¹ MD. Foot & Ankle Orthopaedic Surgeon at Hospital da Luz Lisboa and Hospital Particular do Algarve - Faro
²MBBS, MMed(Ortho), MPH, FRCSEd(Orth) Department of Orthopaedic Surgery National University Hospital, Singapore
³ MD. PhD. Orthopaedic Surgeon at Aleris Tromsø, Norway
⁴MD. Foot and Ankle Unit, iMove Traumatology, Barcelona, and Olympia, Madrid, Spain.Laboratory of Arthroscopic and Surgical Anatomy. Department of Pathology and Experimental Therapeutics (Human Anatomy Unit), University of Barcelona, Barcelona, Spain
⁴MD. PhDc. ankle surgeon at Clinique du Sport, Mérignac, France.

Figure 1: Fig. 1 - AFAS-ESSKA and EFAS faculty: Andrew Hong, João Vide, Paulo Felicissimo, Danielle Marcolli, Mette Andersen, Manfred Thomas, Paolo Ceccarini, Bruno Pereira, Jordi Vega, Guillaume Cordier, from left to right and bottom to top.

In the pursuit of advancing treatments and providing training of excellence for conditions affecting the foot and ankle, European societies have long played a major role in these endeavours. ESSKA Ankle and Foot Associates Section (AFAS-ESSKA) and the European Foot and Ankle Society (EFAS) stand out as pillars of excellence in research and practice in this field. Their recent collaboration marked a significant milestone, setting new standards in joint education and expertise exchange.

The inaugural Sports Medicine Advanced Joint Course, held on February 15th and 16th in Munich, Germany, exemplified the commitment of AFAS-ESSKA and EFAS to push the boundaries of treatment modalities. This groundbreaking event showcased updates and novel techniques across various domains, ranging from small joint arthroscopy to complex ankle reconstructions.

Participants were immersed in a dynamic learning environment, where leading experts shared insights and best practices on osteochondral injuries of the talus, arthroscopy assisted ankle fracture fixation, syndesmotic injuries, Achilles and Peroneal tendon injuries, FHL transfers, as well as medial and lateral ankle ligaments repair and with options for reconstruction all being performed arthroscopically. Close interaction with the faculty and the ratio of one cadaver to two participants made the setting ideal to face the challenges of adopting new advanced techniques in the surgical knowledge of each participant.

Feedback from participants and faculties alike echoed resoundingly positive sentiments, with reported high satisfaction levels. The collaborative nature of the course not only facilitated knowledge exchange but also fostered a sense of camaraderie among attendees. The synergy between AFAS-ESSKA and EFAS was palpable, with each society complementing the other's expertise to deliver a comprehensive educational experience.

Beyond the immediate success of the joint course, this collaboration signifies a paradigm shift in the landscape of foot and ankle treatment. By pooling resources and expertise, AFAS-ESSKA and EFAS have unlocked new possibilities for innovation and advancement. The synergistic fusion of knowledge and techniques has enriched the collective armamentarium of foot and ankle specialists, ultimately benefiting patients in need of specialized care.

As we reflect on the achievements of the past collaboration, we anticipate new opportunities and challenges on the horizon. With each joint endeavor, we inch closer towards realizing our collective vision of excellence in foot and ankle care.

In conclusion, the inaugural Sports Medicine Advanced Joint Course stands as a testament to the power of collaboration and shared expertise. AFAS-ESSKA and EFAS have demonstrated their unwavering commitment to advancing the field, setting a precedent for future endeavors. Stay alert for the next chapter in our collective pursuit of excellence!

Arthroscopic excision of an intra-articular osteoid osteoma on the femoral neck mimicking features of bone marrow edema

Introduction

Osteoid osteoma (OO) is the third most common benign bone-forming tumor, which accounts for 10 to 14% of all benign bone tumors [1]. The most common anatomical location is the diaphysis or metaphysis of the long bones, with lower extremities being more frequently affected [1,2]. Intra-articular location is less common leading to a longest diagnostic delay and frequent misdiagnoses with the initial clinical image that can masquerade inflammatory arthritis [2]. This poor diagnostic accuracy inevitably leads to negative consequences and limits the provided treatment management [2].

We report a case of arthroscopic excision of osteoid osteoma of the femoral neck, which initially managed as bone marrow edema due to diagnostic delay.

Case presentation

A 19-year-old male, university student, was referred to our department with persistent and non-specific groin pain in his right hip that he had for almost a year. The patient reports the insidious onset of initially mild pain but gradually increased in severity. No comorbidities, no trauma or any other relevant history was noted. On clinical examination he walked with an antalgic gait and range of motion was reduced to 90 flexion and no internal or external rotation with intense pain at the FADDIR or FABER test.

The initial radiographic examination, anteroposterior and lateral hip radiographs (Figure 1) did not reveal any relevant abnormality. Blood test were unremarkable. Three consecutive MRI’s within 12-month interval, revealed marked bone marrow edema on the anatomical portion of the femoral neck (Figure 2) and significant joint effusion. The provisional diagnosis was one of transient osteoporosis. The fact that it was in a very usual location and within 12 months no improvement was recorded increased our suspicion for the presence of OO. A computed tomography (CT) was ordered, which revealed the typical nidus and surrounding rim of peripheral reactive sclerotic bone (Figure 3), along the medial cortex of the femoral neck, suggesting the presence of intra-articular OO of the hip.

Arthroscopic excision of the lesion was considered because of the anatomic location of the OO (superficial and medial head-neck junction). Hip arthroscopy was performed under general anesthesia with the patient in supine position. After the initial central compartment assessment, the traction was released and the peripheral compartment was accessed using the PMAP (proximal mid-anterior portal) for the 70 scope and MAP (mid-anterior portal) as a working portal. Significant synovitis was revealed and a prominent mass with high vascularity was seen (Figure 4). The location checked by the Image Intensifier was the area which the CT revealed the lesion. It was removed using a curette and reactive sclerotic rim was removed using motorized burr and then cauterized with radiofrequency (RF). Histological examination of the resection specimen confirmed the presence of OO.

At 2-months follow-up the patient was pain free, had full range of motion, and regained normal gait. A follow-up MRI confirmed the complete regression of the bone edema and much reduced synovitis (Figure 5).

Discussion

Osteoid osteoma is an uncommon but important cause of hip pain [1]. Patients present with constant and progressive pain, which worsen at night and relieved by non-steroidal anti-inflammatory drugs [3]. Clinical examination may reveal limitation of joint motion, limp during gait and muscle weakness or extensive muscle atrophy of the surrounding muscles [4]. Thus, osteoid osteoma may be mistaken for more common causes of synovitis, such as inflammatory arthritis, idiopathic transient osteoporosis, stress fracture of the femoral neck, aseptic osteonecrosis of the femoral head and/or pigmented villonodular synovitis [3,4].

CT is usually the modality of choice not only for proper diagnosis but also for specifying the exact anatomical location of the lesion [1]. Hosalkal et al. [5] found that CT afforded more confident and accurate detection of the nidus of the osteoid osteoma than MRI in children.

According to Wenger et al [6], the detection rate of osteoid osteoma of the hip joint by CT is close to 100%. In their retrospective study, OO was initially misdiagnosed for up to 70% of cases, as a femoral neck stress fracture, femoral acetabular impingement, Legg-Calve-Perthes disease, inflammatory arthritis, or other joint pathology. They Concluded that the utilization of CT is critical for making a timely and accurate diagnosis.

Recently, with the introduction of MRI-perfusion the literature suggests that it is equally successful in identifying OO with the added benefit of minimizing radiation exposure. (7)

Surgical treatment is frequently used with a high efficacy rate, using various methods, such as open surgical resection, drilled resection, or CT-guided percutaneous ablation [4,8-10]. However, in these techniques, care must be taken to avoid damaging the cartilage during the procedure which could have detrimental effects to the joint in the long term [9,11].

Arthroscopic excision in selected cases is a safe and efficient method of the treatment of OO with fast rehabilitation time [11]. Several studies reported a success rate of more than 90%, if the lesion is accessible [8,9,12].

Conclusion

Intra-articular OO has clinical features that can masquerade as any mono-articular inflammatory arthropathy. The clinical presentation may confuse the physician and the lesion may be not recognized in plain radiographs or MRI. If the bone oedema on the MRI is persistent it should raise the suspicion of an OO and a CT or an MRI-perfusion should be ordered. If the location of the OO is intra-articular arthroscopic-assisted resection is an effective technique to direct visualize, biopsy and treat the pathology.

Figure 1: Anteroposterior (A) and lateral (B) radiographs of the right hip.

Figure 2: MRI imaging bone marrow edema of the right femoral neck in three different examinations within 12 months.

Figure 3: Computed tomography imaging in coronal (A) and axial (B) views shows a central osteolytic lesion (nidus) and perinidal sclerosis in the medial area of the femoral neck of the right hip.

Figure 4: Arthroscopic view of the OO lesion (A), intra-operative fluoroscopic image of the lesion, curettage under II (B) and the final result after the arthroscopic excision (C).

Figure 5: 2-month post-operative magnetic resonance imaging shows complete regression of the bone edema.

Authors: Engl M1., Demetz S1., Schaller C2., Indelli PF2,3.

¹ 1Department of Orthopedic Surgery and Traumatology, Hospital of Vipiteno - Sterzing (SABES-ASDAA), Vipiteno-Sterzing, Italy; Teaching Hospital of Paracelsus Medical University
² Department of Orthopedic Surgery and Traumatology, Hospital of Bressanone - Brixen (SABES-ASDAA), Vipiteno-Sterzing, Italy; Teaching Hospital of Paracelsus Medical University
³ 3Department of Orthopaedic Surgery, Stanford University School of Medicine, Stanford University, Stanford, California, USA;

Background and Introduction

A marked increase in Total Knee Replacement (TKR) procedures has been observed over the last decades in the US and Europe, with around 720,000 TKR performed in Europe in 2019 (1). This rising trend of TKR procedures is projected to plateau around 2030 (2).

For example, in France, Le Stum et al. (1) reported the highest increase in the TKR rate (82%, 20.9 to 37.9) in male patients in the age group >64 years for the years 2009 - 2019. The same authors also reported an increased TKR rate in patients with fewer comorbidities. These younger patients, undergoing TKR procedures, have not only a higher functional demand and higher expectations of the outcome but also have a significantly higher risk for revision as shown in a recently published survival analysis of a regional Italian arthroplasty register (6). In this survival analysis, the relative risk of failure was 3.1 higher (CI 95, 2.2 - 4.3) in patients younger than 50 years of age compared to the age group >65 years. Furthermore, patients in the age group 50-65 years of age also showed a 1.8 higher (CI95, 1.6-2 - 2.0) risk of failure. To address these problems, adult reconstruction surgeons must continue to strive for the optimal implant and select the best alignment.

Total knee replacement has undergone significant advancements in design and alignment over the years. The development of medial pivot designs and recently, the philosophy of more personalized alignments combined with enabling technologies, represent a notable stride in improving clinical outcomes.

This article provides a brief overview of the historical progression of the use of medially stabilized total knee designs, highlighting the impact on patient satisfaction and functional outcomes, especially when combined with modern alignment strategies and technological surgical aids.

History of the medial stabilised knee - back to the future?

The first description of the native knee kinematics was given by Giovanni Alfonso Borelli, who showed the medial pivot kinematic and the femoral rollback mechanism in cadaveric specimens back in the late 17th century (7). However, it took almost 300 years until this concept achieved wide acceptance following the publication of Freeman and Pinskerova (8). Thanks to those authors, it has been shown that the tibio-femoral flexion axis translates posteriorly during knee flexion and the tibio-femoral contact remains, at the same time, constant in the medial compartment of the knee.

The first medial stabilized knee design dates back to 1998 and was the Advance Medial Pivot (MicroPort Orthopedics Inc, Arlington, TN). Since then, other orthopaedic companies have developed a medial stabilised knee design. While early knee replacement designs focused on achieving stability and durability, often sacrificing physiological knee motion, the evolution of medially congruent knee designs aimed at addressing these limitations by incorporating more anatomical features. In 2023, it is mandatory to distinguish between pure Medial Pivot (MP) and Medial Congruent (MC) or other forms of Medial Stabilized designs. The pure MP design concept is based on mimicking the natural knee's biomechanics, where the medial condyle serves as a pivot during flexion: this type of implant is usually designed as a “ball in socket” where the medial femoral condyle is defined and designed as the ball and the polyethylene insert, medially ultracongruent with a 1/1 ratio, acts as the socket, whereas the lateral compartment is generally flatter. In contrast to this “pure” concept, the most popular form of MC design (Persona MC, Zimmer Biomet, Warsaw, USA) incorporates a standard femoral component (J-curve) which articulates with a polyethylene insert that is medially more congruent with respect to the lateral side; this medial high-congruence is also increased by the use of a higher anterior lip in the medial compartment, favouring a lateral roll back kinematic during the gait cycle.

All medial pivot/medial congruent/medial stabilized designs aim to restore not only stability but also normal knee kinematics, potentially improving patient satisfaction and function. However, the current literature on the benefits of medial stabilized designs compared to other designs is still inconclusive.

A recent meta-analysis by Kakoulidis et al. (3) published in KSSTA, did not yield any ROM and PROMs statistical differences between PS and medially stabilized groups. In contrast to this study, a systematic review and meta-analysis by Shi (4) showed better WOMAC and HSS scores and a lower complication rate (OR 0.53) in medial pivot cohorts compared to PS while ROM, radiographic results and revision rates showed no differences.

When looking at outcomes, however, adult reconstruction surgeons should also consider alignment philosophies that are currently changing towards more personalized and kinematic strategies. Historically, mechanical alignment has been a dogma over the last decades. With the rise of technological aids, precision for the targeted component placement is dramatically improving. Therefore, the comparison between a mechanical aligned PS knee (historically the gold standard in TKA) and a medially stabilized knee, might not yield the full potential of the second one. A systematic review of the literature comparing gait data following PS and medial pivot primary TKRs, published by Risitano et al. (5) in 2023, confirmed important kinematic and kinetic differences between medial pivot and PS TKA designs; this review also confirmed that both designs kinematic is still quite distant from that one of the native knee.

Clinical Implications

Medial pivot total knee replacement designs in combination with a personalized or kinematically aligned implantation philosophy may show promising results in terms of improved kinematics and patient-reported outcomes. The preservation of natural knee motion may contribute to enhanced functional performance and long-term implant survivorship of medial pivot total knee replacement as shown in a study by Karachilios et al. (9) where an overall survival rate of 97.3% at 15 years was reported. However, challenges and controversies exist, and ongoing research is essential to further validate the clinical benefits.

Conclusion

The evolution of total knee replacement designs has witnessed a paradigm shift towards achieving more natural knee kinematics. The development of medial stabilised total knee replacement designs represents a significant advancement in this pursuit. Scientific literature supports the notion that medial pivot designs may offer improved patient satisfaction and functional outcomes. As research continues to refine and validate these designs, the future of total knee replacement holds the promise of better replicating the intricate biomechanics of the native knee.

References
1. Le Stum, M., Gicquel, T., Dardenne, G., Le Goff-Pronost, M., Stindel, E. and Clavé, A., 2023. Total knee arthroplasty in France: Male-driven rise in procedures in 2009–2019 and projections for 2050. Orthopaedics & Traumatology: Surgery & Research, 109(5), p.103463.
2. Daugberg, L., Jakobsen, T., Nielsen, P.T., Rasmussen, M. and El-Galaly, A., 2021. A projection of primary knee replacement in Denmark from 2020 to 2050. Acta Orthopaedica, 92(4), pp.448-451.
3. Kakoulidis, P., Panagiotidou, S., Profitiliotis, G., Papavasiliou, K., Tsiridis, E. and Topalis, C., 2023. Medial pivot design does not yield superior results compared to posterior-stabilised total knee arthroplasty: a systematic review and meta-analysis of randomised control trials. Knee Surgery, Sports Traumatology, Arthroscopy, 31(9), pp.3684-3700.
4. Shi, W., Jiang, Y., Wang, Y., Zhao, X., Yu, T. and Li, T., 2022. Medial pivot prosthesis has a better functional score and lower complication rate than posterior-stabilized prosthesis: a systematic review and meta-analysis. Journal of Orthopaedic Surgery and Research, 17(1), pp.1-14.
5. Risitano, S., Cacciola, G., Capella, M., Bosco, F., Giustra, F., Fusini, F., Indelli, P.F., Massé, A. and Sabatini, L., 2023. Comparison between gaits after a medial pivot and posterior stabilized primary total knee arthroplasty: a systematic review of the literature. Arthroplasty, 5(1), pp.1-11.
6. Perdisa, F., Bordini, B., Salerno, M., Traina, F., Zaffagnini, S. and Filardo, G., 2023. Total knee arthroplasty (TKA): when do the risks of TKA overcome the benefits? Double risk of failure in patients up to 65 years old. Cartilage, p.19476035231164733.
7. Piolanti, N., Polloni, S., Bonicoli, E., Giuntoli, M., Scaglione, M. and Indelli, P.F., 2018. Giovanni Alfonso Borelli: the precursor of medial pivot concept in knee biomechanics. Joints, 6(03), pp.167-172.
8. Freeman, M.A. and Pinskerova, V., 2005. The movement of the normal tibio-femoral joint. Journal of biomechanics, 38(2), pp.197-208.
9. Karachalios, T., Varitimidis, S., Bargiotas, K., Hantes, M., Roidis, N., amd Malizos, K. N., 2016. An 11-to 15-year clinical outcome study of the Advance Medial Pivot total knee arthroplasty: pivot knee arthroplasty. The Bone & Joint Journal, 98(8), pp. 1050-1055.

In recent years, technological advancements have significantly reshaped the landscape of orthopedic surgery. Innovations in 3D printing and 3D digital CT planning are ushering in a new era of precision, customization and enhanced decision-making capabilities, ultimately improving patient outcomes.

In both anatomic and reverse total shoulder arthroplasty, getting the glenoid component position right is crucial for success. Despite this, there's a 4.6% cumulative revision rate at 5 years, and the top reasons for revisions are instability (38.5%) and loosening (18.0%) [1]. Attaining optimal alignment, inclination, and projection is crucial for maximizing the utilization of the available bone for secure fixation.

The prevalence of shoulder replacement revision, primarily due to glenoid positioning errors, is rising. This trend can be attributed to various factors such as the scapula's flat nature, the lack of a clear reference axis, surgical approaches that expose the glenoid with limited bone landmarks, challenges posed by the humerus and deltoid that impede glenoid access, and the considerable variability in scapula morphology [2].

3D Printing

3D printing, or additive manufacturing, is a revolutionary method for creating three-dimensional objects layer by layer, deviating from traditional subtractive manufacturing processes. This technique employs a diverse range of materials, including plastics, metals, ceramics and biomaterials. The process involves initiating a digital image through various methods such as computer-aided design (CAD), online libraries, 3D scanning or DICOM files derived from CT and MRI scans. The obtained image is then converted into an STL file within modelling software, followed by layer slicing and the generation of G-Code, a file containing instructions for the printer. This G-Code is inserted into the 3D printer, marking the commencement of the printing process [3,4].

The adaptability and transformative nature of 3D printing is not only reshaping manufacturing approaches, but also pushing the boundaries of personalized interventions, patient comfort and preoperative rehabilitation. Beyond personalized manufacturing, the development of 3D bioprinting, artificial intelligence and advanced biomaterials promises to revolutionize precision medicine, offering innovative solutions for tissue engineering, regenerative medicine, and personalized healthcare.

3D Planning

3D virtual planning based on CT scans represents a virtual reconstruction of a 3D anatomical model and it is often used for surgical planning and interventions. This fully manipulable technology helps in the preoperative period, aiding surgeons in choosing the optimal approach and determining the dimensions and type of implants or components, while the software provides both coloured and numeric feedback on the baseplate's position, the extent of bone removal and the prosthetic/bone contact [5].

3D Printed Anatomical Models

The incorporation of 3D-printed anatomical models into preoperative planning offers a multitude of advantages. Firstly, these models are educational tools for less experienced surgeons and serve to familiarize themselves with the patient`s specific anatomy and the surgical steps in a feel-and-see manner. Additionally, the utilization of 3D-printed models has the potential to transform preoperative planning for surgeons who may have limited experience in the field [6].

Secondly, the patient-specific nature of these models is especially beneficial for addressing anatomical variations or complex pathologies. Surgeons can strategize and optimize their approach, tailoring plans to the unique details of each case. This precision contributes to more effective interventions, potentially reducing complications and improving overall surgical outcomes. KC Wang et al. studied the usefulness of bony morphology and model evaluation of CT-Based 3D printed glenoid models before shoulder arthroplasty and proved that the 3D models helped the surgeons to appreciate more clearly the bony morphology as the complexity of the glenoid structure increased [7]. Utilizing the entire scapula as a reference enhances accuracy and reduces the occurrence of glenoid vault perforation. Achieving this level of visualization requires pre-operative 3D CT planning, 3D virtual models or 3D printed anatomical models and the accuracy can be further augmented by using Patient-Specific Instrumentation (PSI). Incorporating automatic software in the pre-operative planning and PSI ensures precise and reproducible positioning and orientation of the glenoid component [8,9,10].

3D Printed Patient-Specific Instrumentation (PSI)/ Patient-specific guides (PSGs)

The advantages of 3D-printed patient-specific instrumentation lie in the enhanced accuracy they provide during surgery. The utilization of 3D printing begins with the generation of patient-specific digital models derived from preoperative imaging data, such as CT scans or MRI scans. This meticulous mapping of the patient's anatomy allows for the creation of personalized instruments that precisely fit the contours of the individual's shoulder joint.

There are 2 types of PSI: moulded and stool guides. In theory, guides formed through moulding should enhance stability by establishing a larger contact area with the glenoid. However, stool guides are preferable due to bone visualization limitations [2].

Several authors proved that the use of 3D-printed PSI can have a superior outcome than standard instrumentation. Gauci et al, performed 17 TSA assessing the accuracy and effectiveness of a 3D-printed PSI in guiding the surgical placement of the glenoid component. The mean error in the accuracy of the entry point was -0.1 mm in the horizontal plane, 0.8 mm in the vertical plane, the mean error in the orientation of the glenoid component was 3.4° for version and 1.8° for inclination [9].

Walch et al, made a quantitative analysis of guide pin positioning on cadaveric scapulae (N=18), the mean error in the 3D orientation of the guide pin was 2.39°, the mean entry point position error was 1.05 mm, the mean inclination angle error was 1.42° and the average error in the version angle was 1.64° [11]. In a study conducted by CSY Yung et al, a multi-centre retrospective analysis of 73 patients who underwent RTSA between 2015 and 2020 revealed a significant advantage in favour of PSI, demonstrating that it leads to substantially longer superior and inferior mean screw lengths compared to conventional instrumentation and during the average 2-year follow-up duration there was no occurrence of glenoid component loosening observed in any of the patients [12].

Jacquot et al, concluded that PSI slightly enhanced the positioning of the central point, particularly for a severely retroverted glenoid, but there was no significant improvement in the orientation of the component compared to the freehand method. In 17 TSA patients, the mean error for the central point was 2.89 mm with the freehand method versus 2.1 mm with the use of a targeting guide, the mean errors for version and inclination were respectively 4.82° and 4.2° with the freehand method, compared to 4.87° and 4.39° with a targeting guide [13]. As MGJ Yam et al highlighted, there is a significant cost disparity between in-house 3D printing (that can go as low as $50) and commercially vendor-created guides, typically manufactured abroad (rising up to $1000-1500 per surgery) [14].

Despite the net improvement in surgical planning, PSI is beneficial in reducing intraoperative radiation, operative time and is also aiding younger or less experienced doctors to operate more difficult cases [2,15,16].

Conclusions

The advancements in 3D printing, 3D planning and patient-specific guides have individually revolutionized the landscape of shoulder arthroplasty. Each method brings its own set of benefits, from precision in surgical planning to real-time intraoperative insights.

With further studies and technological improvements, it will be important to understand how 3D printing and 3D planning could link with other innovative technologies like artificial intelligence, machine learning, and computer-assisted navigation for better patient outcomes. It is at the intersection of these technologies that the true potential for transformative change emerges. It's like upgrading from a regular map to a GPS system—more accurate, personalized, and ultimately leading to better results for everyone involved. This collaboration of technologies marks a new era in shoulder surgery, where innovation meets patient-focused excellence.

References

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2. Gauci MO. Patient-specific guides in orthopedic surgery. Orthop Traumatol Surg Res. 2022 Feb;108(1S):103154. doi: 10.1016/j.otsr.2021.103154. Epub 2021 Nov 24. PMID: 34838754.
3. Levesque JN, Shah A, Ekhtiari S, Yan JR, Thornley P, Williams DS. Three-dimensional printing in orthopaedic surgery: a scoping review. EFORT Open Rev. 2020 Aug 1;5(7):430-441. doi: 10.1302/2058-5241.5.190024. PMID: 32818070.
4. Wixted CM, Peterson JR, Kadakia RJ, Adams SB. Three-dimensional Printing in Orthopaedic Surgery: Current Applications and Future Developments. J Am Acad Orthop Surg Glob Res Rev. 2021 Apr 20;5(4):e20.00230-11. doi: 10.5435/JAAOSGlobal-D-20-00230. PMID: 33877073.
5. Moreschini F, Colasanti GB, Cataldi C, Mannelli L, Mondanelli N, Giannotti S. Pre-Operative CT-Based Planning Integrated With Intra-Operative Navigation in Reverse Shoulder Arthroplasty: Data Acquisition and Analysis Protocol, and Preliminary Results of Navigated Versus Conventional Surgery. Dose Response. 2020 Nov 28;18(4):1559325820970832. doi: 10.1177/1559325820970832. PMID: 35185413.
6. Kang HJ, Kim BS, Kim SM, Kim YM, Kim HN, Park JY, Cho JH, Choi Y. Can Preoperative 3D Printing Change Surgeon's Operative Plan for Distal Tibia Fracture? Biomed Res Int. 2019 Feb 11;2019:7059413. doi: 10.1155/2019/7059413. PMID: 30886862.
7. Wang KC, Jones A, Kambhampati S, Gilotra MN, Liacouras PC, Stuelke S, Shiu B, Leong N, Hasan SA, Siegel EL. CT-Based 3D Printing of the Glenoid Prior to Shoulder Arthroplasty: Bony Morphology and Model Evaluation. J Digit Imaging. 2019 Oct;32(5):816-826. doi: 10.1007/s10278-019-00177-4. PMID: 30820811.
8. Berhouet J, Gulotta LV, Dines DM, Craig E, Warren RF, Choi D, et al. Preoperative planning for accurate glenoid component positioning in reverse shoulder arthroplasty. Orthop Traumatol Surg Res 2017;103:407–13.
9. Gauci MO, Boileau P, Baba M, Chaoui J, Walch G. Patient-specific glenoid guides provide accuracy and reproducibility in total shoulder arthroplasty. Bone Joint J 2016;98-B:1080–5.
10. Moreschini F, Colasanti GB, Cataldi C, Mannelli L, Mondanelli N, Giannotti S. Pre-Operative CT-Based Planning Integrated With Intra-Operative Navigation in Reverse Shoulder Arthroplasty: Data Acquisition and Analysis Protocol, and Preliminary Results of Navigated Versus Conventional Surgery. Dose Response. 2020 Nov 28;18(4):1559325820970832. doi: 10.1177/1559325820970832. PMID: 35185413.
11. Walch G, Vezeridis PS, Boileau P, Deransart P, Chaoui J. Three-dimensional planning and use of patient-specific guides improve glenoid component position: an in vitro study. J Shoulder Elbow Surg. 2015 Feb;24(2):302-9. doi: 10.1016/j.jse.2014.05.029. Epub 2014 Aug 31. PMID: 25183662.
12. Yung CS, Fang C, Fang E, Siu YC, Yee DKH, Wong KK, Poon KC, Leung MMF, Wan J, Lau TW, Leung F. Surgeon-designed patient-specific instrumentation improves glenoid component screw placement for reverse total shoulder arthroplasty in a population with small glenoid dimensions. Int Orthop. 2023 May;47(5):1267-1275. doi: 10.1007/s00264-023-05706-z. Epub 2023 Feb 10. PMID: 36763126.
13. Jacquot A, Gauci MO, Chaoui J, Baba M, Deransart P, Boileau P, Mole D, Walch G. Proper benefit of a three dimensional pre-operative planning software for glenoid component positioning in total shoulder arthroplasty. Int Orthop. 2018 Dec;42(12):2897-2906. doi: 10.1007/s00264-018-4037-1. Epub 2018 Jul 2. PMID: 29968136.
14. Yam MGJ, Chao JYY, Leong C, Tan CH. 3D printed patient specific customised surgical jig for reverse shoulder arthroplasty, a cost effective and accurate solution. J Clin Orthop Trauma. 2021 Jul 17;21:101503. doi: 10.1016/j.jcot.2021.101503. PMID: 34414069.
15. Pérez-Mananes R, Burró JA, Manaute JR, Rodriguez FC, Martín JV. 3D surgical printing cutting guides for open-wedge high tibial osteotomy: do it yourself. J Knee Surg 2016;29:690–5.
16. Farshad M, Betz M, Farshad-Amacker NA, Moser M. Accuracy of patient-specific template-guided vs. free-hand fluoroscopically controlled pedicle screw place- ment in the thoracic and lumbar spine: a randomized cadaveric study. Eur Spine J 2017;26:738–49.

¹3^rd Orthopaedic Department, Hygeia Hospital | Greece
² ESSKA-ESA Board Member

Rotator cuff injuries are a common orthopaedic condition often caused by trauma, repetitive strain, or age-related degeneration. The healing process of tendons is slow and incomplete, resulting in reduced functionality and patient-reported outcomes. Traditional treatments, such as physical therapy and surgery, have limited success, especially for chronic tears or poor tendon quality. In recent years, the focus has shifted towards enhancing the biologics of rotator cuff repair, with the use of bio-inductive scaffolds. In our clinical practice, we utilize a bovine bio-inductive collagen implant called Regeneten, manufactured by Smith & Nephew, Memphis, TN, USA, as a supplementary technique for rotator cuff repairs. This article aims to provide an overview of its use and our experience in clinical practice.

The rationale behind using Regeneten is to promote tendon healing and regeneration by providing a scaffold for progenitor stem cells to migrate on. Derived from highly purified bovine Achilles tendon, it forms a matrix that guides cell growth, enables the formation of new tissue, and promotes integration with the repaired tendon. It should be noted that the collagen implant is not intended to provide immediate structural support after surgery and typically absorbs within 6 months.

Clinical Evidence

Several clinical studies have investigated the safety and efficacy of Regeneten in rotator cuff tears. One notable study by Schegel et al. demonstrated healing rates of 84% and 91% in high and intermediate grade partial-thickness tears, respectively. Patients reported significant improvement in ASES and Constant scores, with a high overall satisfaction rate. Another study by Thon et al. reported successful healing rates at 2 years (96%) when Regeneten was used to augment rotator cuff repairs in large and massive tears. They observed no adverse effects related to the implant. McIntyre et al. reported their results in a larger study involving 170 patients with either partial-thickness or full-thickness tears. Eight patients required reoperation, with two cases attributed to adhesive capsulitis.

Complications and adverse effects

Although Regeneten has shown positive results, there have been some reported complications and adverse effects. Case reports have mentioned stiffness, sometimes due to subacromial bursitis with rice-bodies, associated with the implantation. Yeazell et al. compared the results of augmenting repair with Regeneten to a control group treated only with rotator cuff repair and reported a significant reoperation rate due to stiffness in the implant-augmented group. Long-term follow-up studies are necessary to assess the safety, durability, and functionality of the regenerated tendon. Additionally, cost-effectiveness analyses are needed to determine the economic viability and accessibility of this technology.

Our Clinical Series

In our clinical series, we have used Regeneten in rotator cuff tears either as a standalone implant or as an augmentation to repair. Our series involved 20 patients, 13 males and 7 females, with a mean follow-up of 9.9 months (±5.3 months). Nine patients had medium-sized tears, 4 had large tears, and 7 had massive tears. Different techniques were used for repair, including transosseous, double-row, single-row, and patch implantation. Complete repair was achieved in all patients. (figure 1)

We modified the standard technique by using spinal needles for intraoperative scaffold stabilization after unfolding it. We achieved strong fixation of the scaffold with specific tendon anchors and bone anchors using specific inserters. (figure 2, figure 3)

The patients showed improvement in VAS scores (rest/move/night) improved at the 6- and 12-month follow-up (by 2.7/3.95, 2.7/3.95 and 4.4/5.15, respectively). The mean Constant score, ASES and Oxford score improved at the 6- and 12-month follow-up by 14.2/28.1, 26.7/49.2 and 10.8/16.6, respectively. Eight of the patients had a follow up for more than 6 months but less than 12 months so they did not complete 12 months follow up.

Eleven patients underwent MRI at 6 months postoperatively: 8 showed complete healing (Sugaya I-III), 2 partial healing (Sugaya IV) and 1 no healing (Sugaya V). Four of them had massive tears, 2 large, 5 medium (for the massive tears SII:1, SIII: 2, SV:1, for the large tears SII: 1, SIV: 1 and for the medium tears SI: 1, SII: 2. SIII:1, SIV:1). Needle-arthroscopy was performed on 8 patients for postoperative evaluation at 6 months; Three of them had massive tears, 3 large, 2 medium and only one patient with massive tear had incomplete healing. Adverse effects were reported in one patient. He was reoperated for stiffness and inflammation; no pathogen was detected, and his postoperative course remains uneventful.

Our experience using the bioinductive collagen implant alongside arthroscopic rotator cuff repair has resulted in improved patient-reported outcome measures (PROMs) and reduced VAS pain scores. Additionally, 72.7% of patients who underwent MRI at 6 months postoperatively showed complete healing of the tear, while 12.5% showed incomplete healing.

Benefits

1. Enhanced Healing: it provides a conducive environment for cell proliferation and tissue regeneration, promoting faster and more effective healing of tendon injuries.^8,10 This often translates into quicker recovery times and improved patient outcomes.
2. Potentially Reduced Re-rupture Rates: By supporting the formation of new tissue and integration with the surrounding healthy tendon, it reduces the risk of re-rupture, a common complication in tendon injuries.⁸
3. Minimally Invasive Procedure: Its implantation can be performed using minimally invasive techniques, reducing surgical trauma, resulting in smaller incision and faster recovery times compared to traditional open surgical procedures.
4. Versatile Application: it has shown promising early results in various tendon injuries, including rotator cuff tears^11–14 and patellar tendon injuries.¹⁵ This makes it a potential treatment option where conventional treatments have historically yielded suboptimal outcomes.

Future Implications

Looking forward, the introduction of bio-inductive collagen scaffolds could be a significant advancement in regenerative medicine and tendon repair. Early results are promising in promoting tendon healing and improving patient outcomes and this method can open new possibilities for treating various, previously challenging to manage, tendon injuries. Continued research and clinical trials will provide valuable insights into its long-term safety, efficacy, optimal use, and cost-effectiveness.

Figure 1: Medium size RCT: (A) Preoperative MRI (B) Intraoperative Image (C) Postoperative MRI at 6 months

Figure 2: Modified Technique for the Stabilization of the Implant with Spinal Needles (Red Arrows). Shoulder Arthroscopy, Posterolateral Viewing Portal, Manufacturer’s Unfolding Device (Yellow Arrows). The Scaffold is painted Blue circumferentially.

Figure 3: Intraoperative Image after Implantation with Staples (Red Arrows). Shoulder Arthroscopy, Posterolateral Viewing Portal. The Scaffold is painted Blue circumferentially.

References
1. Galatz LM, Ball CM, Teefey SA, Middleton WD, Yamaguchi K. The outcome and repair integrity of completely arthroscopically repaired large and massive rotator cuff tears. J Bone Joint Surg Am. 2004 Feb;86(2):219–24.
2. Eckers F, Loske S, Ek ET, Müller AM. Current Understanding and New Advances in the Surgical Management of Reparable Rotator Cuff Tears: A Scoping Review. J Clin Med. 2023 Feb;12(5).
3. Neri BR, Chan KW, Kwon YW. Management of massive and irreparable rotator cuff tears. J shoulder Elb Surg. 2009;18(5):808–18.
4. Avanzi P, Giudici LD, Capone A, Cardoni G, Lunardi G, Foti G, et al. Prospective randomized controlled trial for patch augmentation in rotator cuff repair: 24-month outcomes. J shoulder Elb Surg. 2019 Oct;28(10):1918–27.
5. Chalmers PN, Tashjian RZ. Patch Augmentation in Rotator Cuff Repair. Curr Rev Musculoskelet Med. 2020 Oct;13(5):561–71.
6. Denard PJ, Burkhart SS. Techniques for managing poor quality tissue and bone during arthroscopic rotator cuff repair. Arthrosc J Arthrosc Relat Surg Off Publ Arthrosc Assoc North Am Int Arthrosc Assoc. 2011 Oct;27(10):1409–21.
7. McCormack RA, Shreve M, Strauss EJ. Biologic augmentation in rotator cuff repair--should we do it, who should get it, and has it worked? Bull Hosp Jt Dis. 2014;72(1):89–96.
8. Bokor DJ, Sonnabend D, Deady L, Cass B, Young A, Van Kampen C, et al. Evidence of healing of partial-thickness rotator cuff tears following arthroscopic augmentation with a collagen implant: a 2-year MRI follow-up. Muscles Ligaments Tendons J. 2016;6(1):16–25.
9. Schlegel TF, Abrams JS, Angelo RL, Getelman MH, Ho CP, Bushnell BD. Isolated bioinductive repair of partial-thickness rotator cuff tears using a resorbable bovine collagen implant: two-year radiologic and clinical outcomes from a prospective multicenter study. J shoulder Elb Surg. 2021 Aug;30(8):1938–48.
10. Schlegel TF, Abrams JS, Bushnell BD, Brock JL, Ho CP. Radiologic and clinical evaluation of a bioabsorbable collagen implant to treat partial-thickness tears: a prospective multicenter study. J shoulder Elb Surg. 2018 Feb;27(2):242–51.
11. Berthold DP, Garvin P, Mancini MR, Uyeki CL, LeVasseur MR, Mazzocca AD, et al. Arthroscopic rotator cuff repair with biologically enhanced patch augmentation. Oper Orthop Traumatol. 2022 Feb;34(1):4–12.
12. Thon SG, O’Malley L 2nd, O’Brien MJ, Savoie FH 3rd. Evaluation of Healing Rates and Safety With a Bioinductive Collagen Patch for Large and Massive Rotator Cuff Tears: 2-Year Safety and Clinical Outcomes. Am J Sports Med. 2019 Jul;47(8):1901–8.
13. McIntyre LF, Bishai SK, Brown PB 3rd, Bushnell BD, Trenhaile SW. Patient-Reported Outcomes After Use of a Bioabsorbable Collagen Implant to Treat Partial and Full-Thickness Rotator Cuff Tears. Arthrosc J Arthrosc Relat Surg Off Publ Arthrosc Assoc North Am Int Arthrosc Assoc. 2019 Aug;35(8):2262–71.
14. Bushnell BD, Connor PM, Harris HW, Ho CP, Trenhaile SW, Abrams JS. Retear rates and clinical outcomes at 1 year after repair of full-thickness rotator cuff tears augmented with a bioinductive collagen implant: a prospective multicenter study. JSES Int. 2021 Mar;5(2):228–37.
15. Looney AM, Fortier LM, Leider JD, Bryant BJ. Bioinductive Collagen Implant Augmentation for the Repair of Chronic Lower Extremity Tendinopathies: A Report of Two Cases. Vol. 13, Cureus. United States; 2021. p. e15567.
16. Yeazell S, Lutz A, Bohon H, Shanley E, Thigpen CA, Kissenberth MJ, et al. Increased stiffness and reoperation rate in partial rotator cuff repairs treated with a bovine patch: a propensity-matched trial. J shoulder Elb Surg. 2022 Jun;31(6S):S131–5.
17. Barad SJ. Severe subacromial-subdeltoid inflammation with rice bodies associated with implantation of a bio-inductive collagen scaffold after rotator cuff repair. J shoulder Elb Surg. 2019 Jun;28(6):e190–2.
18. Root KT, Wright JO, Mandato N, Stewart BD, Moser MW. Subacromial-Subdeltoid Bursitis With Rice Bodies After Rotator Cuff Repair With a Collagen Scaffold Implant: A Case Report. JBJS case Connect. 2023 Jan;13(1).

¹ Department of Orthopaedic Surgery, Centro Hospitalar De Vila nova de Gaia/Espinho, Porto, Portugal
² Department of Orthopaedic Surgery, Clínica Espregueira – Fifa center of excellence, Porto, Portugal

Introduction

Non-traumatic osteonecrosis of the femoral head (ONFH)¹ is characterized by the death of the bone following a disruption of the femoral head blood flow. Initially, osteonecrosis was described as a late complication of traumatic hip injuries. Later, during the 20^th century, it was associated with several risk factors, such as diving, hemoglobinopathies, corticosteroid use, radiation, and alcohol abuse. We will only explore the non-traumatic osteonecrosis of the femoral head (ONFH).

ONFH is responsible for 10% of total hip arthroplasties (THA) in the United States of America². It affects mainly young adults with an average age at treatment of 33 to 38 years old³. Its incidence increased in the early 2000s⁴ due to two factors: the availability of Magnetic Resonance Imaging (MRI), which detects early stages, and an increase in patients treated with corticosteroids.

ONFH diagnosis and stratification are mandatory. Overall, femoral head collapse may be expected in up to 80% of the hips if no treatment is provided⁵. However, inside this big group of ONFH there are the small lesions that seldom progress and larger lesions, which have a poor prognosis, even if surgically treated.

After stratification, appropriate treatment should be provided. In this work, we will consider only the precollapse stage treatment, especially core decompression and its augmented variants.

Pathophysiology

Alcohol abuse and use of corticosteroids are responsible for up to 80% of non-traumatic ONFH⁶, however, its pathophysiology is not completely understood.

They are believed to cause an intra-osseous compartment syndrome: the hyperplasia of the bone marrow fat cell creates intra-osseous hypertension which results in an impartment of the blood flow. There is bone marrow necrosis and osteocytic death. Until this point the lesion is reversible. After the necrotic phase, the reparative process starts with the deposition of fibrovascular tissue around the dead bone and saponification of the necrotic marrow. At this point, there is a definitive ONFH ^1,7. At this stage the cancellous bone loses its mechanical properties and stress fractures arise, eventually leading to collapse.

The steroids are not only responsible for deregulation of the lipid metabolism, but they also decrease osteogenesis potential and blood supply and induce apoptosis⁸. In a similar fashion, alcohol abuse is also credited with deregulation of mesenchymal differentiation towards osteoblastic cells, however, current literature does not explain why only some patients develop ONFH⁹. A genetic predisposition may be an answer and a mutation to type II collagen gene has already been described¹⁰.

The progression between early necrosis and irreversible scared osteonecrosis is a critical step and is determined by the inability to produce adequate fibrinolysis and angiogenesis capable of restoring the normal blood flow¹¹. Is at this critical stage that core decompression may help change the course of the disease.

Classification

The diagnosis is easily made today with MRI and radiographs. MRI is the most sensible exam, with up to 100% of sensitivity. Radiographs are only positive when there is already some bone remodeling in place: sclerosis, osteoporosis, or osteolysis are early signs. Subcondral fractures are the continuation of the pathogenic spectrum and may be better diagnosed by Computer Tomography. Depression and overly collapse are clear in the radiographs¹² as a crescent sign¹³. If MRI is not available or is contraindicated SPECT/CT has proven to be a suitable alternative¹⁴.

As mentinoned, ONFH must be classified according to the stage of the disease and, the dimensions and location of the lesion.

Ficat, Steinberg, and Japanese Orthopaedic Association systems have historically been used. The Association Research Circulation Osseus (ARCO) classification system was created by merging the previous systems and tried to create a universal system that facilitates scientific discussion⁷. Stage I and II are preccolapse stages. At stage I only MRI is positive while at Stage II there are already subtle radiographic signs. On post-collapse stages, ARCO system focused on the head depression cut-off of 2mm because of its proven implications on survival after joint salvage surgery (bone graft, osteotomy): Stage IIIA lesions present a subchondral fracture < 2mm and have a better prognosis than IIIB lesions which have a head depression greater than 2 mm^7,15. Stage IV lesions are characterized by manifest osteoarthritis.

Steinberg and Kerboul classifications were classically used to classify the size of the lesion in the radiograph. Japanese Investigation Committee (JIC) system characterized the lesion by its size in midcoronal MRI image. Ha et al. modified the Kerboul measurement by adapting it to MR images: therefore, the size of the lesion is measured in midsagittal and midcoronal images. If the combined angle is less than 140º it is a small lesion. Large lesions are classified by a necrotic angle superior to 240º¹⁶. It also has prognostic value as small lesions did not progress in the initial study. Recently, Ruckli et all. showed that volumetric and surface measurements on MRI are better correlated with ARCO classification and prognosis: the amount of necrosis is actually bigger in later stages of the disease, pointing out that a significant articular change has occurred¹⁷.

Core decompression

If we consider the intra-osseous compartment syndrome theory, it is sound reasoning to decompress the bone marrow as in any other compartment syndrome. This has been the principle behind core decompression for 50 years, during which it has shown superior results compared to conservative treatment^18,19, with survival rates from 54,5 to 100%¹². A systematic revision has concluded it should be performed at precollapse stages, ARCO I and II on smaller lesions. It may also be considered for short-term symptomatic relief in Stage III²⁰.

Most patients present at stage II and at this point there is already definitive scar tissue around the necrotic area and decompression alone does not remove or clear all the debris. In an attempt to change local biology, different strategies have been pursued: augmentation of the decompression with bone grafts²¹; small-diameter drilling with supplementation with bone Marrow Aspirated Concentrate (BMAC)^22,23 or platelet-rich plasma (PRPs)^24,25; reverse reaming with grafting and BMAC²⁶. In fact, recent studies have proved the superiority of augmentation with BMAC versus CD alone ^27,28.

However, even with augmentation of CD, large-diameter lesions continue to have a poor prognosis and the size of the lesion continues to be the major predictor of collapse²⁹: Boontanapibul et all²² showed that a modified Kerboul angle >250º is associated with progression and collapse even if CD augmented with BMAC is performed.

Another factor that must be considered is the etiology behind ONFH. In the case of steroid induced-ONFH, it must be assessed If the patient continues the therapy. Corticosteroids alter the activity of mesenchymal cells and therefore there might not be a benefit of augmenting CD with autologous BMAC²⁸.

Our center experience is similar to published results. Between 2015 and 2021 we performed CD alone or augmented with PRPs in 41 hips – Figure 1-4. The mean age was 45 years. 6 hips presented at ARCO stage 1, 31 at stage 2, and 4 at stage IIIA. At a minimum follow-up of 2 years, we found progression to THA in 38% of the hips in the precollapse stage. All the hips initially at stage IIIA progressed to THA – Figure 5-7. We did not find a difference between CD alone or augmentation with PRPs. A higher combined necrotic angle was also associated with higher progression to collapse: from the 17 hips with a modified Kerboul angle >250º, 12 progressed to collapse.

Figure 1: A 46-year-old male presents with left hip pain. MRI presents bilateral ONFH. The left hip had a small lesion with a modified Kerboul angle of 154º.

Figure 2: We performed core decompression augmented with PRPs.

Figure 3: 1 year pos-operatively MRI shows absence of progression of the lesion.

Figure 4: Two years pos-op radiograph shows absence of collapse.

Figure 5: A 40-year-old male patient presents with right hip pain. The radiograph shows subtle sclerotic changes – ARCO Stage II.

Figure 6: MRI control at 6 months post-operatively. There is no regression in the size of the lesion and joint effusion is present.

Figure 7: The patient kept pain in his right hip. Loss of sphericity is already present and a total hip arthroplasty was performed.

Further research

When reviewing the literature, two questions arise: do we really need to decompress the small lesions? Do they progress? There is no definitive answer as no large study can be conducted at the expense of those patients who might have benefited from CD and ended up with a hip prosthesis³⁰.

Regarding large lesions, what is the best treatment? Should we be more aggressive and openly debride those hips and grafts?

Further research must clearly stratify the patients in order for proper metanalysis to be performed: what are the patient-specific risk factors? Is the patient still on steroids? What is the ARCO grade of the lesion and what is its size according to the modified Kerboul angle¹⁶ or to the volumetric and surface area¹⁷?

The advance of tissue engineering will also add another factor to the equation as new biomaterials and techniques are discovered. Maybe the solution for the treatment of large lesions rests in the perfect mechanical and biological scaffold³¹.

¹ Thessaloniki Minimally Invasive Surgery (The-MIS) Orthopaedic Center, St. Luke’s Hospital, Thessaloniki, Greece
² School of Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Greece
³ Department of Orthopaedic Surgery, Sports Trauma Unit, St. Luke's Hospital, Thessaloniki, Greece
⁴ Orthopaedic Surgery and Sports Medicine Department, FIFA Medical Center of Excellence, Croix-Rousse Hospital, Lyon, France
⁵ Orthopaedic Department, University Hospital of Larisa, Larisa, Greece
⁶ Department of Orthopaedic Surgery and Traumatology, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium
⁷ 2nd Orthopaedic Department, General Hospital "G. Gennimatas", Aristotle University of Thessaloniki, Thessaloniki, Greece

Introduction

Mesenchymal stem cells (MSCs) have evolved to be a promising technique for the management of knee osteoarthritis (OA) as they have high plasticity, self-renewal capabilities, and immune-suppressive and anti-inflammatory properties (figure 1)¹. However, the recent popularity gain of cell therapies is not without its toll, as we can observe a considerable overflow of contradicting or unclear information or even misinformation about them.

MSCs can be administered either as injectables or surgically (i.e. transplant). The intra-articular injection is most commonly applied as it is a relatively easy and safe procedure that could also be used in ambulatory care. Nevertheless, this technique could not guarantee the proper administration of the cells in the area of interest. Conversely, MSCs surgical implantation is more invasive but overpasses this limitation and ensures the accurate deposit of the cells in the target territory.

The origin of MSCs can vary, but the two most common types of MSCs used for knee OA are bone marrow derived stem cells (BMSCs) (or bone marrow aspirate concentrate, BMAC) and adipose derived stem cells (ADSCs) (or adipose-derived stromal vascular fraction, AD-SVF). SVF is a heterogeneous product that contains ADSCs, macrophages, blood cells, pericytes, fibroblasts, endothelial cells, and their progenitors².

Some of the acknowledged SVF actions can be attributed to the viable MSCs found in the SVF, while others could be associated with the paracrine effect of the cells that are present in SVF³. Bone marrow aspirate is usually obtained percutaneously from the iliac crest in a safe and minimally invasive technique. BMAC contains MSCs high concentrations of IL1-Ra and other anti inflammatory growth factors^4,5.

Many cell therapies for knee OA are available at point-of-care and are easily delivered due to their autologous nature and minimal manipulation required. Notably, the application of MSCs has consistently been shown to be safe, while they do not preclude additional future therapy in case of treatment failure. These treatments seem to be effective in pain reduction and functional improvement, but little is known about their effect on cartilage regeneration and disease modification in clinical practice.

The present article aims to provide an evidence-based overview of the current role, strengths, and limitations of cell therapies for knee OA.

Figure 1: Schematic representation of an osteoarthritic environment and the cellular responses in the joint (A). Mesenchymal stem cells (MSCs) have a high regenerative capacity according to pre-clinical data (B).

MSCs injection for the treatment of knee OA

Τhe most common way of MSCs administration is intra-articular injections. MSCs have been used in one-step or two-step procedures, where the MSCs can be isolated and expanded before their application. Most clinical protocols recommend that a number of MSCs between 10 to 40 x 10⁶ per intra-articular injection tends to demonstrate superior outcomes⁶. The BMAC is an FDA-approved method of obtaining progenitor cells and growth factors for intra-articular use in treating knee OA. BMAC is obtained through density gradient centrifugation to remove blood cells, granulocytes, immature myeloid precursors, and platelets (figure 2)⁷.

Stromal vascular fraction (SVF) and adipose-derived MSCs (AD-MSCs) contain up to 500 times more MSCs than bone marrow⁶. Adipose tissue is harvested by a minimally invasive procedure, which is painless, safe, and cosmetic. Advantages of AD-MSCs and SVF include the ease of harvesting procedure under local anesthesia and the greater tolerance to ischemia and hypoxia associated with the cell’s survival when implanted into the lesion site⁸. SVF contains a more heterogenous cellular population and secretes several cytokines and growth factors, which can further modulate inflammation and immune responses via paracrine signaling (figure 3)⁹.

The current literature shows encouraging results for the intra-articular injections of both BMAC and SVF regarding pain reduction and improvement of functional outcomes and overall quality of life^6,9. Initially, most of the relevant articles were non-randomized studies or case series. However, a recently published systematic review summarized five level 1 studies and demonstrated superior PROMs at 6 and 12 months for AD-MSCs and SVF compared to placebo and hyaluronic acid injections⁶. It remains unclear whether BMAC is superior to SVF/AD-MSCs injections. Both BMAC and SVF single intra-articular injections in patients with knee OA have been associated with symptomatic improvement. A recent systematic review and meta-analysis showed that SVF injection was more effective than BMAC injection in terms of pain relief at short-term follow-up⁹.

The literature is vague concerning cartilage regeneration assessed with MRI following MSCs injection with other studies showing improvement in cartilage signal and morphology, while others found no improvement. In a recent relevant systematic review, only 3 studies yielded improved post-injection cartilage status whereas 2 did not observe any changes in the MRI after intra-articular injections of AD-MSCs or SVF⁶. The ESSKA Orthobiologic initiative performed a systematic review to investigate in pre-clinical studies the disease-modifying effects of AD-MSCs injectable therapies in joints affected by OA. Overall, 94.1% of the included studies reported better results with adipose-derived products than controls¹⁰.

Figure 2:Bone marrow aspirate concentrate (BMAC) preparation for intra-articular injection.

Figure 3: Stromal vascular fraction (SVF – red arrow) is occasionally combined with platelet rich plasma (PRP – white arrow) for intra-articular injection.

MSCs implantation for the treatment of knee OA

Nowadays, two are the leading sources for MSCs implantation, either autologous AD-MSCs or allogenic from the umbilical cord (hUCB-MSCs). Adipose tissue is harvested with simple liposuction from the patient's abdominal or gluteal regions before implantation. On the other hand, hUCB-MSCs are obtained from the maternal umbilical veins and arteries at the time of delivery or from the placental tissue. The culture expansion of both sources may enforce their effect as more cells are applied. The MSCs are often embedded or mixed with three-dimensional scaffolds substances, including hyaluronic acid, collagen, or fibrin glue.

Recent studies demonstrated promising results using patient-reported outcomes measures (PROMs), radiological evaluation, or second-look arthroscopy. Kim et al. evaluated the midterm clinical results and survival rate in a large case series of 467 patients treated with AD-MSCs implantation on a fibrin glue scaffold for knee OA with a minimum 5-year follow-up. The study showed encouraging functional outcomes with an acceptable duration of symptom relief and a survival rate of 99.8% and 74.5% at 5 and 9 years, respectively, in terms of conversion to high tibial osteotomy or knee arthroplasty¹¹. In another study, Song et al.¹² published a large case series, including 128 patients with Kellgren-Lawrence (KL) grade 1 to 3 knee osteoarthritis who underwent hUCB-MSCs implantation combined with a hyaluronic acid (HA) hydrogel, evaluated with a follow-up lasting at least two years. The authors concluded that implantation of UCB-MSC-HA significantly improves pain and function, with no adverse effects or post-operative complications to be noted. Radiological evaluation was also performed using the modified MOCART score at 3-6 months and one year after surgery, demonstrating increased values (30.58 for the first MRI and 55.44 for the second).

It should be noted that a crucial point in managing an osteoarthritic knee is prioritizing the treatment. The approach should start by assessing the limb alignment, afterward, joint stability, and next considering any meniscal and cartilage procedures. In this regard, MSCs administration is often combined with a high tibial osteotomy (HTO) when a substantial varus is present. Indeed, a recent study performed by Yang et al. demonstrated the effectiveness of this combined surgery. Namely, 176 patients who underwent HTO combined with BMAC or hUCB-MSC procedure for medial compartment osteoarthritis were followed for a minimum of 2 years. Clinical outcomes were evaluated using different PROMs (IKDC, KOOS, SF-36, Tegner) and revealed a significant improvement in both groups with no differences between the two groups. However, a second-look arthroscopy showed better cartilage healing in the hUCB-MSC group¹³.

Discussion

Until recently, literature was scarce regarding the outcomes of MSCs application in patients with arthritic knees. However, high-level studies have reported clinical improvement after injection or implantation of MSCs. Most published data agree that clinical improvement is achieved with pain relief and functional improvement for at least 1 year⁶. Although short-term promising outcomes are widely demonstrated, the presentation of midterm and long-term outcomes is lacking. Only a few studies have revealed the midterm clinical effectiveness of AD-MSCs with suppression of radiological deterioration of degenerative changes for 3 to 5 years¹⁴. Noteworthy, clinical amelioration has been shown after MSCs administration compared with hyaluronic acid or placebo injections, without distinct superiority between adipose-derived products and BMAC.

However, many issues should be solved to achieve a consensus regarding the optimal utilization of MSCs. The proper cell dosage has still to be defined, as there is high heterogeneity in the literature about the optimal cell dosage. High-dosage AD-MSCs seem to be more advantageous in terms of longevity¹⁵. Moreover, the number of doses (single or multiple) remains under investigation.

A particular limitation is that only short-term and mid-term outcomes are available, and the main investigated effect is restricted in evaluating pain relief and functional improvement. Few studies evaluate the impact on cartilage repair through MRI or second-look arthroscopy showing encouraging and promising results in the midterm follow-up period.

Another limitation is the relatively high cost. Osteoarthritis and especially knee arthritis has been reported to constitute a significant economic burden with high direct and indirect expenditures. Unfortunately, the exact cost of MSCs application has not been investigated or reported, while significant variations in costs exist among different countries. No international catalog including the exact costs is available nor reliable cost-effectiveness studies have been published.

As for safety, literature is relatively consistent on this topic with minimal reported side effects and without remarkable difference in knee pain or swelling compared to other treatments, and without tumorigenic effect⁹. Infection that could result in septic arthritis remains extremely rare when the procedure is performed under strict aseptic conditions. Another important issue is that MSCs application does not “burn bridges” since their utilization does not compromise the result of further interventions in the future.

Further high-level studies are necessary to evaluate the efficacy of MSCs, especially in terms of disease modification effects and cost-effectiveness compared to other less expensive orthobiologics. Future perspectives should focus on establishing a wide-accepted protocol for MSCs administration, including all parameters that are still controversial, such as dosage of cells, preparation and injection protocol, and post-injection instructions and rehabilitation.

Key takeaways

• MSCs are increasingly used for the treatment of knee OA, either as an intra-articular injection (most common) or surgical implantation into the lesion along with a scaffold.
• They are efficient in short-term pain, function, and quality of life improvement.
• Limited data exist about MSCs' effect on cartilage status, which shows controversial findings for injectable treatments and short-term improvement of cartilage volume and quality following MSCs implantation.
• Proper indications are unclear, with available studies reporting on patients suffering from mild to severe (KL grade 1 to 4) knee OA.
• Strengths: minimally invasive, autologous, safe, high regenerative capacity in pre-clinical studies.
• Limitations: few RCTs available, high heterogeneity among studies, lack of long-term data, cost-effectiveness still needs to be established.
• Controversial issues: optimal MSCs source, preparation and administration, cell dosage, injections recipe, post-injection protocol.

References
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9. Bolia IK, Bougioukli S, Hill WJ, et al. Clinical Efficacy of Bone Marrow Aspirate Concentrate Versus Stromal Vascular Fraction Injection in Patients With Knee Osteoarthritis: A Systematic Review and Meta-analysis. Am J Sports Med 2022;50:1451-61.
10. Perucca Orfei C, Boffa A, Sourugeon Y, et al. Cell-based therapies have disease-modifying effects on osteoarthritis in animal models. A systematic review by the ESSKA Orthobiologic Initiative. Part 1: adipose tissue-derived cell-based injectable therapies. Knee Surg Sports Traumatol Arthrosc 2023;31:641-55.
11. Kim YS, Suh DS, Tak DH, Chung PK, Koh YG. Mesenchymal Stem Cell Implantation in Knee Osteoarthritis: Midterm Outcomes and Survival Analysis in 467 Patients. Orthop J Sports Med 2020;8:2325967120969189.
12. Song JS, Hong KT, Kim NM, et al. Implantation of allogenic umbilical cord blood-derived mesenchymal stem cells improves knee osteoarthritis outcomes: Two-year follow-up. Regen Ther 2020;14:32-9.
13. Yang HY, Song EK, Kang SJ, Kwak WK, Kang JK, Seon JK. Allogenic umbilical cord blood-derived mesenchymal stromal cell implantation was superior to bone marrow aspirate concentrate augmentation for cartilage regeneration despite similar clinical outcomes. Knee Surg Sports Traumatol Arthrosc 2022;30:208-18.
14. Kim KI, Lee WS, Kim JH, Bae JK, Jin W. Safety and Efficacy of the Intra-articular Injection of Mesenchymal Stem Cells for the Treatment of Osteoarthritic Knee: A 5-Year Follow-up Study. Stem Cells Transl Med 2022;11:586-96.
15. Ding W, Xu YQ, Zhang Y, et al. Efficacy and Safety of Intra-Articular Cell-Based Therapy for Osteoarthritis: Systematic Review and Network Meta-Analysis. Cartilage 2021;13:104S-15S.

¹ Department of Orthopaedic Surgery, Centro Hospitalar De Vila nova de Gaia/Espinho, Porto, Portugal
² Department of Orthopaedic Surgery, Clínica Espregueira Fifa center of excellence, Porto, Portugal

Trochanteric overgrowth is a common sequela in Legg-Calvé-Perthes disease, and it is caused by a premature closure of the capital femoral physis while sparing the greater trochanteric physis[1]. This deformity can be explained by the 3 physeal zones of the proximal femur[2]. The functional consequences of the relative overgrowth of the greater trochanter include a decrease tension and mechanical efficiency of the abductor muscles; the greater trochanter moves closer to the center of rotation of the hip, decreasing the resting length and lever arm of the hip abductor muscles, and impairing muscular stabilization of the hip; the muscle force vector becomes more vertical increasing the pressure force over a diminished area of hip joint surface; and an extra-articular impingement of the trochanter on the acetabular rim during abduction decreasing the range of motion[3]–[6]. Clinically, the patients present with a trendelenburg gait and a positive trendlenburg sign, gluteus medius lurch, and fatigue pain on walking[7]. The examination may reveal limited and painful active or passive hip abduction and extension[8]. Macnicol and Makris described a “gear-stick” sign which is based on the observation that hip abduction is limited by impingement of the greater trochanter on the ilium when the hip is extended but full abduction is possible when the hip is fully flexed[9].

Several surgical interventions for a high-standing greater trochanter have been suggested and they all have the same target: improve the hip biomechanics. Trochanteric epiphysiodesis is effective only in younger patients as a prophylactic measure in the active stage of the disease[3], [4], [10]. Distal and lateral advancement of the trochanter was first described by Jani (1969) and has been advocated for the late treatment of Legg-Calvé-Perthes disease improving gluteal efficiency and increasing the range of abduction[5], [6], [11]–[15].

We retrospectively reviewed all patients who underwent trochanteric osteotomy for a high-standing greater trochanter between April 2013 and February 2019 in our institution. There were 7 patients, 5 males and 2 females; 4 of the hips were left and 3 were right. The mean age of patients was 32 years (range: 21-42). The patients had no previous surgery. All patients were available for complete follow-up evaluation. The minimum follow-up period was 12 months (median, 17 months; range 12–36 months) for the entire group. The same surgeon performed a stepped osteotomy as described by Johannes et al. in all patients[16]. The patient was positioned in the lateral decubitus position and a straight direct lateral 18- to 23-cm incision centered on the greater trochanter was made with one-third of the incision extended proximal to the tip of the greater trochanter. The iliotibial band was split longitudinally, proximally following the anterior border of the gluteus maximus muscle and then the interval between the gluteus maximus and the gluteus medius was developed. The posterior origin of the vastus lateralis fascia was released and the muscle lifted from the bone epiperiosteally, leaving the tendinous origin from the tubercle intact. A stepped osteotomy of the trochanter was performed, starting at the posteriosuperior tip of the greater trochanter and ending distally 15 mm distal to the lateralis tubercule (Fig. 1). The fragment was subsequently advanced and fixed with two 3.5-mm cortical screws (Fig. 2). This technique allows us to maintain the majority of the gluteus medius tendon on the fragment and provides more stability. The patients remain with progressive partial weightbearing for the first 6 weeks after the surgery. Active abduction and passive adduction were prohibited until any signs of consolidation, usually at 6-8 weeks.

Figure 1: Intraoperative view shows completion of the osteotomy. The osteotomy is fully visualized with the gluteus medius and minimus muscles and vastus lateralis muscle attached to the trochanteric fragment.

Figure 2: Schematic view show the reduction of the trochanteric fragment after a stepped trochanteric osteotomy.

All the osteotomies healed with no signs of malunion, like proximal migration of the fragment. We have one case of delayed union (70 days). The hardware was removed in 6 patients after a median of 7 months. No patients had perioperative complication and no revision surgery was necessary. Four patients were completely pain-free, furthermore all patients decreased pain intensity (median of 5 points decrease in Likert scale). Limp was eliminated or gait was considerably improved in 5 of 7 patients. The Hip Disability and Osteoarthritis Outcome Score improved in all patients (median 46 points, range 31-55 points). Biomechanical measurements with good-quality x-rays found a significant improvement in the joint reactive force ranging from -14 to 17%.

Figure 3: A pre and postoperative radiographic anteroposterior view show the anatomic reduction and fixation of the trochanteric fragment after a stepped trochanteric osteotomy.

Our results compared favourably with those found in the literature [17]–[23]. Distal transfer of the greater trochanter provides good outcomes, improving the clinical, functional and radiologic scores. A variety of surgical techniques for greater trochanteric transfer have been described in the literature. The stepped osteotomy used by the surgeon and described by Johannes et al. is more demanding than a flat cut, however, does have technical advantages: reduction of the fragment is easier; the proximal limb can be more shallow, permitting one to stay out of the trochanteric fossa in cases in which the tip of the trochanter is unusually hooked or small; the step provides more stability, the fragment does not rotate or migrates proximally when held for screw placement.

This technique does not allow the treatment of intra-articular lesions, so the selection criteria must be precise and sometimes a surgical hip dislocation need to be combined.

More studies with a greater number of patients are necessary to prove the value of the trochanteric osteotomy in the treatment of the Legg-Calve-Perthes sequelae.

Biography
1. J. Robichon, J. P. Desjardins, M. Koch, e C. E. Hooper, «The femoral neck in Legg-Perthes’ disease. Its relationship to epiphysial change and its importance in early prognosis», J Bone Joint Surg Br, vol. 56, n.o 1, pp. 62–68, fev. 1974.
2. R. S. Siffert, «Patterns of deformity of the developing hip», Clin Orthop Relat Res, n.o 160, pp. 14–29, out. 1981.
3. D. Schneidmueller, C. Carstens, e M. Thomsen, «Surgical treatment of overgrowth of the greater trochanter in children and adolescents», J Pediatr Orthop, vol. 26, n.o 4, pp. 486–490, 2006, doi: 10.1097/01.bpo.0000226281.01202.94.
4. P. M. Stevens e S. S. Coleman, «Coxa breva: its pathogenesis and a rationale for its management», J Pediatr Orthop, vol. 5, n.o 5, pp. 515–521, 1985.
5. A. S. Kelikian, M. O. Tachdjian, M. J. Askew, e M. Jasty, «Greater trochanteric advancement of the proximal femur: a clinical and biomechanical study», Hip, pp. 77–105, 1983.
6. H. Wagner, «Femoral Osteotomies For Congenital Hip Dislocation», em Acetabular Dysplasia, U. H. Weil, Ed., em Progress in Orthopaedic Surgery. Berlin, Heidelberg: Springer, 1978, pp. 85–105. doi: 10.1007/978-3-642-66737-4_4.
7. S. Y. Joo, K. S. Lee, I. H. Koh, H. W. Park, e H. W. Kim, «Trochanteric Advancement in Patients with Legg-Calvé-Perthes Disease Does Not Improve Pain or Limp», Clin Orthop Relat Res, vol. 466, n.o 4, pp. 927–934, abr. 2008, doi: 10.1007/s11999-008-0128-4.
8. S. W. Cheatham, «Extra-articular hip impingement: a narrative review of the literature», J Can Chiropr Assoc, vol. 60, n.o 1, pp. 47–56, mar. 2016.
9. M. F. Macnicol e D. Makris, «Distal transfer of the greater trochanter», J Bone Joint Surg Br, vol. 73, n.o 5, pp. 838–841, set. 1991, doi: 10.1302/0301-620X.73B5.1894678.
10. A. Van Tongel e G. Fabry, «Epiphysiodesis of the greater trochanter in Legg-Calvé-Perthes disease: The importance of timing», Acta Orthop Belg, vol. 72, n.o 3, pp. 309–313, jun. 2006.
11. L. Jani, «Die Entwicklung des Schenkelhalses nach der Trochanterversetzung», Arch orthop Unfall-Chir, vol. 66, n.o 2, pp. 127–132, 1969, doi: 10.1007/BF00417245.
12. J. Cohen, «Congenital dislocation of the hip. Case report of an unusual complication and unusual treatment», J Bone Joint Surg Am, vol. 53, n.o 5, pp. 1007–1011, jul. 1971.
13. G. W. Westin, F. W. Ilfeld, e J. Provost, «Total avascular necrosis of the capital femoral epiphysis in congenital dislocated hips», Clin Orthop Relat Res, n.o 119, pp. 93–98, set. 1976.
14. C. Tauber, A. Ganel, H. Horoszowski, e I. Farine, «Distal transfer of the greater trochanter in cox vara», Acta Orthop Scand, vol. 51, n.o 4, pp. 661–666, ago. 1980, doi: 10.3109/17453678008990858.
15. G. C. Lloyd-Roberts, M. H. Wetherill, e M. Fraser, «Trochanteric advancement for premature arrest of the femoral capital growth plate», J Bone Joint Surg Br, vol. 67, n.o 1, pp. 21–24, jan. 1985, doi: 10.1302/0301-620X.67B1.3968136.
16. J. D. Bastian, A. T. Wolf, T. F. Wyss, e H. P. Nötzli, «Stepped osteotomy of the trochanter for stable, anatomic refixation», Clin Orthop Relat Res, vol. 467, n.o 3, pp. 732–738, mar. 2009, doi: 10.1007/s11999-008-0649-x.
17. R. E. Eilert, K. Hill, e J. Bach, «Greater trochanteric transfer for the treatment of coxa brevis», Clin Orthop Relat Res, n.o 434, pp. 92–101, mai. 2005, doi: 10.1097/01.blo.0000163474.74168.6f.
18. N. Shohat, R. Gilat, R. Shitrit, Y. Smorgick, Y. Beer, e G. Agar, «A long-term follow-up study of the clinical and radiographic outcome of distal trochanteric transfer in Legg-Calvé-Perthes’ disease following varus derotational osteotomy», Bone Joint J, vol. 99-B, n.o 7, pp. 987–992, jul. 2017, doi: 10.1302/0301-620X.99B7.BJJ-2016-1346.R2.
19. M. Lengsfeld, P. Schuler, e P. Griss, «The long-term (8-12 years) results of valgus and lengthening osteotomy of the femoral neck», Arch Orthop Trauma Surg, vol. 121, n.o 4, pp. 201–204, 2001, doi: 10.1007/s004020000214.
20. P. Lascombes, J. Prevot, A. Allouche, J. N. Ligier, e J. P. Metaizeau, «[Lengthening osteotomy of the femoral neck with transposition of the greater trochanter in acquired coxa vara]», Rev Chir Orthop Reparatrice Appar Mot, vol. 71, n.o 8, pp. 599–601, 1985.
21. R. Libri e L. Marchesini Reggiani, «A modified technique for reconstruction of the femoral neck in paediatric patients», Hip Int, vol. 20, n.o 4, pp. 529–534, 2010, doi: 10.1177/112070001002000418.
22. M. Leunig e R. Ganz, «Relative neck lengthening and intracapital osteotomy for severe Perthes and Perthes-like deformities», Bull NYU Hosp Jt Dis, vol. 69 Suppl 1, pp. S62-67, 2011.
23. L. A. Anderson, J. A. Erickson, E. P. Severson, e C. L. Peters, «Sequelae of Perthes disease: treatment with surgical hip dislocation and relative femoral neck lengthening», J Pediatr Orthop, vol. 30, n.o 8, pp. 758–766, dez. 2010, doi: 10.1097/BPO.0b013e3181fcbaaf.

1. Orthopedic Department Hospital del Mar. Universitat Autònoma de Barcelona
2. SPORTOKLINIK Orthopedics and Sports Medicine Center, Kraków, Poland
Orthopedic and Trauma Department Żeromski Specialist Hospital, Kraków, Poland
3. Ortoklinik & Cankaya Orthopedics, Ankara, Turkey

The Past

The first study published in the literature for the treatment of periprosthetic joint infection (PJI) was the one described by Carlsson for the treatment of total hip arthroplasty infections in 1978¹. Few years later, in 1981, Buchholz published a series of 586 patients treated with a one-stage exchange approach for PJI with excellent results. In this study, this German group described the state of the art for PJI diagnosis at that time2. Although they noted that “the proof of deep infection of the arthroplasty rests ultimately on a positive bacterial culture”, the authors realized that some patients with suspected preoperatively PJI did not yield a positive culture. Indeed they already claim 40 years ago that “we believe that sterile loosening are frequently due to a hidden infection not identified bacteriologically”². And they were right as we will see afterwards. I stress this sentence because surprisingly nowadays I still can see some surgeons that rule out infection because cultures are negative.

In the early 2000, Zimmerli included other features for the diagnosis of PJI, such as the presence of a sinus tract or purulent discharge³. Also, histopathological analysis of intraoperative samples showing acute inflammation, was included in this worldwide used diagnostic criteria. Another important advance in the diagnosis of PJI was the identification of a synovial fluid leucocyte cut-off (and differential) proposed by Trampuz⁴. Taking all of these items into account, some 10-20% of culture-negative PJI have been identified applying these diagnostic criteria⁵.

The Present

The aforementioned diagnostic tools have evolved along years. All of them are still valid nowadays and included in every proposed or revised diagnostic criteria. These are:

• Microbiological culture and bacterial (or fungal) identification
• Histopathological analysis for acute inflammation analysis.
• Leucocyte count and granulocyte percentage of synovial fluid
• Clinical features: sinus tract and purulent discharge.

Several advances have occurred in the microbiological diagnosis. Sonication of the prosthesis was described to remove bacterial biofilm and then facilitate culture. It has proven to improve diagnosis, especially in chronic PJI and patients receiving antibiotics ⁶. Another interesting advance is the use of PCR techniques. Although there is still room to improve, broad-spectrum PCR may help in reducing culture-negative PJI.

The assessment of periprosthetic tissue by an experienced pathologist is another diagnostic tool included in all PJI criteria. The cut-off of granulocytes per high-power field (HPF) differs between various criteria. However, it is commonly accepted that more than 5 granulocytes per HPF is definitely diagnostic of PJI (even when cultures are negative)⁷. Similarly, the cut-off for leucocyte count in the synovial fluid varies depending on the criteria used.

Recently, McNally et al published the EBJIS criteria for PJI that have been endorsed by the most important societies in the field⁸. It is true that this is not the definitive one, but for sure this is the most recommended at the moment. Future diagnostic tools will improve PJI identification and diagnosis. Moreover, it is freely available in a user-friendly infographic⁹.

The Future

Improvements in microbiological methods are expected in the near future. Faster techniques and new tools to decrease culture-negative PJI will appear in the next years. Artificial intelligence (AI) will definitely play a role in the diagnosis of PJI. Information about gait, consumption of analgesics, activity or sport level may be correlated with loosening of the implants; furthermore this data, combined with patient-specific risk-factors may help in the diagnosis of PJI with higher accuracy. Moreover, artificial intelligence or monitoring the patient with intelligent implants may provide data on altered knee kinematics, increase in temperature or joint volume (effusion) that will be red flags to rapidly consult the physician.

References
1. Carlsson AS, Josefsson G, Lindberg L. Revision with gentamicin-impregnated cement for deep infections in total hip arthroplasties. J Bone Joint Surg Am 1978;60(8):1059–1064.
2. Buchholz HW, Elson RA, Engelbrecht E, Lodenkämper H, Röttger J, Siegel A. Management of deep infection of total hip replacement. J Bone Joint Surg Br 1981;63-B(3):342–353.
3. Zimmerli W, Trampuz A, Ochsner PE. Prosthetic-joint infections. N Engl J Med 2004;351(16):1645–1654.
4. Trampuz A, Hanssen AD, Osmon DR, Mandrekar J, Steckelberg JM, Patel R. Synovial fluid leukocyte count and differential for the diagnosis of prosthetic knee infection. Am J Med 2004;117(8):556–562.
5. Renz N, Yermak K, Perka C, Trampuz A. Alpha Defensin Lateral Flow Test for Diagnosis of Periprosthetic Joint Infection: Not a Screening but a Confirmatory Test. J Bone Joint Surg Am 2018;100(9):742–750.
6. Trampuz A, Piper KE, Jacobson MJ, Hanssen AD, Unni KK, Osmon DR, et al. Sonication of removed hip and knee prostheses for diagnosis of infection. The New England journal of medicine 2007;357(7):654–663.
7. Krenn V, Morawietz L, Perino G, Kienapfel H, Ascherl R, Hassenpflug GJ, et al. Revised histopathological consensus classification of joint implant related pathology. Pathol Res Pract 2014;210(12):779–786.
8. McNally M, Sousa R, Wouthuyzen-Bakker M, Chen AF, Soriano A, Vogely HC, et al. The EBJIS definition of periprosthetic joint infection. Bone Joint J 2021;103-B(1):18–25.
9. McNally M, Sousa R, Wouthuyzen-Bakker M, Chen AF, Soriano A, Vogely HC, et al. Infographic: The EBJIS definition of periprosthetic joint infection. Bone Joint J 2021;103-B(1):16–17.

¹3rd Orthopaedic Department, Hygeia Hospital | Greece
² ESSKA-ESA Board Member

Comparison between Bone Marrow Aspirate and Concentrate Samples Harvested from Three Different Anatomic Sites as Augmentation to Arthroscopic Treatment of Rotator Cuff Tears.

Mesenchymal stem cells (MSCs) are bone marrow stromal cells which are present in all types of tissues and are currently considered as the “gold standard” for biologic augmentation of arthroscopic treatment of rotator cuff tears.¹ These cells have been shown to demonstrate high differentiation potential in regenerative medicine as they play an important role in the healing process of injured bones, ligaments, tendons and cartilage.^2-6 The number of MSCs in bone marrow ranges from 1 in 104 to 1 in 106 mononuclear cells. This heterogeneous population of units was described in 1968 by Friedenstein as Colony Forming Units (CFUs) as they can differentiate into various mesenchymal tissues.^4-5 The total number of immature blood cells and non-blood or stromal cells in bone marrow are characterized as Total Nucleated Cells (TNC). Therefore, the efficiency of bone marrow aspirates depends on the aspiration technique and the culture process as it may be negatively affected by other cell populations because of blood dilution.

Aspiration technique plays an important role in the quality of the bone marrow samples in relation to the concentration of the osteogenic cells and the differentiation potential. The yield of osteoprogenitor cells is further increased by a greater concentration of the aspirate sample which is then characterized as bone marrow aspirate concentrate.

The aim of this study was to evaluate the levels of Total Nucleated Cells (TNC), Platelets (PLTs) and Colony Forming Units (CFU- Fs) in bone marrow aspirate samples compared to bone marrow concentrates as well as compare the quantitative and qualitative characteristics of bone marrow samples obtained from three different anatomic sites, the anterior and posterior superior iliac spine and the proximal tibia using the same aspiration technique. No clinical outcomes were reported.

A retrospective comparative study was conducted. Bone marrow samples were obtained from three different anatomic sites with the same aspiration technique and were processed with the same centrifugation system for augmentation of arthroscopic treatment of rotator cuff tears. Total Nucleated Cells, Platelets and Colony Forming Units levels were evaluated in bone marrow aspirate and concentrate samples obtained from all three anatomic sites. No further clinical evaluation was conducted.

One hundred and thirteen patients were included in the study. Of 113 patients, 51 patients - 31 females and 20 males - were included in Group A (anterior superior iliac spine), 26 patients - 16 females and 10 males - in Group B (proximal tibia) and 26 patients - 18 females and 8 males - in group C (posterior superior iliac spine). The mean age of patients was 58.13 ± 13.35 years in Group A, 55 ± 13.25 years in Group B and 46 ± 16.12 in group C. Age between group A and C was significantly different (p=0.002).

In the operating room, patients received general anaesthesia and harvest sites were prepared. Samples were collected from the anterior iliac crest (51) (Figure 1), the proximal tibia (26) (Figure 2) and the posterior iliac crest (26) (Figure 3). As per manufacturer instructions, at each individual site, 5 mL were aspirated, and the Jamshidi- style trocar needle was then rotated 90 degrees. After the next 5 mL were aspirated, the needle was advanced 1–2 cm, and the process was repeated. After harvesting, the skin entry incision was properly attended and dressed. BMA was collected into a sterile conical tube and transported to the laboratory for analysis. This sample was taken just prior to centrifugation step and was thus considered representative of the unconcentrated bone marrow aspirate (BMA) produced by the system. The remaining BMA was placed in the system centrifuge for concentration in accordance with manufacturer’s directions.

When comparing the levels of TNC, PLTs and CFU-fs in bone marrow aspirates, we found that total nucleated cell count of bone marrow aspirate from the posterior superior iliac spine was 31.23% higher than from anterior superior iliac spine while platelet count from the tibia was 4 times higher than from the posterior superior iliac spine. Total Colony-Forming Unit formations were significantly higher (28.84%) in the posterior compared to the anterior superior iliac spine. The quality of bone marrow concentrate was significantly higher with no significant difference between the different cites of extraction.

The expanding use of bone marrow aspirate in the field of regenerative medicine resulted in the increasing use of BMA and BMAC as a biological scaffold augmenting various orthopedic procedures, including shoulder arthroscopy. In 2013 Marx et al demonstrated the results of bone marrow aspirates of sixty patients in total. Twenty samples were obtained from the anterior ilium, 20 samples from the posterior ilium and 20 samples from the tibial plateau. The authors concluded that the ilium is preferable for harvesting multipotent stem cells compared to the tibia.⁷ In the same year, Hyer et al compared the quality of bone marrow samples obtained by three different harvest sites, anterior iliac crest, tibia and calcaneus. The number of total nucleated cells was significantly higher in the samples obtained from the ilac crest compared to the samples obtained from the distal tibia and the calcaneus.³ Pierini et al compared the quality of bone marrow samples obtained from the anterior and posterior iliac crest in 22 patients with a mean age of 37 years. The study demonstrated significantly higher levels of Colony Forming Units in the samples obtained from the posterior iliac crest compared to the anterior iliac crest.⁸ These results were consistent with our study.

The number of Colony Forming Units (CFUs) is increasing with increasing number of aspiration sites while age, BMI and medical comorbidities seem to affect CFUs yield.^9-10 Aspiration of small volumes is another way of avoiding blood dilution. However multiple- site aspiration requires more time to obtain the desired volume of bone marrow. Strong aspiration seems to increase the negative pressure needed for the higher concentration of MSCs whereas filling the syringe decreases the desired pressure for obtaining a high- quality aspiration sample.¹¹ In another study, higher quality samples were obtained by rapid aspiration compared to the slow- aspiration patient group.¹²

Several authors reported that a small volume of aspirated bone marrow is associated with a lower risk of blood dilution.¹³ Aspiration volume lower than 10ml is generally associated with an increasing number of MSCs and it may be obtained by single-site aspiration in multiple depths achieved by rotation of the syringe in use.¹⁴ As aspiration volume also depends on the volume of the aspiration site, it is essential to avoid vessels at the time of aspiration and in this way avoid dilution of the sample by the peripheral blood and decrease the number of MSCs.

Our study demonstrated an aspiration technique which allows the aspiration of small volumes from different depths of the same site after sequential rotation to avoid dilution and increase the quality of the obtained bone marrow samples. The purpose was to evaluate the levels of Total Nucleated Cells (TNC), Platelets (PLTs) and Colony Forming Units (CFU- Fs) in BMA compared to BMAC as well as compare the quantitative and qualitative characteristics of bone marrow samples obtained from three different anatomic sites, the anterior and posterior superior iliac spine and the proximal tibia using the same aspiration technique.

There are some studies that support that the proximal humerus is also suitable as a potential donor site for harvesting bone marrow.¹⁵ In our practice during shoulder arthroscopy, it was very difficult to obtain a clear sample of bone marrow because of the existence of a large volume of fluid and the absence of watertightness of the aspiration trocar during the procedure.

In conclusion, proximal tibia and the anterior and posterior superior iliac spine can be considered as reliable sources of bone marrow aspirate for use in biologic augmentation during arthroscopic treatment of rotator cuff tears. However, bone marrow aspirates from the posterior superior iliac spine yielded significantly higher colony-forming units and higher TNC levels than the anterior superior iliac spine and the tibia. Bone marrow concentrates yielded significantly higher TNC, and CFU-f levels compared to bone marrow aspirate samples obtained from all three anatomic sites.

Figure 1: Bone marrow aspiration from the anterior superior iliac spine.

Figure 2: Bone marrow aspiration from the proximal tibia.

Figure 3: Bone marrow aspiration from the posterior superior iliac spine.

References
1. Hernigou P, Flouzat Lachaniette CH, Delambre J, Zilber S, Duffiet P, Chevallier N, et al. Biologic augmentation of rotator cuff repair with mesenchymal stem cells during arthroscopy improves healing and prevents further tears: a case-controlled study. Int Orthop. 2014 Sep;38(9):1811-8.
2. Friedlis MF, Centeno CJ. Performing a Better Bone Marrow Aspiration. Phys Med Rehabil Clin N Am. 2016 Nov;27(4):919-939. doi: 10.1016/j.pmr.2016.06.009. PMID: 27788908.
3. Hyer CF, Berlet GC, Bussewitz BW, Hankins T, Ziegler HL, Philbin TM. Quantitative assessment of the yield of osteoblastic connective tissue progenitors in bone marrow aspirate from the iliac crest, tibia, and calcaneus. J Bone Joint Surg Am. 2013 Jul 17;95(14):1312-6. doi: 10.2106/JBJS.L.01529. PMID: 23864180.
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5. Otto A, Muench LN, Kia C, Baldino JB, Mehl J, Dyrna F, Voss A, McCarthy MB, Nazal MR, Martin SD, Mazzocca AD. Proximal Humerus and Ilium Are Reliable Sources of Bone Marrow Aspirates for Biologic Augmentation During Arthroscopic Surgery. Arthroscopy. 2020 Sep;36(9):2403-2411. doi: 10.1016/j.arthro.2020.06.009. Epub 2020 Jun 15. PMID: 32554079.
6. Roukis TS, Hyer CF, Philbin TM, Berlet GC, Lee TH. Complications associated with autogenous bone marrow aspirate harvest from the lower extremity: an observational cohort study. J Foot Ankle Surg. 2009 Nov-Dec;48(6):668-71. doi: 10.1053/j.jfas.2009.07.016. Epub 2009 Aug 26. PMID: 19857823.
7. Marx RE, Tursun R. A qualitative and quantitative analysis of autologous human multipotent adult stem cells derived from three anatomic areas by marrow aspiration: tibia, anterior ilium, and posterior ilium. Int J Oral Maxillofac Implants. 2013 Sep-Oct;28(5):e290-4. doi: 10.11607/jomi.te10. PMID: 24066346.
8. Pierini M, Di Bella C, Dozza B, Frisoni T, Martella E, Bellotti C, Remondini D, Lucarelli E, Giannini S, Donati D. The posterior iliac crest outperforms the anterior iliac crest when obtaining mesenchymal stem cells from bone marrow. J Bone Joint Surg Am. 2013 Jun 19;95(12):1101-7. doi: 10.2106/JBJS.L.00429. PMID: 23783207.
9. LaPrade RF, Murray IR. Editorial Commentary: Bone Marrow Aspirate Concentrate: Time to Harvest Locally? Arthroscopy. 2020 Sep;36(9):2412-2414. doi: 10.1016/j.arthro.2020.07.015. PMID: 32891243.
10. Li H, Ghazanfari R, Zacharaki D, Lim HC, Scheding S. Isolation and characterization of primary bone marrow mesenchymal stromal cells. Ann N Y Acad Sci. 2016;1370(1):109-18. doi: 10.1111/nyas.13102. PMID: 27270495.
11. Hernigou P, Homma Y, Flouzat Lachaniette CH, Poignard A, Allain J, Chevallier N, Rouard H. Benefits of small volume and small syringe for bone marrow aspirations of mesenchymal stem cells. Int Orthop. 2013 Nov;37(11):2279-87. doi: 10.1007/s00264-013-2017-z. Epub 2013 Jul 24. PMID: 23881064; PMCID: PMC3824897.
12. Grønkjær M, Hasselgren CF, Østergaard AS, Johansen P, Korup J, Bøgsted M, Bilgrau AE, Jensen P. Bone Marrow Aspiration: A Randomized Controlled Trial Assessing the Quality of Bone Marrow Specimens Using Slow and Rapid Aspiration Techniques and Evaluating Pain Intensity. Acta Haematol. 2016;135(2):81-7. doi: 10.1159/000438480. Epub 2015 Oct 28. PMID: 26505268.
13. Fennema EM, Renard AJ, Leusink A, van Blitterswijk CA, de Boer J. The effect of bone marrow aspiration strategy on the yield and quality of human mesenchymal stem cells. Acta Orthop. 2009 Oct;80(5):618-21. doi: 10.3109/17453670903278241. PMID: 19916699; PMCID: PMC2823327.
14. Oliver K, Awan T, Bayes M. Single- Versus Multiple-Site Harvesting Techniques for Bone Marrow Concentrate: Evaluation of Aspirate Quality and Pain. Orthop J Sports Med. 2017 Aug 29;5(8):2325967117724398. doi: 10.1177/2325967117724398. PMID: 28890905; PMCID: PMC5580846.
15. Muench LN, Kia C, Otto A, Mehl J, Baldino JB, Cote MP, McCarthy MB, Beitzel K, Mazzocca AD. The effect of a single consecutive volume aspiration on concentrated bone marrow from the proximal humerus for clinical application. BMC Musculoskelet Disord. 2019 Nov 14;20(1):543. doi: 10.1186/s12891-019-2924-2. PMID: 31727036; PMCID: PMC6857344.

¹ Associate Professor; Department of Orthopaedics, PGIMER, Chandigarh, India
² Sporthopaedicum Regensburg/Straubing, Germany
³ Department of Trauma Surgery, University Hospital Regensburg, Germany

Shoulder arthroplasty has emerged as a gold standard for various indications including advanced osteoarthritis and rotator cuff arthropathy of the shoulder joint. Although the results have been generally good, yet there is always a scope for improvement. Proper glenoid positioning is considered an essential element for achieving long-term success in shoulder arthroplasty. Conventional methods of using plain radiographs or two-dimensional CT scan frequently result in misinterpretation of inclination and glenoid version as compared to three-dimensional CT scans¹. Although the intention of a surgeon is never to land up in a complication, stakes are higher when "quality of life enhancing" surgery is performed as compared to a "life-saving" procedure, and shoulder arthroplasty if done in non-traumatic conditions generally belongs to the former category. Nothing can be left to chance, not least with improper glenoid placement, especially in cases with pre-existing glenoid deformity or bone loss.

We are currently in the age of advanced technology and the influence of "augmented reality" can be seen in every aspect of our life and the field of shoulder arthroplasty is no exception to it. One recent trend in the last few years to improve glenoid placement is the use of preoperative planning software (PPS). This commentary is an attempt to introduce the readers to the recent trend of the use of PPS, its advantages and disadvantages, and some commercially available PPS.

Multiple commercial and non-commercial groups have reported the use of computer planning software to simulate glenoid implantation^2-4. These preoperative planning softwares have demonstrated improvement in both bone models and actual surgical procedures ^2,3. Iannotti et al³ reported in a randomized controlled trial of 46 patients that they could place the glenoid component within 5 degrees of desired inclination and 10 degrees of desired version with three-dimensional templating and computer planning when compared to standard techniques. Venne et al⁵ in a cadaveric lab study also reported that computer planning and navigation improved the accuracy and precision of screw placement and higher precision of baseplate placement. Although these studies hint towards increased accuracy, until now there are no published reports of improvement in patient-reported outcomes or long-term survivorship of implants as these softwares are in the stage of "recent advancements".

It needs to be emphasized, especially for the new shoulder arthroplasty surgeons, that these softwares do not replace the need to have an "in-depth" understanding of the shoulder anatomy and its variations. The surgeon must be fully aware of the traditional preoperative planning which involves the standard AP view (Grashey view), scapular Y view and axillary view along with the assessment of two-dimensional and three-dimensional CT cuts especially when there is altered glenoid anatomy. It is equally relevant to understand how conventional two-dimensional measurements, three-dimensional measurements, and software measurements are correlated to each other.

For glenoid inclination in reverse shoulder arthroplasty, the typical guidelines recommend neutral tilt. However, this estimate is based on the implant positioning in AP radiograph which accounts for both scapulothoracic and glenohumeral positioning. In software planning, the scapulothoracic joint position is difficult to be accounted and further research is awaited to determine the method of including scapulothoracic positioning in inclination of glenoid baseplate. (Fig. 1) So, the surgeon should have an orientation of glenoid inclination in a normal radiograph before he jumps to the software-directed positioning so that he can improvise intraoperatively in case the predetermined positioning appears to be incorrect.

Higher retroversion also leads to early failure in shoulder arthroplasty. However, there is always a lack of complete agreement between the two-dimensional, three-dimensional, and software generated measurement in glenoid version. Budge et al⁶ did a comparison of two-dimensional and three-dimensional methods and reported that in 50% of cases, there was a difference of 5-15 degrees in version. Erickson et al⁷ also demonstrated significant difference in both version and inclination in the preoperative planning between CT scan and software-based methods. The difference may arise because there is no fixed and standardized CT scan protocol for measurement of anteroposterior location for inclination measurement or superior-inferior location for version measurement⁸.

And to make matters complicated, there are also disagreements within the various software-based methods. Currently, we are spoiled for choices as several companies are available for preoperative planning for shoulder arthroplasty. Each system is slightly different based on the reference of the position of the guide. The commonly used software systems include Virtual Implant positioning VIP (Arthrex, Naples, FL, USA), Blueprint (Wright Medical, Memphis, TN, USA), GPS (Exactech, Gainesville, FL, USA) and Materialise (DJO, Vista, CA, USA). VIP, Materialise, and GPS use anatomical landmarks to determine the plane of the scapula to determine the position of maximum coverage (Fig. 2) while Blueprint uses an average plane of the scapula and the best-fit sphere method. It is yet unknown, which method is better to approximate the true anatomy and provides better practise of glenoid placement.

Erickson et al⁷ analyzed 81 preoperative CT scans by using these four software systems and five fellowship-trained shoulder surgeons and compared the preoperative planning for version and inclination. The authors reported that software methods produced more inclination and more retroversion. Also, there were variations within the software groups. VIP and Blueprint overestimated inclination by 2 degrees and GPS underestimated inclination by 2 degrees. Denard et al¹ also evaluated the differences in inclination and version between two commonly used PPS systems (VIP and Blueprint). The authors reported a difference of 5 or more degrees in inclination and version in 46% and 30% of cases. Intra-group variations between the software planning methods may arise as some systems are "semiautomated" and rely on manual input of the standard anatomic landmarks while other systems could be fully automated volume-based systems¹.

The number of shoulder arthroplasties is expected to increase in the future. We endeavour to maximize patient satisfaction and clinical outcome and minimize complications. 3D CT scan is currently the gold standard for the assessment patient’s glenoid anatomy and planning for glenoid placement in shoulder arthroplasty. The use of preoperative planning software is on the rise amongst shoulder surgeons to improve the understanding of the complexity of the anatomy and glenoid placement. But surely, it goes without saying that these softwares are best used for augmentation and not a replacement for surgeon's thoughts and understanding. Grady Booch once famously said "A fool with a tool is still a fool". We don't contradict the statement but "A wise man with a gadget will find himself in the higher bracket" also makes sense. In essence, a sound surgeon can benefit from such advancements yet in adversity, should trust his judgment while the average one can still make mistakes.

Cost-benefit effectiveness has always been a roadblock for recent advances and we leave it to the future to see how titration between the "additional costs" and "improved longevity" affects to acceptance of PPS, but one thing is sure, and we are threading into the right direction.

Figure 1: A representative figure taken from VIP (Virtual implant positioning) software determining the native (3⁰) and implant (0) inclination and native (-1⁰) and implant version (0).

Figure 2A

Figure 2B

¹ Orthopedic Clinic, Centro specialistico ortopedico Traumatologico G.Pini-CTO, Milano, Italy
² Università degli studi di Milano, Milano, Italy
³ Department of Orthopaedic Surgery, Hospital del Mar, Universitat Autònoma de Barcelona, Barcelona, Spain

Introduction

Elective primary total knee arthroplasty (TKA) is a commonly performed surgical procedure in orthopedics worldwide. With the demographic shift towards an aging population, the number of TKA surgeries is expected to rise in the upcoming decade. Despite its popularity, patient dissatisfaction rates as high as 20% have been reported in multiple studies. Isolating a single cause of failure is challenging, but component malposition is clearly one of the most likely factors as it can influence proper alignment of the weight-bearing axis and soft tissue balance. To address this issue, computer-assisted TKA (CA-TKA) and robot-assisted TKA (RA-TKA) are emerging as promising solutions. These technologies leverage the ability of computers to process large sets of data to achieve a reproducible outcome, thereby reducing cutting errors that may lead to component malposition by assisting in guide placement and simulating the result before starting the surgery.

How does RA-TKA work?

Robot-assisted TKA (RA-TKA) involves the use of an intelligent tool to perform the surgical cuts. The intelligence of the tool lies in its ability to collect data, interpret it, and provide precise and accurate results, such as the position of the bony cuts required for the procedure.

Robotic devices used in surgery can be classified based on their degree of freedom during the procedure. The classification includes active, semi-active, and passive robotic devices. An active robotic device can perform the surgical cuts by itself, without the need for direct action from the surgeon.

A semi-active robotic device requires active participation from the surgeon, who operates the tool while being guided by the robot's control system. The robot provides real-time haptic feedback to the surgeon to facilitate precise execution of cuts according to the preoperative plan. Haptic feedback allows the surgeon to experience the tactile sensation of bone cutting during the surgical procedure (fig 1). This sensory information can help the surgeon adjust their movements and apply the appropriate force, leading to the desired precision and accuracy during the surgery. In contrast, a passive robotic device is more similar to computer-assisted TKA (CA-TKA) in which the robot only assists in identifying the correct position of the guiding tool used by the surgeon.

It is also possible to categorize robotic devices based on whether they rely on preoperative imaging of the patient that must be integrated intraoperatively (image-based) or exclusive intraoperative data acquisition using bony landmark registration (image-less). The main objective is to create a three-dimensional model that emulates the patient's anatomy for the purpose of evaluating the balance of ligaments prior to implant placement. This will ensure that the flexion and extension gaps are appropriately balanced, the joint stability is maintained, the range of motion is optimized, and the alignment of the limb is preserved (fig 2).

However, despite being used as a surgical tool for executing bony cuts, equivalent to motors and guides, most robotic systems function as closed platforms that restrict the surgeon to a chose the robot manufacturer's implant design, irrespective of the patient's specific requirements.

What robotic device should I use to perform TKA in my daily practice?

Compared to conventional TKA, RA-TKA demonstrates superior accuracy in implant positioning, as evidenced by a reduction in the number of outliers exceeding 3° from the preoperative plan and average positioning within 1º of planned position in all three planes.(1) Moreover, RA-TKA achieves enhanced restoration of native joint line, Insall-Salvati ratio, and posterior condylar offset ratio, in addition to improving alignment.

In spite of this improvement in objective measures, evidence is still needed to determine whether an increased precision is related to an actual improvement of functional outcomes and implant survivorship rates.

In the short-term, the outcomes are encouraging. The use of RA-TKA involves a lower level of manipulation of the soft tissue, resulting in reduced injury and subsequent inflammatory response in the surrounding tissue. This leads to a lower degree of postoperative pain and swelling, requiring reduced perioperative analgesia and a shorter period of physical therapy as compared to conventional TKA. Hospital stay and postoperative nursing requirements have also decreased when using RA-TKA.(2)

This is accompanied by a short-term improvement in functional outcomes, as evidenced by improvements in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Knee Society Score (KSS) reported in various studies.(3)

Furthermore, restriction of bony cuts by the robot within the preoperative defined limits is associated with a decrease in incidence of posterior cruciate ligament injury, tibial subluxation, and patella eversion, as compared to hand-free cuts.

Nevertheless, quality studies assessing medium or long-term impact of robotic assistance are scarce. The enhanced accuracy of implant positioning and improvement in postoperative functional scores achieved through RA-TKA are comparable to those of conventional TKA in the long-term, as is the survivorship of the implant for as long as 10 years.

Why not use these robotic devices?

One of the major drawbacks of RA-TKA is the substantial installation and maintenance costs. Not only by purchasing a robotic device (which ranges from $600k to $1.5Mk) but for additional preoperative imaging, training of the surgical team and updating the computer software, not to mention that each robotic device is only compatible with a limited number of implant designs.

This cost may partially offset as RA-TKA is associated with shorter hospital stay, reduced need for analgesia, lower readmission rates and decreased need for physiotherapy.

The number of annual cases necessary for RA-TKA to be theoretically cost-effective is 253 per year limiting access of this robot devices to only high-volume surgeons and thus biasing the potential results by its expertise.(4)

This increase of cost is associated with either preoperative time delays for the remote planning team to template the optimal implant size and positioning and longer intraoperative times during the initial learning phase. Although the learning curve for operative times and surgical team confidence levels is around seven to twenty cases, depending on the source, there is no learning curve effect for achieving planned femoral and tibial implant positioning. And thereafter, the intraoperative time with RA-TKA is comparable to conventional TKA.(5,6)

Not to be forgotten, RA-TKA requires additional incisions to insert all the optical sensors needed to enable motion-capture tracking.

Future perspectives

There is enough evidence to state that the assistance of a surgical robot improves implants positioning and limb alignment. However, it is clear that this technology is still in its early stages and that there is a long road ahead to establish and confirm the potential benefits that are starting to emerge.

This change of paradigm in the procedure of TKA will start to face big challenges. As the costs of this robots decrease as open platforms start to gain ground we will probably face with vast evidence as more and more healthcare providers will be able to afford this technology.

The majority of these devices utilize machine-learning algorithms that enhance their performance with each subsequent case, as data gathered from previous procedures are incorporated to fine-tune their outputs. As such, over time, they are expected to become increasingly reliable and precise, potentially resulting in a reduced role for surgeons in certain aspects of the surgical process, with their involvement primarily limited to supervising the work of the robot and therefore improving the workflow of the surgical room.

Nevertheless, the integration of new technologies such as mixed reality, which superimposes simulated images onto real-life images, is expected to expand the range of capabilities of these robots even further.

But for now, it is crucial to establish the long-term outcomes of robot-assisted total knee arthroplasty as a process to determine the viability of widespread implementation of these devices.

Figure 1: The robot is guiding the surgeon to perform the distal tibial cut (semiactive robot). No physical guides are being used to perform the bony cuts.

Figure 2: Trackers in the tibia and the fibula allow the robot to generate a 3D model to plan the cuts

Biography
1. Song EK, Seon JK, Park SJ, Jung W Bin, Park HW, Lee GW. Simultaneous bilateral total knee arthroplasty with robotic and conventional techniques: a prospective, randomized study. Knee Surg Sports Traumatol Arthrosc [Internet]. 2011 Jul [cited 2023 Mar 18];19(7):1069–76. Available from: https://pubmed.ncbi.nlm.nih.gov/21311869/
2. Kayani B, Konan S, Tahmassebi J, Rowan FE, Haddad FS. An assessment of early functional rehabilitation and hospital discharge in conventional versus robotic-arm assisted unicompartmental knee arthroplasty: a prospective cohort study. Bone Joint J [Internet]. 2019 Jan 1 [cited 2023 Mar 18];101-B(1):24–33. Available from: https://pubmed.ncbi.nlm.nih.gov/30601042/
3. Ren Y, Cao S, Wu J, Weng X, Feng B. Efficacy and reliability of active robotic-assisted total knee arthroplasty compared with conventional total knee arthroplasty: a systematic review and meta-analysis. Postgrad Med J [Internet]. 2019 [cited 2023 Mar 18];95(1121). Available from: https://pubmed.ncbi.nlm.nih.gov/30808721/
4. Cool CL, Jacofsky DJ, Seeger KA, Sodhi N, Mont MA. A 90-day episode-of-care cost analysis of robotic-arm assisted total knee arthroplasty. J Comp Eff Res [Internet]. 2019 Apr 1 [cited 2023 Mar 18];8(5):327–36. Available from: https://pubmed.ncbi.nlm.nih.gov/30686022/
5. Kayani B, Konan S, Huq SS, Tahmassebi J, Haddad FS. Robotic-arm assisted total knee arthroplasty has a learning curve of seven cases for integration into the surgical workflow but no learning curve effect for accuracy of implant positioning. Knee Surg Sports Traumatol Arthrosc [Internet]. 2019 Apr 5 [cited 2023 Mar 18];27(4):1132–41. Available from: https://pubmed.ncbi.nlm.nih.gov/30225554/
6. Sodhi N, Khlopas A, Piuzzi NS, Sultan AA, Marchand RC, Malkani AL, et al. The Learning Curve Associated with Robotic Total Knee Arthroplasty. J Knee Surg [Internet]. 2018 Jan 1 [cited 2023 Mar 18];31(1):17–21. Available from: https://pubmed.ncbi.nlm.nih.gov/29166683/

¹Consultant Orthopaedic Surgeon – Cambridge Young Adult Hip Service
Addenbrookes – Cambridge University Hospital NHS Foundation trust, United Kingdom
²Consultant Orthopaedic Surgeon – Cambridge Young Adult Hip Service
Affiliate Associate Professor – University of Cambridge
Addenbrookes – Cambridge University Hospital NHS Foundation trust, United Kingdom
Chair – ESSKA European Hip Preservation Associates
Past President – British Hip Society

Femoroacetabular impingement (FAI) has gained considerable focus in the last two decades since Ganz et al published the possible association of FAI with the development of osteoarthritis [2]. There has been a significant progress in the treatment of FAI from the initial open surgical dislocation described by Ganz to the recent advances in arthroscopic hip surgery [3]. FAI can be classified into (1) cam deformity – an abnormality of the femoral head-neck junction with a reduced head-neck offset, (2) pincer deformity – an acetabular over coverage with a lateral centre-edge angle of > 40° and (3) mixed type with features of both cam and pincer deformities. Cam deformity (figure 1) has gained considerable interest because this is the most common type of FAI and is defined as an alpha angle of > 55° (figure 2). Advanced hip arthroscopic techniques are aimed at correcting this morphological abnormality and concurrently treat the resultant pathology of the acetabular labrum and articular cartilage. However, we still do not understand as to who and how does one develop a cam deformity.

There are concerns that the development of cam may be linked to an increased level of sporting activity whilst the physis is still open predisposing to morphological abnormalities. Repetitive impact due to high level sporting activities increases the stress at the physis potentially leading to the development of cam deformity. Our group has tried to evaluate the current available literature on development of the cam deformity in athletes and whether there is an association between development of the cam deformity and different sporting activities [1, 5], A systematic review (SR) was undertaken to answer each question.

Figure 1: CT scan with 3D reconstruction showing cam deformity of both hips

Figure 2: Alpha angle measurement on lateral view of the hip joint.

Our first SR aimed to determine the aetiology of the cam morphology in athletes looking at three main issues (1) timing of development of cam deformity in relation to physeal closure, (2) whether cam deformity was associated with other proximal femoral deformities and (3) effect of sporting activities and the duration of training on cam development [5]. This SR identified 16 articles reporting on the development of cam lesion, out of which 12 were used for quantitative synthesis of results with a meta-analysis. We noted a greater incidence of a higher alpha angle in the anterosuperior femoral neck in male athletes after physeal closure [5]. However, there was no conclusive association between physeal closure and the prevalence of cam deformity per hip. Interestingly, age of the individual was found to be a significant predictor for cam deformity not only for the prevalence per hip but also prevalence per individual. A two-phase meta-regression model showed that age was associated with cam deformity for both per hip and per individual. This supports that fact that cam deformity potentially develops at the time of growth spurt and just before physeal closure. In addition, the SR found a strong positive correlation between epiphyseal extension and alpha angle. This may perhaps be a result of the cartilaginous physis undergoing temporal displacement from 11 o’clock to 2 o’clock eventually leading to the development of the cam deformity in this region. Furthermore, a positive correlation between those individuals who trained more than 4 times a week and the development of cam deformity was identified. Therefore, the younger the child the more likelihood they developed cam deformity with a higher alpha angle, if they trained more than 4 times or played sport. Similarly, there was a positive association between the length of the sporting career and alpha angle in adults. Therefore, our first SR revealed that those individuals who regularly played sport or trained more than 4 times a week from an early age were at risk of developing cam deformity [5].

Our second SR aimed to assess (1) prevalence of cam-type FAI across various sports, (2) whether kinematic variation among sports influenced morphology of the hip and (3) whether performance level, duration and frequency of training in this population influenced hip morphology [1]. This SR identified 49 articles which described a higher prevalence of cam-type FAI in athletes compared to asymptomatic general population. Athletes were 1.83 times more likely to be diagnosed with FAI when compared to non-athletes. Sports which involve recurrent movement of the hip beyond normal range of motion (flexion, adduction and internal rotation) leading to impingement were associated with the highest prevalence of cam FAI. In addition, contact sports and those involving cutting movements reported high prevalence of cam deformity. This SR found that the athletes had a significantly higher mean alpha angle than controls. Ice hockey players were noted to have the highest prevalence of cam-type FAI. They also noted that elite ice hockey players were 3 times more likely to develop cam deformity compared to the general population [1]. This is potentially because the hip is put through increased stress from an early age for a longer period of time, which has been shown to have an association with cam development in our first SR [5].

Moreover, Ice hockey players were also 4 times more likely than skiers to have an alpha angle more than 550. There was a higher incidence of FAI with cam impingement in ice hockey players when compared to skiers (79% vs 40% respectively). This higher incidence of FAI in ice hockey players may be a result of the repetitive stress placed on the hip because of the unique impinging skating motion. Similarly, ice hockey butterfly goalkeepers were at risk of cam-type FAI as their hips are in a flexed, adducted and internal rotated position. Furthermore, mogul and Alpine skiers were also reported to have a significantly higher prevalence of cam versus controls. This type of skiing involves high ground reaction forces, and acrobatic jumps resulting in high-impact landings. These results reinforce the idea that when the hips are put under an extreme biomechanical stress, there is a potential to develop cam deformity suggesting that the type of sport influences morphology of the hip. In addition, those who participated in martial arts had a higher incidence of cam deformity compared with those whose primary sport was not a martial art [1].

Interestingly, the location of the maximum alpha angle varied in different ice hockey players. The positional players had maximum alpha angle at 1:45 o’clock position compared to 1 o’clock seen in goalkeepers [1]. This again supports the fact that the position of the hips during sport and training predisposes to the site of cam development. A higher proportion of cam deformity with a larger alpha angle was associated with increasing age. However, the prevalence of cam deformity was lower is East Asian athletes when compared to Caucasian players who played soccer. Interestingly, there was no difference in the hip morphology amongst different ethnicities in the Japanese baseball league. This is something which needs exploring further as baseball is not an impingement sport and perhaps the stress on the hip joint during physeal growth is not as much as during impingement type of sporting activities. Therefore, this further supports the fact that not only there is a genetic component to the development of cam deformity but also a mechanical component during growth which contributes to the development of the cam deformity.

Our two systematic reviews have shown that biomechanical factors play an important role in the development of cam deformity. Playing sport or training more than four times a week from an early age increased the risk of developing cam deformity. In addition, sports which increased the stress in the hip joint for long periods of time, such as in flexion, adduction and internal rotation, showed an increased prevalence of cam deformity. Further longitudinal research is urgently needed to confirm these findings with long term monitoring of children engaged in sporting academies to assess whether there they do go on to develop cam deformity and if yes then to inform on the appropriate time and regime of training.

References
1. Doran C, Pettit M, Singh Y, Sunil Kumar KH, Khanduja V (2022) Does the Type of Sport Influence Morphology of the Hip? A Systematic Review. Am J Sports Med 50:1727–1741
2. Ganz R, Parvizi J, Beck M, Leunig M, Nötzli H, Siebenrock KA (2003) Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res 112–120
3. Khanduja V, Villar RN (2006) Arthroscopic surgery of the hip: current concepts and recent advances. J Bone Joint Surg Br 88:1557–1566
4. Mirtz TA, Chandler JP, Eyers CM (2011) The effects of physical activity on the epiphyseal growth plates: a review of the literature on normal physiology and clinical implications. J Clin Med Res 3:1–7
5. Pettit M, Doran C, Singh Y, Saito M, Sunil Kumar KH, Khanduja V (2021) How does the cam morphology develop in athletes? A systematic review and meta-analysis. Osteoarthritis Cartilage 29:1117–1129

¹ Orthopedic and Trauma Department, Żeromski Specialist Hospital | Kraków, Poland
² SPORTOKLINIK - Orthopedics and Sports Medicine Center | Kraków, Poland
³ Trauma and Orthopedic Surgery Department, Nowy Szpital w Olkuszu | Olkusz, Poland

Interest in unicompartmental knee arthroplasty (UKA) compared to total knee arthroplasty (TKA) is increasing due to several reasons: improved outcomes, less invasive procedure, partial preservation of the joint and better patient satisfaction. This procedure partially preserves the knee joint and in turn maintains the natural joint kinematics and stability leading to a more natural feeling knee after surgery. Historically, one of the contraindications for UKA was anterior cruciate ligament (ACL) tear and anterior instability. However, many surgeons extent their indications to UKA and address anterior knee instability in one procedure. The aforementioned is due to the growing number of young patients with unicompartmental osteoarthritis (UOA), mainly medial osteoarthritis (MOA), who are more physically active, participate in sports and other high-impact activities that can increase the risk of developing knee OA due to knee trauma including ACL tear, meniscal and cartilage injuries.

Management of MOA accompanied by ACL deficiency is a challenging dilemma for orthopedic surgeons. UKA performed in ACL deficient knees shows higher failure rate due to the altered joint kinematics due to recurrent anterior translation of the tibia in relation to the femur, cause higher polyethylene wear and consequent osteolysis due to increased motion of the joint knee, the instability increases also risk of mobile bearing insert luxation [1]. Therefore, various strategies have been proposed including ACL reconstruction (ACLR), high tibial osteotomy (HTO) with or without ACLR, UKA with or without ACLR and TKA. TKA may be an overtreatment strategy if the degenerative changes are restricted solely to the medial compartment due to ACL deficiency or instability. ACLR combined with HTO has been criticized as it shows a threefold higher rate of graft failure compared to UKA [2].

In MOA and ACL-D we can face two potential scenarios. For elderly patients presenting lower activity levels, OA is the primary disease with a concomitant secondary ACL deficiency. For these patients a UKA without ACLR can be considered, respecting couple technical aspects: reduction of the tibial slope and tensioning of the collateral ligaments. Change of the posterior tibial slope contribute to tensioning of the collateral ligaments, its reduction increases collateral ligament tension. It is recommended that the posterior tibial slope should not exceed 7°.

In the second scenario, ACL tear and anterior instability is the primary concern. ACL injury prompts recurrent subluxation of the femur gradually wearing off posteromedial cartilage and medial meniscus, leading to secondary degenerative changes in younger, active patients [3,4]. As ACLR is a frequent, validated procedure leading to complete recovery and return to high level sports and UKA being an established treatment method for medial compartment OA, the combination of both these procedures can be successful [5].

Obtaining good clinical results require proper patient selection, experience in both procedures ACLR and UKA. The ideal patients for the combined procedure include: medial OA (bone-on-bone), correctable intraarticular deformity, presenting with medial pain and instability related to ACL tear, age - less than 65 years of age and non-inflammatory arthropathy. It must be remembered that extra-articular deformities are contraindications to UKA procedure, therefore such cases require possibly HTO or TKA to address the disease. Other contraindications to UKA and ACLR include: other coexisting ligamentous injury PCL, MCL or LCL, varus deformity exceeding 10° or uncorrectable passively deformity on clinical examination and previous HTO procedure.

UKA and ACLR can be performed as a one or two stage procedure. A staged procedure may be elected commencing with ACLR when instability is the main concern, with the UKA performed when pain due to OA arise. UKA and ACLR one-stage procedure is more time consuming and technically demanding, yet requires one procedure and anesthesia, shorter recovery time and reduces social-economic costs. The rehabilitation following UKA-ACLR is more difficult and time consuming.

Surgical technique

The author’s preferred implant is the cementless Oxford prothesis, and the ACL graft is quadruple semitendinosus (ST) tendon autograft and fixed with a dual suspensory graft fixation Authors’ surgical technique: Medial parapatellar approach for UKA is performed with an extended tibial incision for graft harvesting (Pic 1A).

• Semitendinosus tendon (ST) harvested and prepared for the graft, folded into 4 for a single-bundle anatomical ACLR (Pic. 1B).
• The grafted is placed in a vancomycin solution.
• Osteophytes should carefully be removed to prevent ACL impingement that can lead to neoligament failure or an inaccurate tibial bone cut.
• AP cut should be made several millimeters medially from the tibial footprint of the ACL to accommodate acceptable positioning of the ACL tibial tunnel (Pic. 1C).
• Tibial slope should not exceed 7° in order to reduce force in the ACL graft - Standard femoral cuts are performed.
• The femoral tunnel is drilled in anatomical place in an open manner (Pic. 1E).
• Trial components are set and ML stability/ balancing checked.
• The UKA components are implanted.
• The tibial tunnel is prepared as an open procedure using a standard guide (50°-55°), slightly lateral or just next to the tuberosity to avoid medial tibial plateau fracture and impingement on the tibial component of the UKA (Pic. 1F).
• The graft is passed through the previously prepared tunnels and fixed. We use endobutton for femoral and tibial fixation of the graft (Pic. 1G).
• Isometric tensioning must be achieved.
• If performing a cemented UKA: beware of the penetration of cement into the tibial tunnel. A reamer of the same size as the tunnel can be inserted into the tibial tunnel to prevent the cement leaks. Arthroscopic inspection of the tunnel should be performed to detect any excess of cement.

Picture 1: (A-G) Steps in surgical technique UKA and ACLR.

Results

Long-term outcomes after UKA and ACLR are limited. Studies are based on small groups, the materials used are not uniform, and the observations are at medium-term follow-up. However, excellent clinical outcomes have been observed, and clinical improvement was not significantly different compared to the control cohort of patients who underwent UKA with an intact ACL [6, 7]. In all studies, authors express concern about the potential longevity of the results, but it has been reported fixed-bearing medial UKA to have a 96% survivorship at 10 and 91.4% at 14.5 years [8,9].

No significant clinical and radiological differences between mobile and fixed bearing implant designs were found at medium-term follow-up.

Postoperative stiffness, improperly positioned ACL graft tunnels secondary to prosthesis, graft impingement, undersizing of the tibial base plate (to avoid graft impingement), proximal tibia fracture and aseptic loosening of the tibial base plate are the encountered complications [7, 10].

Summary

Treating patients with MOA and ACL-deficient knee is highly demanding. Experience in both UKA and ACL reconstruction procedures is necessary to achieve predictable good outcomes. In older patients above 65 with secondary ACL injury to OA, UKA can be performed without ACL-R by correctly performing the surgical technique while avoiding an increase in posterior slope above 7°. In young patients with OA secondary to ACL injury, UKA and ACLR should be performed. Such procedure should be considered as an alternative to TKA in young and active patients, aiming to preserve knee function and bone stock.

Picture 2: Female patient 55 y. o. UKA and ACLR

Biography
1. Li, Guoan & Papannagari, Ramprasad & DeFrate, Louis & Yoo, Jae & Park, Sang & Gill, Thomas. (2007). The effects of ACL deficiency on mediolateral translation and varus-valgus rotation. Acta orthopaedica. 78. 355-60. 10.1080/17453670710013924.
2. Mancuso, F., Hamilton, T.W., Kumar, V. et al. Clinical outcome after UKA and HTO in ACL deficiency: a systematic review. Knee Surg Sports Traumatol Arthrosc 24, 112–122 (2016). https://doi.org/10.1007/s00167-014-3346-1
3. Pandit H, Beard DJ, Jenkins C, Kimstra Y, Thomas NP, Dodd CA, Murray DW. Combined anterior cruciate reconstruction and Oxford unicompartmental knee arthroplasty. J Bone Joint Surg Br. 2006 Jul;88(7):887-92. doi: 10.1302/0301-620X.88B7.17847. PMID: 16798990
4. Kennedy JA, Molloy J, Mohammad HR, Mellon SJ, Dodd CAF, Murray DW. Mid- to long-term function and implant survival of ACL reconstruction and medial Oxford UKR. Knee. 2019 Aug;26(4):897-904. doi: 10.1016/j.knee.2019.05.009. Epub 2019 Jun 4. PMID: 31174980.
5. Zampogna B, Vasta S, Torre G, et al. Return to Sport After Anterior Cruciate Ligament Reconstruction in a Cohort of Division I NCAA Athletes From a Single Institution. Orthopaedic Journal of Sports Medicine. 2021;9(2). doi:10.1177/2325967120982281
6. Aslan H, Çevik HB. Outcomes of Combined Unicondylar Knee Arthroplasty and Anterior Cruciate Ligament Reconstruction. J Knee Surg. 2022 Aug;35(10):1087-1090. doi: 10.1055/s-0040-1722322. Epub 2021 Feb 5. PMID: 33545722.
7. Foissey C, Batailler C, Shatrov J, Servien E, Lustig S. Is combined robotically assisted unicompartmental knee arthroplasty and anterior cruciate ligament reconstruction a good solution for the young arthritic knee? Int Orthop. 2022 Aug 13. doi: 10.1007/s00264-022-05544-5. Epub ahead of print. PMID: 35962232.
8. Jaber, A., Kim, C., Barié, A. et al. Combined treatment with medial unicompartmental knee arthroplasty and anterior cruciate ligament reconstruction is effective on long-term follow-up. Knee Surg Sports Traumatol Arthrosc (2022). https://doi.org/10.1007/s00167-022-07102-3
9. Plancher KD, Shanmugam JP, Brite JE, Briggs KK, Petterson SC. Relevance of the Tibial Slope on Functional Outcomes in ACL-Deficient and ACL Intact Fixed-Bearing Medial Unicompartmental Knee Arthroplasty. J Arthroplasty. 2021 Sep;36(9):3123-3130. doi: 10.1016/j.arth.2021.04.041. Epub 2021 May 5. PMID: 34053751.
10. Tian S, Wang B, Wang Y, Ha C, Liu L, Sun K. Combined unicompartmental knee arthroplasty and anterior cruciate ligament reconstruction in knees with osteoarthritis and deficient anterior cruciate ligament. BMC Musculoskelet Disord. 2016 Aug 5;17:327. doi: 10.1186/s12891-016-1186-5. PMID: 27496245; PMCID: PMC4974734.

Revision total knee arthroplasty (RTKA) has become an important research subject as total knee arthroplasty (TKA) cases are reported to increase year after year [1]. Currently there is no consensus on the best approach to implanting prosthetic stems in complex RTKA cases. Evidence based medicine approaches are required in order to reach much needed agreement in order to maximize postoperative range of motion, quality of life, bone stock preservation and implant survivorship [2]. This article is an overview on the subject, focusing on the importance of mechanical considerations for successful implantation.

As patients receiving TKA become younger and less tolerant of advanced arthritis and severe loss of function, their expectations following implantation are on par with their functional demands [3]. It is worth mentioning that as younger patients benefit from early implantation, an earlier revision is expected as well. In many studies the mean age for revision is between 60 and 70 years old, but younger age and male gender are consistently at a higher risk of revision across all timeframes [4].

During revision surgery, the decision of whether or not to use a stem is based on the implants need to resist coronal, sagittal and rotational forces. The propensity of such forces developing and leading to instability is based on the type of bone defect identified during surgery. Although significant heterogeneity is seen across studies reporting the type of bone defect encountered, a useful classification system is the Anderson Orthopedic Research Institute (AORI) classification that describes defect extent in both the femur and tibia [5].

Based on defect extent, a comprehensive approach to the use of cement, metal augments, cones and sleeves has been proposed [6]. The use of stems is recommended when rotational instability is of concern and cemented and cementless options are available. While a significant decrease in micromotion is noted when stems are used, the advantage of cementless stem fixation is that prosthesis removal at a later revision will be easier, but end of stem pain and stress shielding are of concern [7]. Cementless stems, on the other hand, are better suited for older patients with osteoporosis and when long-term antibiotic release is considered necessary by the surgeon [8]. Figure 1 represents an overview of our cases in which cementation was performed. A hybrid implantation technique is usually preferred with cementation at the epiphysis and metaphysis region and cementless stem fixation, when needed, in young patients with high functional demand and good bone stock.

Adequate mechanical concepts need to be considered especially when stems are implanted. In our practice we judge implant stability in a top-down approach from femoral and tibial baseplate epiphyseal stability, cones and sleeves metaphyseal stability and diaphyseal stability of stems when decided that they are necessary. Slotted uncemented stems improve rotational stability and when cemented they improve it even further. End of stem pain is a real concern when press-fit uncemented stems are implanted in patients with high functional demands. In such cases conical stems can be considered or the use of a cemented prosthesis [9]. Surgeons should always take stress shielding into consideration as it usually leads to pain and gradual loosening with important bone stock degradation when cementless stems with significant endosteal contact are implanted.

It is worth mentioning that because each revision case is a combination between complex bone defects, patient comorbidities and variable bone stock, no high quality randomized controlled trials have been performed on this subject and the increased heterogeneity of each case makes such a study very difficult to perform. We would like to advocate for a personalized approach in which the surgeon decides each type of implant based on the identified bone defect, the patient’s desired activity level and available bone stock quality.

Figure 1: Sequential targets of bony stability during revision TKA. Color gradient represents the recommended need for cement in order to achieve stability.

In recent years, prosthetic knee surgery has advanced exponentially. Different technologies have been appearing to provide surgeons with better training in their daily practice.

New technologies such as navigation, personalized cutting guides or augmented reality have tried to improve the results for our patients ^(1-3).

However, the appearance of robotics as a tool for the implantation of total knee prosthesis has made the community of orthopaedic surgeons consider it as a weapon to improve the satisfaction of their patients ⁽⁴⁾.

Many of these surgeons see this technology as a copy of navigation and believe that it will be abandoned in the same way. They argue that it is a fad and that the added value that this technology entails is negligible and will not achieve the results that are advertised.

Robotics in prosthetic knee surgery should be understood as an evolution of navigation. The latter gave us the pertinent information to know which was the best position for our implants. However, the execution of the bone cuts was carried out in a conventional manner. Robotics aims to maintain the benefits of navigation, adding to this concept a more precise execution with less aggressiveness and greater safety ⁽⁵⁾.

We must not forget that we are at the beginning of the development of this technology and we must bear in mind that its evolution has enormous potential. Regardless of what robotics has meant for experienced surgeons, the impact that this technology can have on surgeons in training in our hospitals is very important ⁽⁶⁾.

One of the biggest concerns that Teaching Hospitals have is obtaining the key tools to train their residents. That is, how to ensure that these surgeons in training and the fellows understand and learn the basic concepts for pre, intra and postoperative decision-making.

In most hospitals, surgeons instructing residents tried to explain their approach to implantation of a knee replacement. These concepts are often subjective and the surgeon in training must imagine the explanation received. If the student had previously acquired concepts or had a significant capacity for abstraction, the comprehension of the instruction could become good. If the resident did not follow the technical reasoning of the experienced surgeon, the subsequent understanding and reproduction of the procedure was very poor.

Robotics currently allows us to put on a screen what we want to transmit (Figure 1). This represents an advance in the training of our residents from the moment they are visualizing what we explain. The difference with navigation, which also allows us to be more graphic in our teaching, is the possibility of carrying out holistic intraoperative planning prior to bone cuts, understanding the ideal stability and alignment that we want to achieve based on the implant positioning changes made. Not only do they have our explanation, but they also have a very powerful visual element to be able to analyse and understand what is initially subjective and abstract intraoperatively.

We must not forget that the new generations of surgeons in training have an unlimited capacity to interact with new technologies ⁽⁷⁾. If we add tools to the knowledge of experienced surgeons, such as robotics, which allow us to numerically visualize what we are doing, the students (future surgeons) will get more out of their training stage. Even in the future they will take much more advantage of these technological tools, due to their educational immersion living with them.

The learning curve for knee surgeons who want to start using robotic technology is relatively short. This allows us that the training of our residents is not influenced by the lack of attention of the trainers. It also allows the surgeon in training to reproduce a surgery, having understood the basic concepts, with the same precision as the experienced surgeon. In other words, in robotic surgery, the precision of the execution of the bone cuts does not depend on the experience of the surgeon, but on the robotic arm that will always execute the established preoperative plan. Therefore, if the resident learns the key concepts of a surgery in a firm way, the execution will be just as correct ⁽⁸⁾.

Another benefit of robotic surgery is the possibility to discuss preoperative planning with surgeons in training. Some devices have the possibility of carrying out a preoperative study based on computed tomography and the robot's software allows us to analyse preoperatively the possibilities of prosthetic implantation (Figure 2), taking into account the size of the implant, its position and the magnitude of the bone cuts ⁽⁹⁾.

There are also mobile applications (Figure 3) that allow simulating the intraoperative balance to be carried out depending on the situation of laxity or retraction of the ligaments ^{(10, 11)}. Applications on mobile devices can help us perform simulations on fictitious cases and, in this way, train our knowledge to allow greater intraoperative agility.

Probably one of the biggest concerns of orthopaedic surgeons today is to know what is the ideal alignment and perfect stability for our patients, which will lead us to decide what is the correct positioning of the prosthetic components. Many of us, with the entry of robotic surgery in our daily practice, have been able to modify or modulate our concepts that seemed immovable ⁽¹²⁾. We have realized that by seeing, before making the bone cuts, the reality of how to balance and align the operated knee, our old philosophy has changed. Understanding that the tibial cut can perhaps be placed outside 90º to avoid large changes in the femoral cut or that we have much more controlled femoral rotation, are situations that have led us to understand that robotic surgery has come to individualize surgeries for each specific patient.

In this context, if for experienced surgeons this technology represents an element of philosophical rethinking, for surgeons in training it is consolidated as a very powerful tool for new learning and consolidation of basic concepts in prosthetic knee surgery.

There are currently few articles that tell us about the difference in learning between the conventional technique and robotic surgery. It is necessary to carry out future studies that evaluate the knowledge acquired by our residents with these new technologies, comparing these results with the instructional techniques that we have used previously. There are other specialties in which the use of robotics has been consolidated for years, even outside the field of medicine. Educational robotics is an interdisciplinary teaching system that allows students to develop their knowledge and skills. One of the characteristics of robotics is that it is taught through ‘gamification’, that is, turning activity into game ⁽¹³⁾. This makes it possible to assimilate mathematical, physical, mechanical or computer concepts in a fun way and, thus, improve the acquisition of skills that are part of school curricula ⁽¹⁴⁾. Why not assume that in the field of orthopaedic surgery our surgeons in training learn by playing, understanding the game as an easy way to solve the problems that arise in our day-to-day surgeries.

In conclusion, we must be aware that new technologies can not only affect the improvement of the satisfaction rate of our patients, but could be a powerful tool for better education for our residents, and robotics could be very useful for a faster and more efficient learning experience.

Figure 1: The robotic technology screen, as in navigation, allows us to visualize all those changes made in a more understandable way.

Figure 2: Preoperative planning with a personalized ct-scan allows us to guide a specific preoperative planning for that patient.

Affiliation: St. Luke's Hospital Bielsko-Biała, ul. Bystrzańska 94B, 43-309 Bielsko-Biała, Poland

The shoulder arthritis among young (<50 years old) and active patients presents a challenging entity, that possesses unique and gradually more often encountered dilemma for orthopedic surgeons. The reason for this is questionable total arthroplasty implant longevity that remains a concern in more active patients and is a potential threat of reoperation and lifestyle impairment [1].

Omarthrosis as described by Samilson & Prieto is classified into 3 stages depending on humeral head and glenoid osteophyte size as well as joint space narrowing seen on plain radiographs. The well-known classification however does not necessarily correlate with patient’s symptoms such as pain or range of motion limitation which should be surgeons main focus and according to which the treatment option should be chosen [2]. Furthermore, it is also known that among the young the pathogenesis standing behind arthritic changes is much more complex and encompasses such conditions as avascular osteonecrosis, post-traumatic changes or rheumatoid spectrum diseases and this fact may also play role in decision algorithm. Classic degenerative omarthrosis is seen occasionally specifically among heavy weight lifters or manual laborers.

There are multiple non-operative treatment options, that should be gradually applied based on severity of symptoms as to prolong time to more invasive steps. First, physiotherapy as well as kinesiotherapy optimally tailored to patient should find its place. Progressive self-exercise as well as manual therapy with shoulder girdle muscle strengthening and stretching have shown to improve function in a variety of shoulder disorders. Simultaneous oral drugs application, such as Acetaminophen 1g every 3-4 times a day or if non tolerated NSAIDs (Non Steroidal AntiInflammatory Drugs) decrease pain and ease rehabilitation protocol allowing for greater joint mobility in comparison to placebo [2].

If the treatment fails to bring sufficient effect and the patient becomes eventually symptomatic, intraarticular US (UltraSound) guided or blind injections are suggested with comparable results [3]. Despite what has just been said, there is certain controversy about such injections and up to date there are no clear indications on what exactly to inject and which dose to choose. Among available medications, steroids placed into subacromial bursa are best studied, giving improvement in pain management and overall joint function in 12 weeks follow up with risk however to induce partial rotator cuff tears progression into full thickness tears [2].

High molecular weight viscosupplementation is a viable modality as suggested by the AAOS (American Academy of Orthopedic Surgeons) guidelines proving to be successful in pain relief even up to 6 months post injection. They are best known for being safe, generally well-tolerated and most effective in isolated omarthrosis but it is unknown if presence of concomitant intraarticular comorbidities impair the pain-reduction effect [3]. Little evidence is available concerning usage of PRP (Platelet Rich Plasma) or mesenchymal stem cells as non the ideal concentration nor most suitable laboratory kit is known. The authors agree however that PRP application is generally safe and brings scarcely any adverse effects.

Along with joint stiffness and general arthritic progression (Fig. 1) operative treatment comes into play. As originally described by Millett et al. CAM procedure (Comprehensive Arthroscopic Management) is considered [4]. It comprises several procedures that aim to address pain generators in the joint and serves as a bridging treatment before TSA (Total Shoulder Arthroplasty). During the operation a biceps tenodesis, axillary nerve decompression, osteophyte resection (Fig. 2,3) with capsulotomy (Fig. 4,5) and chondral debridement are the key steps. According to the authors careful patient selection with joint space narrowing more than 2 mm, flattening of the humeral head and abnormal posterior glenoid anatomy being failure predictors, the procedure brings favorable clinical outcomes in 92% individuals after 1 year follow up and 63% at 10 year follow up respectively. In addition, CAM procedure does not impact subsequent TSA results if such is undertaken [5].

Some success in delaying the need of TSA has been reported with the use of allograft arthroplasty, which originally intends to separate glenoid from the humeral head adopting anterior capsule, fascia lata, Achilles tendon, lateral meniscus or dermal graft acting as interposition tissues. The durability of such constructs is however questionable. [3]

Apart from palliative approach, there is a group of procedures that aim to repair or restore chondral surfaces inside the joint. To such belong micro fracture technique along with chondral abrasion and drilling on one hand, and ACI (Autologous Chondrocyte Implantation) and OAT (Osteochondral Autograft Transfer) on the other. Reparative methods have shown to be most suitable for small chondral humeral head lesions with fibrin clot based scar tissue formation whereas restorative strategy intends to induce hyaline-like cartilage formation. Best known from good results in the knee joint treatment, the efficacy of such concepts in shoulder joint remains to be further studied. Failure in restoring the joint does not preclude TSA.

If all fails, taking into consideration that TSA in younger patients brings poorer satisfaction score [6], the first line of treatment should be anatomic shoulder arthroplasty which shows higher return to sports and prior activity level rate than hemiarthroplasty or RSA (Reverse Shoulder Arthroplasty).

What future will show remains a mystery but the studies designed through next years should focus around TSA technique and implants improvement to achieve maximal longevity and minimal risk of reoperation, which among the young presents as the ultimate challenge.

Figure 1: Osteoarthrosis of the glenohumeral joint
HH - humeral head
G - glenoid

Figure 2: Inferior osteophyte of the humeral head
IC - inferior capsule
IO - inferior osteophyte of the humeral head

Figure 3: Resection of the inferior osteophyte of the humeral head with the burr
IC - inferior capsule
IO - inferior osteophyte of the humeral head

Figure 4: Anterior capsulotomy of the glenohumeral joint
AL - anterior labrum
SSC - supscapularis muscle
HH - humeral head

Figure 5: Posterior capsulotomy of the glenohumeral joint
PL - posterior labrum
PC - posterior capsule
HH - humeral head

References
[1] Brockmeier SF, Werner BC. Shoulder Arthritis in the Young and Active Patient. Clin Sports Med. 2018 Oct;37(4):xiii-xiv. doi: 10.1016/j.csm.2018.07.001. PMID: 30201176.
[2] Takamura KM, Chen JB, Petrigliano FA. Nonarthroplasty Options for the Athlete or Active Individual with Shoulder Osteoarthritis. Clin Sports Med. 2018 Oct;37(4):517-526. doi: 10.1016/j.csm.2018.05.003. PMID: 30201166.
[3] Jong BY, Goel DP. Biologic Options for Glenohumeral Arthritis. Clin Sports Med. 2018 Oct;37(4):537-548. doi: 10.1016/j.csm.2018.06.001. Epub 2018 Aug 3. PMID: 30201168.
[4] Arner JW, Ruzbarsky JJ, Millett PJ. Comprehensive Arthroscopic Management of Shoulder Arthritis. Arthroscopy. 2022 Apr;38(4):1035-1036. doi: 10.1016/j.arthro.2022.01.033. PMID: 35369910.
[5] Schiffman CJ, Whitson AJ, Chawla SS, Matsen FA 3rd, Hsu JE. Arthroscopic management of glenohumeral arthritis in the young patient does not negatively impact the outcome of subsequent anatomic shoulder arthroplasty. Int Orthop. 2021 Aug;45(8):2071-2079. doi: 10.1007/s00264-021-05133-y. Epub 2021 Jul 13. PMID: 34255098.
[6] Christensen J, Brockmeier S. Total Shoulder Arthroplasty in the Athlete and Active Individual. Clin Sports Med. 2018 Oct;37(4):549-558. doi: 10.1016/j.csm.2018.05.005. PMID: 30201169.

Hospital for Orthopaedic and Trauma Surgery,
Vulpius Klinik GmbH
Bad Rappenau, Germany
Michael.clarius@vulpiusklinik.de

Total knee arthroplasty (TKA) is a very successful operation to cure patients suffering from painful knee arthritis. But despite all the scientific work and increasing surgeons experience of the last decades there is still a significant number of patients not satisfied with the clinical result and performance of their artificial knees. Therefore, numerous investigations are performed to change the position of existing knee designs to a more anatomic position, to change to kinematic or anatomical alignment and to design more anatomic or individual knee implants to address this problem.

However due to artificial knee designs the kinematic of the knee changes after implantation of a total knee not only because surgeons need to resect the anterior cruciate ligament but also because both femoral condyles are centered over the tibial plateau during flexion creating more or less a hinge. Due to a different kinematic of the knee patella problems may occur and especially in patients with a good range of motion preoperatively this may result in a limited range of motion postoperatively. In total knee arthroplasty knee surgeons aim for a balanced knee not only in flexion and extension but also medial and lateral. However due to a different structure and length of the collateral ligaments a balance is very difficult or almost impossible to achieve. New technologies, new measurement tools, gait analysis, navigation and robotics will help to better understand these problems and will probably help to improve clinical results but implantation of a total knee arthroplasty will always be a kind of a compromise concerning kinematics because kinematics of a normal knee is much more complex and not to restore with TKA.

A different approach is whenever possible to replace only destroyed compartments of the knee with unicompartmental knee prothesis and to preserve all the ligaments in its shape and length. The existing bone defect of the damaged knee region is filled with the implant which corrects the deformity of the knee and the leg to a predisease level and restores normal and individual kinematics. This is probably the reason why patients with unicompartmental knee arthroplasties (UKA) report a more “normal” knee, in some cases even a “forgotten” knee, show a higher patient satisfaction rate and a better range of motion compared to patients after total knee arthroplasty (TKA). Other undoubted advantages of UKA compared to TKA are less blood loss, less infections, less severe complications and a shorter rehabilitation.

Due to all these advantages protagonists of this UKA philosophy treat whenever possible their patients with Unis even in severe cases and consider more than 60% of their knee arthritis patients suitable for a medial or lateral Uni knee. In our own institution we performed in 2021 586 medial UKAs, 112 lateral UKAs and 352 TKAs. Why do we see so many indications for Unis? The reason is probably because we look different at our patients. The question is not: Can I do a Uni on this patient? The question is: Do I have to do a TKA in this patient? Routine varus- and valgus-stress x-rays in all patients considered for a knee replacement are very helpful to make and confirm the decision.

The strongest argument against UKA is a higher revision rate reported in all registers. However the German and other registers have shown that with the experience of the surgeon and the institution revision rates can be similar to TKA.

Indications for lateral UKA

10% of all knees considered for a knee replacement are generally suitable for a lateral UKA and show isolated lateral bone on bone arthritis resulting in valgus deformity of the knee. Most of the patients are female. Flexion deformity is less common compared to medial, and hyperextension is sometimes seen. A lot of these patients had open or arthroscopic lateral menisectomy in the past. Patients suffer from pain and their progressing valgus deformity and that their knee feels unstable especially when they climb or walk down the stairs. Cartilage and bone defects are usually located in the center of the tibial plateau and the posterior lateral condyle is also involved. Clinical examination in 30°-40° of flexion under valgus stress reveals crepitation due to bone-on-bone contact indicating severe lateral osteoarthritis.

Radiological diagnosis can sometimes be a challenge because standard a.p. views may look normal. Bone on bone contact is usually seen in 30°-40° of flexion in valgus stress. The Rosenberg view (p.a. standing x-ray in 40° of flexion) is very helpful to demonstrate this. MRI can also confirm the diagnosis of lateral osteoarthritis however the status of the ACL can be misinterpreted due to osteophytes in the notch pretending that the ACL is defect.

Age is no longer considered as a contraindication for UKA [8]. Old age has been proposed as a relative UKA contraindication for a long time. However the literature has shown that patients who underwent UKA compared to TKA showed less blood loss, a decreased infection rate, a shorter length of stay, a reduced complication rate, a faster recovery, a shorter rehabilitation time and a lower morbidity rate in terms of thromboembolic events and major cardiac events as well as a lower mortality rate. Therefore elderly patients seem to be ideal candidates when they meet the indication criteria and should benefit in particular from UKA. Numerous studies have shown that UKA shows excellent results in patients younger than 60. Therefore young age relative to the average age for joint replacement can not be regarded as a contraindication for UKA. In general younger age is associated with a higher risk of revision both for UKA and TKA. Because of the relative youth, the patient is likely to outlive the knee prothesis, UKA is still to be preferred because it is easier to revise than TKA.

Operation technique

Usually, a lateral parapatellar approach is performed. We prefer the operation in a hanging knee position. Incision is slightly longer than in medial UKA because the patella may prevent good access to the lateral compartment and need to be mobilized medially. Lateral osteophytes of the patella need to be removed, in cases of a big and overhanging patella the lateral part of the patella is also resected. After removal of osteophytes we mark the midline of the lateral condyle and move the knee in flexion and extension. Then you can see the individual internal rotation of the tibia in flexion. There is a tendency to place the tibia in external rotation, therefore the tibial sagittal cut is performed through a vertical incision of the patella tendon to address internal rotation of the tibia in flexion. Special lateral tibia designs should be used to allow proper sizing of the tibial component avoiding either undercoverage or overcoverage. Posterior joint line is restored with the femoral component and the knee is balanced in extension. Overcorrection should be avoided as it may result in progression of medial compartment arthritis. Elevation of the joint line can lead to instability, particularly when mobile bearing implants are utilized.

Results

Excellent clinical results and survival data of 92% to 98% or even 100% at a mean of 5 and 12 years are reported in the literature for fixed bearing implants. Such clinical results have also been described by a designer study and an independent multicenter study for mobile bearing lateral unis, however they described an 8,5% dislocation rate at 5 years and a survival of 85% at 5 years.

Summary

Lateral UKA restores the lateral compartment in valgus arthritis, allows for true kinematic alignment and demonstrates excellent functional results and implant survivorship for properly selected patients in experienced hands. 10% of all patients considered for a knee replacement are suitable for a lateral UKA.

Pic 1: Lateral bone on bone arthritis, lateral parapatellar approach

Case 1: Excellent clinical and radiological result 3 years after lateral UKA

 

Case 2: 73y female patient with severe valgus arthritis of the knee, passive correctable valgus deformity in varus stress and the postoperative radiological result

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Case 3: Avascular necrosis of the lateral femoral condyle, a very good indication for a lateral UKA

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References
[1] Argenson JN, Parratte S, Bertani A et al. (2008) Long-term results with a lateral unicondylar replacement. Clin Orthop Relat Res 466:2686-2693
[2] Ashraf T, Newman JH, Evans RL et al. (2002) Lateral unicompartmental knee replacement survivorship and clinical experience over 21 years. J Bone Joint Surg Br 84:1126-1130
[3] Buzin SD, Geller JA, Yoon RS et al. (2021) Lateral unicompartmental knee arthroplasty: A review. World J Orthop 12:197-206
[4] Deroche E, Martres S, Ollivier M et al. (2020) Excellent outcomes for lateral unicompartmental knee arthroplasty: Multicenter 268-case series at 5 to 23 years' follow-up. Orthop Traumatol Surg Res 106:907-913
[5] Ernstbrunner L, Imam MA, Andronic O et al. (2018) Lateral unicompartmental knee replacement: a systematic review of reasons for failure. Int Orthop 42:1827-1833
[6] Excellence NIFHaC (2020) Joint replacement (primary): hip, knee and shoulder. Evidence review for total knee replacement. NICE Guideline NG 157.
[7] Heyse TJ, Tibesku CO (2010) Lateral unicompartmental knee arthroplasty: a review. Arch Orthop Trauma Surg 130:1539-1548
[8] Kennedy JA, Mohammad HR, Mellon SJ et al. (2020) Age stratified, matched comparison of unicompartmental and total knee replacement. The Knee 27:1332-1342
[9] Scott RD (2005) Lateral unicompartmental replacement: a road less traveled. Orthopedics 28:983-984
[10] Smith E, Lee D, Masonis J et al. (2020) Lateral Unicompartmental Knee Arthroplasty. JBJS Rev 8:e0044
[11] Walker T, Zahn N, Bruckner T et al. (2018) Mid-term results of lateral unicondylar mobile bearing knee arthroplasty: a multicentre study of 363 cases. Bone Joint J 100-B:42-49

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* Department for Arthroplasty and General Orthopaedic Surgery, Asklepios Hospital of Orthopaedic Surgery Lindenlohe, Lindenlohe 18, 92421 Schwandorf, Germany
** Department of Orthopedic Surgery and Traumatology; Kantonsspital Baselland; CH-4101 Bruderholz, Switzerland
*** Cardiff & Vale Orthopaedic Centre, University Hospital Llandough, Cardiff, CF64 2XX, UK

Contact address: Prof. Dr. Heiko Graichen
Asklepios Orthopaedic Hospital Lindenlohe, Lindenlohe 18, 92421 Schwandorf, Germany
h.graichen@asklepios.com

Bone defects are present in most Revision-Total Knee Arthroplasties (R-TKA) and additional options for implant fixation are needed as the original fixation zones are compromised. To offload the fixation stress, stems are widely used and have proven to increase longevity, however whether these stems should be cemented or cementless remains debatable ¹ as many individual variables, such as bone quality and geometry, are important factors for fixation.

Morgan-Jones et al. (2015) published on the concept of zonal fixation and described three zones for fixation: epiphysis (zone 1), metaphysis (zone 2) and diaphysis (zone 3). Cementless stems, most commonly used, fix in zone 3 and bypass zone 2. This might explain the reduced long-term survival compared to cemented stems. Another disadvantage of longer cementless stems is stress shielding and proximal bone resorption. This could contribute to reduced long term survival rates of cementless stems especially with bigger bone defects. To overcome this problem, additional fixation in zone 2, the metaphysis, was introduced.

Fixation in the metaphysis can be via either Direct fixation or Indirect fixation. Direct fixation can be cementless using a metaphyseal sleeve. With indirect fixation, the metaphyseal defect is filled with a cone before implant fixation with cement. Indirect fixation reduces defect size and improves cement fixation. The implant is placed independently of the cone. Therefore, the main difference between sleeve and cone is that a cone is not part of the implant, while a sleeve is integral to the implant and directly fixes the implant to the bone.

Metaphyseal fixation with Sleeves

Sleeves are step shaped constructs and are partially of fully porous coated to encourage bone ingrowth. All sleeves are oval, apart from the smallest circular sizes, and provide excellent rotational stability. In this concept, the primary zone for fixation is zone 2 and the stem (zone 3), if necessary is more for alignment. Thus, the problem of diaphyseal offset can be reduced however careful pre-op planning and templating is mandatory. In cases where the stem is the point of primary fixation the sleeve may not integrate and a fatigue fracture between stem and sleeve can be a potential consequence.

Sleeve fixation after 6-12 weeks, with bone ingrowth is solid and long lasting. Various authors ^{3, 4} have described mid-term sleeve survival rates of 97-100% and a recent long-term analysis from B. Bloch et al. (2020) confirmed this excellent survival rate. Tibial sleeves are always combined with a mobile bearing implant. In higher constraint R-TKA constructs the mobile bearing reduces the stress on the implant fixation and this is maybe an additional factor for these superior results. A recent analysis from the NJR showed a 20% reduced revision rate of mobile bearing (sleeve) revision implants compared to non-sleeve, fixed bearing implants. A recent meta-analysis ⁶ showed a loosening rate of 0.4% for sleeves compared to 4.1% for cones, however this difference was not significant. Significant differences were only found for periprosthetic joint infection (PJI), being higher in the cone group. A conclusion for this was not given.

An up-coming strategy of metaphyseal fixation is the one of stemless sleeves. According to the concept from Morgan-Jones et al. (2015) this can be taken as an option if solid zone 1 and 2 fixation can be achieved. Therefore, larger uncontained defects are unsuitable for stemless fixation (Fig. 1). Some studies ^{7, 8} have shown that if the indication is correct, excellent midterm results comparable to stemmed sleeves can be achieved. The advantage of such a concept is that it is more physiological in terms of bone loading, proven in a biomechanical model. ^{9, 10}

Metaphyseal fixation with Cones

One major advantage of cones is that they come in different shapes and can fit almost any defects. However, Fischer et al. (2022) described an increased early complication rate in cones, suggesting that it is technically challenging to implant the cone and implant precisely. The cone can dictate the stem alignment and produce sub-optimal stem positioning. In severe metaphyseal/diaphyseal defects off the shelf cones may remain uncovered in part with reduced indirect fixation. This problem can be solved by custom cone manufacture, offered by some companies. Where huge bone defects are present, cone can be advantageous to use (Fig. 2), while in the great majority of contained and uncontained metaphyseal defects either a sleeve or a cone can be equally effective.

Traditionally cones were made from tantalum though titanium alternatives are available. Most of the published data, however, is on tantalum cones with case series all showing low aseptic loosening rates, comparable with sleeves. ⁶

In daily practice, cones and revision implant should also be planned and templated as the position of the cone is directly affects implant positioning. As with sleeves, bowed tibia and femur can be challenging and may affect stem length. Thinner cemented stems may give more freedom for optimal placement, but when not diaphyseal filling can be malaligned.

As a technical comment, it is possible in off-label use, to combine a cone from one company with an implant from another, as they are not connected to each other.

Revision of Sleeves and Cones

One important aspect of improved fixation is the future ability to remove well-fixed implants. This is challenging for both constructs. While in cones the revision implant itself can be removed relatively easy, removal of the cone itself is often very difficult, if there is direct bone ingrowth and the cortex is thin. Small saw blades and multiple sharp osteotomes and surgeon patience are required to remove the cone without damage. ¹¹

Sleeve removal might also be challenging, in particular in aseptic revision where they are generally still well fixed. Some technical tricks to reduce the challenges have been described by different authors, such as using a 14 mm or thinner stem on the tibia or to disengage the femoral component from the femoral sleeve.^{12, 13} However, with both sleeves and cones, the surgeon must be prepared to perform osteotomies, either tibia crest or a femoral osteotomy to finally remove a well-fixed implant.

Conclusion

The concept of metaphyseal fixation has changed RTKA dramatically. Fixation in the metaphysis has improved long term survival rates even in the presence of bigger bone defects. Both sleeves and cones have demonstrated similar, low rates for aseptic loosening. Consequently, personal experience is an important factor when it comes to the decision whether to use a sleeve or a cone, because both implants need meticulous planning and a robust surgical technique that assures alignment and proper placement. Overall, both implants solve the same problem with similar good results, though via different concepts.

Figure 1: R-TKA performed with a cementless metaphyseal sleeve fixation on the tibia. Additional stem was used as zone 1 was severely compromised in that uncontained medial defect. Zone 2 and 3 fixation was achieved on the tibia.

Figure 2: R-TKA performed with cones on both sides to reduce defect size. Implant itself was fixed with cement in zone 2 and 3.

References
[1] Beckmann J, Luring C, Springorum R, Kock FX, Grifka J, Tingart M. Fixation of revision TKA: a review of the literature . Knee Surg Sports Traumatol Arthrosc. 2011;19(6):872–9
[2] Morgan-Jones R, Oussedik SI, Graichen H, Haddad FS. Zonal fixation in revision total knee arthroplasty. .Bone Joint J. 2015 Feb;97-B(2):147-9.
[3] Graichen H, Scior W, Strauch M.Direct, Cementless, Metaphyseal Fixation in Knee Revision Arthroplasty With Sleeves-Short-Term Results. J Arthroplasty. 2015 Dec;30(12):2256-9.
[4] Martin-Hernandez C, Floria-Arnal LJ, Muniesa-Herrero MP, Espallargas-Doñate T, Blanco-Llorca JA, Guillen-Soriano M, Ranera-Garcia M. Mid-term results for metaphyseal sleeves in revision knee surgery. Knee Surg Sports Traumatol Arthrosc. 2017 Dec;25(12):3779-3785 Knee Surg Sports Traumatol Arthrosc. 2021 Aug 20. doi: 10.1007/s00167-021-06691-9
[5] Benjamin V Bloch ¹, Odei A Shannak ², Jeya Palan ³, Jonathan R A Phillips ⁴, Peter J James. Metaphyseal Sleeves in Revision Total Knee Arthroplasty Provide Reliable Fixation and Excellent Medium to Long-Term Implant Survivorship. J Arthroplasty 2020 Feb;35(2):495-499.
[6] Fischer LT, Heinecke M, Röhner E, Schlattmann P, MAtziolis G. Cones and sleeves present good survival and clinical outcome in revision total knee arthroplasty: a meta-analysis. Knee Surg Sports Traumatol Arthrosc. 2022; 30: 2824 – 37
[7] Stefani G, Mattiuzzo V, Prestini G. Revision Total Knee Arthroplasty with Metaphyseal Sleeves without Stem: Short-Term Results. Joints. 2017 Oct 30;5(4):207-211.
[8] Scior W, Chanda D, Graichen H. Are stems redundant in times of metaphyseal sleeve fixation? J Arthroplasty. 2019 Oct;34(10):2444-2448
[9] Nadorf J, Gantz S, Kohl K, Kretzer JP Tibial revision knee arthroplasty: influence of modular stems on implant fixation and bone flexibility in AORI Type T2a defects. .Int J Artif Organs. 2016 Nov 29;39(10):534-540
[10] Nadorf J, Kinkel S, Gantz S, Jakubowitz E, Kretzer JP. Tibial revision knee arthroplasty with metaphyseal sleeves: The effect of stems on implant fixation and bone flexibility. PLoS One. 2017 May 8;12(5):e0177285
[11] Scully WF, Deren ME, Sultan AA, Samue LT, Nageotte W, Molloy RM, Krebs VE. Removal of Well-Fixed Tibial Cone in Revision Total Knee Arthroplasty-A Uniquely Challenging Yet Necessary Scenario J Knee Surg. 2019 Nov 4
[12] Martin JR, Watters TS, Levy DL, Jennings JM, Dennis DA. Removing a well-fixed femoral sleeve during revision total knee arthroplasty. Arthroplast Today. 2016 Jul 2;2(4):171-175.
[13] Lekkreusuwan K, Scior W, Graichen H. TKA-Revision with maintenance of well-fixed metaphyseal sleeves: Indications and surgical technique. J Orthop. 2020 Dec 28;23:13-17

Ankle stabilisation procedures represent an established surgical option for patients suffering from chronic ankle instability (CAI) not responding to conservative treatment. In recent times we have witnessed the development of the arthroscopic approach to CAI, mirroring what already happened in the shoulder and knee joints, where original open stabilisation techniques have progressively been replaced by all arthroscopic procedures (fig 1) [1]. The arthroscopic visualization of the ankle ligamentous structures has permitted a novel insight of the posttraumatic consequences of ankle injuries, sustaining the description of new clinical entities and therapeutic strategies. The concept of microinstability associated to the isolated injury of the superior fascicle of the anterior talofibular ligament (fig 2) and the renewed interest in the clinical role of the medial ligamentous complex are clear examples of the impulse given by the arthroscopic approach to ankle instability [2,3].

Fig. 1: The arthroscopic repair of the lateral ankle ligamentous complex (right ankle, 30° scope in the antero-medial portal). ATFL: Anterior Talo Fibular Ligament. LM: Lateral Malleolus

Fig. 2: Arthroscopic evaution of the lateral ankle ligamentous complex (right ankle, 70° scope in the antero-medial portal). ATFL: Anterior Talo Fibular Ligament. LM: Lateral Malleolus. Ta: Talus. The red arrow shows an avulsion of the upper part of the ATFL. The blue arrows indicate the talar insertion of the ATFL

Like in any field of the medical practice, a solid scientific support is required to promote the use of new therapeutic strategies in the daily practice. For this purpose, the definition of proper outcome tools is of primary importance both for the researcher to produce relevant data and the clinician to critically appraise the increasing amount of literature dealing with ankle instability treatment.

It has long been recognised that the direct patient’s perspective on their experiences with treatment, through the use of the patient-reported outcome measures (PROMs), is the best evidence to evaluate the effectiveness of a clinical intervention. The PROMs are considered appropriate in assessing the therapeutic outcome if they are psychometrically sound, meaning that they have shown to be valid, reliable and responsive in the specific population affected by the disease of interest [4]. Said in more clinician-friendly terms any outcome scale produces information relevant to the daily practice at the extent to which it has been proven capable to measure the pathology it is purported to measure and the eventual modification in the patient’s state after the treatment.

With this premise in mind, Spennacchio et al recently systematically analysed 15 years of CAI surgery literature to furnish an updated overview of the evaluation modalities chosen by researchers, aiming to depict current criticalities worthy of further improvement [5]. The results of the review highlight that the PROM’s selection is not always concordant with the best available evidence. Only a minor part of the researchers selects outcome scales with proofs of validation in the specific CAI population, namely the Karlsson score, the Foot and Ankle Ability Measure (FAAM) and the Foot and Ankle Outcome Score (FAOS) [6,7]. The AOFAS ankle/hindfoot scale [8] resulted the most frequently reported outcome score across the 104 included studies. This clinician-based score, has never been evaluated for validity and reliability in the assessment of ankle instability. The little emphasis on joint stability symptoms, makes it possible to rate the maximum score even in the event of a postoperative persistent subjective feeling of instability [9]. AOFAS outcome data may therefore fail to describe the clinical state of the CAI patient suggesting greater postoperative success than justified, which might contribute to promote inappropriate clinical practices. However, the historical unsupported common use of the scale, seems to represent a strong evidence since recent consensus statements keep on recommending its use to evaluate the results of CAI surgical treatment [10].

Another critical point highlighted by the review relates to the preoperative diagnostic criteria leading to an ankle stabilisation procedure. Researchers define ankle instability in a varied manner, using heterogeneous combinations of patient’s history, subjective symptoms, physical examination signs and imaging investigations. It appears that the common point across the reports is the stabilisation procedure itself rather than the treated disease, with subsequent negative impact on the external validity of the reported findings and a reliable comparison across studies. The need for a standardized patient’s selection is particularly topical in the light of the recent advances in the ankle instability field. An agreed definition of the emerging diagnostic hypothesis, such as the mentioned microinstability, is the first desirable step to produce the evidence required to support their clinical relevance.

In an attempt to increase the quality of the research on ankle instability the International Ankle Consortium proposed in 2014 some criteria to define a more homogeneous cohorts of patients to be enrolled in CAI clinical trials [11]. As a matter of fact, the initiative has so far been unreasonably ignored by most researchers dealing with ankle instability.

As recently reiterated by the experts we are in the middle of an ankle arthroscopic wave characterised by a renewed interest on ankle stabilisation procedures with the exciting potential to increase the quality of the clinical practice [12]. For this to become real it is of utmost importance that the scientific community dedicate future efforts to further standardize the selection of CAI patients in the research setting and promote the use of appropriate evaluation modalities for the proposed therapeutic strategies.

These are essential steps to improve the evidence necessary to recognize the real advances and keep on providing our patients suffering from ankle instability with the best possible practice.

¹Department of Orthopaedics, Cork University Hospital.

The traditional gold standard treatment for bicompartmental or tricompartmental knee arthritis is total knee arthroplasty (TKA). Partial knee arthroplasty (PKA), unicompartmental knee arthroplasty (UKA) or patellofemoral joint (PFJ) arthroplasty, procedures have increased in recent times due to reported improving survivorship rates, superior patient reported outcome measures (PROMS), faster recovery and reduced perioperative complications. There is also an increasing focus in providing patient specific procedures together with preservation of the cruciate ligaments in knee arthroplasty so as to maintain normal knee kinematics. Bicompartmental knee arthroplasty (BCA), also known as combined partial knee arthroplasty (CPKA) has been gaining interest due to improved implant design with better clinical outcomes and survival rates. The benefits of BCA include preservation of cruciate ligaments, bone conservation, restoring isokinetic quadriceps function, preserving extensor efficiency and improved anterior-posterior stability compared with TKA. Walking speed has also been shown to be improved in BCA compared to TKA, with an improvement in walking speed associated with an increased life expectancy [1].

Primary BCA

BCA can either be primary BCA (simultaneous) or conversion from UKA to BCA. A recent systematic review found only 17% of patients with knee OA had tricompartmental disease [2]. BCA may provide a potential alternative treatment option in those with bi-compartmental disease (medial and lateral, lateral and patellofemoral, medial and patellofemoral arthritis). Medial tibiofemoral arthritis and PFJ arthritis is the most common combination of bicompartmental arthritis and the most commonly performed BCA [2] Garner et al recently developed a classification for CPKA, bi-unicondylar arthroplasty (Bi-UKA), medial bicompartmental arthroplasty (BCA-M), lateral bicompartmental arthroplasty (BCA-L) (Fig. 1, 2) [3, 4]. BCA at present make up <0.1% (586 procedures) of all knee arthoplasty procedures in the UK NJR, with 10 year survival of 85.9% [5]. Schrednitzki et al. performed a randomised controlled trial comparing BCA (unlinked modular UKA and PFJ) to TKR (37 vs. 38 patients) and at five years no significant difference was found in PROMS scores [6]. However, they did report significant improvement in ROM in the BCA at 1, 2 and five years. Initial BCAs utilised a linked monolithic prosthesis which was associated with higher complication and revision rates. These were attributed to the difficulties with sizing and positioning of the femoral component as well as cases of tibial subsidence and tibial tray fracture which ultimately led to the recall of the Journey Deuce prosthesis (Smith and Nephew Inc., Memphis, TN, US) by the US Food and Drug administration in 2010. To address the problems associated with the linked implants providers are now providing 3D printed customised patient specific instrumentation and implants. This has improved results with a small number of studies showing satisfactory outcomes in the medium term. However, a recent systematic review including analysis on customised BCA concluded that insufficient evidence existed on the benefits of such implants at present. The addition of navigation and robotic assistance may help improve the alignment and positioning of such implants however greater work is needed in this area. Given the poor results of the initial linked components more surgeons have begun utilising unliked implants allowing them to customise the prosthesis to the anatomy of the specific patient. A study by Rossi et al of 57 BCA with a mean follow up of 9 years reported a survival rate of 91.5% at 10 years [7]. Robotic assisted technology is gaining popularity and a study by Gaudini et al examining Robotic assisted BCA of 57 patients reported excellent functional outcomes and a survival of 93% at 7 years [8]. More recently Blyth et al performed a RCT comparing robotic assisted BCA (bi-unicompartmental) with mechanically aligned TKA and found no significant difference in PROMS at one year [9]. The challenges with BCA to date are that the cohorts are small in size with medium term outcomes reported.

Conversion of UKA to BCA

Progression of arthritis is the most common reason for revision of UKAs. Due to changing patient demographics and patient demands, a greater number of UKA are being performed in younger patients. There is a cumulative revision rate of 17.5% at 17 years in UKA, with the highest revision amongst patients <55 years [5]. This leads to debate about the appropriate steps in managing disease progression in such patients. The majority of UKA undergo conversion to TKA however this is not without its challenges with the potential need for augments, stems and increased levels of constraint. BCA offers an alternative conversion option with retention of the well-functioning UKA and targeted treatment of the new diseased compartment. A small number of studies have shown satisfactory outcomes in the medium and some in the longer term. A recent study by Garner et al comparing 23 patients who underwent conversion of a UKA to BCA to 22 matched TKA patients found increased walking speed and increased step length in BCA [4]. This study also reported an improved Oxford Knee Score in BCA compared with TKA patients. Similarly, a study by Pritchett comparing PROMs and patient satisfaction in UKA converted to BCA or TKA (73 patients vs. 75 patients) found improved PROM, patient satisfaction and reduced complications in those converted from UKA to BCA. Pritchett reported only one revision from BCA to TKA (mean follow up of 14 years) [10]. These findings were mirrored by Haffer et al with similar survivorship but greater improvement in functional outcomes in conversion of UKA to BCA, than UKA to TKA [11]. However, concerns exist in conversion of UKA to BCA including balancing the knee, subsidence, loosening, and disease progression. Also, it must be recognised that not all patients are suitable for conversion of a UKA to a BCA such in those patients with raised BMI and multiple medical comorbidities. Rates of re-revision in UKA-BCA vary with some papers reporting rates of 17% compared to 7% in UKA-TKA [10].

There may be a role for BCA as an alternative treatment option for bicompartmental OA in a certain subset of younger patients with a desire to a faster recovery, preserve normal knee kinematics and stave off a TKR. However, this procedure is technically demanding, and the surgeon should be a high-volume practitioner, proficient in performing UKA and PFJ arthroplasty. Patient specific instrumentation and robotic assisted technology are considerations for the future and may have a greater part to play in addressing some of the difficulties encountered with the positioning, sizing and alignment of the initial BCA implants. Patients should be counselled about the potential benefits of the procedure but also the risks including re-revision. Larger studies with long term follow up are needed to understand the survival of BCA as well as more detailed analysis to help identify what patients may benefit most from BCA but also those patients in whom BCA should be avoided.

Figure 1: Classification of combined partial knee arthoplasty. Garner et al [3,4]

Figure 2: Radiographic examples of partial knee arthroplasty (PKA) procedures revised to combined partial knee arthroplasty (CPKA) for native compartment degeneration, using a compartmental approach. Medial unicompartmental arthroplasty (UKA-M), lateral unicom- partmental arthroplasty (UKA-L), patellofemoral arthroplasty (PFA), medial bicompartmental arthroplasty (BCA-M), lateral bicompart- mental arthroplasty (BCA-L), bi-unicondylar arthroplasty (Bi-UKA). Garner et al [4]

References
[1] Garner AJ, Dandridge OW, van Arkel RJ, Cobb JP. Medial bicompartmental arthroplasty patients display more normal gait and improved satisfaction, compared to matched total knee arthroplasty patients. Knee Surg Sports Traumatol Arthrosc. 2021 Oct 23. doi: 10.1007/s00167-021-06773-8
[2] Stoddart JC, Dandridge O, Garner A, Cobb J, van Arkel RJ. The compartmental distribution of knee osteoarthritis - a systematic review and meta-analysis. Osteoarthritis Cartilage. 2021;29(4):445-455
[3] Garner A, van Arkel RJ, Cobb J. Classification of combined partial knee arthroplasty. Bone Joint J. 2019;101-B(8):922-928
[4] Garner AJ, Dandridge OW, van Arkel RJ, Cobb JP. The compartmental approach to revision of partial knee arthroplasty results in nearer-normal gait and improved patient reported outcomes compared to total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc. 2021 Aug 20. doi: 10.1007/s00167-021-06691-9
[5] National Joint Registry UK. NJR 18th Annual Report 2021.pdf [Internet]. [accessed 18.07.22].
[6] Schrednitzki D, Beier A, Marx A, Halder AM. No Major Functional Benefit After Bicompartmental Knee Arthroplasty Compared to Total Knee Arthroplasty at 5-Year Follow-Up. J Arthroplasty. 2020;35(12):3587-3593
[7] Rossi SMP, Perticarini L, Clocchiatti S, Ghiara M, Benazzo F. Mid- to long-term follow-up of combined small implants. Bone Joint J. 2021;103-B(5):840-845
[8] Gaudiani MA, Samuel LT, Diana JN, DeBattista JL, Coon TM, Moore RE, Kamath AF. Robotic-arm assisted bicompartmental knee arthroplasty: Durable results up to 7-year follow-up. Int J Med Robot. 2022;18(1):e2338
[9] Blyth MJG, Banger MS, Doonan J, Jones BG, MacLean AD, Rowe PJ. Early outcomes after robotic arm-assisted bi-unicompartmental knee arthroplasty compared with total knee arthroplasty: a prospective, randomized controlled trial. Bone Joint J. 2021;103-B(10):1561-1570.
[10] Pritchett JW. Disease Progression After Unicompartmental Arthroplasty: Add a Compartment or Revise to Total Knee Arthroplasty? J Arthroplasty. 2022 May 4:S0883-5403(22)00512-5. doi: 10.1016/j.arth.2022.04.044
[11] Haffar A, Krueger CA, Marullo M, Banerjee S, Dobelle E, Argenson JN, Sprenzel JF, Berger RA, Romagnoli S, Lonner JH. Staged BiCompartmental Knee Arthroplasty has Greater Functional Improvement, but Equivalent Midterm Survivorship, as Revision TKA for Progressive Osteoarthritis After Partial Knee Arthroplasty. J Arthroplasty. 2022;37(7):1260-1265

¹ 401 Military Hospital of Athens, Athens, Greece
² Bioclinic of Athens, Athens, Greece
³ D Group Educational Center, Athens, Greece

Virtual Reality is a technology developed mainly by the video games industry. With the aid of special equipment, the user can isolate himself from the real environment and get into a "virtual" world, living an unprecedented experience.

Gradually the medical community, realizing the advantages of this new technology, started to develop applications for the training of young doctors. Orthopedics is one of the medical specialties that virtual reality tools can contribute substantially to the training of surgeons.

However, there are still questions to be answered:

• What is the level of this technology nowadays, and how can we use it?
• What is the effectiveness of these simulators in orthopedic training?

Traditional training methods in Orthopedic specialty

1. The primary training method of a resident is in the operating room during live surgery. Of course, it is the most realistic way of training, where the resident can operate under the supervision of an experienced surgeon with all the difficulties and tips and tricks that might come up. Nevertheless, this way of training creates much stress for both the trainer and the trainee and raises many ethical and safety issues for the patient.

2. Training in sawbones is another typical method. However, their availability is a law, their cost is high, and they do not offer actual operative room conditions.

3. Wet labs and training on cadavers are one more popular training methods in Orthopedics. Young surgeons compete to participate in numerous courses around the world. However, still, the availability of corpses remains low. Too often, they are characterized by poor quality, and trainees can practice only once while there are two or more over a specimen. To all the above, we must also add the high cost, the ethical issues, and the possibility of disease transmission.

Virtual Reality as a training method

Using virtual reality technology can avoid many of the above disadvantages, and the patient's safety is secured. The surgeon can perform an operation with or without guidance, without time or place limitations, quantify his results, and see his improvement. He can also repeat a procedure as often as he wants, choose between different scenarios with varying degrees of difficulty and teach himself without cost to the patient. Even experienced surgeons may prepare themselves before a high-demand, rare operation. Finally, the software offers the opportunity to cooperate with multiple surgeons worldwide.

Virtual Reality orthopedic training in literature

Many studies have been published on virtual reality methods for specific orthopedic surgical training.

In total hip arthroplasty, virtual Reality did not affect medical knowledge but significantly improved surgical skills, according to J. Hooper, E. Tsiridis, et al.³

In cervical pedicle screw placement during virtual reality training, the screws were in a good position in 100% of cases, and penetration of the pedicle wall was 10%. In cadavers, the percentages were 62,5% and 50%, respectively⁴. Likewise, Gasco et al.² demonstrated that even one virtual reality system could reduce the mistakes by 53% in lumbar pedicle screw placement.

In addition, the basic arthroscopic skills and autonomy of the residents seem to get improved after the training in 3D virtual environment⁶. However, most of the published studies are referred to arthroscopy training.

Finally, Clarke et al.¹, in a review of 2021, included 16 studies with a total of 431 trainees with virtual reality systems and measured 47 outcomes. They conclude that virtual Reality presents an immersive new simulation technology improving the users' technical skills exponentially. However, more studies are needed to prove the positive effects of this new tool in orthopedic surgery training.

Virtual Reality orthopedic training in Shoulder Surgery

D. Goel and G. Athwal from Canada reported up to a 570% decrease in the glenoid approach learning time when the trainee had used the software 3 to 5 times. In addition, the technical and nontechnical skills of participants were improved by 387% ⁵ (Figure 1)

Figure 1: Glenoid approach using virtual reality software

In Greece, our team carried out our first virtual reality course where the participants had the opportunity to train in reverse shoulder arthroplasty. Five young surgeons with no more than 3 years experience and eight residents (2^nd to 6 ^th year) trained for 4-5 hours each (Figure 2, 3). Furthermore, 54% of them were somewhat familiar with the shoulder surgical approaches, 55% were not or not very familiar with RSA and 75% of them has never been a primary surgeon. Regarding the VR experience, 76,9% never used a headset generally and none for surgery training.

Figure 2: Training of a young resident in the anatomy of the shoulder

Figure 3: Training of a young surgeon in placement of the reverse shoulder arthroplasty

The mean adaptation time of the participants in the virtual environment was 2-3 minutes. They all characterized their experience as immersive, and it was easy for them to understand the anatomy and the procedure. Finally, after assessing the metrics, 100% placed the first glenoid guide in a proper position after a mean of 4.1 attempts (Figure 4).

Figure 4: Baseplate placement assessment

After the training program approximately 70% of the participants felt certain for several technical steps to perform correctly an RSA and 80% to convince a consultant shoulder surgeon that they were competent if viewed. However, none of them felt extremely confident to completely perform an RSA as primary surgeon.

In conclusion, virtual reality systems may not develop alone a complete surgeon. Moreover, drawbacks like high cost, low availability and the lack of haptic feedback to recreate the sense of touch or motion restrict VR systems from broad use. However, it can be an immersive, safe, and reliable adjunct to a comprehensive education program focused on improving patient care.

The CEO of the VR software that we used (Precision OS) states:

"Surgical education is ready for disruptive technology to enhance skill acquisition while connecting surgeons to each other with no patient harm. As we continue to use virtual Reality in education, expertise will increase, and patient care will improve worldwide." (Figure 5)

Figure 5: Simultaneous training of multiple surgeons in a virtual environment

Biography
1. Clarke E. Virtual reality simulation-the future of orthopaedic training? A systematic review and narrative analysis. Adv Simul (Lond). 2021 Jan 13;6(1):2. doi:10.1186/s41077-020-00153-x
2. Gasco J, Patel A, Ortega-Barnett J, Branch D, Desai S, Kuo YF, et al. Virtual reality spine surgery simulation: an empirical study of its usefulness. Neurol Res. 2014 Nov;36(11):968–973. doi:10.1179/1743132814Y.0000000388
3. Hooper J, Tsiridis E, Feng JE, Schwarzkopf R, Waren D, Long WJ, et al. Virtual Reality Simulation Facilitates Resident Training in Total Hip Arthroplasty: A Randomized Controlled Trial. J Arthroplasty. 2019 Oct;34(10):2278–2283. doi:10.1016/j.arth.2019.04.002
4. Hou Y, Shi J, Lin Y, Chen H, Yuan W. Virtual surgery simulation versus traditional approaches in the training of residents in cervical pedicle screw placement. Arch Orthop Trauma Surg. 2018 Jun;138(6):777–782. doi:10.1007/s00402-018-2906-0
5. Lohre R, Bois AJ, Athwal GS, Goel DP, Canadian Shoulder and Elbow Society (CSES). Improved Complex Skill Acquisition by Immersive Virtual Reality Training: A Randomized Controlled Trial. J Bone Joint Surg Am. 2020 Mar 18;102(6):e26. doi:10.2106/JBJS.19.00982
6. Walbron P, Common H, Thomazeau H, Hosseini K, Peduzzi L, Bulaid Y, Sirveaux F. Virtual Reality simulator improves the acquisition of basic arthroscopy skills in first-year orthopedic surgery residents. Orthop Traumatol Surg Res. 2020 Jun;106(4):717-724. doi:10.1016/j.otsr.2020.03.009.