Introduction

The ESSKA-EKA course, held from 20-21 September 2024 in Cologne, Germany, was a resounding success, bringing together a dedicated group of orthopaedic surgeons and medical professionals from 14 different nations. Hosted at the state-of-the-art CADLAB in Cologne, the event provided participants with an unparalleled opportunity to engage in both theoretical discussions and practical exercises on deformities around the knee, osteotomies, and joint preservation.

Objectives

The course's main objective was to present a detailed view on knee deformities while addressing the complex interplay between soft tissues, bony structures, and all planes of the leg. Participants delved into the practical and theoretical aspects required to excel in treating both constitutional and post-traumatic deformities, as well as degenerative knee conditions. The course also prepared surgeons for the osteotomy certification module, a valuable milestone for orthopaedic specialists.

Chairs

Special thanks go out to our Course Chairs Dr. Raghbir Khakha and Prof. Dr. Steffen Schröter. Because of your dedication, attendees were immersed in key concepts such as frontal, sagittal, and axial plane alignment, correction planning, and cutting-edge surgical techniques. A highlight of the course was the hands-on cadaveric sessions, where participants performed relevant approaches to knee osteotomies, offering a tangible application of the lessons learned.

“The osteotomy focus group of the EKA and the group of the ESSKA Osteotomy Certification group organized an osteotomy cadaver course in the CADLAB in Cologne. Attendees came from 14 different countries - the spirit of ESSKA-EKA was always present. The amazing environment gave the attendees and faculty the opportunity to discuss indication, treatment and planning. All had the opportunity to train planning and perform the surgeries at the cadaver under guidance of the faculty.” - Steffen Schröter

Faculty

The international faculty, consisting of experts like Dr. med. Vlad Predescu and Dr. med. Silvio Villascusa, alongside Assoc. Professor Hiroshi Nakayama, brought diverse perspectives on osteotomies and joint preservation, enriching the discussion with insights from various clinical backgrounds. Their technical pearls and in-depth knowledge of the latest advancements in implants and instrumentation proved invaluable to all attendees.

Conclusions

With 17 participants and an intimate faculty-to-student ratio, the atmosphere was conducive to personalized learning and interaction. The course not only emphasized the importance of detailed preoperative planning but also shed light on the relevance of deformity correction in treating knee osteoarthritis and patellofemoral disease. Overall, the ESSKA-EKA course was a remarkable opportunity for participants to refine their skills in knee deformity correction, preparing them for the challenges they will face in clinical practice. With the next generation of knee preservation techniques at their fingertips, the surgeons who attended this course are now better equipped to handle complex knee conditions with precision and confidence.

To apply for one of our upcoming Courses, Certification Modules or Fellowships, visit our Education Hub here!

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.

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
1. Dominici M, Le Blanc K, Mueller I, et al. Minimal criteria for defining multipotent mesenchymal stromal cells. The International Society for Cellular Therapy position statement. Cytotherapy 2006;8:315-7.
2. Boada-Pladellorens A, Avellanet M, Pages-Bolibar E, Veiga A. Stromal vascular fraction therapy for knee osteoarthritis: a systematic review. Ther Adv Musculoskelet Dis 2022;14:1759720X221117879.
3. Andia I, Maffulli N, Burgos-Alonso N. Stromal vascular fraction technologies and clinical applications. Expert Opin Biol Ther 2019;19:1289-305.
4. Fortier LA, Potter HG, Rickey EJ, et al. Concentrated bone marrow aspirate improves full-thickness cartilage repair compared with microfracture in the equine model. J Bone Joint Surg Am 2010;92:1927-37.
5. Oliver KS, Bayes M, Crane D, Pathikonda C. Clinical outcome of bone marrow concentrate in knee osteoarthritis. J Prolotherapy 2015;7:937-46.
6. Kim KI, Kim MS, Kim JH. Intra-articular Injection of Autologous Adipose-Derived Stem Cells or Stromal Vascular Fractions: Are They Effective for Patients With Knee Osteoarthritis? A Systematic Review With Meta-analysis of Randomized Controlled Trials. Am J Sports Med 2023;51:837-48.
7. Chahla J, Mannava S, Cinque ME, Geeslin AG, Codina D, LaPrade RF. Bone Marrow Aspirate Concentrate Harvesting and Processing Technique. Arthrosc Tech 2017;6:e441-e5.
8. Cavallo C, Boffa A, Andriolo L, et al. Bone marrow concentrate injections for the treatment of osteoarthritis: evidence from preclinical findings to the clinical application. Int Orthop 2021;45:525-38.
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.

International Knee Course 2022 in Tg. Mures, Romania; From left to right: Mihai Roman, Vlad Predescu, Reha Tandogan, Radu Prejbeanu, Juan Carlos Monllau, Tiberiu Bățaga, Radu Fleacă, Octav Russu

Tiberiu "Tibi" Bataga left us on 19 August 2023, following on from a serious heart problem.

Standing alongside him for all my Orthopaedic years, he was a real friend, an outstanding mentor and a true Orthopaedic professional. He was only 63 years old and he left his dear wife Simona, his daughter Cristina, his son-in-law Rene and his precious nephew Marc Alexander for which he was very proud of.

He was one of the pioneers in arthroscopy in Romania, one of the youngest Professors of Orthopaedics in Romania at GE Palade University of Medicine, Pharmacy, Science and Technology of Targu Mures, a former President of the Romanian Society of Orthopedics and Traumatology, and a Founder of the Romanian Society of Arthroscopy and Sports Traumatology . He was always was a finder of new ways and solutions in modern Orthopaedics, constantly with his patients in mind. Not only an exceptional surgeon,  he was also a true inspiration for the young ones, students and residents, in an enthusiastic manner. Member of ESSKA, EKA, ISAKOS and many other international Orthopaedic societies, with countless presentations on international podiums, he also organised an excellent Romanian course, the International Knee Course, which reached his 7^th edition, with ESSKA patronage, in Targu Mures.

We all had the opportunity of meeting him all over the world, at congresses and other events, and we will remember his laughter, his friendship, and his joy of life.

Farewell, Tibi…

On behalf of ESSKA-EKA,
Octav Russu
Targu Mures, 19 August 2023

EKA Meeting 2019 in Bucharest, Romania; From left to right: Mihai Roman, Radu Prejbeanu, Octav Russu, Ionuț Codorean, Kristian Kley, Nanne Kort, Tiberiu Bățaga, Vlad Predescu, Oliver Djahani, Rodica Marinescu, Vlad Georgeanu, Radu Fleaca

The 5^th ESSKA-EKA All About Total Knee Course was held in Istanbul on 23-24 June 2023. The course took place in the state-of-the-art Koç University RMK-AIMES venue. This multi-specialty training centre houses eight fully equipped operating theatres, five robotic arthroplasty systems, advanced imaging equipment and animal labs. The course was accredited by the European Accreditation Council for Continuing Medical Education (EACCME^®) with ten European CME credits (ECMEC^®s).

The course was fully booked six months in advance, underscoring the popularity and the demand for this event.

RMK-AIMES Surgical Training Center of Koç University, sawbone setup & lecture hall

Faculty

The international faculty consisted of Reha Tandogan (Course Chairman, EKA Chair), Bruno Violante (Vice President of European Knee Associates (EKA)), Guillaume Demey (EKA Board member), Daniel Perez-Prieto (EKA Board member), Alan Ivkovic (EKA Board member), James Harty (EKA member), Mustafa Karahan (former ESSKA Board Member), Baris Kocaoglu (ESSKA Board Member, ESSKA Academy). Local faculty included Burak Beksac, Alper Kaya, Gokhan Meric, Ersin Ercin, Gokhan Kaynak, Sarper Gursu, Tahsin Beyzadeoglu; all academic orthopedic surgeons in teaching hospitals with associate professor degree or higher, and most of them ESSKA or EKA members.

ESSKA-EKA Faculty during discussion

Delegates & Programme

The All About Total Knee Arthroplasty Course is a comprehensive 1.5-day course covering principles and techniques of knee arthroplasty for surgeons who are performing knee joint replacement and are eager to improve their techniques and patient management. All delegates were directed to the ESSKA Academy where the pre-course educational content had been uploaded. Twenty-five delegates from 11 countries had an intense 1.5-day training with lectures, case discussions, sawbone workshops and finally performing a total knee joint replacement operation in fresh cadavers under the supervision of instructors. Two fresh cadaver sessions in ten knees, with in groups of three delegates and two instructors per session allowed delegates to interact with the faculty in a one-on-one basis and perform the surgery under the supervision of expert EKA faculty. The course started with a Kahoot quiz, measuring the experience level of the delegates and was followed by an intense 1.5-day training. Delegates this year were from diverse countries, including Italy, France, Poland, Portugal, Romania, Turkey, Jordan, Kuwait, Georgia, United Kingdom and Greece. The course closed with a post-course Kahoot evaluation. The winner of the post course evaluation, Alberto Castelli was awarded a small gift. The delegates first performed primary TKA’s on sawbones to familiarize themselves with the instrumentation of Stryker Triathlon Knee Replacement system. The next day, surgery was performed on fresh cadaveric specimens using the same instrumentation. This was preceded by a cadaveric demonstration of balancing the flexion and extension gaps using robotics (Stryker, MAKO) utilizing different alignment strategies.

Robotic demonstration of ligament balance and alignment

The open air dinner at Spicy Restaurant in Istinye further strengthened the ties between faculty and delegates, allowing further opportunities for mentorship and EKA membership.

Reha Tandogan
ESSKA-EKA Chairman
Course Chairman

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.

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/

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.

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

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

On 13 September 2021, ESSKA-EKA held their Specialty Members Meeting all virtually. Under the constraints of the current COVID-19 restrictions, it was a fantastic success. More than 70 enthusiasts of the degenerative knee took active part in this two-hour event. The first part was scientific, and for the second, EKA Chairman Michael Hirschmann gave a comprehensive summary of the Section’s numerous activities during the last 12 months. All the activities were possible thanks to the work of the EKA board, focus group members and all the EKA members.

Highlights of their activities included:

• Five webinars about different topics around the degenerative knee with many EKA members involved
• Two EKA In-Touch Section newsletters
• A tremendous increase of social media visibility and followers
• Nine peer-reviewed publications, four in collaboration with EHS (European Hip Society) and one with AAHKS (American Association of Hip and Knee Surgeons)

The main theme of the scientific landmark session was “Horizon 2030 - the future of knee joint preservation and arthroplasty”. The esteemed faculty looked to the future, presented new technological or surgical advancements in their field, and finally, painted a colourful and comprehensive picture about the future of degenerative knee surgery.

Prof. Antonia Chen (USA) started with a fascinating overview about “What we can expect from technological development and digitalization?”. She explained the latest trends and activities with regards to augmented reality, robotic surgery, remote surgery, telesurgery and artificial intelligence. In the discussion it was clear that: “Technology is here to stay as it makes surgery more reliable. We need to get used to it. Orthopaedic surgery will be among the front line of early changes.”

Then Prof. Markus Arnold (Switzerland) highlighted current and future chances of personalization in knee arthroplasty. Firstly Prof. Arnold showed the great variability of knee anatomy and explained the knee phenotype concept. He then explained the pros and cons of customized TKA and emphasized that customized TKA designs might represent the ultimate solution to address different constitutional phenotypes. Only when the soft tissue envelope with its laxity is restored does the knee work perfectly after TKA.

Prof. Carsten Tibesku (Germany) extended on the previous talk and then presented the phenotype TKA alignment strategy based on custom implants.

Dr. Nanne Kort (The Netherlands) brought a new aspect into the discussion after his presentation about future patients' management including digital patient pathways, 5G wireless transmission technology, smartphone apps, wearables and much more. He strongly believes that patients’ expectation management is not only a marketing tool but makes a real difference for the patient and the treating surgeon.

Finally, Prof. Jean-Yves Jenny (France) showed the clinical value of fast-track and out-patient TKA. There is no difference in complication, reoperation and readmission rates after fast-track or out-patient total knee arthroplasty. In the discussion all participants agreed that protocols for outpatient TKA is still missing and EKA should put more efforts in those.

The EKA virtual Section members meeting was a great event allowing at least most of our EKA members to meet virtually. However, we are looking forward to seeing us all face2face in Paris for the ESSKA congress. Personal contact cannot be substituted by virtual meetings forever.

If you missed the scientific meeting or would like to watch it again, the content will be available next month on the ESSKA Academy.

Revision surgery in total knee replacement (TKR) must take into consideration various aspects, such as management of bone loss, joint line restoration, level of implant constraint and potential infection. ⁽¹⁾ One of the most important and often underrated aspects is the role of the patella in the failure of knee arthroplasty and its management. ^(2,3,4) Patellar problems represent one of the most common causes of revision after TKR and two scenarios can be encountered:

1. Painful knee after TKR due to a patellofemoral or extensor apparatus related cause

2. Painful knee after TKR with symptoms around the patella due to non-patella related problems such as maltracking or instability

This article particularly deals with the first scenario.

Specific patellofemoral complications include patellar component wear and loosening, patellar and soft tissue impingement, patellar fracture, avascular necrosis, unexplained anterior knee pain, extensor mechanism ruptures, and patellofemoral instability with or without component malposition. (Figure 1) The management of the patella during a complete revision of TKA depends on the fixation, wear and alignment of the patellar component and residual bone stock. This paper reviews the options for treating patellar problems in failed TKR based on the authors' experience and evidence from the current literature.

Tunnel techniques to fix the MPFL graft in patients with open physes require the use of fluoroscopy to define the exact location of the MPFL origin and avoid damage to the growth plate. The tunnel diameter should be as small as possible, and the implant length should be adjusted to avoid penetrating the intercondylar notch (Figure 1). Femoral sockets created in the epiphysis under fluoroscopic guidance are safe and do not cause angular deformity or leg length discrepancy [8].

Figure 1: Loosening of the patellar component at 14 years in an otherwise well-functioning knee in a patient whose job requires extended periods of kneeling.

Pre-operative planning

Pre-operative planning is crucial to ensure a good outcome after revision surgery. Patellar height and the level of joint line should be analysed on x-rays, and patellar tracking might be frankly evaluated in skyline (Merchant) views. ⁽⁵⁾ (Figure 2). It needs to be highlighted that commonly used bony landmarks to determine the patellar height may have changed after TKR, and measurement methods have to be adapted accordingly. ⁽⁶⁾ A 2D or 3D CT scan is recommended to meticulously analyse the rotation of the femoral and tibial TKR components. Frequently, patello-femoral malalignment is due to rotational errors of the femoral and/or tibial TKR components. CT with metal artifact splatter reduction algorithms might also be helpful to determine component loosening and to evaluate the residual patellar bone stock. ⁽⁷⁾ The clinical evaluation should include the presence of anterior knee pain, signs of objective/subjective instability and lateral flexion gap asymmetry or patellar displacement or dislocation in flexion. One should be reasonably certain that the overloading or prorgression of OA in the non-resurfaced patella is the cause of the patient’s symptoms before deciding on secondary patellar resurfacing. For this purpose the use of bone scans or SPECT-CT may be helpful. ⁽⁸⁾

Figure 2: Skyline view of the patella showing loosening of the patellar component and bone erosion of the lateral patella with subluxation.

Implant retention

If the patellar component is stable and no maltracking or significant wear is found, implant retention is the best option since this preserves bone stock and avoids the potential complications of a complex revision. The retained patellar component should be well fixed, no radiological signs of osteolysis should be present and the patella should track normally. The retained patellar component should have a minimum bone thickness of 12-14mm without any overstuffing. In particular in females overstuffing might be an issue, when resurfacing a thin native patellar. Minor wear and slightly oblique cuts can be ignored if the implant is stable. Mix and match of patellar buttons with femoral components from different brands is acceptable, since most of the trochlear designs of contemporary revision systems accommodate spherical patellar button designs. No adverse outcomes have been reported revisions with patellar and femoral components from different companies. ⁽⁹⁾ However, it needs to be mentioned that legally the surgeon changes his state from user to manufacturer. Good clinical results with patellar retention after revision TKR have been reported. ^(9,11) However, implants and instrumentation should be available in the operating room in case of an unforeseen need for patellar revision, dictated by the intra-operative findings.

Revision of the implant

Revision of the patellar implant should be performed if loosening, significant wear, bone loss or maltracking are present. The options are revision with a standard all-poly patella, a biconvex implant, use of bone graft, trabecular metal bony interface implants, and gull-wing osteotomy.

Revision with a standard all-poly patella

Patellar revision using a standard all-poly implant can be performed for painful non-resurfaced patella, kinematic abnormalities of the primary implant, or loosening without severe bone loss. This procedure is successful if remaining host bone is >12-14 mm in thickness and adequate remaining cancellous bone is present for cement for interdigitation. A smaller button type implant instead of an asymmetrical/anatomical patellar component may be preferred cases of maltracking to permit medialisation and lateral facetectomy. The patella-implant thickness should be measured, and in case of overstuffing, further bone resection should be performed to reduce the volume of the patella. The outcomes of isolated secondary patellar resurfacing for painful TKA are controversial with satisfactory results in only 2/3 of the cases. ⁽¹²⁾ Therefore, the decision to perform an isolated patellar revision should be made after all other causes of pain have been ruled out.

Revision with bi-convex implants

Some patellar remnants can have a central bone defect with a relatively well preserved circumferential bony stock, this is usually seen in cases where the patellar implant had to be removed for infection. In these cases, using a standard all-poly patella is not possible due to the lack of central bone and a bi-convex implant can be a practical option. The biconvex patella was designed to address these problems by maintaining a peripheral bony rim of the patella and using a smaller-circumference inset implant with greater central thickness. ⁽¹³⁾ A residual patellar bone thickness after debridement/preparation of at least 4/6 mm is needed to securely fix these implants. ⁽¹⁴⁾

Patella bone grafting

The management of severe patellar bone loss during revision total knee arthroplasty has proven to be particularly challenging. Autograft or allograft bone, which is placed within a soft-tissue flap along the remnants of the remaining native patella has been used as a salvage procedure in cases with significant bone loss. This procedure has the potential for restoring patellar bone stock and may improve functional outcomes by facilitating patellar tracking and improving quadriceps lever arm. ⁽¹⁵⁾ Allograft bone chips can also be used. The bone graft may remodel and partially resorb with longer follow-up, but clinical outcomes are satisfactory ⁽¹⁶⁾. Although rare, patients with previous total patellectomy may also benefit from this procedure during TKA. (Figure 3)

Figure 3: Bone grafting of the patella. An iliac crest bone graft is placed in a pouch created in the extensor mechanism and sutured.

Trabecular metal implants

The trabecular metal patellar component has been introduced to allow patellar resurfacing in the setting of marked patellar bone loss or prior patellectomy. The design of these implants permits the restoration of the patellar leverage action in many cases, restoring a significant part of the quadriceps function. Some of these implants have also been used as substitutes for a missing patella. The trabecular metal implant is sutured to the remaining bone and soft tissue and a polyethylene patellar button is cemented on to the metal. This radical approach has shown variable results, with some good clinical cases described in the literature. The outcomes are acceptable in cases where there is a remnant of vital bone for ingrowth, however, disappointing outcomes have been reported in patients with total patellectomy. ⁽¹⁷⁾ The difficulty remaining is to foresee the postoperative patellar tracking with active quadriceps tension.

Gull-wing osteotomy

The gull-wing osteotomy is a reconstructive technique in which a sagittal osteotomy is made on the articular surface of the patella. The medial and lateral borders of the patella are then displaced anteriorly, creating a “v” or gull-wing configuration, creating a more convex articular surface to track in the concavity of the femoral trochlear groove.⁽¹⁸⁾ This procedure is indicated when the patellar remnant is less than 12 mm thick. Acceptable results with healing of the osteotomy and centrally tracking patella have been reported with this technique ⁽¹⁹⁾ making this a salvage option for treating the non-resurfaceble patella during revision TKR.

Patelloplasty (Resection Arthroplasty)

Removal of the patellar component with shaping & retention of the patellar bony shell can be performed if the remaining patella is not suitable for resurfacing. Although satisfactory outcomes at mid-term follow-up have been reported with this technique ⁽²⁰⁾, these patients have worse outcomes compared to patients with retained or resurfaced patella ⁽²¹⁾ and there is a further risk of mechanical attrition leading to extensor mechanism failure.

Patellectomy

Patellectomy is a historical salvage procedure, with limited use in modern revision surgery. This approach may be considered in multiple operated patients with severe bone loss, however, other options such as bone grafting should be considered before patellectomy.

Conclusion

Management of patellar problems during revision TKR remains complex, requiring an accurate pre-operative planning and intra-operative evaluation even for a well experienced knee surgeon. The options described in this overview may help the surgeon in the decision making process.

References:
1. Postler A, Lützner C, Beyer F, Tille E, Lützner J. Analysis of Total Knee Arthroplasty revision causes. BMC Musculoskelet Disord. 2018;19(1):55.
2. Naudie D.D.R., Bell T.H., McAuley J. (2012) Technique of revision in total knee arthroplasty: The patella. In: The Knee Joint. Springer, Paris.
3. Campbell DG, Duncan WW, Ashworth M, Mintz A, Stirling J, Wakefield L, Stevenson TM. Patellar resurfacing in total knee replacement: a ten-year randomised prospective trial. J Bone Joint Surg Br. 2006; 88(6):734-9.
4. Putman S, Boureau F, Girard J, Migaud H, Pasquier G. Patellar complications after total knee arthroplasty. Orthop Traumatol Surg Res. 2019;105(1S):S43-S51.
5. Bindelglass DF, Cohen JL, Dorr LD. Patellar tilt and subluxation in total knee arthroplasty. Relationship to pain, fixation, and design. Clin Orthop Relat Res. 1993;(286):103-9.
6. Caton, J.H., Prudhon, J.L., Aslanian, T. et al. Patellar height assessment in total knee arthroplasty: a new method. Int Orthop 2016; 40, 2527–2531.
7. Abdallah AC, Chamseddine AH. Guiding principles and pearls in a stepwise surgical technique of revision total knee arthroplasty. J Med Liban. 2016; 64(3):126-33.
8. Hirschmann MT, Amsler F, Rasch H. Clinical value of SPECT/CT in the painful total knee arthroplasty (TKA): a prospective study in a consecutive series of 100 TKA. Eur J Nucl Med Mol Imaging. 2015; 42(12):1869-82.
9. Lonner JH, Mont MA, Sharkey PF, et al. The fate of the unrevised all-polyethylene patellar component in revision total knee arthroplasty. J Bone Joint Surg Am 2003; 85:56–59.
10. Barrack RL, Rorabeck C, Partington P, et al.The results of retaining a well-fixed patellar component in revision total knee arthroplasty. J Arthroplasty 2000; 15:413–417.
11. Yeroushalmi D, Zak S, Sharan M, Bernstein JA, Schwarzkopf R, Rozell JC. Patellar Tracking in Revision Total Knee Arthroplasty: Does Retaining a Patella From a Different Implant System Matter? J Arthroplasty. 2021; 36(6):2126-2130.
12. van Jonbergen HP, Boeddha AV, M van Raaij JJ. Patient Satisfaction and Functional Outcomes Following Secondary Patellar Resurfacing. Orthopedics. 2016; 39(5):e850-6.
13. Maheshwer CB, Mitchell E, Kraay M, Goldberg VM. Revision of the patella with deficient bone using a biconvex component. Clin Orthop Relat Res. 2005; 440:126-30.
14. Erak S, Bourne RB, MacDonald SJ, McCalden RW, Rorabeck CH. The cemented inset biconvex patella in revision knee arthroplasty. Knee. 2009; 16(3):211-5.
15. Hanssen, AD Bone-Grafting for Severe Patellar Bone Loss During Revision Knee Arthroplasty, J Bone Joint Surg Am 2001; 83(2):171-6.
16. Abdel MP, Petis SM, Taunton MJ, Perry KI, Lewallen DG, Hanssen AD. Long-Term Results of Patellar Bone-Grafting for Severe Patellar Bone Loss During Revision Total Knee Arthroplasty. J Bone Joint Surg Am. 2019; 101(18):1636-1644.
17. Kumar Nanjayan S, Wilton T. Trabecular metal patella--is it really doomed to fail in the totally patellar-deficient knee? A case report of patellar reconstruction with a novel technique. Knee. 2014; 21(3):779-83.
18. Klein GR, Levine HB, Ambrose JF, Lamothe HC, Hartzband MA. Gull-wing osteotomy for the treatment of the deficient patella in revision total knee arthroplasty. J Arthroplasty. 2010; 25(2):249-53.
19. Gililland JM, Swann P, Pelt CE, Erickson J, Hamad N, Peters CL. What Is the Role for Patelloplasty With Gullwing Osteotomy in Revision TKA? Clin Orthop Relat Res. 2016; 474(1):101-6.
20. Dalury DF, Adams MJ. Minimum 6-year follow-up of revision total knee arthroplasty without patella reimplantation. J Arthroplasty. 2012 Sep;27(8 Suppl):91-4.
21. Tetreault MW, Gross CE, Yi PH, Bohl DD, Sporer SM, Della Valle CJ. A classification-based approach to the patella in revision total knee arthroplasty. Arthroplast Today. 2017; 3(4):264-268.

Degenerative knee surgery has made substantial progress during the last decade.

The upcoming EKA Members’ meeting "Horizon 2030 - the future of knee joint preservation and arthroplasty" on Monday, 13 September 2020 at 18:30hrs will feature intriguing presentations, free papers and lively discussions.

This meeting is reserved exclusively for EKA members.

Use the links below to review the preliminary programme and register now for free.

Would you like to join this meeting but are not yet an EKA member? No problem, you can join EKA today and still have time to register for the meeting!

We are looking forward to seeing you there!

Following the rescheduling of the ESSKA Speciality Days 2021 to November 2023, we are delighted to announce a series of four online Section Meetings organised exclusively for Section members.

A chance to get back together, enjoy some top-quality specialised science and hear the latest news from the Section leadership.

Each Section Speciality Meeting will focus on a specific topic and will feature a 90-minute high level scientific programme followed by a Members' meeting.

Save the date and keep an eye out for more information!

Not yet an ESSKA member or a Section Member? No problem - you can still join today!