Various surgical techniques result in different outcomes for full extensor mechanism ruptures following total knee replacement: A systematic review by the European Knee Associates (ESSKA-EKA)

Purpose: Extensor mechanism (EM) ruptures after total knee arthroplasty (TKA) are rare but lead to substantial functional impairment and morbidity. Treatment remains challenging due to the diversity of surgical techniques and the limited number of comparative studies. The European Knee Associates (EKA) group conducted a systematic review to evaluate available treatments for EM rupture following primary TKA, assess outcomes such as extensor lag, patient-reported outcome measures (PROMs) and walking status, and to identify prevailing trends and complication rates. Methods: A systematic review was registered in PROSPERO (CRD42022341591) and conducted according to Preferred Reporting Items for Systematic Review and Meta-Analysis and Cochrane guidelines. PubMed/Medline and Scopus databases were searched for clinical studies published between 2014 and 2024 reporting outcomes after EM repair in TKA patients. Inclusion criteria encompassed retrospective and prospective studies in English or German. Studies on EM ruptures due to infection, revision TKA, or patellectomy were excluded. Data extraction included demographics, time-to-reconstruction, repair type, extensor lag, PROMs and walking status. Due to heterogeneity, a meta-analysis was not feasible, and results were descriptively reported. Results: A total of 32 studies comprising 893 EM rupture cases were included. The mean patient age was 66.8 years (standard deviation [SD] ± 7.4), with a mean body mass index of 34.5 (SD ± 6.2). Patellar tendon ruptures (39%) were the most frequent. Nine different surgical techniques were identified, including allografts, synthetic meshes, autografts and direct repairs. The overall complication rate was 16%, with autografts having the highest complication rate (38%). All repair techniques led to improvements in extensor lag and post-operative Knee Society Scores exceeding the minimal clinically important difference thresholds. However, walking status and PROMs were inconsistently reported. Conclusions: EM failure after TKA remains a complex complication with variable outcomes depending on treatment strategy. Standardization of surgical techniques and outcome measures, along with multicenter collaborations, is crucial to improve future patient care as the number of TKA procedures continues to rise. Level of Evidence: Level III, systematic review of Level III studies.