Inferior results at long‐term follow‐up after extensor mechanism allograft reconstruction in septic compared to aseptic revision total knee arthroplasty

Purpose Extensor mechanism lesion after total knee arthroplasty (TKA) is a catastrophic complication. Reconstruction with extensor mechanism allograft (EMA) has been described as a sound salvage procedure. Its effectiveness at long term and in septic cases is still under scrutiny. The long‐term results of EMA reconstruction for chronic extensor mechanism failures following aseptic and septic revision TKA have been analysed. Methods From the institutional database, 35 patients with a revision TKA (RevTKA) undergoing EMA reconstruction from 2005 to 2015 have been retrospectively identified. A history of periprosthetic joint infection (PJI) was found in 13 (37%) patients. The mean follow‐up was 81.2 months (± 34.7, range 3–120). EMA failures were considered for lag more than 20°, Knee Society Score (KSS) less than 60 points, and/or in the case of revision of the allograft. Results The mean KSS improved from 35.9 (± 16.9, range 0–54) to 86.6 (± 10.4, range 54–99) points in the aseptic group (p < 0.001) and from 27.5 (± 11.6, range 10–44) to 79.4 (± 16.3, range 48–94) points in the septic group (p < 0.001). The extensor lag changed from 48.4° (± 14.5, range 30–90) to 4.6° (± 10.8, range 0–50) in the aseptic group (p < 0.001) and from 56.5° (± 20.8, range 30–90) to 6.1° (± 6.8, range 0–20) in the septic group (p < 0.001). The mean postoperative flexion was 105.2° (± 13.2, range 75–130) in the aseptic group and 102.7° (± 12.5, range 80–120) in the septic group (p = 0.32). Three failures (14% of the cases) occurred in the aseptic group and five in the septic group (38% of the cases). The overall survivorship at 10 years was 83.3% (22 cases, CI95 94.2–121.7) vs 58% (13 cases, CI95 67.2–111.7) in the aseptic and septic group, respectively (p = 0.01). Conclusions EMA reconstruction after extensor mechanism disruptions in TKA is a reliable salvage procedure. The septic nature of the revision decreased the functionality of the knee joint after EMA, but it did not represent a risk factor for re‐ruptures or recurrence of infection. Level of evidence Level III.