Aseptic survival of the 1.5-stage exchange arthroplasty for periprosthetic joint infection was acceptable when using an autoclaved femoral component and a new polyethylene insert

Purpose To investigate the aseptic survival of 1.5-stage exchange arthroplasty for periprosthetic joint infection (PJI) after total knee arthroplasty (TKA). Methods Eighty-eight cases of 1.5-stage exchange arthroplasty for PJI without reinfection were retrospectively analysed. The autoclaved femoral component and new polyethylene insert (PE) were implanted using antibiotic mixed cement. The explanted tibial component was not reinserted. The Western Ontario and McMaster Universities Osteoarthritis Index and range of motion were clinically evaluated preoperatively and at the last follow-up (the last time for the implant in situ). Radiographically, hip-knee-ankle angle (HKA) and component positions were measured preoperatively, postoperatively (1 month after the 1.5-stage exchange arthroplasty), and at the last follow-up. The survival rate was analysed using the Kaplan-Meier method, in which failure was defined as reoperation due to aseptic failure. Mean period to failure and failure site were analysed. Factors affecting survival were investigated in terms of demographics and inappropriateness of the postoperative HKA (HKA > 0 +/- 3 degrees) and component positions (a angle > 95 +/- 3 degrees, beta angle > 90 +/- 3 degrees,gamma angle > 3 +/- 3 degrees, and delta angle > 87 +/- 3 degrees). Results The spacer in-situ time was 3.7 years (0.2-6.4). The clinical results improved hip-knee-ankle significantly at the last follow-up. Radiographically, the average HKA was valgus 0.1 degrees postoperatively. The average a, beta,gamma, and delta angles of the postoperative component positions were 959 degrees, 90.4 degrees, 3.8 degrees, and 86.7 degrees, respectively. The 1-, 2-, and 5-year postoperative survival rates were 90.9%, 86.4%, and 80.6%, respectively. The mean period to failure was 2.0 years (0.2-5.3). There were 18 cases of aseptic loosening (20.8%), occurring on both the femur and tibial sides in 1 knee, and only on the tibial side in 17 knees. Inappropriate coronal position of the PE (beta angle > 90 +/- 3 degrees) was a significant factor affecting survival (odds ratio = 5.491; p = 0.011). Conclusion The aseptic survival of the 1.5-stage exchange arthroplasty was acceptable when using an autoclaved femoral component and new PE. The appropriate coronal position of the PE helps ensure favourable survival of 1.5-stage exchange arthroplasty.