Isolated Polyethylene Insert Exchange for Flexion Instability after Primary Total Knee Arthroplasty Demonstrated Excellent Results in Properly Selected Patients

Abstract Background Historically, isolated polyethylene exchange (IPE) for flexion instability after total knee arthroplasty (TKA) has demonstrated generally poor and unpredictable results. The purpose of this study was to evaluate the results of a single surgeon’s strict indications and protocol for IPE for flexion instability after primary TKA. Methods Between 2009 and 2016, 418 revision TKAs were performed by the senior author. Patients were considered for IPE if they demonstrated excellent radiographic alignment and component positioning preoperatively. Intraoperatively, if component rotation, sizing and fixation were all excellent and the flexion and extension gaps could be balanced, then IPE was performed. We retrospectively reviewed thirty-one knees in 30 patients that were treated with IPE specifically for flexion instability after primary TKA. The mean follow-up was 41 months (range 24-85 months). Nineteen knees were cruciate retaining (CR) TKAs revised to a more constrained “deep-dish” ultracongruent insert, and 12 posterior stabilized (PS) TKAs were revised to thicker PS insert. Results At a mean follow-up of 41 months only 2 out of 31 knees (6.5%) required subsequent component revision surgery for recurrent instability. Knee Society pain scores improved from 70 preoperatively to 86 postoperatively (p Conclusion Isolated polyethylene exchange for flexion instability in carefully selected patients was successful in over 90% of patients for a mean follow up of 41 months. Pain and function scores significantly improved. Longer-term follow-up is necessary to determine if these results are durable over time.