Efficacy Evaluation Of Isolated Polyethylene Exchange In Treating Instability After Primary Total Knee Arthroplasty

Objective:The outcome of performing Isolated Polyethylene Exchange(IPE)after total knee arthroplasty(TKA)is under debate.We assess the effectiveness of IPE in treatinginstability after primary total knee arthroplasty.Method: We retrospectively reviewed 11 patients(14 knees)who underwent IPE for instability after primary TKA with well-aligned,well-fixed TKA components.All patients underwent IPE in our institution between 2006 and 2019.The minimum follow-up was 8 months(average,26 months;range,8–69 months).We collected radiographs,Forgotten Joint Score(FJS-12)and the new Knee Society knee Scoring system(2011 KSS)data at follow-up.Results: The mean FJS-12 scores increased from 33.3(range,8.4–68.8)preoperatively to 64.2(range,39.6–79.2)(P < 0.002)and the mean 2011 KSS patient satisfaction score was 13(range,8–18)preoperatively and 26.3(range,18–32)(P < 0.001)at the most recent follow-up.Mean 2011 KS objective scores increased from 48.7(range,42–58)preoperatively to 67.6(range,63-75)(P = 0.001)at the most recent follow-up and mean 2011 KS subjective scores increased from 70.4(range,52–85)to 123.4(range,76–144)(P < 0.001).All of the patients upsizing the tibial inserts by an average of 4mm(range,2-9.5 mm).11 patients(14 knees)underwent IPE for instability,2(2 knees)of them had persistent moderate to severe pain.All of them recovered well at final follow-up.All of the patients were unrevised at final follow-up or death.Conclusion: We believe that a good grasp of the threshold between IPE and revision TKA can help treat better the instability after TKA,while a clear understanding of the type of the instability after TKA,the selection of prosthesis and the balance technique of ligament are prerequisites to a successful treatment.And the corresponding classification system may help to determine suitable patients for this operation.For these indications,IPE could be a recommended option.And it would provide a significant improvement in knee function,quality of life and satisfaction ofpatients who were indicated and highly selected.