Patellofemoral arthroplasty-patient demographics and revision causes compared with total and medial unicompartmental knee arthroplasty: long-term follow-up data from the Norwegian Arthroplasty Register.

Background and purpose:  Patellofemoral arthroplasty (PFA) is a rare surgical procedure for isolated patellofemoral osteoarthritis (PFOA). This study compares patient demographics, long-term survival rates, revision risks, and causes of revision in PFA with total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA).

Methods: Data from the Norwegian Arthroplasty Register (NAR) (1994-2022) included 725 PFA, 102,135 TKA, and 14,315 UKA procedures. We used Kaplan-Meier (KM) analysis to calculate implant survival at 2, 5, 10, and 15 years and Cox regression adjusted for confounders to assess revision risks. Revision causes were analyzed for procedures after 2005.

Results:  PFA patients were more often female (72%) than TKA (62%) and UKA (51%) patients and had a lower mean age (54.3 for PFA, 69.0 for TKA, and 65.6 for UKA). At 10 years, KM survival was 85% (95% confidence interval [CI] 80.6-88.2) for PFA, 94% (CI 93.8-94.2) for TKA, and 84% (CI 83.6-85.1) for UKA. Among patients < 60 years, KM survival at 10 years was 84% (CI 79.4-88.1) for PFA, 90% (CI 89.3-90.4) for TKA, and 79% (CI 77.1-80.3) for UKA. In patients < 60 years with < 10 years' follow-up, the adjusted hazard ratios (HR) for revision were 0.9 for TKA and 1.7 for UKA compared with PFA. Adjusted HR for > 10 years' follow-up showed lower revision risks for TKA with 0.3 and no significant difference for UKA (HR 0.9). Progression of OA was the leading cause of revision in PFA (49%).

Conclusion:  PFA was predominantly performed in younger female patients. In patients < 60 years, PFA showed similar 10-year survival to TKA but inferior survival after 15 years. Revision rates for PFA are comparable to UKA but inferior to TKA.