Total knee arthroplasty without patella resurfacing leads to worse results in patients with patellafemoral osteoarthritis Iwano Stages 3–4: a study based on arthroplasty registry data

PURPOSE: To determine whether the preoperative degree of degeneration of the patellofemoral joint really affects the outcome of total knee arthroplasty (TKA) surgery without patella resurfacing and thus to establish a parameter that might serve as a guiding factor to decide whether or not to perform retropatellar resurfacing. It was hypothesized that patients with preoperative mild patellofemoral osteoarthritis (Iwano Stages 0–2) would significantly differ from patients with preoperative severe patellofemoral osteoarthritis (Iwano Stages 3–4) in terms of patient-reported outcome (Hypothesis 1) and revision rates/survival (Hypothesis 2) after TKA without patella resurfacing. METHODS: Application of a retrospective–comparative design on the basis of Arthroplasty Registry data that included patients with primary TKA without patella resurfacing. Patients were allocated to the following groups based on preoperative radiographic stage of patellofemoral joint degeneration: (a) mild patellofemoral osteoarthritis (Iwano Stage ≤ 2) and (b) severe patellofemoral osteoarthritis (Iwano Stages 3–4). The Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC) score was assessed preoperative and 1 year postoperative (0: best, 100 worst). In addition, implant survival was calculated from the Arthroplasty Registry data. RESULTS: In 1209 primary TKA without patella resurfacing, postoperative WOMAC total and WOMAC subscores did not differ significantly between groups, but potentially suffered from type 2 error. Three-year survival was 97.4% and 92.5% in patients with preoperative mild and severe patellofemoral osteoarthritis, respectively (p = 0.002). Five-year survival was 95.8% vs. 91.4% (p = 0.033) and 10-year survival was 93.3% vs. 88.6% (p = 0.033), respectively. CONCLUSIONS: From the study findings, it is concluded that patients with preoperative severe patellofemoral osteoarthritis have significantly higher risks for reoperation than do those with preoperative mild patellofemoral osteoarthritis—when treated with TKA without patella resurfacing. Hence, it is recommended that patella resurfacing be applied in patients with severe Iwano Stage 3 or 4 patellofemoral osteoarthritis during TKA. LEVEL OF EVIDENCE: III, Retrospective comparative.