Surgeon Training and Revision Rates After Patellofemoral Arthroplasty.

Importance: Surgeon training with a specific implant is often not considered in implant registry-based studies, which may lead to unobserved confounding bias. Discrepancies between registry and clinical trial outcomes for patellofemoral arthroplasty (PFA) may originate from differences in surgeon training levels. Objective: To compare revision rates for knees operated on by knee surgeons specifically trained for PFA and knee surgeons who were not. Design, Setting, and Participants: In this population-based cohort study, the framework of a target trial was used to compare outcomes for 2 patient groups: patients who underwent PFA performed by knee surgeons who had (trial surgeons) vs who had not (nontrial surgeons) received focused PFA training as part of a randomized clinical trial. All primary PFA procedures from January 1, 2008, through December 31, 2015, were identified using Danish registries and individual hospital notes with 6 years' follow-up. Data were analyzed from January 24 to March 1, 2024. Exposure: Focused PFA training. Main Outcomes and Measures: The primary outcome was 6-year risk of revision. Analyses were conducted according to a prespecified statistical analysis plan, using multiple logistic regression to estimate marginal risk ratios for 6-year risks of revision, reoperation, and mortality, adjusting for potential confounders. Results: Of 482 eligible knees of patients who had undergone PFA, 274 (57%; 206 female [75%]; mean [SD] age, 61 [13] years) were operated on by trial surgeons, and 208 (43%; 142 female [68%]; mean [SD] age, 57 [12] years) by nontrial surgeons. Trial surgeons operated on knees with higher patellofemoral Kellgren-Lawrence osteoarthritis grade (range 0-4, with 0 indicating no osteoarthritis and 4 indicating severe osteoarthritis) than nontrial surgeons (79% vs 53% with grade 3 to 4) and higher tibiofemoral Kellgren-Lawrence osteoarthritis grades (37% vs 17% with grade 2 to 4). The 6-year revision rate for trial surgeons was 8% (22 of 274 knees) vs 26% (54 of 208 knees) for nontrial surgeons, corresponding to an adjusted relative risk (RR) of 0.35 (95% CI, 0.22-0.56; P < .001). The reoperation rate was 12% (33 of 274 knees) for trial surgeons vs 19% (40 of 208 knees) for nontrial surgeons, with an adjusted RR of 0.71 (95% CI, 0.42-1.18; P = .19). There was no difference in mortality for trial vs nontribal surgeon groups (18 of 274 knees [7%] vs 12 of 208 knees [6%]; adjusted RR, 1.11 [95% CI, 0.53-2.33; P = .79). Conclusions and Relevance: In this cohort study using a target trial emulation approach to assess the association of surgeon training with PFA outcomes, the cumulative 6-year revision rate for PFA was lower for knees operated on by PFA-trained knee surgeons, suggesting that such surgeon training was associated with a better outcome. This suggests that the level of training may be an important confounder for registry-based comparisons of implant outcome, and that this confounder may even obscure inherent implant outcomes.