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 nontrial 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.