Surgeon Learning Curve With Selection of New Total Knee Arthroplasty Implants and Risk of Revision: A Registry-Based Cohort Study.

Introduction: Prior studies have reported learning curves as surgeons adopt new technology/techniques. The authors sought to evaluate revision risk following primary total knee arthroplasty (TKA) to assess whether a learning curve was observed as surgeons transitioned to 1) a new implant from the same manufacturer and 2) a new implant from a new manufacturer.

Methods: Patients ≥ 18 years of age who underwent primary fixed bearing, posterior stabilized, fully cemented TKA with patella resurfacing were identified using a US integrated health care system's total joint replacement registry (2009-2023). The exposure groups were categorized in these groups: baseline implant (reference), first 50 TKA with new implant (≤ 50), second 50 (51-100), third 50 (101-150), and the remainder (> 150). A multiple Cox proportional hazard regression was used to evaluate revision risk with adjustment for confounders.

Results: The intra-manufacturer cohort comprised 42,743 TKA. A higher revision risk was observed for the ≤ 50 group compared to the baseline group (hazard ratio [HR], 1.37; 95% confidence interval [CI], 1.01-1.86); no other differences were observed after the first 50 TKA (51-100: HR, 0.98; 95% CI, 0.71-1.34; 101-150: HR, 0.95; 95% CI, 0.69-1.32; > 150: HR, 0.99; 95% CI, 0.79-1.34). However, the association was no longer significant after excluding the TKA performed with the Attune fixed bearing tray, which has been associated with a higher risk of revision in the total joint replacement registry. The inter-manufacturer cohort comprised 19,817 TKA. No differences were observed when comparing a new manufacturer to the baseline manufacturer.

Discussion: Surgeons should be cautious for the first several TKA when transitioning to a new implant given the relationship between surgeon and implant on revision risk.

Level of evidence: Level III.