JOA - 2026-06-27 - Journal Article
Is the Incidence of Conversion from Unicompartmental to Total Knee Arthroplasty Higher Among Surgeons Who Do Not Have Arthroplasty Fellowship Training?
McCormick KL, Schaffer O, Novikov D, Rozell JC
Topics
Key Takeaway
Arthroplasty fellowship-trained surgeons achieved a 2.5% two-year UKA-to-TKA conversion rate versus 5.7% for non-fellowship-trained surgeons (P=0.049), despite operating on older, more comorbid patients with less robotic assistance.
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Summary
This single-institution retrospective study compared two-year UKA-to-TKA conversion rates between arthroplasty fellowship-trained and non-fellowship-trained surgeons performing primary UKA from 2010–2023. Arthroplasty-trained surgeons had a 2.5% conversion rate versus 5.7% for non-trained surgeons (P=0.049), despite their cohort being older (62.9 vs. 58.5 years) with higher Charlson Comorbidity Index scores (5.03 vs. 4.6) and lower robotic utilization (59.4% vs. 84.4%). Lateral UKA demonstrated significantly worse survivorship than medial UKA across both groups (log-rank P=0.0004), and overall complication rates did not differ.
Key Limitation
The absence of multivariable regression controlling for patient age, comorbidity, implant type, and robotic use prevents attribution of the conversion rate difference to fellowship training itself rather than confounding case-mix or technology factors.
Original Abstract
BACKGROUND
Unicompartmental knee arthroplasty (UKA) may offer advantages over total knee arthroplasty (TKA) for select patients, but implant failure leading to conversion to TKA remains a concern. The purpose of this study was to compare two-year conversion rates to TKA following UKA performed by arthroplasty fellowship-trained surgeons versus surgeons who did not have arthroplasty fellowship training at a single academic institution.
METHODS
A retrospective review was performed of primary UKAs conducted at a single academic institution between 2010 and 2023, which had at least two years of follow-up and implant data available. Cases were grouped based on surgeon fellowship training. Demographics, operative characteristics, postoperative complications, and conversion to TKA were analyzed at two and five years, with characterization of all TKAs performed within five years. Implant survivorship was assessed using Kaplan-Meier analysis; group comparisons used Chi-square or Fisher exact tests as appropriate. A total of 413 UKAs were included, with 202 performed by arthroplasty-trained surgeons and 211 by non-arthroplasty-trained surgeons. Patients in the arthroplasty-trained group were older (mean 62.9 versus 58.5 years, P<0.001) and had higher Charlson Comorbidity Index scores (mean 5.03 versus 4.6, P<0.001). Technology utilization differed, with greater robotic use among non-arthroplasty-trained surgeons (84.4 versus 59.4%, P<0.001).
RESULTS
At two years, conversion to TKA occurred in 2.5% of cases performed by arthroplasty-trained surgeons compared with 5.7% in the non-arthroplasty-trained group (P=0.049). Overall complication rates did not differ. Lateral UKA demonstrated significantly worse survivorship than medial UKA (log-rank P=0.0004). Among 29 TKAs performed within five years, indications and operative characteristics were similar between groups, but revision surgeon specialty differed significantly (P=0.001).
CONCLUSIONS
Arthroplasty fellowship training was associated with a lower observed two-year conversion rate to TKA despite treatment of older, more comorbid patients and lower utilization of robotics. Failure patterns and survivorship beyond two years were similar.