Learning curve for CT-free ROSA robot-assisted total knee arthroplasty and its impact on patient-reported outcomes: a retrospective study

To determine whether a learning curve exists for primary robot-assisted total knee arthroplasty (RA-TKA) and whether surgery performed during the learning phase affects postoperative patient-reported outcome measures (PROMs). This retrospective, single-center study included the first 63 patients who underwent RA-TKA between 2024 and 2025. All procedures were performed by a high-volume arthroplasty surgeon who had extensive experience in conventional total knee arthroplasty but no previous experience with RA-TKA. A CT-free ROSA robotic system and a functional alignment (FA) strategy were used for all procedures. Preoperative and postoperative imaging data were collected, including the coronal plane alignment of the knee (CPAK) classification and femorotibial angle. Operative time and complications were also recorded. Functional recovery was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) preoperatively and the WOMAC and Forgotten Joint Score−12 (FJS−12) at 1 year postoperatively. Patients were divided into a learning-phase group comprising the first 34 cases and a post-learning-phase group comprising the subsequent 29 cases, and the two groups were compared. No statistically significant differences in WOMAC or FJS−12 scores were observed between the learning-phase and post-learning-phase groups. Operative time decreased with increasing surgical experience. In exploratory CPAK-related analyses, no statistically significant differences in postoperative PROMs were observed between patients with and without changes in CPAK phenotype or between patients with isolated aHKA or JLO changes and the remainder of the cohort. These findings remained non-significant after Holm-Bonferroni correction, with none of the comparisons reaching the adjusted significance threshold of P < 0.05. Although a learning curve was observed when the surgeon initially adopted the ROSA system, No statistically significant between-phase differences in PROMs were detected. In this single-surgeon cohort, CT-free ROSA RA-TKA performed according to FA principles was associated with satisfactory functional recovery at 1 year without the radiation exposure associated with preoperative CT.