Revision of partial to total knee arthroplasty using robotic assistance

To evaluate the feasibility, radiological accuracy, and early clinical outcomes of robotic-assisted conversion of partial knee arthroplasty (PKA) to total knee arthroplasty (TKA) using the ROSA system. Feasibility was defined as successful robotic registration and completion of the procedure using standard primary components without femoral components or augments.

A retrospective cohort of 23 consecutive conversions (medial or lateral unicompartmental and patellofemoral arthroplasties) was analyzed. The minimum follow-up was 12 months. Clinical outcomes were assessed with the Oxford Knee Score (OKS), visual analogue scale (VAS) for pain, and patient satisfaction. Radiological accuracy was evaluated by comparing planned with achieved component alignment (medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), and hip-knee-ankle (HKA)) using paired t-tests, two one-sided tests for equivalence (SD 1.5°), and Bland-Altman analysis.

All cases were successfully registered with the robot and completed without femoral components or augments; 22 of 23 used standard primary components. The mean OKS improved from 17.2 (SD 5.5) to 40.0 (SD 5.0) and VAS pain decreased from 6.7 (SD 1.5) to 1.6 (SD 1.6) (p < 0.001). The mean absolute error between planned and achieved alignment was 0.8° for MPTA and 0.3° for LDFA, confirming accurate restoration, while HKA showed greater variability (mean bias 1.37°; limits -4.1° to 6.9°). One secondary patellar resurfacing was required; no other complications occurred.

Robotic-assisted conversion of PKA to TKA was feasible, bone-preserving, and resulted in significant clinical improvement at 12 months, with precise component alignment but slightly more variation in overall mechanical axis restoration.