Imageless kinematic versus CT-based functional alignment in robotic-assisted total knee arthroplasty: A propensity score-matched comparative study.

Abstract

Robotic-assisted total knee arthroplasty (rTKA) enables reproducible implementation of personalized alignment strategies, including kinematic alignment (KA) and functional alignment (FA). However, direct comparative data between imageless KA-rTKA and CT-based FA-rTKA remain limited. This study compared six-month patient-reported outcome measures (PROMs) between these strategies, with early postoperative recovery evaluated as secondary outcomes. A retrospective analysis of 206 propensity-matched primary rTKA cases (January 2024-January 2025) was conducted. Matching was based on age, sex, body mass index, and baseline PROMs. Primary outcomes included six-month Knee Society Scores (KSS), Oxford Knee Score (OKS), Short Form-36 (SF-36), minimal clinically important difference (MCID) achievement, patient satisfaction, and expectation fulfillment. Secondary outcomes included postoperative day one (POD1) knee range of motion, pain scores, and ambulation distance. The matched cohort comprised 128 females and 78 males, with mean age 68.7 ± 7.7 years and body mass index 27.1 ± 4.8 kg/m². Six-month PROMs, MCID achievement, satisfaction, and expectation fulfillment were comparable between groups (all P > 0.05). The KA-rTKA group demonstrated greater POD1 ambulation distance compared with FA-rTKA (22.6 ± 21.1 m vs 15.8 ± 12.2 m; P = 0.010), with no significant differences in pain scores or knee range of motion. Imageless KA-rTKA and CT-based FA-rTKA produced equivalent six-month functional outcomes. While KA-rTKA demonstrated modestly greater early ambulation, this did not translate into clinically meaningful differences at six months, suggesting both alignment strategies achieve similar short-term outcomes with robotic assistance. III, retrospective comparative cohort study.