Postoperative neutral coronal alignment does not confer superior functional outcomes after robotic-assisted total knee arthroplasty: A retrospective review

Abstract

Neutral coronal alignment has historically been considered a primary target in total knee arthroplasty (TKA). However, whether restoration of a neutral mechanical axis translates into superior clinical outcomes remains controversial. This study aimed to determine whether achieving a neutral postoperative arithmetic hip–knee angle (aHKA) is associated with improved short-term clinical and patient-reported outcomes following robotic-assisted TKA (RA-TKA). We retrospectively analyzed a consecutive series of 101 patients undergoing primary RA-TKA using an imageless robotic platform. Patients aged ≥50 years with primary osteoarthritis and a minimum follow-up of 12 months were included. Postoperative alignment was assessed using aHKA within the Coronal Plane Alignment of the Knee framework. Patients were stratified into neutral (aHKA within±2.5°) and non-neutral groups (>±2.5°). Outcomes included range of motion and validated PROMs: KOOS, KOOS Jr., and Forgotten Joint Score. At 1 year, PROMs were comparable between groups. KOOS (68.6±14.9 vs. 67.6±16.2), KOOS Jr. (82.1±15.0 vs. 82.0±17.2), and Forgotten Joint Score (72.4±22.7 vs. 67.9±24.4) showed no significant differences after adjustment ( P =0.854). PASS achievement rates were similar across all domains. On multivariable analysis, neutral alignment was associated with slightly lower pain during knee extension (β=−1.08; 95% CI: −2.10 to −0.07; P =0.037). In our study, neutral postoperative coronal alignment was not associated with superior short-term clinical or patient-reported outcomes following RA-TKA. Level IV