Intraoperative component size adjustment is associated with pain-free recovery and good knee flexion after patient-specific instrumentation-assisted medial pivot TKA.

Abstract

Predictors of achieving both pain relief and sufficient knee flexion after patient-specific instrumentation (PSI)-assisted medial pivot total knee arthroplasty (MP-TKA) have been insufficiently studied. This study aimed to identify predictors of achieving pain-free recovery and good knee flexion 1 year after PSI-assisted MP-TKA. This single-center retrospective cohort study included patients with knee osteoarthritis who underwent PSI-assisted MP-TKA and completed a minimum 1-year follow-up. The primary outcome was achieving both knee flexion ≥120° and a numerical rating scale (NRS) pain score ≤1.0 at 1 year postoperatively. Baseline characteristics, radiographic parameters, postoperative knee range of motion (ROM), anteroposterior (AP) laxity, osteotomy thickness, and agreement between PSI-planned and implanted component sizes were evaluated. Variables associated with the outcome in univariate analysis were entered into multivariable logistic regression to identify independent predictors. A total of 64 knees were analyzed, including 21 in the Good outcome group and 43 in the Non-Good group. Overall intraoperative component size adjustment was more frequent in the Good outcome group than in the Non-Good group (81.0% vs 44.2%). Most intraoperative adjustments involved tibial downsizing. In univariate analyses, overall intraoperative component size adjustment, greater patient height, greater preoperative knee extension deficit, and larger AP translation at 90° flexion 1 year postoperatively were associated with favorable outcomes. In multivariable logistic regression analysis including preoperative and intraoperative variables, intraoperative component size adjustment was an independent predictor of achieving pain-free and good flexion recovery (OR = 4.32, 95% CI 1.07-17.45, p = 0.040). Other factors, including patient height and preoperative knee extension deficit and postoperative AP translation, were not independently associated with the outcome. Intraoperative component size adjustment was associated with achieving pain-free and good flexion recovery after MP-TKA. These findings highlight the critical role of intraoperative decision-making in achieving optimal functional outcomes. III (retrospective cohort study).