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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

LEVEL OF EVIDENCE: III (retrospective cohort study).