Medial-Pivot Total Knee Arthroplasty with Kinematic Alignment Produces Similar Clinical Outcomes in Valgus and Varus Deformities.

Abstract

Mechanical alignment total knee arthroplasty (TKA) in valgus knees requires soft tissue releases and complex techniques that are unnecessary with kinematic alignment (KA). Few studies have evaluated the outcomes of KA in valgus knees, and fewer have studied KA with medial-pivot (MP) implants. This study compared the clinical outcomes of KA-TKA with MP implants (KA/MP-TKA) in patients with preoperative varus versus valgus alignment. We hypothesized that outcomes following KA/MP-TKA would be equivalent. A prospective database was queried to identify patients who underwent primary KA-TKA with MP implants. Patients were included if they had a preoperative hip-knee-ankle angle ≤177° (varus, n = 302) or ≥183° (valgus, n = 51). A total of 353 consecutive patients were identified. The Forgotten Joint Score (FJS), Knee Injury and Osteoarthritis Outcome Score (KOOS-JR), Knee Society Score (KSS), and range of motion were collected preoperatively and at 6-week, 6-month, and 1-year visits. Patients with preoperative valgus alignment had worse KSS Function and KOOS-JR scores preoperatively (p = 0.04 and p = 0.02, respectively); all other baseline outcomes were comparable. Postoperatively, the valgus group demonstrated better KOOS-JR at 6 weeks (p = 0.004), KSS Pain-Motion at 6 months (p = 0.02), and FJS at 1 year (p = 0.03). The varus group showed better KSS Function at all postoperative visits (p < 0.02). There were no statistically significant differences in flexion or extension between the groups. Patients with valgus alignment undergoing KA/MP-TKA achieved postoperative outcomes that were clinically equivalent or superior to those of patients with varus alignment. These findings support KA-TKA using MP implants as an appropriate surgical approach for preoperative valgus alignment.