Total Knee Arthroplasty for Fixed Valgus Deformity Correction Using a Modified Lateral Parapatellar Approach.

ABSTRACT

Total knee arthroplasty (TKA) for patients with valgus deformity (> 10 degrees) is technically challenging and has produced variable clinical results in terms of deformity correction, instability, and overall outcomes. The lateral parapatellar approach (LPA) is an alternative to the traditional medial parapatellar approach with potential advantages of direct access for release of tight lateral ligamentous structures with preservation of the medial structures, optimized patellar tracking, preserved medial blood supply to the patella, and less use of constrained implants. We present a case series of a single institution's experience with use of a modified LPA using a Z-capsuloplasty for 35 primary TKA cases in 30 patients with osteoarthritis and Ranawat's type-II fixed valgus deformity with attenuation of medial soft tissues. The mean age of patients was 64.8 years (range 42-78 years). Follow-up duration was a mean of 47.3 months (range 3-130 months). The patients were assessed pre- and postoperatively using radiographic measurement of the anatomic femorotibial angle (FTA) and clinical measurement of range of motion (ROM) and the Chinese knee society score (KSS). Complications and reoperations were recorded. The mean coronal alignment was corrected from 20.4 degrees of valgus (range 11.3-42 degrees) preoperatively to 7.0 degrees of valgus (range 3.6-15.1 degrees) postoperatively. One case required use of a constrained condylar design implant. At a mean of 47.3 months, the mean Knee Society objective and functional scores improved to 91.8 ± 6.6 and 84.3 ± 18.2 points, respectively. Mean ROM was 94.9 degrees preoperatively and 105.7 degrees postoperatively. Three cases (8.6%) had postoperative complications, including transient common peroneal nerve palsy, hematoma, and deep infection. One patient underwent two-stage revision for infection. There were no cases of late instability. The modified LPA using a Z-capsuloplasty is a reproducible and effective surgical technique for performing TKA in the setting of osteoarthritis and severe valgus deformity.