Evaluation of soft tissue balancing and component alignment in computer-navigated TKA for valgus knee.

Abstract

Computer-navigated total knee arthroplasty (CN-TKA) is useful for improving the accuracy of osseous cuts, soft tissue balance, and component placement. However, the usefulness of CN-TKA for valgus deformity remains unclear. This study aimed to assess the availability of CN-TKA for valgus deformities and compare it with CN-TKA for varus knees. A total of 74 cruciate-retaining CN-TKAs (20 valgus, 54 varus) were included in this study. After implantation, the intraoperative hip-knee-ankle (HKA) angle was recorded during full extension and at 30° and 90° of flexion under three conditions (no stress, valgus stress, and varus stress), and the medial and lateral laxities were calculated. The femorotibial angle (FTA), HKA angle, patellar tilt, mechanical lateral distal femoral angle (mLDFA), and mechanical medial proximal tibial angle (mMPTA) were measured on postoperative radiographs. The Knee Injury and Osteoarthritis Outcome Score (KOOS) and Lysholm score were determined at 1 year postoperatively. The lateral laxity of varus knee in full extension was significantly larger than that of valgus knee (valgus: 0.5 ± 0.7°, varus: 1.2 ± 1.0°, <i>p</i> = 0.011). The medial laxity of valgus knee at 90° of flexion was significantly larger than that of varus knee (valgus: 0.4 ± 0.6°, varus: 0.1 ± 0.3°, <i>p</i> = 0.004). There were no significant differences in the FTA, HKA angle, patellar tilt, mLDFA, mMPTA, KOOS scores, or Lysholme score between the two groups postoperatively. CN-TKA for valgus knee demonstrated acceptable soft tissue balancing and component alignment and good early clinical results comparable to those of CN-TKA for varus knees.