Evaluation of Soft-Tissue Balance during Total Knee Arthroplasty

Abstract

Purpose. To evaluate soft-tissue balance during versus after total knee arthroplasty (TKA). Methods. 18 men and 75 women aged 52 to 85 (mean, 68) years who had moderate-to-severe varus deformity underwent TKAs using the Scorpio non-restrictive geometry posterior-stabilised system (Stryker Howmedica Osteonics; Allendale, [NJ], USA). All surgeries were performed by a single surgeon using the medial parapatellar approach. After the bony and soft-tissue procedures, soft-tissue balance was measured intra-operatively using a tensor/balancer device. The coronal laxity—angles between the cut surfaces of the femur and tibia—were measured at 0° (in extension) and 90° (in flexion). The central gap was also measured. Immediate postoperative soft-tissue balance was measured using an arthrometer, while anteroposterior stress radiographs were being taken. A valgus or varus force was applied just above the knee on the lateral or medial side, with the knee counter-supported and at 15° flexion. Results. Intra-operatively, the mean coronal laxity at 0° (in extension) and 90° (in flexion) was 2.1° and −1.6°, and the mean central gaps were 21.2 and 23.5 mm, respectively. Immediate postoperative mean coronal laxity was 2.9°, indicating that lateral laxity was greater than medial laxity. The postoperative coronal laxity was positively corrected to the intra-operative coronal laxity at 0° ( r =0.304, p=0.003), but not to the intra-operative coronal laxity at 90° ( r = −0.07, p=0.47). Conclusion. Slightly greater lateral laxity was observed after TKA, although equal medial-lateral balance was achieved intra-operatively.