Soft tissue tension in extension in total knee arthroplasty affects postoperative knee extension and stability

The purpose of this study was to assess correlation of soft tissue tension in extension with postoperative extension deficit and valgus/varus instability. Sixty-four osteoarthritic knees that underwent primary total knee arthroplasty were investigated. Soft tissue tension in extension was measured during operation with a balancer/tensor device. Extension deficit was measured, and valgus/varus laxity was assessed by stress radiographs in extension and 30°-flexion 1 year after operation. The extension deficit became larger with an increase of soft tissue tension a year after operation. (P < 0.05) The varus laxity in extension and 30°-flexion and valgus laxity in 30°-flexion became smaller with an increase of soft tissue tension (P < 0.05). Our results demonstrated that soft tissue tension during operation affects postoperative knee extension and stability.