The Optimal Distraction Force to Evaluate Tibiofemoral Joint Gaps in Posterior Stabilized-Total Knee Arthroplasty.

BackgroundObtaining well-balanced soft tissues has been known to be important to achieve natural knee kinematics post-total knee arthroplasty. In conventional procedures, the soft tissue balance has been evaluated using the spacer block or the lamina spreader. However, these procedures depend on the surgeons' experiences and are not quantitative. This study aims to measure the mechanical properties of knee soft tissue with a new ligament balancer and to determine the optimal distraction force to evaluate the tibiofemoral joint gaps in total knee arthroplasty.MethodsThis study included 30 medial knee osteoarthritic patients, who were consecutively scheduled to undergo posterior stabilized-total knee arthroplasty. The mean age of the patients was 73 ± 9.6 years old during surgery, and the mean hip-knee-ankle angle was 13.1 ± 6.5° in varus. After distal femoral and proximal tibial resection, the tibiofemoral joint gaps under several amounts of distraction forces in extension and at 90° in flexion were measured. The load-displacement curves in extension and in flexion were drawn with these data, and the stability range, which was defined as the shift range from the toe region to the linear region in the curves, was calculated.ResultsThe stability ranges were calculated to be 160 N in extension and 140 N in flexion.ConclusionsThese displacement forces were considered optimal loads to evaluate the tibiofemoral joint gaps during surgery and to obtain knee stability post-total knee arthroplasty.