Effect of Traditional Sequential Medial Soft Tissue Release on Knee Kinematics and Alignment

Abstract

Traditionally sequential medial soft tissue release is performed for balancing varus knees in total knee arthroplasty. Its effects on kinematics have been described in extension and 90° flexion in coronal plane but not through complete range of flexion. This study describes its effects on knee kinematics, throughout the range of motion of the knee, studied using a computer navigation system. Twelve cadaveric knees were studied. Femoro-Tibial-Mechanical-Angle (FTMA) was studied in extension, 0°, 15°, 30°, 45°, 60°, 90° and maximum flexion. Sequential medial release was performed in 7 steps, described by Luring et al. [1]. At each step FTMA was measured with and without varus and valgus stressing. A 10 Newton Meter (NM) moment was applied for varus and valgus stress. Most of the initial release steps had little effect on FTMA without force application, especially in the initial 60° of flexion. Application of varus force demonstrated very small changes. Even the application of valgus force demonstrated little change in initial arc of flexion until step 5 in the release was reached. Our study concludes that the present sequence of medial release may not be correct and should be investigated further to modify the sequence for sequential medial release for balancing in varus knees.