The Effect of Thigh and Goniometer Restraints on the Reproducibility of the Genucom Knee Analysis System

We compared the reproducibility of measurements made with the Genucom knee analysis system using two methods of restraint. The first method was that sug gested by the manufacturer and consisted of clamping the thigh to the examination chair with 70 N of vertical force and 110 N of mediolateral force and used a single elastic strap to secure the electrogoniometer cuff to the leg. In the second, or enhanced, method, the vertical and mediolateral clamping forces were each increased to 156 N, and an additional strap was used to secure the cuff to the leg. Tests performed were the anteroposte rior stress tests at 20° and 90° of knee flexion, and the varus-valgus stress test, the internal-external rotation stress test, and the medial and lateral pivot shift tests at 20°. Five normal subjects were installed and tested on 6 different days with the manufacturer's suggested se curing method and on 12 different days with the en hanced securing method. The enhanced method of re straint resulted in significantly reduced day-to-day variance for all tests performed except the varus-valgus stress test.