Assessment of the adequency of the current amplitude during intraoperative force measurement of human gracilis muscle

In this study, the adequency of the current amplitudes during intraoperative force measurement of human gracilis muscle is investigated. During anterior cruciate ligament (ACL) reconstruction, gracilis muscle isometric force is measured after stimulating the muscle by different current amplitudes (130, 140, 150 and 160 mA) at fixed knee angles 90°, 60° and 30°. When the knee angle is fixed at 60° and 90°, the mean maximum forces are measured to be 203.8±18.75N and 160.65±8.04N respectively. At 60° knee angle; forces exerted at different current amplitudes are higher than the ones obtained at other knee angles. Due to fatigue, a substantial decrease in maximum force is observed when the knee angle is fixed at 30°. At all conditions, a tetanus state without any fluctuations and minor standard deviations are observed. As a result, it is observed that all stimulation amplitudes tested in this experiment are safe and reliable to measure human gracilis muscle force intraoperatively.