Mechanical and electromyographical gait parameters in the course of rehabilitation after anterior cruciate ligament reconstruction

T. Schmalz, J. Freiwald, A. Greiwing, L. Kocher, H. Ludwig, and S. Blumentritt: mechanical and electromyographical gait parameters in the course of rehabilitation after anterior cruciate ligament reconstruction. Eur. J. Sports Traumatol. rel. res. 23: 146-151, 200 1. We compared the results of the analysis of important biomechanical and electromyographical gait parameters of patients who were treated by means of an autologic patella graft reconstruction after isolated rupture of the anterior cruciate ligament (ACL). A complex gait analysis was conducted on a group of leisure sportsmen (n=19) in the 12(th) post operative week. The gait data of healthy individuals gathered in earlier studies served as reference basis. An optoelectronic camera system (PRIMAS) and two force plates (KISTLER) were used to determine the kinematic and kinetic data (ground reaction forces and torques) of the patient's gait. The surface of the M. tibialis anterior, M. gastrocnemius, M. biceps femoris und M. vastus lateralis electromyograms were recorded by means of a NORAXON-EMG-amplifier. We were not able to detect the frequently described "quadriceps avoidance pattern" in the patient's gait. Rather, there was a significant 7degrees reduction of the knee joint extension at the injured joint during stance phase which was caused by significantly reduced extending torques. These torques normalcy appear in the second part of the stance phase. The uninjured side shows no differences to normal gait. The time structure of the ON-OFF phases of muscle activation shows no differences to the gait of uninjured individuals. The analysis of muscle activation intensify shows a clear reduction of the M. gastrocnemius activity of the injured leg during main activation phase of this muscle, whereas all the other recorded muscles show no activation differences. The activation reduction of the M. gastrocnemius correlates with the reduction of the extending moments which affect the knee joint. Apparently the changes of the mechanical parameters of the knee joint, caused by injury and operation, lead to specific reactions on the neuromuscular level which are mainly constituted by the activation pattern of the M. gastrocnemius and to a lesser extent by the activation pattern of the hamstrings, or the knee extensors. The results indicate that the M. gastrocnemius plays an important part in controlling cyclic movement processes of the knee joint according to its two-joint nature, a fact which has been underestimated up to now. It is likely that modified activation patterns with increased intensities of the hamstrings and the knee extensors as a means of protection are only needed in situations which represent a distinct higher load in contrast to ground level walking. (C)2001, Editrice Kurtis