Biomechanical And Clinical Changes In ACL Injured Subjects Following A Neuromuscular Training Program

Abstract

Neuromuscular exercises to induce changes in lower extremity neuromuscular responses are being implemented for subjects with anterior cruciate ligament (ACL) injury during the rehabilitation programs. While effectiveness has been demonstrated in a few studies, the mechanism responsible is for these changes are unknown. PURPOSE The purpose of this study was to determine changes in biomechanical-, electromyographic (EMG)-, and clinical outcome following a rehabilitation program including neuromuscular exercises in ACL injured subjects. SUBJECTS Thirty ACL injured subjects with a mean age of 26 years, participated in a 20 session rehabilitation program consisting of balance-, jumping-, perturbation exercises and lower extremity strengthening exercises. METHODS Prior to training, and after completing training, subjects were examined using knee arthrometer (KT-1000), Knee Outcome Survey (KOS-ADL), VAS for satisfaction, the new version of the IKDC form, quadriceps and hamstring muscles strength (Cybex 6000), 4 functional knee tests, and motion analysis testing (Qualysis); first, ten trials of free-speed walking were collected, followed by three trails of one-leg jumping on each leg. An 8-camera motion analysis system was used to collect lower extremity kinetic and kinematic data at a frequency of 240 Hz. Rigid body analysis was used to calculate the hip, knee, and ankle angles and moments at initial contact, peak knee flexion, and peak knee extension. EMG data were collected at a frequency of 960 Hz with active surface electrodes over the vastus lateralis and medialis, medial and lateral hamstrings, medial gastrocnemius, soleus, and tibialis anterior muscles. RESULTS Significant improvement in knee function was found for the KOS-ADL (p<0.05), VAS (p<0.01), IKDC (p<0.001), one leg hop test (p<0.01) and thigh muscle strength (p<0.05). There was a significant reduced knee excursion and knee moments between involved and uninvolved leg during gait and hop. There were three different movement patterns in the sagittal plane; 67% walk with a biphasic pattern (normal), 11% with an extension moment, and 22% with a flexion moment. After rehabilitation these movement patterns were normalized. CONCLUSIONS This rehabilitation program significantly improved clinical outcome, induced changes in the lower extremity kinematics, kinetics, and muscle activity patterns. This study provides insight into the possible mechanisms underlying the effect of neuromuscular training program.