EFFECT OF ANTERIOR CRUCIATE LIGAMENT SURGERY ON LOWER EXTREMITY TORQUES AND KNEE SHEAR

Abstract

PURPOSE: The purpose of this study was to assess the effect of anterior cruciate ligament (ACL) reconstructive surgery on hip (HT) and knee (KT) extensor torque, ankle plantar flexor torque (AT), and anterior tibial shear (S). METHODS: ACL deficient subjects (N = 9) were assessed on a semirecumbent variable resistance, closed-chain dynamometer at three time periods: prior to surgery (PRE) and at 3 (3M) and 6 months (6M) following ACL reconstructive surgery. Tests were conducted at 1 and 1.5 Hz and maximum speed at 33% and 50% 1RM. HT, KT, AT and S were recorded at 20%, 40%, 60%, and 80% of the extension phase of the cycle (85° 25° of knee flexion). RESULTS: HT and AT increased and S decreased from the PRE to 3M periods (P < 0.05) while KT remained unchanged. No differences were observed between 3M and 6M for any of the variables. KT was greatest when the knee was more flexed while HT and AT dominated when it was more extended irrespective of test period. The data suggest that persons accommodate to ACL surgery by increasing HT and AT to control S. The hamstrings, as a component of hip extension, and the gastrocnemius, as a component of plantar flexion, may function to counter S, which was reduced from the PRE to 3M post-surgical period. CONCLUSION: ACL reconstructive surgery produces joint torque accommodations in the hip and ankle, which may assist in reducing anterior tibial shear. Supported in part by a grant from the NATA Research and Education Foundation