DOES REFLEX INHIBITION CHANGE WITH ACL RECONSTRUCTION?

Abstract

Vastus medialis (VM) muscle atrophy is usually associated with anterior cruciate ligament (ACL) injury or reconstruction. The atrophy is theorized to be the result of reflex inhibition. The H-reflex may be useful in examining muscle function and inhibition following knee injuries, since it is a measure of the motorneuron pool excitability. Changes in the motorneuron pool may be reflected by changes in the H-reflex amplitude. PURPOSE: 1) Examine the VM inhibition in patients with ACL injury or reconstruction; 2) Examine the changes in the muscular inhibition before and after ACL reconstruction. METHODS: Eighteen subjects in 3 groups (6 healthy, 6 ACL deficient, 6 post ACL reconstruction) participated in the study. Healthy subjects had no history of knee, back, leg pain or injury. Patients had a history of an isolated or combined ACL injury or reconstruction. Subjects were tested bilaterally during standing and knee flexion (0°, 30°, 45°, 60°). VM H-reflex was recorded using surface electrodes, after electrical stimulation of the femoral nerve. Four traces of the maximum VM H-reflex amplitude at each knee flexion angle were averaged. Split plot ANOVA was used with α=0.05. RESULTS: There was a significant difference between all patients (ACL deficient and ACL reconstruction) and healthy subjects (p = 0.023). All patients had significantly smaller H- amplitude in comparison to healthy subjects. There was no difference between the patients with ACL deficient and post ACL reconstruction (p >0.05). CONCLUSIONS: Results indicate reflex muscular inhibition of the VM muscle in patients with ACL injury or reconstruction. This reflex muscular inhibition may be the underlying cause of muscle atrophy. It also indicates that reflex muscular inhibition does not change after surgery.