Abnormalities in muscle function during gait in relation to the level of lumbar disc herniation

Study Design. A comparison between gait in patients undergoing surgery for L4 and L5 lumbar disc herniations and that in an age- and weight-matched co ntrol group. Objectives. To study whether changes in the moments produced at the ankle a cid knee joints during walking reflect the neurologic level of a herniated nucleus pulposus. Summary of Background Data. Lumbar herniated discs often cause muscle weakn ess, reduced motor function, and change in walking capacity. The specific e ffects of a disc herniation on muscle function during gait is poorly docume nted. Methods. Conventional physical examination and kinetic analysis of gait wer e performed on 16 patients who subsequently underwent surgery for herniated discs (eight with L4-L5 and eight with L5-S1 disc herniations) and 16 heal thy control subjects. The three components of the external moment at the an kle and knee were computed. The peak magnitudes of specific components of t he external moments were compared with those of the control group. Results. Reduced external ankle plantar flexion moment, indicating a decrea sed function of the ankle dorsiflexors, was found in patients with herniate d nucleus pulposus of both L4-L5 and L5-S1. Reduced external ankle dorsifle xion moment, indicating a decreased function of the ankle plantar flexors, was found only in patients with a lesion to the L5-S1 disc, but not in thos e with herniations at L4-L5. Conclusions. Preoperative gait analysis identified functional deficits of t he muscles about the ankle and foot that relate to the level of the herniat ion. Kinetic measurements can assist in understanding the functional limita tions associated with specific levels of a herniation.