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 control group. Objectives. To study whether changes in the moments produced at the ankle acid knee joints during walking reflect the neurologic level of a herniated nucleus pulposus. Summary of Background Data. Lumbar herniated discs often cause muscle weakness, reduced motor function, and change in walking capacity. The specific effects of a disc herniation on muscle function during gait is poorly documented. Methods. Conventional physical examination and kinetic analysis of gait were performed on 16 patients who subsequently underwent surgery for herniated discs (eight with L4-L5 and eight with L5-S1 disc herniations) and 16 healthy control subjects. The three components of the external moment at the ankle and knee were computed. The peak magnitudes of specific components of the external moments were compared with those of the control group. Results. Reduced external ankle plantar flexion moment, indicating a decreased function of the ankle dorsiflexors, was found in patients with herniated nucleus pulposus of both L4-L5 and L5-S1. Reduced external ankle dorsiflexion 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 those with herniations at L4-L5. Conclusions. Preoperative gait analysis identified functional deficits of the muscles about the ankle and foot that relate to the level of the herniation. Kinetic measurements can assist in understanding the functional limitations associated with specific levels of a herniation.