Changes in cross-sectional area of psoas major muscle in unilateral sciatica caused by disc herniation

Study Design. A clinical prospective cohort study of 15 healthy volunteers and 25 patients with unilateral sciatica from single-level disc herniation. Objectives. To detect any changes in the cross-sectional area of the psoas major muscle in patients with single-level (lateral to mediolateral) disc herniation causing unilateral sciatica. Summary of Background Data. The exact role of the psoas major muscle in the origin of low back pain and sciatica has not been clarified. Methods. Fifteen healthy volunteers and 25 patients with unilateral sciatica from single-level disc herniation were subjected to magnetic resonance imaging of the lumbar spine. The cross-section area of the psoas major muscle on either side was recorded, and differences were noted, In patients, the cross-section area of either side was compared with and duration of sciatica was related to changes in the cross-section area. Results. Insignificant variation in the cross-section area of the psoas major was observed in volunteers. In the patient group, significant reduction in the cross-section area of the psoas major was observed at the level and the site of the disc herniation. A significant correlation between cross-section area of the psoas major and ipsilateral continuous sciatica was found. There was no relation between the reduction of the cross-section area and the amount of disc herniation. Conclusion. The cross-section area of the psoas major is ipsilaterally decreased in unilateral lumbar disc herniation. The reduction in cross-section area is positively correlated with the duration of continuous sciatica.