Histochemistry and morphology of the multifidus muscle in lumbar disc herniation: comparative study between diseased and normal sides.

STUDY DESIGN: This comparative study was conducted on 19 patients (13 men and 6 women) with lumbar disc herniation (LDH). The histologic and histochemical differences and changes in the back muscles of the diseased and normal sides were evaluated.

OBJECTIVES: To determine the histologic differences in the back muscles between the diseased and normal sides in lumbar disc herniation.

SUMMARY OF BACKGROUND DATA: The morphologic changes of back muscles between the diseased and normal sides in lumbar disc herniation were examined using histologic and histochemical methods. Few studies have reported the difference in these changes based on quantitative analyses.

METHODS: All samples were harvested bilaterally from the multifidus muscle at the level of L4-L5 or L5-S1 in patients with lumbar disc herniation and then were examined by histologic and histochemical methods (hematoxylin-eosin, Gomori trichrome, NADH-TR, and ATPase stains). The percentage, cross-sectional area (CSA), and lesser diameter (LD) of muscle fibers were measured using computerized image analysis. The Wilcoxon, paired t, Kruskal Wallis, and Fisher tests were used for statistical analysis.

RESULTS: Both Type I and II fibers in the diseased side were significantly smaller than those from the normal side. In the diseased side, the potential strength of Type II fibers was weakened. Some pathologic changes (fiber type grouping, small angulated fibers, group atrophy, moth-eaten appearance, and internal nuclei, etc.) in the diseased side were more obvious than those in the normal side. When the straight leg raising test results were abnormal, both Type I and II fibers in the diseased side were smaller than those in the normal side. The Type I fibers of the diseased side were significantly smaller when the patients had symptoms of central low back pain. The size of the Type I fibers as well as of the Type II fibers did not differ between the diseased and normal sides in patients with unilateral and bilateral low back pain.

CONCLUSIONS: The present study indicated that there were differences in the characteristics of the multifidus muscle between the diseased and normal sides in patients with lumbar disc herniation. The changes in muscle characteristics primarily were related to the disc protrusion. In addition, different locations of the low back pain seemed to cause different secondary effects on the muscle characteristics.