Morphology of the paravertebral muscles in adolescent idiopathic scoliosis.

Histochemical studies of paravertebral muscles in idiopathic scoliosis have shown a consistently higher proportion of type I fibers on the convex side. In this study of the transversospinal muscles in moderate idiopathic scoliosis, we could demonstrate a lower type II B/II A fiber ratio on the convex side, along with an increased proportion of type I fibers. The capillary count was also higher on the convex side, especially around the type I fibers. The few pathologic changes found were predominately seen in the gravest cases of scoliosis. It is concluded that the fiber type distribution, capillary count, and metabolic enzyme activity on the convex side resembles that seen after endurance training. This suggests a secondary adaptive origin of these changes.