Idiopathic scoliosis: a clinical, morphometric, and histopathological correlation.

At the time of spinal fusion, muscle biopsies were taken from both the convex and concave side at the apex of the curve from 27 patients with idiopathic scoliosis. Histochemical and morphometric studies showed generally small and atrophic type 1 muscle fibers on both sides, with preservation of the normal type 1 predominance. The most striking abnormality was a type 2A predominance over type 2B fibers, the reverse of normal in the paraspinous muscle. These changes showed no correlation with sex, age, or electrical stimulation but showed a significantly greater severity with the duration and severity of the curve. We conclude that these changes are a secondary muscle adaptation to the curve and not its primary etiology.