Pathology and morphometry of the paraspinous muscles in nonidiopathic scoliosis.

The muscle fibers in 19 patients with nonidiopathic scoliosis were generally small, especially on the concave side of the curve. Type 1 fibers were more frequently atrophic than type 2 fibers, but the former usually remained larger than the latter. Type 1 preponderance was greater on the convex side of the curve; type 2A preponderance occurred bilaterally. These changes are similar to those of idiopathic scoliosis. They resemble those of endurance training or stretch and are interpreted as secondary to the curve.