Ultrastructures of nerve fibers and muscle spindles in adolescent idiopathic scoliosis.

Muscle biopsies were obtained from the erector spinae to investigate ultrastructural changes in nerve fibers and muscle spindles in patients suffering from adolescent idiopathic scoliosis. Membranous bodies are found in myelinated nerve fibers, both within and outside the muscle spindles. Leptofibrils are formed beneath the sarcolemma of the intrafusal muscle fibers. Additionally, in the intrafusal muscle fiber, there are slight increases in the amount of lipid droplets and glycogen particles, and the sarcoplasmic reticulum is slightly dilated. These changes may affect the metabolism of the muscle fiber and the normal balance of the contractile system. The cause-and-effect relationship of the changes in adolescent scoliosis warrants further investigation.