Paraspinal muscle imbalance in adolescent idiopathic scoliosis.

Twelve muscle biopsy samples were taken at operation for spinal instrumentation from each of seven patients suffering from idiopathic scoliosis (one male and six female patients; mean age 14.3 years). The samples were collected from two specific sites (superficial and deep) on both sides on the vertebral column at the level of the apex of the primary curve and two vertebral levels above and below the apex. The results of this study support and extend the findings of other workers. Not only was a significantly larger percentage of Type I fibers found in multifidus muscle at the apex on the curve on the convex side as other workers have found but also in the superficial muscles above and below the apex of the curve on the convex side. These results present a complex picture of muscle fiber characteristics associated with idiopathic scoliosis.