Choosing fusion levels in progressive thoracic idiopathic scoliosis.

The selection of fusion levels in thoracic idiopathic scoliosis was subjected to multicenter retrospective review to test the validity of the classification system and recommendations of King et al. The 253 patients reviewed were treated by posterior fusion and Harrington instrumentation. Bending films were of little help in selecting fusion levels. Standing radiographs alone were usually adequate. King Type II curves may yield better lumbar correction if the lumbar curve is partially included in the fusion. Type IV curves may be safely fused one level proximal to the stable vertebrae.