Lumbar curve response in type II idiopathic scoliosis after posterior instrumentation of the thoracic curve.

Twenty-four patients with King Type II scoliosis were retrospectively studied to determine if preoperative assessment of lumbar curve flexibility was predictive of postoperative spinal balance. All patients had preoperative lumbar curves exceeding 40 degrees and all underwent selective thoracic fusion with Cotrel-Dubousset or Texas Scottish Rite Hospital instrumentation. The lumbar curves corrected 73% on preoperative bend radiographs. Despite this significant flexibility, the lumbar curves remained larger after surgery than the instrumented thoracic curves and spinal imbalance occurred. This finding was due, in part, to postoperative persistence of obliquity between L4 and the pelvis. When using Cotrel-Dubousset or Texas Scottish Rite Hospital instrumentation, preoperative assessment of the large lumbar curve's flexibility is not particularly helpful in predicting its response to selective thoracic fusion, especially regarding whether postoperative imbalance may occur.