Analysis of factors related to truncal decompensation following Cotrel-Dubousset instrumentation

Spinal imbalance following Cotrel-Dubousset (CD) instrumentation for adolescent idiopathic scoliosis is a problem that is recognized with increasing frequency. We reviewed the clinical records and radiographs of 41 consecutive patients treated with CD instrumentation and attempted to identify factors related to postoperative worsening of spinal balance. Spinal balance was determined by the perpendicular distance of C7 to the center sacral line. Twenty-five were decompensated postoperatively. Sixteen patients had balance that was worse relative to the preoperative films. Eleven of 16 patients with worsened balance postoperative were King type III curves. Of 16 patients with worsened balance postoperatively, 13 had been fused to or below the lower neutral vertebra. Overcorrection of either the primary curve or the composite curve (sum of the measurable curves) relative to the preoperative bending films was not related to postoperative worsening of spinal balance. Fusion to the neutral or stable vertebra with CD instrumentation runs a high risk for postoperative worsening of spinal balance when the derotation maneuver is used. Consideration should be given to avoiding the derotation maneuver in larger type II curves in order to preserve spinal balance and avoid extension of instrumentation into the middle or lower lumbar spine.