Estimation of the lumbar curve magnitude with correction of the right thoracic curve in idiopathic scoliosis.

A simple formula was proposed to estimate the magnitude of the postoperative uninstrumented lumbar curve with correction of the right thoracic curve in idiopathic scoliosis. This formula is as follows: PLC < or = LC - 0.5(TC - BTC) (PLC, predicted postoperative standing lumbar Cobb angle; LC, preoperative standing lumbar Cobb angle; TC, preoperative standing thoracic Cobb angle; BTC, preoperative supine lateral bending thoracic Cobb angle). Sixty-five patients' preoperative and postoperative radiographic measurements were taken, and of these 45 had measurements taken after > or = 12 months of follow-up. Multiple regression (R) value for the proposed formula postoperatively was 0.8048 and at > or = 1 year follow-up was 0.6869.