Assessment of spontaneous correction of lumbar curve after fusion of the main thoracic in Lenke 1 adolescent idiopathic scoliosis☆

OBJECTIVE To evaluate the clinical and radiographic response of the lumbar curve after fusion of the main thoracic, in patients with adolescent idiopathic scoliosis of Lenke type 1. METHODS Forty-two patients with Lenke 1 adolescent idiopathic scoliosis who underwent operations via the posterior route with pedicle screws were prospectively evaluated. Clinical measurements (size of the hump and translation of the trunk in the coronal plane, by means of a plumb line) and radiographic measurements (Cobb angle, distal level of arthrodesis, translation of the lumbar apical vertebral and Risser) were made. The evaluations were performed preoperatively, immediately postoperatively and two years after surgery. RESULTS The mean Cobb angle of the main thoracic curve was found to have been corrected by 68.9% and the lumbar curve by 57.1%. Eighty percent of the patients presented improved coronal trunk balance two years after surgery. In four patients, worsening of the plumb line measurements was observed, but there was no need for surgical intervention. Less satisfactory results were observed in patients with lumbar modifier B. CONCLUSIONS In Lenke 1 patients, fusion of the thoracic curve alone provided spontaneous correction of the lumbar curve and led to trunk balance. Less satisfactory results were observed in curves with lumbar modifier B, and this may be related to overcorrection of the main thoracic curve.