A long thoracolumbar sagittal rectitude is sometimes present in adolescent idiopathic scoliosis. The purpose of this study was to identify typical patterns, by comparing frontal plane deformities and vertebral rotation leading to this rectitude. Surgical thoracolumbar alignment correction by three-dimensional in situ bending of rods was then analyzed. Pre- and postoperative radiographs of 24 patients with scoliosis (36–104 degrees) were reviewed using Spineview software. Frontal curves and levels of sagittal rectitude were determined. Thoracic kyphosis, lumbar lordosis, sacral slope, pelvic incidence, pelvic tilt, T9 and T1 tilt were measured. Vertebral rotation was measured by computed tomography, Perdriolle's, Nash and Moe's methods. The intervertebral mobility of the rectitude was analyzed on side bending radiographs. Three patterns leading to sagittal rectitude were identified: 11 main thoracic curves (Lenke 1, King 3) with cranial prolongation of the physiological thoracolumbar junction (T7T12) and maximal vertebral rotation above this zone, 13 double major or thoracolumbar curves (Lenke 3 or 5, King 1 or 2) with cranial and caudal prolongation (T9L3) and maximal rotation above and below, 1 lumbar curve (Lenke 5) with caudal rectitude (T12L4) and maximal rotation at L1. There was no relationship between intervertebral mobility and rectitude. Postoperatively, this zone of rectitude disappeared in 17 out of 24 patients after anterior release followed by posterior instrumentation using the in situ bending technique. In situ bending realizes a stepwise correction of the three-dimensional deformity at different levels. An accurate preoperative analysis is mandatory to achieve an adequate sagittal balance, frontal curve correction and vertebral derotation simultaneously. The determined patterns of thoracolumbar rectitude are helpful to plan surgical correction accurately.