Convex-Rod Derotation Maneuver on Lenke Type I Adolescent Idiopathic Scoliosis

Abstract BACKGROUND Convex-rod derotation may have potential advantages for adolescent idiopathic scoliosis (AIS) correction; however, study of this technique has been limited. OBJECTIVE To compare the radiographic outcomes of Lenke type I AIS patients treated by the convex- or concave-rod derotation maneuvers. METHODS A retrospective study was designed to compare 2 cohorts, including 81 Lenke type I AIS patients treated with convex-rod derotation (n = 38) or concave-rod derotation (n = 43), between July 2008 and September 2012. All patients had complete clinical records and radiographic data, which were collected and compared between groups. RESULTS In comparing 9 radiographic parameters, significant differences were found in the incidence of screw misplacement, the postoperative main-curve angle, and the corrective rate between groups. The major-curve angles in both the convex- and the concave-rod derotation groups were corrected from 54.0° ± 10.6° and 53.0° ± 11.1° preoperatively, to 8.5° ± 6.9° and 12.9° ± 6.8° postoperatively, with corrective rates of 85.3% and 76.0%, respectively ( P = .001). Final T5-T12 kyphosis and appropriate coronal-to-sagittal balance were achieved in both groups. The incidence of screw misplacement in the convex and concave sides of all patients was 1.8% and 3.7%, respectively ( P = .047), and 1.8% and 3.6%, respectively, in the convex- and the concave-rod derotation groups ( P = .044). CONCLUSION Compared with concave-rod derotation, convex-rod derotation can potentially improve the major-curve corrective rate and tends to reduce the risk of pedicle breach in Lenke type I AIS patients.