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

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.