• Xi Yang, Limin Liu, Yueming Song, Chunguang Zhou, Zhongjie Zhou, Lei Wang, and Liang Wang.
• From the Department of Orthopedic Surgery, West China Hospital, Sichuan University, Chengdu, China.
• Spine. 2015 Jan 15;40(2):102-8.

Study DesignA retrospective study.ObjectiveTo investigate the preoperative spinopelvic sagittal alignment in Lenke 5 patients with adolescent idiopathic scoliosis (AIS), and analyze how it alters after posterior correction.Summary Of Background DataThe structural thoracolumbar or lumbar curve may change the local sagittal alignment thereby altering the sagittal balance in Lenke 5 patients with AIS. However, few studies have evaluated the spinopelvic sagittal alignment before and after the surgery in these patients.MethodsForty-eight Lenke 5 patients with AIS who underwent posterior correction and fusion were included in this study. Preoperative and postoperative radiographs were reviewed measuring both the coronal and sagittal parameters. Three pelvic sagittal states (anteverted, normal, or retroverted) were evaluated according to the magnitude relationship of individual pelvic tilt with pelvic incidence (PI). Both the coronal and sagittal parameters between different pelvic sagittal states were compared. The alterations of these parameters by surgery would also be analyzed.ResultsThe mean follow-up was 1.8 years. Preoperatively, the mean PI was 44.3° with a pelvic tilt of 4.1°. There was 48% patients showing the anteverted pelvis, whereas the remaining 52% showing normal. The patients with anteverted pelvis showed a smaller PI and more distal lower end vertebra than normal pelvis ones. Logistic regression analysis revealed PI (odds ratio [OR] = 0.62, P = 0.024) and lower end vertebra (OR = 2.1, P = 0.037) were significantly associated with the risk of developing anteverted pelvis. The pelvic tilt was significantly increased and 61% of patients with preoperative anteverted pelvis had recovered. Logistic regression analysis revealed PI (OR = 0.7, P = 0.034) and lower instrumented vertebra (OR = 6.5, P = 0.002) were significantly associated with the risk of postoperative uncovered of anteverted pelvis.ConclusionAnteverted pelvis appears in almost half of Lenke 5 patients with AIS, especially in who have smaller PI or distal lower end vertebra. The abnormal pelvic sagittal state will be generally corrected by posterior correction surgery except for patients with a PI less than 39° or a lower instrumented vertebra that extends to L5.

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