• Hirofumi Bekki, Katsumi Harimaya, Yoshihiro Matsumoto, Kenichi Kawaguchi, Mitsumasa Hayashida, Seiji Okada, Toshio Doi, and Yasuharu Nakashima.
• Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
• Asian Spine J. 2018 Aug 1; 12 (4): 632-638.

Study DesignProspective cohort study.PurposeThe present study aimed to evaluate the difference in the preoperative curve flexibility between the supine and prone positions in patients with adolescent idiopathic scoliosis (AIS).Overview Of LiteratureIn AIS, a side-bending view is necessary to differentiate a structural curve from a nonstructural curve using the Lenke classification system. However, there are no published studies about which position, supine or prone, is more effective when evaluating preoperative curve flexibility using side-bending X-ray images in AIS patients.MethodsRadiographs were analyzed for 32 AIS patients (26 females, six males) who underwent posterior correction and fusion of their main thoracic (MT) curves. Cobb angles of MT, proximal thoracic (PT), and thoracolumbar/lumbar (TL/L) curves were measured preoperatively using upright, supine (anteroposterior and side-bending), and prone (posteroanterior and side-bending) X-rays.ResultsThe average Cobb angles of PT, MT, and TL/L curves on preoperative upright/supine/prone X-rays were 29.1°/26.7°/26.6°, 60.7°/48.5°/48.2°, and 41.0°/32.6°/33.1°, respectively. The average Cobb angles of PT, MT, and TL/L curves on supine/prone sidebending X-rays were 19.2°/20.3°, 36.3°/36.4°, and 13.9°/15.7°, respectively. The flexibility rates of PT, MT, and TL/L curves in supine/prone positions were 35.3%/32.5%, 40.6%/40.2%, and 71.7%/68.2%, respectively. Comparing flexibility rates in the prone position with those in the supine position in each case, the average ratios of PT, MT, and TL/L curves were found to be 1.0, 1.0, and 0.9, respectively. There were no statistically significant differences between supine and prone side-bending X-ray measurements. However, the Lenke classification in six of 32 patients (18.8%) differed between supine and prone positions because the TL/L curve in the supine position was slightly more flexible than in the prone position.ConclusionsSupine side-bending films may be suitable for the evaluation of preoperative curve flexibility in AIS, especially for lumbar modifier C.

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