• Shingo Kuroya, Tsutomu Akazawa, Toshiaki Kotani, Tsuyoshi Sakuma, Shohei Minami, Yoshiaki Torii, Tasuku Umehara, Masahiro Iinuma, Kenichi Murakami, Sumihisa Orita, Kazuhide Inage, Yawara Eguchi, Kazuki Fujimoto, Yasuhiro Shiga, Junichi Nakamura, Gen Inoue, Masayuki Miyagi, Wataru Saito, Seiji Ohtori, and Hisateru Niki.
• Department of Orthopaedic Surgery, St. Marianna University School of Medicine, Kawasaki, Japan.
• Asian Spine J. 2019 Oct 1; 13 (5): 793-800.

Study DesignA retrospective cohort study.PurposeThis study aims to investigate postoperative shoulder imbalance (PSI) ≥5 years postoperatively in patients who underwent posterior spinal fusion using hooks at the upper instrumented vertebra (UIV) for Lenke type 1 adolescent idiopathic scoliosis (AIS).Overview Of LiteratureStudies have reported PSI due to excessive correction of the main thoracic curve.MethodsWe examined 56 patients with AIS who underwent a posterior spinal fusion with hooks at the UIV from 2004 to 2010. Of these, we enrolled 14 patients who underwent surgery, at least, 5 years ago. X-rays and Scoliosis Research Society-22 (SRS-22) questionnaire were administered. To evaluate the shoulder balance, T1 vertebral tilt angle (T1 tilt), clavicle angle, and radiographic shoulder height (RSH) were measured. PSI was considered as the absolute value of the postoperative RSH being ≥20 mm. Based on radiographs obtained immediately postoperatively, we divided patients into two groups as follows: the balanced group (absolute value of RSH <20 mm) and imbalanced group (absolute value of RSH ≥20 mm).ResultsThe frequency of PSI was 28.6% immediately postoperatively, 0% 2 years postoperatively, and 7.1% at the last follow-up. In the balanced group, PSI did not occur even at 2 years postoperatively or at the last follow-up. In the imbalanced group, PSI was improved in all patients 2 years postoperatively and all patients, except one patient, at the last follow-up. No significant differences were noted in the frequency of distal adding-on at 2 years postoperatively or the last follow-up between the balanced group and the imbalanced group. We observed moderate negative correlations between the absolute value of T1 tilt and the SRS-22 pain and satisfaction at the last follow-up.ConclusionsHooks at the UIV could adjust the shoulder balance to avoid long-term PSI in patients with AIS.

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