title: Chest cage angle difference and rotation of main thoracic curve are independent risk factors of postoperative shoulder imbalance in surgically treated patients with adolescent idiopathic scoliosis.
abstract: METHODS
  Retrospective case series of surgically treated adolescent patients with scoliosis.
  
  
  OBJECTIVE
  To assess the prevalence and independent risk factors for postoperative shoulder imbalance in surgically treated adolescent patients with idiopathic scoliosis.
  
  
  BACKGROUND
  Despite recent reports that have identified risk factors for postoperative shoulder imbalance, the relative risks remain unclear.
  
  
  METHODS
  A retrospective review of 85 consecutive patients treated with thoracic fusion with a minimum 2-year follow-up (mean, 3.1 yr) was conducted to investigate the patient radiographical measurements and demographics. Shoulder height difference (SHD) was measured as the graded height difference of the soft tissue shadows. A SHD more than 2 cm indicated an unbalanced shoulder. Patient demographics and radiographical data were studied to determine risk factors for postoperative SHD. The potential risk factors included age, sex, Risser sign, Cobb angle, flexibility, and apical vertebral rotation (AVR) of the main curve, upper-instrumented vertebra level, SHD, and clavicle chest cage angle difference (CCAD). Univariate and multivariate logistic regression analyses were performed to determine the independent risk factors for postoperative shoulder imbalance.
  
  
  RESULTS
  Of the 85 patients, 21 patients presented postoperative shoulder imbalance. The univariate analysis indicated age, Risser sign, Cobb angle of the main curve, AVR of the main curve, and CCAD as risk factors, but the multivariate logistic regression analysis showed that only AVR of the main curve and CCAD were independent risk factors for postoperative shoulder imbalance (AVR, P = 0.04, odds ratio (OR): 3.54; CCAD, P = 0.01, OR: 5.10).
  
  
  CONCLUSIONS
  Postoperative shoulder imbalance was observed in 25% of the surgically treated adolescent patients. The CCAD and AVR of the main thoracic curve were independent risk factors for postoperative shoulder imbalance in surgically treated patients with adolescent idiopathic scoliosis. The significant correlation between CCAD and postoperative shoulder imbalance seen in this study strongly suggests that the relationship of the shoulder girdle and chest cage has a role in maintaining shoulder balance.
authors.affiliation: From the Department of Orthopedic Surgery, National Center for Musculoskeletal Disorders Murayama Medical Center, Tokyo, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Yagi
authors.forename: Masakazu
authors.initials: M
authors.lastname: Takemitsu
authors.forename: Masafumi
authors.initials: M
authors.lastname: Machida
mesh_terms: D000293:Adolescent; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D011183:Postoperative Complications / Q000175:diagnosis* / Q000453:epidemiology; D004856:Postural Balance / Q000502:physiology; D011446:Prospective Studies; D012189:Retrospective Studies; D012307:Risk Factors; D012399:Rotation; D012600:Scoliosis / Q000175:diagnosis / Q000453:epidemiology / Q000601:surgery*; D012782:Shoulder / Q000473:pathology* / Q000502:physiology; D013123:Spinal Fusion / Q000009:adverse effects; D013904:Thoracic Vertebrae / Q000473:pathology / Q000601:surgery*; D016896:Treatment Outcome; D055815:Young Adult