title: Preoperative pelvic axial rotation: a possible predictor for postoperative coronal decompensation in thoracolumbar/lumbar adolescent idiopathic scoliosis.
abstract: BACKGROUND
  The pelvis as the biomechanical foundation of spine, plays an important role in the balance of the stance and gait through the multi-link spinal-pelvic system. If the pelvic axial rotation (PAR) exists in adolescent idiopathic scoliosis (AIS) patients, it should theoretically have some effects on the body balance.
  
  
  OBJECTIVE
  To explore the probable effects of preoperative PAR on the spinal balance in coronal plane in AIS patients with main thoracolumbar/lumbar (TL/L) curve after posterior spinal instrumentation.
  
  
  METHODS
  Thirty-eight AIS patients (age: 15 ± 1.5 years) with main TL/L curve (51° ± 6.2°) were recruited retrospectively into this study. The mean follow-up period was 27 months (24-36 months). Standing full spine posteroanterior radiographs were taken preoperatively, 3 month and 1 year postoperatively, and at last follow-up. The convex/concave ratio (CV/CC ratio) of the anterior superior iliac spine laterally and the inferior ilium at the sacroiliac joint medially was measured on posteroanterior radiographs. According to the preoperative CV/CC ratios, the patients were divided into two groups: normal group (N-group: 0.95 ≤ CV/CC ≤ 1.05); and the asymmetrical group (A-group: CV/CC < 0.95, or >1.05).
  
  
  RESULTS
  In all the patients, the 3-month-postoperative CV/CC ratio (1.026 ± 0.087) was significantly different from the preoperative CV/CC ratio (0.969 ± 0.095, P < 0.001), indicating that the pelvis had rotated in the opposite direction of the corrective derotation load applied to the TL/L spine after surgery. No significant change was found in the CV/CC ratio from 3-month-postoperative to the last follow-up (1.013 ± 0.103, P > 0.05). There was no significant difference in the demographic, phenotypic, and treatment variables between the N- (n = 16) and A-groups (n = 22) (P > 0.05). However, more coronal decompensation occurred in the A-group after surgery (36.4 vs. 0.0 %, P = 0.013): two patients having trunk translation, three having lower instrumented vertebra (LIV) translation, and one having LIV tilt; meanwhile, one patient having both LIV translation and LIV tilt, and one having both trunk translation and LIV tilt.
  
  
  CONCLUSIONS
  The present study confirmed the existence of PAR in AIS patients, and indicated that the pelvis would experience an active rebalancing in the transverse plane within 3 months after spinal correction, and since then, its position would remain stable. Moreover, TL/L-AIS patients with preoperative asymmetrical PAR probably had greater risk of coronal decompensation postoperatively.
authors: Spine Surgery, Drum Tower Hospital, Nanjing University Medical School, No.321, Zhongshan Road, 210008, Nanjing, China.
authors: Xu-Sheng
authors: XS
authors: Qiu
authors: Zhi-Wei
authors: ZW
authors: Wang
authors: Yong
authors: Y
authors: Qiu
authors: Wei-Jun
authors: WJ
authors: Wang
authors: Sai-Hu
authors: SH
authors: Mao
authors: Ze-Zhang
authors: ZZ
authors: Zhu
authors: Bang-ping
authors: BP
authors: Qian
authors: Shou-Feng
authors: SF
authors: Wang
authors: Feng
authors: F
authors: Zhu
authors: Jun
authors: J
authors: Qiao
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D010388:Pelvis / Q000000981:diagnostic imaging*; D011300:Preoperative Care; D011859:Radiography; D012189:Retrospective Studies; D012399:Rotation; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000601:surgery*; D013123:Spinal Fusion; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D016896:Treatment Outcome
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