title: Association between Sacral Slanting and Adjacent Structures in Patients with Adolescent Idiopathic Scoliosis.
abstract: BACKGROUND
  Sacral slanting is a frequent unique phenomenon in patients with adolescent idiopathic scoliosis (AIS) and may be important for selecting the distal fusion level. However, the reason of the phenomenon remains unknown. The purpose of this study was to determine the association between sacral slanting and adjacent structures in patients with AIS.
  
  
  METHODS
  A total of 303 AIS patients who underwent both whole spine standing anteroposterior (AP) and whole leg standing AP radiography were included. The degree of sacral slanting, pelvic obliquity, lumbar curve angles (L1-L4), and L4 tilt were assessed on whole spine standing AP radiographs. Whole leg standing AP radiographs were used to assess the degree of leg length discrepancy (LLD). Demographic data and radiological parameters were analyzed descriptively. Pearson correlation analysis and partial correlation analysis of the parameters were performed. Ap-value of less than 0.05 was considered statistically significant.
  
  
  RESULTS
  The proportion of patients with ≥ 5° of sacral slanting among those with < 3° of pelvic obliquity was 8.9% (27/303). Thirty-two patients (10.6%, 32/303) showed more than 10 mm of LLD. Sacral slanting was positively correlated with pelvic obliquity and lumbar curve (r= 0.445 andr= 0.325, respectively). Pelvic obliquity was also correlated with LLD and L4 tilt (r= 0.123 andr= 0.311, respectively). However, partial correlation analysis showed that LLD was not directly correlated with sacral slanting (r= -0.034).
  
  
  CONCLUSIONS
  Sacral slanting can be thought to be a compensatory mechanism for large lumbar curves, which is accompanied by pelvic obliquity. In contrast, a congenitally slanted upper sacrum may contribute to scoliosis in some cases. LLD was not directly correlated with sacral slanting.
authors.affiliation: Department of Orthopedic Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jae Hwan
authors.initials: JH
authors.lastname: Cho
authors.affiliation: Department of Orthopedic Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Choon Sung
authors.initials: CS
authors.lastname: Lee
authors.affiliation: Department of Orthopedic Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Youn-Suk
authors.initials: YS
authors.lastname: Joo
authors.affiliation: Department of Orthopedic Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jungu
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Orthopedic Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Chang Ju
authors.initials: CJ
authors.lastname: Hwang
authors.affiliation: Department of Orthopedic Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Dong-Ho
authors.initials: DH
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena; D002648:Child; D005260:Female; D006801:Humans; D007870:Leg Length Inequality / Q000209:etiology; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008161:Lumbosacral Region / Q000000981:diagnostic imaging*; D008297:Male; D010384:Pelvic Bones / Q000000981:diagnostic imaging*; D011859:Radiography; D012447:Sacrum / Q000000981:diagnostic imaging*; D012600:Scoliosis / Q000150:complications / Q000000981:diagnostic imaging*
keywords: Adolescent; Leg length inequality; Pelvis; Sacrum; Scoliosis