title: Analysis of sagittal alignment in thoracic and thoracolumbar curves in adolescent idiopathic scoliosis: how do these two curve types differ?
abstract: METHODS
  Retrospective chart review and radiographic analysis.
  
  
  OBJECTIVE
  To determine if differences exist in the sagittal alignment of adolescent idiopathic scoliosis (AIS) patients with thoracic versus thoracolumbar curve patterns.
  
  
  BACKGROUND
  Relative anterior overgrowth has been suggested as the possible pathomechanism behind thoracic scoliosis. Given the proposed importance of the sagittal alignment on the development of AIS and the known association between pelvic parameters and sagittal alignment, the authors postulate that pelvic incidence may influence the location of vertebral column collapse associated with different AIS curve types.
  
  
  METHODS
  A multicenter surgical database was used to compare preoperative radiographic measurements between patients with primary thoracic curves (Lenke 1A, B), primary thoracolumbar curves (Lenke 5), and normal adolescents.
  
  
  RESULTS
  Pelvic incidence was significantly greater in both groups of AIS patients compared with normal adolescents. Patients in the primary thoracic curve group were found to have a significantly increased sacral slope and a decreased thoracic kyphosis relative to the control group. Patients in the primary thoracolumbar curve group had a significantly increased pelvic tilt; however, a relatively normal thoracic kyphosis, lumbar lordosis, and sacral slope compared with the respective control values.
  
  
  CONCLUSIONS
  An increased pelvic incidence, associated with both thoracic and thoracolumbar curves when compared with the normal adolescent population, does not appear to be the potential determinant of the development of thoracic versus thoracolumbar scoliosis, but may be a risk factor for the development of adolescent idiopathic scoliosis. The theory of anterior overgrowth may be supported by the identification of thoracic hypokyphosis, despite an increased pelvic incidence and lumbar lordosis, in patients with thoracic scoliosis. The association between sagittal measurements and the etiology of thoracolumbar curve formation is less clear; however, regional anterior overgrowth in the lumbar spine may also be responsible for the deformity.
authors.affiliation: Department of Orthopaedic Surgery, University of California San Diego, San Diego, CA, USA.
authors.forename: Vidyadhar V
authors.initials: VV
authors.lastname: Upasani
authors.forename: John
authors.initials: J
authors.lastname: Tis
authors.forename: Tracey
authors.initials: T
authors.lastname: Bastrom
authors.forename: Jeff
authors.initials: J
authors.lastname: Pawelek
authors.forename: Michelle
authors.initials: M
authors.lastname: Marks
authors.forename: Baron
authors.initials: B
authors.lastname: Lonner
authors.forename: Alvin
authors.initials: A
authors.lastname: Crawford
authors.forename: Peter O
authors.initials: PO
authors.lastname: Newton
mesh_terms: D000293:Adolescent; D002648:Child; D016208:Databases, Factual; D005260:Female; D006801:Humans; D016014:Linear Models; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008297:Male; D010388:Pelvis / Q000000981:diagnostic imaging; D011859:Radiography; D012189:Retrospective Studies; D012307:Risk Factors; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000453:epidemiology; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging*