title: Three-dimensional characterization of torsion and asymmetry of the intervertebral discs versus vertebral bodies in adolescent idiopathic scoliosis.
abstract: METHODS
  Cross-sectional study.
  
  
  OBJECTIVE
  To compare the relative contribution of the vertebral bodies and intervertebral discs with the 3-dimensional spinal deformity in adolescent idiopathic scoliosis.
  
  
  BACKGROUND
  There is an ongoing discussion about the causal role of skeletal growth processes in the etiopathogenesis of adolescent idiopathic scoliosis. Contradictory findings have been reported on the individual contribution of the vertebral bodies as compared with the discs to the coronal deformity. As far as we know, the true 3-dimensional deformity of the discs and vertebral bodies have not yet been described.
  
  
  METHODS
  High-resolution computed tomographic scans of 77 patients with severe adolescent idiopathic scoliosis were included. Torsion and anterior-posterior and right-left asymmetry of each individual vertebral body and intervertebral disc were studied from T2 to L5, using semiautomatic analysis software. True transverse sections were reconstructed along the anterior-posterior and right-left axis of all endplates. These "endplate-vectors" were calculated semiautomatically, taking rotation and tilt into account. Torsion was defined as the difference in axial rotation between 2 subsequent endplates. Asymmetry was defined as the relative anterior-posterior or right-left height difference of the discs and the vertebrae.
  
  
  RESULTS
  There were at least 3 times more torsion, anterior overgrowth, and coronal wedging in the discs than in the vertebrae in the thoracic as well as in the (thoraco) lumbar curves (P<0.001). These values correlated significantly with the Cobb angle (r≥0.37; P<0.001). Anterior overgrowth and coronal asymmetry were greater in the apical regions whereas torsion was most pronounced in the transitional segments between the curves.
  
  
  CONCLUSIONS
  The discs contribute more to 3-D deformity than the bony structures, and there is significant regional variability. This suggests an adaptive rather than an active phenomenon.
  
  
  METHODS
  2.
authors.affiliation: *Department of Orthopedic Surgery, University Medical Center Utrecht, Utrecht, the Netherlands †Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands; and ‡Departments of Diagnostic Radiology and Organ Imaging and §Orthopaedics and Traumatology, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Tom P C
authors.initials: TP
authors.lastname: Schlösser
authors.forename: Marijn
authors.initials: M
authors.lastname: van Stralen
authors.forename: Rob C
authors.initials: RC
authors.lastname: Brink
authors.forename: Winnie C W
authors.initials: WC
authors.lastname: Chu
authors.forename: Tsz-Ping
authors.initials: TP
authors.lastname: Lam
authors.forename: Koen L
authors.initials: KL
authors.lastname: Vincken
authors.forename: René M
authors.initials: RM
authors.lastname: Castelein
authors.forename: Jack C Y
authors.initials: JC
authors.lastname: Cheng
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D000886:Anthropometry; D002648:Child; D018450:Disease Progression; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000473:pathology*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology*; D008297:Male; D015203:Reproducibility of Results; D012399:Rotation; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000473:pathology*; D012720:Severity of Illness Index; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology*; D014057:Tomography, X-Ray Computed; D055815:Young Adult