title: Understanding how axial loads on the spine influence segmental biomechanics for idiopathic scoliosis patients: A magnetic resonance imaging study.
abstract: BACKGROUND
  Segmental biomechanics of the scoliotic spine are important since the overall spinal deformity is comprised of the cumulative coronal and axial rotations of individual joints. This study investigates the coronal plane segmental biomechanics for adolescent idiopathic scoliosis patients in response to physiologically relevant axial compression.
  
  
  METHODS
  Individual spinal joint compliance in the coronal plane was measured for a series of 15 idiopathic scoliosis patients using axially loaded magnetic resonance imaging. Each patient was first imaged in the supine position with no axial load, and then again following application of an axial compressive load. Coronal plane disc wedge angles in the unloaded and loaded configurations were measured. Joint moments exerted by the axial compressive load were used to derive estimates of individual joint compliance.
  
  
  RESULTS
  The mean standing major Cobb angle for this patient series was 46°. Mean intra-observer measurement error for endplate inclination was 1.6°. Following loading, initially highly wedged discs demonstrated a smaller change in wedge angle, than less wedged discs for certain spinal levels (+2,+1,-2 relative to the apex, (p<0.05)). Highly wedged discs were observed near the apex of the curve, which corresponded to lower joint compliance in the apical region.
  
  
  CONCLUSIONS
  While individual patients exhibit substantial variability in disc wedge angles and joint compliance, overall there is a pattern of increased disc wedging near the curve apex, and reduced joint compliance in this region. Approaches such as this can provide valuable biomechanical data on in vivo spinal biomechanics of the scoliotic spine, for analysis of deformity progression and surgical planning.
authors.affiliation: Paediatric Spine Research Group, Institute for Health and Biomedical Innovation - Centre for Children's Health Research, Queensland University of Technology and Mater Health Services Ltd., Brisbane, Australia. Electronic address: j2.little@qut.edu.au.
authors.forename: J P
authors.initials: JP
authors.lastname: Little
authors.affiliation: Paediatric Spine Research Group, Institute for Health and Biomedical Innovation - Centre for Children's Health Research, Queensland University of Technology and Mater Health Services Ltd., Brisbane, Australia.
authors.forename: M J
authors.initials: MJ
authors.lastname: Pearcy
authors.affiliation: Paediatric Spine Research Group, Institute for Health and Biomedical Innovation - Centre for Children's Health Research, Queensland University of Technology and Mater Health Services Ltd., Brisbane, Australia.
authors.forename: M T
authors.initials: MT
authors.lastname: Izatt
authors.affiliation: Paediatric Spine Research Group, Institute for Health and Biomedical Innovation - Centre for Children's Health Research, Queensland University of Technology and Mater Health Services Ltd., Brisbane, Australia.
authors.forename: K
authors.initials: K
authors.lastname: Boom
authors.affiliation: Paediatric Spine Research Group, Institute for Health and Biomedical Innovation - Centre for Children's Health Research, Queensland University of Technology and Mater Health Services Ltd., Brisbane, Australia.
authors.forename: R D
authors.initials: RD
authors.lastname: Labrom
authors.affiliation: Paediatric Spine Research Group, Institute for Health and Biomedical Innovation - Centre for Children's Health Research, Queensland University of Technology and Mater Health Services Ltd., Brisbane, Australia.
authors.forename: G N
authors.initials: GN
authors.lastname: Askin
authors.affiliation: Paediatric Spine Research Group, Institute for Health and Biomedical Innovation - Centre for Children's Health Research, Queensland University of Technology and Mater Health Services Ltd., Brisbane, Australia.
authors.forename: C J
authors.initials: CJ
authors.lastname: Adam
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena; D003187:Compliance / Q000502:physiology; D018450:Disease Progression; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D012600:Scoliosis / Q000503:physiopathology*; D013314:Stress, Mechanical; D013904:Thoracic Vertebrae / Q000503:physiopathology*; D016474:Weight-Bearing / Q000502:physiology*
keywords: Adolescent idiopathic scoliosis; Axial loading; Flexibility; Joint compliance; Magnetic resonance imaging; Spine biomechanics