title: The biomechanical effects of spinal fusion on the sacral loading in adolescent idiopathic scoliosis.
abstract: BACKGROUND
  Posterior spinal surgical correction is performed to correct spinal deformities in adolescent idiopathic scoliosis. Although the relative spino-pelvic alignment changes after spinal surgery, pelvis remains unfused in idiopathic scoliosis surgery. The impact of the spinal fusion on the transferred load to the pelvis via sacrum is not documented in the scoliotic subgroups.
  
  
  METHODS
  Bi-planar radiographs of 9 scoliotic subjects before and in average 16 months after spinal instrumentation surgery, and 12 controls were selected retrospectively. Patient-specific 3D reconstruction and finite element models of the spine, ribcage, and pelvis were developed. Spinal parameters (Cobb angles, kyphosis, lordosis), sacro-pelvic parameters (pelvic incidence, pelvic tilt, sacral slope), frontal and sagittal balances, the position of the trunk center of mass, and the centroid of the stress distribution on the sacrum superior endplate were measured and computed before operation and in the last follow-up.
  
  
  RESULTS
  The position of the stress distribution centroid on the sacrum superior endplate with respect to the central hip vertical axis was significantly different between pre-operative and post-operative patients p<0.05. The distance between the anterior-posterior position of the trunk center of mass and the center of pressure on the superior sacral endplate significantly decreased after the spinal surgery p<0.05.
  
  
  CONCLUSIONS
  The impact of the scoliosis spinal fusion on the transferred load between the spine and pelvis was evaluated. The biomechanical loading of the sacrum endplate was related to the post-operative postural balance and compensatory changes in the spino-pelvic alignment after scoliosis surgery.
authors.affiliation: Dept. Mechanical Engineering, École Polytechnique Montréal, P.O. Box 6079, Station "Centre-ville", Montréal, Québec H3C 3A7, Canada; Research Center, Sainte-Justine University Hospital Center, 3175, Cote Sainte-Catherine Road, Montréal, Québec H3T 1C5, Canada.
authors.forename: Saba
authors.initials: S
authors.lastname: Pasha
authors.affiliation: Dept. Mechanical Engineering, École Polytechnique Montréal, P.O. Box 6079, Station "Centre-ville", Montréal, Québec H3C 3A7, Canada; Research Center, Sainte-Justine University Hospital Center, 3175, Cote Sainte-Catherine Road, Montréal, Québec H3T 1C5, Canada; Department of Surgery, Université de Montréal, C.P. 6128, station "Centre-ville", Montréal, Québec H3C 3J7, Canada. Electronic address: carl-eric.aubin@polymtl.ca.
authors.forename: Carl-Eric
authors.initials: CE
authors.lastname: Aubin
authors.affiliation: Research Center, Sainte-Justine University Hospital Center, 3175, Cote Sainte-Catherine Road, Montréal, Québec H3T 1C5, Canada; Department of Surgery, Université de Montréal, C.P. 6128, station "Centre-ville", Montréal, Québec H3C 3J7, Canada.
authors.forename: Hubert
authors.initials: H
authors.lastname: Labelle
authors.affiliation: Research Center, Sainte-Justine University Hospital Center, 3175, Cote Sainte-Catherine Road, Montréal, Québec H3T 1C5, Canada; Department of Surgery, Université de Montréal, C.P. 6128, station "Centre-ville", Montréal, Québec H3C 3J7, Canada.
authors.forename: Stefan
authors.initials: S
authors.lastname: Parent
authors.affiliation: Research Center, Sainte-Justine University Hospital Center, 3175, Cote Sainte-Catherine Road, Montréal, Québec H3T 1C5, Canada; Department of Surgery, Université de Montréal, C.P. 6128, station "Centre-ville", Montréal, Québec H3C 3J7, Canada; Division of Orthopedic Surgery, Hôpital du Sacré-Coeur de Montréal, 5400 Gouin Ouest, Montréal, Québec H4J 1C5, Canada.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Mac-Thiong
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010388:Pelvis / Q000502:physiology* / Q000601:surgery; D004856:Postural Balance; D011312:Pressure; D012189:Retrospective Studies; D012447:Sacrum / Q000502:physiology* / Q000601:surgery; D012600:Scoliosis / Q000503:physiopathology* / Q000601:surgery*; D013123:Spinal Fusion; D016474:Weight-Bearing
keywords: Biomechanics; Finite element model; Pelvis; Sacrum; Scoliosis; Spinal fusion; Spine