Biomechanical loading of the sacrum in adolescent idiopathic scoliosis.
BACKGROUND
The pelvis maintains an important role in transferring loads from the upper body to the lower extremities and hence contributes to the standing postural balance. Even though changes in spino-pelvic relative alignment are involved in the pathophysiology of scoliosis, the mechanism through which the transferred load between the spine and pelvis is related to the spinal deformity is not well understood.


METHODS
A personalized finite element model of the spine and pelvis was constructed for 11 right main thoracic and 23 left thoracolumbar/lumbar adolescent idiopathic scoliosis and 12 asymptomatic controls. The compressive stress distribution on the sacrum endplate was computed. The position of the stress distribution barycenter on the sacrum superior endplate in reference to the central hip vertical axis was projected on the transverse plane and compared between scoliotic subgroups and controls.


RESULTS
The medio-lateral position of the stress distribution barycenter on the sacrum superior endplate was significantly different between the scoliotic subgroups and controls (p<0.05). The stress distribution barycenter on the sacrum superior endplate was located at the right side of the central hip vertical axis in 82% of the right main thoracic patients and to the left side of the central hip vertical axis in 91% of the left thoracolumbar/lumbar patients.


CONCLUSIONS
Analysis of the transferred load to the sacrum provided insight into the biomechanical spino-pelvic interaction in 3D, showing that a thoracolumbar/lumbar scoliotic curve has an increased influence on sacral loads when compared to a main thoracic scoliotic curve.
Department of Mechanical Engineering, Polytechnique Montreal, P.O. Box 6079, Downtown Station, Montréal, Québec, H3C 3A7, Canada; Research Center, Sainte-Justine University Hospital Center, 3175, Cote Sainte-Catherine Road, Montréal, Québec, H3T 1C5, Canada.
Saba
S
Pasha
Department of Mechanical Engineering, Polytechnique Montreal, P.O. Box 6079, Downtown Station, 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.
Carl-Eric
CE
Aubin
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.
Stefan
S
Parent
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.
Hubert
H
Labelle
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.
Jean-Marc
JM
Mac-Thiong
D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D010384:Pelvic Bones / Q000503:physiopathology; D004856:Postural Balance / Q000502:physiology; D011187:Posture / Q000502:physiology; D012447:Sacrum / Q000503:physiopathology*; D012600:Scoliosis / Q000473:pathology / Q000503:physiopathology*; D013131:Spine / Q000503:physiopathology
Finite element simulation; Pelvis; Scoliosis; Spine; Spino-pelvic alignment