Stabilizing Role of Moments and Pelvic Rotation on the Human Spine in Compression

[+] Author and Article Information
A. Shirazi-Adl

Division of Applied Mechanics, Department of Mechanical Engineering, Ecole Polytechnique, Montreal, Quebec H3C 3A7

M. Parnianpour

Department of Industrial, Welding and Systems Engineering, Ohio State University, Columbus, Ohio 43210

J Biomech Eng 118(1), 26-31 (Feb 01, 1996) (6 pages) doi:10.1115/1.2795942 History: Received February 10, 1994; Revised November 04, 1994; Online October 30, 2007


The mechanisms by which the human spinal column in neutral postures can resist relatively large axial compression forces with no abnormal motions or instabilities remain yet unknown. A nonlinear finite element study of the ligamentous thoracolumbar spine was performed to investigate the stabilizing role of two plausible mechanisms of combined moments and pelvic rotation on the human spine in axial compression. The passive system, by itself was able to carry only a negligible fraction of physiological compression loads without exhibiting large motions. The unconstrained spine was most flexible in the sagittal plane (least stiff plane). The existence of combined moments and pelvic rotation significantly increased the load-bearing capacity of the spine so that the free standing passive thoracolumbar spine resisted the axial compression forces of more than 1000 N with minimal displacements. The former mechanism is much more effective in stabilizing the spine in compression than is the latter one. It is postulated that the pelvic rotation and the off-centered anterior placement of the gravity force are exploited to partially stabilize the passive spine in compression and relieve the musculature. Previous and on-going studies support the validity of the proposed mechanisms.

Copyright © 1996 by The American Society of Mechanical Engineers
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