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Volume 42 Number 2, March/April 2005
Pages 167 — 174

Abstract - Bending stiffness of the lumbar spine subjected to posteroanterior manipulative force

Raymond Y. W. Lee, PhD;1* Bonnie Y. S. Tsung, MPhil;1 Pin Tong, PhD;2 John Evans, PhD3

1Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong; 2Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Hong Kong; 3Centre for Rehabilitation Science and Engineering, Queensland University of Technology, Queensland, Australia
Abstract — This study measured the bending stiffness of the spine when it is subjected to posteroanterior mobilization force. The lumbar spine was modeled as an initially curved beam column supported over the rib cage and the pelvis. Posteroanterior mobilization was assumed to be three-point bending of the beam. The mobilization force was measured by the mounting of a force plate onto the manipulation couch, where electromagnetic sensors measured the change in spinal curvature. The bending stiffness of the spine was derived from the force and curvature data. The technique developed in this study provided highly repeatable data. The theoretical analysis suggests that the pelvic rotation produced by mobilization may be used clinically to indicate the magnitude of the mobilization force. Future research may employ the present method to determine how back pain may affect the bending stiffness of the spine. The bending stiffness values reported in this study will be valuable to future modeling work.
Key words: back pain, beam analysis, biomechanics, manipulation, physiotherapy, posteroanterior mobilization, rehabilitation, spine, stiffness, three-point bending.

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