April 2002

CBP® N.P. Supported Study Accepted in Clinical Biomechanics

Model Predicts Spinal Motions During Chiropractic Adjustments

by Christopher J. Colloca, D.C.

In early 2002, Dr. Kim Burton, editor of the journal Clinical Biomechanics, informed Dr. Tony Keller and Dr. Chris Colloca that their paper had been accepted for publication in the journal.  The paper is entitled “Force-deformation response of the lumbar spine: a sagittal plane model of posteroanterior manipulation and mobilization.”, by Keller TS, Colloca CJ, and Beliveau. Clinical Biomechanics is a peer-reviewed indexed international multidisciplinary journal of musculoskeletal biomechanics, affiliated to the American Society of Biomechanics, and the International Society of Biomechanics.  The study was first presented at the Sixth Biennial World Federation of Chiropractic in Paris, France, May 21-26, 2001.

                In the study, lead author Tony Keller, Ph.D., Associate professor and Chair of the Department of Mechanical Engineering at the University of Vermont, developed a mathematical model that predicts spinal motions occurring during chiropractic adjustments.  Such modeling is important in understanding how vertebrae move during chiropractic adjustments to improve chiropractic techniques in the application of forces to the spine.  Additionally, this type of modeling can provide the objective evidence that is needed in protecting chiropractors from allegations of iatrogenic injury resulting from spinal manipulation / chiropractic adjustments.

The model originated from a sagittal plane 5 degree-of-freedom (DOF) model that was presented at the 2000 meeting of the European Society of Biomechanics, Dublin, Ireland.  The 5 DOF model accounted for the posteroanterior (PA) motion response of five lumbar vertebrae which is in press at the Journal of Manipulative & Physiological Therapeutics scheduled to appear later this year.  The current study amassed to 21 DOF by adding thorax and pelvic sections to the five lumbar vertebrae and modeling the coupled flexion-extension rotation, axial (cranial-caudal) and transverse or posteroanterior (PA) vertebral and intervertebral motion response of the lumbar spine, pelvis and thorax of prone-lying subjects.  Applying original data collected from published literature and the author’s own research on spinal movement, the results are presented for static, oscillatory and impulsive forces in the study (Figure 1).

Dr. Colloca sums up the relevance of this research in saying, “In chiropractic, we use a variety of techniques to apply forces to the spine.  Understanding what type of force to use on what type of patient is of great interest to researchers and clinicians alike.  Some chiropractors rely on side posture, or PA lumbar thrusts performed in the knee-chest position, in addition to Drop-table, or instrument delivered thrusts.  Modeling how the spine will react to these different kinds of forces helps us to improve our chiropractic technique.  Our research has shown that the spine doesn’t move the way that we were traditionally taught in school, but rather coupled motions occur dependent upon the spinal morphology.  The traditional chiropractic listing system and paradigm of adjusting will dramatically change this decade.  It’s exciting to be involved in this transformation of chiropractic technique.”

Drs. Keller and Colloca continue to collect data from human subjects to validate this spinal model with research occurring in the U.S. and Europe.  Currently the model is being expanded to 72 degrees-of-freedom to investigate the spine’s motion during adjustments in other planes.  Continued improvements to a three-dimensional model and the neurophysiological effects of said responses are now underway.  This research was supported, in part, from a grant from Dr. William Harris through the Foundation for the Advancement of Chiropractic Education, the National Institute of Chiropractic Research, and Chiropractic Biophysics, Non-profit, Inc.

Figure 1.  Graphical simulation of the lumbar segmental motion response to an impulsive dynamic force at L3 with an anterior-superior line of drive.  Panels (left to right, top to bottom) show 0.5 millisecond interval motion responses starting at time 0.  Axial displacement, posterior-anterior displacement, and flexion-extension rotation have been magnified by factors of 10x, 10x and 5x, respectively so motions can be visualized.  Significant spinal coupling between vertebrae are seen as the PA displacement-time history and corresponding time point (last open circle) for each figure are observed