A prospective in vivo experimental animal study.
To determine the effects of disc degeneration and variable pulse duration mechanical excitation on dorsoventral lumbar kinematic responses.
In vitro and in vivo biomechanical studies have examined spine kinematics during posteroanterior loading mimicking spinal manipulation therapy (SMT), but few (if any) studies have quantified SMT loading-induced spinal motion responses in the degenerated intervertebral disc.
Fifteen sheep underwent a survival surgical procedure resulting in chronic disc degeneration of the L1–L2 disc. Ten age- and weight-matched animals served as controls. Uniform pulse dorsoventral mechanical forces (80 N) were applied to the L3 spinous processes using 10-, 100-, and 200-ms duration pulses mimicking SMT. L3 displacement and L2–L1 acceleration in the control group were compared with the degenerated disc group.
Dorsoventral displacements increased significantly (fivefold, P < 0.001) with increasing mechanical excitation pulse duration (control and degenerated disc groups). Displacements and L2–L1 acceleration transfer were significantly reduced (∼19% and ∼50%, respectively) in the degenerated disc group compared with control (100- and 200-ms pulse duration protocols, P < 0.01).
Dorsoventral vertebral motions are dependent on mechanical excitation pulse duration and are significantly reduced in animals with degenerated discs.
An animal model was used to determine the effect of disc degeneration on dorsoventral vertebral displacement and acceleration responses during mechanical excitations simulating spinal manipulative thrusts. Significant decreases in dorsoventral vertebral displacements and intersegmental accelerations were observed in animals with disc degeneration compared with controls.
From the *Department of Kinesiology, Biomechanics Laboratory, Exercise and Sport Science Research Institute, Arizona State University, Tempe, AZ, and State of the Art Chiropractic Center, Phoenix, AZ; †Departments of Mechanical Engineering and Orthopaedics and Rehabilitation, University of Vermont, Burlington, VT; ‡Adelaide Centre for Spinal Research, Institute of Medical and Veterinary Science, Adelaide, South Australia; §Department of Orthopaedic Surgery, Eeuwfeestkliniek Hospital, Antwerpen, Belgium; and ∥Chiropractic Biophysics Non-profit, Inc., Evanston, WY.
Acknowledgment date: February 15, 2007. Acceptance date: April 2, 2007.
Supported by the Foundation for the Advancement of Chiropractic Education and Chiropractic Biophysics Nonprofit, Inc.
The manuscript submitted does not contain information about medical device(s)/drug(s).
Foundation funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.
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