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Level-Dependent Coronal and Axial Moment-Rotation Corridors of Degeneration-Free Cervical Spines in Lateral Flexion
Narayan Yoganandan, PhD1; Frank A. Pintar, PhD1; Brian D. Stemper, PhD1; Christopher E. Wolfla, MD1; Barry S. Shender, PhD2; Glenn Paskoff, MS3
1 Department of Neurosurgery, Medical College of Wisconsin, 9200 West Wisconsin Avenue, Milwaukee, WI 53226. E-mail address for N. Yoganandan: yoga@mcw.edu
2 Human Systems Department, NAVAIR, Code 4656, Building 2187, Suite 2280, 48110 Shaw Road, Unit 5, Patuxent River, MD 20670-1906
3 NAVAIR, Code, Building 2187, Suite 1280, 48110 Shaw Road, Unit 5, Patuxent River, MD 20670-1906
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Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants in excess of $10,000 from the Office of Naval Research (contract N00421-02-C-3005) and Veterans Affairs Medical Research. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.
Investigation performed at the Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin

The Journal of Bone and Joint Surgery, Incorporated
J Bone Joint Surg Am, 2007 May 01;89(5):1066-1074. doi: 10.2106/JBJS.F.00200
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Background: Aging, trauma, or degeneration can affect intervertebral kinematics. While in vivo studies can determine motions, moments are not easily quantified. Previous in vitro studies on the cervical spine have largely used specimens from older individuals with varying levels of degeneration and have shown that moment-rotation responses under lateral bending do not vary significantly by spinal level. The objective of the present in vitro biomechanical study was, therefore, to determine the coronal and axial moment-rotation responses of degeneration-free, normal, intact human cadaveric cervicothoracic spinal columns under the lateral bending mode.

Methods: Nine human cadaveric cervical columns from C2 to T1 were fixed at both ends. The donors had ranged from twenty-three to forty-four years old (mean, thirty-four years) at the time of death. Retroreflective targets were inserted into each vertebra to obtain rotational kinematics in the coronal and axial planes. The specimens were subjected to pure lateral bending moment with use of established techniques. The range-of-motion and neutral zone metrics for the coronal and axial rotation components were determined at each level of the spinal column and were evaluated statistically.

Results: Statistical analysis indicated that the two metrics were level-dependent (p < 0.05). Coronal motions were significantly greater (p < 0.05) than axial motions. Moment-rotation responses were nonlinear for both coronal and axial rotation components under lateral bending moments. Each segmental curve for both rotation components was well represented by a logarithmic function (R2 > 0.95).

Conclusions: Range-of-motion metrics compared favorably with those of in vivo investigations. Coronal and axial motions of degeneration-free cervical spinal columns under lateral bending showed substantially different level-dependent responses. The presentation of moment-rotation corridors for both metrics forms a normative dataset for the degeneration-free cervical spines.

Clinical Relevance: While clinical studies provide some information on spinal motions, laboratory-driven experimental biomechanical studies allow controlled load application, document motion magnitudes, and provide a critical dataset of moment-rotation responses. Because these data are derived from degeneration-free spines, validation efforts with use of this dataset will greatly improve model predictabilities while studying the effects of pathological processes, trauma, or instrumentation on spinal kinetics and, hence, stability.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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