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Assessment of Three-Dimensional Lumbar Spine Vertebral Motion During Gait with Use of Indwelling Bone Pins
Bruce A. MacWilliams, PhD1; Adam Rozumalski, MS3; Andrew N. Swanson, MD2; Roy A. Wervey, BS3; Daryll C. Dykes, MD, PhD4; Tom F. Novacheck, MD3; Michael H. Schwartz, PhD3
1 Motion Analysis Laboratory, Shriners Hospitals for Children-Salt Lake City, Fairfax Road at Virginia Street, Salt Lake City, UT 84103. E-mail address: bmacwilliams@shrinenet.org
3 Gillette Children’s Specialty Healthcare, 200 East University Avenue, St. Paul, MN 55101
2 Deceased.
4 Twin Cities Spine Center, 913 East 26th Street, #600, Minneapolis, MN 55404
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Investigation performed at Gillette Children’s Specialty Healthcare, St. Paul, Minnesota

Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

Copyright © 2013 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2013 Dec 04;95(23):e184 1-8. doi: 10.2106/JBJS.L.01469
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This study quantifies the three-dimensional motion of lumbar vertebrae during gait via direct in vivo measurement with the use of indwelling bone pins with retroreflective markers and motion capture. Two previous studies in which bone pins were used were limited to instrumentation of two vertebrae, and neither evaluated motions during gait. While several imaging-based studies of spinal motion have been reported, the restrictions in measurement volume that are inherent to imaging modalities are not conducive to gait applications.


Eight healthy volunteers with a mean age of 25.1 years were screened to rule out pathology. Then, after local anesthesia was administered, two 1.6-mm Kirschner wires were inserted into the L1, L2, L3, L4, L5, and S1 spinous processes. The wires were clamped together, and reflective marker triads were attached to the end of each wire couple. Subjects underwent spinal computed tomography to anatomically register each vertebra to the attached triad. Subjects then walked several times in a calibrated measurement field at a self-selected speed while motion data were collected.


Less than 4° of lumbar intersegmental motion was found in all planes. Motions were highly consistent between subjects, resulting in small group standard deviations. The largest motions were in the coronal plane, and the middle lumbar segments exhibited greater motions than the segments cephalad and caudad to them. Intersegmental lumbar flexion and axial rotation motions were both extremely small at all levels.


The lumbar spine chiefly acts to contribute abduction during stance and adduction during swing to balance the relative motions between the trunk and pelvis. The lumbar spine acts in concert with the thoracic spine. While the lumbar spine chiefly contributes coronal plane motion, the thoracic spine contributes the majority of the transverse plane motion. Both contribute flexion motion in an offset phase pattern.

Clinical Relevance: 

This is a valid model for measuring the three-dimensional motion of the spine. Normative data were obtained to better understand the effects of spine disorders on vertebral motion over the gait cycle.

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    Accreditation Statement
    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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    Bruce MacWilliams PhD (1), Michael Schwartz PhD (2)
    Posted on December 30, 2013
    Response to comment: Recruitment of Study Subjects
    (1) Shriners Hospital for Children, Salt Lake City, UT, (2) Twin Cities Spine Center, Minneapolis, MN

    Subjects were compensated for their participation. All aspects of the study, including compensation, were approved by the University of Minnesota IRB. As investigators, we were acutely aware of the invasive and somewhat “dramatic” nature of the study. As a result, we took every possible precaution to be certain that our procedures (including compensation) were carefully reviewed and approved by the IRB. We also were extremely open and direct with the participants regarding the study risks, the fact that participation was entirely voluntary, and that they were free to withdraw at any time during the study.

    Recruitment was very easy. We had all the volunteers we needed within a few weeks, and even ended up with a waiting list. As it turned out, many of the participants were, in fact, interested in knowing more about vertebral motion. Almost all of the participants worked in the spine healthcare field. Due to the places where we advertised the study, we ended drawing a highly knowledgeable and curious set of participants, including surgical nurses, clinical staff from spine treatment center, and people interested in spine biomechanics. The fact that our participants knew so much about what they were volunteering for was reassuring to us. We felt certain that the volunteers were well informed about the risks of the study, and were free of coercion, despite the financial compensation. We are firmly committed to the ethical principles of autonomy, beneficence, and justice that guide research involving human subjects.

    We conducted a follow-up survey with the participants 1 – 2 years after the study. Overwhelmingly, the participants remained supportive of the study, and did not regret their decision to participate.

    Joseph Gerardi, MD
    Posted on December 16, 2013
    Recruitment of Study Subjects
    Children's Hospital Central California, Madera, California, USA

    I am curious as to how the subjects were recruited. Were they paid? Were they simply very curious about vertebral motion and gait?

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