Articles   |    
Noninvasive Imaging Predicts Failure Load of the Spine with Simulated Osteolytic Defects*†
Kelli M. Whealan, M.S.‡; S. Daniel Kwak, Ph.D.§; John R. Tedrow, M.Eng.§; Kaoru Inoue, Ph.D.#; Brian D. Snyder, M.D., Ph.D.**
View Disclosures and Other Information
Investigation performed at the Orthopedic Biomechanics Laboratory, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Funds were received in total or partial support of the research or clinical study presented in this article. The funding sources were the Whitaker Foundation, National Institutes of Health Grant CA 40211-11, and the Children's Orthopaedic Surgery Foundation.
†Read in part at the Annual Meeting of the Orthopaedic Research Society, Anaheim, California, February 3, 1999, and the Summer Bioengineering Conference of the American Society of Mechanical Engineers, Big Sky, Montana, 1999.
‡NuVasive, 10065 Old Grove Road, San Diego, California 92131.
§Orthopedic Biomechanics Laboratory, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, RN 115, Boston, Massachusetts 02215.
#Department of Occupational Therapy, College of Medical Technology, Hokkaido University, 060-0812 Sapporo, Japan.
**Department of Orthopaedic Surgery, Children's Hospital, Hunnewell 2, 300 Longwood Avenue, Boston, Massachusetts 02115. E-mail address: snyder_b@a1.tch.harvard.edu.

J Bone Joint Surg Am, 2000 Sep 01;82(9):1240-1240
5 Recommendations (Recommend) | 3 Comments | Saved by 3 Users Save Case


Background: The clinical management of lytic tumors of the spine is currently based on geometric measurements of the defect. However, the mechanical behavior of a structure depends on both its material and its geometric properties. Quantitative computed tomography and dual-energy x-ray absorptiometry were investigated as noninvasive tools for measuring the material and geometric properties of vertebrae with a simulated lytic defect. From these measures, yield loads were predicted with use of composite beam theory.

Methods: Thirty-four fresh-frozen cadaveric spines were segmented into functional spinal units of three vertebral bodies with two intervertebral discs at the thoracic and lumbar levels. Lytic defects of equal size were created in one of three locations: the anterior, lateral, or posterior region of the vertebra. Each spinal unit was scanned with use of computed tomography and dual-energy x-ray absorptiometry, and axial and bending rigidities were calculated from the image data. Each specimen was brought to failure under combined compression and forward flexion, and the axial load and bending moment at yield were recorded.

Results: Although the relative defect size was nearly constant, measured yield loads had a large dispersion, suggesting that defect size alone was a poor predictor of failure. However, image-derived measures of structural rigidity correlated moderately well with measured yield loads. Furthermore, with use of composite beam theory with quantitative computed tomography-derived rigidities, vertebral yield loads were predicted on a one-to-one basis (concordance, rc = 0.74).

Conclusions: Although current clinical guidelines for predicting fracture risk are based on geometric measurements of the defect, we have shown that the relative size of the defect alone does not account for the variation in vertebral yield loads. However, composite beam theory analysis with quantitative computed tomography-derived measures of rigidity can be used to prospectively predict the yield loads of vertebrae with lytic defects.

Clinical Relevance: Image-predicted vertebral yield loads and analytical models that approximate loads applied to the spine during activities of daily living can be used to calculate a factor of fracture risk that can be employed by physicians to plan appropriate treatment or intervention.

Figures in this Article
    Sign In to Your Personal ProfileSign In To Access Full Content
    Not a Subscriber?
    Get online access for 30 days for $35
    New to JBJS?
    Sign up for a full subscription to both the print and online editions
    Register for a FREE limited account to get full access to all CME activities, to comment on public articles, or to sign up for alerts.
    Register for a FREE limited account to get full access to all CME activities
    Have a subscription to the print edition?
    Current subscribers to The Journal of Bone & Joint Surgery in either the print or quarterly DVD formats receive free online access to JBJS.org.
    Forgot your password?
    Enter your username and email address. We'll send you a reminder to the email address on record.

    Forgot your username or need assistance? Please contact customer service at subs@jbjs.org. If your access is provided
    by your institution, please contact you librarian or administrator for username and password information. Institutional
    administrators, to reset your institution's master username or password, please contact subs@jbjs.org


    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.
    CME Activities Associated with This Article
    Submit a Comment
    Please read the other comments before you post yours. Contributors must reveal any conflict of interest.
    Comments are moderated and will appear on the site at the discretion of JBJS editorial staff.

    * = Required Field
    (if multiple authors, separate names by comma)
    Example: John Doe

    Related Content
    The Journal of Bone & Joint Surgery
    JBJS Case Connector
    Topic Collections
    Related Audio and Videos
    Clinical Trials
    Readers of This Also Read...
    JBJS Jobs
    S. Carolina - Department of Orthopaedic Surgery Medical Univerity of South Carlonina
    Louisiana - Ochsner Health System
    California - UCLA/OH Department of Orthopaedic Surgery
    Pennsylvania - Penn State Milton S. Hershey Medical Center