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L5/S1 joint info request

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  • L5/S1 joint info request

    Dear BIOMECH-L'ers,

    Recently, our group has been doing some dynamic modeling on the full
    body motions, and are interested in simple mechanical models of the
    lumbar/sacral joint. We have two main questions:

    (1) We are looking for reasonable estimates of the moment arms of intra-
    abdominal pressure acting about the L5/S1 joint. We are aware of a
    reference in an article by Chaffin:

    Chaffin (1975) "On the validity of biomechanical models
    of the low back for weightlifting analysis," ASME
    Proceedings, 75-WA-bio-1.

    This is also cited in Chaffin and Andersson's book:

    Chaffin and Andersson, Occupational Biomechanics,
    Wiley, New York, 1991.

    Are there any other approaches we can take in modeling intra-abdominal
    pressure? We are particularly interested in subject-specific models
    based on scaling schemes based on bony landmark measurements. We are
    hoping to obtain a simple relation between TORSO ANGLE and the L5/S1
    intra-abdominal pressure MOMENT ARM.

    (2) We also are trying to find a subject-specific scaling scheme (based
    on bony landmarks, hopefully) for the distance from the skin surface to
    L5/S1 joint center of rotation. Is there a database or study out there
    that relates to this estimate in some way? We are aware of the work of
    McNeill et al:

    McNeill, T, Warwick, D, Andersson, GBJ, Schultz (1980)
    "Trunk Strengths in attempted flexion, extension and
    lateral bending in healthy subjects with low back
    disorders," Spine 5: 529-538

    This study places the L5/S1 joint center 34% from posterior on the
    anteroposterior diameter. Is there any other related information out

    As always, we will post a summary of responses. Thanks in advance,

    Hsin-I Chang, B.S.
    Wynne Lee, Ph.D.
    Jim Patton, M.S.
    Aileen Russo, M.S.
    Julie Steege, B.S.
    Motor control and learning group
    Programs in Physical Therapy and Biomedical Engineering
    Northwestern University
    Chicago, Illinois, USA