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  • SUMMARY - knee model advice

    Please find below my original posting and responses. Thanks to those
    who replied.

    --

    Carol F. Kallfelz, MS, Engr
    Supervisor, Motion Analysis Laboratory
    RR&D Center for Limb Loss Prevention and Prosthetics Engineering
    VA Puget Sound Health Care System
    1660 S. Columbian Way MS 151
    Seattle, WA 98121
    Phone: (206) 762-1010, ext. 63223
    Fax: (206) 764-2127
    Email: kallfelz@u.washington.edu



    ORIGINAL POSTING
    __________________________________________________ ____________________

    Dear Subscribers,

    Please bear with yet another request for advice on knee models: I would

    appreciate hearing from those of you who have implemented one of the
    many published models of the knee to solve the indeterminate problem.

    My goal is a familiar one: to predict the muscle, ligament, and
    articular contact forces throughout the gait cycle using kinematic,
    ground reaction force, and anthropometric data. I’d prefer to use an
    existing dynamic, rigid body model. Accuracy, particularly of the
    contact forces, is my primary concern; ease of implementation is
    secondary. I’ve identified the following models/approaches as possible
    candidates:

    Schipplein and Andriacchi (1991) Interaction between active and passive
    knee stabilizers during level walking. J Orthop Res 9:113-119

    Tumer and Engin (1993) Three-body segment dynamic model of the human
    knee. Transactions of the ASME 115:350-6 (modified for the inverse
    dynamic problem)

    Collins JJ (1995) The redundant nature of locomotor optimization laws. J

    Biomech 28(3):251-267. (later modified and validated by Lu et al
    (1997))

    Glitsch and Baumann (1997) The three-dimensional determination of
    internal loads in the lower extremity. J Biomech 11/12:1123-1131


    Before committing to one, I would appreciate advice from anyone who has
    had practical experience (good or bad) with any of the above. Are there

    well-established benefits/limitations of each? How sensitive is the
    model to anatomical detail (i.e., can generic anatomy be used with
    reasonable confidence if CT/MRI of individual subjects is not possible)?

    And is there a more appropriate model that I have overlooked? General
    comments (of the ‘if I knew then what I know now’ kind) concerning 2D
    vs. 3D, phenomenological vs. anatomical models, the importance of
    including the patellofemoral joint, optimization criteria, role of EMG,
    etc. would also be most welcome.

    Thanks in advance for your help.





    RESPONSES
    __________________________________________________ ____________________

    There are many other models for estimating knee forces than you have
    listed. For example,

    Kaufman et al. (1991) Physiological prediction of muscle forces - I.
    Theoretical Formulation. Neuroscience 40: 781-792.

    Kaufman et al. (1991) Physiological prediction of muscle forces - II.
    Application to isokinetic exercise. Neuroscience 40: 793-804

    Mikosz et al. (1988) Model analysis of factors influencing the
    prediction
    of muscle forces at the knee. JOR 6: 205-214.

    Also see older papers by Crowinshield and Brand (1981), D.E. Hardt
    (1978),
    Seireg and Arvikar (1973, 1975), and A.G. Patriarco et al. (1981).

    For sensitivity analysis to input parameters, see R. A. Brand et al.
    (1986)
    The sensitivity of muscle force predictions to changes in physiologic
    cross-sectional area. J Biomech 19: 589-596.

    You have chosen an area with an extensive literature. It is worthwhile
    doing an exhaustive literature search before deciding on a model. I
    would
    note that one of the main differences in modeling approach is whether
    optization or EMG (or both) are used to estimate muscle forces. Many
    researchers have strong feelings about which approach is superior.

    Regards,

    Richard Hughes, Ph.D.
    Departments of Surgery and Biomedical Engineering
    University of Michigan



    __________________________________________________ ____________________


    Carol,

    Here's another model paper that might help. If you have any questions
    on
    this one, I would be happy to answer them:
    Zheng N, Fleisig GS, Escamilla RF, Barrentine
    SW.
    An analytical model of the knee for estimation of internal forces during

    exercises. Journal of Biomechanics 31(10):963-967, 1998.

    - Glenn

    A SSSS M M IIIIIIII
    A A S S MM MM I
    A A SS M M M I
    AAAAA SS M M I
    A A S S M M I
    A A SSSS M M IIIIIIII
    ************************************************** *******
    Glenn S. Fleisig, Ph.D.
    work phone: 205-918-2139
    work fax: 205-918-0800
    address: American Sports Medicine Institute
    1313 13th Street South
    Birmingham, Alabama 35205
    email: glennf@asmi.org
    web site: http://www.asmi.org
    ************************************************** ********



    __________________________________________________ ____________________

    Dear Carol:

    Part of my research in knee mechanics involved biomechanical models for
    measuring joint reaction forces due to both external and internal (ie,
    muscle, ligament,
    tibiofemoral contact) loads. The following models are a just a few that
    are in existent today and are only appropriate if your objectives are
    similar to those of the
    investigators who incorporated these models:

    (1) Morrison, JB. (1968) Bioengineering analysis of force actions
    transmitted by the knee joint. Biomedical Engineering 3: 164-170
    COMMENTS: Good kinetic model but doesn't account for osteokinematic
    details (ie, changes in tibiofemoral contact points)

    (2) Schipplein, OD, and Andriacchi, TP. (1991) Interaction between
    active and passive
    knee stabilizers during level walking. J Ortho Res 9:113-119
    COMMENTS: Similar model to Morrison (1968) with two unique traits: (a)
    soft tissue tensions were considered in equilibrium equations; and (b)
    varus/valgus
    loads were balanced by collateral ligament tensions; Good model for
    calculating total rxn force, especially in determining the forces
    involved in condylar lift-off (ie,
    increased medial compartment loading). I think there were not enough
    details described regarding the derivation of equilibrium equations.

    (3) Lutz, G.E., Palmitier, R.A., An, K.N., Chao, Y.S. (1993) Comparison
    of tibiofemoral joint forces during open-kinetic-chain and
    closed-kinetic-chain
    exercises. J Bone and Joint Surgery 75-A(5), 732-739.
    COMMENTS: Detailed kinetic model of the knee during weight-bearing and
    non-weight-bearing. Only considers hamstring and quadricep muscle forces
    (EMG
    activity) but offers good estimations of shear as well as compressive
    tiobiofemoral forces.

    Although these as well as other biomechanical models offer effective
    load estimations, the best method(s) that accurately measure joint
    loading are those that are
    not perfected yet. There are currently some research being conducted on
    methods of direct load measurements that would eventually and hopefully
    replace such
    biomechanical models. These include robust sensors that measure
    intramuscular pressure (replacing EMG) as well as articular loading.
    Such sensors could have
    serious clinical implications in the future.

    Well, I hope this helps a little. Good luck!

    Arnel

    =======================================
    Arnel Aguinaldo, M.A.
    Biomechanical Engineer
    San Diego State University
    Athletic Medicine - University of California, San Diego
    San Diego, CA
    email: ala@znet.com
    url: http://ala.someone.net/cv99.htm


    __________________________________________________ ____________________

    Carol,

    Predicting all three (muscle, ligament and contact forces) accurately is
    not
    going to be easy. I am assuming you will be measuring lower limb
    kinematics, EMG and ground reaction forces and using inverse dynamics to

    obtain the mentioned forces. There are just too many variables to get
    an
    accurate prediction. Either you have to make several broad assumptions
    or
    use some sort of optimization to get the results. Also, are you going
    to
    separate the individual ligaments (e.g. anterior and posterior cruciate)
    or
    are you going to lump all the capsuloligamentous structures into one
    passive
    soft tissue structure group? The latter makes the problem more
    tractable.
    The next thing to consider is whether you will be creating a subject
    specific model or a generic model with anthropometric scaling of certain

    parameters. Finally the location of the tibiofemoral contact point is
    important to accurately model knee forces. Most models either calculate

    moments about an arbitratily fixed center of flexion extension, or
    cruciate
    crossing point, but don't take into account the back and forth sliding
    of
    the knee (and the contact point). This is because traditional gait
    analysis
    methods are not sensitive enough to pick up tibiofemoral translations.
    Fluoroscopic gait analysis can measure tibiofemoral translations but it
    has
    its own disadvantages. We have have been working on knee kinematics in
    cadaveric models. While our model uses only the quadriceps muscle for
    closed chain knee extension, it serves as a good starting place to
    determine
    the interactions of contact point location, ligament forces, etc. More
    relevant to your question, we have also developed a total knee
    replacement
    tibial prosthesis instrumented with force transducers and telemetry so
    it is
    possible to measure the actual tibiofemoral compressive force magnitude
    and
    location in vivo. We believe that actually measuring the contact force
    and
    location will reduce the unknowns to make modeling and prediction of
    muscle
    and ligament forces more accurate. We have already validated cadaver
    models
    with this prosthesis and hope to implant it in vivo in the near future.
    While the prosthesis would only provide information about contact forces
    in
    a patient with a total knee replacement, it can be used to validate any
    or
    all of the models available today and thus be useful in predicting
    forces in
    normal gait.

    Please let me know if you want any more information.

    Darryl D'Lima, MD
    Head, Joint Mechanics Laboratory
    Scripps Clinic, CA

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