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A simple elbow kinematic model: problems about assumptions

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  • A simple elbow kinematic model: problems about assumptions

    Dear Biomch-L users,


    I would really appreciate your comments and suggestions about the following
    assumptions concerning elbow axes of rotation and their relation with
    humerus and forearm long axes; my aim is to build a simple kinematic model
    of the elbow in ADAMS(c) using rigid links and hinge joints.

    Considering an arm in the frontal plane (forearm extended and supinated):

    1)Humerus long axis (Yh): the line pointing upward from the midpoint between
    medial and lateral epicondyle ( E = (EM+ EL)/2 ) to the glenohumeral
    rotation centre (GH) [1];

    2)Forearm long axis (Yf): the line pointing upward from the midpoint
    between ulnar and radial styloid (US, RS) to E [1];


    3)Carrying angle: angle formed by the forearm long axis and the humerus long
    axis when the forearm is fully extended and supinated [3]; NB: in [3] I
    didn't find the definition of the long axes with respect to the previously
    defined anatomical landmarks, even if I supposed that the above given are
    nevertheless applicable.

    4)Prosupination axis: the line pointing upward from US to E [1];

    5)Flexion-extension axis: assumed orthogonal to the prosupination axis [2]
    passing through E; its direction should correspond to the Z axis of the
    humerus bone embedded
    system (see below different definitions suggested in [1]);




    >From [1]:
    1) Humerus (1st degree) Coordinate System - Xh1Yh1Zh1
    Oh1: The origin coincident with GH.
    Yh1: The line connecting GH and the midpoint of EL and EM, pointing to GH.
    Xh1: The line perpendicular to the plane formed by EL, EM, and Yh1, pointing
    forward.
    Zh1: The common line perpendicular to Yh1- and Zh1-axis.
    2) Humerus (2nd degree) Coordinate System - Xh2Yh2Zh2
    Oh2: The origin coincident with GH.
    Yh2: The line connecting GH and the midpoint of EL and EM, pointing to GH.
    Zh2: The line perpendicular to the plane formed by Yh2 and Yf (see above),
    pointing laterally. Zh2-axis is taken with 90 degrees flexed elbow.
    Xh2: The common line perpendicular to Xh2- and Yh2-axis.


    [1] Frans C.T. van der Helm , (2002) "ISB Recommendation on Definitions of
    Joint Coordinate System of Various Joints for the Reporting of Human Joint
    Motion - Part II: Shoulder, Elbow, Hand and Wrist, Shoulder", Submitted to
    JBiomech 2002

    [2] Veeger H.E.J, (1997) "Orientation of axes in the elbow and forearm for
    biomechanical modeling" Proc. of the 1^ Conf. of the ISG

    [3] Zatsiorsky V.M., (1998) "Kinematics of the Human Motion", Human
    Kinematics


    Many thanks
    Best regards
    Andrea G. Cutti


    -----
    Ing. Andrea Giovanni Cutti
    PhD Student - Biomedical Engineering Group
    University of Bologna
    Viale Risorgimento 2
    40136 - Bologna

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