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View Full Version : A simple elbow kinematic model: problems about assumptions



unknown user
03-02-2004, 10:22 AM
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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