A comprehensive three dimensional dynamic model of the human elbow joint

This study introduces a three-dimensional dynamic model of the human elbow joint. In this model the bones and joints of the upper extremity as well as 15 muscles and 4 ligaments crossing the elbow joint were considered. Six equations of motion, with 30 unknowns, were obtained using Newton's 2nd law of motion at elbow joint. These unknowns were the magnitudes and directions of 15 elbow muscle forces, 4 ligament forces, the moment arms of the muscles and ligaments about the elbow and radio-humeral joints, and the contact forces. The position of the bony landmarks and the centers of gravity of the upper limb were recorded in global coordinates with two digital video cameras. The WINanalyze software was used to analyze the motion. The results were fed to the software package, developed by the authors, to calculate the kinematics of points of interest as well as the direction cosines and moment arms of all the muscle and ligaments. A genetic optimization package was used to compute the musculoskeletal forces, utilizing the minimization of the resultant contact force at the elbow region as an objective function.