A three-dimensional model of the shoulder and elbow

A three-dimensional musculoskeletal model of the shoulder and elbow has been developed, in order to increase the functional insight in the mechanical behavior of the shoulder and neural control issues, to assist in diagnosis and treatment of shoulder disorders, and to estimate the load on morphological structures for prevention of injuries. In the model all bones and joints of the upper extremity, i.e. the shoulder girdle joints, glenohumeral, elbow and forearm joints, are represented, as well as the 31 muscles crossing the joints. Muscle dynamics are represented by a third-order muscle model. Morphological data have been obtained in cadaver studies. The model has an inverse dynamic mode, in which muscle forces are calculated from the recorded motion and external forces, as well as a forward dynamic mode, in which the resulting motion from the neural input to the muscles is calculated. A few examples for a standardized motion (abduction), clinical application (glenohumeral endoprosthesis) and ergonomic application (reaction forces in the glenohumeral joint) are demonstrated.