A model for the prediction of the forces at the glenohumeral joint.

The design, validation, and application of a three-dimensional musculoskeletal model of the upper limb is presented here, for the study of joint, muscle, and ligament forces during selected tasks of daily living. Much of the model was constructed using data gathered from real cadavers, including the extensive 'visible human' data set, together with information gathered from published post mortem studies on cadavers. Validation was carried out through comparison of model outcomes with available data in the literature. The model was then used to examine the glenohumeral joint loading during ten previously selected activities of daily living. The predicted glenohumeral joint contact forces during everyday activities were found to range from 23 to 75 per cent body weight. A linear regression method for estimating the joint load from externally measured kinetics was developed, giving a 95 per cent confidence interval in predicted joint forces of 8 per cent body weight. The model presented here, namely the Newcastle shoulder model, provides a basis for future studies into biomechanical problems relating to the understanding of musculoskeletal pathology and implant design and performance.