[Biomechanics of the shoulder]

The shoulder joint takes a special position among all the other joints of the human body because of its special requirements of stability and mobility. Knowledge of the biomechanics of the shoulder joint forms the basis for the development of modern concepts of reconstructive surgery and arthroplasty. Most of the biomechanical findings are the result of research performed on cadaver shoulders using increasingly sophisticated methods of measurement. These studies elucidate the interaction of the static and dynamic factors which contribute to the delicate balance of the glenohumeral joint. Recently performed research is increasingly being focussed on more detailed analyses of muscle forces and stress distribution in the subchondral bone and periarticular soft tissues. The efficiency of the computer systems now available has enabled the development of complex, virtual shoulder models and three-dimensional finite element analyses. In the future a pure mechanical understanding has to be modified to extend to a concept which includes more data obtained from living subjects, especially with regard to muscle activity under varying loads and neuromuscular feedback systems which currently are difficult to assess.