Anatomical Study of the Proximal Humerus: Surgical Technique Considerations and Prosthetic Design Rationale

Summary

In an effort to better understand the three-dimensional geometry of the proximal humerus, an anthropometric study was undertaken analyzing human cadaveric specimens using a digitized measuring device linked to a computer. The present study emphasizes the variable shape of the proximal humerus over its variable dimensions because of the variable orientation (variable inclination and retro-version) and the variable location of the articular surface (variable medial and posterior offset). The shape of the proximal humerus is variable, much more variable in fact than the designs of most contemporary humeral components would suggest or can accommodate. Although good clinical results with shoulder replacement can be achieved using either the modular or the nonmodular components that are currently available,their relatively fixed geometry means that they are not truly anatomical when compared with our findings. We have developed a new type of humeral component based on these findings which is not only modular but also adaptable to the individual bony anatomy. Prosthetic adaptability is a new concept in the design of shoulder prosthesis which concentrates on correctly positioning the prosthetic head in relation to the individual anatomical neck.