THE THREE-DIMENSIONAL GEOMETRY OF THE PROXIMAL HUMERUSIMPLICATIONS FOR SURGICAL TECHNIQUE AND PROSTHETIC DESIGNP. Boileau, MDDepartment of Orthopaedic Surgery, Medical University of Nice-Hôpital de L’Archet, 151 Route de St-Antoine de Ginestière, 06200 Nice, France. G. Walch, MD Clinique Emilie de Vialar, 116 Rue Antoine Charrial, Lyon 69003, France. Correspondence should be sent to Dr P. Boileau. We have studied the three-dimensional geometry of the proximal humerus on human cadaver specimens using a digitised measuring device linked to a computer. Our findings demonstrated the variable shape of the proximal humerus as well as its variable dimensions. The articular surface, which is part of a sphere varies individually in its orientation as regards inclination and retroversion, and it has variable medial and posterior offsets. These variations cannot be accommodated by the designs of most contemporary humeral components. Although good clinical results can be achieved with current modular and non-modular components their relatively fixed geometry prevents truly anatomical restoration in many cases. To try to restore the original three-dimensional geometry of the proximal humerus, we have developed a new type of humeral component which is modular and adaptable to the individual anatomy. Such adaptability allows correct positioning of the prosthetic head in relation to an individual anatomical neck, after removal of the marginal osteophytes. The design of this third-generation prosthesis respects the four geometrical variations which have been demonstrated in the present study. These are inclination, retroversion, medial offset and posterior offset. This article has been cited by other articles:
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