Abstract: A modular humeral prosthesis that can be custom fitted to a particular patient by interchanging sizes of the various components by a surgeon interoperatively. The prosthesis features a humeral head having a hemispherically shaped outer surface for placement within the glenoid cavity of a human scapula, the head including on its undersurface a recessed center portion having a first cooperating connecting means. The body has a proximal end and a distal end, with the proximal end including an angled platform having a second cooperating connecting means for engagement with said first connecting means, and the distal end having a third cooperating connecting means. The body also includes a plurality of fins. A cylindrical primary stem has a proximal end and a distal end, the proximal end having a forth cooperating connecting means for engagement with said third connecting means, and the distal end having a fifth cooperating connecting means.

Abstract: An apparatus for guiding the resection of the head of a humerus is provided. The apparatus includes an intramedullary alignment member having a longitudinal axis and structured for substantial axial alignment with the intramedullary canal of the bone, one point of reference for the resection. The apparatus also includes an extramedullary alignment member and a collar rotatably mounted on the intramedullary member for rotating the extramedullary alignment member about the longitudinal axis of the intramedullary alignment member to a desired degree of retrotorsion. A cutting block and a first shaft and a second shaft in a perpendicular orientation relative to the first shaft for positioning the cutting block in a desired orientation relative to the head of the bone are also provided.