Patent ID: 7914584

Claim:
A prosthesis system extending along a longitudinal axis and having a head assembly, comprising: a prosthesis stem; a trunnion having a first end and a second end and a midsection, the second end adapted to be fixed to the prosthesis stem, the midsection interposed between the head assembly and the prosthesis stem, the trunnion having an annular shoulder which defines a first bearing surface in a plane substantially perpendicular to the longitudinal axis of the first end of the trunnion, the annular shoulder also defining an outer surface that intersects the first bearing surface and extends outward from the longitudinal axis, the midsection being interposed between the annular shoulder and the second end, the midsection having a cross sectional area that is constant along an entire length of the midsection between the annular shoulder and the second end; a head having a second bearing surface on which a second prosthesis can articulate, and a third bearing surface, the head defining a recess adapted to securedly receive the first end of the trunnion such that the first bearing surface of the annular shoulder directly abuts the third bearing surface of head, the second bearing surface and the outer surface of the annular shoulder being continuous with respect to each other to cooperatively define the head assembly such that, in a cross section of the trunnion and the head taken along the longitudinal axis, the head defines an entirely curved line with two head end points and the shoulder defines two straight lines with respective shoulder end points, the two head end points being directly adjacent respective ones of the shoulder end points; and wherein the second end of the trunnion is releasably connectable to the prosthesis stem by a taper fit connection.