Patent ID: 8021431

Claim:
A modular basal thumb joint implant comprising the following parts: a head including a single, smooth, generally hemispherical, medio-proximally directed, articulating surface, and a generally abrupt, distally directed, planar end to the head which defines an end to said articulating surface and has a center, said articulating surface being continuous as to its sphericity and uninterrupted up to the end of said articulating surface so that said articulating surface defines a truncated ball of a shape that is from substantially hemispherical to greater than substantially hemispherical; and a stem, which is attachable to the head, and which, when attached to the head, projects from the head along an axis, which arises from the generally planar end to the head and includes at least one of the following features: A) a general angle of projection from the head that is acute in relation to the generally planar end to the head; B) a flanged cross-sectional stem profile, which, when taken in cross-section perpendicularly to the stem, is in a tri-flange shape, with three flanges without notches extending distally on the stem; C) an inwardly curved stem; D) an eccentric head site for the stem, which is offset from the center of the generally planar end of the head; wherein said implant has its head of a size for mounting in and articulating with a correspondingly concavely prepared surface of trapezium bone stock, and its stem of a size for intramedullary insertion in metacarpal bone stock.