Prosthesis
A distal component for an interphalangeal prosthesis suitable for insertion into a proximal end of a distal phalangeal bone includes a stem portion shaped to be received within a surgically prepared bore in the proximal end of the distal bone. A head portion has an under-surface and an upper-surface, the under-surface of which in use will bear on the bone into which the stem is implanted.
1. A distal component for an interphalangeal prosthesis suitable for insertion into a proximal end of a distal phalangeal bone, said component comprising:
a stem portion shaped to be received within a surgically prepared bore in the proximal end of the distal phalangeal bone, said stem portion generally tapering inwardly from a proximal to a distal end and having a central longitudinal axis extending from the distal end to the proximal end, said stem portion additionally comprising a head supporting surface formed as a single piece with said stem portion, the underside of said head supporting surface bearing on the distal phalangeal bone into which the stem is implanted and extending from the stem portion and being ramped away therefrom at an angle of greater than 90° to the longitudinal axis of the shaft; and
a head portion having an under-surface and an upper-surface, the under-surface of which in use will face the distal phalangeal bone into which the stem is implanted, said head portion extending from the stem portion and being ramped away therefrom at an angle of greater than 90° to the longitudinal axis of the shaft; said upper-surface comprising an articulating surface shaped to enable a cooperating surface on a distal end of a proximal phalangeal bone to articulate there-against as a hinge joint, the head portion having a bore therein;
wherein the stem portion in use supports a separate upper section of the head portion, wherein the stem portion includes a stalk extending from and surrounded by the head supporting surface and including a barb to assist in interlocking in the bore, the bore and barb of the stalk being constructed for snap-fit, locking interengagement upon reception of the stalk and barb in the bore to connect the head portion and the stem portion.
2. A distal component for an interphalangeal prosthesis according to claim 1 wherein the barb extends around the outer circumference of the stalk.
3. A distal component for an interphalangeal prosthesis according to claim 1 wherein an upper section of the head portion is formed from a biocompatible plastics material.
4. A distal component for an interphalangeal prosthesis according to claim 3 wherein said biocompatible plastics materials is ultra high molecular weight polyethylene.
5. A distal component for an interphalangeal prosthesis according to claim 1 wherein the stem portion is formed from a biocompatible metal or plastics material.
6. A distal component for an interphalangeal prosthesis according to claim 5 wherein said biocompatible metal material is cobalt-chrome, titanium, titanium alloys, titanium coated cobalt-chrome, or stainless steel.
7. A distal component for an interphalangeal prosthesis according to claim 1 where the articulating surface is shaped to accept bicondular features of the distal end of the proximal phalangeal bone to form the hinge joint.