Wrist prosthesis

1. A prosthesis for a wrist joint replacement, comprising:

a radial brace member having a volar side, dorsal side, radial side, ulnar side, proximal side and distal side, and including a wall at said distal side which defines a first ellipsoidal surface and a distal edge, wherein the volar side of said distal edge defines a centrally recessed guide surface that is concave downwardly, toward in the proximal side, and is concave inwardly, toward the dorsal side; and

an articular member defining a second ellipsoidal surface slidably received by said first ellipsoidal surface, one of said first and second ellipsoidal surfaces being convex and the other being concave.

2. A prosthesis for a total wrist and distal radioulnar joint replacement as recited in claim 1 , and further comprising:

an ulnar brace member, including

a rod defining a proximal end and a distal end and a longitudinal axis; and

a ball mounted on said distal end for translation along said longitudinal axis relative to said rod; and

wherein said radial brace member further defines a bearing surface which supports said ball for relative movement between the ball and the radial brace member.

3. A prosthesis for a wrist joint replacement, comprising:

a radial brace member having a volar side, dorsal side, radial side, ulnar side, proximal side and distal side, and including a wall at said distal side which defines a first ellipsoidal surface and a distal edge, wherein the volar side of said distal edge defines a centrally recessed guide surface; and

an articular member defining a second ellipsoidal surface slidably received by said first ellipsoidal surface, one of said first and second ellipsoidal surfaces being convex and the other being concave, wherein said articular member defines a volar recessed guide surface aligned with and extending proximally to said centrally recessed guide surface.

4. A prosthesis as recited in claim 3 , wherein said volar recessed guide surface is recessed inwardly, towards the dorsal side; and further comprising:

an ulnar brace member including

a rod defining a proximal end and a distal end, and

a ball mounted to said distal end;

wherein said radial brace member defines a bearing surface which receives and supports said ball.

5. A prosthesis for a wrist joint replacement as recited in claim 3 , wherein said centrally recessed guide surface of said first ellipsoidal surface is concave inwardly, toward the dorsal side, and the volar recessed guide surface of the articular member is concave inwardly, toward the dorsal side.

6. A prosthesis for a wrist joint replacement, comprising:

a radial brace member having a volar side, dorsal side, radial side, ulnar side, proximal side and distal side, and including a wall at said distal side which defines a first ellipsoidal surface and a distal edge, wherein the volar side of said distal edge defines a centrally recessed guide surface that is concave downwardly, toward the proximal side; and

an articular member defining a second ellipsoidal surface slidably received by said first ellipsoidal surface, one of said first and second ellipsoidal surfaces being convex and the other being concave;

wherein said articular member defines a volar recessed guide surface aligned with and extending proximally to said centrally recessed guide surface.

7. A prosthesis as recited in claim 6 , and further comprising:

an ulnar brace member including

a rod defining a proximal end and a distal end, and

a ball mounted to said distal end; and

wherein said radial brace member defines a bearing surface configured for mounting on the radius, which receives and supports said ball for rotation relative to the radius.

8. A prosthesis for a total wrist and distal radioulnar joint replacement, comprising:

a radial brace member having a volar side, dorsal side, radial side, ulnar side, proximal side and distal side, and including a wall at said distal side which defines a first ellipsoidal surface and a distal edge, wherein the volar side of said distal edge defines a centrally recessed guide surface that is concave downwardly, towards the proximal side;

an articular member defining a second ellipsoidal surface slidably received by said first ellipsoidal surface, one of said first and second ellipsoidal surfaces being convex and the other being concave;

wherein said second ellipsoidal surface defines a recess aligned with and extending proximally to the central recess in said first ellipsoidal surface; and

an ulnar brace member, including

a rod defining a proximal end and a distal end and a longitudinal axis; and

a ball mounted on said distal end for translation along said longitudinal axis relative to said rod; and

wherein the radial brace member defines a bearing surface which supports said ball.

9. A prosthesis for a total wrist and distal radioulnar joint replacement, comprising:

an ulnar brace member, including

a rod defining a proximal end and a distal end and a longitudinal axis; and

a ball mounted on said distal end for translation along said longitudinal axis relative to said rod; and

a radial brace member having a volar side, dorsal side, radial side, ulnar side, proximal side and a distal side, and defining a first ellipsoidal surface at its distal side that is wider in the radial-ulnar direction than in the volar-dorsal direction, wherein said first ellipsoidal surface is concave and has a distal edge defining a central recess in its volar side which forms a guide surface, and wherein said radial brace member includes an elongated portion projecting in a proximal direction and defining a radius abutment surface, said elongated portion defining a plurality of laterally-oriented holes which are threaded;

a cover releasably mounted on said radial brace member, wherein said cover and said radial brace member together form a substantially spherical cavity which receives and rotationally supports said ball on said radial brace member; and

an articular member defining a second ellipsoidal surface that is convex and is slidably received by the first ellipsoidal surface;

wherein said first ellipsoidal surface extends in the ulnar direction beyond the longitudinal axis of said rod; and

wherein said second ellipsoidal surface defines a recess aligned with and extending proximally to the central recess in said first ellipsoidal surface.

10. A prosthesis as recited in claim 9 , and wherein said radial brace member further defines a proximal convex surface which lies opposite said first ellipsoidal surface and includes means for being received in a natural recess at the distal end of a human radius bone without changing the overall length of the radius bone.

11. A prosthesis as recited in claim 10 , wherein said ulnar brace member is configured for mounting on the ulna bone of a patient,

said articular member includes means for mounting on at least one carpal bone of the patient;

and said ball and said spherical cavity provide the same axis of rotation and the same alignment of the radius and ulna as a natural radioulnar joint.