Semi-constrained 1

1. A first carpometacarpal ball and socket joint implant for implantation in a patient's wrist following removal of a trapezium from the wrist, including:

a proximal component having a joint portion, a trapezoid-engaging fixation portion, and a skid, wherein the joint portion includes one of a ball-shaped member having a convex surface and a socket-shaped member having a concave surface, the one of the convex surface of the ball-shaped member and the concave surface of the socket-shaped member of the joint portion extending from the fixation portion at an angle offset from a longitudinal axis of the fixation portion and the fixation portion adapted to penetrate and be fixedly mounted to one or more elements of a patient's distal carpal row including at least a trapezoid to locate and support the joint portion in a fixed cantilevered position with respect to the one or more elements of the patient's distal carpal row in a space previously occupied by the trapezium with the one of the convex surface of the ball-shaped member and the concave surface of the socket-shaped member configured to be aligned with a longitudinal axis of a patient's thumb metacarpal, wherein the skid on the joint portion of the proximal component is configured for movably engaging a patient's scaphoid bone; and a distal

component having a joint portion movably mounted to the joint portion of the proximal component, and a metacarpal-engaging fixation portion for attachment to the patient's thumb metacarpal, wherein the joint portion of the distal component includes the other of the ball-shaped member and the socket-shaped member.

2. The implant of claim 1 wherein the joint portion with the socket-shaped member includes a polymer cup slidably mounted to the joint portion.

3. The implant of claim 1 wherein:

the joint portion of the proximal component includes the ball-shaped member; and

the joint portion of the distal component includes the socket-shaped member.

4. The implant of claim 3 wherein the joint portion with the socket-shaped member includes a polymer cup slidably mounted to the joint portion.

5. The implant of claim 1 wherein the skid includes a member extending from the proximal component joint portion on a side opposite a side to which the joint portion of the distal component is mounted.

6. The implant of claim 1 wherein the skid includes a recess in the proximal component joint portion on a side opposite a side to which the joint portion of the distal component is mounted.

7. The implant of claim 1 wherein the fixation portion of either or both of the proximal and distal components includes a threaded member.

8. A method for performing 1 st carpometacarpal implant arthroplasty on a patient, including:

removing a trapezium;

penetrating and fixedly mounting a proximal implant component having a joint portion to one or more elements of a distal carpal row including at least a trapezoid, with the joint portion in a fixed cantilevered position with respect to the one or more elements of the distal carpal row by a fixation member off the distal row in a space previously occupied by the trapezium, wherein the proximal component joint portion includes one of a ball-shaped member having a convex surface and a socket-shaped member having a concave surface, and a skid on the joint portion, the one of the convex surface of the ball-shaped member and the concave surface of the socket-shaped member extending from the fixation member at an angle offset from a longitudinal axis of the fixation member and the skid movably engages a patient's scaphoid bone, and wherein the one of the convex surface of the ball-shaped member and the concave surface of the socket-shaped member is aligned with a longitudinal axis of a patient's thumb metacarpal; and

attaching a distal implant component having a joint portion that movably cooperates with the joint portion of the proximal implant component to the patient's metacarpal, wherein the distal component joint portion includes the other of the ball-shaped member and the socket-shaped member.