Radial head prosthesis with floating articular member
System, including apparatus, methods, and kits, for replacement of the proximal end of a radial bone with a prosthesis having a floating articular member. The prosthesis may include a head portion connected or connectable to a stem portion. While the stem portion remains operatively connected to the head portion, the head portion and/or an articular member thereof may be permitted to float in position relative to the stem portion. The head portion/articular member may float transversely (e.g., translationally) and/or rotationally with respect to the stem portion. The articular member may articulate with a humeral bone or both a humeral bone and an ulnar bone. In some embodiments, the head portion may include a fixed member for articulation with an ulnar bone and a floating member for articulation with a humeral bone.
1. A method of replacing an end of a radial bone with a radial head prosthesis having a stem portion and a head portion, the head portion connected or connectable to the stem portion, the head portion comprising a fixed member and a floating articular member, the method comprising:
operatively installing the prosthesis such that the stem portion of the prosthesis is attached to a radial bone, the fixed member directly articulates with an ulnar bone, and the floating articular member directly articulates with a humeral bone and is operatively movable translationally with respect to the fixed member in a direction transverse to a long axis defined by the radial bone when the radial head prosthesis is finally implanted and fully operational,
wherein the fixed member includes a cup portion, and wherein the floating articular member is disposed in the cup portion after the step of installing.
2. The method of claim 1 , wherein at least one of the ulnar bone and the humeral bone includes a prosthetic region, and wherein at least one of the fixed member and the floating member articulates at least in part with a prosthetic region.
3. The method of claim 1 , wherein a majority by volume of the floating member is disposed in the cup portion after the step of installing.
4. The method of claim 1 , wherein the floating member is rotatable with respect to the fixed member during movement of the radial bone with respect to the ulnar bone and/or humeral bone after the step of operatively installing.
5. The method of claim 1 , wherein wherein the head portion includes at least one resilient member that is deformable to bias a position of the floating member with respect to the fixed member.
6. A method of replacing a proximal end of a radial bone with a radial head prosthesis having a stem portion and a head portion, the head portion connected or connectable to the stem portion, the method comprising:
installing the prosthesis in an operative configuration, with the stem portion mounted to a radial bone, a first member of the head portion directly articulating with an ulnar bone and fixed with respect to the stem portion, and a second member of the head portion directly articulating with a humeral bone and operatively movable translationally with respect to the first member in a direction transverse to a long axis defined by the stem portion when the radial head prosthesis is finally implanted and fully operational,
wherein the second member is a floating articular member,
wherein the first member includes a cup portion, and wherein the floating articular member is disposed in the cup portion after the step of installing.
7. The method of claim 6 , wherein the second member is rotatable with respect to the first member in the operative configuration.
8. The method of claim 6 , wherein at least one of the ulnar bone and the humeral bone includes a prosthetic region, and wherein at least one of the first member and the second member articulates at least in part with said prosthetic region.
9. The method of claim 6 , wherein the second member is connected to the first member by a movable joint that permits translational motion and rotational motion of the first and second members relative to each other.
10. The method of claim 6 , wherein the second member is connected to the stem portion by a slidable joint and a pivotable joint that are distinct from each other.
11. The method of claim 6 , wherein the step of installing permits the floating articular member to rotate as a unit with respect to the stem portion to change a tilt of the floating articular member with respect to the stem portion.
12. The method of claim 6 , wherein the floating articular member is operatively connected to the stem portion by a movable joint including a spherical surface region corresponding to no more than one-half of a complete sphere.