Reverse shoulder prosthesis

1. A reverse shoulder prosthesis comprising:

a humeral stem implantable in a shoulder humerus;

a humeral socket attached to the humeral stem, the socket having a concave articulating surface defining a first shape; and

a glenoid component including an attachment surface for attachment to the shoulder glenoid and a convex ovoid surface non-conformingly articulatable with the articulating surface of the socket, the convex ovoid surface having a narrow end and a broad end and defining a second shape, the first and second shapes not conforming relative to one another.

2. The reverse shoulder prosthesis of claim 1 , wherein the narrow end is superior and the broad end is inferior.

3. The reverse shoulder prosthesis of claim 2 , wherein the attachment surface is inclined at an angle relatively to a longitudinal axis of the humerus.

4. The reverse shoulder prosthesis of claim 3 , wherein the angle is in the range of about 0° to 45°.

5. The reverse shoulder prosthesis of claim 3 , wherein the angle is selected for reducing loosening of the glenoid component.

6. The reverse shoulder prosthesis of claim 3 , wherein a shape of the ovoid surface is selected for reducing notching of the humeral stem on the scapula.

7. The reverse shoulder prosthesis of claim 2 , wherein the ovoid surface has a variable curvature.

8. The reverse shoulder prosthesis of claim 1 , further including at least one threaded fastener and at least one unthreaded fastener for attaching the glenoid component to the scapula.

9. The reverse shoulder prosthesis of claim 1 , wherein the humeral socket is modular and includes a modular backing plate and a modular insert.

10. A reverse shoulder prosthesis comprising:

a humeral socket attachable to a shoulder humerus, the humeral socket having a concave surface defining a first shape; and

a glenoid component attachable to the shoulder glenoid, the glenoid component having a major diameter and a convex surface for articulating with the concave surface of the socket, the convex surface having a height from the major diameter that is less than a corresponding height of a spherical surface having the same a diameter equal to the major diameter, the convex surface having a broad end and a narrow end and defining a second shape, the first and second shapes only partially conforming.

11. The reverse shoulder prosthesis of claim 10 , further comprising a humeral stem attached to the humeral socket.

12. The reverse shoulder prosthesis of claim 11 , wherein the glenoid component has a planar attachment surface oriented at an angle relative to a longitudinal axis of the humeral stem.

13. The reverse shoulder prosthesis of claim 12 , wherein the angle is selected for reducing loosening of the glenoid component.

14. The reverse shoulder prosthesis of claim 11 , wherein the humeral socket is integral with the humeral stem.

15. The reverse shoulder prosthesis of claim 10 , wherein the humeral socket is modular.

16. The reverse shoulder prosthesis of claim 15 , wherein the humeral socket comprises a backing plate and an insert.

17. The reverse shoulder prosthesis of claim 10 , wherein the convex surface is an ovoid surface.

18. The reverse shoulder prosthesis of claim 10 , wherein the humeral socket is an integral component.

19. The reverse shoulder prosthesis of claim 10 , wherein the concave surface of the humeral socket has a radius of curvature selected from the group consisting of constant curvature, variable curvature, and combinations thereof.

20. The reverse shoulder prosthesis of claim 10 , wherein the glenoid component further comprises scapula attachments selected from the group consisting of screws, anchors, pegs, keels, and combinations thereof.

21. The reverse shoulder prosthesis of claim 20 , wherein the scapula attachments are directly coupled to the glenoid component.

22. The reverse shoulder prosthesis of claim 20 , wherein the scapula attachments are indirectly coupled to the glenoid component.

23. The reverse shoulder prosthesis of claim 10 , wherein the first shape includes a single isolated conforming portion that conforms to and contacts a corresponding portion of the second shape during a relative articulation motion between the convex and concave surfaces, the single isolated portion surrounded by non-conforming portions of the concave surface.

24. The reverse shoulder prosthesis of claim 23 , wherein an articulation constraint between the convex and concave surfaces is minimal before contact starts over the single isolated conforming portion, and wherein the articulation constraint increases when contact of the first and second shapes begins over the single isolated conforming portion.

25. The reverse shoulder prosthesis of claim 23 , wherein the single isolated conforming portion provides variable amount of constraint during articulation of the convex and concave surfaces.

26. The reverse shoulder prosthesis of claim 23 , wherein the single isolated conforming portion is offset relative to a minor diameter of the second shape.

27. The reverse shoulder prosthesis of claim 10 , wherein first shape includes at least two isolated and spaced apart conforming portions that conform to and contact corresponding portions of the second shape during a relative articulation motion between the convex and concave surfaces.

28. The reverse shoulder prosthesis of claim 27 , wherein an articulation constraint between the convex and concave surfaces increases when contact of at least one of the first and second shapes begins over the corresponding isolated conforming portion.

29. The reverse shoulder prosthesis of claim 27 , wherein the two isolated conforming portions provide variable amount of constraint during articulation of the convex and concave surfaces.

30. The reverse shoulder prosthesis of claim 27 , wherein the two isolated conforming portions are offset relative to a minor diameter of the second shape.