Reverse shoulder systems and methods

1. A glenoid implant for a shoulder prosthesis comprising:

an anchor member including a longitudinal portion configured to be secured to a bone and a proximal head;

a baseplate including a proximal portion and a distal portion, the baseplate configured to receive the proximal head of the anchor member from the distal portion of the baseplate;

means for constraining relative motion of the anchor member and the baseplate, such that when the proximal head and the baseplate are axially connected with the anchor member in the bone, axial translation therebetween is substantially prevented and the anchor member and baseplate are substantially free to rotate with respect to each other; and

a locking member configured to prevent rotation between the anchor member and the baseplate.

2. The glenoid implant of claim 1 , wherein the means for constraining relative motion includes a first engaging surface and a second engaging surface, the proximal head of the anchor member comprising the first engaging surface, the distal end of the base plate comprising the second engaging surface.

3. The glenoid implant of claim 2 , wherein when the proximal head and the baseplate are axially connected, the first engaging surface is directly coupled to the second engaging surface.

4. The glenoid implant of claim 2 , wherein the first engaging surface comprises a first groove and the second engaging surface comprises a second groove.

5. The glenoid implant of claim 2 , wherein the second engaging surface comprises a smooth region, and wherein when the proximal head and the baseplate are axially connected, the first engaging surface of the proximal head is disposed within the smooth region of the second engaging surface.

6. The glenoid implant of claim 2 , wherein the first engaging surface comprises threads.

7. The glenoid implant of claim 2 , wherein the second engaging surface comprises threads.

8. The glenoid implant of claim 2 , wherein when the proximal head and the baseplate are axially connected, the means for constraining relative motion indirectly connects the anchor member and the baseplate.

9. The glenoid implant of claim 8 , wherein the means for constraining relative motion comprises a member connecting the first engaging surface and the second engaging surface.

10. The glenoid implant of claim 9 , wherein the member is elastically deformable.

11. The glenoid implant of claim 1 , wherein the distal portion of the baseplate comprises a first aperture sized to accept the proximal head of the anchor member.

12. The glenoid implant of claim 1 , further comprising a perimeter anchor configured to secure the baseplate to the bone.

13. The glenoid implant of claim 1 , wherein the distal portion of the baseplate comprises a porous metal.

14. The glenoid implant of claim 13 , wherein the porous metal is formed by additive manufacturing.

15. The glenoid implant of claim 1 , wherein the baseplate comprises a bone engaging surface, the bone engaging surface is asymmetric relative to a longitudinal axis of the baseplate.

16. The glenoid implant of claim 1 , wherein the longitudinal portion of the anchor member is threadless.

17. A glenoid implant for a shoulder prosthesis comprising:

a baseplate comprising a proximal end, a distal end, an outer periphery, an aperture that extends from the proximal end to the distal end, and a peripheral aperture that extends from the proximal end to a bone engaging surface, the baseplate further comprising a wall defining the aperture at the distal end;

a screw configured to be placed through the peripheral aperture, the screw having an external threaded surface; and

an internal member disposed in the peripheral aperture comprising an internal threaded surface, wherein an outer surface of the internal member is movable relative to an inner surface of the peripheral aperture to allow the internal member to aim the screw towards a desired location,

wherein the internal member comprises a protrusion configured to engage a corresponding recess in the peripheral aperture of the baseplate, the protrusion is configured to prevent the internal member from being dislodged from the baseplate.

18. The glenoid implant of claim 17 , wherein the threads of the external threaded surf ace of the screw have a constant thread form along the length thereof.

19. The glenoid implant of claim 17 , wherein a first number of thread starts disposed on the internal threaded surface of the internal member is greater than a second number of thread starts disposed on the external threaded surface of the screw.

20. The glenoid implant of claim 19 , wherein the first number of thread starts on the internal threaded surface of the internal member is two times the number of second thread starts on the external threaded surface of the screw.

21. The glenoid implant of claim 17 , wherein the screw comprises a distal portion extending distally from the distal end of the baseplate and a proximal portion surrounded by the internal member when the screw is fully advanced, the proximal portion having the same thread pitch as the distal portion and having a larger diameter than the distal portion.

22. The glenoid implant of claim 17 , wherein the internal member is semi-spherical.

23. The glenoid implant of claim 17 , wherein the internal member comprises a lumen, a wall surrounding the lumen, and a gap extending through the wall of the internal member.

24. The glenoid implant of claim 17 , wherein a portion of the internal member projects above the proximal end of the baseplate when the internal member is disposed in the peripheral aperture.

25. The glenoid implant of claim 24 , further comprising a glenosphere configured to couple with the baseplate, the glenosphere comprising an interior surf ace defining an interior space that accommodates the portion of the internal member.

26. The glenoid implant of claim 17 , wherein the internal member is configured to be angled relative to a longitudinal axis extending through the aperture of the baseplate.