Systems for reverse shoulder implants
Embodiments of the present invention include a convertible prosthesis that is capable of conversion from a humeral head replacement to a reverse reconstruction without any removal of parts integrated into the patient's bony anatomy (e.g. implant stems). A desired overall implant inclination angle may be achieved by matching various implant stems with various reverse inserts, thus permitting a resection surface to be matched with an implant stem selection while also permitting a desired overall implant inclination angle to be achieved through the selection of an appropriate insert.
1. A system for a modular reverse shoulder prosthesis, the system comprising:
a humeral component having a proximal cavity, the proximal cavity including an inner sidewall;
an insert having a distal end and a proximal end, the distal end configured to engage the proximal cavity of the humeral component, the distal end of the insert including an outer sidewall, the outer sidewall formed about an insert axis, the proximal end including a concave articular surface; and
fins projecting directly inwardly from the inner sidewall of the proximal cavity, the fins projecting to an inner diameter that is smaller than the outer diameter of the outer sidewall, the fins arranged with respect to the proximal cavity of the humeral component such that the fins secure the insert against rotation about the insert axis with respect to the humeral component by deforming the outer sidewall of the insert.
2. The system of claim 1 , wherein the fins are configured to secure the insert against rotation about the insert axis regardless of a rotational position of the insert about the insert axis when the insert is inserted into the humeral component.
3. The system of claim 1 , wherein the outer sidewall is at least partially cylindrical and has the outer diameter formed about the insert axis.
4. The system of claim 3 , wherein the fins are at least three fins arranged on the inner sidewall in a rotationally symmetrical manner about the insert axis.
5. The system of claim 4 , wherein the at least three fins are at least six fins arranged on the inner sidewall in the rotationally symmetrical manner about the insert axis.
6. The system of claim 1 , wherein the fins deform the insert by cutting the insert when the insert is inserted into the humeral component.
7. The system of claim 1 , wherein the fins deform the insert by inelastically deforming the insert when the insert is inserted into the humeral component.
8. The system of claim 1 , wherein a first material out of which the fins are made is harder than a second material out of which the distal end of the insert is made.
9. The system of claim 1 , wherein the distal taper is formed about a taper axis, and wherein the taper axis is offset from the insert axis when the insert is inserted into the humeral component, so as to permit eccentric rotation of the humeral component about the taper axis when the distal taper is inserted into the proximal taper of the stem.
10. The system of claim 1 , wherein the fins project inwardly from a bottom of the proximal cavity.
11. The system of claim 1 , wherein the insert includes a first channel formed circumferentially about the distal end, wherein the insert further includes a snap-fit ring seated at least partially within the first channel, and wherein the humeral component includes a second channel formed circumferentially within the proximal cavity, wherein the snap-fit ring is configured to become seated in both the first and second channels when the insert is inserted into the humeral component so as to secure the insert against separation from the humeral component.
12. The system of claim 11 , wherein the snap-fit ring has an at-rest configuration in which an inner diameter of the snap-fit ring is within the first channel and an outer diameter of the snap-fit ring is outside of the first channel, a compressed configuration in which the outer diameter of the snap-fit ring is seated fully within the first channel, and a partially compressed configuration in which the outer diameter of the snap-fit ring is smaller than the outer diameter of the snap-fit ring in the compressed configuration but not entirely seated within the first channel; wherein the snap-fit ring is configured to be in the at-rest configuration prior to insertion of the insert into the humeral component, wherein the snap-fit ring is configured to be in the compressed configuration as the insert is initially inserted into the humeral component, and wherein the snap-fit ring is configured to assume the partially compressed configuration when the snap-fit ring is seated in both the first and second channels.
13. The system of claim 11 , wherein the snap-fit ring is configured to compress radially so as to be fully received within the first channel when the insert is first inserted into the humeral component.
14. The system of claim 11 , wherein the snap-fit ring includes a discontinuity to facilitate radial compression of the snap-fit ring when the insert is first inserted into the humeral component.
15. The system of claim 14 , wherein the snap-fit ring reversibly secures the insert against separation from the humeral component.
16. The system of claim 15 , wherein the humeral component includes one or more holes formed from an outer surface of the humeral component to within the second channel of the proximal cavity, wherein the one or more holes permit insertion of a tool to compress the snap-fit ring into the first channel so as to permit release of the insert from the humeral component.
17. The system of claim 11 , wherein the snap-fit ring is configured to compress radially, wherein the snap-fit ring includes a distal edge that is chamfered to facilitate compression of the snap-fit ring when the insert is inserted into the humeral component.
18. The system of claim 17 , wherein the humeral component includes a chamfered proximal edge configured to interact with the chamfered distal edge of the snap-fit ring.
19. The system of claim 1 , wherein the humeral component comprises a distal taper configured to mate with a proximal taper of a stem.
20. The system of claim 1 , wherein the fins deform the insert when the insert is inserted into the humeral component.
21. The system of claim 1 , wherein the humeral component is configured to mate with a stem.