Shoulder Joint Prosthesis

Abstract

A reverse shoulder joint prosthesis (1) for location between a humerus and a scapula comprised a ball (5) to be fixed to the scapula and a humeral stem 6 to be fixed to the humerus. The prosthesis comprises a first cup (2), a second cup (3) and a plate (4) retained between said cups. The first cup is free to move about the ball. The plate has a trunion (16) adapted to connect to the humeral stem through an aperture in the second cup. The plate is free to move between the cups. The prosthesis has a first phase of movement in which the plate moves between the cups and a distinct second phase of movement in which the first cup moves on the ball. The shoulder joint prosthesis provides an extended range of movement through the provision of two motion phases while minimising wear, scapula infringement and instability.

Claims

1. A shoulder joint prosthesis for location between a humerus and a ball member in a scapula, the prosthesis comprising a first cup and a second cup and a plate retained between said cups; wherein the first cup is adapted to move about the ball member; wherein the plate is adapted to connect to the humerus through the second cup; and wherein the plate is adapted to move about the first cup.

2. A shoulder joint prosthesis according to claim 1 wherein the first and second cups each comprise a convex surface facing the humerus and a concave surface facing the ball member.

3. A shoulder joint prosthesis according to claim 1 wherein the first cup is in contact with not more than 40% of the contactable area of the ball member at any time.

4. A shoulder joint prosthesis according to claim 1 wherein the first and second cups are adapted to attach to each other with the plate retained between them.

5. A shoulder joint prosthesis according to claim 4 wherein the first and second cups attach together around their respective peripheries.

6. A shoulder joint prosthesis according to claim 1 wherein one or both cups comprise an abutment wherein in use contact of the plate with the abutment initiates free movement of the first cup about the ball member.

7. A shoulder joint prosthesis according to claim 1 wherein the second cup comprises an aperture through which the plate can be connected to the humerus.

8. A shoulder joint prosthesis according to claim 1 wherein the plate comprises a trunion adapted for attachment directly or indirectly to the humerus.

9. A shoulder joint prosthesis according to claim 8 wherein the plate is secured to the humerus via a humeral stem adapted to be inserted into the humerus.

10. A shoulder joint prosthesis according to claim 1 wherein the prosthesis includes said ball member, which is adapted for securement to the scapula.

11. A shoulder joint prosthesis according to claim 1 wherein the plate comprises a metal.

12. A shoulder joint prosthesis according to claim 1 wherein the first and second cups each comprise a polymeric material.

13. A shoulder joint prosthesis according to claim 1 adapted for use in a reverse shoulder joint replacement.

14. A shoulder joint prosthesis according to claim 1 adapted to provide two phases of movement, wherein the first phase comprises the movement of the plate about the first cup and the second phase comprises the movement of the first cup about the ball member.

15. A shoulder joint prosthesis according to claim 6 wherein in use the motion of the prosthesis comprises first and second motion phases, wherein: the first phase comprises the movement of the plate about the first cup and is limited by the extent of the movement of the plate on the first cup; and the second phase comprises the movement of the first cup about the ball member and is initiated by the extent of the movement of the plate on the first cup.

16. A shoulder joint prosthesis for placement between a humerus and a scapula, the prosthesis comprising: a ball member securable to a scapula; a humeral insert securable to a humerus; and a first cup and a second cup and a plate retained between said cups; wherein the first cup is free to move about the ball member; wherein the plate is adapted to connect to the humeral insert through the second cup; and wherein the plate is free to move about the first cup.

17. A method for replacing a shoulder joint with a shoulder joint prosthesis comprising: locating a shoulder joint prosthesis between a humerus and a ball member in a scapula; wherein the prosthesis comprises a first cup and a second cup and a plate retained between said cups; wherein the first cup and second cup are attached together; wherein the prosthesis is secured to the humerus by direct or indirect attachment of the plate to the humerus through the second cup; wherein the first cup is free to move about the ball member; and wherein the plate is free to move about the first cup.

18. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] For a better understanding of the invention, and to show how exemplary embodiments of the same may be brought into effect, reference will be made, by way of example only, to the accompanying diagrammatic figures, in which:

[0055] FIG. 1 shows the components of a shoulder joint prosthesis according to an embodiment of the invention;

[0056] FIGS. 2a and 2b are views of a first cup according to the embodiment of FIG. 1;

[0057] FIGS. 3a and 3b are views from different angles of a second cup according to the embodiment of FIG. 1;

[0058] FIGS. 4a and 4b are views from different angles of a plate according to embodiment of FIG. 1;

[0059] FIG. 5 shows the first cup, the plate and the second cup according to the embodiment of FIG. 1 in a perspective expanded view;

[0060] FIG. 6 depicts the shoulder joint prosthesis according to the embodiment of FIG. 1 wherein the first cup and the second cup are attached together enclosing the plate therebetween; wherein the first cup is in contact with a ball member and showing a humeral stem to be engaged with the plate;

[0061] FIG. 7 depicts the assembled shoulder joint prosthesis according to the embodiment of FIG. 1 wherein the first cup and the second cup are attached together retaining the plate, the first cup is in contact with the ball member and wherein the humeral stem is engaged with a trunion of the plate; and

[0062] FIGS. 8 to 11 depict the shoulder joint prosthesis of FIG. 1 wherein the humeral stem is in different positions corresponding to movement of an attached humerus.

DETAILED DESCRIPTION OF THE INVENTION

[0063] FIG. 1 shows in an expanded view the components of a prosthesis 1 comprising a first cup 2 and a second cup 3 and a plate 4 to be retained between the cups 2 and 3. The first cup 2, second cup 3 and plate 4 are located between a ball member 5 and a humeral stem 6.

[0064] The prosthesis is a reverse shoulder prosthesis. Thus the ball member 5 is secured in use to the scapula of a patient, and the stem 6 is introduced into the humerus.

[0065] FIGS. 2a and 2b show the first cup 2 comprising a convex surface 7 and a concave surface 8. In use the concave surface 8 is adapted to freely move about the ball member 5. The convex surface 7 is adapted so that the plate 4, held captive between the cups 2 and 3, can freely move about the convex surface 7. The first cup 2 comprises an abutment 9 extending outwards about the periphery of the first cup 2. The abutment 9 extends completely about the circumference of the first cup 2. The abutment 9 is formed as a continuous rim of the first cup 2. As shown the abutment 9 may comprise a ridge 9 and a comparatively lower portion 9. As will be further explained the abutment 9 facilitates attachment of the second cup 3 to the first cup 2.

[0066] As shown in FIGS. 3a and 3b the second cup 3 comprises a convex surface 10 and a concave surface 11. The second cup 3 comprises an aperture 12. The second cup comprises a groove 13 extending around the edge of the concave surface 11. The groove 13 comprises an area of reduced thickness compared to the rest of the second cup 3. The groove 13 extends completely about the circumference of the second cup 3. The groove 13 corresponds to the abutment 9 of the first cup 2. In use the first cup 2 and second cup 3 are attached securely to each other by means of the complementary abutment 9 and groove 13. In use the plate 4 is retained by the attachment of the second cup 3 to the first cup 2. The plate is captive between the cups but is free to move between them, in engagement with their respective opposed convex and concave surfaces.

[0067] As shown in FIGS. 4a and 4b the plate 4 comprises a convex surface 14 and a concave surface 15. The plate 4 comprises a trunion 16 projecting from its convex surface 14. The trunion 16 has a Morse taper, away from the convex surface 14 of the plate. The trunion 16 is formed as an integral part of the plate 4.

[0068] FIG. 5 shows a perspective view of the first cup 2, plate 4 and second cup 3 looking generally towards the concave surface 8 of the first cup. The plate 4 is located between the first cup 2 and second cup 3. The trunion 16 of plate 4 extends through the aperture 12 of second cup 3.

[0069] FIG. 6 shows the configuration of the prosthesis 1 when the first cup 2 and second cup 3 have been attached together. The plate 4 is retained between the first cup 2 and second cup 3. The trunion 16 of plate 4 protrudes through the aperture 12 of second cup 3. The first cup 2 is almost completely enclosed within second cup 3. The second cup 3 attaches to the first cup 2 by means of the abutment 9 so that only a portion of the abutment 9 of the first cup 2 remains visible, when seen from the side. The first cup 2 is in contact with the ball member 5. The stem 6 is shown ready for insertion into the humerus and attachment to the trunion 16 of the plate 4.

[0070] FIG. 7 shows the shoulder joint prosthesis 1 fully assembled and located between the stem 6 and ball member 5. The trunion 16 of plate 4 is attached to the stem 6. The stem 6 is adapted to be inserted in the humerus. The attachment of trunion 16 of plate 4 to the stem 6 secures the shoulder joint prosthesis 1 to the humerus.

[0071] FIGS. 8 to 11 show movement of the stem 6 causing movement of the trunion 16 and consequently of the plate 4 causing the first cup 2 to move about the ball member 5. The plate 4 is free to move about the first cup 2 until the edge of the plate abuts the abutment 9 of the first cup 2. The plate-halting mechanism limits the movement of the plate 4 about the first cup 2. Small movements are thus enabled and wear problems are limited by stopping the free movement of the plate 4 about the first cup 2.

[0072] In use in a reverse shoulder replacement configuration the ball member 5 is secured to the scapula of a patient, and the stem 6 is introduced into the humerus.

[0073] In use, when a larger range of movement is required the plate 4 impacts against the abutment 9 of the first cup 2. This action is not visible in the figures as the plate 4 and the first cup 2 are located within the second cup 3. By these means the movement of the plate is stopped and a second phase of motion is initiated involving the free movement of the first cup 2 about the ball member 5. The second phase of motion enables a wider range of movement, limited by the rotator cuff of the shoulder. The plate 4 remains at the abutment 9 during this second phase of motion. The plate 4 will begin to move again when the stem 6 moves back to a central location corresponding to movement of the attached humerus.

[0074] Although a preferred embodiment has been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

[0075] In summary, the invention provides a shoulder joint prosthesis for use in a reverse shoulder joint replacement. The shoulder joint prosthesis provides movement over a wide range by providing a mechanism for two phases of motion but without increasing wear and with less scapula impingement and instability

[0076] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0077] All of the features disclosed in this specification (including any accompanying claims and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[0078] Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0079] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.