Prosthetic Shoulder Joint

Abstract

A prosthetic scapular device is provided having a generally cup-shaped member, normally of a hemispherical form at least internally, and intracancellous fixation means extending from approximately one half only of the outer surface of the cup. The fixation means, normally in the form of mutually divergent spikes, include long members extending from points adjacent the central radial plane of the relevant cup half and diverge in the same sense from such plane, together with short members on opposite sides of such plane. Preferably, the long members increase in length and divergence from said plane as they approach the cup rim.

Description

This invention concerns prosthetic shoulder joint devices and it is intended to permit complete replacement of shoulder joints affected by disease or injury.

It appears, at least from the currently available range of prosthetic devices, that no successful attempt has been made previously to permit complete shoulder joint replacement. The available devices include humeral head prostheses, but no associated glenoid prosthesis. Moreover, implantation of the existing humeral head devices usually involves removal of the rotator cuff muscles, and the resultant implant is liable to dislocate.

The present invention seeks to alleviate this situation by effectively providing a prosthetic glenoid cavity for co-operation with a prosthetic humeral head.

According to the invention there is provided a prosthetic scapular glenoid device comprising a generally cup-shaped member having intracancellous fixation means rigidly connected to or integral with, and extending from, approximately one half only of the outer surface of said member.

The glenoid cup, as said member may be termed, will normally be substantially hemispherical, at least over its inner surface.

In a preferred form the fixation means comprise a plurality of mutally divergent spike-like elements, including both long and short spikes. The longer spikes stem from a succession of points adjacent the central radial plane of the relevant half of the cup, and they diverge in the same sense slightly away from such plane. As will be seen hereinafter from an illustrated embodiment the longer spike of greatest length and divergence from the central radial plane is that closest to the rim of the cup.

The associated shorter spikes are located on both sides of the succession of larger spikes and within the relevant half cup surface.

As an indication of the more particular shaping and dimensioning of a device as just described, the cup has an internal diameter of about 3/4 inch and external diameter of about 1 inch, the longer spikes range from about 1/2 to 1 inch in length with respective divergence of about 9.degree. and 13.degree. from the central radial plane, and the shorter spikes are about 1/8 inch in length.

While it is presently preferred to employ spike-like elements as fixation means, this is not essential. For example, the role of some or all of the longer spikes may be served by an appropriately shaped web and the role of some or all of the shorter spikes may be served by ribs.

An associated prosthetic humeral head device for use with a cup as just described may be of any suitable form given that it comprises a ball-like head part which can, when the device is implanted, be presented to the cup to form an appropriate ball-and-socket joint. This point will become clearer after consideration of the illustrated embodiment hereinafter and the desired relative attitudes of the joint parts.

However, a preferred form of the latter device comprises a rod-like intramedullary fixation part integrally formed with a ball-like humeral head part at one end, the longitudinal axis of the head part being turned from that of the fixation part by about 45.degree. .

For a fuller understanding of the present invention, the same will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 shows one embodiment of a glenoid device according to the invention in plan view,

FIGS. 2 and 3 are side views of the embodiment of FIG. 1 as seen in the directions indicated at A and B,

FIGS. 4, 5 and 6 are sectional views respectively taken at C -- C, D -- D, and E -- E in FIG. 1,

FIGS. 7 and 8 are sectional views respectively taken at F -- F, and G -- G in FIG. 2,

FIG. 9 is a sectional view taken at H -- H in FIG. 3,

FIG. 10 is a plan view of the cup of FIG. 1 showing the co-ordinate positions of the fixation means,

FIG. 11 is a diametral section of the cup of FIG. 1,

FIGS. 12 and 13 respectively show an associated embodiment of a humeral head device according to the invention in plan and side views,

FIGS. 14 and 15 are sectional views respectively taken at I -- I, and J -- J in FIG. 13, and

FIGS. 16 and 17 diagrammatically illustrate the manner of implantation of the illustrated devices.

The illustrated glenoid device comprises a substantially hemispherical cup 1 and a plurality of mutually divergent, spike-like fixation means 2 to 6 of the preferred form described above. It will be seen that the spikes 2 to 6 extend from substantially one half of the exterior of the cup as separated by the diametral plane in the direction A of FIG. 1, the longer spikes 2, 3 and 4 extend from a succession of points adjacent the central radial plane in the direction B of FIG. 1 and diverge from the latter plane in the same sense, and the shorter spikes 5 and 6 are located on opposite sides of the succession of longer spikes. The two spikes 2 and 3 of the longer spikes are of similar length and similar lateral inclination to the central radial plane, while spike 4 nearest the rim of the cup is of greater length and lateral inclination than spikes 2 and 3.

More particular details of the illustrated glenoid device are given by the following table of dimensions, each dimension being denoted by a reference numeral and letter of which the former denotes the relevant figure of the drawing and the latter the dimension in that figure, and the dimension value being given in inches unless otherwise denoted as an angle.

1a 13.degree. 6a 22.5.degree. 8b 9/16 10c 0.060 10h 0.4333 3a 13.degree. 7a 13.degree. 9a 25.degree. 10d 0.110 11a 0.750 4a 13.degree. 7b 13.degree. 9b 0.125 10e 0.150 11b 0.960 5a 25.degree. 7c 9/16 10a 0.245 10f 0.030 11c 0.067 5b 7.degree. 8a 9.degree. 10b 0.215 10g 0.235 11d 0.547

The associated humeral device illustrated by FIGS. 12 to 15 is detailed in similar manner by the following table:

12a 11/32 13d 13/32 13j 1/4 13p 23/16 14c 11/32 12b 9/32 13e 5/8 13k 7/16 13q 39/8 14d 37/32 12c 21/16 13f 3/4 13l 5/2 13r 1/16 15a 1/8 13a 0.750 13g 67.5.degree. 13m 1 14a 37/64 15b 3/16 13b 7/32 13h 21/16 13n 5/16 14a 33/32 15c 1/16 13c 1/16 13i 45.degree. 13o 37/16

Regarding materials: the illustrated devices can be conveniently made of cobalt-chromium alloy as is often the case with such devices. However this is not essential since the glenoid device may equally well be made of titanium housing a high-density polythene insert as a bearing liner. The liner is conveniently of hemispherical cup form, retained by a spring circlip seated in an annular groove in the main cup adjacent to its rim. More generally, the associated devices may be made of any suitable materials, be they metal, plastics, ceramic, composite or combination thereof.

Lastly, it is appropriate to indicate the manner of implantation, and this is effected by reference to FIGS. 16 and 17.

The glenoid is excavated and cancellous bone removed to permit cementing or grouting of the device in position, as shown, with acrylic resin or other suitable material. When correctly positioned the cup should lie at an angle of about 60.degree. to the horizontal plane as viewed anteriorly, and should lie at an angle 10.degree. to 13.degree. to the plane of the glenoid cavity as viewed from above.

The humeral device is similarly cemented or grouted into a preformed hole made in the humeral marrow cavity so that the ball-like head part engages the glenoidal device cup as shown.

Claims

We claim:

1. A prosthetic device for use as a human shoulder joint replacement, which device is designed to be used together with a self-hardening or self-curing gap-filling agent within cavities cut in the bone of the scapular glenoid and humerus, comprising:

a scapular glenoid first bearing member having a part-spherically shaped first bearing surface;

intracancellous first fixation means connected or integrally formed with said first member;

said first fixation means projecting from said first member along a succession of points adjacent a symmetrically disposed radial plane of said first surface, said succession of points extending between a central portion and one edge portion of said first member as intersected by said plane, said first fixation means projecting further from said member at said one edge portion than from said central portion, and said first fixation means diverging from said plane to one side thereof with increasing projection from said first member;

a humeral second bearing member having a part-spherically shaped second bearing surface complementary to and rotatably received by said first bearing surface;

and intra-medullary second fixation means connected or integrally formed with said second member;

said second fixation means including an elongate tapered projecting from said second member to terminate in a tapered stem.

2. A device according to claim 1 wherein said fixation means project from said first bearing member by distances in the range of about 1/2 inch to 1 inch, the divergence of said first fixation means increases in the range of about 9.degree. to 13.degree. relative to said plane with progression along said succession of points towards said edge portion, and said second fixation means projects from said second bearing member while turning through an angle of about 45.degree. relative to the longitudinal axis of said tapered stem.

3. A prosthetic device for use as a scapular glenoid replacement, which device is designed to be used together with a self-hardening or self-curing gap-filling agent within cavities cut in the bone of the scapular, which device comprises:

a cup to act as a scapular glenoid replacement and having a part-spherically shaped inner surface, a generally convex outer surface, and a rim joining said inner and outer surfaces;

intracancellous fixation means connected or integrally formed with said cup and for bonding in said gap-filling agent;

said fixation means projecting from said outer surface along a succession of points adjacent a plane which is radially and symmetrically disposed relative to said inner surface;

said succession of points extending between a central portion of said outer surface and an edge portion of said outer surface where said plane makes one intersection with said rim;

said fixation means projecting further from said outer surface at said edge portion than from said central portion;

and said fixation means diverging from said plane to one side thereof with increasing projection from said outer surface.

4. A device according to claim 3 wherein the divergence of said fixation means from said plane increases with progression along said succession of points toward said edge portion, said divergence being in the range of about 9.degree. to 13.degree. relative to said plane.

5. A device according to claim 3 wherein said fixation means comprise a plurality of spike-like members, the geometrical projections of which in said plane are mutually divergent.

6. A device according to claim 3 wherein said fixation means project from said cup by distances in the range of about 1/2 inch to 1 inch, and further comprising relatively shorter fixation means projecting from said cup outer surface adjacent the first-mentioned fixation means and on both sides thereof relative to said succession of points.

7. A device according to claim 4 in combination with prosthetic humeral device comprising a head part having a spherically shaped bearing surface complementary to and received in said cup inner surface, and a fixation member projecting from said head part through a neck portion and terminating in a tapered stem, the longitudinal axis of said stem being disposed at about 45.degree. inclination relative to that of said neck portion adjoining said head part.