Prosthesis for the trapeze-metacarpal joint of the thumb

Abstract

A prosthesis (1) for the trapeze-metacarpal joint of the thumb comprises a body (2) suitable for being arranged between the scaphoid (31) and the metacarpus (30) of the thumb, such body (2) has the shape of an Archimedean solid and operates as a spacer between the scaphoid (31) and the metacarpus (30).

Claims

1. A trapezium prosthesis (1) for the trapezio-metacarpal joint of the thumb, said trapezium prosthesis (1) comprising a solid body (2) having an inner core (3), said solid body (2) suitable for being arranged between the scaphoid (31) and the metacarpus (30) of the thumb, said solid body being suitable for operating as a spacer between said scaphoid (31) and metacarpus (30), characterized in that the solid body (2) has the shape of an Archimedean solid having a plurality of facets (17), wherein the solid body (2) is provided with surface grooves (16) between the facets (17), wherein a net or grid (10) is wrapped around the solid body (2), and wherein portions of said net or grid (10) are inserted into the surface grooves (16) of the solid body (2), and wherein the trapezium prosthesis further comprises fixing means (13, 18) suitable for allowing a constraint of the solid body (2) to the scaphoid (31) and the metacarpus (30).

2. A trapezium prosthesis according to claim 1, wherein said net or grid (10) comprises a non absorbable thread, said non absorbable thread made from a material selected from the group consisting of prolene or nylon.

3. A trapezium prosthesis according to claim 1, wherein said body is made of a material selected from the group consisting of Goretex, Dacron, or PTFE.

4. A trapezium prosthesis according to claim 1, wherein said fixing means comprises at least two eyelets (13) projecting from said net or grid (10) or, alternatively, at least two eyelets (18) projecting directly from the solid body (2) of the prosthesis and integral therewith.

5. A trapezium prosthesis according to claim 1, wherein the solid body (2) has the shape of an icosahedron.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) For a better understanding of the present invention the following drawings are attached for merely explanatory, hence non limitative, purposes, wherein:

(2) FIG. 1 shows a front view of a prosthesis according to the invention;

(3) FIG. 2 shows a top view of the prosthesis in FIG. 1;

(4) FIG. 3 shows a schematic transparent view of a hand in which the prosthesis in FIG. 3 is inserted;

(5) FIG. 4 shows a perspective view of the prosthesis in FIG. 1, a portion being cutaway for the sake of clearness;

(6) FIG. 5 shows a front view of a variant of the prosthesis in FIG. 1;

(7) FIG. 6 shows a schematic transparent view of a hand in which the prosthesis in FIG. 5 is inserted; and

(8) FIG. 7 shows a perspective view of the prosthesis in FIG. 5, a portion being cutaway for the sake of clearness.

DETAILED DESCRIPTION OF THE INVENTION

(9) In the attached figures, identical or corresponding parts are identified by the same reference numerals.

(10) With reference to FIGS. 1-4, they show a first embodiment of the invention wherein the prosthesis is generically referred to with the reference numeral 1 and comprises a solid body 2 made of a biocompatible material. For instance, the latter can be made of Goretex, Dacron, or PTFE.

(11) The body 2 might include, as shown in FIG. 4, a metal core 3 suitable for making the prosthesis 1 visible in a X-ray examination.

(12) Such body 2 has the shape of an Archimedean solid and such as to occupy at best the space that is occupied by the trapezium in the hand. During a surgical operation, whenever such bone (trapezium) is removed from the hand, a substantially cubic space is created which is just filled at best by the shape of the Archimedean solid of the prosthesis. The body 2 is thus positioned between the metacarpus 30 and the scaphoid 31 of the hand and operates as a spacer between these bones; the base 32 of the metacarpus 30 rests thereupon.

(13) Advantageously the body 2 is wound by a non absorbable thread 10 for instance made from nylon, prolene, or another material that facilitates the incorporation and the fixing of the body 2 in the tissue of the hand so as to stimulate the fibrous response of the body or of the surrounding tissue.

(14) In order to fix the body in position, such net includes at least two eyelets or eyes 12 and 13, located in opposed positions, through which it is possible to make one or more suture threads (not shown), preferably of a non absorbable type, pass through around tendon or capsule structures in order to anchor the prosthesis 1 therebetween.

(15) The net 10 can include more than two eyelets indeed to constrain the prosthesis to the bones of the hand too.

(16) In FIGS. 5, 6, and 7, the prosthesis 1 has the shape of a regular icosahedron, i.e. a solid body featuring a plurality of facets. The body here considered can have surface grooves 16 between the individual hexagonal and pentagonal faces 17 of the prosthesis, or not; in such grooves or in any case on the surface of the body 2 there is placed a net or grid 10 (for instance made from nylon or prolene) as with the embodiment shown in FIGS. 1-4.

(17) The prosthesis 1 also includes a number of projecting eyelets 18, integral with the body 2, for constraining (by means of a suture thread) the prosthesis to the tendon or capsule structures.

(18) The solution illustrated in FIG. 5 can also have a metal core in order to make the prosthesis detectable with a X-ray examination.

(19) The insertion of the prosthesis 1 into the hand takes place in a way similar to that already described with respect to FIGS. 1-4, hence such insertion mode is not further described.

(20) Thanks to its shape, the prosthesis 1 is easily insertable into the hand in the space cleared upon removing the trapezium. As a matter of fact, no preferred direction exist for such insertion because the body 2 has the shape of an Archimedean solid which does not have any preferred part for getting in contact with the adjacent bones. Its faceted shape guarantees a limited slip onto the surfaces of the adjacent bones (which do not necessarily require a surface treatment to co-operate with those of the prosthesis); this occurs thanks to the greater friction generated between the flat faces of the prosthesis and the bones as referred to the friction that is generated between the curved surfaces of the prosthesis according to the status of the art and the bones.

(21) Furthermore, such body is easy to handle and, thanks to the net-like configuration of the part (net 10) that winds it, it can be easily incorporated into the adjacent periprosthesic tissues. As a matter of fact, such net or grid 10 stimulates a fibrous proliferation of the body that receives the prosthesis, hence anchoring and strength as well as the incorporation and the prosthesic strength of the implant in the replacement area.

(22) Various embodiments of the invention have been described. However, others are considered to be obtainable on the basis of the previous description: for instance, the body 2 might have a number of facets different from those of the icosahedron, while retaining a shape of various and known Archimedean solids. Such variants of the invention shall also to be considered to fall within the scope of the following claims.