Total Hip Prosthetic Apparatus Made Of Non-porous Alumina

Abstract

A prosthetic apparatus designed to replace a natural articulation between bones including a first hemispherical piece having a plurality of discontinuities on the outer convex surface thereof for attachment to a first bone and having an anchoring projection extending therefrom having an axis offset from the axis of the hemispherical piece, and a second elongated piece attached to a second bone and having a head portion providing the cooperating surface with the hemispherical piece.

Description

The present invention relates to improvements in a prosthetic device designed for replacing a natural articulation between two bones, including a first piece attached to the first bone, a second piece attached to the second bone, the cooperating surfaces being made from non-porous alumina, the second piece consisting of two elements, one of which is a metallic rod, and the other a head which is secured to the metallic rod and which comprises the cooperating surface of this second piece. It is concerned more particularly with a prosthetic device for coxo-femoral articulation.

The attachment of each of the pieces onto the corresponding osseous portion may be effected either with the aid of a cement, or by ossification inside pores or striae.

Actually, the use of a cement, which is generally an acrylic cement, presents disadvantages by reason of its nature as an organic synthetic resin which is more or less well tolerated by the organism. This is the reason why the attachment by ossification within pores or striae is preferable. Nevertheless, the usual porosity of fritted alumina (pores with a dimension in the order of 20 microns) involves the risk of not allowing for a sufficient penetration of the pores by the osseous cells, because of their dimensions, and consequently producing too fragile an attachment of the piece on the corresponding osseous part.

The present invention aims at remedying the above-mentioned disadvantages and at attaining a solid attachment of the piece of the prosthetic device on the corresponding osseous part by ossification.

The prosthetic device according to the present invention is characterized in that the part of at least one of the two pieces which comes into contact with the osseous portion to which it must be attached comprises anfractuosities, at least two dimensions of which are in the order of a millimeter. Tests carried out by applicant have shown, in fact, that the natural ossification completely fills up anfractuosities in the order of a millimeter, thus assuring a solid and homogeneous attachment of the piece joined to the corresponding bone.

In the case of a total prosthetic device of the hip comprising a first piece attached to the hipbone, this acetabular piece and a second piece attached to the femur. The convex face of the first piece comprises preferably anfractuosities consisting of grooves whose width and depth are in the order of a millimeter.

The convex face of the first piece comprises preferably, along with these grooves, or independently of the latter, at least one anchoring projection for reinforcing the mechanical anchoring which is provided. The presence of the anchoring projection or stud facilitates the placement of the acetabular piece into a milled portion of the acetabulum. This anchoring projection is placed in position in a previously bored seat in the acetabulum and assures the guidance of the milling tool. It contributes furthermore to the mechanical bond by reossification.

It might appear advantageous to dispose the anchoring projection coaxially to the remainder of the acetabular piece. Nevertheless, the bottom of the acetabulum or socket has a relatively small thickness in the axis of the acetabular piece and it is not very spongy relatively speaking, which is in turn not very favorable for the desired reossification process.

In accordance with another characteristic of the present invention, the anchoring projection, or at least one of these in case the acetabular piece comprises several of them, has an axis different from that of the rest of this piece, traversing an area of the acetabulum having a thickness greater than that traversed by the axis of the rest of the piece. Furthermore, the area of the acetabulum in which the anchoring projection will come to be positioned is in that case of a spongy nature, which is favorable for the reossification process.

According to a first embodiment of the present invention, the axis of the anchoring projection forms an angle of about 10.degree. with that of the rest of the acetabular piece.

According to another embodiment of the present invention, the axis of the anchoring projection is parallel to that of the rest of the acetabular piece.

The acetabular piece may, however, comprise a second anchoring projection whose axis coincides with its natural axis in the case where an axial centering of the acetabular piece at the moment of its positioning appears advantageous.

The anchoring projection and/or projections are preferably provided with anfractuosities analogous to those of the convex surface of the acetabular piece with a view toward facilitating the reossification process at the contact surfaces.

Described hereinafter by way of example and with reference to the accompanying drawings are acetabular pieces according to the present invention.

FIG. 1 is a profile view, partially in section, of an acetabular piece comprising a coaxial anchoring projection;

FIG. 2 is a plan view of the piece shown in FIG. 1;

FIG. 3 is a cross-sectional view of a coxo-femoral prosthesis comprising an acetabular piece, such as that shown in FIG. 1;

FIG. 4 is a cross-sectional view of a coxo-femoral prosthesis comprising an acetabular piece with an anchoring projection whose axis is angularly shifted with respect to the axis of the acetabular piece and intersects the latter in the center of the spherical envelope of the exterior surface of the acetabular piece;

FIG. 5 is a schematic view of an acetabular piece with an anchoring projection having the axis thereof angularly shifted with respect to its proper one, but intersecting the latter beyond the center of the spherical envelope of its exterior surface;

FIG. 6 is a schematic view of an acetabular piece with an anchoring projection having the axis thereof angularly shifted with respect to its proper one, but intersecting the latter on this side of the center of the spherical envelope of its exterior surface; and

FIG. 7 is a schematic view of an acetabular piece with an anchoring projection having the axis parallel to the normal one thereof.

The acetabular piece shown in FIGS. 1 and 2, the female portion of the coxo-femoral articulation, is made from alumina obtained by fritting. It is made essentially with a hemispherical form or shape and comprises notably a concave face 4 smoothed and ground. This face is the one which assures the contact between the two pieces of the articulation. The convex face 1 which serves for the attachment to the osseous matter comprises anfractuosities consisting of grooves 2 and 3 which are respectively disposed along parallel meridian lines of the sphere.

Furthermore, this piece comprises an anchoring projection 5 which is located substantially at the top of the hemisphere. This projection improves the mechanical linkage or connection between the aforementioned piece and the osseous part to which it is attached. Moreover, the projection may in turn also be provided with anfractuosities, and the total length of the latter will thus be increased.

By way of example, the grooves 2 and 3 may have a width of 1.2 mm and a depth of 1 mm. In the example illustrated, the grooves, such as grooves 2, are 12 in number, and those such grooves 3 are eight in number. But this may not be necessarily so. Likewise, the shape and arrangement or provision of these grooves may also be different.

Other modifications with respect to detail may also be applied to the present invention without departing from the spirit and scope thereof. Nevertheless, the rod which serves for the implantation thereof may also comprise, in the same manner as the acetabular piece described, anfractuosities which assure its fixation, or attachment, by means of natural ossification. Moreover, these anfractuosities, at least two dimensions of which are in the order of a millimeter, do not necessarily constitute a network of grooves; they may instead be detached and distributed more or less regularly. They can be obtained by pressing, for example.

As is shown in and apparent from FIG. 3, it is not possible to embed an acetabular piece of this type unless the bottom of the acetabulum or socket 6 has a sufficient thickness. Furthermore, any possible displacing force or stress on the piece in the housing thereof automatically results in a reaction in the peripheral zone or area of the acetabulum or socket in the vicinity of the acetabular piece, in the new osseous cells of reossification.

In FIG. 4 the prosthetic device for the articulation of the hip according to the present invention consists of an acetabular piece 1, of a femoral piece 12 equipped with a spherical head 13 forming a ball-and-socket joint with a spherical housing 14 arranged in the piece 1. The metallic piece 12 is fixed or secured in the femur and the piece 1 is fixed or secured to the acetabulum or socket, but the anchoring projection 15 is not disposed according to the axis OO' of the acetabular piece and the axis XY thereof forms a certain angle, for example about 25.degree., with the axis of symmetry 00'. The axis XY intersects the latter at the center 16 of the spherical envelope of the exterior surface 17 of the acetabular piece. This provision allows for placing or embedding the anchoring projection 15 in an osseous portion that is more solid and thicker, and whose spongy nature is more favorable than that of the bottom 6 of the socket (FIG. 3) for the reossification process.

In FIG. 5 the axis XY of the projection 15 will come to intersect the axis of symmetry 00' of the acetabular piece beyond the center 16 of the spherical envelope of the exterior surface thereof. The axis XY thus forms a certain angle with the radius of the spherical envelope of the acetabular piece.

In FIG. 6 the axis XY of the projection 15 will come to intersect the axis of symmetry 00' of the piece in a point 18 on this side of the center 16.

In FIG. 7 the axis XY of the projection 15 is parallel to the axis of symmetry 00' of the acetabular piece.

In these different cases, as seen in FIGS. 5-7, the lack of axial symmetry of the acetabular piece, by virtue of the position of the anchoring projection thereof, opposes any possible displacing force or stress of this piece in the housing thereof, a positive reaction in a solid and healthy part of the socket.

It is understood, moreover, that, in the case where the axial centering of the anchoring projection with respect to the axis 00' appears advantageous, the acetabular piece may have two projections, one of which is on the axis 00'. This piece may also have several projections, and the form or shape of the latter may be different from that of a cylinder (conical, in the form of a truncated cone, or parallelepipedal, for example). These projections may constitute an integral part of the acetabular piece or they may be added thereto. For reasons of facilitating the placement or positioning of the acetabular piece, one or several projections may quite possibly not be integral with the acetabular piece, but instead may be disposed in housings arranged in the latter.

The acetabular piece may have a cross section different from that of a portion of the sphere, with preferably an axial symmetry, not taking into account the anchoring projection and/or projections. It may have, moreover, like the complete prosthetic device or apparatus, either one or several of the secondary characteristics defined or set forth herein.

Claims

What is claimed is:

1. A prosthetic apparatus designed to replace a natural articulation between two bones, comprising a first hemispherical piece consisting of non-porous alumina to be attached to a first bone by reossification, a second elongated piece to be attached to a second bone, cooperating surfaces on said first and second pieces being formed from non-porous smoothed and ground alumina, the second piece consisting of two portions, one portion of which is a metallic rod and the other portion of which is a head consisting of non-porous alumina secured to the metallic rod, said head providing the cooperating surface of said second piece, the outer convex portion of said hemispherical first piece which is to come into contact with an osseous part of the bone to which it must be secured by reossification including a plurality of anfractuosities of a size sufficient to permit ingrowth of osseous cells, and means for anchoring said first piece to said first bone including a first anchoring projection extending from said outer convex portion along the axis of symmetry of said first piece and a second anchoring projection extending along an axis different from and parallel to the axis of symmetry of said first piece, so that the second anchoring projection will extend into an area of the bone to which it is to be attached which is thicker than the area through which the axis of said first anchoring projection extends.

2. A total prosthetic apparatus of the hip according to claim 1, characterized in that the first and second anchoring projections are provided with anfractuosities analogous to those of the convex face of said first piece.

3. A total prosthetic apparatus of the hip according to claim 1, wherein at least two dimensions of said anfractuosities are in the order of a millimeter.

4. A total prosthetic apparatus of the hip, comprising a first hemispherical piece consisting of non-porous alumina to be attached to the hip bone by reossification, a second elongated piece to be attached to the femur, cooperating surfaces on said first and second pieces being formed from non-porous smoothed and ground alumina, the second piece comprising two portions, one portion of which is a metallic rod and the other portion of which is a spherical head consisting of non-porous alumina secured to the metallic rod, said spherical head providing the cooperating surface of said second piece, the outer convex portion of said hemispherical first piece which is to come into contact with the osseous part of the hip bone to which it must be secured by reossification including a plurality of anfractuosities of a size sufficient to permit ingrowth of osseous cells, a first anchoring portion extending from the top of said hemispherical first piece and coaxial therewith, and at least another anchoring portion extending also from said other convex portion and having an axis parallel to the axis of symmetry of the first piece, and adapted to be fitted into an area of the hip bone which is thicker than the area through which the axis of symmetry of the first piece extends.

5. A total prosthetic apparatus of the hip according to claim 4, wherein the anchoring projections are provided with anfractuosities analogous to those of the convex face of said first piece.

6. A total prosthetic apparatus of the hip according to claim 4, wherein at least two dimensions of said anfractuosities are in the order of a millimeter.