FR2677878A1 - Acetabular prosthesis - Google Patents

Abstract

Acetabular prosthesis comprising a frame of hemispherical shape intended to be implanted in the acetabular cavity, and an insert intended to bear in its inner recess and to receive the femoral head of a femoral prosthesis, characterised in that the outer surface of the said frame comprises at least one engagement fin formed by an engagement wall which projects from the outer surface of the said frame.

Description

COTYLOIDIAN PROSTHESIS
The present invention relates to an acetabular prosthesis and in particular a prosthesis intended to be impacted and possibly provided with screws.

 When an alteration of the hip joint for whatever reason occurs either through wear or by accident, it is generally not possible to envisage anything other than a surgical operation consisting in purely and simply replacing the natural joint by an artificial joint constituted by an artificial acetabulum placed in the acetabular cavity of the iliac bone cooperating with a femoral prosthesis implanted in the femur.

 There are already different models of total prosthesis and in particular of artificial cup, sometimes called cup which are constituted by a support frame or cup impacted in the acetabulum and an insert or friction cup in which the head of the artificial femur must take place.

 Despite the various improvements successively developed and perfected by surgeons and manufacturers, no acetabular prosthesis is completely satisfactory.

 The present invention therefore seeks to solve the drawbacks of current prostheses and proposes an acetabular prosthesis which allows optimal implantation ensuring excellent stability. Among other things, it allows a uniform distribution of the compression forces. According to the invention, the biological anchoring is completed by an anatomical mechanical anchoring which is particularly adapted to the different forces and in particular of shearing during hip movements.

 Thus the acetabular prosthesis according to the invention comprises a hemispherical frame intended to be implanted in the acetabular cavity, and an insert intended to take place in its internal housing and to receive the femoral head of a femoral prosthesis, and is such that the external surface of said reinforcement comprises at least one embedding fin constituted by an embedding wall which projects relative to the external surface of said armature.

 According to additional characteristics, the embedding wall is arranged in a diametral plane, and has a height which increases from the bottom to the top.

 According to another additional characteristic, the frame comprises at least two embedding fins arranged in two concurrent diametrical planes, while each of the walls comprises at least one hole.

 According to another characteristic of the invention which could constitute an invention in itself, the frame comprises a succession of indexing notches distributed on the underside of the equatorial edge, while the insert comprises a corresponding indexing projection.

 Other characteristics and advantages of the invention will emerge from the description which follows with reference to the appended drawings which are given only by way of nonlimiting examples.

 Figures 1 to 12 show a prosthesis according to one embodiment.

 FIG. 1 is a side view of the acetabular prosthesis, seen along F1 of FIG. 2.

 FIG. 2 is a top view of the acetabular prosthesis according to F2 of FIG. 1.

 FIG. 3 is a bottom view of the acetabular prosthesis according to F3 of FIG. 1.

 Figure 4 is a sectional view along IV-IV of the acetabular prosthesis.

 Figures 5, 6 and 6a show the frame.

 Figure 5 is a bottom view of the frame.

 Figure 6 is a sectional view along VI-VI of the frame.

 Figure 6a shows a detail on a larger scale.

 Figures 7, 8, 8a and g show the insert.

 Figure 7 is a top view.

 FIG. 8 represents a side view along F8 of FIG. 7.

 FIG. 8a shows a detail of FIG. 8 on a larger scale.

 FIG. 9 is a sectional view along Ix-Ix of FIG. 7.

 Figure 10 is a side view of a recessed fin of the frame.

 Figure 10a is a view similar to Figure 10 showing a variant.

 Figures 11 and 12 show an alternative embodiment of the insert.

 FIG. 11 is a view similar to FIG. 9.

 FIG. 12 is a view similar to FIG. 8.

 Figures 13 and 14 show another embodiment for the frame.

 Figure 13 is a bottom view.

 FIG. 14 is a section along AA of FIG. 13.

 As can be seen in the various figures, the acetabular prosthesis (1) comprises a frame (2) and an insert (3). The frame (2) is constituted by a metallic envelope of hemispherical shape and is intended to be fixed by impaction and possibly by addition of screws in the milled bone acetabulum in the hip bone.

The frame (2) is metallic. The metal alloy used is for example a titanium alloy to present good bio-compatibility with the bone in which the frame is intended to be implanted. The hemispherical insert (3) is intended to take place in the frame (1). This insert provides the interface between the head of the femoral prosthesis and the prosthetic acetabulum and is for example made of high density polyethylene to constitute the friction part of the hip joint.

The frame (2) has an interior housing (4) of complementary shape to the exterior profile (5) of generally spherical shape of the corresponding insert (3). The outer surface (6) of the frame is hemispherical in shape and is concentric with the inner housing to form a spherical wall (7) of thickness "E". Note that the interior housing (4) peripherally comprises a spherical interior surface (8) and at the bottom, a planar bearing surface (9). Furthermore, the frame (2) comprises a threaded hole (10) of axis X2X2 'corresponding to the general axis of symmetry passing right through the wall at the top (150) of said frame (2). The threaded hole (10) and the bearing surface (9) are intended to receive the impacting tool necessary for the installation of the frame.

 Furthermore, the spherical wall (7) comprises a set of fixing holes (11, lîa, lîb, lîc, îld, île, 11f, 1lg). Each of the holes is constituted by a cylindrical part (12) and on the side of the internal housing (4), by an enlarged part with spherical bearing (13) intended to receive screws for fixing the prosthesis in the hip bone. The spherical part (13) of the fixing holes comprises a spherical bearing surface (14) on which the fixing screw is supported. The fixing holes are for example distributed over four circular rows (R1, R2, R3, R4), parallel to the equatorial edge (15). Thus on the lower row or first row (R1) are located three fixing holes (1 1h, lld, 11f), while on the second row (R2) are distributed two holes (1 la, lic). The third row (R3) comprises for example a hole (lob) and the upper row or fourth row (R4) comprises two holes (llg, lle).

 According to a particular arrangement of the frame (2), its equatorial edge (15) comprises a succession of indexing notches (16) distributed regularly, intended to receive at least one indexing projection (17) produced on the 'insert (3), as we will see later. Thus, as shown by way of example, the lower surface (151) comprises twelve notches (16a, 16b, 16c, 16d, 16e, 16f, 1gag, 16h, 1gui, 16j, 16k, 161) of rectangular shape. The lower part of the interior surface (8) comprises two portions of cylindrical surfaces (18, 19) separated by a circular hollow profile (20). Note also that the interior housing (4) includes an inlet chamfer (21).

 According to a characteristic of the invention, the armature comprises two embedding fins (22, 23) each constituted by an embedding wall (24) which projects projecting perpendicularly to the external surface of the armature and in diametral plans. The first fin (22) extending in a diametral plane (P22), while the second fin (23) extends in another diametral plane (P23) concurrent with said diametrical plane (P22) of the first fin (2 ) to form an angle (A) which may for example be 800 or 900.

Each of the fins has the general shape of a crescent. Its wall has a constant thickness "e" which can be 0.5 to 1 millimeter and its height "h" varies to gradually increase from the bottom up.

Thus each fin includes a curved upper edge (240), the highest part of which is towards the top (150). Each embedding fin comprises for example three holes (25) further improving the implantation by ossification. FIG. 10a represents a variant according to which the upper edge (240) of the embedding wall is not curved, but consists of two straight converging edges, a first edge (240a) and a second edge (240b).

 According to a particular arrangement of the fixing holes (11), it will be noted that these are advantageously arranged in the area of the embedding fins. Thus four holes (lia, llb, llc, lid) are located between the two fins, while two other holes (1 le, 11f - llg, 11h) are located on the other side of each fin relative to the four holes ( lia, lib, lic, 11d).

 The outer surface (6) of the frame as well as the embedding fins is advantageously covered with a first thin layer of porous titanium and with a second outer layer of hydroxyapatite which, by its osteoconduction properties, allows the biological fusion between the bone and the implant and thus ensures a biological fixation in addition to the possible mechanical fixation. The hydroxyapatite coating is done using a vacuum plasma torch.

 As we have seen previously, the polyethylene insert (3) is intended to take place in the frame (2) and to receive the head of the femoral prosthesis. To this end, said insert (3) has a general hemispherical shape and comprises an internal hemispherical cavity (26) open downwards, the diameter of which corresponds to the operating clearance of the outside diameter of the femoral head which must be housed therein. It will also be noted that the internal cavity (26) comprises a spherical wall (261) terminated downwards by a cylindrical wall (262) and by a chamfer (260). The external profile (5) of the insert comprises at the top an upper support surface (27) planar and at its base, a circular projecting profile (28) intended to cooperate with the hollow profile (20) of the frame to constitute means of clipping between said frame and said insert.

 The insert (3) also comprises a peripheral rim (29) which projects laterally with respect to the external profile (5) and which is formed by a peripheral face (30), an upper face (31) and a lower face ( 32). The upper face (31) of the peripheral rim (29) comprises an indexing projection (33) intended to cooperate with one of the indexing notches (16) of the frame. The cooperation of the indexing projection (2) of the insert (3) with one of the notches of said frame making it possible, on the one hand, to condemn the pivoting of the insert in its frame around its axis, and to on the other hand, the choice of the notch making it possible to choose the optimal position and orientation of said insert (3).

 Figures 11 and 12 show an alternative embodiment of the friction insert (3). According to this variant, the insert (3) comprises a lateral antiluxation projection (35) which is intended to prevent untimely dislocation of the head of the femur. Thus, the lower face (32), instead of being perpendicular to the vertical axis X2X2 ', forms an inclined plane (P32) forming an angle B which is for example 100.

Similarly, the axis ZZ 'of the internal cavity is inclined by the same angle
B. Thus the peripheral face (30) of the peripheral rim (29) has a variable thickness.

 It is to correctly position this antiluxation projection (33) during implantation that the choice of the orientation of the insert (3) in the frame (2) is important and this is another advantage of the notches. successive (16).

 Figures 13 and 14 show another embodiment of a frame (2). As for the frame described above, the frame (2) is constituted by a metallic envelope of hemispherical shape and is intended to be fixed by impaction and possibly by addition of screws in the milled bone acetabulum in the hip bone. The frame (2) is metallic. The metal alloy used is for example a titanium alloy to exhibit good biocompatibility with the bone in which the framework is intended to be implanted. The frame (2) has an interior housing (4) of complementary shape to the outside profile (5) of generally spherical shape of the corresponding insert (3). The outside surface (6) of the frame is of hemispherical shape and is concentric with the interior housing to form a spherical wall (7) of thickness "E". Note that the interior housing (4) peripherally includes a spherical interior surface (8) and at the bottom, a flat bearing surface (9). Furthermore, the frame (2) comprises a threaded hole (10) of axis X2X2 'corresponding to the general axis of symmetry passing right through the wall at the top (150) of said frame (2). The threaded hole (10) and the bearing surface (9) are intended to receive the impacting tool necessary for the installation of the frame.

 Furthermore, the spherical wall (7) comprises a set of fixing holes (lia, ilb, lic, iîd, île, 11f, Ilg, 11h, iii, Ilj, 11k, 111, llm, lin). Each of the holes is constituted by a cylindrical part (12) and on the side of the internal housing (4), by an enlarged part with spherical bearing (13) intended to receive screws for fixing the prosthesis in the hip bone. The spherical part (13) of the fixing holes comprises a spherical bearing surface (14) on which the fixing screw bears. The fixing holes are for example distributed over three circular rows (R1, R2, R3), parallel at the equatorial edge (15). Thus on the lower row or first row (R1) are distributed five fixing holes (lof, 111, lid, lin, 11h), while on the second row or intermediate row (R2) are distributed four holes (him, lia , lic, 11j). The third row or upper row (R3) includes for example five holes cule, 11h, lib, film, zig).

 According to a particular arrangement and as for the previous frame, its equatorial edge (15) comprises a succession of indexing notches (16) distributed regularly, intended to receive at least one indexing projection (17) produced on the insert (3). Thus, as shown by way of example, the lower surface (151) comprises twelve notches (16a, 16b, 16c, 16d, 16e, 16f, 16g, 16h, 16i, 16j, 16k, 161) of rectangular shape. The lower part of the interior surface (8) comprises two portions of cylindrical surfaces (18, 19) separated by a circular hollow profile (20). Note also that the interior housing (4) includes an inlet chamfer (21).

 The outer surface (6) of the frame as well as the embedding fins is advantageously covered with a first thin layer of porous titanium and with a second outer layer of hydroxyapatite which, by its osteoconduction properties, allows the biological fusion between the bone and the implant and thus ensures a biological fixation in addition to the possible mechanical fixation. The hydroxyapatite coating is done using a vacuum plasma torch.

 Of course, the invention is not limited to the embodiments described and shown by way of examples, but it also includes all the technical equivalents and their combinations.

Claims (15)

 1. acetabular prosthesis (1) comprising a frame (2) of hemispherical shape intended to be implanted in the acetabular cavity, and an insert (3) intended to take place in its interior housing (4) and to receive the femoral head a femoral prosthesis, characterized in that the external surface (6) of said frame comprises at least one embedding fin (22, 23) constituted by a embedding wall (24) which projects relative to the external surface ( 6) of said frame (2).  2. acetabular prosthesis according to claim 1, characterized in that the embedding wall (24) is arranged in a diametral plane (P22, P23).  3. acetabular prosthesis according to claim 2, characterized in that the embedding wall (24) has a variable height "h".  4. acetabular prosthesis according to claim 3, characterized in that the height "h" of the embedding wall (24) increases from bottom to top to be less high near the equatorial edge (15) and to increase towards the top (150).  5. acetabular prosthesis according to any one of claims 2 to 4, characterized in that the upper edge (240) of the wall is curved.  6. acetabular prosthesis according to any one of claims 2 to 4, characterized in that the upper edge (240) of the wall is constituted by two rectilinear edges (240a, 240b) converging.  7. acetabular prosthesis according to any one of the preceding claims, characterized in that the embedding wall (24) comprises at least one hole (25).  8. acetabular prosthesis according to any one of the preceding claims, characterized in that the frame (2) comprises at least two embedding fins (22, 23) arranged in two diametrical planes (P22, P23) concurrent.  9. acetabular prosthesis according to any one of the preceding claims, characterized in that the spherical wall (7) of the frame comprises fixing holes (11) intended to receive the fixing screw or screws of the frame.  10. Cotyloid prosthesis according to claim 8, characterized in that the spherical wall (7) of the frame (2) comprises several fixing holes (11) located at the level of the embedding fins (22, 23).  11. acetabular prosthesis according to claim 10, characterized in that four fixing holes (lia, Ilb, lic, 11d) are arranged between the two fins (22, 23), while at least two other holes (lie, 11f ilg, 11h) are located on the other side of each fin.  12. Cotyloid prosthesis according to any one of the preceding claims, characterized in that the equatorial edge (15) of the frame (2) comprises at least one indexing notch (16) for the insert (3).  13. acetabular prosthesis according to claim 12, characterized in that the frame (2) comprises a succession of indexing notches (16) distributed on the underside of the equatorial edge.  14. acetabular prosthesis according to any one of the preceding claims, characterized in that the top (150) of the wall (7) of the frame (2) comprises a threaded hole (10) and its internal surface (8), a flat bearing surface (9).  15. acetabular prosthesis according to any one of the preceding claims, characterized in that the insert (3) of spherical shape complementary to the frame (2) comprises an indexing projection (3) intended to cooperate with one indexing notches (16) of said frame (2) and comprises an internal cavity (26) hemispherical open downwards.