FR2936145A1 - Artificial cotyle for hip joint prosthesis, has circular groove internally provided with dents, where circular groove is arranged above truncated portion of cup along polar direction, on curved zone of hemispherical cavity - Google Patents

Abstract

The cotyle (1) has an articular core (100) indistinctly made by plastic i.e. polyethylene, composite or ceramic material. A cup (10) has a truncated portion shrunken towards a pole (14) for blocking the core in translation. A circular groove (24) is internally provided with dents that are radially projected towards an interior of a hemispherical cavity (20) for blocking the core in axial rotation. The groove is arranged above the truncated portion of the cup along a polar direction, on a curved zone (26) of the cavity.

Description

The present invention relates to a hip joint prosthesis acetabulum for impacting the acetabulum of the patient's pelvic bone. A hip prosthesis comprises in known manner two articulated parts, respectively an anchor rod intended to be introduced into the femoral shaft to be sealed either naturally by osseointegration or artificially by means of cement, and a spherical joint head which is intended to replace the natural femoral head to be received in the acetabular cavity of the patient's corresponding pelvic bone. This head is either impacted by force and possibly held by screws, or glued with a suitable cement. The articular head can be performed in two different ways depending on the type of pathology encountered. Thus, when the acetabular cavity is not too damaged, it is possible to use a single joint head integral with the anchor rod at a neck provided for this purpose, the artificial head replacing then simply to the natural head. But when the acetabular cavity is too damaged to continue to fulfill its function of sliding support with the femoral head, it is necessary to use a joint head intrinsically making a ball joint. This second type of articular prosthesis conventionally comprises an artificial acetabulum firstly fixed permanently in the acetabulum, and a spherical part (or ball joint) integral with the anchor rod and received in a corresponding hemispherical housing of the acetabulum for producing a patella link replacing the natural initial bond. An acetabulum generally comprises a so-called support cup, made of a biocompatible metal such as titanium or a titanium alloy, and a core, or insert, intended to be placed tightly in a hemispherical cavity of the cup. The inner cavity of the core, also of hemispherical shape, is intended to receive the spherical head of the femoral stem of the prosthesis to form the sliding ball joint described above. Of course, the core is fixed in the cup and can, under certain conditions, be extracted. The core can be made of plastic, composite or ceramic material. Depending on the material chosen, different types of fixing and locking means in axial rotation, axial translation and transverse tilting are provided. Thus, patent FR-A-2 681 238 provides, for fixing the plastic core on the metal cup, notches regularly arranged on the outer face of said core and an annular groove secant said notches and receiving a clip, said cooperating assembly with bosses machined on the outer surface of the cup. In FR-A-2 781 362, FR-A-2 781 263 and EP-A-974 316, the locking means between the metal cup and the polyethylene core are constituted by anchoring claws arranged on the inner surface of the cup, near its equatorial edge, and coming to bite in an annular anchoring portion of the core. Patent FR-A-2,708,459 describes the use of corrugated circumferential grooves for fixing a polyethylene insert inside the hemispherical cavity of a metal cup. Finally, FR-A-2,686,791 describes a solution for fixing a polyethylene core in a metal cup using notches and teeth collaborating with each other.

However, these devices are not entirely satisfactory because the attachment is not optimized and the risk of movement of the core inside the cup are still too important. However, these movements can cause complications for the patient that can go to the removal / replacement of the prosthesis if it has moved beyond the acceptable limits. Moreover, these fastening techniques conceal only polyethylene cores and not metal. A solution has also been proposed in EP-A-1 395 206 to be able to fix both ceramic plastic cores in a metal cup. This solution involves both a collaboration between a frustoconical outer surface 3 of the core and a frustoconical surface of the cavity of the cup, in the case where the core is ceramic, and an annular groove formed in the cavity of the cup provided with a protruding protrusion in the form of cusps that can sink into the core, in the case where the latter is plastic .. However, again, the attachment is: not optimized knowing that it takes a blocking in both axial rotation, axial translation and orthogonal tilting. An object of the present invention is therefore to solve the problems mentioned above by means of a solution that is simple to implement, reliable and inexpensive. Thus, the present invention relates to an acetabulum for a hip prosthesis to be impacted in the acetabulum of the patient's pelvic bone, comprising: a hollow hemispherical cup having an external surface, a pole, a equatorial rim and a hemispherical cavity, and - an articular core indistinctly made of plastic material such as polyethylene, composite or ceramic, said core being adapted to be housed in the hemispherical cavity and having a hemispherical inner housing for receiving a ball joint femoral stem, the cavity of the cup being provided with means for locking the core in axial translation, in axial rotation and preventing its orthogonal tilting, said means having, from the equatorial flange: a frustoconical section in one or more parts narrowing towards the pole of the cup to block the translational core, 30 - a circular groove provided locally internally with teeth projecting radially inwardly of the cavity for locking said insert at least in axial rotation, characterized in that the groove is located beyond the frustoconical section of the cup in a polar direction on a curved area of the cavity.

According to preferred embodiments, the cup according to the present invention further comprises at least one of the following features: the teeth are arranged in pairs whose respective sharp peaks are circumferentially oriented in opposite directions so as to block the rotation axial of the core by permanent local deformation of the material constituting the latter; the respective sharp peaks of the teeth are circumferentially oriented in opposite directions to block the axial rotation of the core in the clockwise and counterclockwise directions; the cavity comprises eight pairs of teeth distributed equidistantly around the circumference of the groove; - The groove has a circular recess groove deeper than the rest of the groove and adapted to receive a radially outer prominent bead of the core including locking the latter in axial translation; - the groove is located between the frustoconical section and the teeth; - the groove has, on the side of the pole of the cup, a circular radial shoulder defining a locking flange pivoting the core; - The frustoconical section is at an angle of the order of 15 ° to 20 °, preferably about 18 °; it is provided, at its bottom, beyond the groove, with through-holes intended to house each a screw head for fixing the cup in the bone tissue of the pelvic bone; it is made of a hard biocompatible material such as titanium or a titanium alloy; and the core comprises a peripheral flange extending by a radial skirt forming a seat intended to rest on the equatorial rim of the cup to prevent the orthogonal tilting of the core. The invention also relates to a hip joint prosthesis comprising an acetabulum according to any one of the preceding claims for receiving an artificial head of femur to form a ball joint.

Advantageously, the insert has a radially prominent outer bead intended to cooperate with a groove of the groove of the cup. Preferably, the insert comprises a peripheral rim extending by a skirt forming a seat intended to rest on the edge of the cup to block the orthogonal tilting of the insert. The invention will now be described in more detail with reference to particular embodiments given by way of illustration only and represented in the appended figures in which: FIG. 1 represents an acetabulum according to the present invention comprising an external cupule and an inner core - Figure 2 is a sectional view of Figure 1; - Figure 3 is a detail view of Figures 1 and 2; - Figure 4 is a sectional view of: The cup; Figure 5 is a perspective view of the interior of a cup half; Figure 6 is a detail view of Figure 5; - Figure 7 is a top view of the interior of the cup; Figure 8 is a detail view of Figure 7; Figure 9 is a side view of a half cup; and FIG. 10 is a detailed view of FIG. 9. An artificial acetabulum 1 for a hip prosthesis is represented globally in FIGS. 1 and 2. This acetabulum 1 is adapted to be impacted and fixed permanently in the cavity. cotyloid (not shown) of the patient, for example in a known manner using screws. The acetabulum 1 is made of a biocompatible metal, such as titanium or a titanium alloy, and has an outer cup 10 of hemispherical shape with an outer surface 12 intended to fit the acetabular cavity, a pole 14, an equatorial rim 16 and an internal cavity of substantially hemispherical shape 20.

The acetabulum 1 also comprises a joint core 100, or insert, intended to be precisely placed and held in place in the cavity 20 of the cup 10. The core 100 is made indistinctly of plastic material such as polyethylene, composite or ceramic, which provides a clear advantage to the solution of the present invention over the cups of the prior art. The core 100 further includes a hemispherical inner housing 110 for housing an artificial head femoral stem (not shown) to form a ball joint with the iliac bone (not shown). The cup 10 comprises, at its cavity 20, a frustoconical portion 22 which begins at the equatorial flange 16 and is directed towards the pole 14 narrowing. The frustoconical section 22 makes an angle of the order of 15 ° to 20 °, preferably about 18 ° with the axis XX ', and allows a first locking in translation and axial rotation of the core 100, especially when the latter is in contact. ceramic. A circular groove 24 is formed in the hemispherical cavity 20 of the cup 10, beyond the frustoconical section 22 in a polar direction, on a curved zone 26. This groove 24 is internally provided with eight pairs of teeth 28 making protrusion inwardly of the cavity 20. More precisely, as can be seen in FIGS. 6 and 8 respectively showing detail views of FIGS. 5 and 7, the teeth 28 of each pair 30 exceed from a few hundredths to a few tenths millimeters inwardly of the cavity 20 and are circumferentially oriented in opposite directions. As shown in FIG. 3 illustrating a common detail of FIGS. 1 and 2, the peaks 30 of the teeth 28 are adapted to penetrate into the core 100 by locally and permanently deforming the material which constitutes it in order to block in axial rotation in the clockwise and counterclockwise relation to the cup 10. The pairs of teeth 28 are equidistantly distributed over the circumference of the groove 24 to distribute the force which holds the core 100 in the cup 10 and better resist the movements of the femoral head.

With regard to the locking in axial translation of the core 100 relative to the cup 10, that is to say along the axis XX 'of the cup or of the core + cupule assembly, the annular groove 24 comprises a circular clearance groove 32 deeper than the crown area where the teeth 28 are located so as to receive an external bead 102 projecting radially from the core 100. The groove 32 is disposed between the frustoconical section 22 and the teeth 28 of the cup 10. By penetrating axially into the groove 32, the radial bead 102 is housed in the latter to maintain the core 100 in the cup 10 during traction movements exerted by the femoral head (see Figure 10 in particular) . As can be seen in FIGS. 3 and 10, the groove 24 furthermore has a circumferential radial shoulder 34 which serves as a stop for an outer rim 104 of the core (see also FIG. 2).

This shoulder 34 thus cooperates with the flange 104 to prevent tilting of the core 100 relative to the cup 10 along any axis perpendicular to the axis XX '. The core 100 has meanwhile a peripheral flange 106 extending by a radial skirt 108 forming a seat intended to rest on the equatorial flange 16 of the cup 10 to also prevent the orthogonal tilting of the core: L00. As shown in FIGS. 5, 7 and 9, the cup 10 is provided, at its bottom, beyond the groove 24, with through orifices 40 each intended to house a fixing screw head (no shown) of the cup in the bone tissue of the iliac bone Thus, once the nucleus is forced into the cup, it is perfectly blocked and can not turn on itself, rotate or be removed. axially. This ensures that the artificial head of the femur is properly connected to the patient's iliac bone to form a functional ball joint. It goes without saying that the detailed description of the object of the invention, given solely by way of illustration, does not in any way constitute a limitation, the technical equivalents also being included in the scope of the present invention.

Thus, the shape, distribution and number of pairs of teeth may vary depending on the type of core.

Claims (11)

REVENDICATIONS1. Cotyle (1) for hip joint prosthesis to be impacted in the acetabulum of the patient's bone, comprising: - a hollow hemispherical cup (10) having an outer surface (12), a pole ( 14), an equatorial flange (16) and a hemispherical cavity (20), and - an articular core (100) indistinctly made of plastic such as polyethylene, composite or ceramic, said core (100) being adapted to being housed in the hemispherical cavity (20) and having a hemispherical inner housing (110) for receiving a femoral stem ball, the cavity (20) of the cup (10) being provided with means for locking the core in axial translation, in axial rotation and preventing its orthogonal tilting, said means having, from the equatorial flange (16). - a frustoconical section (22) in one or more parts narrowing towards the pole (14) of the cup (10) to block the core (100) in translation, - a circular groove (24) internally provided locally with teeth (28) protruding radially inwardly of the cavity (20) for locking said core (100) at least in axial rotation, characterized in that the groove (24) is located beyond the frusto-conical section ( 22) of the cup (10) in a polar direction on a curved area (26) of the cavity (20). 2. Cotyle (1) according to claim 1, characterized in that the teeth (28) are arranged in pairs (3) whose respective sharp peaks are circumferentially oriented in opposite directions so as to block the axial rotation of the core ( 100) by permanent local deformation of the material constituting the latter. 3. Cotyle (1) according to claim 2, characterized in that the respective sharp peaks of the teeth (28) of the same pair (30) 35 are oriented circumferentially in opposite directions to block the axial rotation of the core clockwise and counterclockwise. 4. Cotyle (1) according to claim 2 or 3, characterized in that the cavity comprises eight pairs (30) of teeth (28) distributed equidistantly on the circumference of: The groove (24). 5. Cup (1) according to any one of the preceding claims, characterized in that the groove (24) has a circular clearance groove (32) deeper than the rest of the groove and adapted to receive an outer bead (102). ) radially prominent core (100) allowing in particular to block the latter in axial translation. 6. Cotyle (1) according to any one of the preceding claims, characterized in that the groove (32) is located between the frustoconical section (22) and the teeth (28). 7. cup (1) according to any one of the preceding claims, characterized in that the groove (24) has, on the side of the pole (16) of the cup (10), a radial radial shoulder (34) defining a cooperating with a flange (104) of the core (100) to block the latter in tilting. 8. Cotyle (1) according to any one of the preceding claims, characterized in that the frustoconical section (22) makes an angle of the order of 15 ° to 20 °, preferably about 18 °. 9. Cotyle (1) according to any one of the preceding claims, characterized in that it is provided at its bottom, beyond the groove (24), through orifices (40) for housing each a screw head for fixing the cup (10) in the bone tissue of the pelvic bone. 10. Cotyle (1) according to any one of the preceding claims, characterized in that the cup (10) is made of hard biocompatible material such as titanium or a titanium alloy. 11. Cotyle (1) according to any one of the preceding claims, characterized in that the core (100) comprises a peripheral flange (106) extending by a radial skirt (108) forming a seat intended to rest on the equatorial rim (16) of the cup (10) to prevent orthogonal tilting of the core (100). Joint hip prosthesis comprising an acetabulum (1) according to any one of the preceding claims for receiving an artificial head of femur to form a ball joint.