FR2595241A1 - Hip prosthesis - Google Patents

Abstract

This prosthesis is of the type comprising a femoral element consisting of a tail and a spherical head, and an acetabular element consisting of a cup and a support ring comprising a collar of generally circular shape curved according to the external profile of the cup. According to the invention, the support ring 5 comprises, projecting from its periphery, at least one upper plate 15 including fixation orifices 22, and a lower hook 16.

Description

HIP PROSTHESIS
The present invention relates to a hip prosthesis.

 In the event of # deterioration of the head of the femur or the acetabulum, inside which it is mounted, it is now common to resort to the implantation of a prosthesis.

 The implantation of a prosthesis is carried out by sawing the neck of the femur or upper part thereof and by replacing it with a part which comprises a tail intended to be engaged in the medullary canal, terminated by a head of general shape spherical engaged in the acetabulum.

 Depending on the state of this cavity, it may or may not be fitted with a cup of generally hemispherical shape. Such a cup is placed, generally by sealing, inside the cavity, after enlarging the latter by milling.

 However, it appears that the acetabulum constitutes the fragile point of hip prostheses, loosening occurring quite frequently at this level. It is therefore advantageous, even essential in certain cases, to rebuild or simply arm a failing acetabulum.

For this purpose, it is known to have, under the cup, a support ring, fixed by screwing and making it possible to seal said cup properly. A support ring is used to advantage:
- in case of poor bone condition: osteoporosis, cystic cavities, loss of substances
- in case of dysplasia or malformation of the acetabulum, the ring allows, associated or not with bone grafts, to restore correct support to the cup
- in case of acetabular reconstruction with poor bone condition and loss of substances.

 There are several types of support rings allowing reconstructions, but none can be used in all cases.

 A widely used ring includes an upper canopy which requires significant milling of the bone, which is not without risk.

 In addition, this ring is difficult to maintain during screwing, which often results in verticalization of the implant which then leans poorly on the bottom of the acetabulum. In addition, such a ring does not completely avoid the risks of protusion, which involve a new intervention on the patient.

 The present invention aims to remedy these drawbacks.

 To this end, in the hip prosthesis that it relates to, of the type comprising a femoral element constituted by a tail and a spherical head, and an acetabular element constituted by a cup and a support ring comprising a crown of generally curved circular shape according to the outer profile of the cup, the support ring comprises, projecting from its periphery, at least one upper plate having fixing holes, and a lower hook.

 This ring, which does not have an upper canopy, easily penetrates the acetabulum, with or without reconstitution by bone grafts. The upper plate allows, if necessary, a good reconstruction of the upper and anterior part of the acetabulum by a graft, and participates in the fixation of the ring.

 In addition, the lower hook allows a good setting of the ring during the screwing of the latter and plays a role of anti-protusion during period of use of the prosthesis.

 According to another characteristic of the invention, the ring has two lateral ears projecting from its peripheral edge, intended to bear against the acetabulum. These two lateral ears participate in wedging and immobilizing the ring during the screwing phase.

 It should be noted that a ring of determined dimensions can be put in place very simply after more or less significant bending of the upper plate, the lower hook and the lateral ears.

 The simplicity and the good adaptability of the ring, which does not require significant milling prior to its installation, provides a lot of security.

 In addition, it is known that the adaptation of the femoral tail in the medullary canal using a self-locking system allows good holding of the femoral part sometimes making it possible to dispense with cement.

 However, the structure of traditional femoral pieces does not allow a good result to be achieved.

 The present invention therefore also aims to provide a prosthesis ensuring excellent hold of the femoral part.

 To this end, in the prosthesis according to the invention, the upper part of the tail, that is to say that located on the side of the spherical head has a tulip shape corresponding to an increase in section of the tail from the center from the latter towards its end situated on the side of the head, this increase in section resulting both from an increase in thickness and an increase in width of the tail.

 In addition, the upper part of the tail has, seen in cross section, a generally rectangular shape delimited by two plane walls which are substantially parallel, but slightly convergent on the anterior side, connected by two end walls slightly rounded towards the outside.

 Advantageously, the flat walls comprise, # over the entire length of the tail, longitudinal grooves equidistant from each other.

 These characteristics favor the fixation of the tail of the prosthesis in the medullary canal, even in the absence of cement.

 Finally, the upper end of the tail is equipped with a tongue projecting outwards at its front edge.

 This tongue allows good bone support, sometimes requiring a small cut of the Merkel spur, but distributing the pressures better than in the traditional case.

In any case, the invention will be clearly understood with the aid of the description which follows, with reference to the appended schematic drawing, representing, by way of nonlimiting example, an embodiment of this prosthesis:
Figure 1 is a side view and in an exploded position of the components of the prosthesis
Figure 2 is a side view of the femoral part of the prosthesis;
Figure 3 is a front view
Figure 4 is a cross-sectional view along the line IV-IV of Figure 2
Figure 5 is a front view of an iliac bone equipped with a support ring being put in place
Figure 6 is a side view of this support ring after mounting of a cup.

 The prosthesis, shown in the drawing, comprises a femoral part constituted by a tail 2 at the upper end of which is fixed a head 3 of generally spherical shape, and an acetabular part comprising a cup 4 in which is mounted, with possibility of rotation. , the head 3, this cup being itself mounted in the acetabular cavity with the interposition of a support ring 5.

 As shown in Figures 2 to 4, the stem 2 of the prosthesis comprises two planar walls 6 and 7 substantially parallel, connected by two curved walls 8 and 9 facing outwards.

The walls 6 and 7 have longitudinal grooves 10
extending over their entire height.

As can be seen from the drawing, the upper part 2a of the tail is
tulip-shaped, that is to say has an increase in section from the central part of the tail in the direction of the free end thereof. This increase in section results from an increase in width and an increase in thickness, as shown in Figures 2 and 3 respectively.

 In addition, the two plane walls 6 and 7 are not strictly parallel, but converge on the side of the wall 9, that is to say on the side of the anterior edge of the tail of the prosthesis.

 Finally, the upper end of the tail 2 is equipped, at its front edge, with a tongue 12 projecting outwards.

This tongue allows a good bone support distributing the pressures well, its positioning sometimes requiring a small cut of the spur of
Merkel.

 Figures 5 and 6 show the mounting of a cup 4 and a support ring.

 Figure 5 shows an iliac bone 13 in front view. As is apparent from the drawing, the ring 5 comprises a body 14 in the form of a crown of generally circular shape curved according to the external profile of the cup, from the periphery of which project an upper plate 15, a lower hook 16 and two side ears 17.

As shown in Figure 6, the ring 5 is put in place after restoration of the acetabulum using bone grafts 18. The
the ring is fixed by means of screws 19 engaged in orifices 20 formed in the upper plate 15.

 As is clear from the drawing, the upper plate participates in the fixing of the ring while promoting the reconstruction of the acetabulum by grafts 18, the lower hook promotes the setting of the ring and prevents the protusion of the latter in conditions of use, while the lateral ears 17 participate in wedging and immobilizing the ring during the screwing phase.

 It emerges from the above that this prosthesis is simple and safe to use for the practitioner, both at the level of the tail belonging to the femoral part of the prosthesis and at the level of the support ring located in the acetabulum.

 The advantages resulting from the original structure of this prosthesis also translate into excellent solidity and excellent resistance of the latter during use.

 It goes without saying that the invention is not limited to the sole embodiment of this hip prosthesis, described above by way of example; on the contrary, it embraces all of its variant embodiments.

 Thus in particular that the number of grooves formed in the tail of the femoral part or that the number of orifices formed in the support ring could be different without departing from the scope of the invention.

Claims (6)

 1. - Hip prosthesis, of the type comprising a femoral element constituted by a tail (2) and a spherical head (3), and an acetabular element constituted by a cup (4) and a support ring (5) comprising a crown (14) of generally circular shape curved according to the external profile of the cup, characterized in that the support ring (5) comprises, projecting from its periphery, at least one upper plate (15) having fixing holes ( 22) and a lower hook (16).  2. - Prosthesis according to claim I, characterized in that the ring (5) has two lateral ears (17) projecting from its peripheral edge, intended to bear against the acetabulum.  3. - Prosthesis according to any one of claims 1 and 2, characterized in that the upper part (2a) of the tail, that is to say that located on the side of the spherical head (3) has a shape tulip-shaped corresponding to an increase in section of the tail from the center of the latter towards its end situated on the side of the head, this increase in section resulting both from an increase in thickness and an increase in width tail.  4. - Prosthesis according to claim 3, characterized in that the upper part (2a) of the tail has, seen in cross section, a generally rectangular shape delimited by two plane walls (6, 7) substantially parallel, but slightly convergent of the anterior side, connected by two end walls (8, 9) slightly rounded towards the outside.  5. - Prosthesis according to claim 4, characterized in that the flat walls (6, 7) comprise, over the entire length of the tail, longitudinal grooves (10) equidistant from each other.  6. - Prosthesis according to any one of claims 3 to 5, characterized in that the upper end of the tail (2) is equipped with a tongue (12) projecting outwards at its front edge .