WO2004045469A1

WO2004045469A1 - Hip prosthesis

Info

Publication number: WO2004045469A1
Application number: PCT/FR2003/003330
Authority: WO
Inventors: Jean-Yves Arlaud; Didier Merckx; Christophe Cermolacce; Didier Prost; Philippe Tisserand; Gérard de Matteis
Original assignee: Euros S.A.
Priority date: 2002-11-13
Filing date: 2003-11-07
Publication date: 2004-06-03
Also published as: FR2846874A1; FR2846874B1; AU2003294046A1

Abstract

The invention concerns a prosthesis (1) comprising a body (2) extending mainly along a vertical axis (3), whereof the shape is formed by a stack of horizontal sections (11), and including, on its outer surface (5), a shoulder (9) whereof the base (10) is adapted to be arranged at the lesser trochanter when the prosthesis (1) is implanted in the femur. The invention is characterized in that horizontal sections (11) mutually offset by translation in the forward and saggital directions so as to form, additionally to the two support points formed by the shoulder (9) and by the part (12) of the inner surface (4) located at the level of the shoulder (9), a rear bulge (12) adapted to be located beneath the lesser trochanter when the prosthesis (1) is set in the femur and forming a third support point.

Description

HIP PROSTHESIS

The present invention relates to a hip prosthesis intended to replace the hip joint.

There is known a hip prosthesis of the type whose prosthesis body extends mainly along a vertical axis, the shape of which consists of a stack of horizontal sections, and comprises, on its external face, a shoulder whose base is adapted to be placed at the level of the lesser trochanter when the prosthesis is placed in the femur.

A prosthesis of this type is for example described in patent application EP 128 036. In this application, the prosthesis includes a twist around the vertical axis. The conformation of this prosthesis allows better fixation in the femoral barrel.

However, the shape of the prosthesis body is not perfectly suited to the barrel of the femur, which can lead to poor distribution of stresses.

This poor distribution of stresses can generate pain.

The object of the present invention is to produce a hip prosthesis shaped so as to have an optimum setting of the prosthesis in the femoral barrel and a maximum bearing surface so as to have a very good transmission of the forces from the prosthesis to the femur.

In the remainder of the application, the term “front face” is understood to mean the face of the prosthesis facing the front of the patient when it is implanted in the femur. The same is true of the rear, external and internal faces. According to the invention, horizontal sections are offset from each other by translation in the frontal and sagittal directions so as to form, in addition to the two support points constituted by the external shoulder and by the part of the internal face. being substantially at the height of the external shoulder, a third fulcrum located on the rear face of the prosthesis and constituted by a posterior bulge adapted to be situated under the small trochanter when the prosthesis is placed in the femur.

The two conventional support points, which are, on the one hand, the external shoulder located on the external face, and, on the other hand, the part of the internal face being substantially at the height of the external shoulder , are supplemented by a third support point constituted by the posterior bulge located on the rear face of the prosthesis. The three support points of the prosthesis according to the present invention allow the improvement of the transmission of forces from the prosthesis to the femur.

Other advantages and features of the present invention will become apparent from the description which follows. In the appended drawings given by way of nonlimiting examples:

- Figure 1 is a perspective view in the frontal plane of the front face of a prosthesis according to the present invention; - Figure 2 is a perspective view in the sagittal plane of the internal face of a prosthesis according to the present invention; - Figure 3 is a perspective view in the sagittal plane of the external face of a prosthesis according to the present invention;

Figure 4 is a perspective bottom view of a prosthesis according to the present invention;

- Figures 5 to 10 are sectional views of the prosthesis along lines VV, VI-VI, VII-VII, VIII-VIII, IX-IX and XX of Figure 1. A hip prosthesis 1 used without cement, comprises a prosthesis body 2 which extends mainly along a vertical axis 3 and which comprises an internal face 4, an external face 5, a front face 6 and a rear face 7, and a neck 8 which forms a close angle 45 ° with the vertical axis 3 and which is located in the extension of the internal face 4.

The body 2 comprises, on its external face 5, a shoulder 9, the base 10 of which is adapted to be placed at the level of the lesser trochanter when the prosthesis 1 is placed in the femur. This shoulder 9 constitutes a first fulcrum of the prosthesis 1 in the femur.

The body 2 comprises a second fulcrum 46 constituted by the part 46 of the internal face 4 which is located substantially at the height of the external shoulder 9.

In the present application, the upper zone 44 of the body 2 can be defined as being the zone from which the external face 5 curves in the direction of the neck 8, the lower zone 45 can be defined as being the zone in which the horizontal sections 11 are circular, even substantially circular, and the middle zone 41 is defined as being situated between the lower zone 45 and the upper zone 44.

The body 2 of the prosthesis 1 can be considered as a stack of horizontal sections 11. According to the invention, at least the horizontal sections 11 stacked in the middle zone 41 are offset with respect to each other by translation in the frontal directions and sagittal so as to form, in addition to the two support points mentioned above (9,46), a third support point which is located on the rear face 7 and which is constituted by a posterior bulge 12 adapted to be located under the small trochanter when prosthesis 1 is placed in the femur.

More precisely, in the direction of the tail 13 of the prosthesis 1 towards the neck 8, the horizontal sections 11 are translated backwards in the lower part 42 of the middle zone 41, and forwards in the upper part 43 of the median zone 41, so as to form the posterior bulge 12.

Each horizontal section 11 comprises an internal end 14 and an external end 15. The body 2 of the prosthesis 1 comprises an internal curve 16 and an external curve 17 defined as being the stacking of the internal 14 and external 15 ends of each horizontal section 11 .

In a known manner, and as can be seen in FIG. 1, the projection 18 of the internal curve 16 in the frontal plane can be defined as follows: in the lower zone 45, the projection 18 is very slightly curved towards the neck 8 and makes an angle less than 5 ° with the vertical axis 3; beyond, the angle between the projection 18 and the vertical axis 3 increases continuously until it reaches a value close to 30 °.

Similarly, in known manner and as can be seen in FIG. 1, the projection 19 of the external curve 17 in the frontal plane can be defined as follows: in the lower zone 45, the projection 19 is curved in the direction opposite to the neck 8 and makes an angle with the vertical axis 3 close to 5 °, in the middle zone 41, the angle increases until it reaches approximately 15 °, then decreases and, in the upper zone 44, the decrease is such that the projection 19 curves towards the neck 8 until it reaches, at the upper end of the body 2, a value close to 60 °. Thus, the projection 19 comprises an extremum El directed towards the external face 5 corresponding to the external shoulder 9.

As can be seen in FIG. 2, the projection 20 of the internal curve 16 in the sagittal plane has, in the median zone 41, an extremum E2 oriented towards the rear face 7 of the prosthesis 1 and corresponding to the posterior bulge 12. Likewise, and as can be seen in FIG. 3, the projection 21 of the external curve 17 in the sagittal plane has, in the median zone 41, an extremum E3 oriented towards the rear face 7 of the prosthesis 1 and corresponding to the posterior bulge 12.

These two projections 20, 21 in the sagittal plane are similar and can be defined as follows: in the lower zone 45, the projections 20, 21 are in the direction of the vertical axis 3; in the lower part 42 of the middle zone 41, the projections curve towards the rear face 7 then, in the upper part 43 of the central zone 41, towards the front face 8, the deportation of the extremums E2 and E3 of the projections 20,21 behind the vertical axis 3 being a few millimeters, preferably 3 mm.

As can be seen in FIG. 4, the projection 22 of the internal curve 16 in the horizontal plane has an extremum E4 which is oriented towards the rear face 7 of the prosthesis 1 and which corresponds to the posterior bulge 12. Furthermore, the projection 23 of the external curve 17 in the horizontal plane has an extremum E5 which is oriented towards the rear face 7 of the prosthesis 1 and which corresponds to the posterior bulge 12, as well as an extremum E6 which is oriented towards the external face 5 of prosthesis 1 and which corresponds to the external shoulder 9.

Figures 5 to 10 show the shape of the horizontal sections 11 along the vertical axis 3. It can be noted that the horizontal section 11 is circular on the lower region 45 of the tail 13 (Figure 10), and at beyond, the horizontal section 11 stretches in the so-called longitudinal direction (Figures 5 to 9). It can be noted that each horizontal section 11 in the middle zone 41 has a symmetry with respect to the longitudinal segment 24 which is defined as passing through the internal end 14 and the external end 15 of the corresponding horizontal section 11. The angle 40 formed by the projection, in the horizontal plane, of the neck 8 and by the longitudinal segment 24 of a horizontal section 11 is the even, whatever the horizontal section 11. This angle 40 therefore defines the angular offset between the neck 8 and the body 2. In the example illustrated in FIGS. 1 to 10, the neck is retroverted by 10 °, which makes it possible to catch the anteversion of the proximal section of the prosthesis, adapted to the last section of the neck of the femur.

Furthermore, each horizontal section 11 comprises an internal arc 25, an external arc 26, a front arc 27 and a rear arc 28, the stacking of each of these arcs 25,26,27,28 defining the internal 4, external faces 5, front 6 and rear 7 of the body 2 of the prosthesis 1.

Due to the symmetry of each horizontal section 11 in the middle zone 21, with respect to the longitudinal segment 24, the radius of curvature R _av of the front arc 27 is equal to the radius of curvature R _ar of the rear arc 28.

For each horizontal section 11 in the middle zone 41, the radius of curvature R _ar of the rear arc 28 (and that R _av of the front arc 27) is greater than the radius of curvature R _ex t of the external arc 26 and to the radius of curvature Ri _nt of the internal arc 25. In addition, the radius of curvature R _ex t of the external arc 26 is greater than that of the internal arc Rnt-

For example, in the zone adjacent to the posterior bulge 12, the ratio of the radius of curvature R _ar of the rear arch 28 to the radius of curvature R _ex t of the external arch 26 is between 4.5 and 11, and the ratio of the radius of curvature R _ex t of the external arc 26 to the radius of curvature R _nt of the internal arc 25 is between 1.3 and 2. For example, in the example illustrated in Figures 1 to 10, we have the following radii for the different sections:

- Figure 5 (upper area 44): R _ar = 75 mm, R _ext = 11.75 mm and R _{± nt} = 5.6 mm; FIG. 6 (upper part 43 of the central zone 41): R _ar = 77.13 mm, R _ex t = H πun and Rι _nt = 5.6 mm; Figure 7 (upper part 43 of the central area 41): R _ar = 50 mm, R _ex t = 10.25 mm and Rι _nt = 5.6 mm; Figure 8 (lower part 42 of the middle zone 41): R _ar = 28 mm, R _ext = 6.2 mm and Ri _nt = 4 mm; Figure 9 (lower part 42 of the middle zone 41): R _ar = 11 mm, R _ex t = 4.6 mm and Ri _{nt 4.2} mm; and

- Figure 10 (lower area 45): R _ar = 4.4 mm, Re _X = 4.4 mm and Rι _nt = 4.4 mm.

It can be noted that, the more proximal a horizontal section 11, the greater the radius of curvature Rext of the external arc 26.

Each horizontal section 11 is thus formed by the junction of the internal arc 25, the external arc 26, the front arc 27 and the rear arc 28, each arc being joined tangentially to the two neighboring arcs. In this way, no horizontal section has any angular point.

Each horizontal section 11 comprises a rear end 29 which is situated at the junction of the external arc 26 with the rear arc 28. The normal projection of the front end 29 on the segment longitudinal 24 is in the third of this segment 24 near the outer end 15.

The projection 30 in the sagittal plane of the rear curve 31 (which is defined as being the stacking of the rear ends 29 of each horizontal section 11), has, in the upper part 43 of the middle zone 41, an extremum E7 which is oriented towards the rear face 7 of the prosthesis 1 and which corresponds to the front limit of the posterior bulge 12. It is thus possible to define the thickness of the posterior bulge 12 and therefore the quality of the bearing surface of this third point d 'support.

As can be seen in FIGS. 2 and 3, the rearward deviation of the rear curve 31, in the lower part 42 of the middle zone 41, caused by the translation of the horizontal sections 11 towards the rear (as for the internal and external curves 16) is amplified by the increase in the radii of curvature R _ext of the external arcs 26. The deportation of the extremum E7 from the rear curve 31 behind the vertical axis 3 is between 10 and 13 mm.

It is therefore possible to play on the two parameters (translation of the horizontal section and radius of curvature of the external arch) to determine the dimension of the posterior bulge 12 as well as the profile of the part of the rod introduced into the femoral barrel.

Obviously the present invention is not limited to the embodiment described in relation to the appended drawings, numerous modifications can be made to it.

Claims

1. Hip prosthesis (1) comprising a prosthesis body (2) which extends mainly along a vertical axis (3), the shape of which consists of a stack of horizontal sections (11), and which comprises, on its external face (5), a shoulder (9) whose base (10) is adapted to be placed at the level of the lesser trochanter when the prosthesis (1) is placed in the femur, characterized in that horizontal sections (11) are offset relative to each other by translation in the frontal and sagittal directions so as to form, in addition to the two support points constituted by the external shoulder (9) and by the part (46) of the internal face (4 ) being substantially at the height of the external shoulder (9), a third fulcrum (12) located on the rear face (7) of the prosthesis (1) and constituted by a posterior bulge (12) adapted to be located under the small trochanter when the prosthesis (1) is placed in the femur.

2. hip prosthesis (1) according to claim 1, characterized in that, in the direction of the tail (13) of the prosthesis towards the neck (8), the horizontal sections (11) are translated backwards in the lower part (42) of the central region (41), and towards the front in the upper part (43) of the central region (41), so as to form the posterior bulge (12).

3. hip prosthesis (1) according to claim 1 or 2, characterized in that the projection (20), in the sagittal plane, of the curve internal (16) defined by the set of internal ends (14) of the horizontal sections (11), has, in the middle zone (41), an extremum (E2) oriented towards the rear face (7) of the prosthesis (1 ) and corresponding to the posterior bulge (12).

4. Hip prosthesis (1) according to one of claims 1 to 3, characterized in that the projection (21), in the sagittal plane, of the external curve (17) defined by all of the external ends (15 ) horizontal sections (11), has, in the middle region (41), an extremum (E3) oriented towards the rear face (7) of the prosthesis (1) and corresponding to the posterior bulge (12).

5. Hip prosthesis (1) according to one of claims 1 to 4, characterized in that the projection (22), in the horizontal plane, of the internal curve (16) defined by all of the internal ends (14 ) horizontal sections (11), has an extremum (E4) oriented towards the rear face (7) of the prosthesis (1) and corresponding to the posterior bulge (12).

6. Hip prosthesis (1) according to one of claims 1 to 5, characterized in that the projection (23), in the horizontal plane, of the external curve (17) defined by all of the external ends (15 ) horizontal sections (11), has an extremum (E5) oriented towards the rear face (7) of the prosthesis (1) corresponding to the posterior bulge (12), and an extremum (E6) oriented towards the external face (5) of the prosthesis (1) and corresponding to one external shoulder (9).

7. hip prosthesis (1) according to one of claims 1 to 6, characterized in that each horizontal section (11) has a symmetry with respect to the longitudinal segment (24) passing through the internal end (14) and l external end (15) of the corresponding horizontal section (11).

8. hip prosthesis (1) according to claim 7, characterized in that the angle (40) formed by the projection in the horizontal plane of the neck (8) of prosthesis and the longitudinal segment (24) of a horizontal section (11) is the same for each horizontal section (11) of the prosthesis (1).

9. hip prosthesis (1) according to claim 8, characterized in that the angle (40) formed by the projection in the horizontal plane of the neck (8) of prosthesis and the longitudinal segment (24) of a horizontal section (11) is a 10 ° retroversion.

10. Hip prosthesis (1) according to one of claims 1 to 9, characterized in that, in the middle zone (41), each horizontal section (11) comprises an internal arc (25), an external arc (26 ) whose radius of curvature (R _ex t) is greater than that (Rint) of the internal arc (25), a front arc (27) whose radius of curvature (R _av ) is greater than that (R _ext ) of the external arc (26), and a rear arc (28) whose radius of curvature (R _ar ) is equal to that (R _av ) of the front arc (27), each arc (25,26,27 , 28) being joined to the two neighboring arcs in a tangent way.

11. Hip prosthesis (1) according to claim 10, characterized in that the rear end (29) of each horizontal section (11), located at the junction of the external arch (26) with the rear arch (28), is located, in the longitudinal direction, in the third close to the external end (15).

12. hip prosthesis (1) according to claim 10 or 11, characterized in that, in the area adjacent to the posterior bulge (12), the ratio of the radius of curvature (R _ar ) of the rear arch (28) on the radius of curvature (R _ex t) of the external arc (26) is between 4.5 and 11, and the ratio of the radius of curvature (R _GX t) of the external arc (26) to the radius of curvature (Rint) of the internal arc (25) is between 1.3 and 2.