EP2004098A2

EP2004098A2 - Implant for resurfacing a femoral head

Info

Publication number: EP2004098A2
Application number: EP07731118A
Authority: EP
Inventors: Michel Timoteo; Tarik Ait Si Selmi; Michel Bonnin
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-03-10
Filing date: 2007-03-09
Publication date: 2008-12-24
Also published as: FR2898267A1; WO2007104852A2; WO2007104852A3; FR2898267B1; AU2007226442A1; US20090306788A1

Abstract

The resurfacing implant according to the present invention is composed of a femoral cap (2) with an outer face (7), an inner face (8), a peripheral edge (11), a central axis XX' passing through the pole P of said cap (2), an equatorial axis YY' perpendicular to the first axis, and a point C of intersection between the main axes XX', YY' forming the centre of the radius of curvature of said outer (7) and inner (8) faces, characterized in that it comprises guide means composed of a cylindrical finger (9) with a base (90) connected to the inner face (8) at a point D, which is offset laterally with respect to the pole P of the hemispherical profile of the femoral cap (2), and stabilizing means (10) arranged on the perimeter of the inner face (8), and having a profile arranged in a plane parallel to that containing the guide means (9).

Description

HEAD RE-SURFACING IMPLANT

femoral

The present invention relates to a re-surfacing implant for repairing the external articular surface of the femoral head.

The surgical technique for repairing the external articular surface of the femoral head called "re-surfacing" is to replace the defective bone cartilage of the femoral head, a metal cap, hemispherical, hollow. This femoral cap is usually associated with an equally hemispherical metallic acetabulum that is impacted in the acetabular cavity of the pelvis.

Note that the current femoral caps have a generally cylindrical internal shape, forcing the surgeon to shape, using cutting tools, the femoral head spherical shape originally, in a cylindrical shape.

This cut of the femoral head can be considered as aggressive and goes against the spirit of this surgical technique which is by definition conservative of the bone capital of the femoral head.

On the other hand, the superior cortex of the femoral neck may be damaged by the cutting tool, which may lead to fracture initiation. Thus, it is found that the femoral head, after being cut by the surgeon in a cylindrical shape, no longer has its hard or cortical bone layer and has a cylindrical stump consisting essentially of spongy bone of low resistance. Also, it is noted that the profile of the hemispherical caps above imposes a unique positioning of said caps around the femoral head. This unique positioning is located on the axis of the femoral neck and may result in the possible tilting of the hemispherical cap by sagging of the bone support.

Under these conditions, there are certain disadvantages with respect to this surgical technique which are mainly due firstly to the disappearance of the bone capital of the femoral head and secondly to the lack of choice of hemispherical cap positioning. function of the morphological state of the proximal end of the femur.

The purpose of the re-surfacing implant according to the present invention is to propose a solution to the problems posed above. The re-surfacing implant according to the present invention consists of a femoral cap having an outer face, an inner face, a peripheral edge, a central axis XX 'passing through the pole P of said cap, an equatorial axis YY' perpendicular to the first and a point C of intersection between the main axes XX ', YY' forming the center of radius of curvature of said outer and inner faces of the guide means which consist of a cylindrical finger having a base coming to connect with the inner face at a point D which is shifted laterally relative to the pole P of the hemispherical profile of the femoral cap and stabilizing means which are arranged on the periphery of the inner face and having a profile which is disposed in a plane parallel to that containing the guide means.

The re-surfacing implant according to the present invention comprises essential features which are described and protected in claims 2-19.

The following description with reference to the accompanying drawings, given by way of non-limiting examples, will provide a better understanding of the invention, the characteristics it has and the advantages that it is likely to provide:

Figures 1 to 5 are views showing a re-surfacing implant according to the present invention.

Figures 6 and 7 are views illustrating a first variant of the guide means and stabilizing means of the re-surfacing implant according to the present invention. Figures 8 and 9 are views showing a second variant of the guide means and stabilizing means of the re-surfacing implant according to the present invention.

Figures 10 and 11 are views showing a third variant of the guide means and stabilizing means of the re-surfacing implant according to the present invention.

Figure 12 is a sectional view illustrating the placement of the resurfacing implant on the femoral head.

FIGS. 1 to 5 show a re-surfacing implant 1 according to the present invention comprising a femoral cap 2 which is intended to be fixed on the femoral head 3 of a femur 4, the external articular surface 5 of which is deteriorated.

The re-surfacing implant 1 consists of a set of femoral caps 2 to be able to adapt to the dimensions of the femoral head 3 to be repaired.

The femoral cap 2 consists of a thin wall 6 of constant thickness in the range having an outer sliding surface 7 with a substantially hemispherical profile and an inner face 8 with a partially hemispherical profile.

The femoral cap 2 has main axes consisting of a central axis XX 'passing through the pole P of said cap 2 and an equatorial axis YY' perpendicular to the first and intersecting the central axis XX 'at a point C forming the center of radius of curvature of the outer faces 7 and inner 8.

The outer sliding surface 7 has a sphericity which extends beyond the equatorial axis YY 'and to the peripheral edge 11 of the femoral cap 2. Also, the outer sliding surface 7 is mirror polished.

On the other hand, the thickness of the wall 6 must not be greater than that of the external articular surface 5 to be restored in order to preserve the maximum bone capital of the femoral head 3 as well as most of its rotundity.

The femoral cap 2 comprises, from its inner face 8, guiding means 9 which consist of a finger 90 with a cylindrical profile, which can be carried by an axis ZZ 'passing through the center C.

The axis ZZ 'of the cylindrical finger 90 can be arranged in a direction inclined at an angle α with respect to the central axis XX' of the femoral cap 2.

The cylindrical finger 90 comprises a base 91 which is connected to the internal face 8 at a point D carried by the axis ZZ 'and which is offset laterally with respect to the pole P of the hemispherical profile of the femoral cap 2.

Also, the length of the cylindrical finger 90 is provided so as not to exceed the peripheral edge 11 of the femoral cap 2 in order to be completely contained within said cap.

For this purpose the free end 92 of the cylindrical finger 90, located opposite the base 91, may be provided to not exceed the point C forming the center of radius of curvature of the outer faces 7 and inner 8 of the femoral cap 2.

The femoral cap 2 comprises stabilizing means 10 which are arranged around the periphery of the inner face 8 and having at least one profile which is arranged in a plane parallel to that containing the guiding means 90. The inner face 8 of the cap Femoral 2 comprises stabilization means 10 which consist of a truncated profile obtained by at least one flat part 100, which is arranged in a plane parallel to that containing the cylindrical finger 90.

The stabilizing means 10 may comprise, in the middle of the flat 100 and in the same plane as that containing the cylindrical finger 90, at least one tapered rib 12 having, for example, a dovetail profile.

According to a preferred mode, but not limiting, the flat 100 comprises a tapered rib 12 which extends from the inner face 8 of the femoral cap 2 and whose length is substantially half that of said flat 100.

The inner face 8 has an inner cylindrical face portion 13 arranged from the peripheral edge 11 of the femoral cap 2 to the level of the equatorial axis YY 'of said femoral cap 2. It can be seen that the wall 6 of the femoral cap 2 increases in thickness at the flat portion 100 formed in the extension of the inner face 8. The inner face 8 is covered over its entire surface with an osteoconductive substrate.

FIGS. 6 to 7 show a first variant of the guide means 9 and the stabilization means 10 of the re-surfacing implant 1 according to the present invention.

The femoral cap 2 of the re-surfacing implant 1 is similar to that described above in FIGS. 1 to 5 and comprises only modifications with regard to the guiding means 9 and the stabilizing means 10.

For this purpose, the femoral cap 2 comprises from its inner face 8 guiding means 9 which consist of a finger 90 cylindrical profile, which can be carried by an axis ZZ 'passing through the center C. L' ZZ 'axis of the cylindrical finger 90 may be arranged in a direction inclined at an angle α with respect to the central axis XX' of the femoral cap 2.

The cylindrical finger 90 comprises a base 91 coming to connect with the inner face 8 at a point D carried by the axis ZZ 'and which is offset laterally with respect to the pole P of the external hemispherical profile of the femoral cap 2.

For this purpose the free end 92 of the cylindrical finger 90, located opposite the base 91, may be provided to not exceed the point C forming the center of radius of curvature of the outer faces 7 and inner 8 of the femoral cap 2. The cylindrical finger 90 has from its free end 92 and towards the inner face 8 of the femoral cap 2 an inclined pan 93 for producing a tapered profile of said cylindrical finger.

The inclined face 93 may be arranged in a plane parallel to that containing the main axis XX 'passing between the point C and the pole P of the femoral cap 2.

The femoral cap 2 comprises stabilizing means 10 which are arranged around the periphery of the inner face 8 and having at least one profile which is arranged in a plane parallel to that containing the guide means 9.

The inner face 8 of the femoral cap 2 comprises stabilization means 10 which consist of a truncated profile obtained by at least one flat part 100, which is arranged in a plane parallel to that containing the cylindrical finger 90. It should be noted in this case that the flat part 100 does not include any means of bone anchoring as described in FIGS. 1 to 5. The internal face 8 has an inner cylindrical face portion 13 arranged from the peripheral edge 11 of the femoral cap 2 until 'at the equatorial axis YY' of said femoral cap 2.

The peripheral edge 11 has, for example, opposite the flat 100 an inclined sector 110 whose lowest part is either on the equatorial axis YY ', or slightly below.

FIGS. 8 to 9 show a second variant of the guide means 9 and the stabilization means 10 of the re-surfacing implant 1 according to the present invention.

For this purpose, the femoral cap 2 comprises from its inner face 8 guide means 9 which consist of a finger 90 cylindrical profile, which can be carried by an axis AA 'laterally offset from the axis XX ', but arranged in a plane parallel to that containing the main axis XX' passing between the point C and the pole P of the femoral cap 2.

The cylindrical finger 90 comprises a base 91 coming to connect with the inner face 8 at a point D carried by the axis AA 'and which is offset laterally with respect to the pole P of the outer hemispherical profile of the femoral cap 2.

Also, the length of the cylindrical finger 90 is provided so as not to exceed the peripheral edge 11 of the femoral cap 2 in order to be completely contained within said cap. For this purpose, the free end 92 of the cylindrical finger 90, located opposite the base 91, may be located between the peripheral edge 11 of the femoral cap 2 and the equatorial axis YY '.

The cylindrical finger 90 is pierced with at least one through hole 94 passing right through the thickness of said finger to form a zone facilitating bone rehabilitation.

By way of example, the through holes 94 are on the one hand carried by the axis AA 'and on the other hand formed between the equatorial axis YY' and the internal face 8 of the femoral cap 2.

The femoral cap 2 comprises stabilizing means 10 which are arranged around the periphery of the inner face 8 so that the means of 21

9 and the stabilization means 10 are arranged on each side of the main axis XX 'of the femoral cap 2.

The stabilizing means 10 consist of at least one fin 101 extending from the inner face 8 and towards the main axis XX 'of the femoral cap 2.

Each fin 101 consists of a thin wall anchored in the bony part of the femoral head 3 to stabilize and prevent rotation of the femoral cap around the cylindrical finger 90.

Each fin 101 is pierced with through holes 102 passing right through the thickness of the wall to form an area facilitating bone rehabilitation.

The inner face 8 has an inner cylindrical face portion 13 arranged from the peripheral edge 11 of the femoral cap 2 to the level of the equatorial axis YY 'of said femoral cap 2. The peripheral edge 11 has, for example, the opposite of the stabilization means 10, an inclined sector 110 whose lowest part is on the equatorial axis YY ', or slightly below the latter.

FIGS. 10 and 11 show a third variant of the femoral cap 2 and more particularly stabilizing means 10 for the re-surfacing implant 1 according to the present invention, knowing that the guiding means 9 are similar to those described previously.

The stabilizing means 10 consist of at least one fin 103 having a profile with three branches.

For this purpose, the fin 103 comprises a first branch 104 extending from the inner face 8 and towards the main axis XX 'of the femoral cap 2 and two other branches 105, 108 arranged in a direction which is perpendicular to that of the first branch so as to have, for example, a T-shaped profile

On the other hand, the branches 105, 108 may be arranged in a plane which is parallel to that containing the main axis XX 'of the femoral cap 2.

Each branch 104, 105 and 108 of the fin 103 consists of a thin wall anchored in the bony part of the femoral head 3 in order to stabilize and prevent any rotation of the femoral cap around the finger cylindrical 90.

Each branch 104, 105 and 108 of the fin 103 is pierced with through holes 106, 107 passing right through the thickness of the wall to form a zone facilitating bone rehabilitation. FIG. 12 shows a femoral cap 2 which is positioned around the femoral head 3 so that on the one hand the cylindrical finger 90 penetrates inside a blind hole 30 and on the other hand the flat 100 cooperates with the flat face 31 obtained after cutting the external articular surface 5.

Prior to the introduction of the femoral cap 2, the surgeon proceeds with the aid of an ancillary, not shown, to the section of the external articular surface 5 of the femoral head 3 and has an adequate femoral cap 2 which is from a game or a range of cap.

Note that the cylindrical finger 90 is introduced into the blind hole 30 of the femoral head 3 before the tapered rib 12 comes into contact with the edge of the articular surface 5. Then the surgeon exerts a pressure force on the femoral cap 2 so that the latter comes to impact in the femoral head 3 and cover the outer articular surface 5.

When fixing the femoral cap 2, it is noted that the tapered rib 12 penetrates into the thickness of the femoral head 3, close to the flat surface 31 made during the cutting of the external articular surface 5 to form an anchor and immobilization in rotation around the cylindrical finger of said femoral cap 2. It is noted that the cylindrical finger 90 of the femoral cap 2 ensures, during its introduction into the blind hole 30, mainly the guide of the latter during its phase of setting in place to obtain the most appropriate positioning possible. Also, the flat part 100 formed inside the femoral cap 2 bearing against the flat face 31 of the femoral head 3 prevents the tilting of said cap on the rotundity of said femoral head.

This setting up is an example and remains particular to that of the femoral cap 2 described in FIGS. 1 to 5.

Indeed, depending on the structure of the guide means 9 and stabilization means 10 retained, the establishment of the femoral cap 2 may be different.

Also, each variant described above remains an exemplary embodiment of a femoral cap 2 knowing that the combinations between the guide means 9 and the stabilizing means 10 as proposed are not limiting and can be modified without thereby changing the object of the present invention.

It must also be understood that the foregoing description has been given by way of example only and that it in no way limits the scope of the invention which could not be overcome by replacing the execution details described. by any other equivalent.

Claims

1. re-surfacing implant consisting of a femoral cap (2) having an outer face (7), an inner face (8), a peripheral edge (11), a central axis XX 'passing through the pole P of said cap (2), an equatorial axis YY 'perpendicular to the first and a point C of intersection between the main axes XX', YY 'forming the center of radius of curvature of said outer (7) and inner (8) faces, characterized in it comprises guiding means (9) which consist of a cylindrical finger (90) having a base (91) coming to connect with the inner face (8) at a point D which is laterally shifted relative to the pole P of the hemispherical profile of the femoral cap (2) and the stabilizing means (10) which are arranged on the periphery of the inner face (8) and having a profile which is arranged in a plane parallel to that containing the guide means (9).

2. re-surfacing implant according to claim 1, characterized in that the cylindrical finger (90) has, opposite the base (91), a free end (92) which is at the point C forming the center of radius of curvature of the outer (7) and inner (8) faces of the femoral cap (2).

3. re-surfacing implant according to claim 1, characterized in that the cylindrical finger (90) has, opposite the base (91), a free end (92) which lies between the peripheral edge ( 11) and the equatorial axis YY 'of the femoral cap (2).

4. re-surfacing implant according to claim 1, characterized in that the cylindrical finger (90) comprises an inclined pan (93) for producing a tapered profile.

5. re-surfacing implant according to claim 1, characterized in that the cylindrical finger (90) is pierced with at least one through hole (94) passing right through the thickness of said finger to form a facilitating area bone rehabilitation.

6. re-surfacing implant according to claim 1, characterized in that the cylindrical finger (90) comprises an inclined section (93) which is arranged in a plane which is parallel to that containing the main axis XX 'of the cap femoral 2.

7. re-surfacing implant according to claim 1, characterized in that the stabilization means (10) consist of a truncated profile obtained by at least one flat (100).

8. re-surfacing implant according to claim 7, characterized in that the flat (100) comprises a tapered rib (12) extending from the inner face (8) of the femoral cap (2).

9. re-surfacing implant according to claim 7, characterized in that the flat (100) is disposed in a plane which is parallel to that containing the cylindrical finger (90).

10. re-surfacing implant according to claim 1, characterized in that the stabilizing means (10) consist of at least one fin (101) extending from the inner face (8) and in the direction of the main axis XX 'of the femoral cap (2).

11. re-surfacing implant according to claim 10, characterized in that each fin (101) is pierced with through holes (102) to form an area facilitating bone rehabilitation.

12. re-surfacing implant according to claim 1, characterized in that the stabilizing means (10) consist of at least one fin (103) having a profile with three branches.

13. re-surfacing implant according to claim 12, characterized in that the fin (103) has a first leg (104) extending from the inner face (8) and towards the main axis XX of the femoral cap (2) and of two other branches (105, 108) arranged in a direction which is perpendicular to that of the first branch so as to have a T-shaped profile.

14. re-surfacing implant according to claim 13, characterized in that each branch (104, 105, 108) of the fin (103) is pierced with through holes (106, 107) to form a zone facilitating the rehabilitation bone.

15. re-surfacing implant according to claim 1, characterized in that the cylindrical finger (90) is carried by an axis ZZ 'passing through the center C.

16. re-surfacing implant according to claim 15, characterized in that the axis ZZ 'of the cylindrical finger (90) is arranged in a direction inclined at an angle α relative to the main axis XX' of the cap femoral (2).

17. re-surfacing implant according to claim 15, characterized in that the cylindrical finger 90 is carried by an axis AA 'offset laterally and parallel to the main axis XX' of the femoral cap 2.

18. re-surfacing implant according to claim 15, characterized in that the peripheral edge (11) has an inclined sector (110).

19. re-surfacing implant according to claim 1, characterized in that the inner face (8) has an inner cylindrical face portion (13) arranged from the peripheral edge (11) of the femoral cap (2) to level of the equatorial axis YY 'of said femoral cap.