Femoral implant with grooves in the anteroposterior flanks

Abstract

Femoral implant having grooves in the anteroposterior flanks. Femoral part of a hip prosthesis, consisting of an anchoring keel, or diaphyseal part, a metaphyseal part, or upper part, and a head part, intended to receive a patella to cooperate with the acetabular component of the hip prosthesis, the prosthesis having a neutral axis (9), anteroposterior ribs, or AP, projecting from the anterior and / or posterior flanks of the metaphyseal part, having end edges (12) extending at an angle to the neutral axis, characterized in that the end edges of the ribs form an angle with the perpendicular (13) to the neutral axis, in particular between 5° and 40°, more preferably between 10° and 30°. Figure for the abbreviation: Fig. 1

Description

Description Title of the invention: Femoral implant comprising grooves in the anteroposterior flanks

[0001] — The present invention relates to a femoral implant of a hip prosthesis. The The present invention also relates to a hip prosthesis comprising a femoral implant according to the invention.

[0002] — In general, the femoral implant of a hip prosthesis consists of a dia- physeal and metaphyseal part, the metaphyseal part being surmounted by a neck and a patella designed to be inserted into the acetabulum of the hip prosthesis. The The diaphyseal part consists of an anchoring rod, designed to allow guidance and the anchoring of the femoral component in the medullary canal of the femur, while the part The metaphysis (or upper part of the femoral component) is flared upwards.

[0003] — The articulation point of the patella at the level of the neck of the metaphyseal part and the The tip of the anchoring part defines a mechanical axis of the prosthesis. An axis neutral forming an angle with the mechanical axis and also originating from the tip of the An anchoring keel can be defined for the prosthesis. This neutral axis, which corresponds often at the anatomical axis of the prosthesis, is defined as being, in the plane in mediolateral section, the bisector, starting from the apex, the tip of the part anchoring, between the two lines starting from this vertex and corresponding to the pro- projections in the mediolateral plane of the two surfaces respectively posterior and an- external to the anchor keel. This axis can also be defined as the axis along which the tensile and compressive stresses that the prosthesis undergoes when a load is applied to the top of the prosthesis head, that is to say at the level of the kneecap, cancel each other out.

[0004] — On the part of the prosthesis that is on the outer, or lateral, side, relative to On the neutral axis, the prosthesis is subjected to tensile stress. On the other side, that is to say the On the internal, or medial, side, the prosthesis is subjected to compressive stress.

[0005] It is already known in the prior art, notably from FR-A-2862865 in the name of the de- Manderesse, a femoral part of a hip prosthesis, consisting of a keel anchoring, or diaphyseal part, of a metaphyseal part, or upper part, and of a head section, designed to receive a ball joint to cooperate with the coty- part loidal of the hip prosthesis, the prosthesis having a neutral axis, that is to say an axis along which the tensile and compressive stresses cancel each other out when it is applied a load to the center of the femoral head, parallel to the neutral axis, of the notches being formed on the sides of the metaphyseal part as they extend only in the inner or medial part of the prosthesis, that is to say between the axis neutral and the inner or medial side of the prosthesis, while steps are formed on the medial and lateral sides of the metaphyseal part, the tips of the cross-section of the ribs that define them being oriented upwards in the lateral face to oppose the loosening of the femoral part in a femur, while the tips of the cross-section of the ribs that define them being oriented downwards in the medial face, to oppose the sinking of the femoral part into a femur. Preventing loosening of the prosthesis means ensuring that the leading edges of the ribs anchor themselves to the inner wall of the femur in which the prosthesis is inserted, facing upwards, and therefore abut against this wall when an attempt is made to remove it. Conversely, preventing settling means ensuring that the ribs anchor themselves to the inner wall of the femur, facing downwards, and therefore abut against the wall when the prosthesis is inserted. Although the above prostheses represent an advance in that, once mounted in an anchored position in the femur, they promote the formation of bone tissue and thus strengthen their anchorage and stability within the femur and, consequently, have an increased lifespan, avoiding in particular the depletion of bone material on the lateral side of the metaphyseal part, we would like to improve them even further, particularly in terms of stability and longevity. The present invention thus relates to a femoral component of a hip prosthesis, consisting of an anchoring keel, or diaphyseal component, a metaphyseal component, or upper component, and a head component intended to receive a patella for cooperation with the acetabular component of the hip prosthesis. The prosthesis has a neutral axis, that is, an axis along which tensile and compressive stresses cancel each other out when a load is applied to the center of the femoral head. Parallel to the neutral axis, anteroposterior ribs, or AP, project from the anterior and / or posterior flanks of the metaphyseal component, with end edges extending at an angle to the neutral axis, is characterized in that the end edges of the ribs form an angle with the perpendicular to the neutral axis, in particular between 5° and 40°, and more preferably between 10° and 30°. According to one embodiment, end edges, in particular the end edges, extend in a straight line. According to another embodiment, end edges, in particular end edges, extend by being curved. By thus providing an angle between the straight, substantially straight or slightly curved edges of the ribs and the perpendicular to the neutral axis, the bone is stressed in compression rather than in shear, which improves its long-term stability. Preferably, the AP ribs extend over substantially the entire mid- extent lateral of the anterior and posterior flanks, that is to say from the medial flank to the lateral flank. According to a preferred embodiment, the AP ribs have an end edge oriented downwards, so as to oppose the penetration of the prosthesis into the femur, in particular the cross section of the ribs is triangular, the point of the triangle being oriented downwards, i.e. towards the keel part. According to a preferred embodiment of the invention, the neutral axis corresponds to the anatomical axis of the prosthesis, in particular being defined as being, in the mediolateral cross-section plane, the bisector, starting from the apex formed by the tip of the anchoring keel, between the two lines starting from this apex and corresponding to the projections in the mediolateral plane of the two faces respectively medial and lateral of the anchoring keel. Preferably, the medial face of the metaphyseal part has so-called medial steps whose edges are oriented downwards, or towards the keel. Preferably, the side face has so-called lateral steps whose edges are oriented upwards, or towards the head. In particular, the medial steps consist of a succession of upper facets facing upwards and lower facets facing downwards, and the plane of at least one of the lower facets makes an angle with the perpendicular to the neutral axis, in particular an angle between 10° and 30°. In particular, the side steps consist of a succession of upper facets facing upwards and lower facets facing downwards, and the plane of at least one of the upper facets makes an angle with the perpendicular to the neutral axis, in particular an angle between 10° and 30°. According to a preferred embodiment of the invention, mutually parallel longitudinal grooves are provided in the diaphyseal part of the prosthesis, the longitudinal axis of which extends parallel to the neutral axis. Preferably, longitudinal AP grooves are formed in the anterior and / or posterior flanks, between the neutral axis and the lateral flank of the metaphyseal part. In particular, longitudinal grooves are formed in the anterior and / or posterior flanks, between the neutral axis and the lateral flank of the metaphyseal part, specifically only between the neutral axis and the lateral flank of the metaphyseal part. In particular, the longitudinal AP grooves intersect the oriented grooves between the AP ribs and pass through these AP ribs. In particular, the longitudinal grooves AP extend lengthwise in a direction parallel to the lengthwise direction of the grooves, notably by being parallel to the neutral axis. As a non-limiting example, we now describe a method of implementing a femoral part of a hip prosthesis according to the invention, with particular reference to the drawings, in which: Fig. 1 is a side view of a femoral part of a prosthesis according to the invention; Figure 2 represents a larger-scale portion of the femoral part of Figure 1; and Fig. 3 is a perspective view of the metaphyseal part of the femoral part of Fig. 1. The figures show a femoral component 1 of a hip prosthesis. This femoral component 1 comprises an anchoring keel 2, a flared upper portion 3, and a head 4. The upper portion 3 is also called the metaphyseal portion of the femoral implant, while the anchoring keel 2 is also called the diaphyseal portion. The head 4 of the prosthesis has a neck for receiving a patella, which will be mounted in the prosthetic acetabulum of the prosthesis (not shown in the figures). The upper portion 3 comprises two flanks, respectively anterior 6 and posterior (not visible in the figures), an outer or lateral flank 7, and an inner or medial flank 8. Inner, outer, upper, and lower are defined in the mounted state of the femoral component of the prosthesis within the patient's body. The femoral part of the prosthesis has a neutral axis 9. This neutral axis can be determined for the prosthesis as follows, as also described in FR-A-2862865. The prosthesis is fixed at a height of 80 mm from the center of the femoral head, and a load of 6,000 Newtons is applied vertically to the apex of this head (parallel to the longitudinal axis of the keel). The stresses are then evaluated, either by calculation or by applying strain and displacement gauges to the body of the prosthesis. This yields, for each point between the outer and inner edges of the prosthesis, a representative diagram of the tensile and compressive stresses. The neutral axis corresponds to the set of points, for each height of the prosthesis (relative to the tip of the keel), where the tensile and compressive stresses cancel each other out.This neutral axis 9 thus defines an external or lateral part and an internal or medial part of the metaphyseal portion. Another way to define the neutral axis is to consider in the mediolateral plane the bisector from the point formed by the apex 10 of the keel 2, the bisector between the two faces respectively medial and lateral of the keel starting from this apex 10. Grooves 11 are formed in the anterior and posterior flanks of the metaphyseal part, respectively, extending substantially straight from the lateral to the medial flank. The ribs formed between the grooves have substantially straight end edges 12 that are parallel to each other and each makes an angle with the perpendicular 13 to the neutral axis 9, which is comprised of Preferably between 10° and 30°. In the case where the end edges 12 of the ribs and the grooves 11 extend while being curved, at each point of an end edge 12 its tangent is defined at that point, and according to the invention the angle of this tangent with the perpendicular 13 to the neutral axis is between 5 and 40°, between 10° and 30° on at least 50% of the edge, preferably on at least 60% of the edge, even more preferably on at least 70% of the edge, very preferably on at least 80% of the edge, even more preferably on at least 90% of the edge, in particular on the whole edge. The series of grooves 11 is designed so that the intermediate ribs resist the prosthesis from sinking into the femur. Thus, in section in the vertical plane, the ribs have a "fir tree" shape, i.e. triangular with the point oriented downwards, i.e. towards the anchoring keel (The upward and downward directions are defined relative to the mounted state of the prosthesis in the femur). The anchor keel, for its part, has 14 longitudinal grooves, that is to say parallel to the longitudinal axis of the keel, which coincides with the neutral axis 9. 15 medial steps are formed in the medial flank of the metaphyseal part and 16 lateral steps are formed in the lateral flank of the metaphyseal part. Steps 15 and 16 are defined by alternating successions of upper facets 17, 19 oriented upwards and lower facets 18, 20 oriented downwards. The upper facets 19 (in particular the lower upper facet) of the lateral steps 16 make, in mediolateral vertical section (perpendicular to the anteroposterior axis), an angle B with the perpendicular 13 to the neutral axis 9 which is greater than 0°, in particular which is between 10° and 30°. The lower facets 18 (in particular the lowest lower facet 18) of the medial steps 15 make, in vertical mediolateral section (perpendicular to the anteroposterior axis), an angle A with the perpendicular 13 to the neutral axis 9 which is greater than 0°, in particular which is between 10° and 30°. In the anterior and posterior flanks of the metaphyseal part, on the lateral side of the neutral axis 9, longitudinal grooves 21 are cut into the anterior and posterior sides, crossing the intermediate ribs. These longitudinal grooves 21 extend lengthwise in a direction parallel to the longitudinal direction of the grooves 14, in particular by being parallel to the neutral axis 9.

Claims

Demands

1. Femoral part of a hip prosthesis, consisting of an anchoring keel, or diaphyseal part, of a metaphyseal part, or upper part, and of a head section, designed to receive a ball joint to cooperate with the acetabular component of the hip prosthesis, the prosthesis having an axis (9) neutral, of the anteroposterior ribs, or AP, projecting from the anterior and / or posterior flanks of the metaphyseal part, having end edges (12) which extend at an angle to the neutral axis, characterized in that the end edges of the ribs make an angle with the perpendicular (13) to the neutral axis, in particular between 5° and 40°, more preferably between 10° and 30°.

2. Femoral part according to claim 1, characterized in that the AP ribs extend over virtually the entire mediolateral extent the anterior and posterior flanks, that is to say from the medial flank to the lateral side.

3. Femoral part according to claim 1 or 2, characterized in that AP ribs have a downward-facing end edge, so to oppose the insertion of the prosthesis into the femur, in particular the cross-section of the ribs is triangular, the apex of the triangle being oriented downwards, that is to say towards the keel part.

4. Femoral part according to any one of the preceding claims, ca- characterized in that the medial face of the metaphyseal part comprises so-called medial tiers whose edges are oriented downwards, or towards the keel.

5. Femoral part according to one of the preceding claims, ca- characterized in that the lateral face has so-called lateral steps whose edges are oriented upwards, or towards the head.

6. Femoral part according to claim 4 or 5 when it depends on the claim 4, characterized in that the medial steps are consisting of a succession of upward-facing upper facets and of downward-facing lower facets, and the plane of at least one of the The lower facets form an angle with the perpendicular to the neutral axis. in particular an angle between 10° and 30°.

7. Femoral part according to claim 5 or 6 when it depends on the claim 5, characterized in that the side steps are consisting of a succession of upward-facing upper facets and of downward-facing lower facets, and the plane of at least one of the the upper facets form an angle with the perpendicular to the neutral axis, in particular an angle between 10° and 30°.

8. Femoral part according to one of the preceding claims, ca- characterized in that it is provided for, in the diaphyseal part of the prosthesis, mutually parallel longitudinal grooves (14), whose longitudinal axis gitudinal extends parallel to the neutral axis.

9. Femoral part according to one of the preceding claims, ca- characterized in that longitudinal grooves (21) AP are formed in the anterior and / or posterior flanks, between the neutral axis and the flank lateral of the metaphyseal part.

10. Femoral part according to claim 9, characterized in that longitudinal grooves (21) AP are formed in the anterior flanks and / or posterior, only between the neutral axis and the lateral flank of the metaphyseal part.

11. Femoral part according to claim 9 or 10, characterized in that the longitudinal grooves (21) AP intersect the grooves formed between the AP ribs and cross these AP ribs.

12. Femoral part according to claims 8 and 9 or 10, characterized in that the longitudinal grooves (21) AP extend in length following a direction parallel to the longitudinal direction of the grooves (14).