FR3121836A1 - Femoral implant with grooves in the antero-posterior flanks - Google Patents

Abstract

Femoral implant comprising grooves in the antero-posterior flanks Femoral part of a hip prosthesis, consisting of an anchoring pin, or diaphyseal part, a metaphyseal part, or upper part, and a head part, intended to receive a ball joint to cooperate with the acetabular part 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) which extend at an angle with respect 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°, even more preferably between 10° and 30°. Figure for abstract: Fig. 1

Description

Femoral implant with grooves in the antero-posterior flanks

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

In general, the femoral implant of a hip prosthesis consists of a diaphyseal part and a metaphyseal part, the metaphyseal part being surmounted by a collar and a ball joint intended to be introduced into the acetabulum of the hip prosthesis. The diaphyseal part consists of an anchoring rod, intended to allow the guiding and anchoring of the femoral part in the medullary canal of the femur, while the metaphyseal part (or upper part of the femoral part) is flared towards the top.

The point of articulation of the patella at the neck of the metaphyseal part and the tip of the anchoring part define a mechanical axis of the prosthesis. A neutral axis making an angle with the mechanical axis and also starting from the tip of the anchor pin can be defined for the prosthesis. This neutral axis, which often corresponds to the anatomical axis of the prosthesis, is defined as being, in the plane in medio-lateral section, the bisector, starting from the vertex, the point of the anchoring part, between the two straight lines starting from this vertex and corresponding to the projections in the mid-lateral plane of the two respectively posterior and anterior surfaces of the anchor pin. This axis can also be defined as being the axis along which the tensile and compressive stresses that the prosthesis undergoes when a load is applied to the top of the head of the prosthesis, that is to say at the level of the patella, cancel each other out.

On the part of the prosthesis which is on the exterior side, or lateral, with respect to the neutral axis, the prosthesis undergoes a tensile stress. On the other side, that is to say the internal, or medial side, the prosthesis undergoes a compressive stress.

It is already known in the prior art, in particular from FR-A-2862865 in the name of the applicant, a femoral part of a hip prosthesis, consisting of an anchoring keel, or diaphyseal part, a part metaphyseal, or upper part, and a head part, intended to receive a ball joint to cooperate with the acetabular part 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 when a load is applied to the center of the femoral head, parallel to the neutral axis, notches being formed on the flanks of the metaphyseal part extending only in the inner or medial part of the prosthesis, i.e. between the neutral axis and the inner or medial side of the prosthesis, while steps are formed on the medial and lateral flanks of the metaphyseal part, the points of the cross section of the ribs which define them being oriented s upwards in the lateral aspect to oppose loosening of the femoral part in a femur, while the cross-sectional points of the ribs which define them point downwards in the medial aspect, to oppose the insertion of the femoral part into a femur.

By opposing the loosening of the prosthesis is meant the fact that the leading edges of the ribs are anchored in the internal wall of the femur in which the prosthesis is installed facing upwards, and therefore abut against this wall when attempting to remove it from the femur. Conversely, by opposing the depression is meant the fact of being anchored in the internal wall of the femur by being oriented downwards and therefore by abutting against the wall when the latter is depressed.

Although the above prostheses represent an advance in that, once mounted in a position anchored in the femur, they promote the formation of bone material and thus the reinforcement of their anchorage and their stability within the femur and, consequently , have an increased lifespan, in particular avoiding the depletion of bone material on the lateral side of the metaphyseal part, we would like to improve them even more, in particular in terms of stability and longevity.

The present invention thus aims for this purpose at a femoral part of a hip prosthesis, consisting of an anchor pin, or diaphyseal part, of a metaphyseal part, or upper part, and of a head part, intended to receive a ball joint for cooperating with the acetabular part 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 a load is applied on the center of the femoral head, parallel to the neutral axis, anteroposterior ribs, or AP, projecting from the anterior and/or posterior flanks of the metaphyseal part, having end edges which extend an angle with respect 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 comprised between 5° and 40°, even more preferably between 10° and 30°.

According to one embodiment, end edges, in particular the end edges, extend straight.

According to another embodiment, end edges, in particular the end edges, extend while being curved.

By thus providing an angle between the straight edges, substantially straight or slightly curved, 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 medio-lateral extent of the anterior and posterior flanks, i.e. from the medial flank to the lateral flank.

According to a preferred embodiment, the AP ribs have an end edge facing downwards, so as to oppose the insertion of the prosthesis into the femur, in particular the cross section of the ribs is triangular, the tip of the triangle being oriented downwards, that is to say 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 plane in medio-lateral section, the bisector, starting from the vertex consisting of the tip of the anchor keel, between the two straight lines starting from this vertex and corresponding to the projections in the mid-lateral plane of the two respectively medial and lateral faces of the anchor keel.

Preferably, the medial face of the metaphyseal part comprises so-called medial steps, the edges of which are oriented downwards, or towards the keel.

Preferably, the side face comprises so-called side steps whose edges are oriented upwards, or towards the head.

In particular, the medial steps are made up of a succession of upper facets turned upwards and lower facets turned 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 lateral steps are made up of a succession of upper facets facing upwards and lower facets facing downwards, and the plane of at least one of the upper facets forms 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 grooves AP 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, in particular only between the neutral axis and the lateral flank of the metaphyseal part.

In particular, the longitudinal grooves AP intersect the grooves formed between the ribs AP and cross these ribs AP.

In particular, the longitudinal grooves AP extend lengthwise in a direction parallel to the lengthwise direction of the grooves, in particular being parallel to the neutral axis.

By way of non-limiting example, an embodiment of a femoral part of a hip prosthesis according to the invention will now be described with particular reference to the drawings, in which:

The is a side view of a femoral part of a prosthesis according to the invention;

The represents part of the femoral part of the on a larger scale; and

The is a perspective view of the metaphyseal portion of the femoral portion of the .

In the figures, a femoral part 1 of a hip prosthesis is shown. This femoral part 1 comprises an anchoring keel 2, a flared upper part 3 and a head 4. The upper part 3 is also called the metaphyseal part of the femoral implant, while the anchoring keel 2 is also called the part diaphyseal. The head 4 of the prosthesis has a neck intended to receive a ball joint which will be mounted in the prosthetic acetabulum of the prosthesis (not shown in the figures). The upper part 3 comprises two respectively anterior 6 and posterior flanks (not visible in the figures), an outer or lateral flank 7 and an inner or medial flank 8. Interior, exterior, upper and lower are defined in the mounted state of the part prosthesis femoral joint in a patient's body.

The femoral part 1 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 embedded at a height of 80 mm from the center of the femoral head and a load of 6,000 Newtons is applied to the top of this head, vertically (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. A representative diagram of the tensile and compressive stresses is thus obtained for each point between the external edge and the internal edge of the prosthesis. The neutral axis corresponds to all the points, for each height of the prosthesis (compared to the tip of the keel), where the tensile and compressive stresses cancel each other out. This neutral axis 9 thus defines an outer or lateral part and an inner or medial part of the metaphyseal part.

Another way of defining the neutral axis consists in considering in the medio-lateral plane the bisector starting from the point formed by the top 10 of the keel 2, the bisector between the two respectively medial and lateral faces of the keel starting from this peak peak 10.

Grooves 11 are formed in the respectively anterior and posterior flanks of the metaphyseal part, extending substantially straight from the lateral flank to the medial flank. The ribs formed between the grooves have substantially straight respective end edges 12 which are parallel to each other and which each form an angle with the perpendicular 13 to the neutral axis 9 which is 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 is defined its tangent at this 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° over at least 50% of the edge, preferably over at least 60% of the edge, even more preferably over at least least 70% of the edge, very preferably over at least 80% of the edge, even more preferably over at least 90% of the edge, in particular over the entire edge.

The series of grooves 11 is made in such a way that the intermediate ribs oppose the insertion of the prosthesis into the femur. Thus, in section in the vertical plane, the ribs have a "fir tree" shape, i.e. triangular whose point is oriented downwards, i.e. towards the anchor keel (We define the up and down directions relative to the mounted state of the prosthesis in the femur).

The anchor keel, on the other hand, has 14 longitudinal grooves, that is to say parallel to the longitudinal axis of the keel, which merges with the neutral 9 axis.

Medial steps 15 are formed in the medial flank of the metaphyseal portion and lateral steps 16 are formed in the lateral flank of the metaphyseal portion.

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 vertical medio-lateral section (perpendicular to the antero-posterior 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 mid-lateral section (perpendicular to the antero-posterior 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°.

It is dug in the anterior and posterior flanks of the metaphyseal part, on the lateral side of the neutral axis 9, longitudinal grooves 21 which intersect the grooves 11 crossing the intermediate ribs. These longitudinal grooves 21 extend lengthwise in a direction parallel to the lengthwise direction of the grooves 14, in particular being parallel to the neutral axis 9.

Claims (12)

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 part, intended to receive a ball joint to cooperate with the acetabular part of the hip prosthesis, the prosthesis having a neutral axis (9), anteroposterior ribs, or AP, protruding from the anterior and/or posterior flanks of the metaphyseal part, having end edges (12) which extend at an angle with respect 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 comprised between 5° and 40°, even more preferably between 10° and 30°. Femoral part according to Claim 1, characterized in that the ribs AP extend over substantially the entire medio-lateral extent of the anterior and posterior flanks, that is to say from the medial flank to the lateral flank. Femoral part according to Claim 1 or 2, characterized in that the ribs AP have an end edge directed downwards, so as to oppose the insertion of the prosthesis into the femur, in particular the cross section of the ribs is triangular, the tip of the triangle pointing downwards, i.e. towards the keel part. Femoral part according to one of the preceding claims, characterized in that the medial face of the metaphyseal part comprises so-called medial steps, the edges of which are oriented downwards, or towards the keel. Femoral part according to one of the preceding claims, characterized in that the lateral face comprises so-called lateral steps whose edges are oriented upwards, or towards the head. Femoral part according to Claim 4 or 5 when it depends on Claim 4, characterized in that the medial steps consist of a succession of upper facets facing upwards and lower facets facing downwards, and the upper plane least one of the lower facets forms an angle with the perpendicular to the neutral axis, in particular an angle comprised between 10° and 30°. Femoral part according to Claim 5 or 6 when it depends on Claim 5, characterized in that the lateral steps consist of a succession of upper facets facing upwards and lower facets facing downwards, and the upper plane least one of the upper facets forms an angle with the perpendicular to the neutral axis, in particular an angle comprised between 10° and 30°. Femoral part according to one of the preceding claims, characterized in that mutually parallel longitudinal grooves (14) are provided in the diaphyseal part of the prosthesis, the longitudinal axis of which runs parallel to the neutral axis . Femoral part according to one of the preceding claims, characterized in that longitudinal grooves (21) AP are formed in the anterior and/or posterior flanks, between the neutral axis and the lateral flank of the metaphyseal part. Femoral part according to Claim 9, characterized in that longitudinal grooves (21) AP are formed in the anterior and/or posterior flanks, only between the neutral axis and the lateral flank of the metaphyseal part. Femoral part according to Claim 9 or 10, characterized in that the longitudinal grooves (21) AP intersect the grooves formed between the ribs AP and pass through these ribs AP. Femoral part according to Claims 8 and 9 or 10, characterized in that the longitudinal grooves (21) AP extend lengthwise in a direction parallel to the lengthwise direction of the grooves (14).