FR2867060A1 - Femoral implant for hip prosthesis, has metaphyseal and diaphyseal parts whose dorsal and lateral sides form dorsal lateral sharp edge, where frontal and dorsal and medial sides of diaphyseal part form frontal and dorsal medial sharp edges - Google Patents

Abstract

The implant has frontal and lateral sides of metaphyseal and diaphyseal parts (8, 9) forming, at their junction, a frontal lateral sharp edge. Dorsal and lateral sides of the parts form, at their junction, a dorsal lateral sharp edge. Frontal (9f) and medial sides of the part (9) form, at their junction, a frontal medial sharp edge. Dorsal (9d) and medial sides of the part (9) form, at their junction, a dorsal medial sharp edge.

Description

The present invention relates to the technical field of implants

  orthopedic and, more particularly, prostheses used to rehabilitate the hip joint of the human body.

  The subject of the invention is more particularly directed towards the part of the hip prosthesis which is placed in the femur, after resection of the latter, within the framework of the interventions intended to rehabilitate the hip-femoral joint.

  In the technical field above, it is now customary to implant femoral implants which are intended to cooperate with a cup adapted on the hip.

  Such femoral implants have been the subject of many technical proposals that can be classified into two main families, namely femoral implants with straight shanks and anatomical femoral implants which have a curved shank whose concavity is oriented towards the femur. 'before the patient.

  The stems of the first category are qualified as straight, given their general conformation, which gives them a general appearance of a mechanical part rather than a biomechanical prosthesis, so that their appearance leads some surgeons not to use them and so that Generally, right stem prostheses are made to have softened shapes.

  However, if such straight stem prostheses are generally satisfactory, it was found that their performance after implantation could be further improved and the inventors had the merit of highlighting that this improvement could be obtained by pushing until end the concept of the right stem and abandoning any temptation to soften the shape of the prosthesis.

  In order to achieve this objective, the invention relates to a femoral implant for a hip prosthesis comprising an intra-medullary stem extended by a neck, with axis A for fixing a head, the stem having, from the cervix, a metaphyseal portion of axis D extending by a diaphyseal portion of axis A ', followed by a distal end tip.

  According to the invention, the femoral implant is characterized in that: the metaphyseal part comprises a lateral face, a front face and a dorsal face which are all three substantially planar, the front and rear faces converging, on the one hand, towards a medial side and, on the other hand, towards the diaphyseal part, the diaphyseal part comprises a lateral face, a medial face, a front face and a dorsal face, all of which are substantially plane, the medial and lateral faces converging towards the distal end point, the frontal and lateral faces of the metaphyseal and diaphyseal parts form at their junction a sharp frontal lateral ridge, the dorsal and lateral faces of the metaphyseal and diaphyseal parts form, at their junction, a dorsal lateral ridge the frontal and medial sides of the diaphyseal part form, at their junction, a sharp frontal medial edge, the dorsal and lateral sides of the diaphyseal part form, at their junction, a sharp dorsal medial edge.

  The adoption of this conformation, which seems a priori anti-anatomical, combining both sharp edges and wedge shapes for the various constituent parts of the femoral implant, allows, on the contrary and surprisingly, to obtain a femoral implant that fits into the walls of the medullary canal and gets stuck in it, so that after its implantation, the femoral implant and more particularly its intramedullary rod has a very high resistance to rotation and then offers a very high security for the paired patient.

  According to the invention, the terms "sharp edges" are understood to mean ridges having, in cross-section, a radius of less than 0.8 mm and, preferably, less than 0.6 mm.

  According to one characteristic of the invention, in order to promote the anteroposterior stability of the stem in the medullary canal, the frontal and dorsal faces of the metaphyseal part form, in projection in the sagittal plane, an angle α of between 9 and 14 and, preferably between 9 45 'and 13.

  According to another characteristic of the invention and still with a view to providing better stability of the stem in the medullary canal, the dorsal and frontal faces of the metaphyseal part form, in transverse cross section, an angle b of between 5 and 7 and preferably between 45 'and 6.

  It should be noted that, according to a preferred but not strictly necessary characteristic of the invention, the end faces, on the one hand, and the dorsal, on the other hand, of the metaphyseal and diaphyseal parts of the stem are not coplanar and have a different convergence angle. Thus according to the invention and preferably but not strictly necessary, the front and rear faces of the metaphyseal portion have a convergence angle α greater than the convergence angle c of the front and rear faces of the diaphyseal portion.

  Similarly, in order to promote the stability of the rod, again in the medullary canal, according to another characteristic of the invention, the medial and lateral faces of the diaphyseal part form, in projection in the frontal plane, an angle e between 2 and 4 and preferably between 50 'and 3.

  According to another characteristic of the invention, the lateral faces of the metaphyseal and diaphyseal parts form, in projection in a frontal plane, an angle f between 7 and 10 and, preferably, between 8 and 9.

  According to the invention, the femoral implant is, preferably but not strictly necessary, made to have a straight stem. Thus, the axes A, D and A 'are substantially coplanar and contained in a plane parallel to the frontal plane.

  Still in the sense of a better stability of the stem in the medullary canal, the metaphyseal portion has, in a central region and in cross section along the axis D, substantially the shape of an isosceles trapezium, called metaphyseal, of which the large base corresponds to the lateral face, the sides correspond to the frontal and dorsal sides, the small base corresponds to the medial side.

  Preferably, the sides of the metaphyseal trapezium then form, with the large base, an angle g between 86 and 88 and preferably between 87 and 87 15 '.

  In the same direction, in order to promote the distal stability of the stem in the medullary canal, the diaphyseal portion has, in cross section transverse to the axis A ', substantially the shape of an isosceles trapezium, said diaphyseal, the great base corresponds to the lateral face, the sides correspond to the frontal and dorsal sides, the small base corresponds to the medial side.

  Preferably, the sides of the diaphyseal trapezium then form, with the large base, an angle h between 88 and 89 and, preferably, between 88 40 'and 88 50'.

  According to another characteristic of the invention, the axes A, A 'of the neck and of the diaphyseal part form a cervico-diaphyseal angle α, of between 125 and 140.

  According to yet another characteristic of the invention, the axes D and A 'of the metaphyseal part and of the diaphyseal part form an angle (3 of between 158 and 162 and is preferably 160.

  Of course, according to the invention, the rod can be made to have different sizes.

  Various other characteristics of the invention emerge from the description below made with reference to the accompanying drawings which show a preferred non-limiting embodiment of a femoral insert according to the invention.

  Fig. 1 is a front view, in the frontal plane F, of a left femoral implant according to the invention.

  Fig. 2 is a side view, in a sagittal plane S perpendicular to the frontal plane F, of the femoral implant according to FIG. 1.

  Fig. 3 is a cross section along the line III-III of FIG. 1.

  Fig. 4 is a cross section along the line IV-IV of FIG. 1.

  A femoral implant according to the invention, as illustrated in FIGS. 1 and 2 and designated as a whole by the reference 1, comprises an intramedullary rod 2 extended by a neck 3. The anatomical femoral implant 1, illustrated in FIGS. 1 and 2, is intended to be adapted in a left femur. Of course, the invention relates, indifferently, femoral implants left or right. Thus, a right femoral implant according to the invention and intended to be inserted into a patient's right femur would be symmetrical to the implant 1 with respect to the sagittal plane S, so that the left and right implants would be enantiomorphic.

  The neck 3 is intended to receive a hinge head, not shown. For this purpose, the neck 3 has, at its proximal end 5, a matching cone 6 whose characteristics are widely known to those skilled in the art.

  The intramedullary stem 2 is, as its name suggests, intended to be engaged in the medullary canal of the femur paired and has, from the neck 3, a metaphyseal portion 8 extending by a diaphyseal portion 9 which ends with a tip distal end 10.

  As is apparent from FIG. 1, the intramedullary rod 2 has, on the one hand, a lateral face 11 which has a general shape, seen in the frontal plane F, convex and, on the other hand, a medial face 12 which has a general shape, always seen in the frontal plane F, concave.

  According to a characteristic of the invention, the axis A of the neck 3, the axis D of the metaphyseal part 8 and the axis A 'of the diaphyseal part 9 are coplanar and, in projection in the sagittal plane S, like this is illustrated in FIG. 2, aligned, while in projection in a frontal plane F, as illustrated in FIG. 1, the axis A of the neck 3 and A 'of the diaphyseal portion 9 form a cervico-diaphyseal angle α of between 125 and 140 and, preferably but not exclusively, equal to 135.

  Similarly, in projection in the frontal plane F, the axes D and A 'of the metaphyseal 8 and diaphyseal portions 9 form an angle, preferably, 160.

  According to an essential characteristic of the invention, the metaphyseal portion 8 comprises a front face 8f, a back face 8d and a side face 81 which are all three substantially planar. The metaphyseal portion 8 also comprises, opposite its lateral face 81, a medial face Sm which, in projection in the sagittal plane S, has a curved shape. In order to allow a good wedging of the stem and, more particularly, of its metaphyseal part 8, the end faces 8 f and dorsal 8d converge, on the one hand, towards the diaphyseal part 9, as is clear from FIG. 2, and, on the other hand, towards the medial side 8m of the metaphyseal part, as is apparent from the section illustrated in FIG. 3.

  Preferably, the front 8f and dorsal 8d faces of the metaphyseal part then form, in projection in the sagittal plane S, an angle a between 9 and 14 and preferably between 9 45 'and 13.

  In the same way, the frontal 8f and dorsal faces 8d of the metaphyseal part form, in transverse cross-section, a convergence angle b of between 45 'and 6.

  In order to contribute to the stability of the implant, the diaphyseal portion 9 comprises a lateral face 91, a medial face 9m, a front face 9f and a dorsal face 9d all of which are substantially planar.

  It should be noted that, preferably, the front 9f and dorsal faces 9d of the diaphyseal portion 9 are parallel or converge towards the distal end point 10 and form, in projection in the sagittal plane S, a strictly smaller angle c at the angle of convergence has front faces 8f and dorsal 8d of the metaphyseal portion 8. Thus the angle c may be between 6 and 7. This angular break between, on the one hand, the end faces 8f, 9f and, on the other hand, the dorsal faces 8d, 9d of the metaphyseal and diaphyseal parts creates a wedge effect particularly favorable to the blockage of the stem in the medullary canal. .

  Furthermore, according to the invention and preferably but not strictly necessary, the front 9f and dorsal faces 9d of the diaphyseal portion converge, also, towards the medial face 9m, forming an angle d between 2 30 'and 3 30 and preferably between 3 and 15 '.

  In addition, the medial and lateral faces 9 and 91 converge towards the distal end point and then form, in projection in the frontal plane, an angle e between 2 50 'and 3.

  The distal end portion 10 then has a pyramidal or ogival shape in continuity with the shape of the diaphyseal portion 9.

  According to another essential characteristic of the invention, in order to allow a perfect wedging or blocking of the stem 2 in the medullary canal of the paired femur, the front and lateral faces of the metaphyseal and diaphyseal parts form, at their junctions, a sharp frontal edge. 20, while the dorsal and lateral faces of these same metaphyseal and diaphyseal parts form, at their junctions, a sharp dorsal lateral ridge 21.

  In the same way, the frontal and medial, on the one hand, and dorsal and medial sides, on the other hand, of the diaphyseal part 9 form, at their junctions, respectively, a sharp frontal medial edge 22 and a dorsal medial edge. live 23.

  The sharp or sharp character of the edges 21, 20, 22 and 23 then contributes to a good embedding of the intramedullary rod 2 in the resected medullary canal of the paired femur. According to the invention this lively character of the edges 21, 20, 22 and 23 corresponds to a junction surface between the relevant faces having a radius of curvature in transverse cross section, as illustrated in FIG. 3 and 4, less than 0.8 mm and preferably less than 0.6 mm, 0.5 mm being an optimum compromise in the manufacture of the rod by forging without recovery or sharpening of the edges 21, 20, 22 and 23.

  Similarly, again with a view to ensuring better stability, the lateral faces 81 and 91 of the metaphyseal 8 and diaphyseal portions 9 form, in projection in the frontal plane, an angle f between 8 and 9.

  Still in order to promote blockage of the prosthesis in the intramedullary canal, the metaphyseal part presents, preferably but not necessarily, in the central region 15 and in cross section along its axis D, substantially the shape of an isosceles trapezium, said metaphyseal, as shown in fig. 3, whose large base corresponds to the lateral face 81 and the small base to the medial face 8m of the metaphyseal part.

  In a preferred embodiment, the sides of the metaphyseal trapezium, formed by the dorsal 8d and frontal 8f, form, with the large base 81, an angle g between 86 and 88 and preferably between 87 and 87. .

  In the same way, the diaphyseal portion has, preferably but not strictly necessary, cross-section in the axis to ', as illustrated in FIG. 4, substantially the shape of an isosceles trapezium, said diaphyseal, whose large base corresponds to the lateral face 91 of the diaphyseal portion 9 and the sides correspond to the front 9f and dorsal 9d of this same part, while the small base corresponds to the medial side 9m.

  Preferably, the sides of the diaphyseal trapezium then form, with the large base 91, an angle h between 88 40 'and 88 50'.

  Moreover, it should be noted that, according to the invention, the metaphyseal portion has a side of an upper face 25 substantially flat and perpendicular to the axis e 'of the diaphyseal portion 9.

  Of course, the invention is not limited to the examples described and shown because various modifications can be made without departing from its scope.

Claims (11)

  1 - Femoral implant, for hip prosthesis, comprising an intramedullary rod (2), extended by a neck (3) of axis A for fixing a head (4), the stem having, from the neck (2) , a metaphyseal part (8) of axis D extending by a diaphyseal portion (9) of axis A 'and then a distal end point (10), characterized in that: the metaphyseal part (8) comprises a lateral face (81), a front face (8f) and a dorsal face (8d) all of which are substantially planar, the front (8f) and dorsal (8d) faces converging, on the one hand, towards a medial face (8m) ) and, on the other hand, towards the diaphyseal portion (9), the diaphyseal portion (9) comprises a lateral face (91), a medial face (8m), a front face (8f) and a dorsal face (9d). ), all four of which are substantially planar, the medial (9m) and lateral (91) faces converging towards the distal end point (10), the front (8f, 9f) and lateral (81, 91) faces of the parts me taphyseal (8) and diaphyseal (9) form, at their junction, a sharp frontal lateral edge (20), the dorsal (8d, 9d) and lateral (81, 91) sides of the metaphyseal (8) and diaphyseal (9) ) form, at their junction, a sharp dorsal lateral edge (21), the front (9f) and medial (9m) sides of the diaphyseal part (9) form, at their junction, a sharp frontal medial edge (22), the dorsal (9d) and medial (9m) sides of the diaphyseal portion (9) form, at their junction, a sharp dorsal medial edge (23).   2 - femoral implant according to claim 1, characterized in that the front (8f) and dorsal (8d) sides of the metaphyseal part (8) form, in projection in the sagittal plane S, an angle a of between 9 and 14 and preferably between 9 45 'and 13.   3 - femoral implant according to claim 1 or 2, characterized in that the front (9 f) and dorsal (9d) of the diaphyseal portion (9) form, in projection in the sagittal plane S, an angle c strictly less than the angle of convergence of the front (8 f) and dorsal (8d) faces of the metaphyseal part (8).   4 - femoral implant according to one of claims 1 to 3, characterized in that the medial (9m) and lateral (91) of the diaphyseal portion (9) form, in projection in the frontal plane F, an angle e included between 2 and 4 and preferably between 2 50 'and 3.   Femoral implant according to one of claims 1 to 4, characterized in that the lateral faces (81, 91) of the metaphyseal (8) and diaphyseal portions (9) form, in projection in a frontal plane F, an angle f inclusive. between 7 and 10 and preferably between 8 and 9.   6 - femoral implant according to one of claims 1 to 5, characterized in that the axes A, D, A 'are substantially coplanar and contained in a plane parallel to the frontal plane F. 7 - femoral implant according to one of the claims 1 to 6, characterized in that the front (8f) and dorsal (8d) sides of the metaphyseal part (8) form, in cross section, an angle b of between 5 and 7 and preferably between 45 and 6 8 - femoral implant according to one of claims 1 to 7, characterized in that the metaphyseal part (8) has, in a central region (15) and in cross section in the axis D, substantially the shape of an isosceles trapezium, called metaphyseal, whose large base corresponds to the lateral face (81), the sides correspond to the frontal (8f) and dorsal (8d) faces, the small base corresponds to the medial face (8m).   9 - femoral implant according to claim 8, characterized in that the sides (8d, 8f) of the metaphyseal trapezium form, with the large base (81), an angle g between 87 and 88 and, preferably, between 87 and 87 15 '.   10 - femoral implant according to one of claims 1 to 9, characterized in that the diaphyseal portion (9) has, in cross section transverse to the axis A ', substantially the shape of an isosceles trapezium, said diaphyseal, of which the large base (91) corresponds to the lateral face, the sides correspond to the front (9f) and dorsal (9d) sides, the small base corresponds to the medial face (9m).   11 - femoral implant according to claim 10, characterized in that the sides (9f, 9d) of the diaphyseal trapezium form, with the large base (91), an angle h between 88 and 89 and, preferably, between 88 40 'and 88 50'.   12 - femoral implant according to one of claims 1 to 11, characterized in that the axes A and A 'of the neck (3) and the diaphyseal portion (8) form a cervico-diaphyseal angle a between 125 and 140.   13 - femoral implant according to one of claims 1 to 12, characterized in that the axes D and A 'of the metaphyseal part (8) and the diaphyseal part (9) form an angle (3 between 158 and 162 and preferably, 160.   14 - Femoral implant according to one of claims 1 to 13, characterized in that the sharp edges (21, 20, 22 and 23) have, in cross section, an angle radius of less than 0.8 mm and, preferably less than 0.6 mm.