FR2868688A1 - Femoral rod for hip prosthesis, has impaction lunula with opening having edge defined by spheroid that is generated by rotation of ellipse around one of transversal or longitudinal axes - Google Patents

Abstract

The rod has an impaction hole that is provided in the form of an impaction lunula (5) that is placed on a distal side (4) of a cervix (2) of the rod. The lunula has an opening (6) for the introduction of an impactor. The opening has an elongated shape and has an edge (7) which is defined by a spheroid that is generated by the rotation of an ellipse around one of transversal or longitudinal axes.

Description

2868688 IMPACTABLE FEMALE ROD FOR HIP PROSTHESIS

  The present invention relates to a femoral stem for total or partial prosthesis of the hip to be implanted in the medullary cavity of a femur with or without cement.

  More particularly, the invention relates to a femoral stem of the type comprising a directional impaction hole, in the form of a lunula made on the proximal face of the neck of the femoral stem.

  The purpose of this lunula is to provide a percussion seat produced by an impactor during the final establishment of the rod.

  In this way, it is possible to produce percussion on the impactor without risk of slipping it and this with some impact accuracy.

  Nevertheless, the presence of the impaction lunula has certain detrimental consequences on the mechanical strength of the prosthetic femoral stem at its neck, not so much by the absence of material caused by the realization of the lunula, but by the primers. cracking due to the presence of edges formed at the corners of the different flat or rounded surfaces defining said lunula.

  Indeed, in known manner, the lunula is defined by a curved bottom in the longitudinal direction of the rod itself delimited by two straight side walls parallel to each other, forming with the end edges of the lunula, a rectangle .

  It is understandable that the bottom being in the transverse direction, it forms with the straight walls, two angles generating two edges.

  The presence of these ridges has a certain number of disadvantages, the main one of which is to weaken and thus to risk a rupture of the neck of the stem because of the presence of double points or even triple points formed at the edges which generate constraints. and eventually cracking primers.

  The purpose of the present invention is precisely to make a lunette on a prosthetic femoral stem providing a harmonious distribution of constraints while allowing practitioners, during the intervention, to be able to take support in the lunula to involve a rotation on the rod.

  Also, the aim is to be able to support this lunula by exerting a vertical or slightly angular pressure fixed with a needle, the time of setting the cement.

  The present invention overcomes the aforementioned drawbacks, while achieving the objectives defined and concerns for this purpose, a femoral stem for total or partial hip prosthesis intended to be implanted in the medullary cavity of a femur, of the type comprising a lunette-shaped directional impaction hole made on the distal face of the neck, constituting the seat of percussion F, F 'produced by an impactor, characterized in that the impaction lunula has an opening for introducing the impactor, of elongated shape and whose bottom is defined by an ellipsoid of revolution generated by the rotation of an ellipse around one of its longitudinal axes X, X 'or transverse Y, Y'.

  Such a profile given to the lunula in both the longitudinal and transverse direction allows, according to the desired aim, to optimize the reduction of the stresses exerted on the neck of the rod in tension and / or in compression, thereby avoiding double points, or even points. triplets.

  Also, the advantage offered to practitioners with such a conformation of the lunula lies in the fact that it can exert forces on the stem by resting in its lunula in an anteroposterior sense and in an internal / external sense.

  The present invention also relates to the features which will emerge during the following description, which should be considered in isolation or in all their possible technical combinations.

  This description given by way of nonlimiting example, will better understand how the invention can be made with reference to the accompanying drawings in which: FIG. 1 represents a partial front view of a prosthetic femoral stem conforming to FIG. invention.

  FIG. 2 represents on a reduced scale a view from above of the distal face of the neck of the femoral stem represented in FIG.

  FIG. 3 is a cross-sectional view along line III, III of FIG. 2.

  FIG. 4 is a view in longitudinal section along the line IV, IV of FIG.

  The femoral stem 1 generally designated in the figures is intended to be implanted in the medullary cavity of a femur (not shown) for total or partial prosthesis of the hip.

  This femoral stem 1 comprises in known manner, a neck 2 at the end of which is formed a cone for receiving a spherical head.

  The distal face 4 of the neck 2 of the rod 1 comprises a directional impaction hole formed by a lunula 5 constituting the seat of percussion produced by an impactor, in a direction F, F 'variable both angularly in the longitudinal direction and transverse .

  According to the invention, the impaction lunula 5 shown in the figures has an opening 6 for introducing the impactor, of elongate shape, the bottom 7 of which is defined by a spherical ellipsoid 2868688 generated by the rotation of an ellipse around one of its longitudinal axes X, X 'or transverse Y, Y'.

  According to an alternative embodiment not shown, the impaction lunula 5 has an introduction opening 6 of the impactor, of elongated shape and whose bottom 7 is defined by a spherical segment generated by the rotation of a circle around one of its diametrical axes.

  According to an embodiment not shown, the opening 6 of the introduction of the impactor in the impaction lunula 5 is shaped itself ellipsoidal.

  Thus, not only the stresses generated by the double points and the triple points are removed, because the lunula has no junction edge between these different planes, but moreover, the practitioner will be able to impact at different angles in the longitudinal and transverse directions. by impactions respectivemenet F or F 'while maintaining the ability to bear on straight sidewalls 8a, 8b to guide the femoral stem during surgery.

  Also, the bottom 7 of the lunula 5 is pierced with a central blind hole 9 allowing the introduction of a tool forming a needle. (not shown) According to a preferred embodiment, shown in the figures, the bottom 7 of the lunula 35 5 is pierced with a threaded central hole 10 so as to allow the screwing of an extraction tool of said Femoral stem 1. (not shown) Of course, the two aforementioned features may be associated so that the central blind hole of the lunula is extended by a threaded hole also central smaller diameter.

Claims (1)

7 CLAIMS   1. Femoral stem for total or partial hip prosthesis intended to be implanted in the medullary cavity of a femur, of the type comprising a lunette shaped directional impaction hole (5) made on the distal face (4) of the cervix (2), constituting the percussion seat (F, F ') produced by an impactor, characterized in that the impaction lunula (5) has an opening (6) for introducing the impactor, of elongated shape and whose bottom (7) is defined by an ellipsoid of revolution generated by the rotation of an ellipse around one of its longitudinal axes (X, X ') or transverse (Y, Y').   2. Femoral stem for total or partial hip prosthesis for implantation in the medullary cavity of a femur, of the type having a lunula-shaped directional impaction hole (5) formed on the 20 (2), constituting the seat produced by an impactor the impaction horn (5) distal face (4) of the percussion neck (F, F ') characterized in that has an introduction opening (6) of the impactor, elongate and whose bottom (7) is defined by a spherical segment generated by the rotation of a circle around one of its diametral axes. 3. Femoral stem according to one of the   claims 1 or 2, characterized in that   the insertion opening (6) of the impactor 2868688 8 the impaction lunule (5) is shaped ellipsoidal itself.   4. femoral stem according to one of claims 1 to 3, characterized in that the bottom (7) of the lunula (5) is pierced with a central blind hole (9) for the introduction of a tool forming a needle.   5. femoral stem according to one of claims 1 to 4, characterized in that the bottom (7) of the lunula (5) is pierced with a threaded central hole (10) so as to allow the screwing of a tool extraction of said femoral stem (1).   6. femoral stem according to claims 4 and 5, characterized in that the central blind hole of the lunula is extended by a threaded hole also central smaller diameter.