FR2644690A1 - Femoral prosthesis having an anchoring system with screwed metaphysis and blocked diaphysis - Google Patents

Abstract

Femoral prosthesis having an anchoring system with screwed metaphysis and blocked diaphysis, characterised in that: a) the neck 2 ending in a truncated cone 3, forming a relatively trapezoidal part 1, receives the heads 4 of small diameter which are generally made of a ceramic compound or metal, b) the cervico-diaphysial angle is normally between 135 and 120 DEG , and c) the prosthetic shaft, which is to have a self-locking morphology and to exist in several sizes, comprises a metaphysial upper part 6b, a self-locking lower part 6a extended via a strictly conical zone 7 receiving the metaphysial bushing 9.

Description

We have known for a very long time, from systematic anatomatic studies of the human femur, that we can observe the following principles
a) the proximal part of the femur is bulky and perfectly rigid under a heavy load. The different horizontal sections revealed that the intramedullary part went in decreasing cone.

 b) the diaphyseal part of the upper third of the femur is elastic under a heavy load. The different horizontal sections revealed that the medullary part was in the shape of a very slight decreasing cone and sometimes cylindrical.

 These anatomical observations made, it appeared that this femoral area could present weaknesses especially in the elderly or after a violent shock and that it was therefore necessary to strengthen this area of the femur especially when the upper neck was broken or cracked.

 The present invention has therefore taken into account a bulky and conical proximal anchoring, then in the diaphyseal part of the upper femoral third, a flexible practically cylindrical anchoring.

 The use in current practice of screw-retained diaphyseal and locking prostheses further comprising a porous metaphyseal anchoring reveals over the course of experience the advantages and disadvantages of each of these solutions, which led to an attempt to assemble the two principles on the same prosthesis.

 It was found that, on screwed prostheses, the diaphyseal screwing over the entire length of the prosthesis could cause pain in the lower part of the tail of the prosthesis which severely affected the functional result of the operated patients.

Likewise, cortical screwing is not without drawbacks because it forces the femoral shaft to be cleared over a large area so as to place a very robust forceps thereon, which can cause fear of longitudinal fractures at the time of screwing.

 Self-locking prostheses with metaphyseal madreporic fixation have shown that, in many cases, the primary stability of the prosthesis may appear good but that as soon as the micromovements are loaded, this can be noted after a certain period of time. X-rays, are at the origin of the variation or the descent of the prosthesis. These phenomena can be accompanied by pain.

It was therefore decided to study and produce a prosthesis having the following two principles
a) anchor screwed only metaphyseal of which we know the solidity of the primary stability,
b) self-locking of the lower portion of the rod in the diaphysis.

According to the invention, the femoral prosthesis with a screwed metaphyseal anchoring system and blocked diaphyseal, is characterized in that
a) the neck ending in a Morse cone forming a relatively trapezoidal part reviews the small diameter heads which are generally made of a ceramic or metal compound,
b) the cervico-diaphyseal angle is normally between 135 and 1200, and
c) the prosthetic tail, which must have a self-locking morphology and exist in several sizes, comprises a metaphyseal upper part, a self-blocking lower part extended by a strictly conical zone receiving the metaphyseal sleeve.

 Various other characteristics of the invention will also emerge from the detailed description which follows.

 An embodiment of the object of the invention is shown, by way of nonlimiting example, in the accompanying drawings.

 Fig. 1 is a schematic elevation view, practically complete, of the new femoral prosthesis.

Fig. 2 shows, in side elevation, the conventional location of an independent conical metaphyseal screwed portion
Fig. 3 is a schematic side elevation showing different prosthetic tails corresponding to conventional sizes.

 Fig. 4 is a perspective view of the complete prosthesis.

 Fig. 5 is a section through the metaphyseal fixation cone.

 Fig. 6 shows the metaphyseal cone in place on the prosthesis which does not have in this figure the neck.

 In general and as shown in fig. 1, the prosthesis comprises a relatively trapezoidal part 1 consisting of a type 2 neck ending in a Morse cone 3 which receives heads 4 of variable diameter adapted to international standards, for example 22, 26, 28 or 32 mm.

 These femoral heads 4 are, in general, made of a cer ## e e or metal compound but can also be made of any other suitable material.

 As can be seen in fig. 1, the prosthesis in place has been shown diagrammatically in a femur F partially shown and having its original neck C. This has been previously cut so as to prepare the complete canal necessary for the introduction of the entire prosthesis .

 The cervico-diaphyseal angle indicated by lines C and D should normally be between 135 and 1200.

 In addition, the prosthetic tail 6 must, on the one hand, have a self-locking morphology and, on the other hand, exist in several sizes so that it can adapt to different diaphyses both in diameter and in length. (see what is shown diagrammatically in fig. 3).

 We immediately notice that this prosthetic tail 6 is in one piece with the neck 2 and therefore has two separate portions, a lower portion 6a of the self-locking type, and a lower area 7. The lower portion 6a corresponds to conventional sizes such as 7.5, 10 , 12.5, 15 cm.

 It is located below the portion described as metaphyseal 6b and should be approximately 11.5 cm in length, except for size 7.5 where it seems that a length of 11.5 cm is sufficient.

 Zone 7, placed below this lower zone 6a, is strictly conical and corresponds to the four sizes mentioned above and is 5.5 cm. This zone is intended to receive the independent conical screwed portion which will be described in a specific manner. An anti-rotation stud 8 is placed under the underside of the neck in order to penetrate the metaphyseal screw cone 9 to obtain an anti-version of the prosthetic assembly.

 The fixing cone or metaphyseal sleeve 9 is in the form of a cone extending the self-locking design of the lower portion 6a of the tail having a thread pitch of 3 mm deep by 5 mm wide. This screwed cone 9 is hollow and intended to receive the conical portion 7 of the tail of the prosthesis. This is therefore introduced into the cone screwed in force into the bone (see fig. 2).

 It should be noted that the outer periphery of the fixing cone 9 is grooved by parallel grooves 9a of substantially equal depth.

 In addition, the metaphyseal screw cone 9 comprises, at the upper part (support zone of the prosthetic tail 6), a series of radiating notches 10 separated from each other every 3 to 50 to allow the screwing of setting position as well as the pre-version positioning of the prosthetic assembly.

Claims (5)

 1 - Femoral prosthesis with screwed metaphyseal anchoring system and blocked diaphyseal, characterized in that  a) the neck (2) ending in a morse cone (3) forming a relatively trapezoidal part (1) receives the heads (4) of small diameter which are, in general, made of a ceramic or metal compound,  b) the cervico-diaphyseal angle is normally between 135 and 120 0, and  c) the prosthetic tail, which must have a self-locking morphology and exist in several sizes, comprises a metaphyseal upper part (6b), a self-blocking lower part (6a) extended by a strictly conical zone (7) receiving the metaphyseal sleeve (9).  2 - Prosthesis according to claim 1, characterized in that the fixing cone or metaphyseal sleeve (9) has at its upper part a series of radiating notches (10) intended to cooperate with an anti-rotation stud (8) thus giving positioning ante-version of the prosthetic assembly.  3 - Prosthesis according to claims 1 and 2, characterized in that the radiating notches (10) are arranged every 3 to 50 approximately.  4 - Prosthesis according to claims 1 to 3, characterized in that the different parts of the prosthesis are generally made of metal compatible with the environment, in particular the bones.  5 - Prosthesis according to one of claims 1 to 4, characterized in that the prosthesis is adapted to international standards.