FR2794642A1 - Extractor for Charnley-type hip prosthesis comprises locking assembly and impaction member - Google Patents

Abstract

The extractor consists of a locking assembly (5) which is fastened to the femoral shank (2) of the prosthesis, applying a first force (F1) along its lengthwise axis (Y) and a second force (F2) against its collar (4) at an angle to the first, and an impacter (6) in line with the shank's lengthwise axis. The impacter is connected to the first component (5a) of the locking assembly and allows a series of impacts to be applied to the shank to loosen it in the femoral canal and allow its extraction.

Description

<B> DEVICE </ B> DEVICE </ B> </ B> </ B> </ b> </ b> </ b> The present invention finds application in the field of total prostheses which concern the articulation hip.

As is known, total hip prostheses consist of an acetabular component and a femoral component. The femoral component is a stem that can be sealed in the femoral shaft.

Usually, after preparation of the femoral shaft, through reamers and graters, a rod is impacted. This stem can be sealed with a surgical or cementless acrylic cement. When the stem is cementless, it is made of a biocompatible alloy having a surface state that can promote bone regrowth.

If the total hip prostheses are in the majority of successes at the surgical level, it happens that the surgeon is obliged to make a recovery, when the femoral stem or the acetabulum is unsealed.

When the femoral stem is unsealed, recovery is relatively easy. Indeed, the surgeon proceeds as follows: it removes with a simple punch needle, the femoral stem of the femoral shaft, and this in a relatively easy way, because the femoral stem moves in the barrel due to loosening.

The operation is then to clean the femoral shaft and then dispose of a new prosthesis, in fact a new femoral stem.

On the other hand, in the case of an acetabulum loosening, the stem may have remained perfectly sealed in the femoral shaft, and have suffered damage, which nevertheless requires its extraction to replace it.

The extraction of a femoral stem having remained perfectly sealed can pose a major problem because in some patients, because of the acetabulum loosening or because of the physiological nature of the femur, it can be considerably weakened.

The extraction of the rod then becomes a very difficult operation, and several known impaction and extraction methods are then used.

A first method is to use small osteotomes that the surgeon slips between the femoral stem and the bone, which allows to release said rod in the proximal portion.

In this case, very often, when the bone of the femur is fragile, it is then necessary to shake the femoral stem, or via a needle extractor which is housed in a housing provided under the cervix. the femoral stem.

The risk is then significant to cause fractures in the femur.

On the other hand, when it is a prosthesis type Charnley, it is not possible to create the aforementioned housing by making a hole under the neck of the femoral stem, because the latter in this type of prosthesis very particular is of reduced dimensions.

This extraction mode is therefore not easily used in the case of a Charnley type prosthesis.

To better understand the problem, when it comes to extract the femoral stems of this type, it should be known that the latter have spherical heads intended to cooperate with a corresponding prosthetic acetabulum, which have a diameter of 22. , 2 mm. This leads to propose a neck of sufficiently small diameter to avoid any dislocation problems related to a cam effect between the acetabulum and the femoral stem.

This cam effect can be described as a conflict between the neck and the edge of the acetabulum. This conflict could have the effect of causing the output of the head of the rod relative to the acetabulum, which can pose major problems of performance of the implant.

This is why all these products have cones and necks with diameters of about 10 mm, and therefore it is not possible in this case to provide an extraction hole. As a result, the extraction mode just described is not applicable.

Another method is to use a clamp that comes to hang on the morse taper protruding from the femoral stem or on the head. Very often, this method can cause cracks in the femur, and fractures, because each time the shaking of the prosthesis is not done in its longitudinal axis.

A third known method is to make a threaded hole in the implant or femoral stem, to slide a rod with a sliding flyweight. It is then possible to be able to shake the femoral stem in the axis.

This extraction method is effective, however it is not used in Charnley type prostheses because, as already mentioned above, the realization of a threaded hole in the proximal portion of the femoral stem significantly weakens the prosthesis and can cause fracture risks.

The configuration of a femoral stem type Charnley therefore does not allow the realization of a threaded hole, but only a small impaction hole.

The problem is all the more acute as the prostheses of the charnley type do not comprise flanges that can possibly constitute a support The present invention aims to remedy all of the aforementioned drawbacks, and relates to this effect a device for extracting a femoral stem, in particular of the Charnley type, previously cemented inside a femoral shaft and having a spherical head, intended to cooperate with a prosthetic acetabulum of the hip and attached to a Morse taper made at the end of a neck of said femoral stem, intrinsically small diameter, and whose longitudinal axis is angularly offset from that of the femoral stem proper, characterized in that it is constituted - on the one hand by a locking assembly adapted to be secured to the femoral stem by exerting a first force against it in its longitudinal axis by a n first clamping means and a second force against the neck of said rod in the longitudinal axis thereof by a second clamping means forming with the first a triangulation via a connecting element forming a return angle whose apex is located substantially within the footprint of the stem and whose value is complementary to that of the angle formed by the neck with the femoral stem to obtain a flat angle substantially equal to 180, so as to locate the axis of the first clamping means in the axis of the femoral stem and cause jamming of the second relative to the angularly deported neck, and - on the other hand an impaction means (6) disposed in the longitudinal axis of the first clamping means of the locking assembly, merging with the longitudinal axis of the rod, and at the free end of which means is secured the compaction means, so as to constitute a line of action the along which repeated shocks are produced against said first clamping means and consequently against the femoral stem by repercussion, for the purpose of shaking it in the femoral shaft, in which it is sealed, for its extraction.

The advantage of such a device is to be able to be secured very closely to the femoral stem to extract without weakening it.

Such an extractor according to the invention thus allows, without particularly soliciting the femur, to extract a Charnley type prosthesis in the axis, by shaking said prosthesis without having to set up a particular extraction device on the stem properly said, such as an extraction hole that is not feasible on Charnley-type prosthesis collars, and which anyway remain an imperfect extraction mode because these threaded holes also weaken the prosthesis. On the other hand, such threaded holes are not necessarily accessible when the bone has pushed back inside the thread, which in these cases requires the presence of an additional hole.

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 non-limiting example, will better understand how the invention can be made with reference to the accompanying drawings in which Figure 1 is a front view of the assembly of a device for extracting a rod femoral, according to the invention, shown in place on a femoral stem to extract.

FIG. 2 is an exploded view of the elements of an extraction device according to FIG.

Figure 3 is a sectional view on an enlarged scale along the line III.III of Figure 1.

The extraction device 1 generally designated, is more particularly intended for a femoral stem 2 Charnley type that would have been previously cemented inside a femoral shaft (not shown).

A femoral stem 2 of this type has a spherical head (not shown) intended to cooperate with a prosthetic acetabulum (not shown) of the hip. The spherical head is attached to a Morse taper 4 made at the end of a neck 3 of the femoral stem 2.

In a femoral stem of the Charnley type, the neck 3 is intrinsically of small diameter, and does not have a collar.

The longitudinal axis x of the neck 3 is angularly offset at an angle α to the y axis of the femoral stem 2 itself.

According to the invention, the extraction device 1 is constituted on the one hand by a locking assembly 5 adapted to be secured to the femoral stem 2 by exerting a first force F1 against it in its longitudinal axis Y by a first 5A clamping means and a second force F2 against the neck 4 of said rod 2 in the longitudinal axis x thereof by a second clamping means 5B forming with the first 5A a triangulation through a member of link 5C forming a bevel gear whose vertex 0 lies substantially within the footprint of the rod 2 and whose value a2 is complementary to that of the angle α1 formed by the neck 3 with the femoral stem 2 to to obtain a flat angle a3 substantially equal to 180, so as to locate the Y axis of the first clamping means 5A in the Y axis of the femoral stem 2 and cause a jamming of the second 5B relative to the neck 3 angularly deported according to the x axis.

This is in fact to establish a balance of the clamping forces F1, F2 relative to the femoral stem 2 in order to obtain a compromise able to secure the locking assembly 5 with respect thereto.

The extraction device 1 further comprises an impaction means 6 disposed in the longitudinal axis Y 'of the first clamping means 5A of the locking assembly 1, coinciding with the longitudinal axis Y of the rod 2, and at the free end of which means 5A is secured the compaction means 6, so as to constitute a line of action AA 'along which are produced repeated shocks against said first clamping means 5A and consequently against the Femoral stem 2 by repercussion, in order to shake it in the femoral shaft, in which it is sealed, for its extraction.

According to the embodiment shown in the figures, the first clamping means 5A is constituted by a cylindrical sleeve 7 also acting as a manual gripping means, of which at least a part of its internal bore is threaded, and in which is susceptible to be actuated in rotation a clamping rod 8 also threaded intended to bear against a proximal zone 2a of the femoral stem 2.

Still according to this same embodiment, the second clamping means 5B is constituted by a second cylindrical sleeve 9 secured to the first 7 by means of the connecting element 5C forming an angle gear, and of which at least a part its upper internal bore 10 is threaded to receive a rotatable assembly 11 also threaded, having an external adjustment portion 11a by manual rotation drive and an inner portion 11b forming a morse taper for cooperating after adjustment with a corresponding conical end 4 of the collar 3 of the femoral stem 2 to extract.

Preferably, the Morse taper 11b of the second clamping means 5B is a piece attached to the end of a hollow adjusting screw 11c carrying at its other free end the external adjustment portion 11a, the connection between the Morse taper 11b and said external adjustment part 11a being effected by means of a longitudinal axis 11d of which an end head 11e abuts against a corresponding inner shoulder of the Morse taper 11b and whose other end 11f is secured to the outer part 11a through a transverse pin 11g through both the end 11f of the connecting shaft 11d and the external adjusting portion 11a. In this way the Morse taper 11b is in solid contact with the end 11h of the adjusting screw 11c to form therewith the rotary assembly 11, via the pin 11g and the longitudinal connection axis. 11d. In fact, the external adjustment portion 11a of the rotary assembly 11 is a knurled knob for rotating operation.

The clamping rod 8 cooperating with the sleeve 7 of the first clamping means 5A is constituted by a threaded rod comprising on the one hand a conical end zone 8a intended to bear in clamping in a corresponding cavity 12 made in the proximal zone. 2a of the femoral stem 2, and secondly at its other end a manual actuation button 8b.

Regarding the latter, it could be here also a knurled knob.

According to another characteristic of the invention, the manual actuating button 8b of the clamping rod 8 of the first clamping means 5A is pierced axially at its upper part by a threaded hole 8c intended to receive fixedly and in the longitudinal axis YY 'a threaded end 6e of the impaction means 6.

With regard to the impaction means 6 itself, it is constituted by a sliding rod 6a on which is disposed a sliding weight 13, captivated longitudinally between two stops 6b, 6c arranged on said rod 6a, so as to cause by manual actuation of the weight 13 upwards and downwards, axial shocks repeated against the stops 6b, 6c and consequently against the button 8b of the clamping rod 8 and against the femoral stem 2 by its end 8a, according to the action line AA 'coinciding with the longitudinal axes YY' of the femoral stem 2 and the first clamping means 5A.

The distance d between the two stops 6b, 6c of the slide rod 6a of the impaction means 6 corresponds to the maximum stroke of the weight 13.

 According to another characteristic of the invention, the sliding rod 6a of the impaction means 6 extends beyond its upper stop 6c by a longitudinal axial handle 6d constituting a gripping grip grasped by a hand of a surgeon while his other hand activates the weight 13, once the device 1 in place.

Claims (9)

<B> CLAIMS </ B> 1. Device for extracting a femoral stem (2) in particular of the Charnley type, previously cemented inside a femoral shaft and having a spherical head, intended to cooperate with a prosthetic acetabulum of the hip and attached to a Morse taper (4) made at the end of a neck (3) of said femoral stem (2), intrinsically of small diameter, and whose longitudinal axis (x) is angularly offset from that (y) of the femoral stem (2) proper, characterized in that it is constituted - on the one hand by a locking assembly (5) adapted to be secured to the femoral stem (2) by exerting a first force (F1) against it in its longitudinal axis (Y) by a first clamping means (5A) and a second force (F2) against the neck (4) of said rod (2) in the longitudinal axis (x) thereof by a second clamping means (5B) forming with the first (5A) a triangulation via a connecting element (5C) forming a bevel gear whose vertex (O) lies substantially within the footprint of the rod (2) and whose value (a2) is complementary to that of the angle (a) ) formed by the neck (3) with the femoral stem (2) to obtain a flat angle (a3) substantially equal to 180, so as to locate the axis Y 'of the first clamping means (5A), in the axis (Y) of the femoral stem (2) and cause jamming of the second (5B) relative to the neck (3) angularly deported along the x axis, and - on the other hand an impaction means (6) arranged in the longitudinal axis (Y ') of the first clamping means (5A) of the locking assembly (1), merging with the longitudinal axis (Y) of the rod (2), and at the end free of which means (5A) is secured the compaction means (6), so as to constitute a line of action (AA ') along which are produced repeated shocks against said first clamping means (5A) and consequently co between the femoral stem (2) by repercussion, in order to shake it in the femoral shaft, in which it is sealed, with a view to its extraction. 2. Device according to claim 1, characterized in that the first clamping means (5A) is constituted by a cylindrical sleeve (7) also acting as a manual gripping means, at least a portion of its internal bore is threaded, and in which is rotatably operable a clamping rod (8) also threaded intended to bear against a proximal zone (2a) of the femoral stem (2). 3. Device according to claim 1, characterized in that the second clamping means (5B) is constituted by a second cylindrical sleeve (9) secured to the first (7) via the connecting element (5C). forming at least one upper part of its internal bore (10) is threaded to receive a rotatable assembly (11) also threaded, having an external adjusting portion (11a) by manual rotation drive and a portion internal (11b) forming a Morse taper for cooperating after adjustment with a corresponding conical end (4) of the neck (3) of the femoral stem (2) to extract. 4. Device according to claim 3, characterized in that the Morse taper (11b) of the second clamping means (5B) is a piece attached to the end of a hollow adjusting screw (11c) carrying at its other free end the external adjustment part (11a), the connection between the Morse taper (11b) and said external adjustment part (11a) being effected by means of a longitudinal axis (11d) including an end head (11e) ) abuts against a corresponding inner shoulder of the Morse taper (11b) and whose other end (11f) is secured to the external adjustment portion (11a) via a transverse pin (11g) passing through the the end (11f) of the connecting pin (11d) and the external adjustment portion (11a), so that the Morse taper (11b) is in solid contact with the end (11h) of the screw (11c) for forming therewith the rotary assembly (11), via the pin (11g) and the longitudinal connection axis (11d). 5. Device according to one of claims 1 to 4, characterized in that the clamping rod (8) cooperating with the sleeve (7) of the first clamping means (5A) is constituted by a threaded rod comprising on the one hand a conical end zone (8a) intended to bear in clamping in a corresponding impression (12) made in the proximal zone (2a) of the femoral stem (2), and on the other hand at its other end a button of manual operation (8b). 6. Device according to claim 5, characterized in that the manual actuating button (8b) of the clamping rod (8) of the first clamping means (5A) is pierced axially at its upper part by a threaded hole (8c ) for receiving fixedly and in the longitudinal axis (YY ') a threaded end (6e) of the impaction means (6). 7. Device according to claim 6, characterized in that the impaction means (6) is constituted by a sliding rod (6a) on which is disposed a sliding weight (13) captivated longitudinally between two stops (6b, 6c). ) arranged on said rod (6a), so as to cause by manual actuation of the weight (13) upwards and downwards, repeated axial shocks against the stops (6b, 6c) and consequently against the button (8b) of the clamping rod (8) and against the femoral stem (2) at its end (8a), along the line of action (AA ') coinciding with the longitudinal axes (YY') of the femoral stem (2) and the first clamping means (5A). 8. Device according to claim 7, characterized in that the distance (d) between the two stops (6b, 6c) of the sliding rod (6a) of the impaction means (6), corresponds to the maximum stroke of the flyweight (13). 9. Device according to claim 7 or 8, characterized in that the sliding rod (6a) of the impaction means (6) extends beyond its upper stop (6c) by a longitudinal axial handle (6d) constituting grasping grasping grip of a surgeon's hand while his other hand activates the weight (13), once the device (1) in place.