FR2880257A1 - Tools for hip prosthesis femoral stem, comprises tracer having femoral stem, cone for fixing spherical head, reference line, and grater with fixing tip and positioning stem, and impactor has support point and U-shape positioning stem - Google Patents

Abstract

The pointing end is superimposed with a point of the reference line (3a, 3b, 3c). The support point allows the depression of the femoral stem (30a, 30b, 30c). The reference line has a radius of curvature equal to the length of the positioning stem, which is mobile in rotation. The fixing tip comprises tightening means activated by a lever attached to an order handle. The stems comprise an end, which is inserted in an opening in the grater and impactor.

Description

The present invention relates to a set of tools for laying

  of a femoral stem of hip prosthesis.

  Hip prosthesis is a surgical procedure to replace, partially or totally, a damaged hip joint resulting from osteoarthritis or a fracture, for example.

  A total hip prosthesis is divided into three parts: a head, intended to replace the head of the femur; a femoral stem, intended to be inserted and fixed in the central shaft of the femur or medullary canal and on which the head will be fixed; an acetabulum or acetabulum, implanted at the level of the pelvis whose anatomical orientation it reproduces to replace the articular part and which will receive the head of the prosthesis.

  In order to better reconstruct the patient's joint, the surgeon will have to estimate the depth at which he must fix the femoral stem in the medullary canal so that the patient finds two legs of equal length. To do this, this surgeon helps with anatomical landmarks on the leg. These landmarks are difficult to find and generally very inaccurate. This is particularly true in the case of pertrochanteric fractures or large smashing of the upper femur, since the joint is completely destroyed and therefore does not provide these markers. In addition, the leg being detached from the pelvis, the relative positions of these marks may change during the intervention.

  The purpose of the present invention is to remedy the drawbacks mentioned above, and for this purpose consists of a set of tools for the placement of a femoral stem of a hip prosthesis, characterized in that it comprises: a layer comprising a representation a femoral stem adapted to the patient, having a head, and on which is marked a reference line passing through a point situated at a predetermined distance from said head, - a rasp holder having a fixing end for receiving a rasp and equipped with a positioning rod having a pointing end, said positioning rod being designed so that its pointing end is superimposed with a point of the reference line, once the rasp holder is correctly positioned, an impactor having a fulcrum for allowing the sinking of the femoral stem, the impactor being equipped with a positioning rod having a pointing end, said positioning rod being designed so that its pointing end is superimposed with a point of the reference line, once the femoral stem is correctly positioned.

  Thus, thanks to the reference line materialized on the representation of the adapted femoral stem, it is possible, from the correct positioning of the model on the healthy leg of a radiograph of the patient's pelvis, to mark a point of reference at the level of the patient. from the intersection of the reference line with the leg bone. The symmetrical application of the layer on the deteriorated articulation makes it possible to postpone this reference point on the leg to be operated. Since the rasp holder and the impactor are each equipped with a positioning rod designed to integrate the parameter that constitutes the predetermined distance, it is then possible to know precisely where the reference point will be once the two assembled members. By placing the pointing ends at the landmark, the positioning of the instruments, and thus the depression of the rasp holder and that of the femoral stem by the impactor, are assured. It should be understood that the value of the predetermined distance is not significant in itself, the important thing being that the same distance is used in the design of the three tools. Moreover, it should be understood that, for practical reasons, the layer may include several representations of femoral stem models so as to easily allow the determination of the most appropriate representation which will be the only representation used thereafter. Each representation then has its own reference line with the characteristics defined above.

  Advantageously, the reference line has a radius of curvature substantially equal to the length of the positioning rod of the rasp holder. Thus, the margin of error due to the thickness of the bone is reduced compared to a straight line of reference.

  Preferably, the positioning rod of the rasp holder is rotatable. Thus, its pointing end will be closest to the bone, thus further reducing registration and positioning inaccuracies with respect to the reference point.

  Advantageously, the attachment end of the rasp holder has retaining means which can alternatively pass from an engagement position to a retracted position. In its engagement position, the rasp is fixed in the attachment end, the passage in the retracted position to detach it to possibly change.

  Preferably, the fixing means comprise clamping means actuated by a lever attached to a control handle.

  According to one embodiment, the positioning rod of the rasp holder is U-shaped, and has an end intended to be inserted into a hole in the rasp holder.

  In the same way, the positioning rod of the impactor is preferably U-shaped, and has an end intended to be inserted into an orifice arranged in the impactor.

  The invention will be better understood with the aid of the detailed description which is set out below with reference to the appended drawing in which: FIG. 1 is a diagrammatic representation of a set of layers belonging to a set of tools according to FIG. 'invention.

  Figure 2 is a schematic representation of a rasp holder belonging to a set of tools according to the invention.

  Figure 3 is a schematic representation of an impactor belonging to a set of tools according to the invention.

  Figure 4 is a representation of a destroyed femur no longer ensuring the articulation between a leg and the pelvis.

  Figure 5 is a representation of a layer according to the invention used on a radiograph of the patient's pelvis to mark a landmark on the leg.

  Figure 6 is a representation of a rasp inserted into the medullary canal by means of a rasp holder according to the invention.

  Figure 7 is a representation of the rasp of Figure 6 correctly positioned.

  Figure 8 is a representation of a femoral stem inserted into the medullary canal by means of an impactor according to the invention.

  Figure 9 is a representation of the pelvis and legs of the patient, once the operation is completed.

  A set of tools according to the invention comprises a set of transparent layers 1, a rasp holder 10 and an impactor 20 intended to be used for the installation of a femoral stem 30 having a cone 31 for mounting a head.

  As shown in FIG. 1, each layer 1 comprises two sets A, B of three representations 30a, 30b, 30c of model femoral stems corresponding to the lengths of femoral stems 30 available for a cone 31 of given size. Each representation of a femoral stem 30a, 30b, 30c comprises a connecting cone portion 31a, 31b, 31c on which is intended to be connected a spherical femoral head.

  Moreover, each layer 1 is intended to be superimposed on a radiograph 50 of the patient's pelvis and the scaling ratio of the radiographic apparatus is taken into account. Consequently, several layers 1 are provided adapted to the different possible scale ratios. In the present case, the set A comprises three representations of model femoral stems having a smaller head than those of the set B, and is therefore intended to be used for a radiography performed with a smaller scale.

  On each representation 30a, 30b, 30c is materialized a reference line 3a, 3b, 3c. This reference line is made to pass through a point R located on the longitudinal axis of the cone 31, 31b, 31c at a predetermined distance d from the latter, after application of the scale ratio with respect to the original rod 30 . Furthermore, this reference line 3a, 3b, 3c has a determined radius of curvature adapted to the other tools in the set.

  The rasp holder 10, shown in Figure 2, comprises a body having a handle 12 and terminated by attachment end 13 having clamping means (not visible) actuated by a lever attached to a control handle 14. In addition, this rasp holder 10 is equipped with a U-shaped positioning rod 15 having a bent first end 16, by which it is fixed to the rasp holder 10 and a bent second end forming a pointing end 17. The first end 16 is fixed on the shaft 12 in a rotational manner and so that its pointing end 17 is able to be superimposed with a point of the reference line 3a, 3b, 3c. The radius of curvature of the reference line is determined so as to be substantially equal to the length of the positioning rod 15 so that the rotation of said rod around its first end substantially describes the reference line 3a, 3b , 3c.

  Finally, the impactor 20, shown in Figure 3, comprises a body having a handle 21 and a bearing point 22. This impactor 20 is also equipped with a U-shaped positioning rod 23, similar to the positioning rod 15, having a first end 24 bent by which it is fixed to the impactor and a second curved end forming a pointing end 25. The first end 24 is fixed on the handle 21 of the impactor so that that when the fulcrum 22 presses the femoral prosthesis, the pointing end 25 is superimposed with a point of the reference line 3a, 3b, 3c.

  A surgeon wishing to use the tools according to the invention to perform the placement of a femoral stem 30 in a patient whose leg 32a is no longer articulated with an acetabular cavity 33 of the pelvis 34 due to destruction of the head of the femur 40 as shown in Figure 4, proceed as follows.

  First of all it is necessary to perform a radiography 50 of the patient's pelvis. A layer 1 adapted to the scale ratio of the radiograph 50 taken is then superimposed on the latter, correctly positioning each representation of the cones 31a, 31b, 31c at the acetabulum of the healthy leg 32b, and the representation 30a, 30b, 30c of the most suitable femoral stem 30 is chosen. As shown in FIG. 5, the representation 30b is chosen to be the most suitable.

  The reference line 3b, present on the representation 30b retained, is then used to determine, on the layer 1, a first reference point P located at the intersection between the reference line 3b and the healthy leg 32b. An estimate of the distance from the point P is made with respect to an anatomical landmark, which may be the top of the greater trochanter. This distance is then postponed during the intervention on the damaged leg in order to materialize the point P '.

  During the operation, the surgeon first performs the installation of a definitive acetabulum 36 according to his appropriate surgical technique and can move the damaged leg 32a of the patient.

  The second step, shown in FIG. 6, of the operation consists in digging the medullary canal to allow the femoral stem 30 to be housed therein. To do this, the surgeon connects the head 37 of a rasp 38 to the mouthpiece The rasp 38 is then inserted into the medullary canal until the pointing end 17 of the rasp holder 10 is at the second reference point P '. The surgeon then knows that the depression of the rasp 38 corresponds to what is necessary for the femoral stem 30 to be positioned as determined on the healthy leg by means of its representation 30b.

  The rasp 38 is then disconnected from its rasp holder and a series of test collars 39 are tested, as shown in FIG. 7, to determine the neck 39 adapted to both the acetabulum 36 and the selected femoral stem 30.

  The femoral stem 30 is presented in the femoral shaft previously dug by the rasp 38 with the interposition of cement. The impactor 20 makes it possible to finalize the impaction and the orientation of this femoral stem 30. This step is represented in FIG. 8. When the pointing end 25 of the positioning rod 23 is at the level of the second point of P 'mark, this means that the femoral stem 30 is positioned as initially determined on the healthy leg by means of its representation 30b. A definitive spherical head 39 is fixed on the cone 31 of the femoral stem 30 and then inserted into the acetabulum 36. The femoral stem 30 having been positioned with reference to the healthy leg, the leg 32a is thus in a configuration very close to its configuration before fracture once reconnected to the pelvis 34, which ensures a length of the leg 32a identical to the length of the healthy leg, as shown in Figure 9.

  Although used in combination, it should be clear that the present invention also aims to protect the layer, the rasp holder and the impactor itself.

  Although the invention has been described in connection with particular embodiments, it is obvious that it is not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention. In particular, the layers can include a different number of representations than those indicated above.

Claims (7)

  1. Set of tools for positioning a femoral stem (30) of a hip prosthesis, characterized in that it comprises: a layer (1) comprising a representation of a femoral stem (30a, 30b, 30c ) adapted to the patient, having a cone (31a, 31b, 31c) for attaching a spherical head, and on which is shown a reference line (3a, 3b, 3c) passing through a point at a predetermined distance from said head, a rasp holder (10) having a fastener (13) for receiving a rasp (38) and equipped with a positioning rod (15) having a pointing end (17), said positioning rod being designed so that its pointing end is superimposed with a point of the reference line, once the rasp holder is correctly positioned, - an impactor (20) having a fulcrum (21) intended to allow the 'depression of the femoral stem, this impactor being equipped with a positio rod member (23) having a pointing end (25), said positioning pin being designed so that its pointing end is superimposed with a point of the reference line, once the femoral stem is correctly positioned.   2. Tool set according to claim 1, characterized in that the reference line (3a, 3b, 3c) has a radius of curvature substantially equal to the length of the positioning rod (15) of the rasp holder (10). ).   3. Set of tools according to any one of claims 1 or 2, characterized in that the positioning rod (15) of the rasp holder (10) is rotatable.   4. Tool assembly according to any one of claims 1 to 3, characterized in that the attachment end (13) of the rasp holder (10) has retaining means that can pass alternately from a position of commitment to a withdrawal position.   5. Set of tools according to claim 4, characterized in that the fastening means of the rasp holder (10) comprises clamping means actuated by a lever attached to a control handle (14).   Tool set according to one of Claims 1 to 5, characterized in that the positioning rod (15) of the rasp holder (10) is U-shaped and has an end (16) for be inserted into a hole in the rasp holder.   Tool set according to one of Claims 1 to 6, characterized in that the positioning rod (23) of the impactor (20) is U-shaped and has an end (14) for be inserted into a hole in the impactor.