Aid for positioning an ulnar and/or radial component of an elbow prosthesis

ES 2 265 027 T3

DESCRIPTION

Ancillary for placement of an ulnar component and / or a radial component of an elbow prosthesis.

The present invention relates to an ancillary for placement of an ulnar component and / or a radial component of a total or partial elbow prosthesis.

An elbow prosthesis, such as that known from EP-A-1 051 954, comprises an ulnar component and a radial component that must reproduce the ulnar and radial articular surfaces. The positioning of these surfaces with respect to the joint, very particularly with respect to the humeral trochlea, is essential for a good function of the prosthetic elbow.

To date, surgeons implant the ulnar and radial components of the elbow prosthesis after having dislocated the joint and attempting to reproduce the anatomical configuration of the articular surfaces. It happens that this reproduction is not perfect, resulting in poor cooperation of the ulnar and / or radial articular surfaces with the humeral trochlea. This leads to premature wear of these surfaces and discomfort for patients.

On the other hand, it is known from document US-A-4 718 414, which serves as the basis for the preamble of claim 1, or from document EP-A-0 132 284 to use a cutting guide with a view to placing a prosthesis shoulder. Such a guide induces a sometimes imprecise positioning of the cuts, which also implies an imperfect reproduction of the anatomical configuration of the articular surfaces.

It is these drawbacks that the invention aims more particularly to avoid by proposing a positioning ancillary that allows precise positioning of the ulnar component and / or the radial component with respect to the humeral trochlea, which substantially improves the operating conditions of the prosthetic elbow.

In this essentiality, the invention relates to an ancillary for the placement of an ulnar component and / or a radial component of a total or partial elbow prosthesis that comprises an ulna and / or radius cutting guide, this guide being intended to be positioned with respect to a phantom humeral trochlea also belonging to said ancillary and representative of the anatomical humeral trochlea, when the phantom trochlea is positioned with respect to the corresponding ulnar and / or radial articular surfaces. This guide is also suitable to be positioned with respect to the ulna and / or radius when the phantom trochlea is positioned with respect to its articular surface (s).

Thanks to the invention, the guide allows the surgeon to reference the resection areas of the bone or bones taking into account the real volume of the trochlea. In other words, the cutting guide functions as a three-dimensional anatomical probe of the trochlea surface, which allows an efficient positioning of the cutting areas with respect to this trochlea.

According to advantageous but not mandatory aspects of the invention, the ancillary incorporates one or more of the following characteristics:

- The guide comprises a support on which the phantom trochlea can be mounted and on which are mounted screws suitable for resting against the ulna and / or the radius for immobilization of the guide with respect to these bones.

- The aforementioned support comprises a leg whose end constitutes a guiding element for a cutting tool at the upper end of the spoke. This guide element may comprise a sliding groove for a resection blade at the upper end of the radius.

- The aforementioned support constitutes a cylindrical guiding element of a bell saw for the preparation of the upper end of the ulna.

- The aforementioned support comprises a leg that supports a shaft on which the phantom trochlea can be mounted. In this case, the cylindrical guiding element of the bell saw and the shaft on which the phantom trochlea can be mounted advantageously have confused axes of symmetry, the aforementioned shaft being hollow and forming a sliding and guiding volume of a central axis of the bell saw.

- The aforementioned support is extended by a stem capable of being positioned, over most of its length, parallel to the patient's forearm. This stem allows the surgeon to quickly preposition the support before a final adjustment obtained thanks to the aforementioned screws.

- The support is constituted by the assembly of several pieces selected according to the size of the phantom trochlea. In other words, the geometry of the support depends on the size of the phantom trochlea, that is actually the size of the anatomical trochlea of ​​which the phantom trochlea is a three-dimensional representation. This adaptation to the size of the anatomical trochlea allows a corresponding adaptation of the ulnar and radial cut zones.

- A guiding tool is provided for drilling the ulna, this tool comprising a template suitable for resting against the cut-out surface of the olecranon, this template being provided with a guide perforation for a drill or similar, while the template is integral with a handle for adjusting its angular position with respect to a central axis of the cut-out surface.

The invention allows the placement of an ulnar component or a radial component of an elbow prosthesis according to a procedure comprising steps consisting of positioning a cutting guide with respect to a phantom humeral trochlea representative of the anatomical humeral trochlea, when the

ES 2 265 027 T3 phantom trochlea is arranged with respect to the corresponding ulnar and / or radial articular surfaces, in immobilizing this guide with respect to the ulna and / or radius and in cutting the upper ulnar and / or radial ends, depending on the profiles defined by this guide.

It is also possible to provide that the ulna is cut into a surface inscribed in a cylinder and centered on a geometric axis of the external surface of the phantom trochlea. In this case, the phantom trochlea is advantageously held in position relative to the ulna during its trimming, its trimming taking place, in part at least, around this phantom trochlea.

Furthermore, cutting the ulna can be carried out by means of a bell saw guided in an element provided with a guide ring coaxial with the phantom trochlea.

Finally, according to an advantageous aspect of this procedure, the immobilization of the guide with respect to the ulna takes place thanks to three screws that pass through a guide support and that rest respectively on the olecranon, on the posterior plane triangle and on the lateral plane of the ulna.

The invention will become more apparent and other advantages thereof will appear more clearly in the light of the following description of an embodiment of an ancillary according to its principle and its method of use, given solely by way of example and with reference to the attached plans, in which:

FIG. 1 is a perspective view of an ancillary according to the invention, when a first stage of use takes place, the ulna and the radius being represented in thin lines for the sake of clarity of the drawing;

figure 2 is a perspective view of the ancillary of figure 1, when a second stage of use takes place;

FIG. 3 is a view similar to FIG. 1 when a third stage of use takes place;

figure 4 is a partial section of principle according to line IV-IV in figure 3;

Figure 5 is a perspective view of the upper ends of the radius and the ulna, when a fourth stage of use takes place; Y

FIG. 6 is a view analogous to FIG. 5 when prosthetic components are placed on the ulna and on the radius.

The ancillary 10 according to the invention is intended to be immobilized with respect to the ulna C and the radius R of an elbow joint to be equipped with an ulnar prosthetic component and / or with a radial prosthetic component.

This ancillary comprises several phantoms of humeral joint assemblages 20i, 20₂ and 20₃ which are called “phantom humeral trochlea” for simplicity and which the surgeon can successively compare with the corresponding anatomical trochlea of ​​the humerus or install in the sigmoid socket of the ulna. Obviously, the number of phantom trochlea is not limited to three and depends on the precision sought when this comparison takes place.

Trochlea 20₁, 20₂, 20₃ They are of symmetry of revolution and each one is provided with a central perforation 21 that allows its mounting on a support 31 that constitutes the reinforcement of a cutting guide 30 belonging to the ancillary 10.

The support 31 is constituted by the mechanical assembly of several metal parts. More precisely, the support 31 comprises a U-shaped stirrup 32 on which is mounted a hollow shaft 33 which can be inserted into the bore 21 of the selected phantom trochlea.

Next, the trochlea 20 is assumed₂ it has been selected for comparison with the anatomical trochlea.

This trochlea is then supported against the internal surface S_c olecranon and articular surface S_R of the radial head, in a position close to that of the anatomical trochlea before elbow dislocation.

The shaft 33 is mounted on a first branch 34 of the stirrup 32. The second branch 35 of the stirrup 32 is terminated by a ring 36 whose width is indicated T₃₆. The ring 36 and the hollow shaft 33 are coaxial and are centered on an axis XX 'which is also the axis of symmetry of the phantom trochlea 202 mounted on the support 31.

The support 31 also comprises a leg 37 immobilized on the support 31 and comprising two branches 37a and 37b that are generally perpendicular to one another, the branch 37b comprising, at its free end, a guide 37c that defines a generally parallel groove 37d to the X-X 'axis.

The stirrup 32 also supports a second leg fixed on the stirrup 31 and comprising two branches 38a and 38b that are globally perpendicular, one with respect to the other. The branch 38b is equipped with a carriage 39 integral with a rod 40, the carriage being able to slide with respect to the branch 38b as represented by the double arrow F₁ in figure 1.

The branch 38a is provided with a protrusion 38c in which a threading is made for receiving a screw 41 intended to bear against the proximal part of the olecranon.

Carriage 39 is, as regards itself, equipped with a screw 42 intended to bear against the posterior flat triangle of the ulna.

Lastly, the ring 36 is provided with an extension 36a into which a screw 43 is threaded intended to bear against the lateral plane of the ulna.

Cutting guide 30 is positioned relative to ulna C and radius R by arranging stem 40 globally along the patient's forearm and then roughly threading screws 41 to 43 so that phantom trochlea 202 is positioned with relative to the ulnar Sc and radial SR articular surfaces in substantially the same way as the anatomical trochlea when the elbow is not dislocated. When this position is reached, the screws 41 to 43 are tightened, so that the guide 30 is immobilized with respect to the ulna, and therefore with respect to the radius.

In this position and as shown in figure 2, it is possible to insert a sheet 50 in the slot 37d so that it cuts the upper end of the radius R. The position of the cut line of the radius R is determined taking into account the height of the radial button that will be subsequently placed on the spoke. This makes it possible to guarantee that the articular surface of this radial button will be correctly positioned with respect to the trochlea with which it will cooperate.

In Figure 2, arrows F2 and F3 represent the insertion and reciprocating directions of the sheet 50 with a view to cutting out the radius R.

As appears more particularly from Figures 3 and 4, it is then possible to insert a saw

ES 2 265 027 T3 of bell 60 in ring 36, parallel to axis XX 'and as presented by arrow F₄. The bell saw 60 is equipped with a central guide finger 61 aligned on the axis XX 'and the diameter of which allows it to penetrate into the inner volume 33a of the shaft 33, which allows effectively guiding the bell saw 60 in cooperation with the surface. internal support of the ring 36 that extends over its width €₃₆.

The bell saw makes it possible to cut the olecranon of the ulna C around the phantom trochlea creating a part of a cylindrical surface with a circular base S, more particularly visible in figure 5.

When the radius and ulna have been trimmed, cutting guide 30 is removed by loosening screws 41-43 and the bones can be prepared for receiving prosthetic components.

A perforation R, of the radius R is carried out substantially along the axis of the neck of the radius, while a guide tool 70 is used to determine the direction of a perforation C, to be carried out in the ulna to receive the anchor tail 101 of a ulnar prosthetic component 100. The tool 70 comprises a template 71 provided with a bore 72 for receiving and guiding a bore 73, with a punch or an adapted cutting tool. The outer surface 74 of the template 71 is a section of cylindrical surface of the same radius as the surface S and the template 71 can pivot around the axis XX 'which is the axis of symmetry of the surface S.

To control the angular positioning of the template 71 with respect to the axis X-X ', that is to say the direction of the perforation 72 with respect to the ulna C, the template 71 is attached by a handle 75 to a handle 76 intended to be grasped by the surgeon or one of his assistants and that allows to exert a tilting effort F₅ template 71 around the X-X 'axis.

It is understood that when the template 71 is in contact with the surface S, it is possible to create the hole C, by introducing the hole 73 into the bone through the hole 72, as schematically represented by the arrow F₆.

When the perforations C j and R have been made, the ulnar component 100 can be placed by inserting its anchor tail 101 in the perforation Ci, while a radial button 110 can be placed on the radius R by inserting its anchor tail 111 in the perforation R ,.

Thanks to the invention, it is possible to correctly position the components 100 and 110 taking into account the combined anatomy of the ulna, the radius and the humerus since, in the configuration of figure 1 that determines the positioning of the guide 30 and the zones cut, the phantom trochlea is supported on the anatomical articular surfaces of the ulna and radius. The result is a precise positioning of these components, with a good balance of ligaments of the joint.

The invention has been described when the placement of an ulnar component and a radial button takes place, but it can obviously be used for the placement of only one of these components.

The invention has been described for use through a lateral access route, in particular for an access of the bell saw 60 on the lateral side of the joint. Obviously, a medial access route can be used, with an ancillary designed symmetrically with respect to the one represented in the figures.