FR2960418A1 - Glenoid assembly for shoulder prosthesis, has base plate provided with part for receiving anchoring rod and articulation element, where base plate is provided with another part with fixation arrangements in coracoid process - Google Patents

Abstract

The assembly has a base plate provided with a part (1a) for receiving an anchoring rod (2) and an articulation element (T) that cooperates with a complementary articulation element provided with a humeral implant. The base plate is provided with another part (1b) with fixation arrangements in coracoid process. The former part of the base plate is diametrically extended in circular shape in a plane. A bottom face of the former part is in convex shape corresponding to an anatomical profile of a coil.

Description

The invention relates to the technical sector of orthopedic implants, including shoulder prostheses.

In a manner well known to those skilled in the art, a shoulder joint prosthesis essentially comprises a humeral assembly and a glenoid assembly.

Different solutions have been proposed to achieve this type of articulation and that according to two large families. According to a first family, the humeral element fixed in the medullary canal of the humerus, has, directly or in a reported manner, a substantially hemispherical head adapted to cooperate with a glenoid implant fixed at the level of the anatomical glenoid of the scapula. According to a second family, with the particular aim of having a center of rotation of the humerus which is close to the glenoid, the principle of the articulation is reversed in that the hemispherical articulation head is fixed either at the level of the humeral stem, but at the level of the anatomical glenoid 20 to cooperate with a cup of complementary shape that has said rod. A joint prosthesis of this type can be illustrated, for example, by way of non-limiting indication, by the teaching of patent EP 1.064.890.

In the course of a revision or revision, sometimes problems may arise in attaching the glenoid implant to the remaining portions of the scapula. For example, in an attempt to solve this problem, a solution has been proposed in patent FR 2,902,993 which relates to a glenoid element comprising an anchor disc tail 10 formed from a proximal collar. The anchor disc tail has a helical shape and has, opposite its anchoring portion in the bone, a frustoconical bearing for fixing a hemispherical hinge head. The support flange has holes for engaging at least one screw to be inserted into the bone.

The problem to be solved by the invention is to improve the fixation of the glenoid implant in the case of certain traumatologies and / or when the glenoid has been weakened, which is all the more important in the case an inverted prosthesis where the anchors are much more stressed than in the case of a so-called conventional joint. Fixation problems may arise especially in case of osteoporosis or revision of a prosthesis. It is therefore important to be able to fix the glenoid implant in the intact or highly corticalized parts of the scapula.

To solve this fixing problem, particularly in the case of a revision, it has been designed and developed a glenoid assembly for a shoulder prosthesis, which comprises a base having a portion adapted to receive an anchor rod and an element. articulation member for cooperating with a complementary-shaped hinge member that has a humeral implant and a portion having fixation arrangements in the base of the coracoid process.

In order to solve the problem posed by being able to fix the glenoid implant at the level of the most strongly corticalized scapular regions, the portion able to receive the anchor rod and the articulation element is generally circular in shape while being extended diametrically, in the same plane, by an elongate and curved form constituting the part having the fixing arrangements.

Advantageously, the underside of the substantially circular portion is convex to correspond to the anatomical profile of the glenoid.

To solve the problem posed to ensure the primary fixation of the assembly, the center of the substantially circular portion has a threaded hole for screwing the anchor rod into the glenoid cavity, said rod having arrangements for mounting and fixing the hinge element.

According to another important feature of the invention and in order to solve the problem posed of possibly placing a bone graft in place, the circular part has, opposite and substantially in alignment with the elongate portion, an oriented heel adapted to cooperate with an area of the anatomic glenoid and act as a bone graft abutment.

In order to solve the problem of being able to fix the glenoid assembly, in particular at the level of the coracoid process, the fixing arrangements of the elongate part consist of several holes able to receive, in whole or in part, screws whose number and implantation depend on the nature of the area considered of the process.

In order to be able to adapt to different pathological cases, the elongated part has one or more breakable zones.

Still with the aim of improving the fastening of the assembly, the substantially circular portion has holes for the engagement of complementary anchoring screws.

As indicated, the invention finds a particularly advantageous application in the case of an inverted joint. For this purpose, the hinge member is constituted by a convex head of the hemispherical type adapted to cooperate with a bearing surface and sliding that has the humeral implant.

The invention is described below in more detail with the help of the figures of the accompanying drawings in which: - Figure 1 is a perspective view of the base; - Figure 2 is a perspective view of the anchor rod; - Figure 3 is a perspective view of the base after installation of the anchor rod and fixing screws; FIG. 4 is a perspective view of the base after placement of the articulation element, in the form of a hemispherical head; FIG. 5 is a schematic view showing an example of implantation of the glenoid assembly at the level of the scapula.

It is recalled that the invention relates more particularly to a glenoid assembly, in the case of a shoulder joint prosthesis, and more particularly in the case of a revision or revision. In addition, the glenoid assembly has, in a preferred manner which can not, however, be considered as strictly limiting, a hinge element in the form of a convex head of the hemispherical type (T) intended to be fixed at the level of the anatomical glenoid of the scapula under the conditions indicated in the following description and according to a characteristic of the invention.

In a known manner, this articulation (T) is capable of cooperating with a bearing and sliding surface, not shown, that has, directly or in a reported manner, a humeral element intended to be fixed by any known means. and appropriate in the humeral diaphysis.

According to the invention, the glenoid assembly comprises a base (1) having essentially two parts or areas (1a) and (1b). The portion (la) is adapted to receive an anchor rod (2) and the hinge member as such (T). Part (Ib) has fixing arrangements, particularly at the level of the coracoids process.

As shown in the figures of the drawings, the portion (la) has a generally circular general shape. This circular portion (la) is extended, diametrically and in the same plane, by an elongate shape to form the fixing portion (lb). The top face of the portion (la) is flat to receive support, as will be indicated in the following description, the hinge head (T). The underside of the portion (la) is convex, according to a radius of curvature substantially corresponding to the anatomical profile of the glenoid. The attachment portion (Ib) of flat section, is curved so as to correspond substantially to the anatomical shape of the base of the coracoid process.

The center of the portion (la) has a threaded hole (lai) for screwing the anchor rod (2) by means of a threaded bearing (2a). The distal end (2b) of the anchor rod (2) has recessed and raised areas to improve anchoring. Above the threaded portion (2a), the rod (2) has a frustoconical shoulder shoulder (2c) for the impaction of the hinge head (T). Note that this scope (2c) may have a threaded hole (2d) for the engagement of a fastening screw that has the hinge head (T) which bears against the top face of the part (la) of the base (1).

The rod (2) can be welded or monobloc with the base (1), in particular the part (la).

According to another important characteristic of the invention, the circular portion (1a) has, opposite to the elongate fixing portion (1b) and substantially in alignment with the latter, an oriented heel (1c). This heel (1c) is able to cooperate with an area of the anatomical glenoid and serves as a stop for a possible bone graft intended to fill the defect created during the removal of the glenoid implant during prosthetic revisions. As an indication, the heel (lc) is oriented relative to the plane defined by the portion (la), at an angle of about 120 ° and a sector of about 60 ° relative to the center of the hole (lai).

The elongated portion (Ib) has a plurality of holes (lbl) for engaging at least one screw (3). In a conventional manner, these holes (lbl) have a hemispherical bowl for the integration and, optionally, the orientation of the heads of the screw or screws (3). These provisions allow the operator to set, depending on the pathological case, one or more screws (3), according to different locations determined by the holes (lbl). Note that this part (lb) may have one or more breakable zones, in order to adapt its length to the pathological case encountered.

Still with the aim of improving the anchoring and fixing, the circular part (la) has at least one, but preferably several holes (1 a2) for the engagement of at least one anchoring screw ( 4).

The entire glenoid base (1) as described and illustrated is advantageously made of titanium, without excluding other materials.

The advantages are apparent from the description, in particular it is emphasized and recalls: the base has a general shape corresponding to that of the coracoids apophysis allowing many possibilities for the establishment of one or more screws; - The heel can serve as a stop and / or facilitate a bone graft and / or construction; the possibility of having a reduced section of the anchor rod at its distal portion by considering the fixation of the entire base, including at the level of the coracoid process; - the self-adaptation of the base to the different pathological cases.