FR2997290A1 - Humeral implant for prosthesis of reverse shoulder joint of patient, has plate comprising anchoring rod with reduced height and engaged on metaphyseal part of humeral channel and humerus, where rod has openings to facilitate bone ingrowth - Google Patents

Abstract

The implant has a plate (1) whose circular edge (1f) retains an insert co-acting with a hemispherical cup fixed in a glenoid cavity. The plate has a hollow anchoring rod (1a) with reduced height ranging about 10 to 20 mm, preferably 15 mm. The plate is engaged on a metaphyseal part of a humeral channel and humerus. The rod comprises peripheral openings (1c) to facilitate bone ingrowth. The circular edge comprises edge arrangements i.e. recessed notches (1f1, 1f2), co-acting with arrangements complementary to the insert to ensure angular indexing of the insert.

Description

The invention relates to the technical sector of orthopedic implants, including total shoulder prostheses. In general, a shoulder joint prosthesis comprises a humeral implant and a glenoid implant. Thus, the humeral implant is fixed in the medullary canal of the humerus being able to cooperate with the glenoid implant fixed at the level of the anatomical glenoid of the scapula.

Most often, the humeral implant has a hemispherical hinge head that is attached to an anchor rod engaged in the humeral shaft. This articulation head cooperates with the glenoid implant, for example, in the form of a platinum cup fixed at the level of the anatomic glenoid. In the field of shoulder joint prostheses, it has also been proposed, in order to have a perfect humerus / glenoid congruence, and to improve the function of the deltoid to compensate for the absence or deficiency of the rotator cuff. to reverse the principle of articulation in the sense that the hinge head as such is fixed, no longer at the level of the humerus, but at the level of the glenoid to cooperate with a cup of complementary shape which it is fixed at the level of the humerus. This mechanical principle of inversion is particularly well suited for the treatment of glenohumeral arthropathies with insufficient or destroyed caps. This type of inverted shoulder prosthesis is apparent, for example, from the teaching of patent FR 2,618,065.

The patent FR 2,795,304 also describes a prosthetic assembly of inverted articulation of the shoulder comprising a glenoid element in the form of a convex hinge head of the hemispherical type having fastening arrangements at the level of the glene of the scapula . The hinge head cooperates with a bearing surface and sliding fixed on the rod anchored in the humeral shaft. Whatever the solutions chosen in this type of inverted joint prosthesis, it appears that the cup or platinum attached to the humerus, is always by means of a rod housed in the diaphysis of the humerus. Indeed, it is generally accepted that this humeral stem is necessary considering that in the case of an inverted joint prosthesis, the stresses at the platinum or the humeral insert are important. The establishment of this humeral stem requires the use of a rasp that will indirectly dictate the cervico-diaphyseal angle resulting from the cutting of the head of the humerus.

The object of the invention is to remedy these disadvantages in a simple, safe, effective and rational manner. The problem to be solved by the invention is to no longer use a humeral stem in the case of an inverted joint prosthesis which goes against the existing solutions as indicated above. To solve such a problem, the humeral implant for an inverted shoulder joint prosthesis comprising, in known manner, a plate receiving an insert intended to cooperate with a hemispherical head fixed in a glenoid cavity is remarkable in that the plate has a range. anchoring reduced height and able to be engaged only at the metaphyseal portion of the humeral canal and more generally of the humerus. This absence of stem therefore avoids the use of rasp for implant placement, gives the practitioner greater freedom for the angular orientation of the platinum at the cervico diaphyseal angle and thus preserves the bone capital of the patient. Advantageously, the height of the anchoring surface is composed between 10 and 20 mm and is advantageously 15 mm. According to another characteristic, the scope is hollow and has peripherally openings to facilitate bone regrowth. To solve the problem of ensuring the angular indexing of the plate, the support surface of the plate has overflowing, within the anchor range, at least one anti-rotation fin. According to another characteristic, the periphery of the anchoring surface has arrangements capable of constituting hollow or raised asperities. In order to solve the problem posed by the coupling of the insert with respect to the plate, the plate has a circular flange for embedding the insert. The circular flange has arrangements cooperating with complementary arrangements of the insert to provide angular indexing of said insert.

The arrangements consist of a system of pins and lights. In one embodiment, the plate has at its bearing surface, holes for the engagement of fixing screws cooperating with the cancellous bone and / or reaching the cortical bone of the opposite edge. The invention is described below in more detail with reference to the figures of the accompanying drawings in which: FIG. 1 is a perspective view of the plate considered in view from above, FIGS. 2 and 3 are views. in perspective of the plate considered in view from below, - Figure 4 is a perspective view of the plate considered in plan view, - Figure 5 is a perspective view corresponding to Figure 4 showing another perspective angle, - Figure 6 is a perspective view in partial section of the plate, - Figure 7 shows the mounting of the plate at the diaphysis of the humerus in the position of cooperation with the glenoid implant in the form of a hemispherical hinge head. It is recalled that the invention relates to an inverted joint prosthesis of the shoulder. The humeral implant comprises a plate (1), without humeral stem, receiving an insert (2) intended to cooperate with a cup or hemispherical head (3) fixed in a glenoid cavity as will be indicated in the following description.

According to another characteristic underlying the invention, the plate (1) has an anchoring surface (la) of reduced height and able to be engaged only in the metaphyseal part of the humeral canal. The entire plate (1) has a generally circular shape. The height of the anchoring range (1) is between 10 and 20 mm approximately.

Advantageously, the height of this circular reach (la) is of the order of 15 mm to avoid conflicts with the opposite humeral cortex. The periphery of the anchor span (1a) has recessed and raised asperities (1b) to improve anchoring. The end of this span (la) delimits a frustoconical bearing (lai) to facilitate impaction. According to another feature, the scope (la) is hollow and has peripherally openings (1c) to facilitate bone regrowth.

Note that the bearing face (1d) of the plate (1) has within the scope (la) and overflow, at least one anti-rotation fin (1c). The plate (1) has a circular flange (1f) for embedding the insert (2). For example, the circular rim (1f) has an internal peripheral boss (1g) adapted to cooperate with a complementary groove that the insert (2) has in order to ensure its fixation by clipping. It should also be noted that the circular rim (1f) has recessed notches (1f1) in relief (1f2) capable of cooperating with complementary shapes that the insert presents for the purpose of its angular indexing.

In another embodiment, the plate (1) has at its bearing surface holes (1g) for the engagement of fixing screws cooperating with the cancellous bone and can reach the cortical bone of the opposite edge. Considering the low height of the anchoring surface (1a) in opposition to an anchor rod which this type of implant generally presents, it is possible to reduce the orientation of the plate with respect to the section of the os since it is not constrained by a rod. In other words, according to the invention, one is not constrained by the cervico-diaphyseal angle at the level of the humeral head. As indicated, the implant as defined according to the features of the invention cooperates with a hemispherical head or cup (3) fixed in the glenoid cavity. This glenoid implant may be of any type known or appropriate in the field of shoulder arthroplasty prostheses. For example, this glenoid implant may have, opposite the hinge head (3), a bearing surface which has on the side of the outer abutment of the scapula, an extension capable of increasing the amplitude of rotation and to avoid the notch effects by repeated contact of the polyethylene on the bone.

This extension is connected perpendicular to the bearing surface of the hinge head thus acting as a means of rotation and anti-elevation. These characteristics are apparent from the teaching of the French patent FR 2 795 304.

The center of rotation of the hinge head is therefore offset downward relative to the median plane and the center of the anatomical glenoid. The advantages are clear from the description.5