FR2860427A1 - HUMERAL INSERT FOR AN INVERSE SHOULDER PROSTHESIS. - Google Patents

Abstract

This humeral insert (3) which can be engaged on a humeral rod (2) and which can receive a glenosphere (4), comprises means for fixing to the humeral rod (2) on its posterior face, and a concave articular surface (9) on its front face (8). According to the invention, it has a recess (12) in its belt wall (10).

Description

The present invention relates to a humeral insert for a prosthesis

inverted shoulder.

  In the context of a reconstruction of the humeral joint, it is well known to place a total shoulder prosthesis.

  When the cap is very damaged, we can put a so-called inverted prosthesis. This type of prosthesis comprises a humeral subset and a scapular subset.

  The humeral subset is composed of a humeral stem that is engaged in the medullary canal of the humerus and an insert that is attached to the head of the humeral stem. This insert has a concave outer face and is generally made of polyethylene.

  The scapular subset is composed of a glenosphere attached to the scapular part of the joint to be reconstructed. The fixation of the glenosphere is via a metal base anchored in the scapular bone.

  Clinical experience has revealed a significant disadvantage of this type of prosthesis.

  Practitioners have been able to note that there is a notch in the scapula pillar, that is to say the part located under the glenoid cavity of the scapula.

  This bone notch is due to a conflict between the humeral implant and the shoulder blade abutment.

  Indeed, during an adduction movement of the arm, and in particular at the end of this movement, it may occur a collision between the humeral insert and the abutment of the scapula, which can then create this bone notch.

  This phenomenon is even more marked in patients in whom the abutment of the scapula is vertical.

  This notch generally stabilizes but, in some cases, may progress to greater necrosis, due in particular to the polyethylene debris resulting from the friction of the glenosphere on the insert.

  Although these cases are not in the majority, it is very undesirable to allow a notch to form in a bone, since the latter, even if stabilized, remains an area of weakening of the bone.

  An object of the invention is therefore to provide a humeral insert which minimizes the formation of a bone notch.

  To this end, the present invention relates to a humeral insert that can be engaged on a humeral stem and can receive a glenosphere, comprising means for attachment to the humeral stem on its posterior surface, and a concave articular surface on its anterior wall.

  Thus, the presence of a recess in the belt wall of the insert makes it possible, by orienting the recess facing the abutment pillar, to avoid a conflict between the insert and the abutment pillar.

  According to an advantageous embodiment, the recess is secant with the concave articular surface, which makes it possible to preserve a reduced encumbrance of the insert, without impairing the holding of the glenosphere in the concave articular surface.

  According to an advantageous possibility, the belt wall is substantially trapezoidal, the recess being formed in its large base.

  Preferably, the recess has a cylindrical surface, which allows the recess to be made by a milling operation.

  In addition, the cylindrical surface forms an acute angle with the belt face.

  In one embodiment, the recess extends over a portion of the waist face adjacent to the anterior face.

  To avoid a conflict between a fixed base in the scapular bone receiving the glenosphere and the humeral insert, a chamfer is formed at each of the connection areas between the recess and the anterior face.

  An alternative may provide that the insert has a conical pin protruding from its posterior face by its attachment to a humeral stem.

  For a good understanding, the invention is described with reference to the accompanying drawing showing by way of non-limiting example an embodiment of a humeral insert according thereto.

  Figures 1 to 3 show respectively in side view and in perspective in two orientations a humeral insert 30 according to the invention cooperating with a glenosphere of a total shoulder prosthesis.

  Figure 4 shows a total shoulder prosthesis incorporating the humeral insert according to the invention.

  FIG. 4 represents the usual components of a shoulder prosthesis, namely a humeral stem 2 intended to be anchored in the medullary canal of a humerus, a humeral insert 3 which engages in the metaphyseal part of the humeral stem 2, a glenosphere 4 and a base 5 fixed to the scapular portion of the joint to be reconstructed.

  Referring to Figures 1 to 3, it can be seen that the humeral insert 3 has a posterior face 6 of which protrudes a conical pin 7 for attachment to the femoral stem. The anterior face 8 of the insert has a concave articular surface 9 which, in the example shown, has a perfect congruence with the glenosphere.

  The waist face 10 connecting the anterior and posterior faces has a trapezoidal shape, which prevents its rotation when mounted on the humeral stem.

  The insert may, in the usual way, be made of polyethylene.

  As shown in the figures, a recess 12 is formed in the belt face of the insert.

  The recess 12 is made in the large base of the belt and cuts the concave articular surface 9.

  The recess 12 has a cylindrical surface which is inclined with respect to the belt surface by an inclination angle of up to about 50.

  It is also noted that the recess 12 is not made over the entire height of the belt face 10, but is only hollowed out on the part of the waist wall 10 situated on the side of the front face 8.

  It should also be noted that, at each of the connection areas of the recess and the anterior face, two chamfers 14 are made.

  Thus, when a total shoulder prosthesis comprising an insert 3 is placed, it can be seen with reference to FIG. 3 that, at the end of the adduction movement, the humeral insert 3 forms with the glenosphere an angle which would lead to a conflict between the pillar of the scapula and the humeral insert, if it was not formed in the latter, I 'recess 12.

  It should be noted that the chamfers 14 also contribute to a good functioning of the prosthesis by avoiding a conflict between the humeral insert 3 and the metal base (also called metal back glenoid), during an internal rotational movement of the prosthesis. arms.

  The invention thus provides a humeral insert which avoids the formation of a bone notch in the scapular abutment.

  Of course, the invention is not limited to the embodiment described above by way of non-limiting example, but it encompasses all the embodiments.

  Thus, the humeral insert could be generally circular and non-trapezoidal.

Claims (8)

  1. A humeral insert (3) engageable with a humeral stem (2) and capable of receiving a glenosphere (4), comprising means for attachment to the humeral stem (2) on its posterior surface, and a concave articular surface (9). ) on its anterior face (8), characterized in that it has a recess (12) in its belt wall (10).   2. humeral insert according to claim 1, characterized in that the recess (12) is secant with the concave articular surface (9).   3. humeral insert according to claim 1 or claim 2, characterized in that the belt wall (10) is substantially trapezoidal, the recess (12) being formed in its large base.   4. humeral insert according to one of claims 1 to 3, characterized in that the recess (12) has a cylindrical surface.   5. Humeral insert according to claim 4, characterized in that the recess (12) forms an acute angle with the belt face (10).   6. humeral insert according to claim 4 or claim 5, characterized in that the recess (12) extends over a portion of the belt face (10) adjacent to the anterior face (8).   Humeral insert according to one of claims 2 to 6, characterized in that a chamfer (14) is formed at each of the connection areas between the recess (12) and the anterior face (8).   8. humeral insert according to one of claims 1 to 7, characterized in that it has a conical pin (7) protruding from its rear face (6).