Patent Application
20230404767
The invention relates to a glenoid implant for reverse shoulder prosthesis, intended to be attached to the patient's glenoid fossa.
A reverse total shoulder prosthesis comprises a humeral implant, in other words a part attached in the patient's humerus, and a glenoid implant, in other words a part attached on the patient's glenoid fossa (also called glenoid cavity). These two implants are hinged to each other to restore the mobility of the arm of the patient receiving surgery.
In case of a “reverse” total shoulder prosthesis, the center of rotation of the joint is shifted to the glenoid implant, unlike an “anatomic” prosthesis where it remains on the humeral implant.
This modification of the position of the center of rotation of the joint generates a modification of the muscles solicited to move the arm. In the present case, the deltoid muscle is solicited while, for an anatomic prosthesis, the rotator cuff muscles are solicited, i.e. the subscapularis, supraspinatus, infraspinatus and teres minor in addition to the deltoid. This modification of the muscles involved can be explained by irreparable damage of all or some of the rotator cuff muscles, such damage possibly occurring in old persons, in particular. In other words, and for persons suffering from irreparable damage to the rotator cuff muscles, a reverse shoulder prosthesis is preferred since it preserves the mobility of the shoulder from the first degrees of abduction of the arm with respect to the trunk. The reverse shoulder prosthesis therefore involves soliciting the deltoid muscle which is anchored to the humerus in a more distal manner than the rotator cuff muscles, thereby compensating for the damage to the rotator cuff muscles.
The reverse shoulder prosthesis is formed by a humeral implant comprising a hollow end (or cup) replacing the humeral head and, at the scapula, a bone anchoring base (or metaglene) to which a glenosphere that will collaborate with the cup positioned on the humerus is added.
Conventionally, the bone anchoring base present at the scapula is attached to this bone by several diverging anchor screws extending from the bone anchoring base. This spacing ensures that the glenoid implant is securely anchored by soliciting remote attachment points.
However, shoulder prostheses, and more particularly reverse shoulder prostheses, are used to restore the joint of persons suffering from osteoarthritis, in particular the reverse shoulder prosthesis for the reasons of shoulder mobility explained above. At an advanced stage of osteoarthritis, the damage to the joint, and more particularly to the glenoid cavity of the scapula, may be too serious to consider stable anchoring of the traditional glenoid implant. In other words, the available bone surface or bone capital is no longer sufficient (the bone wearing away), in particular at the portion connecting the glenoid cavity to the scapula, to guarantee stable anchoring of the bone anchoring base, which may jeopardize the possibility of restoring the joint with a shoulder prosthesis, even reverse.
The invention aims to provide a glenoid implant for reverse shoulder prosthesis allowing the use of a shoulder prosthesis for persons suffering from osteoarthritis at an advanced stage and for whom it would not be possible to consider the use of a prosthesis according to the prior art.
Thus, the invention relates to a glenoid implant for reverse shoulder prosthesis, comprising a base for anchoring the implant to a bone formed by a rod configured to extend through the thickness of the bone from a glenoid fossa, the rod comprising through-holes, and by screws for anchoring the rod configured to cross radially the rod, via the through-holes, and the bone, when the glenoid implant is implanted on the bone.
Thus, and instead of using an anchoring base that is difficult to stabilize, the rod extends through the thickness of the bone, in a bone trabecula, and is stabilized in the bone by anchor screws crossing radially the rod and the bone. Stable anchoring of the glenoid implant is therefore obtained, with a structure extending less (a rod) by using the bone areas that are less affected, which is particularly suitable for persons suffering from osteoarthritis at an advanced stage.
According to other optional characteristics of the glenoid implant taken alone or in combination:
The invention also relates to a reverse shoulder prosthesis comprising a glenoid implant according to the invention.
The invention also relates to a tool for gripping and guiding a glenoid implant according to the invention, comprising an end for locking to the rod and a gripping end, the gripping end extending at least partly parallel to the rod when the gripping and guiding tool is attached to the rod, the gripping end comprising at least one guiding hole to insert the anchor screws.
According to other optional characteristics of the glenoid implant taken alone or in combination:
The invention also relates to a use of a glenoid implant according to the invention to form a joint prosthesis.
The invention also relates to a method for attaching a glenoid implant according to the invention to form a reverse shoulder prosthesis.
The invention will be better understood on reading the following description, given solely by way of example and with reference to the accompanying drawings in which:
We now refer to
This glenoid implant 2 comprises an anchoring base formed by a rod 4 configured to extend through the thickness of a bone 6 (a scapula shown on
The rod 4, shown alone on
The rod 4 may comprise a face 10 for receiving a spacer 12, the receiving face 10 possibly comprising a bore 14, for example tapped, to attach the spacer 12 via a screw and/or a cone or a clip, for example by screwing if the bore 14 is tapped, possibly completed by a groove 16 forming a surface for interacting with a gripping and guiding tool 36 described below.
The rod 4 further comprises through-holes 18 for inserting the anchor screws 8, in this case three. Preferably, the through-holes 18 are made in areas of the rod 4 which will be located at the thickest areas of the bone 6. Thus, the anchor screws 8 will go through a thickness of bone 6 that is as large as possible. In addition, the rod 4 can be locked by soliciting the acromion and the coracoid.
As outlined above, the rod 4 can receive a spacer (or added ring) 12. The latter is used to form a remote link between the rod 4 and the glenosphere 20.
This spacer 12 may be formed in one piece or consist of several parts assembled to each other. It may be completely coaxial with the rod 4 or have an axis for attaching the glenosphere 20 that is offset with respect to the axis for attaching the spacer 12 to the rod 4. These attachment axes may or may not be parallel with each other. These various configurations can be used to adapt the glenoid implant 2 to the patient receiving it. The spacer 12 is added to the rod 4 once the latter has been locked to the bone 6.
As for the rod 4, the spacer 12 is made of a biocompatible material having an optimum lifetime that is as long as possible, allowing good distribution of the mechanical stresses. The spacer 12 can in particular be made entirely or partially of metal, plastic or ceramic. It can also be made of several different materials, including a composition of the above-mentioned materials.
In the examples described, the spacer 12 is a part added to the rod 4. It could also be made in one piece with the latter and form an end of the rod 4.
The glenosphere 20 is shown on
The glenosphere 20 can be centered or not and can be lateralized if necessary (as described above, in particular depending on the shape of the spacer 12). Centering means that a protrusion 28 that is used to attach the glenosphere 20 to the spacer 12 extends from the center of the flat surface of the hemisphere in a direction perpendicular to the plane in which the flat surface of the hemisphere extends. Off-centering, for example between 1 and 4 millimeters, means that a protrusion 28 that is used to attach the glenosphere 20 to the spacer 12 does not extend from the center of the flat surface of the hemisphere. The protrusion 28 may comprise an external thread in order to screw the glenosphere 20 onto the spacer 12, more particularly in the hole of the second portion 24 or 24′ of the spacer 12, threaded in this case as described above.
The glenosphere 20 can be marked, for example by engraving, to indicate its diameter, the fact that it is centered or off-centered or, and if necessary, to write text identifying the portion of the glenosphere 20 to be placed at an angle towards the upper position of the scapula, in other words “UP” in the example shown on
The possibility of using a glenosphere 20 of variable diameter, centered of off-centered, provides an additional possibility for adapting the glenoid implant 2 to the patient, in addition to the choice of the shape of the spacer 12 and the size of the rod 4.
The glenoid implant 2 may further comprise a stabilizing part 30 (or stabilizing fork). The latter, shown alone on
This stabilizing part 30 may comprise an end 32, advantageously drilled, for locking the stabilizing part 30 to the rod 4 and two stabilizing ends 34. The latter are arranged opposite each other so as to extend each side of the bone 6 (in this case the scapula) when the glenoid implant 2 is positioned. At least one stabilizing end 34 could rest against the bone 6 when the glenoid implant 2 is positioned. In this case, it can have a flat surface extending parallel to the bone 6 in order to rest against a large area. The number and shape of the stabilizing ends 34 may vary.
The stabilizing part 30 could also provide additional bone anchoring for the glenoid implant 2. At least one stabilizing end 34 (or the stabilizing end if there is only one) may in this case comprise a through-hole to attach it to the bone 6, for example by screwing, and thus create an additional anchor point.
As described above for other elements, the stabilizing part 30 is made of a biocompatible material having an optimum lifetime that is as long as possible, allowing good distribution of the forces. It may for example be made of a titanium alloy, stainless steel, cobalt chromium or a polymer material.
The locking end 38 and the gripping end 40 are advantageously two separate parts of the gripping and guiding tool 36. Consequently, the locking end 38 is firstly added to the rod 4 (whether or not the latter is provided with the stabilizing part 30). This locking end 38 is advantageously hollow and partially tapped in order to insert an intermediate part 39 comprising at least an external thread in order to lock by screwing the locking end 38 onto the rod 4 (see
The gripping end 40 is then added to the locking end 38 (see
The gripping end 40 comprises a part extending parallel to the rod 4 when the latter is held by the gripping and guiding tool 36 and comprises holes 46 that can be aligned with the through-holes 18. These guiding holes 46 are used to guide a surgeon when positioning the rod 4. The alignment allows the surgeon to know where to drill the bone 6 to reach a through-hole 18. To do this, the surgeon can position a guiding element 48, in this case of cylindrical shape, that extends from the guiding holes 46 and perpendicularly to the rod 4 and to the part of the gripping end 40 that has the guiding holes 46 (see
As shown on
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2204313 | May 2022 | FR | national |
