Reverse shoulder prosthesis glenoid implant

Abstract

The invention relates to a glenoid implant (2) for a reverse shoulder prosthesis, comprising a base for anchoring the implant to a bone formed by a rod (4) configured to extend into the thickness of the bone (6) from a glenoid cavity, the rod (4) comprising through-holes (18), and by anchoring screws (8) of the rod (4) configured to radially pass through the rod (4), through the through-holes (18), and the bone (6), when the glenoid implant (2) is implanted on the bone (6). Figure for abstract: figure 1

Description

Title of the invention: Reverse shoulder prosthesis glenoid implant

[0001] The invention relates to a glenoid implant for reverse shoulder prosthesis, intended to be fixed to the glenoid cavity of the patient.

[0002] A reverse total shoulder prosthesis comprises a humeral implant, i.e. a part fixed in the patient's humerus, and a glenoid implant, i.e. a part fixed on the patient's glenoid cavity (also called glenoid). These two implants are articulated with each other in order to restore the mobility of the operated patient's arm.

[0003] In the context of a so-called "reverse" total shoulder prosthesis, the center of rotation of the joint is moved onto the glenoid implant, unlike a so-called "anatomical" prosthesis where it remains located on the humeral implant.

[0004] This modification of the positioning of the center of rotation of the joint causes a modification of the muscles used to move the arm. In this case, it is the deltoid muscle that is used, whereas for an anatomical prosthesis, the muscles used remain those forming the rotator cuff, namely the muscles: subscapularis, supraspinatus, infraspinatus and teres minor in addition to the deltoid. This modification of the muscles involved can be explained by irreparable damage to all or part of the muscles of the rotator cuff, such damage being able to occur in elderly people in particular. In other words, and for people suffering from irreparable damage to the muscles forming the rotator cuff, a reverse shoulder prosthesis is preferred because it allows the shoulder to retain mobility from the first degrees of abduction of the arm relative to the trunk.The reverse shoulder prosthesis therefore involves the use of the deltoid muscle which is anchored to the humerus more distally than the rotator cuff muscles, thus compensating for damage to the muscles forming the rotator cuff.

[0005] The reverse shoulder prosthesis is formed by a humeral implant comprising a hollow end (or cup) replacing the humeral head and, at the level of the scapula, a bone anchoring base (or metaglene) on which is attached a glenosphere intended to collaborate with the cup positioned on the humerus.

[0006] Conventionally, the bone anchoring base present at the level of the scapula is fixed to this bone by means of several anchoring screws extending from the bone anchoring base and diverging. This distance makes it possible to ensure good anchoring of the glenoid implant by requiring distant fixation points.

[0007] However, shoulder prostheses, and more particularly reverse shoulder prostheses, are used to restore the joint of people suffering from osteoarthritis, in particular the reverse shoulder prosthesis for the reasons of shoulder mobility explained above. At an advanced stage of osteoarthritis, the degradation of the joint, and more particularly of the glenoid cavity of the scapula, may be too significant to envisage stable anchoring of the conventional glenoid implant. In other words, the available bone surface or bone capital is no longer sufficient (the bone hollows out), in particular at the level of the portion connecting the glenoid cavity to the scapula, to ensure stable anchoring of the bone anchor base, which may call into question the possibility of restoring the joint by a shoulder prosthesis, even a reversed one.

[0008] The aim of the invention is to provide a glenoid implant for a reverse shoulder prosthesis allowing the use of a shoulder prosthesis for people suffering from osteoarthritis at an advanced stage and for whom it would not be possible to provide the use of a prosthesis according to the prior art.

[0009] For this purpose, the invention relates to a glenoid implant for a reverse shoulder prosthesis, comprising a base for anchoring the implant to a bone formed by a rod configured to extend into the thickness of the bone from a glenoid cavity, the rod comprising through-holes, and by screws for anchoring the rod configured to radially pass through the rod, via the through-holes, and the bone, when the glenoid implant is implanted on the bone.

[0010] Thus, and instead of using an anchoring base that is difficult to stabilize, the rod extends into the thickness of the bone, in a bone trabeculae, and is stabilized in the bone by anchoring screws radially passing through the rod and the bone. This ensures stable anchoring of the glenoid implant with a structure that extends less (a rod) by exploiting less affected bone areas, which is particularly suitable for people suffering from advanced osteoarthritis.

[0011] According to other optional characteristics of the glenoid implant taken alone or in combination: - The glenoid implant includes a glenosphere attached to the stem; - the rod comprises a surface for receiving a spacer for fixing the stem to the glenosphere; - the receiving surface comprises a bore configured to cooperate with the spacer and a groove surrounding the bore, the groove being configured to interact with a tool for gripping and guiding the rod; - the spacer is formed of a first portion for fixing the spacer to the rod and a second portion for fixing the spacer to the glenosphere, the first portion and the second portion being offset from each other;

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[0020] - the first portion and the second portion are inclined relative to each other; - the glenoid implant further comprises a stabilizing part of the glenoid implant relative to the bone when the glenoid implant is implanted on the bone; and - the stabilizing part comprises two stabilizing ends configured to extend on either side of the bone when the glenoid implant is implanted on the bone. 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 a rod-locking end and a gripping end, the gripping end extending at least partly parallel to the rod when the gripping and guiding tool is fixed to the rod, the gripping end comprising at least one guide hole for placing the anchoring screws. Depending on other optional features of the glenoid implant taken alone or in combination: - the gripping and guiding tool comprises at least one guide element for positioning the anchor screws, removable relative to the gripping end and able to extend between the guide hole and a through hole; and - the gripping end is rotatable relative to the locking end. The invention also relates to the use of a glenoid implant according to the invention for forming a joint prosthesis. The invention also relates to a method of fixing a glenoid implant according to the invention to form a reverse shoulder prosthesis. Brief description of the figures The invention will be better understood on reading the following description, given solely by way of example and with reference to the appended drawings in which: [Fig.l] is a perspective view of a reverse shoulder prosthesis glenoid implant according to the invention, [Fig.2] is a side view of a reverse shoulder prosthesis glenoid implant according to the invention, [Fig.3] is a perspective view of a glenoid implant of a reverse shoulder prosthesis according to the invention placed at the level of a scapula,

[0021] [Fig.4] is a perspective view of a stem of a glenoid prosthesis implant reverse shoulder according to the invention,

[0022] [Fig.5] is a perspective view of a first variant of a spacer of a glenoid implant for reverse shoulder prosthesis according to the invention,

[0023] [Fig.6] is a side view of a second variant of a spacer of an implant reverse shoulder prosthesis glenoid according to the invention,

[0024] [Fig.7] is a perspective view of a second variant of a spacer of a glenoid implant for reverse shoulder prosthesis according to the invention,

[0025] [Fig.8] is a side view of a second variant of a spacer of an implant reverse shoulder prosthesis glenoid according to the invention,

[0026] [Fig.9] is a perspective view of a stabilizing part of a glenoid implant of reverse shoulder prosthesis according to the invention,

[0027] [Fig. 10] is a perspective view of a first variant of a glenosphere of a glenoid implant of a reverse shoulder prosthesis according to the invention,

[0028] [Fig. 11] is a perspective view of a second variant of a glenosphere of a reverse shoulder prosthesis glenoid implant according to the invention, and

[0029] [Fig. 12] is a perspective view of a stem of a glenoid implant of a reverse shoulder prosthesis according to the invention attached to a tool for gripping and guiding the latter,

[0030] [Fig. 13] is an exploded view of a stem of a glenoid implant of a reverse shoulder prosthesis according to the invention and of a part of a tool for gripping and guiding the stem,

[0031] [Fig.14] is a perspective view of a stem of a glenoid implant of a reverse shoulder prosthesis according to the invention being connected to a tool for gripping and guiding the stem, and

[0032] [Fig. 15] is a perspective view of a glenoid implant being implanted on a scapula. Detailed description

[0033] Reference is now made to Figures 1 and 2 illustrating a glenoid implant 2 for a reverse shoulder prosthesis.

[0034] This glenoid implant 2 comprises an anchoring base formed by a rod 4 configured to extend into the thickness of a bone 6 (a scapula visible in [Fig. 3]) from a glenoid cavity and by anchoring screws 8 (or cortical screws) of the rod 4 in the bone configured to radially pass through the rod 4 and the bone 6. As explained above, the rod 4 extends into a bone trabecula of the bone 6, for example at the junction between the scapula and the acromion, to allow anchoring, by placing the anchoring screws 8, without extending too much into the bone 6, which could pose problem in the case of osteoarthritis at too advanced a stage. We therefore understand that the surgeon will proceed to make a bore in the thickness of the bone 6 to house the rod 4. The anchoring screws 8 are then put in place to pass radially through the bone 6 and the rod 4 (through through holes 18 of the latter) and thus lock the rod 4 in the bone 6 as illustrated in [Fig.3]. We obviously understand that "radially" means in a direction perpendicular to a longitudinal axis A of the rod 4.

[0035] The rod 4, visible alone in [Fig. 4], is made of a biocompatible material and having the longest possible optimal lifespan. It can for example be made of titanium alloy, stainless steel, cobalt chrome or even from a polymer material. The length of the rod 4 can vary in order to best adapt to the size of the bone 6, with a diameter that can vary between 5 and 14 millimeters. It is possible for this purpose to design several rods 4 of variable sizes and variable length or a rod 4 formed by an assembly of several parts (each part can for example carry at least one through hole 18) whose lengths can vary in order to assemble a rod 4 adapted to the bone 6. The length of the rod 4 can for example vary between 40 and 120 millimeters.

[0036] The rod 4 may comprise a receiving face 10 for a spacer 12, the receiving face 10 being able to comprise a bore 14, for example tapped, allowing the spacer 12 to be fixed via a screw and / or a cone or a clip, for example by screwing if the bore 14 is tapped, potentially completed by a groove 16 forming an interaction surface with a gripping and guiding tool 36 described below.

[0037] The rod 4 further comprises through holes 18 allowing the passage of the anchoring screws 8, here three in number. Preferably, the through holes 18 are made at the areas of the rod 4 which will be located at the areas of the bone 6 where the thickness of the latter will be the greatest. Thus, the anchoring screws 8 will pass through the greatest possible thickness of bone 6. It is also possible to lock the rod 4 by stressing the acromion and the coracoid.

[0038] As seen above, the rod 4 can receive a spacer (or attached ring) 12. The latter makes it possible to ensure a remote connection between the rod 4 and the glenosphere 20.

[0039] This spacer 12 can be formed in one piece or by several parts assembled to each other. It can be totally coaxial with the rod 4 or have an axis of fixation of the glenosphere 20 offset relative to the axis of fixation of the spacer 12 on the rod 4. These axes of fixation can be parallel to each other or not. These different configurations make it possible to adapt the glenoid implant 2 to the patient receiving it. The spacer 12 is attached to the rod 4 after the latter has been locked on the bone 6.

[0040] Figures 5 and 6 illustrate a first variant of a spacer 12. The latter is formed of two portions 22 and 24 made in one piece but offset, for example by 1 to 25 millimeters relative to each other. The first portion 22, making it possible to connect the rod 4 to the spacer 12, comprises a first orifice making it possible to carry out this connection, for example by screwing while being threaded and / or conical. This orifice aligns with the bore 14 of the rod 4. The second portion 24, making it possible to connect the glenosphere 20 to the spacer 12, comprises a second orifice making it possible to carry out this connection, for example by screwing while being tapped and collaborating with a projection 28 of the glenosphere 20 comprising an external thread. The fixing can also be carried out using a Morse taper. The portions are parallel to each other.

[0041] Figures 7 and 8 illustrate a second variant of a spacer 12. The latter is formed of two portions 22' and 24' made in one piece but offset, for example by 1 to 25 millimeters relative to each other. The first portion 22', making it possible to connect the rod 4 to the spacer 12, comprises a first orifice making it possible to make this connection, for example by screwing while being threaded. This orifice aligns with the bore 14 of the rod 4. The latter carries a protuberance 26 collaborating with the groove 16 as explained above. The second portion 24', making it possible to connect the glenosphere 20 to the spacer 12, comprises a second orifice making it possible to make this connection, for example by screwing, being threaded and collaborating with a projection 28 of the glenosphere 20 comprising an external thread.The portions are inclined relative to each other, for example forming an angle of between 5° and 30°, which makes it possible to fix the glenosphere 20 in an inclined manner relative to the rod 4.

[0042] As for the rod 4, the spacer 12 is made of a biocompatible material and having the longest possible optimal lifespan, allowing good distribution of mechanical stresses. The spacer 12 can in particular be made entirely or partly of metal, plastic or ceramic. It can also be made with several different materials including a composition of the aforementioned materials.

[0043] 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 formed one end of the rod 4.

[0044] The glenosphere 20 is illustrated in Figures 10 and 11. This glenosphere 20 may be spherical in shape (half-sphere, portion of sphere larger than a half-sphere, portion of sphere extended by a cylindrical portion). Its diameter may be between 30 and 46 millimeters. This diameter may of course be outside this range. It may be made of ceramic. The type of ceramic used may be any type of ceramic known to those skilled in the art. For example, it may be alumina, zirconia or a composite material. Since ceramic is a hard material, it can be used in the context of a “hard / hard” or “hard-soft” material pair. In this second example, the so-called “soft” material can be ultra-high molecular weight polyethylene (UHMWPE), polyetheretherketone (PEEK), PEKK (poly ether ketone ketone) or their derivatives.

[0045] The glenosphere 20 may be centered or not and may be lateralized if necessary (as seen above, in particular depending on the shape of the spacer 12). Centering means that a projection 28 allowing the glenosphere 20 to be fixed 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 projection 28 allowing the glenosphere 20 to be fixed to the spacer 12 does not extend from the center of the flat surface of the hemisphere. The projection 28 may comprise an external thread making it possible to screw the glenosphere 20 onto the spacer 12, more particularly into the orifice of the second portion 24 or 24' of the spacer 12, threaded in this case as seen above.

[0046] The glenosphere 20 may be marked, for example by engraving, to indicate its diameter, the fact that it is centered or eccentric, or even, and if necessary, to inscribe a note making it possible to identify the portion of the glenosphere 20 which must be placed angularly towards the upper position of the scapula, namely "UP" in the example shown in [Fig.l 1] of the eccentric glenosphere.

[0047] The possibility of using a glenosphere 20 of variable diameter, centered or eccentric, allows an additional possibility of adaptation of 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.

[0048] The glenoid implant 2 may further comprise a stabilizing part 30 (or stabilizing fork). The latter, visible alone in [Fig. 9] or mounted on the rod 4 in Figures 1 to 3, may be attached to the rod 4, which then comprises a fixing slot 42 for the stabilizing part 30. More precisely, the fixing slot 42 may open at an internal thread of the rod 4. An intermediate part comprising an external thread may then be screwed to the rod 4 and lock the stabilizing part 30.

[0049] This stabilizing part 30 may comprise a locking end 32, advantageously pierced, of the stabilizing part 30 to the rod 4 and two stabilizing ends 34. The latter are arranged opposite one another so as to extend on either side of the bone 6 (here the scapula) when the glenoid implant 2 is put in place. It can be envisaged that at least one stabilizing end 34 is in abutment against the bone 6 when the glenoid implant 2 is put in place. In this case, it may have a flat surface extending parallel to the bone 6 in order to obtain support over a large area. The number and shape of the stabilizing ends 34 may vary.

[0050] The stabilizing part 30 could also allow additional bone anchoring for the glenoid implant 2. At least one stabilizing end 34 (or the stabilizing end if there is only one) can in this case comprise a through hole to fix it to the bone 6, for example by screwing and thus create an additional anchoring point.

[0051] As seen before for other elements, the stabilizing part 30 is made of a biocompatible material, having the longest possible optimal lifespan and allowing good recovery of forces. It can for example be made of titanium alloy, stainless steel, cobalt chrome or even from a polymer material.

[0052] [Fig. 12] illustrates the rod 4 attached to a gripping and guide 36. The latter comprises a locking end 38 configured to collaborate with the groove 16 and the bore 14 in order to attach the rod 4 to the gripping and guiding tool 36 and to be able to place the latter in the cavity formed in the bone 6. The gripping and guiding tool 36 also comprises a gripping end 40 of the assembly formed by the latter and the rod 4 by a surgeon.

[0053] The locking end 38 and the gripping end 40 are advantageously two separate parts of the gripping and guiding tool 36. Therefore, the locking end 38 is initially attached 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 so as to insert therein an intermediate part 39 comprising at least one external thread so as to screw-lock the locking end 38 onto the rod 4 (see [Fig. 13]).

[0054] The gripping end 40 is then attached to the locking end 38 (see [Fig. 14]) and fixed to the latter, for example by screwing them together, for example by a knurled head screw 44 visible in Figures 12 and 15.

[0055] The gripping end 40 comprises a portion extending parallel to the rod 4 when the latter is held by the gripping and guiding tool 36 and comprises holes 46 which can be aligned with the through-holes 18. These guide holes 46 make it possible to guide a surgeon when positioning the rod 4. Indeed, the alignment allows him to know where to drill the bone 6 to find a through-hole 18. For this purpose, he can position a guide element 48, here of cylindrical shape, extending from the guide holes 46 and perpendicular to the rod 4 and to the portion of the gripping end 40 carrying the guide holes 46 (see [Fig. 15]). This guide element 48 then comes into abutment against the bone 6 and is advantageously generously hollow so as to be able to introduce means for drilling the bone 6 then the anchoring screws 8 and means for screwing the latter to the rod 4. The anchoring screws 8 then pass through the bone 6 and the rod 4.

[0056] In [Fig. 15], a rod 4 can be seen, carrying a stabilizing part 30, already in place in a cavity formed in the thickness of the bone 6. The gripping end 40 is placed so as to align at least one guide hole 46 with a through orifice 18 (not visible in this figure). A guide element 48 extends from a hole 46 and is pressed against the bone 6.

[0057] As can be seen in [Fig. 4], the through holes 18 may not be aligned but extend in different directions for at least two of them. It is therefore advantageous to provide a rotation capacity of the gripping end 40 relative to the locking end 38. Thus, it is possible to move the gripping end 40 to align a guide hole 46 with a through hole 18. In [Fig. 4], two through holes 18 are aligned and the third is offset by 90°. The gripping end 40 can therefore pivot by 90° to align with one or another through hole 18. List of references

[0058] 2: glenoid implant

[0059] 4: stem

[0060] 6: bones

[0061] 8: anchor screw

[0062] 10: receiving surface

[0063] 12: spacer

[0064] 14: bore

[0065] 16: throat

[0066] 18: through holes

[0067] 20: glenosphere

[0068] 22, 22': first portions of the spacer

[0069] 24, 24': second portions of the spacer

[0070] 26: protuberance

[0071] 28: projection

[0072] 30: stabilizing part

[0073] 32: locking end

[0074] 34: stabilization end

[0075] 36: gripping and guiding tool

[0076] 38: locking end

[0077] 39: intermediate piece

[0078] 40: gripping end

[0079]

[0080]

[0081]

[0082]

[0083] 42: fixing slot 44: knurled head screw 46: guide holes 48: guide element A: longitudinal axis of the rod

Claims

Claims

1. Glenoid implant (2) for a reverse shoulder prosthesis, comprising a base for anchoring the implant to a bone formed by a rod (4) configured to extend into the thickness of the bone (6) from a glenoid cavity, the rod (4) comprising through-holes (18), and by anchoring screws (8) of the rod (4) configured to radially pass through the rod (4), through the through-holes (18), and the bone (6), when the glenoid implant (2) is implanted on the bone (6), characterized in that the rod (4) is formed of several parts removable from each other so as to be able to form a rod of variable length, for example between 40 and 120 millimeters.

2. Glenoid implant (2) according to claim 1, comprising a glenosphere (20) attached to the stem (4).

3. Glenoid implant (2) according to any one of the preceding claims, in which the rod (4) comprises a receiving surface (10) of a spacer (12) for fixing the rod (4) to the glenosphere (20).

4. Glenoid implant (2) according to the preceding claim, wherein the receiving surface (10) comprises a bore (14) configured to collaborate with the spacer (12) and a groove (16) surrounding the bore (14), the groove (16) being configured to interact with a gripping and guiding tool (34) of the rod (4).

5. Glenoid implant (2) according to any one of claims 3 or 4, wherein the spacer (12) is formed of a first portion (22, 22') for fixing the spacer (12) to the rod (4) and a second portion (24, 24') for fixing the spacer (12) to the glenosphere (20), the first portion (22, 22') and the second portion (24, 24') being offset from each other.

6. Glenoid implant (2) according to the preceding claim, wherein the first portion (22, 22') and the second portion (24, 24') are inclined relative to each other.

7. A glenoid implant (2) according to any preceding claim, further comprising a stabilizing part (30) of the glenoid implant (2) relative to the bone (6) when the glenoid implant (2) is implanted on the bone (6).

8. Glenoid implant (2) according to the preceding claim, in which the stabilizing part (30) comprises two stabilizing ends (34) configured to extend on either side of the bone (6) when the glenoid implant (2) is implanted on the bone (6).

9. Reverse shoulder prosthesis characterized in that it comprises a glenoid implant (2) according to any one of claims 1 to 8.

10. A tool for gripping and guiding (36) a glenoid implant (2) according to any one of claims 1 to 8, comprising a locking end (38) for locking to the rod (4) and a gripping end (40), the gripping end (40) extending at least partly parallel to the rod (4) when the gripping and guiding tool (36) is fixed to the rod (4), the gripping end (40) comprising at least one guide hole (46) for placing the anchoring screws (8), characterized in that the gripping and guiding tool (36) comprises at least one guide element (48) for placing the anchoring screws (8) removable relative to the gripping end (40) and able to extend between the guide hole (46) and a through hole (18).

11. A gripping and guiding tool according to claim 10, wherein the gripping end (40) is rotatable relative to the locking end (38).

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