INVERSE SHOULDER JOINT PAN IMPLANT

Description

[0001] The invention relates to a glenoid implant for a reverse shoulder prosthesis, intended to be fixed to the patient's glenoid cavity. The closest prior art is document WO 2014 / 075037 A1, which defines the preamble of claim 1.

[0002] A total reverse shoulder replacement consists of a humeral implant, which is fixed in the patient's humerus, and a glenoid implant, which is fixed in the glenoid cavity (also called the glenoid fossa). These two implants are articulated with each other to restore mobility to the patient's arm.

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

[0004] This change in the positioning of the joint's center of rotation results in 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 subscapularis, supraspinatus, infraspinatus, and teres minor muscles, in addition to the deltoid. This modification of the muscles involved can be explained by irreparable damage to all or part of the rotator cuff muscles, such damage being particularly common in older individuals. In other words, for individuals with irreparable damage to the rotator cuff muscles, a reverse shoulder prosthesis is preferred because it allows for the preservation of shoulder mobility from the first degrees of arm abduction relative to the trunk.The reverse shoulder prosthesis therefore involves the use of the deltoid muscle which is anchored on the humerus more distally than the rotator cuff muscles, it then compensates for the 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) onto which is attached a glenosphere intended to collaborate with the cup positioned on the humerus.

[0006] Typically, the bony anchor base located on the scapula is fixed to this bone by means of several anchoring screws extending from the bony anchor base and diverging outwards. This spacing ensures good anchoring of the glenoid implant by applying force to widely spaced fixation points.

[0007] However, shoulder prostheses, and more specifically reverse shoulder prostheses, are used to restore the joint in people suffering from osteoarthritis, particularly the reverse shoulder prosthesis for the reasons of shoulder mobility explained above. In an advanced stage of osteoarthritis, the deterioration of the joint, and more specifically of the glenoid fossa of the scapula, may be too extensive to consider stable anchoring of the conventional glenoid implant. In other words, the available bone surface area or bone mass is no longer sufficient (the bone recedes), particularly in the portion connecting the glenoid to the scapula, to ensure stable anchoring of the bone base, which may jeopardize the possibility of restoring the joint with a shoulder prosthesis, even a reverse one.

[0008] The invention aims to provide a glenoid implant for reverse shoulder prosthesis allowing the use of a shoulder prosthesis for people suffering from advanced osteoarthritis and for whom it would not be possible to foresee 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 as defined in claim 1.

[0010] Thus, instead of using a difficult-to-stabilize anchoring base, the stem extends within the bone, into a bony trabecula, and is stabilized within the bone by anchoring screws that pass radially through the stem and the bone. This ensures stable anchoring of the glenoid implant with a less extensive structure (a stem) by utilizing less affected bone areas, which is particularly suitable for individuals with advanced osteoarthritis.

[0011] Depending on other optional features of the glenoid implant, taken alone or in combination: The glenoid implant comprises a glenosphere attached to the stem; the stem comprises a receiving surface for a spacer for fixing the stem to the glenosphere; the receiving surface comprises a bore configured to collaborate with the spacer and a groove surrounding the bore, the groove being configured to interact with a tool for gripping and guiding the stem; the spacer is formed of a first portion for fixing the spacer to the stem and a second portion for fixing the spacer to the glenosphere, the first and second portions being offset from each other; the first and second portions are inclined from each other; the glenoid implant further comprises a stabilizing piece for the glenoid implant relative to the bone when the glenoid implant is implanted on the bone;and the stabilizing piece includes two stabilizing ends configured to extend on either side of the bone when the glenoid implant is implanted onto the bone.

[0012] The invention also relates to a reverse shoulder prosthesis comprising a glenoid implant according to the invention.

[0013] The invention also relates to a kit comprising a tool for gripping and guiding a glenoid implant according to the invention as defined in claim 10.

[0014] Depending on other optional features of the glenoid implant, taken alone or in combination: the gripping and guiding tool includes at least one guide element for setting the anchor screws removable relative to the gripping end and capable of extending between the guide hole and a through hole; and the gripping end is rotationally movable relative to the locking end.

[0015] The invention also relates to the use of a glenoid implant according to the invention to form a joint prosthesis. Brief description of the figures

[0016] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings in which: [ Fig. 1 ] is a perspective view of a glenoid implant for a reverse shoulder prosthesis according to the invention, [ Fig. 2 ] is a side view of a glenoid implant for a reverse shoulder prosthesis according to the invention, [ Fig. 3 ] is a perspective view of a glenoid implant for a reverse shoulder prosthesis according to the invention placed at the level of a scapula, [ Fig. 4 ] is a perspective view of a stem of a glenoid implant for a reverse shoulder prosthesis according to the invention, [ Fig. 5] is a perspective view of a first variant of a spacer for a glenoid implant of a reverse shoulder prosthesis according to the invention, [ Fig. 6 ] is a side view of a second variant of a spacer for a reverse shoulder prosthesis glenoid implant according to the invention, [ Fig. 7 ] is a perspective view of a second variant of a spacer for a glenoid implant of a reverse shoulder prosthesis according to the invention, [ Fig. 8 ] is a side view of a second variant of a spacer for a reverse shoulder prosthesis glenoid implant according to the invention, [ Fig. 9 ] is a perspective view of a stabilizing component of a glenoid implant for a reverse shoulder prosthesis according to the invention, [ Fig. 10 ] is a perspective view of a first variant of a glenosphere of a glenoid implant for a reverse shoulder prosthesis according to the invention, [ 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 [ Fig. 12 ] is a perspective view of a stem of a glenoid implant for a reverse shoulder prosthesis according to the invention attached to a tool for gripping and guiding the latter, [ Fig. 13 ] is an exploded view of a stem of a reverse shoulder prosthesis glenoid implant according to the invention and of part of a stem gripping and guiding tool, [ Fig. 14 ] is a perspective view of a stem of a reverse shoulder prosthesis glenoid implant according to the invention being connected to a stem gripping and guiding tool, and [ Fig. 15 ] is a perspective view of a glenoid implant being implanted on a scapula. Detailed description

[0017] We now refer to figures 1 and 2 illustrating a glenoid implant 2 of reverse shoulder prosthesis.

[0018] This glenoid implant 2 includes an anchoring base formed by a stem 4 configured to extend into the thickness of a bone 6 (a scapula visible on the figure 3) from a glenoid cavity and by anchoring screws 8 (or cortical screws) of the stem 4 in the bone, configured to pass radially through the stem 4 and bone 6. As explained above, the stem 4 extends into a bony trabecula of bone 6, for example at the junction between the scapula and the acromion, to allow anchoring, by the placement of the anchoring screws 8, without extending too far into bone 6, which could be problematic in cases of advanced osteoarthritis. It is therefore understood that the surgeon will perform a reaming in the thickness of bone 6 to accommodate the stem 4. The anchoring screws 8 are then placed to pass radially through bone 6 and the stem 4 (via through holes 18 in the latter) and thus lock the stem 4 in bone 6 as illustrated in the figure 3 It is clearly understood that "radially" means in a direction perpendicular to a longitudinal axis A of the rod 4.

[0019] Stem 4, visible alone on the figure 4 The rod 4 is made of a biocompatible material with the longest possible lifespan. For example, it can be made of titanium alloy, stainless steel, cobalt-chromium alloy, or a polymer material. The length of the rod 4 can vary to best fit the size of the bone 6, with a diameter ranging from 5 to 14 millimeters. To this end, it is possible to design several rods 4 of varying sizes and lengths, or a single rod 4 formed by assembling several parts (each part can, for example, have at least one through-hole 18) whose lengths can vary 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.

[0020] The rod 4 may include a receiving face 10 for a spacer 12, the receiving face 10 being able to include a bore 14, for example tapped, allowing the fixing of the spacer 12 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.

[0021] The stem 4 also includes through holes 18 for the passage of the anchoring screws 8, here three in number. Preferably, the through holes 18 are located in the areas of the stem 4 where the bone 6 is thickest. Thus, the anchoring screws 8 will penetrate the greatest possible thickness of bone 6. It is also possible to lock the stem 4 by applying pressure to the acromion and the coracoid process.

[0022] As seen above, the rod 4 can receive a spacer (or added ring) 12. The latter allows a remote connection between the rod 4 and the glenosphere 20.

[0023] This spacer 12 can be formed in one piece or from several parts assembled together. It can be perfectly coaxial with the stem 4 or have a glenosphere fixation axis 20 offset from the fixation axis of the spacer 12 on the stem 4. These fixation axes may or may not be parallel to each other. These different configurations allow the glenoid implant 2 to be adapted to the patient receiving it. The spacer 12 is attached to the stem 4 after the latter has been locked onto the bone 6.

[0024] THE figures 5 and 6These figures illustrate a first variant of a spacer 12. This spacer is formed of two portions 22 and 24 made from a single piece but offset, for example, by 1 to 25 millimeters relative to each other. The first portion 22, which connects the rod 4 to the spacer 12, has a first opening for this connection, for example, by screwing, being threaded and / or tapered. This opening aligns with the bore 14 of the rod 4. The second portion 24, which connects the glenosphere 20 to the spacer 12, has a second opening for this connection, for example, by screwing, being tapped and engaging with a projection 28 of the glenosphere 20 which has an external thread. The attachment can also be made using a Morse taper. The portions are parallel to each other.

[0025] THE figures 7 And 8illustrate a second variant of a spacer 12. This spacer 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', which connects the rod 4 to the spacer 12, has a first opening for this connection, for example, by screwing it in place. This opening aligns with the bore 14 of the rod 4. The rod 4 has a protrusion 26 that interacts with the groove 16, as explained above. The second portion 24', which connects the glenosphere 20 to the spacer 12, has a second opening for this connection, for example, by screwing it in place. This second opening interacts with a projection 28 of the glenosphere 20, which has an external thread.The portions are inclined relative to each other, for example by forming an angle between 5° and 30°, which allows the glenosphere 20 to be fixed in an inclined manner relative to the rod 4.

[0026] As with rod 4, spacer 12 is made of a biocompatible material with the longest possible lifespan, ensuring good distribution of mechanical stresses. Spacer 12 can be made entirely or partially of metal, plastic, or ceramic. It can also be made of several different materials, including a combination of the aforementioned materials.

[0027] In the examples described, the spacer 12 is an added piece on the rod 4. It could also be made in one piece with the latter and form one end of the rod 4.

[0028] The glenosphere 20 is illustrated on the Figures 10 and 11This glenosphere 20 can be spherical (a hemisphere, a portion of a sphere larger than a hemisphere, or a portion of a sphere extended by a cylindrical section). Its diameter can range from 30 to 46 millimeters. This diameter can, of course, fall outside this range. It can be made of ceramic. The type of ceramic used can be any type of ceramic known to those skilled in the art. For example, it could be alumina, zirconia, or a composite material. Since ceramic is a hard material, it can be used in "hard / hard" or "hard-soft" material pairs. In this second example, the "soft" material could be ultra-high-molecular-weight polyethylene (UHMWPE), polyetheretherketone (PEEK), PEKK (polyetheretherketone), or their derivatives.

[0029] The glenosphere 20 may be centered or not and may be lateralized if necessary (as seen above, particularly depending on the shape of the spacer 12). Centering means that a projection 28 allowing the glenosphere 20 to be attached 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. Eccentricity (for example, between 1 and 4 millimeters) means that a projection 28 allowing the glenosphere 20 to be attached to the spacer 12 does not extend from the center of the flat surface of the hemisphere. The projection 28 may include an external thread allowing the glenosphere 20 to be screwed 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.

[0030] The glenosphere 20 can be marked, for example by engraving, to indicate its diameter, whether it is centered or eccentric, or, if necessary, to inscribe a marking to identify the portion of the glenosphere 20 that must be placed angularly towards the superior position of the scapula, namely "UP" in the example shown on the figure 11 of the eccentric glenosphere.

[0031] The possibility of using a glenosphere 20 of variable diameter, centered or eccentric, allows for an additional possibility of 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 stem 4.

[0032] The glenoid implant 2 may also include a stabilizing component 30 (or stabilizing fork). This component, visible on its own on the figure 9 or mounted on stem 4 on the figures 1 to 3, can be attached to the rod 4, which therefore includes a fixing slot 42 for the stabilizing piece 30. More precisely, the fixing slot 42 can open into an internal thread in the rod 4. An intermediate piece including an external thread can then be screwed onto the rod 4 and lock the stabilizing piece 30.

[0033] This stabilizing piece 30 may include a locking end 32, advantageously drilled, for connecting the stabilizing piece 30 to the stem 4, and two stabilizing ends 34. These latter ends are arranged opposite each other so as to extend on either side of bone 6 (here, the scapula) when the glenoid implant 2 is inserted. It is possible for at least one stabilizing end 34 to bear against bone 6 when the glenoid implant 2 is inserted. In this case, it may have a flat surface extending parallel to bone 6 to provide support over a large surface area. The number and shape of the stabilizing ends 34 may vary.

[0034] The stabilizing piece 30 could also allow additional bone anchorage for the glenoid implant 2. At least one stabilizing end 34 (or the stabilizing end if there is only one) can in this case include a through hole for fixing it to the bone 6, for example by screwing and thus create an additional anchorage point.

[0035] As previously mentioned for other components, the stabilizer piece 30 is made of a biocompatible material, offering the longest possible lifespan and ensuring good stress absorption. It can, for example, be made of titanium alloy, stainless steel, cobalt-chromium alloy, or a polymer material.

[0036] There figure 12The illustration shows the rod 4 attached to a grasping and guiding tool 36. The latter includes a locking end 38 configured to collaborate with the groove 16 and the bore 14 in order to attach the rod 4 to the grasping and guiding tool 36 and to be able to place the latter in the cavity provided in the bone 6. The grasping and guiding tool 36 also includes a grasping end 40 of the assembly formed by the latter and the rod 4 by a surgeon.

[0037] 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 fitted with the stabilizing piece 30). This locking end 38 is advantageously hollow and partially tapped so as to allow the insertion of an intermediate piece 39 comprising at least one external thread, in order to lock the locking end 38 onto the rod 4 by screwing it in place (see figure 13 ).

[0038] The gripping end 40 is then attached to the locking end 38 (see figure 14 ) and fixed to the latter, for example by screwing them together, for example by a knurled head screw 44 visible on the Figures 12 And 15 .

[0039] The gripping end 40 includes a portion extending parallel to the shaft 4 when the latter is held by the gripping and guiding tool 36 and includes holes 46 that can be aligned with the through holes 18. These guide holes 46 allow a surgeon to be guided during the placement of the shaft 4. Indeed, the alignment allows the surgeon to know where to drill the bone 6 to find a through hole 18. To do this, the surgeon can position a guiding element 48, here cylindrical in shape, extending from the guide holes 46 and perpendicular to the shaft 4 and to the portion of the gripping end 40 bearing the guide holes 46 (see figure 15). This guide element 48 then comes to rest against the bone 6 and is advantageously hollow so as to allow the introduction of means for drilling the bone 6 and 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.

[0040] On the figure 15 A rod 4, carrying a stabilizing piece 30, can be seen already in place in a cavity formed in the thickness of bone 6. The grasping end 40 is positioned so as to align at least one guide hole 46 with a through hole 18 (not visible in this figure). A guide element 48 extends from a hole 46 and is pressed against bone 6.

[0041] As can be seen on the figure 4The 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 rotational capability for 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. On the figure 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 through hole 18 or another. List of references

[0042] 2: glenoid implant 4: stem 6: bone 8: anchoring screw 10: receiving surface 12: spacer 14: bore 16: groove 18: through holes 20: glenosphere 22, 22': first portions of the spacer 24, 24': second portions of the spacer 26: protrusion 28: projection 30: stabilizing piece 32: locking end 34: stabilizing end 36: grasping and guiding tool 38: locking end 39: intermediate piece 40: grasping end 42: fixing slot 44: knurled head screw 46: guide holes 48: guiding element A: longitudinal axis of the stem

Claims

1. Glenoid implant (2) of a reverse shoulder prosthesis, comprising an anchoring base for anchoring the implant to a bone formed by a stem (4) configured to extend within the thickness of the bone (6) from a glenoid cavity, the stem (4) comprising through-holes (18), and by anchoring screws (8) for anchoring the stem (4) configured to extend radially through the stem (4), through the through-holes (18), and the bone (6), when the glenoid implant (2) is implanted on the bone (6), characterised in that the stem (4) is formed of several parts removable relative to one another so as to be able to form a stem of variable length, for example between 40 and 120 millimetres.

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

3. Glenoid implant (2) according to any one of the preceding claims, wherein the stem (4) comprises a receiving surface (10) for receiving a spacer (12) for fastening the stem (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 cooperate 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 stem (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 fastening the spacer (12) to the stem (4) and a second portion (24, 24') for fastening the spacer (12) to the glenosphere (20), the first portion (22, 22') and the second portion (24, 24') being offset relative to one another.

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 one another.

7. Glenoid implant (2) according to any one of the preceding claims, further comprising a stabilising member (30) for stabilising 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, wherein the stabilising member (30) comprises two stabilising 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 comprising a glenoid implant (2) according to any one of claims 1 to 8.

10. Kit comprising a gripping and guiding tool (36) for a glenoid implant (2) according to any one of claims 1 to 8 and a glenoid implant (2) according to any one of claims 1 to 8, the gripping and guiding tool (36) comprising a locking end (38) for locking to the stem (4) and a gripping end (40), the gripping end (40) extending at least partly parallel to the stem (4) when the gripping and guiding tool (36) is fixed to the stem (4), the gripping end (40) comprising at least one guiding hole (46) for positioning the anchoring screws (8), the gripping and guiding tool (36) comprising at least one guiding element (48) for positioning the anchoring screws (8), removable relative to the gripping end (40) and capable of extending between the guiding hole (46) and a through-hole (18).

11. Kit according to claim 10, wherein the gripping end (40) is rotatable relative to the locking end (38).