Device, bone fixation screw and fixation system for fixation of a reverse shoulder prosthesis

Abstract

The device for fixation of a reverse shoulder prosthesis comprises a base plate (2) adapted to mate with the glenoid cavity, bounded at its bottom by a first, at least partially convex, surface (21), bounded at its top by a second, concave, surface (22) opposite the first surface, and bounded peripherally by a third, frusto-conical or cylindrical, surface (23), and a central pin (3) having an internal duct (5) projecting from the first surface, the internal duct (5) extending axially therethrough and having at least one major diameter (D1). The central pin has a first end (3a) connected to the base plate and a second, free end (3b) opposite the first end. The duct has a helical cavity (7) formed in an inner wall (5L) bounding the duct, the cavity opening toward the interior of the duct and extending along its entire length to provide fluid communication between the second surface of the base plate and the second end of the central pin. The inner duct has a second diameter (D1') smaller than the main diameter, and the helical cavity has a diameter (D4) larger than the main diameter of the inner duct.

Description

[Technical Field]

[0001] The present invention relates to a device for fixation of a reverse shoulder prosthesis, a bone fixation screw for use with the fixation device, and a system for fixation of a reverse shoulder prosthesis.

[0002] A conventional (or anatomical) shoulder prosthesis attempts to replicate and therefore mimic the normal anatomy of the shoulder joint: a polyethylene "cup" fits into a depression in the bone of the shoulder blade (the glenoid fossa), and a "ball" made of a biocompatible metallic material connects to the top of the arm bone (the humerus).

[0003] In a reverse prosthesis, the cup and ball are reversed: the ball (glenosphere) is fixed in the glenoid cavity and the cup is fixed to the upper end of the humerus.

[0004] Thus, the term reverse shoulder configuration refers to a total shoulder arthroplasty system that reverses the normal biomechanics between the scapular and humeral components: the joint mechanism is reversed, the glenoid cavity is replaced with a glenosphere, and the spherical surface of the humeral head is replaced with a concave polyethylene surface that interfaces with the glenosphere.

[0005] The device that is the subject of the present invention is used as a system for anchoring an implant in a glenoid cavity, in particular as a system for anchoring a base plate with a glenosphere attached. [Background technology]

[0006] Currently, several devices exist for fixation of reverse shoulder prostheses.

[0007] Some known types of devices include a base plate with a central pin that can be inserted into the glenoid cavity. The pin may be cylindrical and fit into a pre-formed hole in the glenoid cavity. In this case, the base plate is inserted into the glenoid cavity, and an additional central screw cannot be used to provide additional compression and stability to the implant.

[0008] Alternatively, the glenosphere support includes a screw integral to the base plate, which is screwed into the glenoid cavity.

[0009] This solution has the disadvantage that it does not allow the base plate to be positioned according to the planned orientation. The base plate is screwed in until it contacts the glenoid cavity. The base plate has four peripheral holes for inserting the connecting screws, arranged at 90° to each other. Because the holes are formed after the base plate is positioned, it is possible that the holes may overlap with areas of low bone or poor bone quality, resulting in an inability to securely fix the base plate to the glenoid cavity.

[0010] Additionally, these types of prostheses may have base plates with asymmetrical shims used to compensate for bone thickness deficiencies. Therefore, when the base plate is screwed down until it contacts the glenoid, the shims or wedges may not be positioned where they are needed, thus creating an inaccurate connection between the prosthesis and the abutment surface.

[0011] Another solution used in the prior art provides a base plate with a substantially cylindrical central pin. The pin has a central hole. After the base plate is inserted into the bone, and thus the pin is inserted into a pre-formed hole in the glenoid cavity, a screw is passed through the central cavity of the pin. The screw can rotate independently of the base plate and thread itself into the bone. This system, which includes modular screws and a central pin inserted after the base plate is inserted, has the disadvantage of including a pin with a central through-hole whose diameter is larger than the diameter of the screw thread to allow for screw insertion. Therefore, it is a bulky device and necessarily requires a good base bone implant with a wide thickness to accommodate pins of a certain diameter.

[0012] Finally, there is a further type of prosthesis, similar to that described above, which comprises a support base (base plate) that is substantially cylindrical and has a central pin bored therein.

[0013] Unlike the embodiment described above, in which the screws are inserted with the base plate already in place on the bone, the modular central screw can be inserted into the pin hole before the base plate is in place and impacted into the bone.

[0014] In this embodiment, the screws are actually inserted from the tip of the central pin (the pin inserted into the bone first) towards the base plate, rather than along the pins and through the base plate.

[0015] The drawback of such a solution is that the surgeon cannot decide whether to use a central screw or not based on the stability of the implant after the base plate has been inserted, and is forced to fix it by the central screw. Furthermore, in the case of a revision prosthesis, complications arise during the revision surgery, since the screw cannot be removed before removing the base plate. Summary of the Invention

[0016] SUMMARY OF THE INVENTION An object of the present invention is to overcome the drawbacks of the prior art.

[0017] In particular, the object of the present invention is to propose a device for fixation of a reverse shoulder prosthesis, which has pins of limited size so that they can be implanted even in situations of bone deficiency, and which allows the pins to be placed along the spines of the scapula to maximize the stability of the implant.

[0018] It is a further object of the present invention to create a device for fixation of a reverse shoulder prosthesis that has screws that are independent of the bearing base, so that the bearing base itself can be freely oriented to optimally position the peripheral screw seats and any corrective wedges or shims.

[0019] It is also an object of the present invention to provide an apparatus for fixation of a reverse shoulder prosthesis that allows for the insertion of screws through the base plate after impaction to determine if screws are required based on the stability of the implant after impaction.

[0020] It is a further object of the present invention to provide a device for fixation of a reverse shoulder prosthesis that allows the screws to be removed before removing the base plate in the case of a revision, thus simplifying removal of the implant.

[0021] A further object of the invention is to propose a bone fixation screw that can be used with the aforementioned fixation device and that allows it to be properly fixed in the shoulder joint.

[0022] It is a further object of the present invention to provide a system for fixating a reverse shoulder prosthesis that overcomes, among other things, the shortcomings of the prior art.

[0023] These and other objects and advantages are achieved by an apparatus for fixation of a reverse shoulder prosthesis as set forth in the appended claims. overview A first aspect of the present invention provides a device for fixation of a reverse shoulder prosthesis having a base plate bounded at its bottom by a first at least partially convex surface adapted to mate with the glenoid cavity, bounded at its top by a second concave surface opposite the first convex surface, and bounded at its periphery by a third frustoconical or cylindrical surface. A central pin protrudes from the first at least partially convex surface and includes a through internal axial duct. The central pin has a first end connected to the base plate and a second free end opposite the first end.

[0024] The internal axial duct has a helical cavity in the interior wall that bounds the duct itself, the cavity opening to the inside of the duct and extending along the entire length of the duct so as to place a first end of the cavity in fluid communication with the second end of the central pin.

[0025] Advantageously, the inner duct has a second diameter smaller than the main diameter. Preferably, the helical cavity has a diameter larger than the main diameter of the inner duct.

[0026] The helical cavity has a pitch and profile designed to mate with the pitch and profile of a thread that can be screwed into the duct.

[0027] The depth of the helical cavity is also equal to the thread height of the fixing screw.

[0028] The base plate has a central through hole formed in the pin that communicates with the duct inside the pin.

[0029] A first end of the pin is connected to the base plate and opens outwardly into the first concave surface through a hole therein, and a second free end of the central pin is axially opposite the first end and opens outwardly.

[0030] The internal duct has at least one threaded portion with a different pitch and height than the helical cavity, so that it can be coupled with a second screw that can be inserted through a first end of a central pin adapted to fixate the glenoid cavity.

[0031] The change in diameter of the duct occurs in an intermediate region between the second surface of the base plate and the second end of the central pin, and therefore in an intermediate region between the first and second ends of the central pin.

[0032] The duct has a larger main diameter extending between the base plate and the intermediate region and a smaller second diameter extending between the intermediate region and the second end of the central pin. The pin has a cylindrical shape and a corrugated outer surface.

[0033] The base plate has at least two through holes communicating the first at least partially convex surface with the second concave surface.

[0034] The first surface has an at least partially raised wedge-shaped portion.

[0035] In a second aspect, the present invention provides a bone fixation screw that can be inserted into a device for fixating a reverse shoulder prosthesis. The screw has a cylindrical body, a tip located at one end of the cylindrical body, a head located at a second end of the cylindrical body opposite the first end, and a thread extending helically along the entire axial extension of the cylindrical body. The head of the screw has an outer diameter that is larger than the outer diameter of the cylindrical body and smaller than the outer diameter of the thread.

[0036] The head has a cylindrical shape with no protrusions, and the head is connected to the cylindrical body by a tapered portion.

[0037] The tip of the screw has at least one notch with a sharp edge so that it taps when inserted, thus avoiding pre-tapping.

[0038] In a third aspect, the present invention provides a system for fixation of a reverse shoulder prosthesis, comprising a fixation device as described and claimed in the present invention and a locking screw as described and claimed in the present invention.

[0039] The fastening system requires that the helical cavity provided inside the duct of the pin has a pitch, profile and depth designed to mate with the pitch, profile and height of the threads of the fixing screw that can be screwed into the duct. [Brief explanation of the drawings]

[0040] The invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, which are provided by way of example only. [Figure 1] 1 shows a top perspective view of a device for fixating a reverse shoulder prosthesis according to the present invention and in a first configuration; [Figure 2] 1 shows a side view of the device that is the subject of the present invention, according to a second embodiment; [Figure 3] 1 shows a bottom perspective view of the device that is the subject of the present invention, according to a third embodiment; [Figure 4] 1 shows a side view of the device that is the subject of the present invention, according to a fourth embodiment; [Figure 5a] 1 shows a perspective view of a bone fixation screw according to the present invention that can be coupled to a device for fixating a reverse shoulder prosthesis according to the present invention; FIG. [Figure 5b] 1 shows a side view of a bone fixation screw according to the present invention that can be coupled to a device for fixating a reverse shoulder prosthesis according to the present invention; [Figure 6] 1 shows a cross-sectional side view of a system for fixation of a reverse shoulder prosthesis according to the present invention in a first illustrated configuration. [Figure 7] 10 shows a cross-sectional side view of a system for fixation of a reverse shoulder prosthesis according to the present invention in a third illustrated configuration. [Figure 8]1 shows a perspective view of a fully assembled reverse shoulder prosthesis on a fixation system that is the subject of the present invention; [Figure 9] FIG. 9 shows a cross-sectional side view of the prosthesis shown in FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0041] In the above figures, the device for fixation of a reverse shoulder prosthesis according to the invention is generally designated 1.

[0042] With particular reference to Figures 1 to 4, which are shown in detail below, the fixation device 1 comprises a base plate 2 and a pin 3 protruding centrally from the base plate 2.

[0043] The base plate is actually a base plate bounded at the bottom by an at least partially convex first surface 21 adapted to mate with the glenoid cavity, and bounded at the top by a second concave surface 22 opposite the first convex surface 21. The base plate 2 is bounded at the periphery or laterally by a frustoconical or cylindrical third surface 23, which may have a varying thickness depending on the required implant configuration. Two examples of the various thicknesses that the base plate may have, and therefore the heights that the third surface 23 may have, are shown in Figures 1 and 2, which differ primarily in the height of the third side surface 23 that bounds the base plate 2; i.e., the height in Figure 1 is lower than the height in Figure 2. These figures show a configuration including a third cylindrical side surface 23, but as mentioned above, this surface may also be frustoconical.

[0044] First surface 21 is at least partially convex, as shown in Figures 3 and 4, and can have a raised wedge-shaped portion 4 to accommodate as many alternative configurations as possible. This first surface 21 is actually the surface that interfaces with the glenoid cavity and can be fully convex (as seen in Figures 1 and 2), or it can have a partial (Figure 3) or full (Figure 4) protrusion specifically shaped according to the patient's anatomy, thereby correcting the course of the underside of base plate 2 to compensate for bone defects. The underside of the base plate (i.e., first surface 21 of the base plate) must fit perfectly into the surface of the glenoid cavity without any voids or protrusions that could affect the correct positioning of the implant and, therefore, its stability.

[0045] The central pin 3 is preferably cylindrical and projects from a first lower surface 21 of the base plate 2 along a straight longitudinal axis 3'.

[0046] The central pin 3 has a first end 3a or distal end connected to the base plate 2 and a second free end 3b or proximal end opposite the first end 3a.

[0047] The terms distal and proximal refer to the portions of the device that are furthest and closest, respectively, from the patient's body, particularly with reference to the patient's heart.

[0048] The fixation device is hollow in the center and therefore has an internal duct 5 extending through it along its entire axial extension 5a from the second surface 22 of the base plate 2 to the free end 3b of the pin 3 over the entire longitudinal extension of the device.

[0049] The duct 5 has a cylindrical cross section and a main internal diameter D1, which may be constant throughout the entire extension of the duct, or may taper to a second diameter D1' in an intermediate region along the extension of the duct 5. In the latter case, the inner duct 5 has a constant internal diameter equal to the main diameter D1 throughout substantially the entire extension of the duct itself, extending from the second surface 22 to an intermediate region 30 located between the first distal end 3a and the second proximal end 3b, and then slightly tapers to a second diameter D1' slightly smaller than the main diameter, which extends from the intermediate region 30 of varying diameter to approximately the second proximal end 3b of the pin 3 at a constant size. Thereafter, at the second proximal end 3b, the internal diameter of the duct 5 narrows further to define a diameter D2 smaller than the second diameter D1' of the duct 5.

[0050] The pins 3 can have a variety of lengths depending on the patient's anatomy and the shape of the bone into which they are inserted. The outer diameter of the pins 3 can also vary from device to device depending on the size of the patient's bone. However, because the present invention solves the problem of minimizing the size of the pins 3 so as to limit as much as possible the amount of bone that must be removed to place the fixation device, the preferred design will always be a fixation device with a pin 3 that has the smallest possible outer diameter that matches the size of the bone.

[0051] The base plate 2 has a central hole 20 in the pin 3, which communicates with the duct 5 inside the pin 3. The central hole 20 penetrates the thickness of the base plate 2 and communicates between a first surface 21 and a second surface 22 of the base plate 2.

[0052] The base plate also has a number of peripheral holes 2f arranged around the central hole 20 for the insertion of additional fixation screws 14 which can be used to better fixate the implant to the bone.

[0053] The holes are at least two, preferably four, through holes for connecting the first at least partially convex surface 21 and the second concave surface 22 .

[0054] A first distal end 3a of the pin 3 is connected to the base plate 2 and opens outwardly into a first concave surface 21 at the aforementioned hole 20, while a second proximal end 2b of the central pin 3, axially opposite the first distal end, is free and opens outwardly.

[0055] Externally, on the side wall 3L, the central pin 3 has a corrugated outer surface with a series of circumferential discharges 6 to increase friction with the hole formed in the bone into which the pin 3 is to be inserted.

[0056] Internally, the duct 5 has in its inner wall 5L a helical cavity 7 that opens towards the inside of the duct 5 and extends along the entire length of the duct 5. This helical cavity 7 puts the first end 3a in fluid communication with the second end 3b of the central pin 3.

[0057] The helical cavity 7 has a pitch, profile and depth or height designed to mate with the pitch, profile and height of the threads of a fixing screw 8 that can be screwed into the duct 5 .

[0058] In other words, the helical cavity 7 is the negative of the thread of a fixation screw 8 that can be inserted inside the duct 5 to fix the fixation device 1 to the scapula.

[0059] The smallest diameter D3 of the spiral cavity 7 is equal to the inner diameter of the duct (main diameter D1 or secondary diameter D1' depending on where the smallest diameter of the cavity 7 is evaluated), and the largest diameter D4 of the spiral cavity 7 is greater than the inner diameter of the duct 5. The main diameter D1 is greater than the secondary diameter D1' and smaller than the diameter D4 of the spiral cavity 7.

[0060] The fixation screw 8 shown in Figures 5a and 5b comprises a cylindrical body 81 having a tip 82 located at a proximal end 8' of the cylindrical body 81, a head 83 located at a second distal end 8'' of the cylindrical body opposite the first end 8', and a thread 84 extending helically along the entire axial extension 8a of the cylindrical body 81.

[0061] The head 83 has an outer diameter d 5 that is larger than the outer diameter d 6 of the cylindrical body 81 and smaller than the outer diameter d 7 of the threads 84 .

[0062] The head 83 has a cylindrical shape with no protrusions and is connected to the cylindrical body 81 by a tapered portion 85 .

[0063] The tip 82 of the screw has at least one notch 86 with a sharp edge that allows the screw to be inserted into the bone without pre-tapping the bone. The notch actually taps directly into the bone as it is inserted.

[0064] 6 and 7, the diameter d5 of the head 83 of the screw 8 is equal to the second inner diameter D1' of the interior of the duct 5. The outer diameter d6 of the cylindrical body 81 of the fixing screw 8 is equal to the smaller diameter D2 of the duct 5 installed at the second proximal end 3b of the pin 3. The outer diameter d7 of the thread 84 of the fixing screw 8 is equal to the maximum diameter D4 of the helical cavity 7 formed in the wall 5L of the duct 5 inside the pin 3.

[0065] The head 83 of the fixing screw 8 is provided with a housing 9 which is coupled to a fixing tool.

[0066] The length of the fixation screw 8 depends on the size and quality of the available portion of bone into which the screw is to be implanted.

[0067] Inside the pin 3, the duct 5 also has, on the side wall 5L, at least one threaded portion 10 with a pitch and height different from the pitch and height of the helical cavity 7, so that it can be coupled with a second screw 11 insertable into the inside of the pin 3 through a central hole 20 in the base plate 2. This second screw 11 is adapted to fix a glenosphere 12 to the fixation device 1.

[0068] The threaded portion 10 is arranged along the duct 5 and has a limited development confined to a portion of the duct 5 .

[0069] In the accompanying drawings, the threaded portion 10 is shown, by way of example only, in a portion of the duct 5 having a smaller second diameter D'.

[0070] An alternative configuration may be to provide this threaded portion 10 inside the first part of the duct 5 which has the largest main diameter D.

[0071] The present invention also provides a system 15 for fixating a reverse shoulder prosthesis, including the fixation devices and locking screws described herein.

[0072] The helical cavity 7 has a pitch and profile designed to mate with the pitch and profile of the threads 84 of the fixing screw 8 that can be screwed into the duct 5 of the pin 3. In addition to the pitch and profile, the height or depth of the helical cavity 7 also corresponds to the height of the threads 84 of the fixing screw 8, so that during insertion of the fixing screw 8 into the interior of the duct 5, the threads 83 of the fixing screw 8 fit perfectly into the wall 5L that delimits the duct 5 of the pin 3. This allows the pin 3 to have a limited lateral dimension compared to prior art pins.

[0073] The fixation system is used to provide fixation of the implant in the glenoid cavity, particularly for reverse shoulder arthroplasty.

[0074] 8 and 9 show the complete implant associated with the anchoring system that is the subject of the present invention.

[0075] The glenoid cavity is prepared to receive the base plate 2 of the fixation device by milling the articular surface and preparing a central hole through which the pin 3 will be inserted. While fitting the base plate 2 into the glenoid cavity, the surgeon can select the orientation of the base plate 2 by rotating the plate about the longitudinal axis 3' of the pin 3 so that the peripheral holes 2f are located where the bone is thicker and of good quality, and the protrusion or wedge-shaped portion 4 of the first convex surface 21, if present, is located in the bone defect or reduction.

[0076] The corrugations on the outer wall of the pin and the circumferential relief 6 allow for greater interference with the wall of the hole formed in the bone, allowing for better attachment of the pin 3 to the bone tissue.

[0077] If the surgeon deems it necessary based on implant stability or preoperative planning, a central locking screw may be used to provide additional stability and compressive strength. The central hole is prepared using a special guide and tip, and the hole depth is assessed using a depth gauge to determine the length of the screw to be used.

[0078] The central locking screw 8 is then inserted through the central hole 20 in the base plate 2 and into the interior of the scapula.

[0079] The threads 84 of the fixing screw 8 fit over and pass through the spiral cavity 7 formed in the wall 5L that bounds the duct 5 inside the pin 3. The fixing tool makes it possible to tighten the fixing screw 8 all the way.

[0080] The surgeon continues with the preparation of the peripheral holes 2f and the insertion of the respective screws 13. After the trial glenosphere has been placed, the final glenosphere 12 is implanted and the procedure can be completed by inserting a second screw 11 into the central hole 20 of the base plate 2 and screwing it into the threaded portion 10 present in the side wall 5L that delimits the duct 5 inside the pin 3.

[0081] The present invention overcomes the shortcomings encountered in the prior art by providing a device for fixation of a reverse shoulder prosthesis that has pins of reduced size for implantation in bone-poor situations, and that can be positioned along the spines of the scapula, maximizing implant stability.

[0082] Because the fixation screws are independent of the support base, the surgeon is free to orient the support base itself in a manner that he or she deems best suited to the patient's bony anatomy, regardless of the position of the peripheral screws and correction wedges or shims.

[0083] By inserting fixation screws through the baseplate after impaction, the surgeon has the opportunity to determine whether screws are necessary based on the stability of the implant, or whether screws are not necessary because the implant is already stable as is.

[0084] Inserting the locking screws after the baseplate has been fitted simplifies implant removal in the event of a revision, as the screws can be removed before removing the baseplate.

Claims

1. 1. A device for fixation of a reverse shoulder prosthesis, comprising: a base plate (2) bounded at the bottom by a first at least partially convex surface (21) adapted to connect with the glenoid cavity, bounded at the top by a second concave surface (22) opposite said first surface (21), and bounded at the periphery by a third frustoconical or cylindrical surface (23); a central pin (3) protruding from said first surface (21), said central pin (3) having at least one axially passing internal duct (5) with a main diameter (D1), said central pin (3) having a first end (3a) connected to said base plate (2) and a second free end (3b) opposite said first end (3a); the duct (5) has a spiral cavity (7) formed in an inner wall (5L) that bounds the duct (5), the cavity (7) opening toward the inside of the duct (5) and extending along the entire length of the duct (5) so as to fluidly connect the second surface (22) of the base plate (2) and the second end (3b) of the central pin (3); The device, wherein the internal duct (5) has a second diameter (D1') smaller than the main diameter (D1), and the helical cavity (7) has a diameter (D4) larger than the main diameter (D1) of the internal duct (5).

2. 2. The device according to claim 1, wherein the helical cavity (7) has a pitch and profile designed to be coupled with the pitch and profile of a fixing screw that can be screwed into the duct (5).

3. 3. The device according to claim 1 or 2, wherein the base plate (2) has a central hole (20) in the pin (3) that passes through the duct (5) inside the pin (3) and communicates with the duct (5), the first end (3a) of the pin (3) being connected to the base plate (2) and opening outwardly into the second concave surface (22) through the central hole (20), and the second end (3b) of the central pin (3) opening outwardly.

4. 3. The device according to claim 1, wherein the internal duct (5) has at least one threaded portion (10) having a pitch and height different from the pitch and height of the helical cavity (7), so that it can be coupled with a second screw (11) adapted to fixate the glenoid cavity (12), which can be fitted through the first end (3a) of the central pin (3).

5. 3. The device according to claim 1 or 2, wherein the internal duct (5) has an end located at the second end (3b) of the pin (3) and having a diameter (D2) smaller than the main diameter (D1) of the duct (5).

6. 3. The device according to claim 1, wherein the change in diameter of the duct (5) occurs in an intermediate region (30) between the second surface (22) of the base plate (2) and the second end (3b) of the central pin (3), the duct (5) having a larger main diameter (D1) extending in the section between the base plate (2) and the intermediate region (30) and a smaller second diameter (D1') extending in the section between the intermediate region (30) and the second end (3b) of the central pin (3).

7. 3. Device according to claim 1 or 2, characterized in that the pin (3) has a cylindrical shape and a corrugated outer surface (3L) provided with a plurality of circumferential discharges (6).

8. 3. The device according to claim 1 or 2, wherein the base plate (2) has at least two peripheral through holes (2f) connecting the first at least partially convex surface (21) with the second concave surface (22).

9. 3. The device according to claim 1 or 2, wherein the first surface (21) has an at least partially raised wedge-shaped portion (4).

10. 3. A bone fixation screw (8) insertable into a device for fixation of a reverse shoulder prosthesis according to claim 1 or 2, comprising a cylindrical body (81), a tip (82) located at one end (8') of the cylindrical body (81), a head (83) located at a second end (8'') of the cylindrical body opposite the first end (8'), and a thread (84) extending helically along the entire axial extension of the cylindrical body (81), the head (83) having an outer diameter (d5) greater than the outer diameter (d6) of the cylindrical body (81) and smaller than the outer diameter (d7) of the thread (84).

11. 11. The bone fixation screw according to claim 10, wherein the head (83) has a cylindrical shape without protrusions, and the head (83) is connected to the cylindrical body (81) by a tapered portion (85).

12. The fixation screw of claim 10, wherein said tip (82) has at least one notch (86) with a cutting edge.

13. A system for fixation of a reverse shoulder prosthesis, comprising a fixation device (1) according to claim 1 and a locking screw (8) according to claim 10.

14. 14. The fastening system according to claim 13, wherein the helical cavity (7) has a pitch, profile and depth designed to be coupled with the pitch, profile and height of the thread (84) of the fixing screw (8) that can be screwed into the duct (5).

15. 14. The anchoring system according to claim 13, wherein the head (83) of the fixing screw (8) has an outer diameter (d5) equal to the second diameter (D1') of the duct (5) inside the anchoring device (1).

16. The fixation system according to claim 13, wherein the outer diameter (d7) of the thread (84) of the fixation screw (8) is equal to the diameter (D4) of the helical cavity (7) of the fixation device (1).

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