Artificial shoulder joint

Abstract

The present invention relates to an artificial shoulder joint, the artificial shoulder joint comprising a metagrene element (2) or base plate, a pin (3) protruding from the metagrene element (2), a through hole (11) in the center of the metagrene element (2), at least one through hole (5) formed around the metagrene element (2) relative to the central through hole (11), a glenosphere element (12) on the opposite side of the pin (3) relative to the metagrene element (2), and a glenosphere element (12) received in the central through hole (11) of the metagrene element (2) and located in the central through hole (11). and a central compression screw (9) having a head that abuts the bottom of the glenosphere element (12), the central through hole (11) having a continuously threaded opening (11A) to receive an end of a safety screw (18) that passes through the glenosphere element (12), and the shoulder prosthesis further comprises a connector element (13) between the metagrene element (2) and the glenosphere element (12), the metagrene element (2) providing a seat (14) for receiving the connector element (13) that protrudes around the central through hole (11).

Description

Technical Field

[0001] The present invention relates to an artificial shoulder joint for the articulation of the humeral head relative to the opposing scapula.

[0002] Generally, the present invention applies to the field of orthopedic artificial joints for shoulder surgery.

Background Art

[0003] The anatomical shoulder joint, or scapulohumeral joint, substantially includes the humeral head formed as a spherical part and the articular cavity or glenoid fossa of the scapula, which is slightly elliptical and not very deep.

[0004] For proper shoulder function, in addition to the four muscles and tendons of the rotator cuff's glenosphere that keep the humeral head firmly close to the glenoid fossa and centered, providing internal and external rotational forces, the deltoid muscle, a strong muscle essential for the movement of raising the arm, plays an important role.

[0005] There are various situations where intervention of an artificial shoulder joint may be required.

[0006] The most common situation is arthritis, which involves the loss of the articular space between the humerus and the scapula, deformation of the articular surface, and formation of bone growths called osteophytes, compared to a normal shoulder, including the loss of the covering cartilage.

[0007] This may occur naturally with aging or may be caused by previous joint injuries, such as severe trauma or repeated shoulder dislocations.

[0008] There are also other situations, such as the onset of rheumatic diseases like rheumatoid arthritis and psoriatic arthritis, or the result of a fracture with insufficient healing.

[0009] When one of the above-mentioned conditions causes severe, almost uncontrollable pain and a significant loss of shoulder movement, thereby preventing the patient from performing daily activities, then relying on a prosthetic joint implant is the correct application.

[0010] There are many solutions currently available.

[0011] In particular, so-called "total" prostheses are available, which replace both joints, both the humeral head and the glenoid cavity of the scapula, or replace only the humeral side of the prosthesis, in which case it is technically called "hemiarthroplasty."

[0012] A "whole" prosthesis should be employed when both the humeral and glenoid components are degenerated or damaged.

[0013] According to the "anatomical" model, the component with the convex humeral head is connected to a scapular component with a concave surface or cup, which can be composed of a base called a metaglene, coupled to an insert, and as its name suggests, the structure of this component evokes the shape of the joint cavity.

[0014] Another "whole" prosthesis model that has achieved success in recent years is the so-called "reverse prosthesis," which consists of a metal base including a glenosphere. This model features a structure that is essentially the reverse of the anatomical structure of the shoulder, with a hemispherical convex component fixed to the scapula, while the concave surface for housing the hemisphere is on the humerus side.

[0015] An "anatomical" model is preferable because it does not involve damage to the rotator cuff muscles, and therefore, anatomical biomechanics and joint stability can still be ensured.

[0016] The "reverse" model is preferred, instead, in cases of rotator cuff injury due to irreparable damage, including the loss of anatomical biomechanics and joint stability to such an extent that conventional anatomical prostheses do not lead to improvement in the patient's clinical condition.

[0017] Even the materials used for artificial joints have undergone significant technological innovation in recent years, along with the development of coatings that are more biocompatible and focus on host tissues, including both bone and cartilage.

[0018] In this regard, for example, specific solutions are known, as described in the same applicant's European Patent Application Publication No. 1488764 and DEPUY's International Publication 01 / 47442.

[0019] Despite the existence of the above-mentioned solutions and updates based on prior art, there is still a perceived need to improve their characteristics in order to obtain better clinical outcomes.

[0020] More specifically, it is well known that assembling a glenosphere into an articular component is difficult due to the extreme reduction in available space. This decisively hinders the accuracy of its positioning, resulting in subsequent time loss, as well as the risk of inaccurate cone assembly and subsequent implant failure.

[0021] The underlying technical challenge of this invention is to provide an artificial shoulder joint that facilitates the surgeon's work by enabling the easy and precise assembly of a spherical body within the joint cavity using a reverse-type artificial joint implant.

[0022] Another objective of the present invention is to devise an artificial joint that can improve fixation between the artificial joint and the bone, and subsequently improve bone growth.

[0023] A further object of the present invention is also to provide a scaled-down solution for reducing the invasiveness of the artificial joint with respect to both the implantation process and the subsequent rehabilitation process. In other words, the scaling limitation must be maintained in both the vertical and horizontal directions.

[0024] Yet another object of the present invention is to take into account the natural anatomical differences that exist among several patients and thus to provide a specific number of options to the surgeon in order to ensure the best biomechanical solution.

[0025] Finally, an object of the present invention is to provide a solution suitable for both "anatomical" artificial joint models and "reverse" artificial joint models. SUMMARY OF THE INVENTION

[0026] The underlying idea of the solution of the present invention is to provide a particularly compact solution that exploits the compression action between the elements of the artificial joint that are assembled together and with respect to the anatomical seat in which the artificial joint is housed.

[0027] The above technical problem is solved by an artificial shoulder joint, which a metaglenoid element or base plate, and a pin protruding from the above metaglenoid element, and a through hole at the center of the above metaglenoid element, and at least one through hole formed around the metaglenoid element with respect to the through hole at the center above, and a glenosphere element on the opposite side of the above pin with respect to the above metaglenoid element, and the artificial shoulder joint further comprises a central compression screw housed in the through hole at the center of the above metaglenoid element and having a head that abuts against the bottom of the through hole at the center above, where the through hole at the center above has an opening continuously threaded so as to receive the end of a safety screw passing through the glenosphere element, the central compression screw, and A connector element (13) between a metaglenoid element (2) and a glenosphere element (12), the metaglenoid element (2) providing a seat (14) for accommodating the connector element (13) that protrudes around the through-hole (11) at the center, comprising the connector element (13).

[0028] As an advantage, the solution of the present invention enables greater compression by means of a central compression screw that can be adjusted to different lengths as needed, and thus enables primary stability of the implant.

[0029] Preferably, the connector element between the metaglenoid element and the glenosphere element is also incorporated between the elements.

[0030] Also preferably, the seat for accommodating the connector element is formed as a single part that protrudes around the through-hole at the center.

[0031] Also, the connector element includes a conical portion, and the connecting seat is formed with several serrated portions that are angularly spaced from each other and project coronally from the surface of the base plate facing the surface of the glenosphere.

[0032] A part of the connector element is securely engaged with the glenosphere element fixed by the insertion of the safety screw.

[0033] Also, the connector element can be connected to the glenosphere element by a connecting portion having an axial dimension configured to generate an offset of the center of rotation of the glenosphere (12) included between 1 mm and 10 mm.

[0034] According to a preferred embodiment, the pin is removable and constrained by a protrusion of the base plate. Alternatively, the base plate and the pin are made as a single part, but the through-hole at the center completely penetrates them.

[0035] Each of the above-mentioned Metagrane elements has an axis (AA) that is inclined with respect to the central axis (XX), and multiple through holes for accommodating surrounding fixing screws are arranged around the central through hole.

[0036] It should also be noted that a locking element, which forms a closure after the insertion of the fixing screw, is attached to the opening of the through hole formed around the surrounding fixing screw. This fixing screw preferably has a spherical head, as shown in the embodiment.

[0037] The locking element is a disc with at least one screwdriver around its circumference and a hemispherical projection, and the head of the fixing screw instead has a frustoconical seat for accommodating the hemispherical projection. In the shown embodiment, locking is ensured by the fact that the axis of the frustoconical head of the fixing screw always passes through the center of the locking element and that this coincides with the center of the spherical head of the fixing screw.

[0038] The base plate of the solution of the present invention is smaller in dimensions than known solutions, for example, having a substantially cylindrical body and a diameter of 25 mm or less.

[0039] Clearly, this does not prevent the same solution described here from being applied to base plates with larger diameters.

[0040] Furthermore, the base plate includes a trabecular structure or a surface coating layer on a surface configured to contact the bone.

[0041] The artificial joint of the present invention can be configured to be convertible, and a central through-hole is further configured to accommodate a liner insert according to the anatomical configuration.

[0042] Therefore, in this anatomical configuration, the liner insert is assembled on the opposite side of the base plate pins, instead of the glenosphere element and connector element.

[0043] Further features and advantages will become apparent from the following detailed description of preferred but non-exclusive embodiments of the artificial shoulder joint according to the present invention, with reference to the attached drawings given by non-limiting examples. [Brief explanation of the drawing]

[0044] [Figure 1] This shows an exploded view of an artificial shoulder joint according to the first embodiment of the present invention. [Figure 2A] Figure 1 shows a detailed embodiment of the artificial shoulder joint. [Figure 2B] Figure 1 shows a detailed embodiment of the artificial shoulder joint. [Figure 3] This shows the artificial shoulder joint according to the present invention, with the assembled seat obtained in the glenoid cavity. [Figure 4] This shows the artificial shoulder joint according to the present invention, with the assembled seat obtained in the glenoid cavity. [Figure 5] Figure 1 shows a cross-sectional view. [Figure 6] Another cross-sectional view is shown in Figure 1. [Figure 7] Figure 4 shows the details. [Figure 8] Another cross-sectional view of Figure 1 with a locking element is shown. [Figure 9] Figure 6 shows a perspective view of the locking element. [Figure 10] This shows an embodiment of the coupling mode for the substantially hemispherical elements of the artificial shoulder joint according to the present invention. [Figure 10D] Figure 8 shows the details. [Figure 11] This figure shows a specific example of a first embodiment of the coupling mode between a connector element and a Metaglen element in an artificial shoulder joint according to the present invention. [Figure 12A] This shows a perspective view of a second embodiment of the coupling mode between a connector element and a Metaglen element in an artificial shoulder joint according to the present invention. [Figure 12B] This shows a perspective view of a second embodiment of the coupling mode between a connector element and a Metaglen element in an artificial shoulder joint according to the present invention. [Figure 13] A cross-sectional view of the artificial shoulder joint according to the present invention, equipped with a safety screw, is shown. [Figure 14A] The present invention illustrates connector elements having different connection parts. [Figure 14B] The present invention illustrates connector elements having different connection parts. [Figure 14C] The present invention illustrates connector elements having different connection parts. [Figure 15] A perspective view of the reverse-type artificial joint according to the present invention is shown. [Figure 16A] This illustrates the modification process for the artificial shoulder joint according to the present invention, between the reverse configuration and the anatomical configuration. [Figure 16B] This illustrates the modification process for the artificial shoulder joint according to the present invention, between the reverse configuration and the anatomical configuration. [Modes for carrying out the invention]

[0045] Referring to the attached drawings, a first embodiment of the artificial shoulder joint is shown in general and schematic in 1, manufactured in accordance with the present invention, and for brevity, is defined below by artificial joint 1 and artificial joint 1' in the alternative embodiment.

[0046] Specifically, so-called reverse-type artificial joints are shown herein, but the present invention also applies to so-called anatomical artificial joints, as will become clear below.

[0047] In particular, the artificial joint 1 or 1' includes an intermediate metagrain element 2. This element 2 can represent a so-called artificial joint baseplate by itself, or it can work in conjunction with a pin 3 or peg of an intra-articular bone implant.

[0048] As will be seen in more detail below, in order to have an artificial joint system suitable even in cases of bone defects, baseplate 2 is also made in a so-called extended version, available in a range of configurations. This makes it possible to restore various types of bone defects in the glenoid fossa and restore an optimal state in terms of both bone reconstruction and tissue tension.

[0049] The pin 3, which actually protrudes from the Metagrane element 2, is attached to the base of the Metagrane element 2, which is rotated toward the joint cavity.

[0050] The Metagren element 2 is a roughly cylindrical element that, depending on whether it is an anatomical or reverse prosthesis, is positioned on the glenoid cavity or humerus together with the associated pin 3. Generally, the pin 3 is embedded by interfering into the combined seat obtained in the glenoid cavity, screwing it in, or fixing it with cement, as seen in Figures 3 and 4.

[0051] As seen in Figures 2A and 2B, the Metagrane element 2 and pin 3 can be detachably mounted (Figure 2A) or form a single monolithic element as a single component (Figure 2B). In the first case, the Metagrane element 2 is provided with a projection 3A to which the pin 3 is fixed, while in the second case, the mounting process between the two components is clearly not required, and conversely, the pin 3 represents the projection of element 2 itself.

[0052] In the embodiment shown in Figure 2A, the coupling is preferably achieved by a Morse cone type conical coupling, but this does not prevent the use of different types of couplings. In the case of modularity between the Metagrane element 2 and the pins 3, all base plates 2 (including those with additional reinforcements) can be coupled to all pins 3 (of different lengths).

[0053] As an advantage, with respect to pin 3 currently used in the SMR MB TT artificial joint system (an acronym for Shoulder Modular Replacement Metal Back Trabecular Titanium), the dimensions of pin 3 as described herein are significantly reduced by the adoption of a connector element and its housing seat, which makes it possible to reduce the number of required fixing parts (for example: from a diameter of 9.3 mm in the single-piece version to a diameter of φ11.37 mm in the modular version).

[0054] In contrast, if the two components 2 and 3 are separable from each other, different metagrain elements 2 can be associated with pins 3 having different lengths, thus reducing the number of different elements that need to be manufactured.

[0055] Furthermore, the Metagrane element 2 can provide a surface coating 22, particularly on the surface that comes into contact with bone. This surface coating 22 can be made, for example, of trabecular titanium.

[0056] The body of Metagrene 2 is provided with a through hole 11 located in the center and actually coaxially positioned along the main spindle XX, along with the protruding portion 3A of Metagrene 2, or in any case, the pin 3.

[0057] The central compression screw 9 passes through the Metagrane elements 2 and the pins 3 protruding from these elements 2, 3 until it is housed in the through hole 11 and embedded by screwing into the articular cavity. The central compression screw 9 has a head 10 with a hexagonal wrench seat or a similarly shaped recessed seat, which is screwed in with a special compound wrench.

[0058] The head 10 of the central compression screw 9 abuts against the bottom of the through hole 11, as shown in the cross-section of Figure 5. The bottom of the through hole 11 has a diameter slightly narrower than the diameter of the through hole 11 itself.

[0059] The opening 11A of the central through hole 11 is screwed into at least one continuum 18 to accommodate the threaded end 24 of the further safety screws 25 discussed below.

[0060] The central compression screw 9 can have different lengths as appropriate. The central compression screw 9 enables optimal bone integration, which allows the implant of pin 3 in the joint cavity to be fixed.

[0061] Furthermore, if the Metagrane elements 2 and pin 3 are separable from each other, the screw 9 works in cooperation with these elements 2 and 3 to prevent their undesirable disconnection. This also generates beneficial compression between the entire artificial joint implant and the bone.

[0062] Around the central through-hole 11, several seating areas 5 are provided to accommodate the surrounding / left and right fixing screws 4.

[0063] In effect, the Metagrane element 2 and associated pin 3 are stabilized and implant retention is increased with the help of at least one peripheral fixing screw 4 inserted into a corresponding through-hole seat 5 provided in the body of the Metagrane 2. In a preferred embodiment, the screw 4 has a spherical head that can be suitably oriented in different directions.

[0064] Multiple through-hole seat portions 5 are provided for the surrounding / left and right fixing screws 4.

[0065] Although four through-hole seat portions 5 are provided, their number may be small or large depending on the possibility of forming them around the central through-hole 11.

[0066] Each seat portion 5 has a countersunkand threaded insertion portion that accommodates the corresponding spherical head of the fixing screw 4 by screwing it in.

[0067] In this embodiment illustrated in the attached drawings, four fixing screws 4 are provided arranged in a cross shape around a substantially central through hole 11.

[0068] The fixing screw 4 may have stems of different lengths and diameters, as appropriate.

[0069] As can be seen in the drawings, these fixing screws 4 are extended along axes that branch from each other when embedded. More specifically, as shown in the example in Figure 7, each screw 4 extends along axis AA inclined with respect to the principal axis XX of the Metagrane element 2, and with an inclination angle that generally follows the concave shape of each housing seat 5, as well as the size of the fixing screw 4 itself, with an amplitude α.

[0070] Axis AA is actually the axis of hole 5, which is inclined with respect to the central axis XX of the metagrain element (2).

[0071] Artificial joint elements, each having at least one fixing screw 4, are shown in particular in Figures 7 and 8.

[0072] The fixing screws 4, when simply inserted according to the angle of the corresponding pilot hole, act by compression but without allowing rotation due to the load on each fixing screw 4 around its own hole 5, which obviously presupposes that this rotation is within a range permissible by the shape of the rear joint element 2.

[0073] The present invention also provides a device for preventing the screws 4 from rotating about their own axes after they have been embedded. As shown in Figure 8, a removable locking element 7 has been devised, which is schematically shown in Figure 9 in a preferred embodiment. Furthermore, as shown in Figure 7, the locking element 7 allows the fixing screws 4 to be inserted at different angles, according to a range of angles contained within the opening cone α.

[0074] The locking element 7 is, in fact, a locking cap that resembles the head of a screw alone, having at least one circumferential screwdriver 7B. The element 7 has a hex wrench seat and a hemispherical projection 7A on the opposite side.

[0075] Each screw 4 has a frustoconical seat 8 that accommodates the hemispherical projection 7A of the locking element 7.

[0076] In effect, the locking element 7 is screwed into the female thread of the hole 5 after the corresponding fixing screw 4 has already been inserted and screwed in, and can be fixed as a cap over the opening of the hole 5 by one or more rotations of the locking element 7. The projection 7A is housed in the frustoconical seat of the head of the screw 4. However, this does not prevent the locking element 7 from being provided in other ways, such that it can only be inserted into the opening of the hole 5 by pressure.

[0077] The presence of the locking element 7 prevents the fixing screw 4 from potentially releasing during rotation due to friction caused by the contact pressure between the hemispherical surface 7A of the locking element 7 and the frustoconical surface of the seat on the head of the fixing screw 4.

[0078] The fact that the locking element 7 has the same shape as the head of the fixing screw 4, regardless of the stem, makes it possible to create a standardized shape for the locking element 7.

[0079] The structure of the artificial shoulder joint 1 also includes a Glenosphere element 12 assembled on a Metagrane element 2 at the opposite position of the pin 3.

[0080] The embodiments shown in Figures 1 to 14C and Figure 16A illustrate an inverted type artificial joint 1, while Figures 15 and 16B relate to an anatomical artificial joint.

[0081] In the case of a reverse-type artificial joint, the glenosphere element 12 includes a substantially hemispherical element 12A called a glenosphere 12A and a connector element 13 having an annular body, through which the glenosphere 12A is connected to the metataglen element 2.

[0082] An advantage is that the connector element 13 comprises two parts 15 and 19 and is incorporated between the Glenosphere and the base plate.

[0083] The Glenosphere 12A and the connector element 13 are preferably joined first by secure engagement, preferably conical, more preferably with a male cone in the Glenosphere 12A and a female cone in the connector element 13, as shown in Figure 10 and in detail in Figure 10D, or also in Figure 13, but the reverse is also possible, in which case they are joined by a screw connection, which will be discussed later.

[0084] Such embodiments enable the easy connection of the entire artificial joint structure.

[0085] The connection between the connector element 13 and the Metagrane element 2 or base plate is instead made between the connector element 13 and a connecting seat 14 of the Metagrane element 2, which is configured to accommodate a portion 15 of the connector element 13 and is formed around a through hole 11 in the center of the base plate 2. This seat 14 is formed to project substantially toward the Glenosphere element (12), is angularly spaced apart from one another, and is defined and bounded by several serrated portions 28 that project crown-like from the surface of the base plate facing the surface of the Glenosphere 12A.

[0086] More specifically, according to the first embodiment shown in Figure 11, the connector element 13 includes an annular edge portion 19 that is coaxial with the conical portion 15.

[0087] The connection seat portion 14 of the base plate has the shape of a cone-tapered recess, and the cone portion 15 is configured for a cone connection between the male cone on the connector element 13 and the female cone 14 of the base plate 2.

[0088] The separate serrated portions 28 that form the crown shape of the female seat portion 14 are obtained by a single rotational step and are subsequently trimmed, so that they connect with the conical portion 15 of the connector 13 in millimeter increments, thus defining the connection with particular precision.

[0089] The conical portion 15 is fully incorporated into the seat portion 14, while the annular edge portion 19 accommodates the conical portion of the Glenosphere until it is fully incorporated by the Glenosphere element 12.

[0090] Therefore, the connector 13 is nested between the two metaglen elements 2 and the glenosphere element 12.

[0091] Since the entire connection between the seat portion 14 of the Metagrane element 2 and the conical portion 15 of the connector element 13 is within the dimensions of the Metagrane element 2, the possibility of interference with surrounding soft tissue can be avoided.

[0092] According to an alternative embodiment, different portions can be provided for secure engagement between the metagrain element 2 and the connector element 13.

[0093] More specifically, in exemplary embodiments illustrated in two drawings, Figures 12A and 12B, several tabs 16 may be provided, which are angularly spaced from and protruding from the connector element 13. These tabs 16 are intended to engage with corresponding slots 17 provided on the outer circumferential surface 6 of the base plate element 2. In the example illustrated herein for index purposes only, the number of these tabs 16 is four.

[0094] This solution is clearly an alternative to the previous one, as it requires inserting the four tabs 16 of the connector element 13 in "in phase" with the four slots 17 of the Metagrane element 2, and is therefore more difficult to assemble during the surgical procedure compared to the previous solution, as it requires the introduction of screws at that time.

[0095] This does not explicitly prevent the use of different numbers of tabs 16 and slots 17, or the resulting use of different types of secure engagement.

[0096] The first embodiment, shown as an example in Figure 11, allows for the "orientation" of the structure formed by the glenosphere 12A and connector 13 during the insertion process, influencing everything once the optimal position is found for the surgeon. Not all glenospheres need to be symmetrical, but some have asymmetry that determines the optimal implantation position. In many cases, the first embodiment is necessary.

[0097] Therefore, with respect to this requirement, the first embodiment, which does not have a forced insertion direction, is preferred.

[0098] Conversely, in the alternative embodiments shown in Figures 12A and 12B, the phase is maintained by the presence of the connector 13 with the tab 16, so it is necessary to insert the connector first and then the Glenosphere 12A, thus introducing an additional step.

[0099] In other words, the first embodiment has the advantage that the connector 13 can be pre-assembled into the Grenosphere 12A, and the assembly can be embedded later while allowing for position adjustment.

[0100] This embodiment is often considered by surgeons to facilitate adjustment and implantation.

[0101] Furthermore, as can be seen in the cross-sectional view of Figure 13, the artificial joint 1 is equipped with safety screws 25 configured to keep all elements of the artificial joint 1 itself interconnected, except for pin 3, which may have a conical connection (if it is not a single piece). However, pin 3 ensures further reinforcement of the connection.

[0102] The safety screw 25 penetrates the Glenosphere 12A and is inserted into the central hole 23, which is actually coaxial with the hole 11 in the base plate. The screw has a stem 25 with a threaded end 24 that screw-in engages with the female thread 18 of the opening 11A of the hole 11 in the base plate, thus maintaining the packing between all components of the artificial joint 1, except for the pin 3.

[0103] While there are clear anatomical similarities among patients requiring prosthesis implantation, it is also well known that several natural anatomical differences exist that must be considered in order to perform optimal shoulder prosthesis implantation. For each patient, it may be necessary to alter the center of rotation of the glenosphere to properly tension the soft tissues, or to reposition it to a more advantageous location to favor the proper biomechanics of the prosthesis (i.e., the medialized glenoid fossa).

[0104] In this regard, it is preferable to have the possibility of positioning the artificial joint 1, particularly the glenosphere element 12, in different ways in different patients.

[0105] More specifically, the artificial joint 1 according to this disclosure makes it possible to position the glenosphere 12A axially, i.e., laterally, relative to the metataglen element 2, and to ensure different axial offsets. This makes it possible to implant an artificial joint in which the tissue is always properly tensioned.

[0106] This possibility is provided by the devices illustrated in Figures 14A to 14C, which bring about a change in the configuration of the connector element 13, more specifically, in the portion 19 of this element intended for coupling with the Glenosphere.

[0107] To achieve this, the connection portion 19 of the connector element 13 is modified in height while maintaining its other characteristics.

[0108] In other words, the same connector element 13 is used, except for the axial dimension of this connection portion 19, and the height of this connection portion 19 is configured to produce an axial offset of the rotation center of the grenosphere 12A, preferably between 1 mm and 10 mm. As an example, connector elements 13 with axial dimensions varying between 3 mm and 6 mm are shown in Figures 14A, 14B, and 14C.

[0109] In an alternative embodiment illustrated in Figure 15, the artificial joint according to this disclosure can be configured as an anatomical artificial joint 1' by the same interconnection and fixation solutions between its components.

[0110] In the anatomical prosthesis 1' in Figure 15, there is a metagrane element 2' or baseplate, which is always intended to be inserted into the articular cavity but is coupled to the liner insert 12B.

[0111] The liner insert 12B is molded to fit the metagrain element 2' of the anatomical prosthesis 1', which is structurally different from that of the previous exemplary embodiment.

[0112] The liner insert 12B has a protruding portion formed by a pair of elastic claws 20 that engage with a central hole 11' of the base plate 2, which can accommodate a central compression screw 9. The elastic claws 20 are equipped with small projections 21 that are elastically inserted into an annular cavity 22 obtained at the opening of the central hole 11' to ensure a secure bond of the liner insert 12B in the metagrane element 2'.

[0113] The liner insert 12B is configured to close the metagrane element 2 at the top and to distribute the pressure applied to the entire contact surface with the artificial joint 1' in the best possible way.

[0114] The artificial joint 1' is implanted in an anatomical configuration, and later, at a certain point in the patient's life, deterioration of the rotator cuff may occur, suggesting conversion to a reverse-type artificial joint 1, as in the previous exemplary embodiment.

[0115] In other words, as can be seen in Figures 16A and 16B, the artificial joints 1 and 1' are configured to be convertible, and therefore it is possible to convert the anatomical artificial joint 1' into the reverse artificial joint 1.

[0116] In particular, the liner insert 12B can be removed and the connector element 13 can be added to the base plate 2', which allows the Grenosphere element 12 to be connected by safety screws 25.

[0117] An advantage of the present invention is that it is possible to improve the fixation between the artificial joints 1, 1' and the bone, and subsequently bone growth is also improved.

[0118] As a result, the dimensions of the Metagrane element 2 and pin 3 can be reduced. This brings beneficial effects to the implant and rehabilitation processes.

[0119] Specifically, the advantages of the present invention, compared to the prior art, are that the connector element has a housing seat, eliminating the need for extra pins, and thus making it possible to reduce the diameter of the metaglen by compressing everything toward the center of the artificial joint.

[0120] Furthermore, an advantage of this invention is that it is particularly practical for surgeons who have found it possible to manipulate easily interconnected components without requiring significant visual effort during complex surgical procedures in hard-to-reach areas.

[0121] Finally, as an advantage, the present invention can be modified and adapted according to the specific needs of the patient.

[0122] Those skilled in the art will understand that the embodiments presented may be further modified and transformed according to specific and incidental needs, as defined by the following claims, all of which fall within the scope of the protection of the present invention.

[0123] For example, the characteristics described for reverse prostheses, which do not exhibit technical defects in anatomical prostheses, can be interpreted without exceeding the scope of the protection claimed.

Claims

1. An artificial shoulder joint, wherein the artificial shoulder joint is Metagrain element or base plate, A pin protruding from the aforementioned metagrane element or base plate, The through hole in the center of the aforementioned metaglen element or base plate, With respect to the central through hole, at least one through hole formed around the metaglen element or base plate, The system comprises a Glenosphere element located on the opposite side of the pin from the Metagrane element or base plate, The aforementioned artificial shoulder joint further, A central compression screw, which is housed in a through hole in the center of the metagrain element or base plate and has a head that abuts the bottom of the central through hole, wherein the central through hole has an opening that receives the threaded end of a safety screw passing through the Glenosphere element and is threaded in a continuous manner to engage with the screw, An artificial shoulder joint comprising: a connector element between the metagrain element or base plate and the glenosphere element, wherein the metagrain element or base plate provides a seat for housing the connector element, the seat protruding around the connector element.

2. The artificial shoulder joint according to claim 1, wherein the connector element is incorporated between the metagrain element or base plate and the glenosphere element, and the seat portion is formed as a single part protruding around the central through hole.

3. The artificial shoulder joint according to claim 1 or 2, wherein the connector element includes a frustoconical portion, and the seat portion is formed having several serrated portions spaced apart from each other in the circumferential direction of the connector element, the serrated portions projecting in a crown-like manner from the surface of the Metagrane element or base plate facing the surface of the Glenosphere element.

4. The artificial shoulder joint according to any one of claims 1 to 3, wherein a portion of the connector element is securely engaged with the glenosphere element, which is fixed by the insertion of the safety screw.

5. The connector element may be connected to the glenosphere element by a connecting portion having an axial dimension configured to generate an axial displacement of the rotation center of the glenosphere element. The artificial shoulder joint according to any one of claims 1 to 4, wherein the axial displacement is between 1 mm and 10 mm.

6. The artificial shoulder joint according to any one of claims 1 to 5, wherein the pin is removable and constrained to a projection of the Metagrane element or base plate.

7. The artificial shoulder joint according to any one of claims 1 to 6, wherein a plurality of through holes, each having an axis inclined with respect to the central axis of the metagrain element or base plate, are provided around the central through hole to accommodate surrounding fixing screws.

8. The artificial shoulder joint according to any one of claims 1 to 7, wherein the safety screw is inserted through the glenosphere element having a threaded end that engages with a threaded opening in a through hole in the center of the metagrain element or base plate.

9. The artificial shoulder joint according to any one of claims 1 to 8, wherein the metagrain element or base plate and the pin are made from a single component.

10. The artificial shoulder joint according to claim 7, wherein a locking element that forms a closing portion after the insertion of the fixing screw is attached to the opening of a through hole formed around it.

11. The artificial shoulder joint according to claim 10, wherein the locking element comprises a hemispherical projection, and the head of the fixing screw comprises a frustoconical seat for accommodating the hemispherical projection.

12. The artificial shoulder joint according to any one of claims 1 to 11, wherein the metagrain element or base plate has a substantially cylindrical body and a diameter of 25 mm or less.

13. The artificial shoulder joint according to any one of claims 1 to 12, wherein the metagrain element or base plate includes a columnar structure or a surface coating layer on a surface configured to contact bone.

14. The artificial shoulder joint according to any one of claims 1 to 13, wherein the artificial shoulder joint is configured to be convertible between an anatomical prosthesis and a reverse prosthesis, and a central through-hole is further configured to accommodate the glenosphere element or liner insert according to the anatomical configuration.

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