ITMI20122177A1 - IMPROVING SHOULDER PROSTHESIS - Google Patents

Description

IMPROVED SHOULDER PROSTHESES

The present invention relates to an improved shoulder prosthesis.

The field of invention is that of prostheses used in orthopedic surgery for the reconstruction of the shoulder joint, that is the humeral bone segment whose head articulates with the glena.

Two important types of prostheses are used in shoulder surgery, namely:

- the standard prosthesis, also known as anatomic, in which the prosthesis faithfully reproduces the anatomy of the humeral bone, with the humeral head integral with the stem which is implanted in the diaphyseal canal of the humerus; the prosthesis is completed with the glenoid component, in turn fixed to the glena and on which the humeral head is articulated;

- the inverse prosthesis, once again composed of a humeral stem implanted in the diaphyseal canal of the humerus, but on the top of which the concave component is fixed which identifies the joint site of the humeral head and which, in this configuration of the prosthesis , Is attached to the glena.

The surgery of the shoulder prostheses described above involves, in both cases, the resection of the humeral head of the humerus to be prosthesized, in order to expose the diaphyseal canal, site of implantation of the humeral stem. The plane of this resection is in particular made with an angle, with respect to the anatomical axis of the humerus, which differs between standard prosthesis and inverse prosthesis. By way of example, in the standard system this angle is approximately 135 °, in the reverse it is approximately 150 °.

In the known technique, the choice of the angle of the resection plane constrains the type of standard or inverse implant to be used right from the start. Often, however, the surgeon finds himself in the need to change intraoperatively the indication of the initial type of prosthesis (for example a standard prosthesis), depending on the anatomical state of the patient (which, in the example considered, could make the type preferred of reverse shoulder prosthesis).

At present, the change in the type of surgery from standard shoulder prosthesis to reverse shoulder prosthesis requires changing the angle of the resection plan of the humerus head, which entails the need for a further resection operation. However, such an additional corrective intervention has the drawback of reducing the length of the bone and in any case represents an invasive operation for the patient, to the point that it is carried out only in cases of extreme necessity.

To this disadvantage is added that the prostheses of the known technique, as they are specifically dedicated to the standard or reverse type, make it necessary to have both instruments and the related prosthetic components, with greater risks of infection, dilation of surgical times, increase the costs of equipment and the need for storage of both types of prostheses.

The main purpose of the present invention is to provide a new shoulder prosthesis which, compared to traditional prostheses, offers the surgeon the possibility to choose in situ or intraoperatively the type of standard or inverse prosthesis to be used, without the need to make changes. to the resection plan for standard shoulder prostheses.

A further object of the invention is to avoid the need for additional surgical interventions on the humeral head, traditionally necessary to switch from the standard shoulder prosthesis type to that of reverse shoulder prosthesis.

Another purpose of the invention is to make it no longer necessary to have medicated prosthetic components, distinguished between standard and inverse prosthesis applications.

These and other purposes are achieved with the shoulder prosthesis, as characterized in claim 1. Preferred ways of carrying out the invention result from the remaining claims.

In relation to the known technique, the shoulder prosthesis of the invention offers the advantage of making the resection of the humeral head unambiguous, so as to allow the surgeon to choose the type of application, standard or reverse, directly at the moment of the act. surgical. In this way, the choice of the shoulder prosthesis to be applied can be made according to the anatomy found intraoperatively, without the need to correct the resection plan of the humeral head compared to that of a standard prosthesis.

In this way, the invention also makes it possible to avoid resorting to traditional invasive interventions, usually required when it is necessary to modify the type of intervention in relation to that initially envisaged.

Furthermore, thanks to the possibility of converting the prosthesis of the invention from the standard to the inverse type, the important advantage is also achieved that the different instruments for these different prostheses are no longer necessary, thus reducing the risk of infection. Surgical times have also decreased, all with lower equipment costs and without the need to provide for the storage of both types of prostheses.

These objects, advantages and characteristics result from the following description of a preferred way of making the prosthesis of the invention illustrated, by way of non-limiting example, in the figures of the attached drawings.

In them:

- figure 1 illustrates the standard type of shoulder prosthesis implant;

- figure 2 illustrates the type of reverse implant of shoulder prosthesis;

- Figures 3 to 6 illustrate the shoulder prosthesis of the invention, in its standard configuration;

- Figures 7 to 10 illustrate the shoulder prostheses of the invention, in its inverse configuration;

- figure 11 is a perspective view of the detail of the humeral stem of the prosthesis of the invention;

- Figures 12 and 13 illustrate the stem of Figure 11, in the standard and reverse applications of the shoulder prosthesis, respectively. The application of a standard shoulder prosthesis illustrated in figure 1 involves the insertion, in the diaphyseal canal of the humerus 2, of a stem 1, in turn provided with a humeral head 3 articulated on the glenum 4.

For this standard application, a resection is performed surgically on the anatomical humeral head according to the resection plane 5, whose axis 6 is inclined, with respect to axis 7 of humerus 2, by an angle Î ±, usually equal to 135 °.

In the inverse application of figure 2, the resection of the head of humerus 2 is performed on plane 10, defined by an inverse element 8, in turn articulated on the glenosphere 9. In this type of inverse application, the angle β which is formed between axis 11 of the aforementioned resection plane 10 and humeral axis 7 is usually about 150 °.

Traditionally, once the choice has been made, for example of the application of the standard shoulder prosthesis in figure 1, the possible passage to the inverse type of figure 2 involves the surgical modification of the resection plane, from that 5 with angle Î ± to that 10 with corner β. This modification therefore takes the form of an invasive surgery additional to the one previously performed, which reduces the amount of bone available to the implant.

The correction described above also has the drawback of requiring specific equipment, distinguished between standard and inverse shoulder prostheses, which are mutually incompatible.

To overcome these drawbacks, the prosthesis of the invention, as illustrated in figure 3, comprises a humeral stem 12 provided with a female proximal conical seat 13, intended to house a standard adapter 14. The latter is in particular provided with a male cone 15, which engages in operation inside the aforementioned seat 13. The adapter 14 also has a vice cone 16, protruding from the side of the humeral head 17 and suitable for engaging within a corresponding seat 18 of the same. A hole 19 is also provided for housing a screw (not shown) for fixing the adapter 14 to the stem 12, by engagement of the same screw within a corresponding threaded hole 20 provided in said seat 13 of the stem 12.

As shown in figure 4, in the humeral component of the standard prosthesis of the invention, as assembled, the axis 22 of the respective resection plane 21 forms, with the axis 23 of the stem 12 of the prosthesis, the angle Î ± (for example 135 °) required for standard applications.

In its inverse version, the shoulder prosthesis of the invention illustrated in figure 7 maintains the structure of the stem 12, provided with a female proximal conical seat 13 and a threaded hole 20.

In this version, on the aforementioned female seat 13 there is fixed an inverse adapter 25 formed by a discoidal body which, on the rod side 12, has a male vice cone 26 suitable for engaging inside the same female seat 13. On the opposite side, the same adapter 25 has a housing 27 for the reverse insert 28. Also on the reverse adapter 25 there is a seat 19 for the attachment screw in the threaded hole 20 of the stem 12.

The adapter 25 just described performs the function of fixing the reverse insert 28 to the stem 12, in particular by engaging the coupling 29 of this insert 28 inside the aforementioned housing 27. On its proximal side, the € ™ reverse insert 28 presents the seat 30 for the glenosphere 31 of figure 9.

As illustrated in figure 8, the inverse version of the shoulder prosthesis of the invention maintains the standard resection plane 21 inclined by the respective angle Î ± (for example of 135 °), but also has the inclination β of the plane 32 of inverse shoulder prosthesis (for example equal to 150 °) formed between the axis 23 of the stem 12 and the axis 33 of the inverse plane 32.

The humeral component of figures 7 and 8 is completed, in the reverse shoulder prosthesis illustrated in figures 9 and 10, with the glenosphere 31, in turn fixed to the anatomical glena by means of a plate 34 and screws 35.

As shown in particular by the aforementioned figure 8, the prosthesis of the invention lends itself to being converted from the standard to the inverse application, thanks to the conservation of the standard resection plane 21 even in the application of inverse shoulder prostheses with an inclined 32 plane. of the respective angle β. This result is made possible by the simple application, in the proximal conical seat 13 of the stem 12, of the inverse adapter 25 for fixing the respective inverse insert 28 which defines the aforementioned inverse plane 32.

Obviously the described conical coupling between the various components of the prosthesis of the invention can be replaced with equivalent means, however suitable for the same function.

In order to give primary stability to the prosthesis of the invention, in particular by interlocking the stem in the humeral diaphyseal canal, the proximal part 36 of the stem 12 of figure 11 has a flared configuration, ie increasing from the distal part 37 towards the proximal one 36.

The secondary stability of the prosthesis of the invention is instead obtained thanks to the presence, on the aforementioned proximal part 36 of the stem 12, of a portion 38 structured in the form of a cage, provided with slots 39 which allow the regrowth of the bone tissue, up to inhabit the internal space or the cavity 40 of the same stem 12.

The structure of the stem 12 of the invention, internally provided with the aforementioned cavity 40, allows to lodge in the latter a homologous bone (for example obtained from the humeral resection head), or of other material suitable for stimulating bone regrowth at the ™ inside the stem.

Claims (11)

CLAIMS 1. Shoulder prosthesis, characterized by the fact that it is equipped with means that allow it to be converted from the standard application to the inverse one, for preservation of the angle (Î ±) of the standard resection plane (21) even in the application of prostheses of reverse shoulder having a resection plane (32) inclined by the respective angle (β). 2. Prosthesis according to claim 1, characterized by the fact that said means consist of a humeral stem (12) provided with a proximal female seat (13) suitable for housing, interchangeably, adapters respectively (14) for the standard shoulder prosthesis application and (25) for reverse shoulder prosthesis application. Prosthesis according to claim 2, characterized in that the aforementioned adapter for reverse shoulder prosthesis (25) is oriented, on the stem side (12), according to the inclined (Î ±) plane (21) of standard shoulder prostheses and is provided, on the opposite side, with an insert (28) oriented according to the plane (32) with inclination (β) of the reverse shoulder prosthesis. 4. Prosthesis according to claim 3, characterized in that the aforementioned adapter (14) for standard shoulder prosthesis has, on the side of the stem (12), coupling means (15) in the female seat (13) of the same stem ( 12) and, on the opposite side, the means (16) for fixing the humeral head (17), in turn equipped with a corresponding seat (18) for said fixing means (16). 5. Prosthesis according to claim 4, characterized in that the aforementioned adapter (25) for reverse shoulder prosthesis has, on the stem side (12), coupling means (26) in the female seat (13) of the latter and , on the opposite side, a housing (27) for fixing the aforementioned inverse prosthesis insert (28). 6. Prosthesis according to claim 5, characterized in that said insert (28) is provided with a hook (29) for engagement in said housing (27). 7. Prosthesis according to claim 6, characterized in that said insert (28) has, on the proximal side, a seat (30) for the glenosphere (31) of an inverse shoulder prosthesis. 8. Prosthesis according to claim 7, characterized in that it has, in the standard version, a ring nut (24) on the humeral head (17) and, in the reverse version, the said glenosphere (31) articulated on the aforementioned insert (28). 9. Prosthesis according to one or more of the preceding claims, characterized in that said stem (12) has an internally hollow structure (40). 10. Prosthesis according to claim 9, characterized in that said structure of the stem (12) develops with a flared conformation towards the proximal part (36), so as to adapt to the shape of the humeral canal. 11. Prosthesis according to claim 10, characterized in that said proximal flared part (36) of the stem (12) is composed of a cage structure (38), provided with openings (39) suitable for forming bone interactions between the inside and the outside of the same stem (12).