EP2934396A1

EP2934396A1 - Improved shoulder prosthesis

Info

Publication number: EP2934396A1
Application number: EP13717850.5A
Authority: EP
Inventors: Henry KOOPMANN
Original assignee: Permedica SpA
Current assignee: Permedica SpA
Priority date: 2012-12-19
Filing date: 2013-03-08
Publication date: 2015-10-28
Also published as: ITMI20122177A1; WO2014096912A1

Abstract

A shoulder prosthesis, provided with a humeral stem (12) having a proximal female seat (13) suitable for interchangeably housing adaptors for the standard application of the shoulder prosthesis (14) and reverse application of the shoulder prosthesis (25), respectively. In this way, the shoulder prosthesis of the invention can be converted from the standard application to the reverse application, by maintaining the angle (a) of the standard resection plane (21) also in the reverse application of the shoulder prosthesis with the resection plane (32) tilted by the respective angle (β). With respect to the known art, the shoulder prosthesis of the invention offers the advantage of making the resection of the humeral head univocal, in order to allow surgeons to choose the type of application, standard or reverse, directly at the moment of surgery. In this way, the choice of shoulder prosthesis to be applied can be made in relation to the anatomical state observed during surgery, without having to correct the resection plane of the humeral head with respect to that of the standard prosthesis.

Description

IMPROVED SHOULDER PROSTHESIS

The present invention relates to an improved shoulder prosthesis.

The field of the invention relates to prostheses used in orthopedic surgery for reconstructing the shoulder joint, i.e. the humeral bone segment whose head is articulated with the glenoid.

In shoulder surgery, two important types of prosthesis are used:

- standard prosthesis, also called anatomical, in which the prosthesis accurately reproduces the anatomy of the humeral bone, with the humeral head integral with the stem which is implanted in the diaphyseal channel of the humerus; the prosthesis is completed with the glenoid component, in turn fixed to the glenoid and on which the humeral head is articulated;

- reverse prosthesis, again consisting of a humeral stem, but on whose top the concave component is fixed, which defines the articulation seat of the humeral head and which, in this configuration of the prosthesis, is fixed to the glenoid.

The shoulder prosthesis surgery described above comprises, in both cases, the resection of the humeral head of the humerus to which the prosthesis is to be applied, in order to expose the diaphyseal channel, the implant seat of the humeral stem. The plane of this resection is formed in particular with an angle, with respect to the anatomical axis of the humerus, which is different in the standard prosthesis and reverse prosthesis. In a standard implant, for example, this angle is about 135°, in a reverse implant it is about 150° .

In the known art, the choice of the angle of the resection plane immediately restricts the type of standard or reverse implant to be used. The surgeon however often finds that during surgery it is necessary to change the indication of the initial type of prosthesis (for example a standard prosthesis) , in relation to the anatomical state of the patient (which, in the example considered, may make it preferable to use the type of reverse shoulder prosthesis) .

In the present state, the change in the type of intervention from the standard shoulder prosthesis to the reverse shoulder prosthesis requires a modification of the angle of the resection plane, which leads to the necessity of a further resection intervention. This additional corrective intervention, however, has the disadvantage of reducing the length of the bone and in any case represents an invasive operation for the patient, to such an extent that it is only effected in cases of absolute necessity.

In addition to this disadvantage, there is also the fact that, as the prostheses of the known art specifically relate to the standard or reverse type, it is necessary to have both instrumentations, in addition to the relative prosthesis components, with greater risks of infection, prolonged surgery times, an increase in the costs of the equipment and the necessity of storing both types of prosthesis.

The main objective of the present invention is to provide a new shoulder prosthesis which, with respect to traditional prostheses, offers surgeons the possibility of choosing, in situ or during surgery, the type of standard or reverse prosthesis to be used, without the necessity of applying modifications to the resection plane of the shoulder prosthesis of the standard type.

A further objective of the invention is to avoid the necessity of additional surgical interventions on the humeral head, traditionally necessary for passing from the standard type of shoulder prosthesis to the reverse type of shoulder prosthesis.

Another objective of the invention is to make it no longer necessary to have distinct medicated prosthesis components between standard and reverse prosthesis applications .

These and other objectives are achieved with the shoulder prosthesis, as specified in claim 1. Preferred embodiments of the invention are indicated in the remaining claims .

With respect to the known art, the shoulder prosthesis of the invention offers the advantage of making the resection of the humeral head univocal, in order to allow surgeons to choose the type of application, standard or reverse, directly at the moment of surgery. In this way, the choice of the shoulder prosthesis to be applied can be made in relation to the anatomical state observed during surgery, without having to correct the resection plane of the humeral head with respect to that of the standard prosthesis .

The invention therefore also avoids having to resort to traditional invasive interventions, normally required when the type of intervention must be modified with respect to that initially established.

Furthermore, thanks to the possibility of converting the prosthesis of the invention from the standard type to the reverse type, there is also the important advantage that the different instruments for these different prostheses are no longer necessary, thus reducing the risk of infection. The surgery times are consequently also reduced, with lower costs for the equipment and without the necessity of storing both types of prosthesis.

These objectives, advantages and characteristics are evident from the following description of a preferred embodiment of the prosthesis of the invention, provided for illustrative and non-limiting purposes in the figures of the enclosed drawings.

In the drawings:

figure 1 illustrates the type of standard shoulder prosthesis implant;

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

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

figures 7 to 10 illustrate the shoulder prosthesis of the invention, in its reverse configuration;

- figure 11 illustrates 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 standard and reverse applications of the shoulder prosthesis, respectively. The standard application of the shoulder prosthesis illustrated in figure 1 comprises the insertion, in the diaphyseal channel of the humerus 2, of a stem 1, in turn provided with a humeral head 3 articulated on the glenoid 4.

For this standard application, a resection is effected by surgery on the anatomical humeral head according to the resection plane 5, whose axis 6 is tilted, with respect to the axis 7 of the humerus 2, by an angle a, normally equal to 135°.

In the reverse application of figure 2, the resection of the head of the humerus 2 is effected on the plane 10, defined by a reverse element 8, in turn articulated on the glenosphere 9. In this type of reverse application, the angle β which is formed between the axis 11 of the above resection plane 10 and humeral axis 7 is normally about 150°.

Traditionally, once the choice has been made, for example of the standard application of the shoulder prosthesis of figure 1, the possible passage to the reverse type of figure 2 requires surgical modification of the resection plane, from that 5 with angle a, to that 10 with angle β. This modification therefore requires additional surgery to that previously effected, of an invasive nature, and which reduces the quantity of bone available for the implant.

The correction described above also has the disadvantage of requiring specific equipment, which is distinct between the standard and reverse shoulder prosthesis, and therefore reciprocally incompatible.

In order to overcome these drawbacks, the prosthesis of the invention, as illustrated in figure 3, comprises a humeral stem 12 provided with a conical proximal female seat 13, suitable for housing a standard adaptor 14. The latter is provided in particular with a male cone 15, which is engaged inside the above seat 13. The adaptor 14 also has a cone bit 16, protruding from the side of the humeral head 17 and suitable for being engaged inside a corresponding seat 18 of the same. There is also a housing hole 19 for a fixing screw (not illustrated) of the adaptor 14 to the stem 12, by engagement of the same screw inside a corresponding threaded hole 20 situated in said seat 13 of the stem 12.

As represented in figure 4, in the humeral component of the standard prosthesis of the invention, as thus assembled, the axis 22 of the respective resection plane 21 forms, with the axis 23 of the stem 12 of the prosthesis, the angle a (for example 135°) required for standard applications. In its reverse version, the shoulder prosthesis of the invention illustrated in figure 7 maintains the structure of the stem 12, provided with a conical proximal female seat 13 and a threaded hole 20.

In this version, a reverse adaptor 25 is fixed on the above-mentioned female seat 13, composed of a discoidal body which, on the stem side 12, has a male cone bit 26 suitable for being engaged inside the same female seat 13. On the opposite side, the same adaptor 25 has a housing 27 for the reverse insert 28. A seat 19 for the fixing screw in the threaded hole 20 of the stem 12 is also envisaged on the reverse adaptor 25.

The adaptor 25 now described exerts the function of fixing the reverse insert 28 to the stem 12, in particular for engagement of the connection 29 of this insert 28 to the inside of the cited housing 27. On its proximal side, the reverse insert 28 has a seat 30 for the glenosphere 31 of figure 9.

As illustrated in figure 8, the reverse version of the shoulder prosthesis of the invention maintains the standard resection plane 21 tilted by the respective angle a (for example 135°) , but it also has the inclination β of the reverse shoulder prosthesis plane 32 (for example equal to 150°) formed between the axis 23 of the stem 12 and axis 33 of the reverse 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 glenoid by means of a plate 34 and screws 35.

As can be seen in particular in figure 8, the prosthesis of the invention is suitable for being converted from the standard application to the reverse application, thanks to the preservation of the standard resection plane 21 also in the reverse application of the shoulder prosthesis with the plane 32 tilted by the respective angle β. This result is possible due to the simple application, in the conical proximal seat 13 of the stem 12, of the reverse fixing adaptor 25 of the respective reverse insert 28 which defines the above- mentioned reverse plane 32.

The above-mentioned conical coupling between the various components of the prosthesis of the invention can obviously be substituted by equivalent means, in any case suitable for the same function.

In order to give the prosthesis of the invention primary stability, in particular for insertion of the stem into the humeral diaphyseal channel, the proximal part 36 of the stem 12 of figure 11 has a flared configuration, i.e. developing from the distal part 37 towards the proximal part 36.

The secondary stability of the prosthesis of the invention, on the other hand, is obtained thanks to the presence, on the above proximal part 36 of the stem 12, of a cage-structured portion 38, provided with apertures 39 which allow the regrowth of the bone tissue, occupying the internal space or cavity 40 of the same stem 12.

The structure of the stem 12 of the invention internally containing the above cavity 40, allows a homologous bone to be housed in the latter (for example taken from the humeral head resection) , or another material suitable for stimulating the regrowth of the bone inside the stem.

Claims

1. A shoulder prosthesis, characterized in that it is provided with means for allowing it to be converted from the standard application to a reverse application, by maintaining the (a) angle of the standard resection plane (21) also in the reverse application of the shoulder prosthesis having a tilted resection plane (32) of the respective (β) angle.

2. The prosthesis according to claim 1, characterized in that said means consists of a humeral stem (12) having a proximal female seat (13) suitable for interchangeably housing adaptors for the standard application of the shoulder prosthesis (14) and reverse application of the shoulder prosthesis (25) , respectively.

3. The prosthesis according to claim 2, characterized in that said adaptor for the reverse shoulder prosthesis (25) is oriented, on the stem side (12), according to the plane (21) with an inclination (a) of the standard shoulder prosthesis and is provided, on the opposite side, with an insert (28) oriented according to the plane (32) with an inclination (β) of the reverse shoulder prosthesis.

4. The prosthesis according to claim 3, characterized in that said adaptor (14) for the standard shoulder prosthesis has, on the stem side (12), coupling means (15) in the female seat (13) of the same stem (12) , and, on the opposite side, fixing means (16) of the humeral head (17), in turn provided with a corresponding seat (18) for said fixing means (16) .

5. The prosthesis according to claim 4, characterized in that said adaptor (25) for the 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 said insert (28) of the reverse prosthesis.

6. The prosthesis according to claim 5, characterized in that said insert (28) is provided with an engagement connection (29) in said housing (27) .

7. The prosthesis according to claim 6, characterized in that said insert (28) has, on the proximal side, a seat (30) for the glenosphere (31) of the reverse shoulder prosthesis.

8. The prosthesis according to claim 7, characterized in that, in the standard version, it has a ferrule (24) on the humeral head (17) and, in the reverse version, said glenosphere (31) is articulated on said insert (28) .

9. The prosthesis according to one or more of the previous claims, characterized in that said stem (12) has an internally hollow structure (40) .

10. The 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 itself to the form of the humeral channel.

11. The prosthesis according to claim 10, characterized in that said flared proximal part (36) of the stem (12) is composed of a cage structure (38) , provided with apertures (39) suitable for forming bone interactions between the inside and outside of the same stem (12) .