EP1294320A1

EP1294320A1 - Articulated prosthesis

Info

Publication number: EP1294320A1
Application number: EP01949596A
Authority: EP
Inventors: Henry Graf
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-06-30
Filing date: 2001-06-29
Publication date: 2003-03-26
Also published as: AU2001270721A1; FR2810878B1; FR2810878A1; WO2002000141A1

Abstract

The invention concerns an articulated prosthesis (2) comprising at least a fixed element (12) designed to be secured to an organ of the human body, in particular a bone, at least a mobile element (4) capable of moving relative to the or each fixed element (12) and at least an intermediate element (20) for articulating the or each mobile element (4) relative to the or each fixed element (12). The or each intermediate element (20) is received in an internal volume (16) of the fixed element (21), said intermediate element (20) having at least one degree of freedom in rotation relative to said fixed element (12), while the mobile element (4) is received at least partly in an internal volume (28) of the intermediate element (20), having at least one degree of freedom in rotation relative to said intermediate element (20), and means are provided to secure in translation, said other element (4) relative to said intermediate element (20).

Description

ARTICULATED PROSTHESIS

The present invention relates to an articulated prosthesis. The invention relates more particularly to such a prosthesis which, once implanted, connects two parts of the 'human body, between which mechanical stresses are exerted. It can be in particular, on the one hand the acetabulum of the hip or the shoulder and, on the other hand, the medullary canal of the femur or the humerus.

The invention proposes to produce an articulated prosthesis, the structure of which is simple, the mounting of which is easy and which is reliably implanted in the organs which it connects. To this end, it relates to an articulated prosthesis, characterized in that it comprises:

- at least one fixed element intended to be made integral with an organ of the human body, in particular with a bone,

- at least one mobile element able to move relative to or each fixed element,

- as well as at least one intermediate element allowing the articulation of the or each mobile element with respect to the or each fixed element,

- in that the or each intermediate element is received in an interior volume of the fixed element, this intermediate element having at least one degree of freedom in rotation relative to this fixed element, first means being provided, to allow the joining in translation of said intermediate element relative to said fixed element, comprising a periphery, substantially rigid, of the outlet of the interior volume of this fixed element,

- And in that the mobile element is received at least partially in an interior volume of the intermediate element, having at least one degree of freedom in rotation relative to this intermediate element, and in that there are provided second means allowing the movable element to be joined in translation relative to said intermediate element, these second means comprising a periphery substantially rigid, the outlet of the interior volume of this intermediate element.

The invention will be described below, with reference to the accompanying drawings, given only by way of nonlimiting examples, in which:

- Figure 1 is a longitudinal sectional view, illustrating the various components of an articulated prosthesis according to the invention;

- Figures 2, 2A and 2B are views similar to Figure 1, illustrating three stages of mounting of an intermediate element of the prosthesis of Figure 1, in the interior volume of a fixed element of this prosthesis; and

- Figures 3 and 3A are views similar to Figure 1, illustrating the introduction of a movable member of the prosthesis of Figure 1, in the interior volume of the intermediate element of this prosthesis.

Figure 1 illustrates an articulated prosthesis according to the invention, which is a shoulder prosthesis. As a variant, the person skilled in the art may produce a prosthesis according to the invention, the type of which is different, for example a hip prosthesis.

The prosthesis 2 illustrated in this figure 1 comprises a movable element, generally designated by the reference 4, which comprises a rod 6, of known profile, which is intended to be introduced into the medullary canal of the humerus not shown. This rod β is extended by a collar 7, as well as by a spherical head 8 of diameter d, which is provided with an equatorial flat extending in an inclined manner. This means that this flat is not perpendicular to the main axis A of the flange 7. The transverse dimension of this flat 10, which is denoted by, is less than the aforementioned diameter d.

The prosthesis illustrated in Figure 1 also includes a fixed element 12, intended to be secured to the acetabulum not shown of the shoulder. This fixed element 12 has a spherical outer surface, as well as a spherical inner surface, of diameter D. This inner surface extends over an angular sector greater than 180 °, so that the transverse dimension L, corresponding to the outlet 14 of the internal volume 16 of the element 12, is less than the aforementioned diameter D.

The inner wall of the fixed element 12 can also be hollowed out with a not shown notch, making it possible to locally widen the cross section of the housing 16. This guarantees an easier introduction of an intermediate element into this housing, like this is described in the following. The prosthesis finally comprises an intermediate element 20, the external surface 22 of which defines a portion of truncated sphere, of diameter identical to that D of the housing 16. This intermediate element has an internal surface 24 also spherical, the diameter of which is equal to that of of the head 8.

The inner surface 24 of the intermediate element 20 extends along an angular sector greater than 180 °. In this way, the transverse dimension of the outlet 26 of the housing

28 of this element 20 is substantially equal to the transverse dimension of the flat 10.

The mounting of the prosthesis illustrated in FIG. 1 will now be described with reference to FIGS. 2 and 3.

The first step is to introduce the intermediate element 20 into the interior volume 16 of the fixed element 12.

For this purpose, this intermediate element is arranged, so that its spherical outer surface 22 is in the vicinity of the outlet 14 of the housing 16. Then, this intermediate element is brought axially closer to the fixed element, so as to make it penetrate into the housing 16, as shown in Figure 2A. The intermediate element 20 and the fixed element 12 are not linked in rotation or in translation, in this position of free introduction.

The intermediate element 20 is then made to pivot, so that its external surface 22 extends in the vicinity of the internal walls of the fixed element, as shown in FIG. 2B. Once these operations have been carried out, the intermediate element 20 has no degree of freedom in translation relative to the fixed element 12, in this position of use illustrated in FIG. 2B.

In fact, the transverse dimension L of the outlet 14 is less than the external diameter D of this intermediate element 20. On the other hand, there are three degrees of freedom in rotation between the intermediate element and the fixed element.

As shown in FIG. 3, it is then a question of introducing the spherical head 8 of the movable element 4 into the interior volume 28 of the intermediate element 20. To this end, the head 8 is first tilted , so that the flat 10 extends perpendicularly to a diameter of the element 20, passing through the center of its outlet. The moving element is then brought axially closer to the intermediate element. Since the transverse dimension of the flat 10 is substantially identical to that of the outlet 26, this allows free introduction of the head 8 into the housing 28, as illustrated in FIG. 3.

Then, once the head 8 abuts against the inner surface 24 of the intermediate element, the movable element 4 is pivoted, so as to give it the arrangement illustrated in FIG. 3A. Given that the transverse dimension of the outlet 26 is less than the diameter d of the head 8 of the movable element 4, the latter cannot emerge from the interior volume 28, in the arrangement of FIG. 3A.

In the case where the movable element 4 is not free to pivot about the axis A, it is possible to tilt the intermediate element 20 within the housing 16 of the fixed element 12. Then, we move axially the movable element 4 of the intermediate element thus tilted, so that the flat 10 cooperates with the periphery of the outlet 26, in a manner similar to that which is illustrated in FIGS. 3 and 3A.

The periphery of the outlet 26 is substantially rigid. To this end, the intermediate element can be made entirely of a rigid material, in particular metallic. As a variant, this intermediate element can be made of a deformable material, such as polyethylene, a rigid ring then being attached in the vicinity of the abovementioned outlet. Once the arrangement of FIG. 3A has been completed, it is possible to attach to the flat part 10 an advantageously removable stop means, such as a screw 30. The latter, by limiting the pivoting of the head 8 relative to the intermediate element 20, prevents the head from recovering its position of FIG. 3, which avoids any untimely separation between this intermediate element 20 and this mobile element 4.

The invention makes it possible to achieve the objectives mentioned above. Indeed, the various constituent elements of the articulated prosthesis of the invention have a relatively simple structure.

The assembly of these various elements is particularly easy, since the mobile element has a position of free introduction into the interior volume of the intermediate element, while the latter also has a position of free introduction into the interior volume of the fixed element. Thus, a user does not have to use significant physical force, so that these different introductions can be carried out without compromising the integrity of the other organs of the patient.

Furthermore, in their position of use, the various constituent elements of the prosthesis are linked in translation, two by two. In this way, this prosthesis is very satisfactory.

In addition, it should be noted that the mounting of these different elements is carried out by performing only a pivoting, an axial introduction, then another pivoting. Thus, this assembly does not induce any mechanical deformation of these different elements, which is particularly advantageous in terms of reliability and longevity of the prosthesis.

It should be noted that the presence of the intermediate element allows the mutual mounting of the fixed and mobile elements, even though there is practically no rotational movement between these two elements.

Finally, once the articulated prosthesis of the invention is put in place, it has a high resistance with respect to mechanical stresses, exerted in particular in traction. In Indeed, the presence of the intermediate element makes it possible to transmit only to a very small extent the possible forces to which the articulated prosthesis of the invention is subjected.

Claims

1. Articulated prosthesis, characterized in that it comprises:

- at least one fixed element (12) intended to be made integral with an organ of the human body, in particular of a bone,

- at least one mobile element (4) able to move relative to the or each fixed element, - as well as at least one intermediate element (20) allowing the articulation of or each mobile element relative to the or each fixed element,

- in that the or each intermediate element is received in an internal volume (16) of the fixed element, this intermediate element (20) having at least one degree of freedom in rotation relative to this fixed element, first means being provided, to allow the securing in translation of said intermediate element (20) relative to said fixed element (12), these first means comprising a periphery, substantially rigid, of the outlet (14) of the interior volume (16) of this fixed element,

- And in that the mobile element is received at least partially in an internal volume (28) of the intermediate element (20), having at least one degree of freedom in rotation relative to this intermediate element, and in this that second means are provided for the securing in translation of said movable element (4) relative to said intermediate element (20), these second means comprising a periphery, substantially rigid, of the outlet (26) of the interior volume (28) of this intermediate element.

2. Articulated prosthesis according to claim 1, characterized in that said intermediate element (20) has a truncated spherical outer surface (22), and cooperates with a corresponding spherical inner surface, which is provided with said fixed element (12).

3. Articulated prosthesis according to claim 2, characterized in that said fixed element has a notch for introducing the intermediate element into the volume inside of this fixed element.

4. Articulated prosthesis according to one of the preceding claims, characterized in that said movable element (4) has a spherical head (8), able to cooperate with a corresponding spherical inner surface (24) of the intermediate element (20) .

5. Articulated prosthesis according to claim 4, characterized in that the spherical head (8) of said movable element (4) is provided with an equatorial flat (10) for introducing this head (8) into the interior volume of the 'intermediate element (20).

6. Articulated prosthesis according to one of the preceding claims, characterized in that the intermediate element (20) is provided with a stop member (30), in particular removable, making it possible to limit the pivoting of the mobile element (4 ) with respect to this intermediate element.

7. Articulated prosthesis according to any one of the preceding claims, characterized in that it forms a shoulder or hip prosthesis, the fixed element (12) being intended to be made integral with the acetabulum of the shoulder or the hip, while the movable element (4) comprises a rod (6) capable of being introduced into the medullary canal of the humerus or femur, as well as a head (8) extending this rod and capable of being introduced in said interior volume (28) of the intermediate element (20).