WO1994010942A1

WO1994010942A1 - Foot prosthesis

Info

Publication number: WO1994010942A1
Application number: PCT/CH1993/000254
Authority: WO
Inventors: Alain Lallemand
Original assignee: Composites-Busch & Cie
Priority date: 1992-10-11
Filing date: 1993-11-05
Publication date: 1994-05-26
Also published as: EP0625033A1; CA2127691A1

Abstract

A foot prosthesis comprising a front plate (1) and a heel (2). The heel (2) is C-shaped with the opening (5) of the C facing the back of the prosthesis. The front plate has a stretched S shape and comprises a forward portion (10), a rear portion (11) and a middle portion (13) where the curvature changes direction. The front plate and the heel each comprise a plurality of layers of carbon, glass or aramide fibres. The fibre layers of the front plate and those of the heel are respectively coated with one or more layers of woven material then impregnated and shaped.

Description

Foot prosthesis

Technical area

The present invention relates to a foot prosthesis made of composite material.

Prior art

10 Various prostheses have already been proposed including a framework made of composite material based on carbon or glass fibers, for example Kevlar, impregnated with resin.

15 Prostheses made of composite material make it possible to obtain flexibility without appreciable dissipation of energy, so that the prosthesis restores the energy which led to its bending when the stress ceases.

2O In fact, unlike prostheses made of thermo-plastic material, the flexibility of prostheses made of composite material decreases as the force is applied, which is important in particular when climbing a staircase. While a thermoplastic prosthesis would continue to

25 bend, the composite prosthesis tightens and locks, then the load is reduced and, when the foot leaves the step, the prosthesis restores the energy which was supplied to it, thus facilitating the recovery of the body for the next step.

30 Prostheses of this type are for example described in American patents Nos. 4,645,509 and 4,959,073, in French patent applications published under Nos 2,612,768 and 2,626,463 and in European patent applications published under Nos 0401864 and 0487852.

35

However, none of the foot prostheses mentioned above constitute a truly versatile prosthesis, being suitable for both normal walking and climbing stairs. The difficulty of making a polyva¬ slow prosthesis is due to the different reactions it must provoke depending on the type of stress to which it is subjected. It must react in some cases as a more or less flexible shock absorber and in others as a kind of springboard. In particular, the heels of the prostheses proposed so far, when they are of simple design, are either too flexible or too hard. High-performance heels, on the other hand, have a relatively complex design. None of the foot prostheses which have been proposed so far make it possible to take full advantage of the advantageous properties described above with regard to modern composite materials.

Statement of the invention

The object of the present invention is to propose a prosthesis of a composite material which overcomes the drawbacks of the prostheses set out above.

To this end, the invention relates to a prosthetic foot made of composite material, comprising on the one hand a "C" shaped heel, intended to serve as a rear support for the prosthesis on the ground, the opening of the "C "being directed towards the rear of the prosthesis, and on the other hand a spatula comprising a front part and a rear part, the front part of the spatula being intended to serve as a front support of the prosthesis against the ground, the heel being arranged below the rear part of the spatula.

According to one embodiment, the heel may include an upper arm and a lower arm, both of substantially planar and parallel shapes. The lower arm of the heel may be longer than the upper arm.

The spatula may have the shape of a stretched "S", comprising a front part, a rear part and an intermediate part having a zone of inflection of the curvature, the front part of the spatula being able to comprise a surface substantially flat lower.

The tip and / or the heel may include a plurality of layers of carbon fibers, glass or aramid.

At least part of the layers of fibers of the spatula can be truncated at the front, so as to constitute a gradation of the thickness of the spatula.

All of the fiber layers of the tip and / or all of the fiber layers of the heel can be respectively covered with at least one layer of woven material and then be impregnated and shaped.

The prosthesis can be arranged so that its attachment to the tibia is effected by means of a fastening element passing through the upper arm of the heel and the rear part of the spatula and fixed in a connection device mounted on a tibia. .

The prosthesis may include an element placed on the upper surface of the rear part of the spatula and intended to serve as a base for fixing the prosthesis on the connecting element mounted on the tibia.

Brief description of the drawings

The description which follows, given by way of example, refers to the drawing in which:

- Figure 1 is a perspective view of three quarters before a schematic example of a prosthetic foot according to the invention;

- Figure 2 is a side view of the prosthesis of Figure 1 covered with a cosmetic coating;

- Figure 3 is a perspective view illustrating the design of the spatula of the prosthesis of Figure 1 in progress;

- Figure 4 is a side view of a schematic example of prosthesis according to the invention comprising a shock absorber device of a first type;

- Figure 5 is a side view of a schematic example of prosthesis according to the invention comprising a cushioning device of a second type; and

- Figure 6 is a side view of a schematic example of prosthesis according to the invention comprising a shock absorber device of a third type.

Ways to realize the invention

The frame shown in Figure 1 includes a spatu¬ 1, a heel 2 and a plate 3 serving as a base for fixing the prosthesis to an artificial tibia. The spatula 1 and the heel 2 are made separately from composite material, then are assembled using a screw 4 when the prosthesis is fixed to the artificial tibia, the screw 4 passing through the upper arm 7 of the heel, the part rear 11 of the spatula, then the base plate 3 and being screwed into a connecting device, known per se, fixed on the tibia.

As can be seen in FIGS. 1 and 2, the profile of the spatula recalls the shape of a stretched "S", comprising a front support part 10, constituting the spatula proper, and a rear part 11 , substantially planar, of smaller dimensions than those of the front part, the intermediate part 13 connecting the front and rear parts having a zone of inflection of the curvature of the spatula. The front support part 10 of the spatula has a substantially planar lower surface 12.

Spatula 1 has a plurality of layers of fibers carbon, glass fibers or aramid fibers arranged lengthwise and / or widthwise depending on the degree of flexibility desired. Each layer, with a thickness of about 0.5 millimeters, is cut to the shape of the foot. The front part of the upper layers is truncated in an upward gradient, so as to gradually decrease the thickness of the spatula between its front end and its rear end, as shown in Figure 3. The assembly is then covered with a or several layers of woven materials, for example tres¬ its carbon fibers or any other suitable fiber, such as glass or aramid fibers. The percentage of each kind of fibers and the direction of these fibers determine the different models of prostheses according to the weight and the level of activity of the patient. Thus, for example, the percentage of glass fibers will be increased to increase the flexibility of the prosthesis or, on the contrary, the percentage of carbon fibers will be increased to reduce said flexibility. The assembly obtained is then treated by the RTM (Resin Transfer Molding) molding process, a process known per se, so as to impregnate the assembly with epoxy resin by injection into a closed mold, while giving it the desired shape. . The assembly is then cut at its ends according to the desired size and shape.

The heel 2 has the shape of a "C" whose opening 5 is directed towards the rear of the prosthesis. It is arranged below the rear part 11 of the spatula. According to a preferred embodiment, the two arms of the C are of planar and parallel shape, the lower arm 6 being substantially longer than the upper arm 7. The heel can be produced according to the same process as the spatula, the only difference is that the fiber layers all have the same surface, that is to say that a thickness gradient is not necessarily provided. A circular hole 8 for handling the screw 4 is provided in the lower arm 6 of the heel. This hole is arranged so that its center coincides with the axis 9 of the screw 4. The fixing base 3 can for example be machined in a glass fiber / epoxy plate with a thickness of the order of four millimeters or molded in glass-carbon / epoxy. It can be attached to the upper rear end of the spatula by gluing, for example using an epoxy resin.

The combination of the "C" shape of the heel and the "S" shape of the tip really allow versatile performance of the prosthetic foot according to the invention. It should be emphasized here that the versatile properties derive from the structural characteristics of the prosthesis, while using only simple elements, that is to say without resorting to complex devices. Indeed, the heel in the shape of "C", with its opening directed towards the back, allows an adequate cushioning during normal walking. This amortization fully and directly benefits from the nature and properties of the materials used, so that the response to the stress is directly a function of the stress itself and is therefore fully adapted to it, without sudden blockage or fixed stop. On the other hand, the "S" shape of the spatula, with a front part having a flat bottom surface, is particularly well suited for placing the foot on a stair step. The "S" shape presents a curve and a counter-curve allowing an optimal restitution of the energy supplied to the prosthesis when the foot is pressed on the step. This restitution is done in a way in two places thanks to the double curve. On the other hand, the reduction in the thickness of the spatula towards the front of the latter allows good flexibility of the forefoot when the foot is flexed. The implementation of several preformed curves has the advantage of printing both a bending in accentuation of the curve and a bending fighting against the curve. Depending on the nature of the stress, the distribution between the two types of flexion will be different, but in all cases this will result in a harmonious reaction offering the user new comfort. Moreover, given its design, the connection zone between the heel 1 and the tip 2 does not deform and there is consequently no relative movement between the heel and the tip in this area, therefore no friction, which prevents squeaking while walking.

We must also emphasize the gradation of thickness which marks the front of the spatula. Indeed, this gradient makes it possible to trigger a stimulus effect having a large horizontal component. In fact, this part recreates the little impulse normally given by the toes when walking. This impulse allows a revival of the limb, as opposed to the revival of the whole body which results from the middle part of the spatula.

The very limited number of elements making up the prosthesis has two immediately perceptible advantages. Firstly, there is a simplicity of manufacture, assembly and maintenance, and secondly, the extreme reliability of the assembly. The manufacturing technique used, as well as the simplicity of the shapes of the elements, allow industrial production and consequently a substantial reduction in manufacturing costs. Finally, and this is undoubtedly the most important, by using only a limited number of parts of simple shapes and by using only a relatively simple manufacturing technology, the prosthesis according to the invention offers truly versatile characteristics of use, expressed in perfect harmony with each other, thanks precisely to the combination of simple and intimately complementary lines that fully enhance the inherent performance of the materials used.

The prosthesis which has been described above can be used as it is, without coating, as shown in Figure 1, or provided with a cosmetic coating 15, as shown in Figure 2. Thanks to the simplicity of the shapes of its elements , the prosthesis of the invention can be very easily dressed and allows an almost perfect reconstruction of a foot, in particular thanks to the narrowness of the prosthesis at the ankle. A filling foam 16 can be arranged in the volume limited on the one hand by the intermediate part 13 of the spatula and on the other hand by the bent part of the heel 2. A filling foam can also be provided in the interior volume of the heel defined by its two arms 6 and 7.

In order to further improve comfort when attacking the ground with the heel, a shock absorbing device, adjustable or not, can be inserted into the heel of the prosthesis so as to allow progressive attack on the heel. This shock absorbing device can for example comprise an independent base support plate connected to the heel by a shock absorbing element.

According to a first embodiment, represented in FIG. 4, the shock absorbing device comprises a base support plate 41 disposed below the lower arm 6 of the heel and integral with a shock absorbing cylinder 42, for example made of polyurethane, mounted under the upper arm 7 of the heel.

According to a second embodiment, shown in Figure 5, the damping device comprises a base support plate 51 similar to the plate 41 and arranged in a similar manner. The plate 51 is connected to a damping element 52 secured to the upper arm 7 of the heel and comprising a spring 53.

According to a third embodiment, represented in FIG. 6, the damping device comprises a base support plate 61 disposed below the lower arm 6 of the heel and mounted in articulation 62 at the front part of said lower arm 6. The plate 61 acts against a hydraulic shock absorber 64 secured to the lower arm 6 of the heel. This damper can be adjustable via an adjustment device 65.

In the three cases which have just been described, a compensation foam can be placed under the base support plate 41, 51, 61 to compensate for the irregularities of the cosmetic coating.

Claims

1. Foot prosthesis made of composite material, characterized in that it comprises on the one hand a heel (2) in the shape of a "C", intended to serve as a back support for the prosthesis on the ground, the opening ( 5) "C" being directed towards the rear of the prosthesis, and on the other hand a spatula comprising a front part (10) and a rear part (11), the front part (10) of the spatula being intended to serve as the front support of the prosthesis against the ground, the heel (2) being arranged below the rear part (11) of the spatula.

2. Prosthetic foot according to claim 1, characterized in that the heel (2) comprises an upper arm (7) and a lower arm (6), both of substantially planar and parallel shapes.

3. Prosthesis according to claim 2, characterized in that the lower arm (6) of the heel is longer than its upper arm (7).

4. Foot prosthesis according to one of the preceding claims, characterized in that the spatula is in the form of an "S" drawn, comprising a front part (10), a rear part (11) and an intermediate part (13) having an area of inflection of the curvature.

5. Foot prosthesis according to claim 4, characterized in that the front part (10) of the spatula has a lower surface (12) substantially planar.

6. Foot prosthesis according to one of the preceding claims, characterized in that the tip and / or the heel comprises (s) a plurality of layers of carbon fibers, glass or aramid.

7. Foot prosthesis according to claim 6, characterized in that at least part of the layers of fibers of the spatula are truncated at the front, so as to constitute a gradient in the thickness of the spatula.

8. Foot prosthesis according to one of claims 6 or 7, characterized in that all of the fiber layers of the tip and / or all of the fiber layers of the heel are (are) respectively covered (s) at least one layer of woven material then is (are) impregnated (s) and shaped.

9. Foot prosthesis according to one of the preceding claims, characterized in that it is arranged so that the fixing of the prosthesis on the tibia is carried out using a fixing element (4) passing through the upper arm (7) of the heel and the rear part (11) of the spatula and fixed in a connecting device mounted on a tibia.

10. Foot prosthesis according to claim 9, characterized in that it comprises an element (3) disposed on the upper surface of the rear part (11) of the spatula and intended to serve as a base for fixing the prosthesis on the connecting element mounted on the tibia.

11. Foot prosthesis according to one of the preceding claims, characterized in that a damping device, adjustable or not, is inserted in the heel of the prosthesis so as to allow a progressive attack of the heel.

12. Foot prosthesis according to claim 11, characterized in that the shock absorbing device comprises an independent base support plate connected to the heel by a shock absorbing element.