WO1998018414A1

WO1998018414A1 - Prosthesis device comprising a lower leg part, a galosh part and a foot part

Info

Publication number: WO1998018414A1
Application number: PCT/NO1997/000283
Authority: WO
Inventors: Dag JØRSTAD; Jon Andersen; Egil Jensen
Original assignee: Joerstad Dag; Jon Andersen; Egil Jensen
Priority date: 1996-10-25
Filing date: 1997-10-27
Publication date: 1998-05-07
Also published as: AU4887397A; NO302214B1; NO964545D0; NO964545A

Abstract

An artificial lower leg which comprises a lower leg part, a gaiter part and a foot part, wherein the gaiter part is attached to the lower leg part by a tongue and groove system and the foot is glued to the gaiter part, where opposite surfaces in the gaiter and foot parts are of such a nature that a movement of the foot in relation to the gaiter part will give an angular change in the foot's position in relation to the lower leg, as described herein. A set for adaptation and adjustment of the artificial limb is also described.

Description

PROSTHESIS DEVICE COMPRISING A LOWER LEG PART, A GALOSH PART AND A FOOT PART

The present invention concerns an artificial limb consisting of a lower leg part, a gaiter part and a foot part.

There is a wide selection of artificial feet and foot systems on the market to- day, but they are all essentially based on the following fundamental principle:

1. Feet used in laminated/moulded systems.

2. Feet used in modular systems.

3. Feet in energy recovery /carbon fibre systems. Re 1 - Laminated/moulded systems.

In this case the feet consist of two parts - an ankle part and a foot part. As a rule the ankle part is made of wood or plastic and has a core consisting of a threaded piece in which a bolt through the lower part of the ankle part can be secured. This ankle part is mounted on the artificial lower leg by means of lamination, moulding, gluing or screwing.

The foot part consists of a fixed core which may, e.g., be made of wood, with a through-going hole which, e.g., is adapted to the bolt in the ankle part. Attaching the foot is often a combination of screwing the foot and ankle joints together, and gluing. The foot is covered with a soft, flexible outer part which facilitates the use of the foot.

In all such prosthetic systems it is necessary to accurately adjust the position between foot and lower leg in order to give the user an optimal gait. In this group this is done by replacing the ankle part with an adjustment device which permits an accurate determination of the foot's position. This so-called jig is removed and the foot is screwed on to the ankle part in the correct position. This makes the fitting of an artificial limb complicated and expensive.

Re 2 - Modular systems.

The foot can be constructed as above, but the bolt is not attached to an ankle part, but to a connector which permits adjustment of the foot's angles in relation to the lower leg part, which in turn has a connector corresponding to that of the foot. There are many different types of feet for the modular systems. All of them consist of a hard inner part and a soft outer part and they all have the possibility of connection between the foot's inner part and a suitable modular connector by means of screws or bolts.

The possibilities of adjustment are good in this system, but require relatively complicated mechanical components which increase the weight of the artificial limb and are expensive to purchase.

Re 3 - Energy recovery systems.

In this system the core of the foot part and the lower leg part is constructed of a part which is elastic or flexible. In this system a part of the kinetic energy in the foot is transferred to the pliable lower leg core when the heel is placed on the ground, and returned when the foot is rotated (the foot is rotated around the ball of the toe).

These cores which normally consist of carbon fibre or epoxy composite are coated by an external soft cosmetic covering when the artificial limb is completed.

Energy recovery systems of this kind have good possibilities of adjustment and are light, but extremely expensive, requiring special tools for adjustment.

A combination of the two above-mentioned systems 2 and 3 is now being used to an increasing extent. This provides advanced systems with many possibilities of adjustment. They are therefore user- friendly, but are expensive and a special requirement is a fully established prosthesis workshop to enable them to be adjusted.

Thus there are many types of artificial legs consisting of several parts which are connected by means of the prior art. Norwegian patent no. 46930 concerns an artificial leg composed of a thigh part, a lower leg part and a foot part which are attached to one another by bolt devices, where the artificial limb is provided with straps to facilitate use. SE-B2-451 177 constitutes an artificial foot with an ankle part where the heel can be adjusted in height by a bolt device. SE-B2-466380 concerns an insertion for an artificial foot with adjustable heel height and angle in relation to any lower leg part with screw and bolt devices. US-Al-5 108 454 and US-Al-5 219 364 concern simple artificial lower legs where a shoe part can be affixed, but without any simple adjustment devices on these protheses. In DE-C 1-89427 the ankle part is situated down in the foot part and a spring device provides considerable elasticity in all directions during use.

The common factor for all these artificial limbs and limb parts is that the adjustment possibilities are either absent or are performed by means of complicated screw arrangements. Adapting the limb to the patient requires a great deal of equipment and special tools and normally each artificial limb is moulded from first principles for each person since it has to be adjusted both for the person's height, gait and leg position. Thus it is an object of the present invention to provide a prefabricated artificial limb with simple adjustment possibilities which do not require special tools, where assembly of the artificial limb also requires no special tools, and where the artificial limb should require as little expenditure as possible, and a set for fitting the artificial limb. These objects are achieved by the present invention characterized by the features indicated in the claims.

The present invention concerns an artificial leg which consists of a lower leg shell which may be equipped with a core which may or may not be removable, a gaiter part between the lower leg part and the foot, and a foot part, of which the gaiter part and the foot part are solid. The gaiter part is connected to the lower leg part by means of a cut-out which in cross section is in the form of a "dovetail", in the surface which has to be connected to the lower leg part, and the lower leg part has a similar flange with the same cross section. The foot in turn is glued on to the gaiter part. The foot's contact surface with the gaiter part is larger than the gaiter part's corresponding surface with the lower leg in addition to which the contact surfaces between foot and gaiter are curved in different directions, thus enabling the adaptation of the foot to the user to be performed by moving the foot in all the required directions in relation to the gaiter part.

The invention will now be explained in greater detail with reference to the figures, in which fig. 1 illustrates the lower leg shell, gaiter part and foot joined in perspective, fig. 2 illustrates the lower leg shell, gaiter part and foot joined in the sagittal plane (lateral plane), fig. 3 illustrates the three parts separated in the sagittal plane,

fig. 4 illustrates the parts joined in frontal section in line II-II in fig. 2,

fig. 5 illustrates the parts of the artificial limb joined in transversal section in line III-III in fig. 2, and

fig. 6 illustrates the artificial lower leg with the gaiter part and foot mounted as a lower leg part on, e.g., an artificial thigh.

The rationale for the invention is a need to be able to produce an artificial lower leg from the knee to the ground which is prefabricated and which has the following characteristics: few components, low weight, satisfactory adjustment possibilities, simple assembly, low manufacturing and adaptation costs and satisfactory functioning. These qualities combined in one artificial limb do not exist in the prior art. The object is to be able to offer an artificial lower leg with foot which is suitable for use, e.g., in developing countries and war-stricken countries, but which should also be capable of being employed everywhere where there is a need for inexpensive artificial limbs with satisfactory adjustment possibilities.

At present the production and adaptation of artificial limbs in/to developing countries and war-stricken countries are based on two general trends:

1. High-technology products produced for developed countries, but used in developing countries. These products are often expensive, make great demands on technology and tools and are not adapted to the special needs which may exist in developing countries and war-stricken countries, while at the same time optimal utilisation of the products is limited due to the lack of established workshops and expertise in these countries.

2. Artificial limbs produced on the basis of local materials and existing production capabilities. This solution provides cheap artificial limbs, but they are usually heavy and with limited durability while at the same time the production capacity is very low. There is currently an enormous need for artificial limbs in a number of war- stricken countries. The object of the invention is therefore to develop an artificial limb/limb part which should permit a substantial increase in artificial limb production and the adaptation of the limb to the individual without having to make excessive demands on tools, special equipment and other expensive and/or complicating aids.

According to the present invention this problem is solved in the following manner:

1. By constructing the artificial lower leg of few parts, the costs are kept at a low level.

2. By using prefabricated parts and a separate patent concerning a direct moulding method, NO-B 180 103, for adapting the artificial limb, the production capacity is increased and the costs reduced.

3. Reasonably priced materials are employed.

4. The production technology should to some extent be simple with the possibility of direct transfer to developing countries.

5. The parts which constitute the artificial lower leg are designed in a manner which provides satisfactory adjustment possibilities in the adaptation phase.

6. The parts of the artificial lower leg can be mounted and the artificial limb can be completed without the use of special tools.

The artificial limb according to the invention is composed of the following parts:

The lower leg shell 1 (figs. 1-6) is made of a rigid plastic material, preferably thermoplastic and is characterized by being in the shape of a lower leg from the knee down to an area from the top of the heel at the back edge, to the middle of the instep in the front edge of the foot. Moreover, the lower leg shell is hollow with an open upper end (proximal end), and closed at the lower end (distal end). The distal surface is formed with a flange in the heel- toe direction, extending over most of the length and most of the width of the distal end surface, and in both the sagittal plane and the frontal plane is in the form of a "dovetail", with the outer edges sloping inwards towards the lower leg part's centre line. This flange is formed as a part of a tongue and groove system and when connection is made to the gaiter part it should provide a rigid connection as it engages with a correspondingly shaped groove in the gaiter part's opposite end surface. In the cavity which is described in the lower leg shell a solid but light core material may be filled, preferably consisting of an expandable polystyrol (EPS) or polyurethane and which during adaptation can be partly removed in order to provide sufficient space for the amputation stump (see Norwegian patent NO-B 180 103).

The gaiter 2 (figs. 1-6) is made of a flexible and easily adhesive rubber or artificial rubber material, with an upper surface which is formed in order to exactly fit the outer shape of the distal part of the lower leg shell and consequently through its shape provide a secure attachment thereto. The gaiter is further characterized in that the distal end surface in the sagittal plane is in the form of a convex arc with a suitable radius and in the frontal plane in the form of a concave arc with a suitable radius.

The foot part 3 (figs. 1-6) is produced in a flexible and easily adhesive rubber or artificial rubber material and is characterized in that like the gaiter it is solid and its upper (proximal) surface is curved in a manner which causes it to exactly fit the gaiter's distal outer part, but where the surface of the foot is somewhat larger than the surface of the gaiter, thus enabling the foot to be pushed in all directions in order to be able to adjust the foot's angle to the leg's line of gravity. This is possible due to the curved surfaces since the specified angles can be changed on several planes merely by placing the foot in a suitable position in relation to the gaiter. The foot part's proximal surface has the same shape on the right and left sides, while the sole of the foot is formed in the right and left feet respectively.

The object of being able to fill the core material in the lower leg shell's cavity is that when the lower leg shell of the artificial lower leg has to be used in direct moulding (see NO-B 180 103), sufficient core material can be removed to create a cavity for the amputation stump, in which case the rest of the core material will act as a foundation for the moulding mass in the direct moulding. When the lower leg shell is used as a lower leg part in other types of described artificial limbs, the core material is not used. The object of the design of the lower leg shell's distal and the gaiter's proximal parts is to provide the possibility of attachment of the two parts without the need for additional fastening means or tools. Furthermore, it will also make it easy to replace the foot when it is worn out.

The object of the present design of the gaiter's distal part and the foot's proximal part is as follows:

- There will always be a need to be able to adjust the position and angle of the foot in relation to the lower leg. This can be done before the two parts are finally joined. - Because the foot's surface against the gaiter is slightly larger than the gaiter's corresponding surface, it will be possible to move the foot in all directions without reducing the contact surface between the parts. When the correct position has been obtained, the foot part and the gaiter can be joined and the excess material on the foot part can be ground or cut away. - The curve formed by the foot's proximal surface, convex in the sagittal plane and concave in the frontal plane, which curve matches the gaiter's distal surface's curves in the two planes, causes a movement of the foot in relation to the gaiter in all directions to result in an angular displacement of the foot in relation to the lower leg. The movement of the foot in the frontal direction will also be able to provide a dorsal flexion (upward turning of the foot sole) while a movement of the foot in the dorsal direction (backwards) will provide a plantar flexion of the foot (a downward turning of the foot sole). Furthermore, a movement in the lateral direction (outwards) will provide a supination of the foot (a torsion about the foot's longitudinal axis which brings the big toe higher and the little toe lower), while a movement in the medial direction (inwards) has the opposite effect.

- The relatively large surface between gaiter and foot, which has been made possible by pulling the gaiter far down on the foot, enables glue to be employed as the only binding means in attaching the two parts, which again makes very modest demands on tools in the mounting process. The large surfaces also give less torque during rotation of the foot. Comparison of the device according to the present invention with known devices which are in use

In comparison with known artificial limbs the artificial lower leg according to the present invention has three main elements, the artificial lower leg being prefabricated in one piece, and a completely new principle being employed for adjusting the artificial foot's arrangement in relation to the artificial lower leg in all planes, in addition to which the method of attaching the foot to the lower leg is performed in a new way.

The production of artificial lower legs according to the prior art is always based on an individual moulding of the amputation stump. This moulding is used as the basis for individual construction of each individual artificial lower leg. This production method has been necessary in order to ensure a satisfactory fit for the artificial limb against the amputation stump. However, the method is long-winded and has made it impossible to implement serial production and prefabrication of the part of the artificial limb which is in contact with the patient's extremity.

Due to a newly developed direct moulding technique (Norwegian patent NO- B 180 103) it has become possible to prefabricate the entire artificial lower leg. Thus when adapting the limb, a size and shape can be chosen which most closely approximate the patient's healthy leg. The upper part of the artificial lower leg is cut off to a suitable height and the artificial limb is fitted directly on the patient with the moulding technique for which a patent has been applied (patent NO-B 180 103). This technique has considerable advantages with regard to saving of both time and costs, since prefabricated prosthesis parts and simplified adaptation routines are employed, in addition to which the prefabricated artificial lower leg can also be used as the lower leg part on artificial thighs (fig. 6).

In the production and adaptation of a new artificial limb there will always be a need to be able to adjust the artificial limb during the adaptation process. The reason is that, besides having legs of different shapes and angles, the patients also have different ways of walking. This does not become evident until the patient begins to use the artificial limb, which therefore has to be capable of adjustment while the artificial limb is in use, but before it is completed. In the prior art one of two alternative methods is employed.

1. After the upper part of the leg, the prosthetic sleeve, has been made, the rest of the artificial limb is constructed from suitable materials, such as wood, and mounted on an adjustment apparatus before fitting on the foot. When the patient has tried walking and all adjustments have been made, the artificial lower leg is anchored in a jig. The adjustment apparatus is removed and the remaining cavity is filled with a suitable material. The final outer shape of the artificial limb is then prepared with reinforcement by means of lamination in glass fibre or the like. The advantages of this method are that the possibilities for adjustment are good, but the disadvantage is that it is very long-winded and time-consuming.

2. After the prosthetic sleeve has been made, the artificial limb can be constructed from modular systems with connecting adapters to the sleeve and the foot. Each connecting adapter is built as a small adjustment apparatus which is permanently situated in the artificial limb, even after the limb is completed. The advantages of this system are that it provides good possibilities for adjustment (also after the prosthesis is completed), a wide variety of choice of components and short production times. The drawback, however, is that these systems are very expensive and require a great deal of maintenance.

In the new artificial limb according to the invention, the sleeve part forms the artificial limb right down to the foot. Connecting adapters between lower leg and foot which consists of a gaiter, help to secure the foot to the artificial lower leg. The adjustment function originates from the design of the connecting surfaces between gaiter and foot, together with the fact that the foot's surface against the gaiter is larger than the gaiter's surface against the foot. Through movement of the foot in relation to the gaiter, changes of position and angle are achieved, thereby enabling the foot to be correctly adjusted in relation to the patient's angles and walking pattern. Thus the starting point will be the choice of correct sizes for the prefabricated lower leg shell, gaiter and foot. When the testing and mounting of the artificial limb are completed, excess material is ground off the foot, which can be used. The advantages of this system are good adjustment possibilities. Adjustment can be performed quickly and the total time for production of a finished artificial limb is low, in addition to which the costs are extremely low. Regardless of which type of system is chosen, at present according to the prior art the artificial foot is attached to the rest of the artificial limb by screws and bolts. The attachment area may vary somewhat, by far the majority being secured in the ankle region, but some being attached slightly higher up on the lower leg against the prosthetic sleeve. The reason for the need for screws or bolts is that the cross section of the artificial limb in the attachment area is so small that gluing alone is not sufficient. Bolts or screws are also a necessary part of the adjustment apparatus on the modular systems. This provides the advantage of rapid mounting and a replaceable foot, but the disadvantages are considerable, with increased weight, risk of bolt breakage, the possibility of the system becoming disconnected and it is very expensive. In the artificial lower leg according to the present invention the attachment point is pushed down to the instep area on the foot, thus obtaining a large attachment surface between the artificial lower leg and foot and the moment of force between lower leg and foot when the foot is rotated during walking is reduced, with the result that the foot can be secured to the gaiter with glue alone, without the need for screws or bolts, and that the gaiter can be attached to the artificial lower leg by means of a tongue and groove system without the use of either glue or screws. The advantages of this system are fast mounting, low weight, low costs, both the gaiter and the foot are replaceable and an artificial limb can be fitted without the need for an established workshop with machines (jig equipment), and other special equipment.

As an adhesive contact glue such as polyurethane glue or cyanacrylate glue or other suitable kinds of glue are used.

As stated above, all artificial limbs, including the artificial limb according to the present invention, have to be adapted to the amputation stump so that in the transition the artificial limb is a satisfactory fit, providing a pressure distribution on the amputation stump which is optimal for that particular stump and providing the pattern of movement which is normal for the individual patient.

Equipment for adapting the prosthetic sleeve to the amputation stump is advantageously collected in a set, with which the artificial lower leg according to the present invention is adapted to the amputation stump before the artificial foot is adjusted for adaptation to the patient's gait. A set of this kind will advantageously contain:

- a prosthetic sleeve fabricated in a suitable material, size and shape, an appropriate volume, e.g. 500 g, of a suitable moulding mass and packing for the purpose, - a suitable number, e.g. six, relief/strain cushions for use during adaptation,

- a suitable insulation bag, e.g. a latex sheath, for insulating the amputation stump during the adaptation process,

- a suitable reinforcing material, e.g. nylon stockinet for reinforcement of the moulding mass,

- glue for attaching the foot part to the gaiter.

The contents of the set will now be described in greater detail:

The prosthetic sleeve, the leg shell is prefabricated in a suitable material, such as polypropylene or carbon fibre composite. The prosthetic sleeve is made in different sizes, is open at the upper end and is designed so as to enable an amputation stump to be passed down into a sleeve of a suitable size. The prosthetic sleeve will serve as a foundation for the construction of the rest of the artificial limb and a foundation for absorption of forces from amputation stump to artificial limb.

The moulding mass is a liquid or viscous material of a single or multi- component type which under given conditions alters its structure to a solid but flexible material. In its liquid (viscous) form the moulding mass has to fill all the gaps between the amputation stump and the prosthetic sleeve and after being converted into a solid form represents a transition, an insertion, which can transfer forces from artificial limb to amputation stump in an appropriate manner, thereby creating an optimal fit between amputation stump and artificial limb.

The relief and strain cushions are prefabricated, soft, appropriately designed cushions in suitable material, e.g. the same as is used in the moulding mass. The cushions are applied on the amputation stump in areas which can withstand little or no pressure during the moulding process. When these cushions are subsequently removed, they will have left cavities inside the prosthetic sleeve which thereby provide relief for unstressed areas on the stumps. The cushions may also subsequently be glued into the inside of the prosthetic sleeve corresponding to the area on the stump which is capable of withstanding increased strain (patent NO-B 180 103).

The insulation bag is made of a thin elastic material, such as latex. It is open at the upper end and closed or capable of being closed at the lower end. The insulation bag is pulled over the amputation stump after the cushions have been applied and is in position during the moulding process. Apart from insulating the stump it will compress the stump's soft parts and help to create an optimal fit during moulding.

The reinforcing material is made of a suitable material such as nylon, with a suitable structure and may be in the form of a stocking with an opening at least at one end. This stocking can be pulled on outside the sheath on the amputation stump and/or inside the prosthetic sleeve before the moulding mass is poured down into the sleeve and the stump is inserted. The moulding mass will penetrate the stockinet which thereby will give the insert an increased strength and elasticity in its final form.

The glue will be a suitable contact glue, such as, e.g., polyurethane glue or cyanacrylate glue.

Claims

PATENT CLAIMS

1. An artificial limb which comprises a lower leg part (1) which is hollow and open at the upper, proximal end and closed at the lower, distal end, a solid gaiter part (2) and a solid foot part (3), securely connected to one another, characterized in that the lower leg part (1) is made of a rigid material and possibly filled with a core material, wherein the lower leg part's (1) distal end is provided with a flange, arranged in the toe-heel direction, of a suitable shape for connecting with a correspondingly shaped groove in the gaiter part (2), where the gaiter part's (2) distal surface is larger than its proximal surface, and where the distal surface is convex in a sagittal plane and concave in a frontal plane, with the result that it is adapted to the proximal surface of the foot part (2), where its surface is concave in a sagittal plane and convex in a frontal plane and where the foot's surface has a larger extension than the gaiter's (2) opposite distal surface.

2. An artificial limb as indicated in claim 1, characterized in that the flange on the lower leg part's (1) distal end has lateral walls (5) all of which slope outwards, thus forming an angle of less than 90° with the flange's bottom (4) which forms a part of the lower leg part's (1) bottom in both the sagittal plane and the frontal plane, and that the gaiter part's (2) groove is so formed that the flange on the lower leg part (1 ) fits exactly into the groove on the gaiter part (2).

3. An artificial limb as indicated in claims 1-2, characterized in that the said secure connection is provided by means of glue or screws.

4. An artificial limb as indicated in one of the preceding claims, characterized in that the rigid plastic material in the lower leg part (1) is preferably thermoplastic, that the solid gaiter part (2) consists of flexible, easily adhesive rubber or artificial rubber, preferably polyurethane and the solid foot (3) consists of flexible, easily adhesive rubber or artificial rubber, preferably polyurethane.

5. An artificial limb as indicated in one of the preceding claims, characterized in that the core material in the lower leg part (2) can be partly removed, with the result that the remaining material forms a foundation for moulding mass, and is preferably expanded polystyrene (EPS) or polyurethane.