WO2004066890A1 - Orthopaedic device - Google Patents

Abstract

An orthopaedic device for treating a contractive of the lower leg which holds the foot in the open condition comprises a close fitting gaiter (15), a close fitting shoe (18), and one or more gas struts (25) extending therebetween so as to urge the foot towards the closed condition. The device preferably includes a lower member (22) housed in a side pocket (21) of the shoe and extending rearwardly thereof to gas strut (25).

Description

Orthopaedic Device

This invention relates to an orthopaedic device for treating contractures of muscle and tendon in the lower leg.

Certain medical conditions are characterized by a shortening of the Achilles tendon or of the posterior tibial muscles. Typically the shortened tendon or muscle holds the foot at an obtuse angle, and the patient is unable to pivot the foot about the ankle joint so as to permit standing or walking. Typically treatment is by physiotherapy in which the tendon or muscle is stretched by the application of a pivoting force to the foot. The application of such a force requires physical effort, and only be sustained by a physiotherapist for a few minutes. Moreover, since the ankle joint is capable of some lateral movement, the physiotherapist must take care to apply the restoring force precisely at right angles to the pivot axis of the ankle, and this degree of control is somewhat difficult to achieve.

Other proposals require immobilization of the lower leg/foot with the tendon/muscle in a stretched condition. This is typically achieved by application of a plaster cast, but is disadvantageous because the patient is immobilized for a few days or a week. Furthermore a plaster cast becomes progressively less rigid over time and may allow the tendon/muscle to relax or move laterally, both of which are undesirable. Finally it is of course difficult to hold the foot precisely at right angles to the axis of the ankle joint whilst the cast is applied and is setting.

What is required is an improved means of precisely holding the lower leg and foot of a patient whilst permitting the tendon/muscle to be stretched with a substantially constant predetermined force, and which is relatively easily applied and removed from a patient.

According to the invention there is provided an orthopaedic device for treating a contracture of the lower leg which holds the foot in an open condition, the device comprising lower member for attachment to a close fitting shoe within which the heel is substantially immobilized, and an upper member for attachment to a close fitting gaiter within which the leg is substantially immobilized, the lower and upper member being connected by a hinge having an axis substantially coincident with the pivot axis of the ankle, and the device further comprising a gas strut operably connected at one end to the upper member and at the other end to the lower member whereby, in use, the foot is urged towards a closed condition.

In this specification the open condition of the foot describes the most obtuse angle between leg and foot, and the closed condition describes the most acute angle. By 'shoe' is meant an enclosure of the foot which may or may not be suitable for walking.

Such a device when attached to a shoe and gaiter ensures immobilization of the ankle joint in the lateral direction, and the precise application of a stretching force in the length direction of tendon/muscle. A gas strut has the known advantage of being capable of applying a substantially constant force over a significant travel, thus ensuring that the contracture is stretched at a precisely predetermined level of force.

The invention also has the substantial advantage that, once applied to the patient, no inadvertent relaxation of the stretching force is possible. Accordingly the treatment can be applied in accordance with predetermined parameters, and the risk of misuse, overuse or underuse can be avoided. In particular the patient can be treated and monitored by suitably trained but lesser skilled medical personnel.

The device can be easily fitted and removed and thus treatment for several hours is easily achieved. The disadvantages of repeated short applications of force or long term immobilization are thereby avoided. Repeated treatments can be effected using settings which are accurately reproducible.

Preferably the gas strut is to the side of the leg. In a preferred embodiment, the lower member is formed as part of the shoe, and the upper member is formed as part of the gaiter so that the device is entirely self-contained. The lower and upper members are preferably integrated in the respective shoe and gaiter, to provide a lightweight and slim assembly. Nevertheless, for reasons of practicality it is envisaged that means for attachment of the device to a separate shoe or gaiter or both may be necessary or desirable in some circumstances.

In a preferred embodiment immobilization of the ankle is achieved by the use of a close fitting sock moulded by conventional techniques from a cast of the patient's foot. The sock is preferably of polypropylene and thus relatively rigid. In use the sock forms part of the shoe of the device. Alternatively the shoe may be directly moulded from a cast of the patient's foot.

The gaiter can be of any suitable material, for example polypropylene, which can provide the necessary degree of rigidity and support for the hinge joint. The gaiter may for example be strapped around the patient's leg, and may if desired extend above the knee so as to substantially immobilize the knee joint.

Preferably the gas strut acts on a rearwardly directed cantilever portion. Such an arrangement can avoid unnecessary thickness of the shoe in the region of the heel which would be required in the case of direct mounting of the strut. The cantilever portion is preferably located in a rear facing pocket of the lower member or of the shoe, and in the preferred embodiment is at the side thereof. Such an arrangement permits fore and aft adjustment of the cantilever portion and thus the lever ratio of the strut about the hinge axis. The cantilever portion also permits forces to be transmitted over a significant area of the shoe rather than via a single pivot mounting.

By mounting the cantilever portion to the anterior of the ankle joint, the force of the strut is in use applied to the sole of the foot via the shoe. This force is a compressive force and is distributed over a significant area; in contrast the application of force directly to the heel requires application of a tensile force to the foot, and a rather close fitting heel cup of the shoe.

The gas strut of the invention urges the device to the closed condition. In order to fit the device to a patient, the strut must be tensioned in order to move the shoe towards the open condition, and the device preferably includes tensioning apparatus. In a preferred embodiment the tensioning apparatus comprises an inextensible strap extending from the lower member to the upper member and adapted to be shortened. In the integrated version, the strap can extend directly from the shoe to the gaiter. Preferably the strap includes a latch to hold the device in a desired open condition. The strap may comprise a belt having one end fixed on the upper member or gaiter, and the other end running through a loop defined by the lower member or shoe, and preferably on the heel of the shoe. Pulling the strap through the loop causes shortening thereof so that the shoe is pulled against the effect of the strut to the open condition. The strap may include a hook and loop fastener as the latch, whereby a region of the free end can be secured to the fixed end.

In a preferred embodiment a pair of matched gas struts are mounted on either side of the leg so as to apply the restoring force to the posterior of the ankle joint. This arrangement provides additional stability to the device, and helps to avoid the risk of lateral movement of the ankle joint.

A pair of cantilever members may be provided in side pockets of the lower member or shoe, one each being associated with a respective gas strut. In a preferred embodiment these cantilever members extend in use generally parallel to the sole of the shoe and are immediately adjacent the sole. The pockets are preferably located to the anterior of the ankle joint. The cantilever members preferably terminate at one end close to the posterior surface of the foot, so as not to cause discomfort when the patient is lying down.

Preferably the ram of the gas strut is at the bottom whereas the body is at the top. This arrangement gives greater clearance in the region of the hinge, and thus greater design freedom.

Other features of the invention will be apparent from the following description of a preferred embodiment shown by way of example only, and in which:- Fig. 1 illustrates a human leg and foot.

Fig. 2 illustrates a preferred embodiment of a device according to the invention.

Fig. 3 illustrates a half-section on line 3-3 of Fig. 2.

Fig. 4 illustrates a half-section on line 4-4 of Fig. 2.

Fig. 5 illustrates a tensioning strap of the device, and

Fig. 6 illustrates a preferred embodiment from the front.

With reference to the drawings Fig. 1 shows a human leg 10 with a foot tending towards an open condition due to a contraction force in the Achilles tendon or posterior tibial muscles, represented by arrows 11. As a result the foot tends to pivot anticlockwise about ankle joint 12, as represented by arrow 13. This medical condition is uncomfortable and makes walking difficult if not impossible. It often applies to both legs, and is treated by stretching the contractile tissues in a controlled and predetermined manner.

Figs. 2-4 illustrate a device 14 for treating this condition. A gaiter 15 is open at the front and sized to closely engage a patient's leg. Typically the gaiter is moulded of polypropylene and is conformable to the leg contours. The mouth 16 (Fig. 3) may have flexible lips 17 to permit easy entry of the leg, and securing means (such as hook and loop fasteners) may be used to strap the gaiter securely in place.

A shoe 18 is attached to the gaiter by means of hinges 19 intended to be substantially coincident with the pivot axis of the patient's ankle. A hinge is provided symmetrically on either side of the device, and the ends thereof may be housed in pockets 20 of the gaiter and shoe, as illustrated.

The shoe 18 substantially encircles the patient's foot and is a very close fit over the posterior part and in the region of the heel. The shoe may be moulded directly from a plaster cast of the patient's foot, but preferably the patient is provided with a moulded sock (not shown) which is itself a very close fit in the shoe. This latter technique simplifies moulding somewhat, and the shoe may in fact be moulded directly over the sock. Both shoe and sock are typically of polypropylene, and having a respective wall thickness of 4.5 mm and 2.5 mm.

A pocket 21 is provided on either side of the shoe for respective rear facing arms 22 which are generally parallel to the sole of the foot/shoe and to each other. The arms are rigidly secured in a respective pocket 21 by any suitable means, such as one or more rivets or screws 23 (Fig. 4). The arms are of any suitably stiff material, such as aluminium.

The free ends of the arms 22 terminate approximately level with the posterior of the heel cup 24.

A gas strut 25 extends on either side of the device from the free end of a respective arm 22 to a respective side of the gaiter 15, as illustrated, and is arranged to urge the shoe in the direction of arrow 26 to the closed condition.

Fig. 6 illustrates the general appearance of the device from the front, and showing the mouth 16 of the gaiter 15, and mouth 27 of the shoe 18. (Other parts of the device are omitted for reasons of clarity).

In use the foot and leg are slipped into the device from the front side, assisted by partial opening of the mouths 16,27 if necessary. The gaiter and shoe may be further secured for example by the use of external circumferential straps of any suitable kind, or by elastic clips over the respective mouth of gaiter and shoe.

In order to fit the device comfortably the shoe is moved to the open condition by means of a strap 31 illustrated in Fig. 5. The strap 31 is riveted at one end to the back of the gaiter 15, and passes through a loop 32 of the shoe to a free end 33. A hook and loop fastener 34,35 is provided on facing sides of the strap in order to secure the free end in a predetermined position. In use the strap is tensioned by pulling in the direction of arrow 38 until the shoe is at the desired orientation, and then locked by use of the fastener 34,35. Once the leg and foot are in position the latch is released to permit the struts 25 to tension the muscles/tendons.

The tensioning force can be relieved, if necessary, by relatching the strap 31.

The struts 25 are mounted to respective stiffeners 36 of e.g. aluminium which are housed in pockets of the gaiter, and extend longitudinally of the leg as illustrated (Fig. 3). By this means the operational force is adequately supported, and several spaced mounting points can be provided if desired. Furthermore the lower end of the struts can also have spaced mountings on the arms 22, via which the lever ratio of the struts can be varied. The arrangement permits use of standard struts of a variety of lengths, and a relatively easy change of restoring torque from a standard strut exerting a substantially fixed effort. It will be appreciated that the lever ratio may also be varied by adjusting the depth of the arms in the respective pockets 21.

In use the struts typically exert a combined torque in the range 8-12 Nm, and contain a relatively thick oil to ensure that movement of the ram is heavily damped.

It will be understood that the upper and lower mountings defined by stiff ener 36 and arm 22 could be adapted for external attachment to a respective gaiter and shoe, by suitable external clamps or screws. Such an arrangement would tend to be more bulky, but may be appropriate in certain clinical circumstances or for example where an immediate temporary treatment is required in the absence of suitably tailored gaiter and/or shoe.

Claims

Claims

1 An orthopaedic device for treating a contracture of the lower leg which holds the foot in an open condition, the device comprising lower member for attachment to a shoe adapted for substantial immobilization of the heel and an upper member for attachment to a gaiter adapted for substantial immobilization of the leg, the lower and upper member being operatively connected in use by a hinge having an axis substantially coincident with the pivot axis of the ankle, and the device further comprising a gas strut connected at one end to the upper member and at the other end to the lower member whereby, in use, the foot is urged towards a closed condition.

2. A device according to claim 1 and further including a shoe and a gaiter respectively attached to the lower and upper members, and hinged about said pivot axis.

3. A device according to claim 2 and further including a close fitting sock.

4. A device according to claim 3 wherein said sock is of polypropylene.

5. A device according to any of claims 2-4 wherein said gaiter is of polypropylene, and adapted to be strapped around the leg.

6. A device according to any of claims 2-5 wherein said lower member is a rearwardly directed cantilever member of said shoe.

7. A device according to claim 6 wherein said cantilever member is located in a rear facing side pocket of said shoe.

8. A device according to any preceding claim and further including tensioning apparatus comprising an inextensible strap extending from the lower member to the upper member and adapted to be shortened.

. A device according to any preceding claim wherein the ram of the gas strut is at the bottom and the body of the gas strut is at the top, in use.

10. A device according to any preceding claim and having a pair of matched gas struts mounted so as to extend on either side of the leg.