GB2322803A

GB2322803A - Improved leg prosthesis

Info

Publication number: GB2322803A
Application number: GB9704713A
Authority: GB
Inventors: Catherine May Sunley
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-03-07
Filing date: 1997-03-07
Publication date: 1998-09-09
Anticipated expiration: 2017-03-07
Also published as: GB2322803B; GB9704713D0

Abstract

A leg prosthesis affording improved protection for the wearer against strain upon the residual limb has an inflatable air cushion (10) within its structure. In one form of the invention, the air cushion, which may be of toroidal shape, is retained within a cover of a rigid or stiff material, for example between the flat closed ends (11a, 12a) of two coaxial cylinders (11, 12).

Description

Improved Leg Prosthesis The present invention is concerned with artificial limbs and in particular with a prosthesis devised to replace a leg.

Leg prostheses are available in a wide variety of forms and it has been recognised that the design of such prostheses must take account of the heavy work which the prosthesis must perform in supporting the body in a range of different circumstances - and of the potential strain upon the residual limb. For example, the constant use of such an artificial limb by a person who has had the leg amputated at a point above the knee joint, and in particular the repetitive impact of the limb upon the wearer's body in normal use, may give rise to pain in the user's lower back.

Various proposals have been made to build some measure of shock absorption into artificial legs. For example, it has been proposed to provide such legs incorporating springs or pneumatic cylinders in order to absorb some of the axially-directed impacts upon the leg in use. However such prior proposed devices have often proved to be unsatisfactory or impractical in use.

It is therefore one object of the present invention to provide an improved leg prosthesis by which some at least of the disadvantages of existing such prostheses are reduced or avoided.

The leg prosthesis according to the present invention is characterised by having an inflatable air cushion within its structure. By means of that air cushion, the body of the wearer, and in particular the residual limb, is protected to a considerable extent from the effects of the repetitive impact of the foot or base of the artificial limb upon the ground.

The air cushion may be located in any position along the length of the artificial limb, including at one or other of the ends of the limb. However it is particularly preferred that it be built into the limb at a position intermediate the ends.

In the case of a limb which incorporates an artificial knee joint, the air cushion may be above or below that joint. The leg prosthesis according to the invention may be adapted for use by a person who has had the leg amputated either above or below the knee but is of particular benefit for above-theknee amputees.

The air cushion is made of any material having the necessary strength and flexibility to sustain the pressure entailed in supporting the user of the prosthesis. Thus for example it may be made of a natural or synthetic rubber or of another suitable synthetic polymeric material. It is particularly preferred that the cushion be retained within a cover of a rigid or stiff material, for example a generally cylindrical such cover, both to protect the cushion against external damage and to provide additional support for the cushion.

Such a cover may for example be of metal or of a synthetic polymeric material.

In one preferred form of the prosthesis according to the invention, the air cushion is disposed between the flat ends of two coaxial cylinders, within the outer cylinder, the two cylinders being connected to respective upper and lower parts of the shaft of the artificial leg. Very preferably, the capacity for relative axial movement of the two cylinders is limited, for example by means of a bolt extending, preferably axially, between the cylinders.

It is particularly preferred that means be provided for adjusting the air pressure within the air cushion. Thus the cushion may advantageously have an air valve, which preferably can be operated to permit air to pass either into or from the air cushion. The valve may be combined with an adaptor, by means of which an air line may be attached. In this way the air pressure may be raised by means of a bicycle pump or other handoperated pump, for example a pocket-sized pump specifically for that purpose, or using a compressedair container, which also may be either an existing product or one devised specifically for carrying in a pocket or handbag. By varying the air pressure in this way, the prosthesis may be adjusted to take account of the circumstances in which it is being worn, for example for work or sport, or when it is required to support an increased load, for example when the user is carrying a suitcase or shopping.

Preferably the prosthesis is of adjustable length, for example to accommodate situations wherein the user wishes to dispense with footwear, or to wear heels of different height, or to fit a different base to the artificial limb. In one form of the present invention, two adjacent sections of the length of the prosthesis can be screwed or otherwise adjusted in a manner to increase or decrease their mutual overlap and thereby adjust their overall length.

If the prosthesis is intended for wear by a person whose leg has been amputated from above the knee, it preferably incorporates an artificial knee joint, most preferably one which allows the leg to be locked in its straight condition, for example automatically when the leg is straightened.

In one form of the invention, the prosthesis has interchangeable base parts or feet, to permit bases having different functions, for example different treads, to be interchanged.

The invention will now be further described with reference to the accompanying drawing, which illustrates, in vertical sectional view, a detail of one preferred embodiment of the improved leg prosthesis according to the present invention.

In the illustrated embodiment, a toroidal, inflatable air cushion 10 is a close fit within the space formed between the flat closed ends lia, 12a of two coaxial cylinders 11, 12 respectively.

A bolt 13, secured in position by a nut 14, extends between the cylinder ends and through the axial centre of the cushion 10, thereby limiting the extent to which the cylinders can move apart.

Air under pressure can be introduced into the cushion by means of a valved adaptor 15.

The lower end of the cylinder 12 threadedly engages the inner face of the upper end of a cylindrical hollow shaft 16, into which it can be screwed to a greater or lesser extent in order to vary the overall length of the prosthesis.

When the desired length has been achieved, the cylinder 12 and shaft 16 are secured in fixed relative positions by a lock nut 17.

The illustrated device is secured, by conventional attachment means not shown, to the upper and lower components of the leg prosthesis, incorporating respectively a socket for the residual limb and a base block or foot. The air cushion 10 is inflated to the pressure desired for normal wear. Via the adaptor 15, additional air may be introduced into the cushion when more strenuous activity is to be undertaken or when the user is to carry an increased load, the air pressure being subsequently reduced to the desired normal level by release of air through the adaptor.

Claims

1. A leg prosthesis characterised by an inflatable air cushion within its structure.

2. A leg prosthesis as claimed in Claim 1, wherein the air cushion is built into the prosthesis at a position intermediate the ends of the latter.

3. A leg prosthesis as claimed in Claim 1 or Claim 2, incorporating also a knee joint.

4. A leg prosthesis as claimed in Claim 3, wherein said knee joint is lockable in its straight condition.

5. A leg prosthesis as claimed in any of the preceding claims, wherein the air cushion is formed of a natural or synthetic rubber or another synthetic polymeric material.

6. A leg prosthesis as claimed in any of the preceding claims, wherein the air cushion is retained within a cover of a rigid or stiff material.

7. A leg prosthesis as claimed in Claim 6, wherein said cover is generally cylindrical in shape.

8. A leg prosthesis as claimed in Claim 7, wherein the air cushion is disposed between the flat closed ends of two coaxial cylinders, within the outer said cylinder.

9. A leg prosthesis as claimed in Claim 8 having means to limit the capacity for relative axial movement of said two cylinders.

10. A leg prosthesis as claimed in Claim 9, wherein said movement limiting means is a bolt extending between said two cylinders.

11. A leg prosthesis as claimed in any of the preceding claims, having means for adjusting the air pressure within the air cushion.

12. A leg prosthesis as claimed in Claim 11, wherein said pressure adjusting means comprises a two-way valve.

13. A leg prosthesis as claimed in Claim 11 or Claim 12, incorporating an adaptor for attachment of an air line.

14. A leg prosthesis as claimed in any of the preceding claims, which is of adjustable length.

15. A leg prosthesis as claimed in Claim 14, wherein two adjacent sections of the length thereof are adjustable to increase or decrease their mutual overlap.

16. A leg prosthesis as claimed in any of the preceding claims, wherein said air cushion is of toroidal form.

17. A leg prosthesis substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawing.