GB2103490A

GB2103490A - Artificial limb socket

Info

Publication number: GB2103490A
Application number: GB08222707A
Authority: GB
Inventors: Herbert Thompson; John Jeffrey Shorter
Original assignee: Blatchford & Sons Ltd; Chas A Blatchford and Sons Ltd
Current assignee: Blatchford & Sons Ltd; Chas A Blatchford and Sons Ltd
Priority date: 1981-08-14
Filing date: 1982-08-06
Publication date: 1983-02-23
Also published as: GB2103490B

Abstract

An artificial limb socket intended mainly for use as a temporary socket for primary amputees has overlapping wall portions (1,2) to allow adjustment of the internal diameter of the socket. The socket is cut from a single vacuum formed socket blank from which material has been removed on opposite sides to form wall portions which are connected together by an integral flexible hinge portion (3) adjacent the base portion (4) of the socket. The integral construction of the socket has advantages over prior art adjustable sockets in terms of the time required in manufacture and the amount of material used. <IMAGE>

Description

SPECIFICATION Artificial limb socket This invention relates to an adjustable socket for an artificial limb.

In the artificial limb field adjustable sockets are know, their use being mainly as temporary sockets form'mary amputees. Following amputation of a leg, the volume of the stump generally changes over a period of a few months. If the amputee is to make the best use of a temporary artificial limb during that period, a socket is required which will accommodate such volume changes, the diameter of the socket being gradually adjusted until the stump has stabilised and a tailor-made socket can be produced.

One known adjustable socket for an above-knee amputee comprises two vacuum-formed polypropylene halves which overlap to an extent determined by two or three straps which encircle the socket. In the lower portion of the socket the two component halves overlap completely to form a double skin end portion to which, for example, the knee mechanism is attached. The two halves of the socket are separately moulded. Due to the shrinkage characteristics of polypropylene as it cools, it is necessary to use the first half as the mould over which the second half is vacuum-formed, each half then being trimmed to shape. In this way the two halves can be made to fit together relatively accurately. The two halves are clamped together at the lower end of the socket between a pair of plates which mount the rest of the artificial limb.

It is an object of this invention to provide an adjustable socket which can be produced more economically both in terms of material and in time required.

According to this invention, a socket for an artificial limb has a socket wall which is divided into two or more wall portions arranged to overlap each other and to be movable relative to each other so that the size of the socket can be adjusted, wherein the wall portions are integrally formed as part of a one-piece moulded thermoplastics component. A socket in accordance with the invention preferably has two integrally moulded halves which overlap on either side of the socket by an integral flexible hinge portion which allows adjustment of the size of the socket by pivoting of one half relative to the other.In the case of an above-knee amputee, the socket may be split into an anterior half and a posterior half, with each half overlapping the other on the medial and lateral sides, adjustment being provided by anterior-posterior pivoting of the anterior half relative to the posterior half.

The preferred material for the socket is polypropylene co-polymer. The socket can be produced from this material byvacuum-forming over an internal mould to produce an over-size socket with a single continuous wall. This enlarged socket is then trimmed to produce cut-outs in the side walls extending from the open end of the enlarged socket down to the ends of the required hinge portion, so defining two socket halves which can then be pushed together with their edges overlapping to form a socket of the required size.

The two halves are preferably held in the required relative position by straps attached, for example by rivetting, to the posterior half, and arranged to pull the anterior half inwardly towards the posterior half.

Adjustable length straps allow the size of the socket to be adjusted. In cases where adjustment is to be reserved for the prosthetist, replaceable fixed length straps may be provided, or rivets may be driven through the overlapping portions of the two halves.

A socket in accordance with the invention has the advantage overthe prior art two-piece socket that only one vacuum-forming operation is required instead of two. Secondly, less material is wasted.

Also, only one trimming operation is required.

The trimming operation in particular is a skilled job, and the invention considerably reduces the time required for this part of the process.

The invention will now be described by way of example with reference to the drawings, in which: Fig. 1 is a lateral side view of a right socket for an above-knee amputee; Fig. 2 is a medial side view of the lower portion of the socket of Fig. 1; Fig. 3 is a partly sectioned anterior view of the socket of Fig. 1; Fig. 4 is a sectioned top plan view taken along the line IV-IV in Fig. 3; Fig. 5 is a lateral side view of a one-piece moulding from which a left socket is produced; and Fig. 6 is a lateral side view of the moulding of Fig. 5 after trimming and closing in.

Referring to Figures 1 to 4, an above-knee socket forthe right leg is formed from a one-piece polypropylene vacuum-formed moulding, and comprises an anterior half 1 having rear edge portions which are overlapped by the front edge portions of a posterior half 2, the two halves being connected by an integral anterior hinge portion 3 adjacent the base 4 of the socket.

The degree of overlap of the two socket halves 1 and 2 is determined by straps 5, 6 and 7 attached to the posterior half 2 by rivets 8, 9 and 10. In this embodiment the straps are provided with Velcro hook and loop strips (11 and 12 respectively) so that each strap can be tensioned by looping its free end through a ring 13 (see Fig. 2) attached to the medial side of the posterior half 2 and by bringing the two Velcro strips together.

The posterior half 2 has a flat raised area 14 for mounting a hip joint connection.

The socket is attached to a knee joint mechanism by means of an internal mounting plate 15 which preferably forms part of the mould over which the socket is vacuum-formed. The base 4 of the socket is sandwiched between the plate 15 and an external plate (not shown) forming part of the knee mechanism by means offourthreaded nuts 16 recessed in the plate 15.

The method of manufacturing a socket in accordance with the invention will now be described with reference to Figures 5 and 6 which show a socket for a left leg. The first step is the vacuum-forming of an oversize continuous-walled socket as shown in outline by the unbroken line in Fig. 5. The starting point is a cup-shaped polypropylene preform, or a polypropylene sheet which has been heated and allowed to drape freely into the cup shape. This is heated and draped over an internal mould capped by the plate 15 (Fig. 3). The mould has a step to produce a tuber seating portion 17 in the socket adjacent the top rear edge 18, and a flat plate may be attached to the mould to produce the raised hip joint connection area 14 referred to above. Air between the mould and the draped polypropylene sheet is evacuated to vacuum-form the socket, and the moulding is allowed to cool.

The second step is the trimming of the moulding to remove the shaded areas in Fig. 5, and in particularto make a tapered cut-out 19 in each side of the moulding. The lower end of each cut-out is terminated by a small hole 20, these two holes defining the ends ofthe hinge portion 3 (see Fig. 4) and serving to minimise cracking and to assist subsequent overlapping of the two halves of the socket. The wall of the socket in the hinge portion follows a substantially straight line between the holes 20.

The final step is to draw the anterior half 1 towards the posterior half 2 which results in a tapered overlap region 21 on each side extending from the hole 20 to the top edge. At this stage the socket may be reheated gently to stabilise the moulding in the overlapping configuration.

The shape of the moulding is such that a preset angle of knee flexion is built into the socket, as indicated by the line 22 drawn perpendicular to the base 4 in Fig. 6, which line makes an angle of 5 in this embodiment with the central axis 23 of the socket.

Claims

1. A socket for an artificial limb having a socket wall which is divided into two or more wall portions arranged to overlap each other and to be movable relative to each other so that the size of the socket can be adjusted, wherein the wall portions (1, 2) are integrally formed as part of a one-piece moulded thermoplastics component.

2. A socket according to claim 1, wherein the socket wall comprises two side wall portions (1, 2) connected together through an integral flexible hinge portion (3) extending transversely at or adjacent a distal end of the socket.

3. A socket according to claim 2, wherein one of the wall portions (1,2) includes a base portion (4) at the distal end of the socket for mounting an endoskeletal load-bearing member, and wherein the hinge portion (3) extends transversely of the socket adjacent the edge of the base portion (4).

4. A socket according to claim 2 or claim 3 for an above-knee amputee, wherein the wall portions comprise an anterior wall portion (1) and a posterior wall portion (2) extending from the hinge portion (3) to the proximal end of the socket, and overlapping each other on both the medial and lateral sides of the socket.

5. A socket according to any preceding claim including adjustable straps (5, 6, 7) attached exter nally to at least one of the wall portions (1, 2) for drawing the wall portions together to a required degree of overlap.

6. A socket according to any preceding claim, characterised by having been formed from a vacuum-formed thermoplastics moulding in the shape of an oversize socket, the sides of the moulding having been cut lengthwise from one end to points adjacent the other end to form the said wall portions.

7. A socket according to claim 6, including rounded cut-outs at the said points.

8. A socket according to any preceding claim wherein one of the wall portions (1, 2) includes a raised planar area (14) for external mounting of a side support member.

9. A socket according to claim 3, including a mounting plate (15) fitted internally to the base portion (4).

10. A method of making an adjustable artificial limb socket, comprising moulding an oversizethermoplastics socket blank having a closed end and an open end, cutting the blank lengthwise from the open end to points adjacent the closed end to produce at least two wall portions which can be moved relative to each other about a hinge portion adjacent the closed end, and bringing the wall portions together in an overlapping relationship.

11. A method according to claim 10, in which tapered sections (19) are removed from opposite sides of the socket blank to form two separate wall portions, the edges of the openings so formed being terminated by a hole (20) to minimise cracking.

12. A method according to claim 10 or claim 11, wherein the socket blank is vacuum-formed over a mould including a plate which is then removed with the blank to form a mounting plate fitted internally to the said closed end.

13. An artificial limb socket constructed and arranged substantially as herein described and shown in the drawings.

14. A method of making an artificial limb socket substantially as herein described with reference to the drawings.