GB2082074A - Device for relative adjustment of limb components - Google Patents

Abstract

An alignment device for an artificial limb has means (13,15 and 2,4,5) for attaching the device to a limb socket (7) and an outer limb structure (1) so as to provide a temporary, external connection between the socket and the outer limb structure. The device has joints with screw clamps to allow the relative alignment of the outer limb structure and the socket to be adjusted both rotationally and linearly, and to allows walking trial to be performed. When a required alignment has been established, the device is used to maintain the relative positions of the socket and the outer limb structure whilst a permanent connection is formed between them, where upon the device is detached from the limb. <IMAGE>

Description

SPECIFICATION Alignment device for an artificial limb This invention relates to an alignment device for setting and adjusting the position of one component of an artificial limb relative to another component of the limb. The device is intended primarily for use as a temporary alignment coupling prior to the permanent mounting of one component on the other.

When an artificial limb, for example an above-knee leg prosthesis, is being fitted to a patient it is generally necessary to adjust the position of the knee mechanism and the parts of the limb below the knee relative to the stump socket. This adjustment is normally carried out with the patient wearing the limb. Alignment devices for such a limb fall into two groups: (i) devices which form a permanent cou pling between the stump socket and the rest of the limb, and occupy the space between the end of the socket and the knee mechanism; and (ii) devices which form part of the limb during fitting but which are removed once the correct alignment has been established and are replaced by a lighter, permanent fixed coupling.Devices of the latter group have the advantage that they do not contribute to the weight of the limb after fitting, but known devices in this group have to be removed while the permanent coupling is formed and therefore require the use of a jig to hold the socket and the knee mechanism in the aligned position until the permanent coupling is completed.

In the case of a patient with a long stump, there may be insufficient clearance between the lower end of the socket and the knee axis to accommodate a known alignment device, whether permanent or temporary, between the socket and the knee mechanism. It is then encessary to use, for example, side steels adjustably mounted on both sides of the socket, but these suffer from the disadvantage that the alignment is difficult to carry out and is therefore relatively time-consuming.

It is an object of this invention to provide an alignment device which overcomes or at least mitigates these drawbacks.

According to this invention there is provided an alignment device for an artificial limb for external and detachable mounting on the limb, wherein the device includes first and second mounting elements for removably attaching the device to respective parts of the limb requiring alignment relative to each other, the mounting elements being connected to one another by a connecting structure including a joint or joints allowing rotational and translational adjustments of the position of the first mounting element relative to the second mounting element to be made.This device serves to connect temporarily one part of the limb relative to another part of the limb so that, firstly, adjustment of the relative position of the two parts may be carried out so as to permit a walking trial, and secondly, a permanent, fixed connection which preserves the alignment may be built up or fabricated before the device is removed from the limb. The device can then be re-used on another limb.

In its preferred embodiment, the device allows linear medial and lateral adjustments, linear anterior-posterior adjustments 3600 rotation about the longitudinal axis of the socket, and angular adjustments including flexion or extension and adduction or abduction. Unlike several known devices it also allows lengthening and shortening adjustments.

Since it is an externally mounted device it can be used with a limb in which there is minimal clearance between the socket and the knee mechanism. It need not be removed while a fixed connection is being built up or fabricated since it does not occupy the space required for such a connection. Therefore the use of a special jig, with which it is often difficult to maintain the alignment when the alignment device is removed, is avoided.

The preferred embodiment includes a plurality of adjustable joints which are calibrated so that the prosthetist can record settings and thus return the alignment to a previously noted position.

The method of mounting the device on the limb depends on the material and configuration of the limb components. The device is suitable for use with a thermoplastics socket or socket container, to which it may be attached by external clamps or straps.

Other methods of attachment include screwing, rivetting, or by permanently sandwiching an attachment plate in the prosthesis. Attachment to different types of knee mechanism can be achieved by using different interfacing plates or other intermediate components which may either be removable with the alignment device or may form a permanent part of the limb.

It is envisaged that the device will be used particularly in the alignment and assembly of a limb which, in its final form, has a polyurethane foam connection between a thermoplastics socket and a metal cup mounted on a knee mechanism. The method of assembly would include the steps of attaching the alignment device to the socket by means of straps, mounting the rest of the limb on the lower part of the device using, for example, a pair of bolts inserted through holes drilled in the metal cup.

Alignment would then be carried out by adjusting and tightening the joints of the device so that a walking trial can be performed. When a satisfactory alignment has been achieved, and the limb removed from the patient. With the socket and the rest of the limb still held in alignment by the device, the space between the socket and the cup is enclosed by some form of shuttering, for example, poly thene sheet, and a liquid polyurethane foaming mixture is poured into the space. Once the foam has set, the alignment device can be removed and the foam trimmed so that its outer surface forms a smooth transition from the socket wall to the edge of the cup. In some cases the foam itself is sufficient to provide the required strength, in which case, a compatible adhering material, for example an acrylic plastic, is preferably used for the socket and the cup.The cup may also be provided with projecting pins or the like to act as a key for the foam. Normally, however, load-bearing sleeve of thermoplastics or glass-fibre reinforced material is moulded around the socket and the foam coupling.

Alternative method of forming a permanent coupling include filling the space below the socket with a plaster-of-paris or wax mould, and then removing the alignment device, removing the knee mechanism from the metal cup, and vacuum forming a polypropylene sleeve or container around the mould and the socket. In the case of a plaster-of-paris mould, the sleeve is cut to enable withdrawal of the mould and then welded back in place. With a wax mould, the wax is melted and allowed to drain out through a small hole in the sleeve.

During fitting of the limb, extra rigidity may be obtained by inserting a platform in the space below the socket to take the load on the limb when it is bearing the patient's weight This platform may be adjustably mounted on the cup to allow for different socket-to-cup distances as the alignment device is adjusted. When a satisfactory alignment has been achieved, the platform is removed and alignment preserved by the alignment device along whilst the permanent coupling is formed.

The invention will now be described by way of example with reference to the drawings in which: Figure 1 is a side view of an alignment device mounted on a metal cup and strapped to an above-knee socket; Figure 2 is a rear view of part of the device of Figure 1,viewed in the direction of the arrow "2" in Figure 1; Figure 3 is a plan view of the device, sectioned on the line A-A in Figure 1; and Figure 4 is a sectional plan view of an attachment plate of the device, viewed in the direction of the arrow "4" in Figure 1.

Referring to Figures 1 and 3, the alignment device is attached to a metal cup 1 (shown vestigially) by a pair of bolts 2 fixed in a base member 3 of the device, and clamped by a bridge 4 and knurled nuts 5. The cup 1 is a permanent part of the limb and is attached to a knee mechanism not shown in the drawings by means of a bolt passing through a slot 6 in the base of the cup.

The bolts 2 are preferably shrouded by plastics tubes (not shown) in the cup 1, so that the alignment device can be easily removed from cup 1 after a permanent foam coupling has been formed in the space between the socket 7 and the cup 1. The slot 6 extends in a direction perpendicular to the plane of Figure 1 and allows the cup 1 and the alignment device to be moved linearly in the same direction so as to provide medial-lateral adjustment of the socket 7 relative to the knee mechanism. The mounting of the cup 1 also allows rotation of the socket through 3600 about the longitudinal axis of the limb.

The base member 3 has two side members 8 housing a fixed horizontal shaft 9 which supports an upright arm in two parts 10A and 10B. Part 10A is clamped on and rotatable about the shaft 9 for flexion-extension adjustment. A scale 11 is provided for this adjustment. The part 1 0A has a second screw clamp at its upper end housing the upper part 10B of the arm which is circular in cross-section for rotational adjustment. The corresponding circularsection receptacle in the lower part 10A extends below the upper clamp to allow relative vertical movement of the part 1 OB as a means of lengthening or shortening the limb above the knee. The top end of the part 1 OB also has a screw clamp and mounts a circular section horizontal arm 12 with a socket attachment plate 13. This latter clamp is also seen in Figure 2, and allows longitudinal sliding of the arm 12 for linear anterior-posterior adjustment, and rotation of the arm 12 for abduction-adduction adjustment. A scale 14 is provided for recording abduction-adduction settings. The arms 10B and 12 have ring markings or grooves for indicating linear adjustment settings.

The attachment plate 13 has two angles inner faces 14 (Figure 4) for contacting the outer surface of sockets 7 of varying diameters. The faces 14 are preferably rubber-lined to grip the socket. Adjustable straps 15 are used for clamping the attachment plate 13 to the socket 7.

Claims (15)

1. An alignment device for an artificial limb for external and detachable mounting on the limb, wherein the device includes first and second mounting elements for removably attaching the device to respective parts of the limb requiring alignment relative to each other, the mounting elements being connected to one another by a connecting structure including a joint or joints allowing rotational and translational adjustments of the position of the first mounting element relative to the second mounting element to be made.

2. A device according to claim 1, wherein the connecting structure includes at least two joints allowing rotational adjustment about respective axes which are substantially perpendicular to each other.

3. A device according to claim 2, wherein the connecting structure comprises an intermediate member having a joint surface at each end, at least one of the joint surfaces being cylindrical in form and engaging a corresponding cylindrical surface on the first mounting element, which element is thereby movable both rotatably and linearly relative to the intermediate member.

4. A device according to any peceding claim wherein the or each joint includes a screw clamp.

5. A device according to any preceding claim for an artificial leg, wherein the first mounting element includes a clamp for securing a clamping surface on the element to the side wall of a stump socket or socket container, and wherein the second mounting element includes a clamp for securing the second element to a lower leg component.

6. A device according to claim 5, wherein the first mounting element extends laterally from the clamp ing surface to an upper adjustable joint which connects the element to a downwardly extending intermediate member, the upper adjustable joint allowing rotation of the first mounting element about an axis extending laterally from the clamping surface, and linear movement parallel to the said axis.

7. A device according to claim 6 wherein the intermediate member is coupled to the second mounting element via a lower adjustable joint allowing rotation of the second mounting element relative to the intermediate member about an axis substantially perpendicular to the axis defined by the upper adjustable joint.

8. A device according to claim 5 for an aboveknee artificial leg, the second mounting element including means for removably securing the element to an artificial knee mechanism, wherein the first mounting element is coupled to an intermediate member by an upper adjustable joint allowing anterior/posterior shift adjustment and abduction/ adduction rotational adjustment, and wherein the second mounting element is coupled to the intermediate member via a lower adjustable joint allowing flexion/extension adjustment.

9. A device according to claim 8 wherein the intermediate member includes a joint for limb length adjustment.

10. A device according to claim 8 or claim 9, wherein the second mounting element includes a clamp in the form of a pair of bolts extending laterally from the intermediate member for insertion through a lower leg component from one side, and a removable bridge arranged to be secured over the distal ends of the said bolts to clamp the other side of the lower leg component.

11. A device according to claim 6, wherein the clamping surface of the first mounting element has two surface portions arranged on a V-configuration to engage stump sockets of different diameters, and wherein the element includes straps for removably securing the element to the socket or socket containers.

12. A method of manufacturing an artificial limb comprising: (i) providing a stump socket; (ii) providing an outer limb portion; (iii) attaching an external alignment device to the outside of the socket and to the outer limb portion to form a temporary load-bearing connection between the socket and the said limb portion, the device having an adjustable joint or joints allowing rotational and translational adjustments; (iv) fitting the limb to the patient and carrying out a trial; (v) adjusting the said joint or joints to obtain a required alignment of the said limb portion relative to the socket; (vi) establishing a structural connection between the socket and the limb portion to fix the alignment of limb portion relative to the socket; and (vii) removing the external alignment device from the limb.

13. A method according to claim 12 for manufacturing an artificial limb having a thermo-plastics stump socket, wherein the step of establishing a structural connection between the socket and the limb portion comprises enclosing the space between the socket and the limb portion, introducing a liquid foaming mixture into the space, and allowing the mixture to harden thereby to form a permanent structural connection between the socket and the limb portion.

14. An alignment device constructed and arranged substantially as herein described and shown in the drawings.

15. A method of manufacturing an artificial limb substantially as herein described with reference to the drawings.