WO1990002543A1

WO1990002543A1 - Antithrombotic device repetitively works the calf muscle

Info

Publication number: WO1990002543A1
Application number: PCT/AU1989/000377
Authority: WO
Inventors: Brian Wellesley Holt; Alexander Mckechran Hardie Mcneil
Original assignee: Brija Pty Limited
Priority date: 1988-09-07
Filing date: 1989-09-06
Publication date: 1990-03-22
Also published as: AU4225089A

Abstract

An antithrombotic device (10) for attachment to a leg of a patient to induce repetitive compression of the calf muscle to aid deep-vein circulation, the device (10) comprising a first body member (12) adapted to support a patient's lower leg (16), a second body member (11) substantially pivotably connected (36) with the first body member (12) and adapted for engagement with the patient's foot (17), a driving connection (26) between said first (12) and second body members (11) for effecting substantially pivotal movement therebetween, power means (27) connected to the antithrombotic device for actuating the driving connection (26), and restraining means (22) to retain the patient's leg in the antithrombotic device (10), characterised in that the restraining means (22) includes engagement means (21) adapted to engage about the achilles tendon of that leg of the patient adjacent the heel.

Description

ANTITHROMBOTIC DEVICE REPETITIVELY WORKS THE CALF MUSCLE

The present invention relates to an improved antithrombotic device for attachment to a leg of a patient to induce repetitive compression or tensing of the calf muscle to aid deep vein circulation. Background Art

In the present applicants co-pending PCT patent application PCT/AU87/00317, the contents whereof are incorporated herein be reference, there is described an antithrombotic device, for attachment to a leg of a patient to induce repetitive compression of the calf muscle of the patient to aid deep-vein circulation. Such deep-vein circulation is described as being particularly desirable to prevent postoperative venous thromboembolism. The device therein described comprises a first body member, means for attaching the body member to a patient's lower leg, a second body member substantially pivotably connected with the first body member for engagement with the patient's foot, a driving connection between the first and second body members for effecting substantially pivotal movement therebetween and power means carried by the first body member for actuating the driving connection. In use the patient's lower leg is attached to the first body member and the foot to the second body member. Operation of the driving means provides reciprocating movement of the patient's foot between plantar flexion and dorsiflexion of the patient's ankle to achieve fluctuating intercompartmental pressure in the patient's leg and thereby promoting blood flow therein.

The means for retaining the patients leg within the antithrombotic device comprised a strap around the lower calf, which strap is connected to the first body member, and straps around the patient's ankle and foot which straps are both attached to the second body member. The inventor has now improved the method of connection of the patient's leg to the antithrombotic device to overcome deficiencies in the arrangement previously described. Disclosure of the Invention Thus, a first aspect of the present invention consists in an antithrombotic device for attachment to a leg of a patient to induce repetitive compression of the calf muscle to aid deep-vein circulation, the device comprising a first body member, adapted to support a patient's lower leg, a second body member substantially pivotably connected with the first body member and adapted for engagement with the patient's foot, a driving connection between said first and second body members for effecting substantially pivotal movement therebetween, power means connected to the antithrombotic device for actuating the driving connection, and restraining means to retain the patient's leg in the antithrombotic device, characterised in that the restraining means includes engagement means adapted to engage about the achilles tendon of that leg of the patient adjacent the heel.

The use of the restraining means according to this invention keeps the foot more closely associated with the second body member during its pivoting movement relative to the first body member. There is less "lost-motion" between the foot and the second body member using this restraining means and different users will be subjected to a more controlled amount of flexion than was previously the case.

The device may be operated to provide positive dorsiflexion and plantar flexion or the dorsiflexion may be positive under the influence of the power means while the plantar flexion is passive as the foot is allowed to relax back as the second body member pivots away from the foot. The engagement means may be mounted on either the first or second body member, however, it is preferred that the second body member includes a heel support portion adapted to project beneath the patient's heel and the engagement means is preferably mounted on this heel support portion. The engagement means preferably comprises a pair of resilient pads mounted to diverge from one another and to resiliently engage with the patient's ankle one on either side of the achilles tendon and abutting the heel bone. The engagement means restrains the leg against withdrawal from the antithrombotic device longitudinally of the leg.

The restraining means preferably also includes means adapted to restrain the foot against removal from the engagement means. These means preferably comprise a strap means adapted to pass around the ankle of the leg of the patient.

The strap means may be connected to either of the first or second body member but is preferably connected to the first body member. The points of connection of the ends of the strap means are preferably as far below the point of pivotal connection of the first and second body members as is possible. The strap means preferably extends around the patient's ankle. The strap means prevents the patient lifting the leg out of the device or otherwise disengaging it from the engagement means.

In preferred embodiments of the invention the pivotal connection between the first and second body members is located on an axis approximating that of the ankle of a patient using the antithrombotic device. In this arrangement and when the engagement means is positioned on a heel support portion of the second body member and the strap means passes around the patient's ankle there is very little relative motion between the device and the patient's leg thereby avoiding abrasion of the skin or the development of blisters. The present inventor has also discovered that the driving connection between the first and second body parts of the device may be considerably simplified by mounting the power means pivotably on the first body member or the second body member. The power means can then be directly coupled to a threaded driving shaft which co-operates with a threaded follower for transmitting pivotal motion to the other body member. This arrangement avoids the necessity to support the end of the threaded device shaft distal to the power means and the need to include a lost motion linkage between the threaded follower and the second body member. The power means may be pivotably mounted on the first body member through a simple yoke or, preferably, it is mounted on a resilient pad. If desired, additional straps may be included in the device. If, for instance, one wants to bring about forced plantar flexion a strap may be connected to the second body member and pass around the patient's foot. In the absence of such a strap the patient's foot will be allowed to naturally relax into plantar flexion. An additional strap may be connected to the first body member and pass lightly around the patient's calf at a distance from the ankle to assist in holding the patient's leg in place on the device. This strap cannot be drawn tightly around the calf however or it will impede the desired circulation through the calf muscle. Brief Description of the Drawings

Hereinafter given by way of example only is a preferred embodiment of the present invention described with reference to the accompanying drawings in which: - Figure 1 is a side elevational view of an antithrombotic device according to the present invention with a patient's leg in place on the device,

Figure 2 is a longitudinal sectional view through the antithrombotic device of Fig. 1 with a patient's leg in place on the device,

Figure 3 is a vertical sectional view along III-III of Fig. 1 with the patient's leg removed from the device, Figure 4 is a plan view of the antithrombotic device of Fig. 1 with the patient's leg removed from the device, and

Figure 5 is a cut-away perspective view of the first body member of the antithrombotic device of Fig. 1 showing the power means and the driving connections. Best Mode of Carrying out the Invention

The antithrombotic device 10 consists of an upper body member 11 connected to a lower body member 12 by confronting pairs of flanges 13 and 14 integral with respective ones of the body members 11 and 12, with each pair being interconnected at their distal ends by a pivot pin 15. Both portions 11 and 12 are channelled shells of thermoplastic material contoured to enclose at least part of the patient's calf 16 and foot 17. The confronting flanges 13 extend laterally from a heel support portion 18 of the upper body member 11, while confronting flanges 14 are upstanding from the lower body member 12. The position and length of the flanges 13 and 14 is such that each pivot pin 15 lies in an axis which will, in use, pass at least approximately through the centre of rotation of a users ankle.

Engagement means are provided in the heel support portion 18 of the upper body member 11 and comprises a V-shaped resilient plastics member 19 connected at its base to the heel support portion 18. A resilient foamed plastics pad 21 is provided on the inside face of the member 19 and may be covered with a suitable fabric. The pad 21 thins adjacent the base of the member 19 and thickens adjacent its free ends such that it fits snugly around the patient's achilles tendon and firmly engages both sides of the ankle portion 20 thereabove when the patient's leg is in the device. The pad 21 will abut against the patient's heel on its upper end i.e. the end further from the sole of the foot A pair of co-operating strap members 22 and 23 are pivotably connected to the lower body member 12 by pivot pins 24 (only one shown). The strap members 22 and 23 are adapted to pass around the ankle 20 of the patient. The restraining means comprising member 19 and pad 21 prevents the patient's leg being withdrawn axially of the device 10 while the straps 22 and 23 prevent the leg being lifted free from those engagement means.

It will be appreciated that movement of foot 17 is permitted .into the dorsiflexion and plantar flexion positions by pivoting of the upper body portion 11 about the pivot pins 15. Consequently, the foot 17 can be moved between these po-sitions, and this is attained by the provision of an arm 25 fixed to the heel support portion 18 of the upper body member 11 and activated by driving means 26 carried within the housing of the lower body member 12. The driving means 26 (as shown in Fig. 5) includes a reversible electric motor 27 connected through a rotatable driving shaft 28 to the arm 25. The driving shaft 28 is provided with a threaded end portion 31. An internally threaded follower 32 is threadibly engaged upon the threaded portion 31 of the shaft 28 and is held against rotation thereon by the arm 25 so as to move axially along the shaft 28 with rotation thereof. The direction of axial movement of the follower 32 will depend upon the direction of rotation of the shaft 28. The arm 25 preferably consists of a metal plate 33 displaceable along a narrow slot 34 in the lower body member 12, provided with a yoke 35 at one end which encloses the follower 32. The follower 32 is pivotably connected to the yoke 35 by pins 36. The motor 27 has at its end distal to driving shaft 28 a plate which is bonded to a resilient rubber block 38 which is in turn bonded to an upstanding arm 39 of an L-shaped support member 41. The other arm of the L-shaped support member is attached to the floor 43 of the lower body member. The resilient rubber block 38 allows the motor 27 and the driving shaft 28 to pivot in a vertical plane as the follower 32 rises and falls when the upper body member 11 pivots about the pivot pins 15. Thus, when the motor 27 is energised reciprocation of the arm 25 is effected for repeated forced dorsiflexion of the user's foot 17.

The device may be utilised in all areas of a hospital, and even for home care, as readily available electrical mains power may be used for actuation of the device. As a result deep-vein circulation can be maintained within the patient's legs to avoid development of venous thrombi. In at least some instances separate ones of the present devices will be attached to each leg of the patient. It is envisaged that mutual timing of their operations will be required for alternate, simultaneous or other related operation. Preferably, also the operation of each device will incorporate a pause at a rest position and controlled timing, speed and degree of pivoting action between the body members 11 and 12. The antithrombotic device is controlled by known electronic circuitry described in applicants copending PCT patent application PCT/AU87/00317 or by like means.

Claims

1. An antithrombotic device for attachment to a leg of a patient to induce repetitive compression of the calf muscle to aid deep-vein circulation, the device comprising a first body member adapted to support a patient's lower leg, a second body member substantially pivotably connected with the first body member and adapted for engagement with the patient's foot, a driving connection between said first and second body members for effecting substantially pivotal movement therebetween, power means connected to the antithrombotic device for actuating the driving connection, and restraining means to retain the patient's leg in the antithrombotic device, characterised in that the restraining means includes engagement means adapted to engage about the achilles tendon of that leg of the patient adjacent the heel.

2. An antithrombotic device as claimed in claim 1 in which the engagement means is mounted on the second body member.

3. An antithrombotic device as claimed in claim 2 in which the second body member includes a heel support portion adapted to project beneath the patient's heel and in which engagement means is mounted on the heel support portion.

4. An antithrombotic device as claimed in claim 1 in which the engagement means comprises a pair of resilient pads mounted to diverge from one another and adapted to resiliently engage with the patient's ankle on either side of the achilles tendon and abutting the heel bone.

5. An antithrombotic device as claimed in claim 1 in which the restraining means additionally includes means adapted to restrain the foot against removal from the engagement means.

6. An antithrombotic device as claimed in claim 5 in which the means adapted to restrain the foot comprise strap means.

7. An antithrombotic device as claimed in claim 6 in which the strap means is connected to the first body member.

8. An antithrombotic device as claimed in claim 7 in which the strap means is connected to the first body member at a point or points below the axis of pivoted connection between the first and second body members.

9. An antithrombotic device as claimed in claim 1 in which the pivoted connection between the first and second body members is located on an axis approximating that of the ankle of a patient using the antithrombotic device.

10. An antithrombotic device as claimed in claim 1 in which the restraining means additionally includes a strap connected to the second body member and adapted to pass around the patients foot.

11. An antithrombotic device as claimed in claim 1 in which the restraining means additionally includes a strap connected to the first body member and adapted to pass around the patients calf.

12. An antithrombotic device for attachment to a leg of a patient to induce repetitive compression of the calf muscle to aid deep-vein circulation, the device comprising a first body member adapted to support a patient's lower leg, a second body member substantially pivotably connected with the first body member and adapted for engagement with the patient's foot, a driving connection between said first and second body members for effecting substantially pivotal movement therebetween power means carried by the first body means or the second body means for actuating the driving connection and restraining means to restrain the patient's leg in the antithrombotic device, characterised in that the power means comprises a reversible electric motor pivotably connected to the first body member or the second body member and in that the driving connection comprises a threaded driving shaft directly coupled to the power means and a threaded follower pivotably connected to the other body member.

13. An antithrombotic device as claimed in claim 12 in which the electric motor is pivotably connected to the first body member through a resilient pad.