GB2433204A

GB2433204A - Orthosis for applying a predetermined level of compression to a limb

Info

Publication number: GB2433204A
Application number: GB0525658A
Authority: GB
Inventors: Derek Silcock
Original assignee: Ethicon Inc
Current assignee: Ethicon Inc
Priority date: 2005-12-16
Filing date: 2005-12-16
Publication date: 2007-06-20
Anticipated expiration: 2025-12-16
Also published as: GB2433204B; GB0525658D0

Abstract

An orthosis for applying compression to a limb comprises at least one flexible strap 3, 4 for applying compression when the orthosis is wrapped around a limb, and a mechanical tensioner 5 for tightening the strap to a predetermined tension. The mechanical tensioner provides a predetermined level of compression to the limb. The mechanical tensioner may comprise a drive shaft for rotating a ratchet wheel, and a torque-limited coupling between the drive shaft and ratchet wheel. The torque-limited coupling may comprise first and second clutch plates respectively connected to the drive shaft and ratchet wheel, and at least one biasing element to urge the clutch plates into engagement. The biasing elements may be adjustable to adjust the maximum torque that can be transmitted by the coupling.

Description

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1 2433204

ORTHOSIS FOR APPLYING COMPRESSION TO A LIMB

The present invention relates to an orthosis for applying compression to a limb, for example for the treatment of venous and lymphatic insufficiency.

Orthoses for wrapping around a limb are widely used to provide support, to assist in the repair of soft tissues such as healing of strained muscles, and in the treatment of venous and/or lymphatic insufficiency. Conventionally, these limb orthoses are based on elastic woven or knitted bandages that are wrapped around the limb, or tubular elasticated bandages into which the limb is inserted. However, such bandages must be applied under appropriate tension to maintain the desired level of compressive force under the bandage for the duration of treatment. It can be difficult to design or apply such bandages with the desired compressive force on the limb bearing in mind the natural variation in the size and shape of limbs.

EP-A-04758 11 describes an elastic compression bandage having markings which adopt a particular identifiable configuration when the bandage has been stretched to the desired degree. However, the application of such bandages requires a degree of skill and dexterity that may not always be available.

Furthermore, it would be desirable to apply such orthoses with a predetermined compression profile, that is to say with different pressures applied to different regions of the limb. For example, in the case of a legging orthosis for the treatment of venous insufficiency, it is preferable to apply greater compression in the lower region of the leg, i.e. near the ankle, than further up the leg. This is the opposite of what would be achieved with a simple, tubular elastic orthosis, which will apply a higher compression in the wider regions of the limb In addition, it is thought that inelastic compression provides important advantages over elastic compression for increasing venous blood flow and improving healing times for stasis ulcers.

Sanford H. Vernick et al. in Arch. Phys. Med. Rehabil. vol. 68, pages 459-461 (1987) describe a legging orthosis consisting of a number of pliable, inelastic, adjustable compression bands, from the knee to the instep. The bands are easily closed, tightened, and opened using woven nylon hook-and-loop fastening tapes. The pressure applied in each region of the limb is readily adjusted by pulling the relevant tape to the desired tightness, and then fastening with the hook-and-loop fastener. However, it is still necessary for each orthosis to be custom fitted to each patient by adjusting the length of each band to the dimensions of the limb being treated.

W097/39709 describes a development of the Vernick legging orthosis, in which the fastening bands are provided with indicia that visually indicate the relative movement of the ends of the bands, and thereby provide a visual indication of the tension applied to the band, and the resulting pressure applied by the band to the limb. The indicia make it easier for users to apply the orthosis with the desired compression profile. However, application of the orthosis still requires a degree of precision and dexterity.

Furthermore, it is still necessary to customise the orthosis to the dimensions of the limb being treated.

Accordingly, a need remains for a limb compression orthosis, in particular a leg orthosis, that is easy to apply even by unskilled personnel, and that can provide a desired inelastic compression profile on a limb independently of the individual limb dimensions.

The present invention provides an orthosis for applying compression to a limb, comprising at least one flexible strap, and a mechanical tensioner attached to the strap and adapted for tightening the strap to a predetermined tension when the orthosis is wrapped around a limb.

The orthosis is suitably a legging compression orthosis, for example a legging orthosis for compression treatment of the lower leg.

The strap may he a continuous hand, fbr example of width about 5mm to about 5cm, for wrapping around the limb. In these embodiments, the orthosis suitably comprises a plurality of such bands for applying pressure around the limb at a plurality oflocations along the limb. An advantage of this configuration is that different pressures can be applied by different bands in order to achieve a desired compression profile along the limb. Suitably, in these embodiments, the bands are closely spaced along the limb in order to provide a substantially continuous compression profile along the limb. For example, a gap between edges of adjoining bands may be of width less than about 5cm, for example less than about 2cm, and in certain embodiments less than about 1cm.

Suitably, the continuous bands are attached to, threaded through, or interlaced with, a limb covering sheet for wrapping around the limb underneath the straps. The sheet helps to distribute the forces applied by the straps smoothly across the surface of the limb.

The sheet also functions as a covering for the limb, which is especially appropriate if there is an open wound or ulcer on the limb. The sheet also maintains the bands in the desired substantially parallel relationship at the desired spacing. Suitably, the straps are substantially inelastic, and suitably the continuous sheet is also substantially inelastic.

In alternative embodiments, the orthosis comprises a sheet for wrapping around the limb having a plurality of fastening straps extending from one longitudinal edge of the sheet and attached thereto, for securing to complementary straps and/or fasteners on the opposite edge of the sheet. In other words, in these embodiments the primary tensile component around the limb is the sheet. The straps do not extend as a continuous band around the limb. Instead, the straps are provided along a longitudinal edge of the sheet for tensioning the sheet.

The orthosis according to the present invention further comprises a mechanical tensioner attached for applying a predetermined tension to at least one strap when the orthosis is wrapped around the limb. The term "mechanical tensioner" refers to a mechanism that receives the strap and applies a predetermined tension thereto when mechanically actuated by e.g. a lever, a key or a motor. The predetermined tension translates to a predetermined compressive force applied to the limb by the strap. The orthoses according to the present invention thus differ from the legging orthosis of Vernick ci a!.

and the legging orthosis of W097/39709, both of which rely on tightening a band to a predetermined length in order to achieve a desired compression of the limb. In contrast, the orthosis according to the present invention uses a mechanical tensioner which applies a predetermined force (tension) regardless of the size of the limb. Therefore, the orthosis according to the present invention can be applied to limbs of any size without custom fitting to the individual patient. Furthermore, the desired compressive force can be applied by a unskilled operator without training, simply by actuating the mechanical tensioner.

Preferably, each of the straps as hereinbefore described on the orthosis is tensioned by the mechanical tensioner. For example, a mechanical tensioner may he associated with each strap. In other embodiments, a single mechanical tensioner may be moved from strap to strap. In these latter embodiments, each strap is tightened to the desired tension by the mechanical tensioner, and is then fastened at that tension before moving the tensioner to the next strap. In any case, the straps preferably further comprise one or more fastener elements for securing the straps at the predetermined tension after tightening of the mechanical tensioner. This helps to prevent the straps from slipping back through the mechanical tensioner over time. The fastener elements may, for example, comprise hook-and-loop cloth, or a buckle fastener.

It will be appreciated that the fastening bands and straps in the above-described embodiments can be released from the mechanical tensioner to allow removal and re-application of the orthosis to the limb.

Preferably, at least one of the mechanical tensioners on the orthosis, and more preferably all of the mechanical tensioners, is adjustable to vary the predetermined tension. In this way, any desired compression profile along the orthosis can be achieved reproducibly, and again without specifically customising the orthosis to the dimensions of a given patient's limb.

The mechanical tensioner may he any mechanism adapted to receive a strap, and to apply a predetermined maximum tension to the strap upon actuation of the mechanism by a user. Typically, the mechanism will comprise a handle or a key socket that can be actuated or rotated by the user (using a suitable key where appropriate) to apply tension incrementally to the strap until the limiting tension is reached.

In certain embodiments the mechanical tensioner comprises a ratchet wheel having an outer surface, for example a toothed surface. The strap in these embodiments comprises a complementary surface for engaging the ratchet wheel surface, whereby rotation of the ratchet wheel in the permitted direction tightens the compression band. In these embodiments, the mechanical tensioner further comprises a drive shai for rotating the ratchet wheel, and a torque-limiting coupling between the drive shaft and the ratchet wheel. The torque-limiting coupling permits a torque applied to the ratchet wheel to be increased until a limiting value of the torque is reached, after which the torque-limiting coupling locks or slips to prevent any increase in the torque applied to the ratchet wheel.

The tension applied to the strap by the ratchet wheel at this limiting torque is the said predetermined tension.

In these and other embodiments, the mechanical tensioner comprises a suitable housing, and the housing has an aperture for receiving an end of the strap passing through the housing.

In the above embodiments comprising a ratchet wheel, the strap passes through a pinch between the ratchet wheel and a fixed surface or roller within the housing, against which the strap is gripped by the ratchet wheel. The engagement between the ratchet wheel and the strap may be solely frictional, but preferably there are projections (e.g. teeth) or apertures in the band for engagement with complementary projections (e.g. teeth) or recesses on the ratchet wheel to provide traction between the ratchet wheel and the band, and to resist slipping of the band back through the housing to release the tension on the band.

The ratchet wheel is rotated by means of a suitable torque-limiting coupling. For example, the tensioner may comprise a drive shaft which may be mounted substantially coaxially with the ratchet wheel. The drive shaft can he rotated by a handle or key from outside the housing by the operator. A torque-limiting coupling is provided between the drive shaft and the ratchet wheel. For example, the torque-limiting coupling may comprise a first clutch plate connected to the drive shaft and a second clutch plate coniiected to the ratchet wheel, such that the drive shaft rotates the ratchet wheel when the clutch plates are in engagemeit. The engagement may be purely frictional between the clutch plates, or suitably there may he projections such as hemispherical projections or rollers on one of the clutch plates that engage complementary hemispherical recesses in the other clutch plate. The clutch plates are biased into engagement by a suitable biasing element, such as a spring on the drive shaft and/or the ratchet wheel axle. The biasing element may be adjustable to vary the maximum torque that may be transmitted by the clutch. When the maximum torque is exceeded, the first and second clutch plates slip past each other instead of transmitting further torque to the ratchet wheel.

An embodiment of the present invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a plan view of a legging orthosis according to the present invention before application to a limb; Figure 2 shows the legging orthosis of Figure 1 applied to a lower leg; Figure 3 shows a plan view of a legging orthosis according to a second embodiment of the invention, before application to a limb; Figure 4 shows a schematic top plan view of the mechanical tensioner mechanism in the embodiments of Figs. 1-3, with the clutch plates engaged; Figure 4A shows a partial schematic view of the mechanical tensioner of Figure 4, with the clutch plates out of engagement; and Figure 5 shows a sectional view through the tensioner of Figure 4.

Referring to Figure 1, the orthosis comprises a flexible sheet 1 for wrapping around the leg. The sheet I is formed of a substantially continuous, substantially inelastic woven textile material, for example a nylon textile. The sheet I is dimensioned to wrap around a lower leg. Six straps 2 are attached along a longitudinal edge of the sheet 1 equally spaced. The straps 2 are formed from substantially inelastic textile material, for example they are nylon straps. They are attached to the longitudinal edge of the sheet 1 by stitching. Each strap 2 ends in a tongue 4. In this specification, the term "longitudinal" refers to an edge of the sheet that extends along the axis of the limb in use.

Six further straps 3 are attached to the opposite longitudinal edge of the sheet 1 by stitching. The sIraps 3 are of a similar dimensions and material to the straps 2. The distal ends of the straps 3 are fixedly attached to respective tensioner mechanisms 5.

Each tensioner mechanism 5 is provided with a socket 7 for inserting a key to actuate the tensioner mechanism. A strip 6 of hook-and-loop fabric is stitched to the front face of the strap 3. A complementary strip 8 of hook-and-loop attachment fabric is stitched to the reverse side of the opposite straps 2.

Referring to Figure 2, the orthosis of Figure 1 is shown fitted to lower leg 9. The sheet 1 is wrapped around the leg 9, and straps 2 pass through respective tensioner mechanisms 5, in which the straps are tensioned to a predetermined tension, and straps 2 are then attached to straps 3 by engagement of the respective hook-and-loop fastener strips 6, 8.

This prevents the straps 2 from backing off through the tensioner during extended wear of the orthosis.

Figure 3 shows an alternative embodiment. The orthosis according to Figure 3 comprises a backing sheet 10 of inelastic textile material similar to that described in relation to Figure 1. In this embodiment, straps in the form of six continuous bands 11 for wrapping around the limb are threaded through eyelets 16, 17 in sheet 10. A first end 11 of the straps terminate in a tongue 12, and is provided with a strip 18 of hook-and-loop fastener material stitched to the reverse side thereof. A second end 13 of the straps is fixedly attached at a distal end to a tensioner mechanism 14, and has a strip 15 of hook-and-loop fastener material stitched thereto.

Referring to Figure 4, a single tensioner mechanism 5 is shown in top plan view. The tensioner 5 comprises a housing 20 substantially enclosing the mechanism (in this view the front face of the housing has been removed to show the mechanism inside). The mechanism comprises a ratchet wheel 22 in the form of a cylinder having longitudinal teeth 23 for engaging complementary teeth on the strap 42. The ratchet wheel 22 is mounted on axle 24 that rotates in bearings 26, 27 that arc fixedly attached to the housing. Some axial movement of the axle 24 in the bearings 26,27 is permitted. A first end of the axle 24 terminates in a clutch plate 34. A second end of the axle 24 ends in bias plate 36.

The ratchet wheel 22 is driven by drive shaft 29 through a second clutch plate 32 that engages clutch plate 34. Small hemispherical projections in clutch plate 32 are received in corresponding hemispherical recesses in clutch plate 34 to provide the necessary engagement. Drive shaft 29 rotates in a bearing 28 fixed to the wall of housing 20. The distal end of the drive shaft 29 is provided with key socket 7, whereby the drive shaft 29 can be rotated by inserting hexagonal key 30 into socket 7 and turning. It will be appreciated that any other suitable means could be used to rotate the drive shaft 29.

The clutch plates 32, 34 are pressed together by pressure of leaf spring 38 against biasing plate 36 on the drive shaft 24. The leaf spring 38 is in turn pressed against the biasing plate 36 by pressure screw 40, whereby rotation of the pressure screw 40 allows the biasing pressure applied to the clutch plates 32, 34 to be adjusted. The clutch plates are held in engagement by said biasing pressure as shown in Fig. 4 until the torque applied across the clutch plates 32,34 reaches a limiting value at which the clutch plates start to slip past each other as shown in Fig. 4A. This limiting value of the torque thereby limits the maximum tension applied to the strap. The magnitude of the limiting torque value (and hence of the maximum tension applied to the strap) is adjusted by rotation of the pressure screw 40 to increase or decrease the biasing pressure between the clutch plates 32,34.

Referring to Figure 5, this schematic cross-sectional view shows the ratchet wheel 22 having teeth 23 around the circumference thereof for engaging complementary teeth 44 on the strap 42. A ratchet pawl 46 engages the teeth 23 to resist reverse rotation of the ratchet wheel 22. The pawl 46 is provided with a spring or similar biasing element (not shown) to bias the pawl against the ratchet wheel 22. The tensioner further comprises a release mechanism (not shown) which can be actuated by the user to release the pawl 46 from the ratchet wheel 22 thereby enabling the strap 42 to be pulled out of the tensioner for removal of the orthosis from the patient.

The above embodiment has been described by way of example only. Many other embodiments falling within the scope of the accompanying claims will be apparent to a skilled reader.

Claims

CLAIMS

1. An orthosis for applying compression to a limb, said orthosis comprising at least one flexible strap for applying said compression when the orthosis is wrapped around a limb, and a mechanical tensioner for tightening the said strap to a predetermined tension.

2. An orthosis according to claim 1, wherein the orthosis is a legging orthosis.

3. An orthosis according to claim 1 or 2, wherein said strap is a continuous band for wrapping around the limb, and the orthosis comprises a plurality of such bands spaced longitudinally along the orthosis for applying compression around the limb at a plurality of locations along the limb.

4. An orthosis according to claim 1 or 2, comprising a sheet for wrapping around the limb having a plurality of said straps extending from one longitudinal edge of the sheet and attached thereto, for securing to complementary straps and/or fasteners on the opposite edge of the sheet.

5. An orthosis according to claim 3 or 4, wherein each said strap is associated with a mechanical tensioner configured to apply a predetermined tension to the flexible band when it is wrapped around the limb to produce a compression profile along the limb.

6. An orthosis according to any preceding claim, wherein at least one said mechanical tensioner is adjustable to vary said predetermined tension.

7. An orthosis according to any preceding claim, wherein: the mechanical tensioner comprises a ratchet wheel having an outer surface; the flexible band comprises a complementary surfiice for engaging the said ratchet wheel surface, whereby rotation of the ratchet wheel in the permitted direction tightens the compression band; and the mechanical tensioner further comprises a drive shaft for rotating the ratchet wheel and a torque-limiting coupling between the drive shaft and the ratchet wheel.

8. An orthosis according to claim 7, wherein the torque-limiting coupling comprises: a first clutch plate connected to the drive shaft; a second clutch plate connected to the ratchet wheel for engagement with the first clutch plate, and one or more biasing elements to urge the clutch plates into engagement.

9. An orthosis according to claim 8, wherein the biasing elements are adjustable to adjust the maximum torque that can be transmitted by said coupling.

10. An orthosis according to any preceding claim, wherein at least one said strap further comprises a one or more fastener elements for securing the strap at the predetermined tension after tightening of the mechanical tensioner.