WO2009094712A1

WO2009094712A1 - An orthotic suitable for use in treating plantar fasciitis

Info

Publication number: WO2009094712A1
Application number: PCT/AU2009/000099
Authority: WO
Inventors: Greg Ernest Sanderson
Original assignee: Greg Ernest Sanderson
Priority date: 2008-01-29
Filing date: 2009-01-29
Publication date: 2009-08-06

Abstract

An orthotic for a shoe being a substantially foot shaped sheet of fibreglass and/or carbon fibre reinforced epoxy polymer with high fiexural strength in order to resist flexing as the wearer runs or walks. The orthotics are fiat or curved upwardly at the toe. Those for heavy wearers are made of sheet metal. A Fiexural Strength range of 1-82 GPa is disclosed but the preferred range is 38-44 GPa.

Description

AN ORTHOTIC SUITABLE FOR USE IN TREATING PLANTAR FASCIITIS

FIELD OF THE INVENTION

This invention concerns an orthotic worn in a shoe for the relief of plantar fasciitis.

BACKGROUND OF THE INVENTION

The plantar fascia (or plantar aponeurosis) is a dense band of connective tissue which extends over the sole of the foot deep in the skin. Figure 1 of the drawings is a plan view of a superficial dissection of the sole of the foot showing the plantar fascia 2.

The plantar fascia originates from the medial tubercle of the calcaneus bone. From there the plantar fascia fans out, covering intrinsic muscles of the foot, blending with the soft tissues of the metacarpophalangeal (MCP) joint complex and continuing on as five slips which anchor into the phalangeal bases.

Figure 2 of the drawings is a medial side view of the bones of the foot and the plantar fascia when standing. As shown, the bones of the foot form a bony arch with the plantar fascia stretched like a bow string between the two ends of the arch. The bony arch is relatively flatter in weight bearing than non- weight bearing positions due to body weight placing soft tissues beneath the arch, including the plantar fascia, under increased strain and causing stretching thereof. Placing of the foot in a non- weight bearing position, such as occurs when lying down, reduces the stretch and strain on the planar fascia and relatively heightens the arch in the foot.

In weight bearing, shortening of the plantar fascia may occur by actively flexing (curling up) the toes, or actively supinating to heighten the arch of the foot. Lengthening of the plantar fascia in weight bearing may occur by actively dorsiflexing the toes, or actively pronating to flatten the arch of the foot. Figure 2 illustrates the plantar fascia lengthened in weight bearing due to dorsiflexion of the toes whilst the ankle is plantar fixed.

Thus in individuals having a naturally high arch in weight bearing due to a rigid cavus foot, the plantar fascia tends to become shortened and thickened. This is as opposed to individuals with a planus foot type having a naturally flat arch in weight bearing which tends to result in stretching and lengthening of the plantar fascia. Individuals having either a naturally high arch or flat arch in weight bearing may be predisposed to an overuse inflammatory type condition known as 'plantar fasciitis'.

In this condition the overstressed plantar fascia becomes painful about its attachment to the medial tubercle of the calcaneus. The medial tubercle may be tender to touch, and the tenderness may extend distally along the medial portion of the plantar fascia. Plantar fasciitis may occur due to a sudden relative increase in strain and stretch on the plantar fascia such as may occur in individuals who change from non- weight bearing desk job to a weight bearing stand-up job.

hi athletes, plantar fasciitis commonly results from activities such as running or dancing that require dorsiflexion of the metacarpophalangeal joints during plantar flexion of the ankle (see Figure 2) which stretches the plantar fascia whilst under significant strain. Various treatments have been suggested for plantar fasciitis including:

Passive sustained stretching of the calf muscles to reduce tightness. Tightness may reduce an individual's ability to supinate, thereby increasing strain on the plantar fascia.

Passive sustained stretching of the plantar fascia.

Taping appropriate parts of the foot.

US 6,343,426 discusses the shortcomings of footwear for older men and how these spoil balance in physical activity. A removable sock containing a foot shaped plate of EVA polymer containing carbon fibres is described. The purpose of this is to reduce the resilience of the shoe sole in order to restore stability during running. My work has shown that while the use of such carbon fibre plates relieve some conditions they produce scant relief for others. The body's reaction to shoe modifications is complex and incompletely understood. The introduction of stiffer soles which allow less change in shape during foot movement are in the prior art rejected as too uncomfortable.

SUMMARY OF THE INVENTION

A first product aspect of the invention provides an orthotic for placing in a shoe between the sole of a user's foot and the shoe, being a foot shaped metal plate of sufficient thickness to prevent flexing as the user walks or runs.

In this specification reference to the term "prevent flexing" does not refer to a complete - A - prevention of flexing as slight movements of the foot will invariably occur. Rather, "prevent flexing" is a reference that flexing of the foot will be prevented to an extent which significantly reduces stress on the plantar fascia.

In a particular aspect, flexing of the foot comprises dorsiflexion (extension) at the MCP joints.

The plate may be made of a rigid material so as to prevent flexing of the user's foot. Despite this, slight flexing of the plate may still occur when sufficient weight bearing forces are applied. The plate may then elastically recoil after slight flexing. Thus during slight flexing, the plate may absorb some energy ordinarily absorbed by the plantar fascia, thereby reducing stress on the plantar fascia. The slight flexing of the plate may occur in the region beneath the MCP joints.

The plate may extend substantially along the length of the user's foot. The area of the plate preferably equals or somewhat exceeds the area of the users foot.

The plate may be substantially flat. However, it may be concave in relation to the foot in respect of the longitudinal axis. Alternatively, the plate may have a predetermined contour. The plate may be contoured to some extent to a user's foot or shoe. In particular it may be a gentle s-shape so that a user's toe is slightly elevated with respect to the heel when standing. The contoured plate should still be able to prevent flexing to an extent which significantly reduces stress on the plantar fascia. The contoured version may be more appropriate for user's who have trouble tolerating the flat version or find it uncomfortable.

The purpose of the plate is to resist flexion of the foot as the user walks or runs. The flexible construction of a shoe allows the sole to assume an S -configuration but this may be limited when the plate is worn inside the shoe.

The choice of metal is influenced by its density and malleability. In practice the loads borne by the plates vary depending on the weight of the user which may range from a young schoolgirl to a fat mature male. A thickness of 3mm may suffice and aluminium may be a suitable metal because of its lightness and the tendency to passivate thereby resisting corrosion. 3mm aluminium may be particularly suitable for light weight users or users having a more sedentary lifestyle. Plates for heavier persons may be manufactured from a 4mm bearing plate, namely the next commercial plate thickness. Steel may also be an alternative but powder coating or galvanising adds to the cost of manufacture. Titanium may also be suitable, particularly when the plate is to be used by a heavy athlete.

Commercially available sheets reinforced with carbon fibre may be another alternative. More energy absorption and elastic recoil may be available if carbon fibre is used. The carbon fibre version may be more appropriate for user's who have trouble tolerating the metal version or find it uncomfortable. This carbon fibre version may comprise a sheet of transparent epoxy polymer with roving carbon fibre. For some users it may be preferable to start with the carbon fibre version and progress to a metal version once tolerance to the orthotic has developed.

The plate may improve athletic performance. It may allow the user to run faster or jump further or higher. This may be due to the elastic recoil of the plate. Thus the carbon fibre version may be particularly suitable for improving athletic performance.

A variety of synthetic plastics, composites and metal sheet make orthotics of suitable stiffness. Overall the range of Flexural Modulus is 1-82 GPa₃ the preferred range being those made of fibre reinforced epoxy polymer sheets with a Flexural Modulus of 38, 39, 40, 41, 42, 43, 44 GPa. Those polymers and alloys with a Flexural Modulus of 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82 are at the stiffer end of the range and include 2mm and 3mm sheets of aluminium, titanium, stainless steel and magnesium alloy.

The less rigid materials such as polyethylene terephthalate (1 GPa), polyamide reinforced with carbon fibre (12 GPa) lie at the opposite end of the range and flex more. This part of the range, namely 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 GPa is less satisfactory but is more useful than the comparatively flexible prior art range. A second product aspect of the invention is a shoe incorporating an orthotic plate as described above into the construction.

In this version of the invention the plate is not visible being covered by an insole joined to the upper of the shoe or the lining thereof.

A third product aspect of the invention provides an orthotic for placing in a shoe between the sole of a user's foot and the shoe, being a rigid metal plate adapted to prevent flexing of the foot as the user walks or runs.

The plate may extend between the heel and the ball of the user's foot. It may not extend past the ball of the foot beneath the toes, or a portion of the orthotic beneath the toes may be cut out. Either of these arrangements may allow for some more movement of the toes whilst still preventing flexion of the foot to an extent which significantly reduces stress on the plantar fascia.

The plate may generally outline the sole of the foot with the toe end being shortened to proximate the ball of the foot. Alternatively, the orthotic may generally outline the sole of the foot with a portion cut out. The cut out portion may be beneath the toes.

The orthotic may be designed to be of a similar shape to, and to underlie, the plantar fascia.

The plate may be narrower than the sole of the foot. It may have projecting tabs adapted to project towards the edges of the shoe. These may help to align the plate in the shoe or limit movement of the plate once inserted into the shoe.

The plate may be made of metal. It may be made of high grade aluminium which is suitable for aircrafts and able to resist the forces applied thereto when the user runs. Alternatively or additionally, titanium may be used. Stainless steel or carbon fibre may also be used. Carbon fibre may be particularly suitable where slightly more bending of the plate is desired. This may be desired for user's who have some difficulty tolerating the more rigid metal plates, or for user's seeking to improve their athletic performance. The plate may be a removable insert. Instead of, or as well as, being removable the plate may be suitable for permanent affixing to the sole of the shoe.

The plate may have one or more straps adapted to pass over the user's foot in order to tightly secure the foot to the plate. This may help to further limit movement of the foot. The plate may be flat. It may be of substantially even thickness.

In a fourth product aspect, the invention provides an orthotic suitable for use in the treatment of plantar fasciitis, the orthotic comprising a plate for placing in the user ' s shoe between the sole of the user's foot and the shoe, the plate being adapted to limit dorsiflexion of the metacarpophalangeal joints of the user's foot.

In a fifth product aspect, the invention provides an orthotic comprising a plate for placing in a shoe between the sole of the user's foot and the shoe, the plate being adapted to limit movement of the user's foot. Limiting foot movement may in turn cause increased movement in the user's ankle. Therefore the plate may be suitable for increasing ankle mobility or stretching muscles which act about the ankle. In particular, the plate may be used to increase ankle dorsiflexion or stretch the ankle plantar flexor muscles. Increasing ankle dorsiflexion may be desired if dorsiflexion is reduced such as commonly occurs after injury of the lateral ligaments of the ankle.

In a sixth product aspect, the invention provides an orthotic comprising a plate for placing in a shoe between the sole of a user ' s foot and the shoe, the plate being adapted to allow the athlete to run faster or jump further or higher. The plate may elastically recoil after flexing of the plate. The elastic recoil may assist the athlete to run faster or jump further or higher.

In the prior art orthotics, rubbers and elastomers which distributed the pressure of the foot were of low flexural strength and had a Shore A2-40 hardness. Comfort was an important requirement. The aim of this invention is the removal of foot pain by contact with a foot support of high flexural strength. Comfort is a lesser consideration and harness in the Brinell 1-100 range is likely. BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention is now described with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic medial view of bones of a foot and plantar fascia in a standing position on a flat surface.

Figure 2 is a diagrammatic medial view of a foot as in Figure 1 in the tiptoe position showing the plantar fascia already stretched.

Figure 3 is a diagrammatic underneath plan of a foot showing the plantar fascia.-

Figure 4 is a plan of a plate.

Figure 5 is a perspective of the first plate.

Figure 6 is a side view of the first plate.

Figure 7 is a diagrammatic section through a running shoe with the first plate in position.

Figure 8 is a plan view of a second plate.

Figure 9 is a plan view of a third plate.

Figure 10 is a plan view of a fourth plate.

Figure 11 is a side view of a fibreglass mould.

Figure 12 is a diagrammatic side view of a shoe incorporating the orthotic. DETAILED DESCRIPTION WITH RESPECT TO THE DRAWINGS

In Figures 1 and 3 the plantar fascia 2 is shown extending between the heel 4 and toes 6 in a relaxed state. Figure 2 shows the plantar fascia 2 in an extended state. Walking and running on lumpy ground when the person has been accustomed to smooth paths or tracks can bring on fasciitis. So too can incorrect use of leg exercise machines in a gym. Persons suffering plantar fasciitis complain of pain and walking is reduced to hobbling.

Figures 4, 5 and 6 show a 3mm thick aluminium plate 8 the same size as the persons foot. The plate is laser cut from commercially available plate of the same thickness.

The plates are supplied as a pair. These are inserted into the persons shoes, in this example a running shoe 10.

The obverse face 12 contacts the persons sole and heel. The reverse face 14 bears on the sole and heel of the shoe.

Immediate relief from pain is experienced. The person transfers them to subsequent pairs of shoes, for example work boots so that the foot continues to stand on the plate.

Figure 8 shows a second embodiment of a plate 16. The second plate 16 is of even thickness and surrounds the outline of the user's foot 18 with the toe end being cut away at the balls of the feet. Such an arrangement allows for some additional toe mobility when compared with the first embodiment of the plate 8, whilst still supporting the area of the foot which is transversed by the plantar fascia. This may be desirable for athletes requiring some additional toe mobility.

The heel to ball of foot arrangement also requires less aluminium to be used than the first plate, thereby reducing production costs.

Figure 9 shows a third embodiment of a plate 26 made of rigid titanium. The third plate is narrower than the user's foot 18 and is designed to outline the shape of the user's plantar fascia with an enlarged heel portion which aids placement and stability in the shoe. Projecting tabs 28 extend from the sides of the plate 26 to the sides of the shoe, facilitating placement and stability therein.

Referring to Figure 10, there is shown a fourth embodiment of a plate 20. The fourth plate 20 surrounds the outline of the user's foot, having a cut-out toe portion 22 and a cutout heel portion 24. This arrangement allows the plate to fit in the shoe without having excess room to move around at the sides or ends whilst still supporting the area of the foot 18 transversed by the plantar fascia. Furthermore the cut-out portions may allow for some improved mobility of the toes which may be desirable for some athletes.

By preventing flexing of the foot, and in particular by limiting MCP joint extension and stretching of the fascia, the plate encourages increased movement (particularly dorsiflexion) at the talocrural (ankle) joint to compensate. Therefore the plate may also be used to stretch and lengthen the achilles tendon and plantar flexors of the ankle and increase mobility in the ankle joint. It may in particular improve ankle dorsiflexion, a movement which is often reduced after ankle injuries.

The applicant considers that the effectiveness of using the plate in the treatment of plantar fasciitis may be due to reasons including:

The plate significantly limits dorsiflexion at the MCP joints, thereby reducing stretch and stress on the plantar fascia during activities in which such movement ordinarily occurs (eg. walking, running, dancing).

Despite being made of a rigid material, the plate may still be forced to flex slightly beneath the MCP joints during weight bearing activities such as walking, running or dancing. Thus some energy which would ordinarily be absorbed by the plantar fascia is absorbed by the plate before it elastically recoils to its original shape.

A pair of cavity moulds, one for each foot is made from fibreglass and resin (see Figure 11). Each mould is 3.5mm deep at the heel end tapering to 1 mm thickness at the toe end, the intermediate thicknesses being as shown in Figure 6. The mould has a margin surrounding the cavity. The surface of the mould is prepared by wiping with a wax based release agent in known manner. A batch of epoxy resin is prepared. A GP ISO wax free POLYPLEX™ resin made by Fiber Glass International, Springvale, Victoria, Australia. Six sheets of reinforcement are cut from the following materials:

198g Plain weave Carbon fibre 30Og Plain weave Fibreglass 58Og Carbon Double Bias 580g Fibreglass Double Bias 580g Carbon Double Bias 300g Plain weave Fibreglass

The first plain weave carbon fibre sheet is laid in the mould and brushed with epoxy resin in known manner followed by the plain weave fibreglass sheet. This too is brushed with resin and rolled with a fibreglass consolidator after each sheet is wetted and the orthotic is built up in known manner until all the sheets are used. Three of the sheets are foreshortened in order to achieve the taper in thickness. The resin requires 24 hours to cure. After two hours the edges are trimmed off. The average weight is 13Og. The weight change is 8g per size.

Orthotics prepared by the above method were subj ected to a three-point load test, namely ASTM D790. Test results appear below.

Support Span: 27.5mm Specimen Width: 12.7mm Crosshead Speed: 7.35mm/min

In Figure 12 a black rubber sole 32 supports a rubber heel wedge 34 to which orthotic 36 is attached. A mid sole 38 cushions the foot somewhat cushions the foot and upper 40 completes the construction but usually there will be no mid sole and the orthotic will be sheathed only in a fabric envelope.

I have found the advantages of the above embodiment to be:

1. The orthotic brings immediate, lasting relief to the user.

2. The orthotic is easily transferable from shoe to shoe.

3. The orthotic is adaptable to be incorporated into the shoe structure.

It is to be understood that the word "comprising" as used throughout the specification is to be interpreted in its inclusive form, ie. use of the word "comprising" does not exclude the addition of other elements.

It is to be understood that various modifications of and/or additions to the invention can be made without departing from the basic nature of the invention. These modifications and/or additions are therefore considered to fall within the scope of the invention.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. An orthotic for placing in a shoe between the sole of the user's foot and the shoe, being substantially foot shaped and of sufficient stiffness to prevent flexing (as herein defined), as the user walks or runs, having a Flexural Modulus of 1-82 GPa.

2. An orthotic as claimed in Claim 1, wherein the orthotic is a plate substantially equal to the area of the user's foot.

3. An orthotic as claimed in Claim 1 or 2, wherein the plate is flat.

4. An orthotic as claimed in Claim 1 or 2, wherein the plate is of sinusoidal profile so that the toe end is slightly elevated in relation to the heel end.

5. An orthotic as claimed in any one of Claims 1 -4, wherein the plate is made of a material with a hardness of 1-100 Brinell.

6. An orthotic as claimed in Claim 5, wherein the plate is made of metal 2-4mm thick.

7. An orthotic as claimed in Claim 6, wherein the metal is mild steel, stainless steel, magnesium alloy, titanium, aluminium.

8. An orthotic as claimed in any one of Claims 1 -4, wherein the plate is made of an epoxy polymer reinforced with alternate sheets of carbon fibres and glass fibres.

9. ^■ An orthotic as claimed in any one of Claims 1 -8, wherein the plate extends from the heel to the ball of the foot.

10. An orthotic as claimed in any one of Claims 1 -8, wherein the plate extends from the heel to the toes but does not underlie the toes.

11. An orthotic as claimed in any one of Claims 1-8, wherein the plate is co-extensive in area with the plantar fascia of the user's foot.

12. An orthotic as claimed in any one of Claims 1-8, wherein the plate is narrower than the user's foot but has at least one peripheral pair of projections from the side of the plate which positions the plate in the shoes.

13. An orthotic as claimed in any one of Claims 1-12, wherein the range is 35-82 GPa.

14. An orthotic as claimed in any one of Claims 1-12, wherein the range is 38-44 GPa.

15. An orthotic as claimed in any one of Claims 1-12, wherein the range is 1 -34 Gpa.

16. An orthotic as claimed in Claim 4 or 8, wherein the plate thickness diminishes from 3-3.5mm at the heel to 1-1.2mm at the toe.

17. An orthotic for placing in a shoe between the sole of the user' s foot and the shoe being foot shaped and capable of exerting elastic recoil upon loading by the user's weight.

18. An orthotic for placing in a shoe between the sole of the user's foot and the shoe being a substantially foot-shaped plate of sufficient stiffness to limit foot movement and promote ankle movement.

19. An orthotic substantially as herein described and illustrated in Figures 5-7 or as modified by Figures 8, 9 or 10.

20. A shoe containing as part of the sole construction an orthotic as claimed in any one of Claims 1-19.