GB2136268A - An orthopaedic walking sole - Google Patents

Abstract

An orthopaedic walking sole comprises a platform which is substantially trapezoidal in plan view, which is shaped to receive a foot and which is formed on its under surface with spaced support members. The sole is formed of plastics material capable of being cut to a desired length. The platform is flat and the upper surface may be substantially planar or relieved at least in part for lightness. In order to support the instep of a foot offered to the sole, at least one arch piece is provided and has the shape of part of a segment of a sphere. The platform and arch piece are formed or provided with means enabling an arch piece to be mounted at an appropriate location on the platform. <IMAGE>

Description

SPECIFICATION An orthopaedic walking sole This invention relates to an orthopaedic walking sole for use in association with casts made of Plaster of Paris and the so-called "new casting materials".

In this Specification, the term "new casting materials" is intended to mean those orthopaedic casting materials such as those known under the Trade Names or Trade Marks "Baycast" or "Scotchcast", and which generally comprise a woven fabric impregnated with a plastics or resin material. In contradistinction to Plaster of Paris casts which may take several hours, even up to 36 hours, to set to a sufficiently hard state, the new casting materials are capable of setting to a loadbearing state in as little as 20 minutes. Furthermore these materials are very much lighter than Plaster of Paris and some are radio-apparent. For example, the new casting material sold under the Trade Name "Baycast" is a polyurethane resin system impregnated on to a woven fabric with threads measured at 0.5 mm. across and 0.25 mm. down, enclosing interstices of 1.00 mm. by 0.5 mm.The fabric usually has very little elasticity.

The resin curing period is accelerated by water, and the moisture in the air is usually sufficient to promote initial setting in a very short time. The cured bandage is thin but very strong in the same plane as the weave and strength increases rapidly as successive layers are built up.

It has long been common practice to incorporate a block or other solid device into the underside of the foot of a lower leg cast. These devices are called "walking heels" and in using them the main aims are:~ 1. To prevent the cast itself becoming worn or wet, 2. To facilitate ambulation.

Most designs of such walking heels are essentially similar, being applied to the plantar surface of the cast far enough posteriorly to be in the weightbearing line of the foot. If applied too far anteriorly the cast is likely to break through the ankle.

Walking heels may be applied after the cast is dry by adding more plaster or new casting material to hold them on. However, they are also frequently applied at the same time as the cast.

In order to deal with the considerable pressure transmitted through these heels to the base of the cast, additional layers of new casting material or Plaster of Paris in the form of splints are usually applied to the sole to provide the necessary extra support.

Despite these preventive measures, softening of the cast leading to 'push through' of the walking heel against the patient's foot is quite common.

Simple loosening of the heel from the cast is also quite frequent and necessitates either replacement or re-fixing to the sole of the cast.

In general, existing designs of heel have a quite small area in contact with the cast, consequently when a large proportion of body weight is loaded onto them, the load transmitted to the cast is considerable. Under these circumstances it is not difficult to see why problems of detachment and loosening occur.

Apart from their relatively small area, most currently available walking heels are rather high, 2 inches (50 mm.) not being unusual. Far from assisting normal gait, such a high heel positively disturbs the patient's gait. In order to counter this, many technicians, orthotists or othopaedic surgeons urge their patients to wear a raised heel on the contralateral foot so that a more or less balanced weightbearing level is achieved. The patient is now balanced but has an abnormal raised posture and may need assistance in becoming confident in walking in this position.

The reasons behind the use of such high walking heels are historical and relate to the many decades of supremacy of Plaster of Paris in the casting room. We have found that despite the revolution brought about in casting by the introduction of the new casting materials, there has so far been little effect on the design of casting accessories and cast room supplies. This is highly surprising in view of the profound differences in physical properties between Plaster of Paris and the new casting materials. It was probably valid to use up to 2 inch walking heels when elevation was the best chance of preserving the cast from wet ground (which would have rapidly caused it to distintegrate).However we have failed to find any anatomical grounds or therapeutic basis for introducing such an obvious source of instability and disturbance of gait into the management of fractured lower extremities.

Although existing designs of walking heel probably do facilitate ambulation to a degree, they do so at the expense of elevating the patient to an inappropriate degree and placing him or her in unstable equilibrium. They are not particularly successful in preserving casts and indeed often contribute problems to the maintenance of cast integrity.

There have been a number of attempts to provide an alternative to the types of walking heel described above; the most successful of these are generally referred to as 'cast shoes' or 'cast boots'.

Unlike walking heels, they are not applied as an integral part of the cast but are strapped or laced around the 'shoe' zone. Typically they consist of a thick rubber or plastic sole with canvas or similar sides. Laces or hook-and-pile closures are used to tie the device on.

Cast shoes do not normally cause 'push through' or other damage to the cast and they do confer a degree of protection against dampness to a Plaster of Paris cast. They do not elevate the patient as much as most walking heels and can thus be said to aid ambulation. Their principal disadvantage is that they cost four or more times as much as a walking heel.

Nothing has been said so far about 'rocker action' either in walking heels or cast shoes.

Protagonists of rocker action argue that by facilitating rotation of the cast the likelihood of significant rotational loading of the leg (and hence the fracture zone) within the cast, is reduced.

Detractors argue that the rocker reduces the area of contact with the ground and this, combined with the elevation of the patient create a degree of instability which may be potentially dangerous since a fall could result.

Our investigations have led to the conclusion that the rocker facility was principally of value in assisting mobility because of the considerable elevation most designs incorporate. The "climb" effect introduced into the patient's gait during weight transfer onto the affected limb elevated on a traditional walking heel makes it desirable that directional descent be governed by the pivoting possibilities of the small area at the bottom of a rocker, thus allowing the patient to choose the way down off the heel which imparts the least stress to his affected limb.

With the advent of the new casting materials there is no longer a risk of cast distintegration from dampness and for these casts at least there would seem to be little value or justification in using highly elevated walking heels, where there is a a functional alternative available.

It is an object of the present invention to provide such an alternative and substantially to meet the basic aims of walking heels or walking soles without the disadvantages of present designs.

According to the present invention there is provided an orthopaedic walking sole, wherein the sole comprises a platform which is substantially trapezoidal in plan view, which is shaped to receive a foot and which is formed on its intended under surface with spaced support members, the sole being formed of a plastics material capable of being cut to a desired length, and wherein at least one arch piece is provided having substantially the shape of part of a segment of a sphere, the platform and the or each arch piece being provided or formed with means enabling the arch piece to be mounted on the platform at a location to support the instep of a foot offered to the sole.

The platform may be flat and the upper surface substantially planar or it may be flat and the upper surface may be relieved at least in part for lightness and to provide better engagement with the base of the cast. If desired, the spaced support members may also be relieved and may be formed with an arcuate walking surface.

A preferred embodiment of the present walking sole or walking piece will have the following properties~ 1. It will elevate the affected limb only to normal shoe level so that controlateral foot compensation can be achieved with ordinary footwear. This will ensure that the patient remains in stable equilibrium and rapidly gains confidence in walking.

2. It will support the cast over a wide area and thus avoid point or small area loads. Deformation and push-through failure of the cast will thus be avoided.

3. It will be capable of comforming to the anatomy of the plantar surface of the foot as reflected in the base of the cast and be capable of being built into it. By this means loosening and breakout from the cast will be avoided.

4. It can be made adaptable to fit all patients.

5. It will be simple to use and be presented in a single form so that its adoption in the cast room does not require storage of many different sizes. A single easily tailored size would be advantageous where space is at a premium.

6. It can be made to exhibit flex characteristics similar to normal footwear.

The present orthopaedic walking sole is thus a universal walking piece which can be made to fit either foot of any patient from a small child to a large adult male. It is intended to be incorporated into the base of any cast which extends onto and around the plantar surface of the foot including a below knee walking plaster, a full leg cylindrical walking plaster or a cast brace incorporating a walking plaster. It is especially valuable for use in conjunction with new casting materials but can of course be used with excellent effect in traditional Plaster of Paris casts.

In order to enable the invention to be more readily understood, reference will now be made to the accompanying drawings, which illustrate diagrammatically and by way of example two embodiment of a walking sole, and in which:~ Figure 1 is a perspective view of a walking sole and two plantar arch pieces, Figure 2 is a perspective view of another embodiment of a walking sole, Figure 3 is an under plan view of a plantar arch piece for use with the sole shown in Figure 2, and Figure 4 is a side view of the plantar arch piece shown in Figure 3.

Referring now to Figure 1 of the drawings, there is shown an orthopaedic walking sole in the form of a flat trapezoidal platform 1. The intended underside of the sole is formed with support bars 2 extending transversely across the sole, the bars being arranged in pairs with wider spaces 3 between pairs.

In a preferred embodiment of the sole shown in the drawing, the length of the sole is about 300 mm. The greatest width is about 75 mm. and the narrowest width is about 40 mm. The flat platform 1 is about 7 mm thick and is buttressed with the support bars 2 extending across the width at intervals which alternate between about 8 mm. and 25 mm.

The narrow end 4 of the platform 1 is the 'toe' end and the ground-to-top-of-platform height rises progressively from about 12 mm. at this end to about 20 mm. at the broad or heel end 5. These heights conform with the range of elevations encountered in normal footwear and it will be seen that the gentle slope which this imparts to the foot is also quite normal.

The platform is moulded from a suitable plastics material such as urethane or polyvinyl chloride.

The shape of the platform and the plastics material from which it is made are selected such that the walking sole may easily be cut with a sharp knife such as a "Stanley" or similar knife.

The entire platform may be used for a large male foot; the front section may be cut away for use on the foot of a child; the front and back section may be trimmed off for use on the foot of a woman.

There is a wide variety of sizes which may be trimmed from the basic platform.

The larger spaces 3 on the underside of the platform between the support bars 2 allow the fabric of the new casting material or Plaster of Paris to be used for wrapping the walking sole on to the foot of the cast.

A series of circular holes 6 of regular size are moulded along the borders of the long sides of the platform extending rather less than the full length of each side.

Supplied with the platform is a pair of plantar arch pieces 7 and 8 which may or may not be joined together by a membrane. Each of the arch pieces is similar being approximately half of a segment of a sphere moulded in the same material as the platform. On the undersurface of each arch piece is a series of cylindrical pegs 9 and 10 having the same pitch as the holes 6 in the platform and being positioned the same distance from their straight border as the holes in the platform'are from the edge of it. The larger arch piece 7 is about 80 mm. across the straight border, about 10 mm. deep at the thickest part and about 40 mm. in width. The smaller piece 8 measures about 60 mm., 8 mm. and 30 mm.

respectively.

Using one or other of these two arch pieces and trimming them to shape, if necessary, it is possible to make instep supports for practically any foot.

In the use of the present orthopaedic walking sole, the platform 1 is 'offered up' to the foot before the cast is applied then trimmed as required. When used on very small feet the section not required may be retained for subsequent use.

The appropriate arch piece 7 or 8 is then selected and trimmed to the required size. The pegs 9 or 10 are engaged with the appropriate holes 6 according to the size and which foot is involved.

The walking sole is then firmly bound into the cast using 1 inch or 2 inch bandages of the cast material.

Referring now to Figures 2 to 4 of the drawings there is shown an orthopaedic walking sole the length of which is about 250 mm. The greatest width is about 75 mm. and the narrowest width is about 40 mm. The platform 21, is about 10 mm.

thick and has a relieved upper surface in the form of ridges 22 and grooves 23 which has the effect of facilitating engagement with the base of the cast and of lightening the sole. The underside is buttressed with support bars 24, extending across the width at intervals of about 25 mm. The bars are about 20 mm. thick and relieved internally for lightness as by being formed with hollows 25.

The narrow end 26 of the platform is the heel and the gruond-to-top-of-plafform height rises from about 15 mm. at the toe end 27 to about 25 mm. at the deepest point. These heights conform with the range of elevations encountered in normal footwear and the configuration of the support bar heights. The support bars 24 are framed with arcuate walking surfaces so as to impart to the foot a minimal rocker action to aid normal walking. In addition, the walking surfaces are grooved or roughened to improve the grip on the ground.

The platform is moulded from a suitable plastics material such as urethane or polyvinyl choride.

As in the other embodiment, the shape of the platform and the plastics material from which it is made are selected such that the walking sole may be easily cut with plaster cutters or a sharp knife.

The entire platform may be used for a large male foot; the front section may be cut away for use on the foot of a child; the front and back sections may be cut off for use on the foot of a woman. There is a a wide variety of sizes which may be trimmed from the basic platform and in addition the narrow heel end may be built in around the back of the heel of the cast to prevent damage when the patient is sitting with the leg extended.

The spaces 28, on the underside of the platform between the support bars 24, allow the fabric of the new casting material or Plaster of Paris to be used for wrapping the walking sole on to the foot of the cast.

A A groove 29, is moulded along each side of the top of the platform just less than the full length of each side.

Supplied with the platform is a pair of plantar arch pieces 30, of which one is shown in Figures B and C. Each of the arch pieces is similar, being approximately half a segment of a sphere, moulded in the same material as the platform. On the underside of each arch piece is a bar 31, just less in width than the grooves in the platform and being positioned the same distance from their straight border as the grooves in the platform are from the edge of it. The larger arch piece is about 80 mm. across the straight border, about 10 mm.

deep at the thickest part and about 40 mm. in width. The smaller arch piece measures about 60 mm., 8 mm., and 30 mm. respectively.

The bar 31 of an arch piece can be engaged in the groove 29 and the arch piece can be slid along the groove to an appropriate place to provide an arch support.

If desired, the underside of the platform in the spaces 28 is roughened or provided with small prongs (not shown) to provide a better grip on the Plaster of Paris or new casting material.

After use, the walking sole is.discarded with the cast when this is removed. It will be appreciated that many modications of the present walking sole may be made including the shape, arrangement and spacing of the support members, the platform dimensions, peg and hole capture, supply of arch pieces separately or together and in varying shapes and size and the use of different materials.

It is also contemplated that the present walking sole could be incorporated into a cast shoe or boot which could be strapped or laced about the foot.

Claims (10)

1. An orthopaedic walking sole, wherein the sole comprises a platform which is substantially trapezoidal in plan view, which is shaped to receive a foot and which is formed on its intended under surface with spaced support members, the sole being formed of a plastics material and capable of being cut to a desired length, and wherein at least one arch piece is provided having substantially the shape of part of a segment of a sphere, the platform and the or each arch piece being provided or formed with means enabling the arch piece to be mounted on the platform at a location to support the instep of a foot offered to the sole.

2. A sole as claimed in claim 1, wherein the platform is flat and the upper surface is substantially planar.

3. A sole as claimed in claim 1, wherein the platform is flat and relieved at least in part.

4. A sole as claimed in any one of claims 1 to 3, wherein the support members are relieved.

5. A sole as claimed in any one of claims 1 to 4, wherein the support members are formed with arcuate walking surfaces.

6. A sole as claimed in any one of claims 1 to 5, wherein the under surfaces of the support members are grooved or roughened.

7. A sole as claimed in any one of claims 1 to 6, wherein the or each arch piece is formed with pegs and the platform is formed with a series of holes along each edge to receive the pegs, whereby an arch piece may be mounted at an appropriate location to support the instep of a foot.

8. A sole as claimed in any one of claims 1 to 6, wherein the or each arch piece is formed with a bar and the platform is formed with a groove along each edge to receive the bar, whereby an arch piece may be mounted at an appropriate location to support the instep of a foot.

9. A sole as claimed in any one of claims 1 to 8, wherein the platform and the or each arch piece is moulded from a urethane plastics or polyvinyl chloride.

10. An orthopaedic walking sole substantially as hereinbefore described with reference to Figure 1 or Figure 2 to 4 of the accompanying drawings.