Title: Orthotic Insole

Description of Invention

The invention relates to an orthotic insole and in particular to one which includes one or more insert by which its action can be readily modified.

There are many forms of orthotic insoles in the prior art, some are custom made for individuals and tend to be very expensive, whilst others are bought "off the shelf and tend to be less expensive but potentially less effective at correcting the users' problems. It is also known in the prior art for orthotic insoles to include removable inserts which allow for "off the shelf products to be adjusted for a user's needs, and readjusted as their condition alters over time, or indeed the activities they perform alter. One example of such an orthotic insole with inserts is described in US5, 138,774. An alternative approach, where an arch support is removably adhered to the underside of an insole to allow for adjustment, is described in US6, 598,319 B2. Another alternative approach is described in WO98/524435.

It is an object of the present invention to provide an alternative form of orthotic insole.

According to the present invention there is provided an orthotic insole comprising a main body having an opening in either the lateral and/or medial sides for receipt of an insert, the opening(s) extending from a forward position which in use is located beneath and close to the relevant metatarsal head to a rearward position which in use is located beneath the calcaneus wherein the main body comprises: a) a base portion extending in use from the back of the calcaneus to just behind the metatarsal heads which is formed of semi-rigid plastics material capable of deforming under loading and then returning to its original shape, and

b) a top portion which extends the full length of the foot which is formed of deformable material, and wherein the opening(s) are located between the base and top portions

The opening may be on the lateral side of the main body and may extend from a forward position which in use is located beneath the head of the fifth metatarsal or behind (posterior) the head of the fifth metatarsal to a rearward position which is located beneath the calcaneus.

The opening may be on the medial side of the main body and may extend from a forward position which in use is located beneath the head of the first metatarsal or behind (posterior) the head of the first metatarsal to a rearward position which is located beneath the calcaneus.

The orthotic insole may further include an upper surface layer on the top portion.

The orthotic insole further includes a plurality of inserts of different sizes and materials for receipt in the opening(s).

The base portion may be manufactured from a material having a flexural strength in the range of 50 to 150 MN/m ² .

The base portion may be manufactured from a material having a tensile strength in the range of 50 to 80 MN/m ² .

An embodiment of an orthotic insole according to the present invention will now be described, by way of example only, with reference to the accompanying figures in which:

Figure 1 illustrates an orthotic insole for a left foot according to the present invention from beneath;

Figure 2 illustrates an orthotic insole of Figure 1 from the lateral side, and

Figure 3 illustrates an orthotic insole of Figures 1 and 2 from the medial side.

Referring to the Figures, an orthotic insole 10 comprises a base portion 12, a top portion 14, a lateral opening 16 and a medial opening 18. The insole 10 of the Figures is for a left foot. As will be well understood an insole 10 for a right foot will be a mirror image of that illustrated.

The base portion 12 extends in use from the back of the calcaneus to just behind the metatarsal heads, and thus is what is known in the field as a three- quarter length component. The base portion 12 is intended to emulate the normal loading and unloading properties of the foot, which is achieved by a combination of the design and the material from which it is manufactured.

The material from which the base portion 12 is manufactured must have properties which include good flexural strength and elastic deformation such that it can flex repeatedly without breaking and such that it returns to its original shape rapidly once unloaded during use. It may also be that the act of returning to its original shape is energy returning in use. Clearly it is important that the material operates consistently, without degradation or loss of its mechanical properties, over the multiple loading cycles that the insole will undergo during its operational life. Suitable materials are semi-rigid plastics such as homo polypropylene, co-polymer polypropylene, ABS (Acrylonitrile

Butadiene Styrene) and other materials with similar properties. It is advantageous for the base portion 12 to be manufactured from a material having a flexural strength in the range of 50 to 150 MN/m ² and/or a tensile strength in the range of 50 to 80 MN/m ² . It has been found that insoles with

these material properties do not easily collapse when loaded by a foot of a user.

The base portion 12 is designed to have a profile similar to that of the foot, with 3 prime arches: the medial longitudinal arch, the lateral longitudinal arch and the transverse arch, but where each of the arches will be significantly lower than the arches normally found in the foot such that the insole should not in general come into contact with the sole of the user's foot within the arches.

In addition the base portion 12 may incorporate a plantar fascia groove - that is a shallow depression or groove that runs along the approximate path of the medial slip of the plantar aponeurosis, in an attempt to facilitate normal foot mechanics.

The top portion 14 extends the full length of the foot (but embodiments of insoles according to the invention may be constructed in which this component is also three-quarters rather than full length). The top portion 14 is formed from a softer material than the base portion, which is deformable and elastic, such as, for examples, EVA (Ethyl Vinyl Acetate), PU (Polyurethane) and

Polyethylene foam, such that it provides a comfortable interface for the foot of the user and stretches to accommodate different inserts being positioned within the lateral and/or medial openings 16, 18, as discussed below.

Embodiments of insoles 10 according to the invention may be manufactured specifically for use by those with particular conditions, such as diabetes, rheumatoid disease, or for particular uses, such as sport or particular sports, and so and this top layer 14 may be chosen as best suited to the application of the embodiment concerned.

An upper surface layer (not shown) may also be added to the insole 10 if desired, to provide a particular aesthetic effect, or for any other purpose. The base and top portions 12, 14 are anatomically shaped as is well known in the

prior art to provide a surface which is contoured generally as the under surface of a foot.

The base and top portions, 12, 14 will typically be injection moulded. The base and top portions 12 and 14 may be secured together by any appropriate means with regard to the materials from which they are made, such as sonic welding or by use of an adhesive. In addition, depending on the different materials used, it may be possible to mould one of the base and top portions

12, 14, and then to mould the second of the portions 12, 14 directly onto the first one manufactured. A preferred combination is for the base portion 12 to be manufactured from ABS and for the top portion 14 to be manufactured from

PU, although other combinations could be used.

The lateral opening 16 extends from a forward position which in use is located either beneath the fifth metatarsal or 10 mm to a rearward position which is located beneath the calcaneus. The medial opening 18 extends from a forward position which in use is located either beneath or 10mm behind the head of the first metatarsal to a rearward position which is located beneath the calcaneus.

A range of inserts of varying sizes and materials, shaped to fit into the lateral opening 16 or the medial opening 18, is provided. The inserts are anatomically designed to provide correction to abnormal function of the user's foot, and may be provided with different densities. The particular inserts to be inserted into the opening(s) may be selected by the user to provide the required mechanical properties of the insole 10 in use. Preferably this is done following consultation with a suitably qualified practitioner, such as a podiatrist who may also perform scans of the foot or feet and analysis of the users gait in order to advise the user.

Because the openings 16 and 18 and the appropriate inserts extend backwards to the calcaneus they control and improve any abnormal function of the rear foot as well as of the lateral and/or medial arches.

The insole according to the present invention is beneficial because it permits a user to individually control the amount of deformation experienced by the insole as a whole unit, by selecting desired inserts for the lateral opening 16 and medial opening 18. For example, where a patient's foot experiences large amounts of movements or 'collapsing of the arches of the foot', potentially leading to pathology, then the ability to adjust the insole to reduce this movement is extremely beneficial. The inserts being made of variably deformable materials and geometry, will, as desired, either resist or allow movement, depending on the individual forces generated by the foot. The prior art does not allow the surface geometry of the insole to be modified in this way, instead relying on the addition of inserts to the under side of the insole. Due to the massive variability in foot shape and function, it would be extremely difficult for any of the existing insoles to be capable of matching this individuality of a user's feet. The insole according to the present invention, however, will not only allow the previously mentioned mechanical adjustability, but it will also permit modification of the contours of the surface of the insole which is directly in contact with the foot.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any

combination of such features, be utilised for realising the invention in diverse forms thereof.