GB2458282A

GB2458282A - An orthotic device

Info

Publication number: GB2458282A
Application number: GB0804502A
Authority: GB
Inventors: Barney Gardner
Original assignee: FOOT RITE Ltd
Current assignee: FOOT RITE Ltd
Priority date: 2008-03-12
Filing date: 2008-03-12
Publication date: 2009-09-16
Also published as: GB0804502D0

Abstract

An orthotic device comprising a heel support portion 22 arranged to support a heel of the foot and an arch support 24 portion arranged to support the arch of the foot. The heel support portion 24 comprises a base with a raised rim 28 extending at least partially round its rear and sides to locate and support the heel. The base 26 having a calcaneus support portion formed in it and a surrounding portion surrounding the calcaneus support portion, the calcaneus support portion being softer than the surrounding portion. The calceneus support may have at least one cavity to make it softer than the surrounding portion. An adjustment wedge may be fitted against the heal support 22 to adjust the amount of inversion provided by the orthotic.

Description

ORTHOTIC DEVICES

Background to the Invention

An orthotic is a pre-formed insole (foot bed) that is designed to fit into footwear to treat and control abnormal foot function during normal walking. There are two types of orthotic: accommodative and functional.

An accommodative orthotic is used for cushioning and re-distribution of high plantar pressure where an existing deformity prevents the foot from functioning correctly.

In many instances these devices are used to accommodate a deformity where there is little chance of restoring full foot function. Often rigid bony changes prevent an orthotic controlling foot function.

A functional orthotic is designed to improve foot function where a mild deformity exists, and where adequate range of motion is available to place the foot in a more functionally advantageous position during normal walking. Functional orthotics can be custom made or pre-formed (depending on level of control required).

Summary of the Invention

The present invention provides an orthotic device comprising a heel support portion arranged to support a heel of the foot and an arch support portion arranged to support the arch of the foot, wherein the heel support portion comprises a base with a raised rim extending at least partially round its rear and sides to locate and support the heel, the base having a calcaneus support portion formed in it and a surrounding portion surrounding the calcaneus support portion, the calcaneus support portion being softer than the surrounding portion.

The calcaneus support portion may have at least one cavity formed in it to make it softer than the surrounding portion. The at least one cavity may comprise at least one recess formed in the underside of the base.

Alternatively the cavity may be partially or completely enclosed within the calcaneus support portion.

The at least one cavity may comprise an array of recesses formed in the underside of the base.

The orthotic may further comprise an adjustment wedge arranged to fit against the heel support portion to adjust the amount of inversion provided by the orthotic. The orthotic may further comprise locating means arranged to locate the adjustment wedge relative to the heel support portion. The locating means may comprise a projection, on one of the heel support portion and the adjustment wedge, arranged to cooperate with at least one recess on the other of the heel support portion and the adjustment wedge. The at least one recess providing the calcaneus support portion may also form the at least one recess of the locating means.

Alternatively the locating means for locating the adjustment wedge may be completely separate from the calcaneus support portion.

Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings.

Brief description of the Drawings

Figure 1 is a diagram of the phases of gait; Figure 2 is a diagram of the bones of the foot; Figure 3 is a further diagram of components of the foot; Figure 4 is a top view of an orthotic device according to an embodiment of the invention; Figure 5 is a bottom view of the orthotic of Figure 4; Figure 6 is a perspective view of the orthotic of Figure 4; Figure 7 is a bottom view of an orthotic according to a further embodiment of the invention; Figure 8 is a top view of an adjustment wedge for use with the orthotic of Figure 7;

Description of the Preferred Embodiments

The orthotic design according to one embodiment of the invention is a pre-formed orthotic for the treatment of functional foot disorders. To understand the orthotic device and its applications, there now follows a brief description of the main bones of the foot, and of how the foot should function during normal walking.

Referring to Figure 1, the main bone in the heel of the foot is the calcaneus 10. The talus 12 sits on top of the calcaneus 10, and is connected to the tibia 11 and fibula 13. The navicular 14 and cuniforms are located in front of the talus 12 and the cuboid 16 is located in front of the calcaneus 10. The five metatarsals 17 are the main bones in the midfoot or arch area of the foot, and the phalanges 18 make up the toes in the forefoot.

Referring to Figures 1 to 3, the gait cycle is a description of the various stages of what is considered normal ambulation within the medical community. There are three distinct stages in the gait cycle: heel strike, mid-stance and toe off.

Heel strike This is considered to be the first part of the gait cycle. The calcaneus (heel bone) 10 strikes the ground at its lateral (outside) aspect. Once heel strike has taken place the talus 12, which is a bone that sits on top of the calcaneus 10, and to which the tibia 11 and fibula 13 are connected, begins to pronate the rear of the foot. Pronation is comprised of rotational movement in three planes of motion, abduction which is motion in the transverse plain, i.e. about a vertical axis, eversion which is motion in the frontal plane, i.e. about a horizontal front/rear axis, and dorsiflexion which is motion in the sagittal plane, i.e. about the horizontal transverse axis. Pronation plays a major part in controlling the overall movement of the feet. Its effect is to roll the foot inwards. Once heel strike has taken place the foot then moves to the next stage the gait cycle.

Mid-stance In this part of the gait cycle the foot is flat on the ground and is pronated to its full extent of movement with the body's centre of gravity lying directly over the foot.

It is here the foot goes from being very loose to rigid to enable supination of the foot. Supination like pronation is also movement in three planes of motion and has the effect of rolling the foot outwards. Following this movement the bones of the foot lock onto the rear-foot creating rigidity.

The foot then resembles a lever that allows the foot to progress to the final stage of the gait cycle.

Toe-off This is the final part of the gait cycle where the foot is fully supinated and the foot locked onto the rear-foot to form a rigid lever. Much of the body weight progresses through the first ray (bones of the great toe), which plantar-flexes (moves downwards) enabling the foot to move forwards. The plantar fascia ligament 19, which is located on the bottom of the foot and is attached to the heel bone 10 and toes 14 of the foot, enhance the forward motion of the foot, greatly improving the efficiency of the gait cycle. There are many soft tissue structures that also enhance foot movements throughout the gait cycle.

Once toe-off has taken place the foot swings forward to re-commence heel strike and the cycle begins again.

Orthotic Design Referring to Figures 4 to 6, an orthotic according to one embodiment of the invention comprise a moulded body 20 of elastomeric material. The orthotic is arranged to extend under the hindfoot and midfoot, but not under the forefoot. The orthotic therefore comprises a heel support portion or heel cup 22 at its rear end and an arch support portion 24 at its front end.

The heel cup 22 comprises a base 26 with a raised rim 28 around its rear end and sides, which is arranged to extend up round the back and sides of the heel to locate the heel in the correct position on the orthotic, and to provide lateral support for the heel. The underside 30 of the base is flat and the base is thicker on the medial side than on the lateral side providing approximately 50 of lateral inversion.

In the centre of the heel cup 22 a calcaneus support region is provided which is arranged to be softer than the surrounding parts of the heel cup 22. This soft spot is arranged to cushion the calcaneus, to further reduce excessive stress on the calcaneus and surrounding soft tissue. The soft spot is produced by forming a group of recesses 32 in the underside of the heel cup 22. In this case an array 34 of small circular recesses 32 is formed in the underside of the heel cup 22 extending upwards into the heel cup.

The arch support portion 24 is flat on the underside of its lateral edge, which is coplanar with the underside of the heel support portion 22. The medial side of the arch support portion is arched on the underside. As can best be seen in Figure 6, the upper surface of the arch supporting portion 24 is convexly curved upwards by an amount which is greatest on the interior side and decreases down to substantially zero curvature on the lateral side where the top surface is substantially parallel to the under surface. On the interior side, the curve of the upper surface extends further back than the arch on the underside, so that there is a thickened portion between the calcaneus support portion and the arched portion of the under surface. The height of this area of the orthotic, which is arranged to be proximal to the navicular, is therefore stiffened to maintain the plantar fascia ligament at its correct height and to prevent over stress caused by excessive pronation.

The orthotic is arranged to be approximately three quarters of the length of the foot, bringing the front end of the device close to the end of each metatarsal 17. The device is this length as it is concerned with controlling the larger bones of the rear foot and mid-foot along the sagittal plane of the foot. The entire orthotic is laterally inverted from the ground (or flat surface) by 5°; this inversion helps to slow down the calcaneus on heel strike and controls excessive pronation.

The lateral (outer side) aspect of the heel cup is externally curved to achieve a better fit inside footwear, and is slightly denser (approx 2mm) than the medial (inner side) aspect of the heel cup. Specifically the rim 28 is thicker on the lateral side than on the medial side. In particular the base of the rim 28 is thicker on the lateral side than on the medial side.

Since the top edge of the rim is of substantially constant thickness all around the rim, this means that the tapering of the rim from its base to its top is greater on the lateral side than on the medial side. This increased thickness cushions and absorbs shock directly at heel strike and thereafter.

The elasticity of the TPE material also enhances the action of the plantar ligament 19 to aid toe-off during the gait cycle.

The orthotic of this embodiment is designed to control abnormal foot function primarily due to excessive pronation of the sub-talar joint, which is the joint between the talus bone 12 and the calcaneus bone 10.

It is desirable to use an orthotic to control the talus bone/joint, but as it is inaccessible due to soft tissue and other bones, this is not possible.

Therefore the orthotic of this embodiment is arranged to improve foot function by supporting, controlling, and providing shock absorption for, the calcaneus on heel strike and reducing excessive forces taking place as the bones of the foot as they move through the gait cycle.

The effects of excessive pronation, which the orthotic of this embodiment is arranged to avoid, can be to cause the tibia and fibula to internally rotate which moves the knee into a valgus position and internally rotates the hips. These actions can increase stress on the bones, joints and soft tissue structures leading to poor mechanical locomotion and in turn injury.

The use of the orthotic device of this embodiment is to create an ideal platform for locomotion, from heel strike to toe off improving the function of the foot and lower limb and to treat and prevent further injury.

The material used for this embodiment of the orthotic is a thermoplastic elastomer (TPE) often used in the plastics industry. The selection of this material is based on a number of criteria. The principle considerations are: toughness, shock absorption, fatigue resistance, flexibility, low density, wear resistance, hydrolysis resistance, exceptional load bearing properties, suitable for prolonged contact with the skin, non-toxic.

With the research for the material conducted and trials completed the most suitable substance was considered to be a co-esther based thermoplastic elastomer (TPE). Due to the properties of the TPE material, the device is not rigid, but designed to flex with the movement of the foot, helping to reduce any risk of inversion injury following heel strike.

Other suitable materials can be used as alternatives Referring to Figures 8 and 9, in a second embodiment of the invention an orthotic comprises a main body 120 which is similar to that of the first embodiment. However, in this case, the calcaneus support portion is formed by a shallow square recess 134 in the underside of the heel cup, with an array of circular recesses 132 formed in the top surface of the square recess 134. The orthotic also comprises an adjustment wedge 140 in the form of a medial varus wedge which is arranged to fit under the heel support portion of the main body 120. The adjustment wedge 140 has curved sides and rear and a straight front edge, and is arranged to cover the whole of the underside of the heel support portion. The medial side of the wedge 140 is thicker than the lateral side, with the wedge providing an angle of about 4°. A locating formation 142 is formed on the top surface of the adjustment wedge which is arranged to fit into the square recess 134 on the underside of the heel cup so as to locate the wedge relative to the heel cup. The locating formation 142 is arranged to be an interference fit into the square recess 134, so as to attach the adjustment wedge 140 releasably to the heel support portion of the main orthotic body 120.

Should more additional pronatary calcaneal control, than is provided by the main orthotic body 120, be required, the 4° medial varus wedge can be clipped into place by pushing the locating formation 142 into the square recess 134. Because the smaller circular recesses 132 are not filled by the locating formation, the soft spot still functions with the wedge in place. This device can be used to control the foot medially, where excessive pronation takes place.

Claims

CLAIMS1. An orthotic device comprising a heel support portion arranged to support a heel of the foot and an arch support portion arranged to support the arch of the foot, wherein the heel support portion comprises a base with a raised rim extending at least partially round its rear and sides to locate and support the heel, the base having a calcaneus support portion formed in it and a surrounding portion surrounding the calcaneus support portion, the calcaneus support portion being softer than the surrounding portion.
2. An orthotic according to claim 1 wherein the calcaneus support portion has at least one cavity formed in it to make it softer than the surrounding portion.
3. An orthotic according to claim 2 wherein the at least one cavity comprises at least one recess formed in the underside of the base.
4. An orthotic according to claim 3 wherein the at least one cavity comprise an array of recesses formed in the underside of the base.
5. An orthotic according to any foregoing claim further comprising an adjustment wedge arranged to fit against the heel support portion to adjust the amount of inversion provided by the orthotic.
6. An orthotic according to claim 5 further comprising locating means arranged to locate the adjustment wedge relative to the heel support portion.
7. An orthotic according to claim 6 wherein the locating means comprises a projection on one of the heel support portion and the adjustment wedge arranged to cooperate with at least one recess on the other of the heel support portion and the adjustment wedge.
8. An orthotic according to claim 7 when dependent on claim 3 or claim 4 wherein the at least one recess providing the calcaneus support portion also forms the at least one recess of the locating means.
9. An orthotic substantially as hereinbefore described with reference to any one or more of the accompanying drawings.