WO2013034870A1

WO2013034870A1 - A sole for therapeutic footwear

Info

Publication number: WO2013034870A1
Application number: PCT/GB2012/000662
Authority: WO
Inventors: Philip Henry Rees; Peter Alan REED
Original assignee: REED MEDICAL Ltd
Current assignee: REED MEDICAL Ltd
Priority date: 2011-09-05
Filing date: 2012-08-17
Publication date: 2013-03-14
Anticipated expiration: 2014-03-05
Also published as: GB201214721D0; GB201115300D0; GB2494253A

Abstract

A sole (1) is provided for an item of footwear. The sole (1) comprises toe and heel portions (2, 3) and insole and outsole surfaces (4, 5). The outsole surface (5) defines a rocker region (6) that extends transversely across the sole (1). The rocker region (6) is formed along first and second axes (8, 9) emanating from a pivot point (10) located in a position anatomically aligned to that of the second metatarsal bone (11) of a person wearing the item of footwear. Preferably, the pivot point (10) is located in a position anatomically aligned with a central shaft (12) of the second metatarsal bone of the person wearing the item of footwear and the first and second axes (8, 9) substantially follow the anatomical alignment of the mid section of metatarsal bones (13, 14) on either side of the second metatarsal (11) bone respectively. Also provided is an item of footwear incorporating such a sole (1).

Description

A SOLE FOR THERAPEUTIC FOOTWEAR

The present invention relates to a sole for therapeutic footwear and to footwear incorporating the sole that is suitable for wear, in particular but not exclusively, by diabetics.

Patients with type 2 diabetes often experience tissue stresses on the underside of the feet that lead to the breakdown of skin and the formation of plantar ulcers. Diabetic ulcers often require prolonged medical attention to achieve healing. Unfortunately, for some patients, the formation of a plantar foot ulcer is the beginning of a pathway to surgical intervention and partial or full limb amputation. Medical and allied healthcare professionals now routinely use therapeutic footwear in the management and prevention of diabetic ulcers. The function of diabetic footwear is to protect the tissues of the foot by creating an environment where damaging forces, stresses and strains are reduced and preferably minimized.

The object of the present invention is to provide a sole for an item of footwear that is suitable for use by diabetics and others with foot-related medical conditions and that fulfills the aforesaid criteria.

According to a first aspect of the present invention there is provided a sole for an item of footwear, the sole comprising toe and heel portions and insole and outsole surfaces, the outsole surface defining a rocker region that extends transversely across the sole and that is formed along first and second axes emanating from a pivot point located in a position anatomically aligned to that of a second metatarsal bone of a person wearing the item of footwear.

Preferably also, the pivot point is located in a position anatomically aligned with a central shaft of the second metatarsal bone of the person wearing the item of footwear. Preferably also, the pivot point is located at a position that is between 53% and 72% along the length of the outsole surface measured in a direction from the heel portion to the toe portion. Advantageously, the pivot point is located at a position that is 60% along the outsole surface measured in a direction from the heel portion to the toe portion.

Preferably also, the first and second axes substantially follow the anatomical alignment of the mid section of metatarsal bones on either side of the second metatarsal bone respectively.

Preferably, the first axis is orthogonal to a longitudinal axis anatomically aligned with the central shaft of the second metatarsal bone of the person wearing the item of footwear. Preferably also, the second axis is angled at between 11° and 22º inclusive to the first axis towards the heel portion of the sole. Advantageously, the second axis is angled at 19⁰ to the first axis towards the heel portion of the sole. Preferably also, the insole surface of the heel portion is rounded in both medio-lateral and anterior-posterior directions.

Preferably also, the insole surface of the toe portion has a toe spring dimension which is no more than 3mm given a last heel height of at least 25 mm.

Preferably also, the sole has a negative pitch wherein when the footwear is placed on a horizontal surface the insole surface supports a ball of the foot of the person wearing the footwear at a higher level than a heel of the foot.

Preferably also, the sole is a non-flexing sole. According to a second aspect of the present invention there is provided an item of footwear incorporating a sole according to the first aspect of the present invention. The various aspects of the present invention will now be described by way of example with reference to the accompanying drawings, in which:-

Figs. l and 2 are medial and lateral views of a sole of a left shoe in accordance with the first aspect of the present invention, an upper of a shoe incorporating the sole being shown in dash lines and a last around which the upper is formed being shown in chain dashed lines;

Fig. 3 is an underneath plan view of an outsole surface of the sole shown in Fig. ι with the position of surfaces of a foot in contact with an insole surface of the sole being shown in dotted lines;

Fig. 4 is a schematic plan view of the sole showing superimposed on an dashed outline of the sole the normal location of the bones of the left foot of a person wearing a shoe of which the sole forms a part in relation thereto ;

Fig. 5 is a medial view of a right shoe incorporating a sole in accordance with the present invention and showing in shadow a last around which an upper of the shoe is formed; and Fig. 6 is a view from the posterior of the last shown in Fig. 5

Each of the drawings shows a sole 1, an item of footwear or a last for a left shoe or a right shoe, as described above, of a pair. It will be appreciated that the other sole, item or footwear or last of the pair will be identical in all respects to that depicted but in mirror image.

The sole 1 comprises toe and heel portions 2 and 3 respectively. -In addition it comprises an insole surface 4 on which a wearer's foot rests, typically through an inlay, and an outsole surface 5 that, at least in part, contacts the ground when the wearer walks. Although the sole 1 may be made of a resilient material, such as rubber or a similar synthetic material, so as to cushion the foot when walking, the sole 1 is preferably substantially rigid so that it does not flex significantly when the wearer of an item of footwear incorporating the sole 1 walks. Instead, the sole 1 incorporates a rocker region 6 that creates an artificial pivot over which the wearer's body rotates during walking. The sole 1 is made significantly non-flexing by an appropriate choice of the manufacturing material, for example by the inclusion of textured layers or panels 7, and by making it a sufficient thickness so that flexing by foot and leg movement alone during walking is not possible.

The sole 1 is shaped so that its outsole surface 5 defines the rocker region 6. This region 6 extends transversely across the sole 1 and is formed by thickening of the sole to define two ridges aligned along first and second axes 8 and 9 respectively that emanate from a pivot point 10. The pivot point 10 is located in a position anatomically aligned to that of a second metatarsal bone 11 of a person wearing a correctly sized item of footwear, as shown in Fig. 5. The pivot point 10 is therefore located at the intersection of a hypothetical axis 12 that passes down the length of the sole 1 aligned with the second metatarsal bone 11 with the axes 8 and 9. The axis 12 may be located in any longitudinal position from a position midway between the first and second metatarsal bones 13 and 11 respectively to a position midway between the second and third metatarsal bones 11 and 14 respectively. Preferably, however, the axis 12 is aligned with the central shaft of the second metatarsal bone 11, as shown in Fig. 4.

The ball of the foot is located along the metatarso-phalangeal joints and primarily beneath the head of the first metatarsal bone 13. The pivot point 10 is located to the posterior of the ball of the foot so that the first and second axes 8 and 9 substantially follow the anatomical alignment of the mid-section of metatarsals on either side of the second metatarsal bone 11 respectively. This means that the pivot point 10 is located at a position that is between 53% and 72% along the length of the outsole surface 5 measured in a direction from the heel portion 3 to the toe portion 2, that is from the most rearward edge 15 of the heel portion to a tip 16 of the toe portion. Advantageously, the pivot point 10 is located at a position that is 60% along the length of the outsole surface 5 measured in a direction from the heel portion 3 to the toe portion 2.

With the pivot point 10 located in any of the positions as proposed above, the first axis 8 is preferably orthogonal to the axis 12 on the medial side of the sole 1 so that it aligns with the mid section of the first metatarsal 13. Likewise, the second axis 9 is preferably angled at between n° and 22° inclusive to the first axis 8 towards the heel portion 3 of the sole 1. Advantageously, the second axis 9 is angled at 19° to the first axis 8 towards the heel portion 3 of the sole 1, as also shown in Fig. 4.

In addition to the foregoing, if the sole 1 is placed on a horizontal plane, preferably the plane of the outsole surface 5 along the second axis 9 is oblique so that the thickness of the sole 1 along the axis 9 reduces evenly along its length from the pivot point 10 towards the lateral side of the sole 1. This assists in reducing the weight of the body borne by the ball of the foot during walking. As shown in Figs. 1 and 2, the thickness Ti of the sole 1 along the first axis 8 on the medial side of the sole 1 is of the order of 25 mm whereas the thickness T2 of the sole 1 along the second axis 9 reduces from 25 mm at the pivot point 10 down to around 22 mm at the lateral edge of the sole 1, as shown in Fig. 2. This reduction in thickness of the sole 1 along with the placement of the pivot point 10 to the posterior of the ball of the foot causes an oblique plane of the fore foot relative to the rear foot of a wearer of the footwear. This has the effect of moving body weight away from the inside of the ball of the foot to the outside of the foot when the heel is lifting from the ground during walking. This, in turn, reduces the stress borne by the ball of the foot and spreads the weight more evenly over the fore foot. The outsole surface 5 also includes planar relieving faces 17 and 18 at the toe and heel portions 2 and 3 respectively, as shown in Fig. 3. These are provided primarily for the comfort of the wearer of the footwear when walking and in particular when the heel is placed on the ground and the foot rolls forward during walking. Their size and configuration is not of importance to the other features of the sole 1 described herein. However, preferably the relieving face 17 extends obliquely across the toe portion from an axis 19 that is not parallel to but extends in a similar direction to the second^' axis 9 and is produced by a reduction in thickness of the sole from a thickness T3 of around 10 mm at the medial edge of the shoe to a thickness T4 of around 5 mm at the lateral edge of the shoe. The relieving face 18 extends to the posterior from an axis 20 that is substantially parallel to the first axis 8 and that is located at a distance Di which is approximately 25 mm from the posterior edge 15 of the sole 1. This relieving face 18 is produced by a reduction in thickness of the sole 1 by a thickness T5 of around 9 mm at the posterior edge 15 of sole 1.

The insole surface 4 of the sole 1 is also contoured. In the manufacture of footwear, a last is the model around which the shape of the footwear is formed and is made approximately in the shape of a human foot. However, its precise shape is tailored to the item of footwear being manufactured. It therefore conforms to the interior shape of the footwear. A last 21 for a shoe with a sole 1 in accordance with the present invention is shown in shadow in Fig. 5. Every last, for example last 21, has dimensions that correspond to a last heel height H and a last toe spring S as shown in Fig. 5. The last heel height H is a variable dimension based on the final dimension of the heel height of the finished shoe. The last toe spring S is measured from a base line assuming a nominal heel height H of the last and reflects the up-tilt of the insole surface 4 of the toe portion 2 of the sole 1. The last toe spring S is determined by the heel height H and the amount of forward roll of the foot during walking required by the shoe designer. In conventional footwear, the toe spring S compensates for a lack of sole flexibility at the ball of the foot. The toe spring S creates a rocker effect on the sole so that instead of flexing, the foot is forced to roll forward. Conventionally, therefore, the thicker or the stiffer the sole the greater the toe spring S needed because of the lack of sole flexibility. Also, the combination of up-tilted toes caused by the toe spring and a down-slanted heel and foot caused by the heel height creates an angle apex at the ball of the foot. This creates strain on the metatarsal heads and because the toes are largely immobilized by their up-tilted position, step propulsion must come almost wholly from the metatarsal heads, which further imposes stress on the metatarsal heads. In a diabetic this stress is undesirable and is considered a major contributor to the formation of diabetic ulcers.

In the present invention, as it is desired to reduce the strain on the metatarsal heads, the sole 1 is substantially rigid and the rocker region 6 of the sole is provided to create an artificial pivot over which the wearer's body rotates during walking. However, unlike conventional footwear where a rigid sole l would require an increased toe spring S, in the present invention the rocker region 6 of the sole 1 permits the last toe spring S to be reduced over most conventional last toe springs and preferably the insole surface 3 of the toe portion 2 of the sole 1 has a toe spring S which is no more than 3 mm assuming a last heel height H of at least 25 mm. This reduction in the toe spring dimension reduces the pressure experienced by a wearer of a shoe between the tips of the toes and the surface of the shoe.

In addition to the foregoing, footwear incorporating a sole 1 according to the present invention has a negative pitch. In conventional footwear, the sole of the shoe supports the heel of the wearer at a higher level than the ball of the foot. This means that the body weight of the wearer is primarily borne by the ball of the foot and the higher the heel, the greater the weight borne by the ball of the foot. However, in the present invention, as shown in Fig. 5, the insole surface 3 supports the ball of the foot at a higher level than the heel, which means that the footwear has a negative pitch. This reduces the proportion of the wearer's body weight that is supported by the ball of the foot and therefore reduces the stress and strains placed on the metatarsal heads and the metatarso-phalangeal joints along the ball of the foot.

The heel portion 3 of the insole surface 3 is also shaped. The shape of the last 21 reflects this. As shown in Fig. 6, the heel portion 22 of the last 21 below the dashed line 23 shown in Fig. 6 is rounded in both a medio-lateral and anterior-posterior dimensions. The former can be seen in the rounded medial and lateral sides 24 and 25 in Fig. 6 which is reflected in the shape of the heel portion 4 of the sole 1. The latter can be seen in the rounded portion 26 of the insole surface 3 shown in Fig. 5. In contrast, in a conventional last, the heel profile is flat in both the medio-lateral and anterior -posterior directions. The rounded nature of the heel portion 4 of the insole surface 3 follows the natural heel profile of the human foot and this reduces interface pressure between the shoe and the foot. It also provides stability and improves the biomechanical control of the heel part of the foot within the shoe during walking.

In conventional footwear, when a wearer of the footwear walks, the heel is the first part of the footwear to contact the ground. The body weight of the wearer then passes over the foot as the sole of the footwear is progressively brought into contact with the ground. The wearer's body weight moves from the outside edge of the heel, along the outside edge of the foot to the part of the plantar surface of the foot behind the head of the fifth metatarsal bone and then along the part of the sole beneath the heads of the metatarsal bones to the ball of the foot beneath the head of the first metatarsal bone. After the sole is flat on the ground a push-off phase takes place in which the heel lifts off the ground and the foot pushes against the ground to propel the body forward. In this phase, the body weight is transmitted through the ball of the foot and then the hallux. Hence, the ball of the foot beneath the head of the first metatarsal bone experiences high forces and pressures is therefore a high risk area for ulceration in diabetics In contrast in footwear incorporating a sole 1 in accordance with the present invention, the rocker region 6 of the sole 1 operates to follow the principle of high and low gear coupling as described by Bojsen-Moller in The Journal of Anatomy (1979) 129, 1 pp 165-176: "Calcaneocuboid joint and stability of the longitudinal arch of the foot at high and low gear push off". Bojsen-Moller describes how the extension of the metatarso-phalangeal joints along the ball of the foot during a push-off phase of a walking cycle, can be of a high gear or a low gear configuration. In footwear with a sole 1 in accordance with the present invention the placement of the axes 8 and 9 and the pivot point 10 and the difference between the thicknesses T1 and T2 of the sole 1 forms an oblique plane of the fore foot relative to the rear foot. The first axis 8 forms a high gear axis over which the footwear rotates as the foot rolls forward initially into the push-off phase. However, as the heel lifts from the ground the footwear rolls over to its lateral side and rotates over the second axis 9, which forms a low gear axis, as the foot pushes against the ground. This has the effect of moving body weight away from the inside of the ball of the foot to the outer lateral side when the heel is lifting from the ground and thereby reduces the strain imposed on the ball of the foot. Overall, therefore, it will be appreciated that a sole 1 for an item footwear in accordance with the present invention enables that footwear to create an environment where damaging forces, stresses and strains that would otherwise be imposed on the ball of the foot are reduced and preferably minimized. This makes the footwear suitable for use by diabetics and others with poor blood circulation in the feet.

Claims

CLAIMS 1. A sole for an item of footwear, the sole comprising toe and heel portions and insole and outsole surfaces, the outsole surface defining a rocker region that extends transversely across the sole and that is formed along first and second axes emanating from a pivot point located in a position anatomically aligned to that of a second metatarsal bone of a person wearing the item of footwear.

2. A sole as claimed in claimed in Claim 1, wherein the pivot point is located in a position anatomically aligned with a central shaft of the second metatarsal bone of the person wearing the item of footwear.

3. A sole as claimed in Claim 1 or Claim 2, wherein the pivot point is located at a position that is between 53% and 72% along the length of the outsole surface measured in a direction from the heel portion to the toe portion.

4. A sole as claimed in any of Claims 1 to 3, wherein the pivot point is located at a position that is 60% along the outsole surface measured in a direction from the heel portion to the toe portion.

5. A sole as claimed in any of Claims 2 to 4 when dependent on Claim 2, wherein the first and second axes substantially follow the anatomical alignment of the mid section of metatarsal bones on either side of the second metatarsal bone respectively.

6. A sole as claimed in any of Claims 1 to 5, wherein the first axis is orthogonal to a longitudinal axis anatomically aligned with a central shaft of the second metatarsal bone of the person wearing the item of footwear.

7. A sole as claimed in any of Claims 1 to 6, wherein the second axis is angled at between 11° and 22° inclusive to the first axis towards the heel portion of the sole.

8. A sole as claimed in any of Claims 1 to 7, wherein the second axis is angled at 19º to the first axis towards the heel portion of the sole.

9. A sole as claimed in any of Claims 1 to 8, wherein the insole surface of the heel portion is rounded in both medio-lateral and anterior- posterior directions.

10. A sole as claimed in any of Claims 1 to 9, wherein the insole surface of the toe portion has a toe spring dimension which is no more than 3mm given a last heel height of at least 25 mm.

11. A sole as claimed in any of Claims 1 to 10 that has a negative pitch wherein when the footwear is placed on a horizontal surface the insole surface supports a ball of the foot of the person wearing the footwear at a higher level than a heel of the foot.

12. A sole as claimed in any of Claims 1 to 11 that is a non-flexing sole.

13. An item of footwear incorporating a sole as claimed in any of Claims 1 to 12.

14. An item of footwear having a sole comprising toe and heel portions and insole and outsole surfaces, the outsole surface defining a rocker region that extends transversely across the sole and that is formed along first and second axes emanating from a pivot point located in a position anatomically aligned to that of a second metatarsal bone of a person wearing the item of footwear.