Device for use with a leg prosthesis

Abstract

A device 2 for use with a leg prosthesis comprises a foot member including at least a first portion 4 and a second portion 6, wherein the first portion is substantially planar, and the second portion

Description

The invention to which this application relates is to a device for use with a leg prosthesis and in particular, although not necessarily exclusively, a sole or insole member to be located within a shoe in which a lower-leg or above-the-knee prosthesis is to be located. The use of prosthetic devices, herein after referred to as prostheses, to aid or replicate the function of parts of the body of a user are well known and can be provided in various forms for specific uses. Prostheses may range in form from cochlear implants or pacemakers to artificial limbs such as prosthetic arms or legs. Prosthetic legs mimic the function, and sometimes the appearance, of a real limb. They may be used by people that have undergone an amputation, or are affected by a congenital limb difference that can make walking difficult. Typically, prosthesis include a load bearing frame structure to mimic the leg of the user and a terminal portion to mimic the foot of the user and allow them to stand and balance on a support surface. Leg prostheses are often available in a variety of designs at varying levels of complexity and associated costs and / or availability. Simple, readily available and relatively inexpensive prostheses only include the load bearing frame, or skeleton, and the foot portion. It has been found that these prostheses, which are often rigid and offer no movement about the knee and / or ankle joints, are inhibitive to the movement of the user. The foot portions are provided with a flat surface to ensure that the user is stable when standing on a support surface. However, when a user begins to walk, the foot must be lifted and placed rather than rolled off, as would be the case with a real foot. This results in a swinging action of the user’s leg in order to walk. The swinging action is an irregular motion for the gait of the person, and can result in over-compensation of the user’s other leg which can result in further musculoskeletal health complications. Furthermore, the irregular gait of the user may visually indicate the presence of a prosthesis, which may be something that the user of the prosthesis may not wish to disclose. The swinging motion is often exaggerated for a user of an above-the-knee prosthesis. It is known to provide prostheses with articulated components, such as moveable knee and / or ankle joints. These moveable joints may more accurately mimic the movement of a real leg and / or foot, but are more complex and therefore more expensive and less readily available than a rigid prosthesis. Furthermore, foot portions of these articulated prostheses are still provided with flat surfaces to stand and balance on, and an exaggerated gait must be performed for the user to walk. Prostheses designed for movement, such as those including a resilient member such as a curved blade, are unsuitable for daily usage as they do not offer adequate support to a user when they are standing on the same. Furthermore, these prostheses must be interchanged by the user when they are selecting which prosthesis to wear. A known alternative is to provide interchangeability of the foot portion of the prosthesis to suit the requirements of the user, to be more suited for either walking or standing. However, this requires planning by the user for what activities they are about to undertake, which may not always be possible. The mechanisms by which the foot portion is interchanged is also complex, as the foot portion must be connected to the leg portion in a manner that ensures adequate stability to the user in use. It is an aim of the present invention to overcome the aforementioned known issues of leg prostheses, and lower-leg and above-the-knee protheses in particular, and to provide a means by which a user may adapt their existing prosthesis for ease of walking in a relatively simple and inexpensive manner. In a first aspect of the invention, there is provided a device for use with a leg prosthesis, the device including a foot member including at least a first portion and a second portion, wherein the first portion is substantially planar and the second portion is inclined with respect to the plane of the first portion. In a preferred embodiment the device is configured to function as a sole or insole member to be used with and / or as part of a leg prothesis. Further preferably the device is configured to form the sole and / or insole portion to be used with and / or form part of a lower-leg and / or above-the-knee prothesis. As such at least part of the device is configured to mimic the sole or the foot and in particular the ball of the foot so that the user’s gait is improved. Typically the second portion is formed or located at and angle to the first portion. In one embodiment, the first portion is configured to he substantially parallel with a surface on which a user of the device is standing in use. In one embodiment, the second portion is inclined to be directed upwards and away from the surface on which a user of the device is standing in use. In one embodiment, the incline of the second portion with respect to the first portion is such that applying force to the second portion causes the second portion to he parallel with the surface on which a user is standing. Typically, in this embodiment, when the second portion is lying parallel with the surface the first portion is inclined to be directed upwards and away from the surface. In one embodiment, the second portion is substantially planar or planar. In one embodiment, the angle of incline of the second portion from the first portion is between 10 and 30 degrees. Preferably, the angle of incline is between 10 and 15 degrees. Further preferably the angle of incline is 14 degrees. In one embodiment, an interface is formed between the first portion and second portion. In one embodiment, the interface between the first portion and second portion is curved, such that the device may partially roll when force is applied to the second portion. In one embodiment, the second portion takes the form of the toes of a real foot, and the first portion takes the form of the flat of a real foot. In one embodiment, the length of the second portion is equivalent to a third of the length of the device. Thus, in accordance with the invention, a user of the device may locate the foot portion of their prosthesis on the device in use. When standing, the weight of the user acts through the first portion, which is parallel or flat with the surface on which the user is standing, and the device is stable. When the user begins to walk forward, weight is shifted so as to act through the second portion of the device, which causes the device to partially roll to be parallel or flat with the surface, which in turn raises the first portion upwards and away from the surface. It is submitted that in this way, the second portion allows the foot to move similar to how the toes of a real foot bend upwards with respect to the rest of the foot as a person walks forwards. In one embodiment, the device includes a third portion, separate from the second portion, that is inclined with respect to the first portion. In one embodiment, the third portion is planar. In one embodiment, the angle of incline of the third portion from the first portion is between 3.5 and 10 degrees. Preferably, the angle of incline is 3.5 degrees. In one embodiment, the third portion takes the form of the heel of a real foot. In one embodiment, the length of the third portion equivalent to a third of the length of the device. In this embodiment, when a user locates their foot on the surface after taking a step, they may initially make contact with the surface when their foot is at an upward angle, rather than being parallel to the surface, before then rolling their foot to be flat with the ground. It is submitted that this provides for a natural stride of a user using the device with a prosthesis. In one embodiment the device is a unitary member. In one embodiment at least the first and second portions are formed of a sheet material of uniform thickness. Typically, the first, second and third portions are formed of a sheet material of uniform thickness. In one embodiment, the device is formed of a material and / or has suitable thickness such that there is substantially no deflection of the device caused by the weight of the user during the use of the device. In this way, the device does not bend in use, so as to provide a stable platform on which the user may locate their weight in use. In an alternative embodiment, the device is formed of a material and / or has suitable thickness that the device may flex under the weight of the user by a predetermined amount. Typically, the predetermined amount by which the device may flex is selected to mimic the Achilles tendon of the user, that is to aid in the propulsion of the user when they take a step on the device. Preferably the predetermined amount by which the device may flex is selected in relation to the estimated weight of the user, typically associated with the foot size of the user. In one embodiment, the device is formed of a material with a high strength-to-weight ratio so as to not significantly impede the step of the user in use. In one embodiment, the device is formed of a carbon fibre material. In one embodiment, the device is configured to be located within a shoe of the user, such that the device is located intermediate the prosthesis and a sole of the shoe in use. In an alternative embodiment, the device is configured to be located with a prosthesis. In this embodiment, the device includes locating means such that the device is releasably located with the prosthesis. In one embodiment, the device includes a surface with a high friction means to reduce sliding of the device with a surface with which the same is contacted. Typically the high friction means includes indentations and / or brushing. In one embodiment, the device has a profile that is approximate to the profile of the sole of a real foot. In a further aspect of the invention, there is provided a device for use with a leg prosthesis, the device including a first, second and third planar portions, wherein the second portion and third portion are inclined with respect to the first portion so as to angle away from a surface with which the first portion is flat against. In one embodiment the device has a profile of a sole of a foot. In one embodiment, the first portion is equivalent to the flat of a foot, the second portion is equivalent to the toes of a foot, and the third portion is equivalent to the heel of a foot. In one embodiment the second portion is inclined from the first portion at an angle of 14 degrees. In one embodiment the third portion is angled from the first portion at an angle of 3.5 degrees. In one embodiment, the length of the device is evenly divided by the first, second, and third portions. In a yet further aspect of the invention, there is provided a device to be located within a shoe, the device including a at least a first portion and a second portion, the first portion substantially planar and the second portion inclined with respect to the first portion. In one embodiment the device is formed of a sheet material that is rigid enough so as not to substantially deflect in use but may flex in use. Specific embodiments of the invention are now described with reference to the accompanying drawings wherein: Figure 1 illustrates a side schematic view of a device in accordance with an embodiment of the invention; Figures 2a-c illustrate the various positions of a device during use with a prosthesis in accordance with one embodiment of the invention; Figures 3a-c illustrate plan, beneath, and side views of a device in accordance with one embodiment of the invention; Figures 4a-c illustrate plan, beneath and side views of a device in accordance with another embodiment of the invention; and Figures 5a-c illustrate perspective, rear, and side views of a device in accordance with a yet further embodiment of the invention. Referring firstly to Figure 1, there is illustrated a device 2 for use with a lower-leg prosthesis. It will be appreciated that the device may further be suitable for an above -the-knee prosthesis or similar lower-body prosthesis. The device 2 is formed of a unitary member that is subdivided into three portions: a first portion 4, a second portion 6, and a third portion 8. The portions 4,6,8 are substantially planar. The second portion 6 is inclined from the first portion 4 at an angle A, and the third portion 8 is inclined from the first portion at an angle B. The incline of the second and third portions 6,8 with respect to the first portion 4 is such that the second and third portions are inclined upward and away from a support surface on which the first portion 4 is flat with in use. The lengths of the first, second and third portions 4,6,8 are evenly proportioned as a 1:1:1 ratio along the length of the device 2. In alternative embodiments, the lengths of the portions 4,6,8 may be different from one another. The second portion 6 and first portion 4 are joined by an interface 12, and the third portion 8 and first portion are joined by an interface 14. The unitary member 2 from which the device is formed is a single piece of sheet material that is bent at the interfaces 12,14 by the required amount to form the inclined portions 6,8. In alternate embodiments, the interface may be weld lines between separate components to form the unitary member 2. The device 2 is suitably rigid so as not to deflect under the force of a user’s weight or by the walking or running motion of the user. Referring to Figures 2a-c, there is illustrated the device 2 of Figure 1 in use with a prosthesis 20. The prosthesis includes an artificial foot portion 22 and an artificial leg portion 24. The foot portion 22 is fixed with respect to the leg portion 24, and cannot move as a real ankle joint would. The prosthesis 20 is typically located within a shoe (not illustrated) to be worn by a user. The shoe acts to protect the foot portion 22 of the prosthesis and conceals the prosthesis, which the user may not wish to disclose that they are wearing. The shoe provides no significant aid to the walking motion of the user. The foot portion 22 includes a flat sole 26. In typical use, without an device 2, when a user is standing still, the force of their bodyweight travels through the flat sole to the ground or support surface 100 on which they are standing. The flat surface area of the sole of the foot portion 22 of the prosthesis ensures that the user is stable when standing still, as there is no rolling of the foot, and the leg portion 24 through which the body weight of the user acts is substantially perpendicular to the ground 100. However, when the user moves to take a step forwards, the entire flat surface of the sole of the foot portion 22 must be lifted from the ground 100 for the step to be taken. This in an unnatural motion, as when a step is taken with a real foot, the heel of the foot is first lifted off the ground, followed by the flat of the foot, and finally the toes of the foot. Similarly when a person is placing their real foot after a step, the initial contact is with the heel of the foot, followed by the flat of the foot, followed by the toe of the foot. When using a prosthesis with a flat sole, the entire foot must make contact with the ground at one time. It is often the case that the leg portion of a prosthesis must be perpendicular with the ground when the foot is lifted and placed on the ground due to the flat surface of the foot portion, resulting in an unnatural gait of the wearer of the prosthesis. In accordance with the invention, the device 2 is provided intermediate the sole 26 of the foot portion 22 of the prosthesis and the ground or support surface 100. It is typically the case that the device 2 is located within a shoe in which the foot portion 22 is then placed, so as to be in the form of a sole or insole of the shoe. In alternate embodiments, the device may be located with the foot portion 22 by the provision of locating means such as straps or the like. In the illustrated embodiment, the sole 26 of the foot portion 22 contacts the inclined second portion 6 and third portion 8 of the member. This results in a gap 28 forming between the sole 26 and the first portion 4. In reality, it is often the case that the foot portion of the prosthesis is formed of a resilient material, such as silicon, and as such there is partially deformation such that the foot portion partially deforms to conform with the shape of the device 2. As can be seen from the Figures 2a-c, the heel part of the foot portion 22 is located with the third portion 8, the flat of the foot portion 22 is located with or proximal to the first portion 4, and the toe part of the foot portion 22 is located with the second portion 6. As seen in Figure 2a, the user is standing still. The weight of the user is acting in direction 30, through the first portion 4 of the device 2. The first portion 4 is flat with the ground or support surface 100, and the foot of the user is stable. When the user takes a step forward, as indicated in Figure 2b, the weight of the user is shifted forward, and acts in direction 32, through the second portion 6. This causes the device to pivot until the second portion 6 is flat with the ground 100, and the first and third portions 4,8 are angled away from the ground. This motion is similar to the stepping motion of a real foot, when the toes of the foot are the last point of contact with the ground when a step is taken. This allows the leg portion 24 of the prosthesis to be angled forward during the stepping motion, which is allows for a more natural movement of the leg of the user of the prosthesis. When the user places their foot on the support surface after a step has been taken, as indicated in Figure 2c, the initial force of the weight of the user acts along direction 34, and the third portion lies flat with the ground 100. This allows the leg portion 24 to be angled rearward as the step lands, as is the natural position of a real leg when a step is taken. When a user stops walking, the force again acts through the direction 30, as indicated in Figure 2a, and the foot of the user with the device is balanced. Due to the knee joint of a real leg, the angle of the lower leg of a person is further forward when the foot is lifted off the ground than it is rearward when the foot lands during a step. Because of this, the angle of incline of the second portion 6 with respect to the first portion 4 is greater than the angle of incline of the third portion 8 from the first portion. Referring to Figures 3a-c, there is illustrated a device 2 in accordance with the invention. The device 2 has the profile of the sole of a shoe, such that the device may be inserted into a shoe and be complimentary with the same, with no freedom to move within the same. The interface between the first portion 4 and the third portion 8 is perpendicular to the direction of walking of the user. The interface between the first portion 4 and second portion 6 is angled (exaggerated for illustrative purposes), to accommodate the direction of force applied through the sole of the foot portion when a step is taken. It is to be appreciated that the angle and / or location of the interfaces between the portions may be varied by a predetermined amount to accommodate the gait of the individual users. In the illustrated embodiment, the third portion 8 spans 28% of the total length of the device 2, and the second portion 6 spans 35% of the total length of the device 2 at its midline. The device of the illustrated embodiment has a total length of 280mm. The angle of incline of the second portion 6 with respect to the first portion is 28 degrees. The angle of the third portion 8 with respect to the first portion is 7 degrees. It can be seen in Figure 3c that the interfaces 12, 14 are rounded. This enables the device 2 to roll on the ground 100 in use, as a real foot of the user would, and prevents the device from suddenly tipping or rocking in use as the user transitions between the first, second or third portions 4,6,8 being flat with the ground 100. It is to be appreciated that the device 2 may be provided in a variety of shapes and / or sizes to accommodate the different feet sizes of different users. In the illustrated embodiment, the device is formed of carbon fibre and epoxy, particularly a 4-ply carbon-fibre material. For smaller feet sizes, the material may be a 3-ply carbon-fibre material. The device 2 includes a high-friction surface 36 on its underside, formed by brushing the material. This high-friction surface reduces the likelihood that the device will slip within the shoe it is worn. The circumferential edge of the device 2 is rounded to remove any sharp edges or corners that may damage a shoe in which it is inserted or may be dangerous to a user when handling the device. The device 2 has a suitable thickness so as to be suitably rigid to not deform in use. In particular, the thickness of the illustrated embodiment is 4 mm. It will be appreciated that the thickness and / or material density of the device may vary depending on the size of the device, to reflect the size of the foot and approximate weight of the user. For example, a device for use with any UK shoe size of 1-6 may be formed of one ply of 200 gsm carbon fibre and two plies of 600 gsm carbon fibre, and devices for use with any UK shoe size of 7-12 may be formed of one ply of 200 gsm carbon fibre and four plies of 600 gsm carbon fibre. In an alternative embodiment, the device for use with any UK shoe size of 1-6 may be 3mm thick, formed by three layers of 1 mm carbon fibre (3-ply) and a device for use with any UK shoe size of 7-12 may be 4mm thick, formed by 4-ply carbon fibre. This has the beneficial effect that devices for use by an adult will have greater resilience, and therefore greater rigidity, than a device for use by a child. Alternatively, the thickness and / or material properties of the device are selected so as to provide the device with a degree of flexibility to mimic the Achilles tendon of the user and allow the user to propel from a support surface with each step. Referring to Figures 4a-c, there is illustrated a further device 2’, with a reduced thickness. In this embodiment, the reduced thickness allows the device 2 to slightly flex under the weight of the user, increasing the range of motion of the prosthesis in use whilst slightly reducing the stability of the same. Referring to Figures 5a-c, there is illustrated a yet further device 2”, having a substantially uniform thickness 16 of 3.8mm. At the rear of the device, the minimum radius 18 is 1mm, ensuring that there are no pointed edges for a user to find uncomfortable or that may be damaging to the interior of a shoe in which the device 2” is located in use. For the device 2”, the second portion 6” is elevated with respect to the first portion 4” at an angle C. The third portion 8” is elevated with respect to the first portion 4” at an angle D. In this embodiment, angle C is 14 degrees and angle D is 3.5 degrees. Thus, in accordance with the invention, there is provided a device to be used with a prosthesis to enable a user to move their foot through the motions of lifting their foot to take a step, placing their foot, and standing on their foot in a natural manner. The device is a single unitary member with no moveable components and is cheaper and more readily replaceable than complex moveable prosthetic apparatus.

Claims

1. A device for use with a leg prosthesis, the device including a foot member including at least a first portion and a second portion, wherein the first portion is substantially planar and the second portion is inclined with respect to the plane of the first portion.

2. A device according to claim 1, wherein the device is configured to function as a sole or insole member to be used with and / or as part of a leg prothesis.

3. A device according to any preceding claim, wherein the second portion is formed or located at an angle to the first portion.

4. A device according to claim 3, wherein the first portion is configured to lie substantially parallel with a surface on which a user of the device is standing in use and the second portion is inclined to be directed upwards and away from the surface on which a user of the device is standing in use.

5. A device according to claim 4, wherein the incline of the second portion with respect to the first portion is such that applying force to the second portion causes the second portion to lie parallel with the surface on which a user is standing.

6. A device according to any of claims 3-5, wherein the angle of incline of the second portion from the first portion is between 10 and 30 degrees.

7. A device according to claim 6, wherein the angle of incline of the second portion from the first portion is 14 degrees.

8. A device according to any preceding claim, wherein an interface between the first portion and second portion is curved, such that the device may partially roll when force is applied to the second portion.

9. A device according to any preceding claim, wherein the device includes a third portion, said third portion planar and inclined with respect to the first portion.

10. A device according to claim 9, wherein the angle of incline of the third portion from the first portion is between 3.5 and 10 degrees.

11. A device according to claim 10, wherein the angle of incline of the third portion from the first portion is 3.5 degrees.

12. A device according to any preceding claim, wherein the device is a unitary member and formed of a sheet material of uniform thickness.

13. A device according to claim 12, wherein the device is formed of a material and / or has suitable thickness such that there is substantially no deflection of the device caused by the weight of the user during the use of the device.

14. A device according to claim 12, wherein the device is formed of a material and / or has suitable thickness that the device may flex under the weight of the user by a predetermined amount.

15. A device according to claim 14, wherein the predetermined amount by which the device may flex is selected to mimic the Achilles tendon of the user.

16. A device according to any preceding claim formed of a carbon fibre material.

17. A device according to any preceding claim including a locating means such that the device is releasably located with a prosthesis in use.

18. A device according to any preceding claim wherein the device includes a surface with a high friction means to reduce sliding of the device with a surface with which the same is contacted.

19. A device according to any preceding claim wherein the device has a profile that is approximate to the profile of the sole of a real foot.

20. A device for use with a leg prosthesis, the device including a first, second and third planar portions, wherein the second portion and third portion are inclined withrespect to the first portion so as to angle away from a surface with which the first portion is flat against.

21. A device to be located within a shoe, the device including at least a first portion and a second portion, the first portion substantially planar and the second portion inclined with respect to the first portion.A

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