Ankle-foot orthosis

Abstract

An ankle-foot orthosis includes a plantar flexion limiting device that limits the plantar flexion of the foot and which is configured to provide support for a user's foot drop. The ankle-foot orthosis includes a lower leg shell including a foot support and a lower leg support, and is configured to position and/or fix a user's heel in the lower leg support. The plantar flexion motion of the foot is limited by the complementary action of elastic and non-elastic portions of the plantar flexion limiting device. The plantar flexion limiting device further leads to a dynamic return of the foot to an angle substantially equal to the angle value .sub.2.

Claims

1. An ankle-foot orthosis for providing support for a user's foot drop, comprising: a substantially L-shaped lower leg shell having an elongate lower leg support configured to be placed against a rear side of a user's lower leg and an elongate foot support configured to support at least part of an underside of a metatarsus, said lower leg support and foot support are oriented at an adjustable angle relative to each other; a plantar flexion limiting device which is configured to allow a smooth foot strike of a foot of the user supported by the ankle-foot orthosis, said plantar flexion limiting device having a substantially non-elastic portion and a substantially elastic portion, wherein the non-elastic portion is configured to impede the angle exceeding an angle value .sub.2 and wherein the elastic portion is configured to effect a dynamic return of the user's foot to an angle equal to the angle value .sub.2 when the angle exceeds the angle value .sub.2; wherein said non-elastic portion of said plantar flexion limiting device includes a first non-elastic strap attached to said lower leg shell and a second non-elastic strap attached to said lower leg shell, and wherein an end of said first non-elastic strap and an end of said second non-elastic strap are connected together so that the connected ends are in contact with each other; wherein the connected ends of said first non-elastic strap and said second non-elastic strap are attachable to a fastener on said lower leg support, and wherein the position of the connected ends on the fastener is adjustable to modify the angle value .sub.2; and wherein said plantar flexion limiting device is configured to position and/or orient a user's heel in the lower leg support.

2. An ankle-foot orthosis according to claim 1, wherein the non-elastic portion is configured to position and/or orient a user's heel in the lower leg support.

3. An ankle-foot orthosis according to claim 1, wherein the plantar flexion limiting device is configured to fix an end of the foot support that is remote from the lower leg support to the foot of the user.

4. An ankle-foot orthosis according to claim 3, wherein the non-elastic portion is configured to fix the end of the foot support that is remote from the lower leg support to the foot of the user.

5. An ankle-foot orthosis according to claim 3, wherein the elastic portion and the non-elastic portion can at least in part be detachably connected to the L-shaped lower leg shell.

6. An ankle-foot orthosis according to claim 1, wherein the non-elastic portion is configured to effect a dynamic return of the user's foot to an angle substantially equal to the angle value .sub.2 when the angle exceeds the angle value .sub.2.

7. An ankle-foot orthosis according to claim 1, wherein the ankle-foot orthosis further comprises a lower leg support fixing device by which an end of the lower leg support that is remote from the foot support can be fixed tightly to the lower leg.

8. An ankle-foot orthosis according to claim 1, wherein the angle value .sub.2 substantially ranges between 80 and 100.

9. An ankle-foot orthosis according to claim 1, wherein the non-elastic portion forms a connection between the foot support and the lower leg support in use, such that this connection will only transmit a force between the foot support and the lower leg support when the angle exceeds the angle value .sub.2.

10. An ankle-foot orthosis according to claim 9, wherein the connection of the non-elastic portion between the foot support and the lower leg support is formed by at least one of said first non-elastic strap and said non-elastic second strap, whose shape and positioning determine the adjustable angle value .sub.2 in use.

11. An ankle-foot orthosis according to claim 10, wherein at least one of the first non-elastic strap and the second non-elastic strap is configured to partially extend crosswise from one side of the foot support, over the foot, to an other side opposite the one side of the foot support.

12. An ankle-foot orthosis according to claim 11, wherein said first non-elastic strap is attached to one side of the foot support and said second non-elastic strap is attached to the other side opposite the one side of the foot support.

13. An ankle-foot orthosis according to claim 1, wherein the lower leg support and the foot support are connected by means of a rear foot support portion configured to support an underside of a rear part of a foot, wherein the rear foot support portion extends substantially transversely to the lower leg support in a direction of the foot support, at the angle equal to the angle value .sub.2, and wherein the rear foot support portion is flexibly connected to the foot support.

14. An ankle-foot orthosis according to claim 1, wherein the elastic portion is elastic in use, to such an extent that when the angle increases beyond the angle value .sub.2 said elastic plantar flexion limiting means will exert a force that drives back the foot to the angle substantially equal to the angle value .sub.2.

15. An ankle-foot orthosis according to claim 1, wherein the elastic portion extends from one side of the foot support to an other side opposite the one side of the foot support in use.

16. An ankle-foot orthosis according to claim 15, wherein the elastic portion includes at least one elastic strap connected to the foot support, wherein the at least one elastic strap extends from one side of the foot support to a side of the lower leg support on the side of an other side opposite the one side of the foot support.

17. An ankle-foot orthosis according to claim 16, wherein the elastic portion includes at least two elastic straps connected to the foot support, which straps extend crosswise over the foot in use.

18. An ankle-foot orthosis according to claim 1, wherein plantar flexion limiting device is configured to preventing a foot from twisting inward, seen from a user's viewpoint, relative to an associated ankle joint.

19. An ankle-foot orthosis according to claim 1, wherein the plantar flexion limiting device is configured to preventing a foot from twisting outward, seen from a user's viewpoint, relative to an associated ankle joint.

20. An ankle-foot orthosis according to claim 19, wherein the non-elastic portion is configured to prevent the foot from twisting inward, seen from a user's viewpoint, relative to an associated ankle joint and wherein the elastic portion is configured to prevent the foot from twisting outward, seen from a user's viewpoint, relative to an associated ankle joint.

Description

(1) The present invention will be explained in more detail below with reference to the appended figures, in which:

(2) FIG. 1 is a perspective view of an ankle-foot orthosis according to the present invention in the open position for receiving a lower leg;

(3) FIG. 2 is a perspective view of an ankle-foot orthosis according to the present invention during use thereof;

(4) FIG. 3 is a side view of an ankle-foot orthosis according to the present invention, in which the angle is smaller than the angle value .sub.2;

(5) FIG. 4 is a perspective view of a rear side of an ankle-foot orthosis according to the present invention;

(6) FIG. 5 is a perspective view of an embodiment of an ankle-foot orthosis according to the present invention, in which the non-elastic straps are arranged substantially parallel to each other;

(7) FIG. 6 is a side view of an embodiment of an ankle-foot orthosis according to the present invention, in which the non-elastic plantar flexion limiting means are provided on the underside of the foot support.

(8) Identical elements are as much as possible indicated by the same numerals in the description below. To avoid unnecessary repetition, such elements are not introduced anew in every drawing.

(9) FIG. 1 shows in perspective view an ankle-foot orthosis 1 according to the present invention in the open position for receiving a lower leg 21 (not shown in FIG. 1) in the lower leg shell 2 thereof. The foot support 3 is preferably modelled on the shape of a user's foot. The foot support 3 is preferably thin so as to make it possible to use the orthosis 1 in combination with a shoe (not shown). The foot support 3 is connected to the rear foot support portion 5, which is positioned under the rear portion of a user's foot in use. The rear foot support portion 5 can extend up to the rear side of the lower leg in use, but it is also possible for the rear foot support portion 5 to extend up to a position is spaced from the rear side of the lower leg. The heel opening 8 also extends on the underside of the heel of the foot 21a in that case. The rear foot support portion 5 and the foot support 3 preferably form one plane, which is substantially identical to the shape of the sole of the user's foot. In one embodiment, the foot support 3 leaves clear the underside of at least the toes.

(10) In FIG. 1, the lower leg support 7 extends in vertical direction from the rear foot support portion 5, substantially perpendicular to the foot support 3. The lower leg support 7 is connected to the rear foot support portion 5. This connection is preferably a rigid connection. In use, side walls 9 are provided between the rear foot support portion 5 and the lower leg support 7 on either side of a user's ankle. Each side wall 9 is provided with an opening 11. As shown in FIG. 1, the lower leg support 7 widens in upward direction, so that the side portions 13 of the lower leg support 7 extend partially around the lower leg 21. Seen from a user's viewpoint, the lower leg support 7 is positioned substantially behind the lower leg 21, with the side portions 13 of the lower leg support 7 positioned to the left and to the right of the lower leg 21. Thus, also the side walls 9 can be placed substantially to the left and to the right of the ankle 21b and/or the heel. A second fastener 15 for an elastic strap 23 is provided on each of the side portions 13 of the lower leg support 7. At the rear side of the lower leg support 7, a first fastener 17 for a non-elastic strap is provided. A third fastener 19 (which is not shown in FIG. 1, but whose position is broadly indicated at 19 in FIG. 4) for a lower leg strap 27 is provided at the top of the lower leg support 7 of the orthosis 1 in FIG. 1. This third fastener 19 for a lower leg strap 27 is preferably formed by VELCRO, buttons, hooks or a slot through which the lower leg strap 27 can extend.

(11) In FIG. 1, the upper side of the lower leg support 7 is connected to a lower leg strap 27 which is configured to function as lower leg support fixing means 27. The lower leg strap 27 is fixedly connected to the lower leg support 7 at one end and can be detachably connected to the third fastener 19 for a lower leg strap 27 at another end.

(12) A non-elastic strap 25 is attached to both sides (left-hand side and right-hand side, seen from a user's viewpoint) of the foot support 3, near the front side of the foot support 3. Each non-elastic strap 25 extends from its attachment to the foot support 3 to the opening 11 in the side wall 9, which is located on the side of the foot support 3 opposite the attachment to the foot support 3. In other words, one non-elastic strap 25 extends from its attachment on the left-hand side of the foot support 3 to an opening 11 on the right-hand side of the foot support 3, whilst the other non-elastic strap 25 extends from the right-hand attachment to the left-hand opening 11. At some point the non-elastic straps 25 cross one another. The non-elastic straps 25 further extend through the openings 11, behind which the non-elastic straps 25 are connected together at their ends. The connected ends of the non-elastic straps 25 can be connected to the first fastener 17 for a non-elastic strap 25.

(13) Between the attachments of the non-elastic straps 25 and the lower leg support 7, in particular the rear foot support portion 5, two elastic straps 23 extend from the foot support 3 on opposite sides of the foot support 3. One elastic strap 23 is connected to the left-hand side of the foot support 3, whilst the other elastic strap 23 is connected to the right-hand side of the foot support 3. The elastic straps 23 can be connected to the elastic strap fasteners 15.

(14) FIG. 2 shows in perspective view an ankle-foot orthosis 1 according to the present invention during use. A lower leg 21 is placed in the lower leg shell 2 in such a manner that the rear side of the lower leg 21 closely abuts the lower leg support 7. The foot 21a rests on the foot support 3, with the rear portion of the foot 21a positioned on the rear foot support portion 5. The heel and part of the ankle 21b of the foot 21 are in part enclosed by the side walls 9.

(15) The lower leg strap 27 extends substantially horizontally around the lower leg 21. In FIG. 2, the lower leg strap 27 is fixed to the lower leg support 7 with one end and detachably connected to the third fastener 19 for a lower leg strap 27 with the other end, for example by means of VELCRO. The position of the lower leg strap 27 on the third fastener 19 for a lower leg strap 27 can be adjusted for realising a close abutment at varying circumferential dimensions of the lower leg 21.

(16) The non-elastic straps 25 form the non-elastic plantar flexion limiting means. Each non-elastic strap 25 can be connected to the first fastener 17 for a non-elastic strap 25 of the lower leg support 7 in such a manner that there will be a tension on the non-elastic strap 25. The adjusted position on the lower leg support 7 and the thus defined length of the non-elastic straps 25 determine the angle value .sub.2 for the angle between the foot support 3 and the lower leg support 7. By attaching the non-elastic straps 25 at a higher position on the lower leg shell, the bias on said straps 25 will be increased. After being attached to the lower leg support 7, the non-elastic straps 25 effectively impede an increase of the angle , which increase is known as plantar flexion. At an angle equal to the angle value .sub.2, the non-elastic straps are capable of compensating the relatively large reactive force exerted on a foot being placed on the ground. It is possible to adjust the angle value .sub.2 by changing the position of the fastener of the non-elastic straps 25 on the lower leg support 17. A lower position, in use, preferably results in an increase of the angle value .sub.2.

(17) A decrease of the angle is not impeded by the non-elastic straps 25. When the foot support 3 pivots toward the lower leg support 7, the tension is released from the non-elastic straps 25. The non-elastic straps 25 than become slack, as it were, so that the foot support 3 can pivot in the direction of the lower leg support 7 without being impeded. Dorsiflexion of the ankle 21b is thus not impeded by the orthosis 1. A user wearing the orthosis 1 according to the present invention can still freely move his or her knee forward, so that the stride will feel natural. In addition to that, a user can thus get up more easily, for example from a chair.

(18) In use, the non-elastic straps 25 extend over the foot 21a, thereby positioning and/or fixing the foot 21a on the foot support 3. The non-elastic straps 25 thus also form the foot support fixing means by which the end of the foot support 3 remote from the lower leg support can be placed into close abutment with the foot 21a.

(19) The non-elastic straps 25 further form the heel fixing means. The non-elastic straps 25 position and fix the foot 21a in the lower leg shell 2 during the stride in that the non-elastic straps 25 are just themselves to the foot 21a during the stride. The user thus has freedom of movement without the position of the foot 21a in the lower leg shell 2 being lost. In addition to that it is conceivable for the non-elastic straps 25 to contribute toward returning the foot to an angle substantially equal to the angle value .sub.2 when the angle exceeds the angle value .sub.2. Use can be made in this regard of the shape-retaining property of the lower leg shell 2. Upon deformation of the lower leg shell 2 in the case of an increase of the angle beyond the angle value .sub.2, the lower leg shell 2 will exert a reactive force against the movement of the deformation, which reactive force can be transmitted to the foot 21a by the non-elastic straps 25 for driving back the foot 21a to an angle substantially equal to the angle value .sub.2.

(20) As FIG. 2 shows, two elastic straps 23 are arranged over the non-elastic straps 25 and the foot 21a. The elastic straps 23 are attached to opposite sides of the foot support 3, one elastic strap 23 on the left-hand side and the other elastic strap 23 on the right-hand side of the foot support 3. The elastic straps 3 each extend from their attachment to the foot support 3 to the opposite side of the foot support 3, i.e. one elastic strap 23 from the left to the right and the other elastic strap 23 from the right to the left. The elastic straps 23 are arranged over the non-elastic straps 25.

(21) The elastic straps 23 form the elastic plantar flexion limiting means. As shown in FIG. 2, the elastic straps 23 cross on the instep. The elastic straps 23 can furthermore be detachably connected to the second fastener 15 four and the elastic strap 23 on the sides 13 of the lower leg support 7, for example by means of VELCRO, buttons, hooks or other known means of attachment. The elastic straps 23 can thus be biased to a desired value by adjusting the position of the connection to the second fastener 15 for an elastic strap 23. The relative strength of the force by which the elastic straps return the foot to an angle substantially equal to the angle value .sub.2 can thus be adjusted by the user himself, if desired.

(22) When the angle value .sub.2 is exceeded, the elastic straps 23 will return the foot 21a to an angle substantially equal to the angle value .sub.2. In use, the elastic straps 23 form an elastic connection between the foot support and the lower leg support 7. When the angle increases beyond a predetermined angle value, which may equal .sub.2, the elastic straps 23 will stretch to such an extent as to exert a force that urges the foot support 3 and the lower leg support 7 toward each other. This force causes the foot 21a to return to an angle substantially equal to the angle value .sub.2. As the angle increases, this force will become stronger as a result of the elastic straps 23 being stretched further. The elastic straps 23 thus form the elastic plantar flexion limiting means for realising a smooth strike of the foot 21a and a dynamic return of the foot 21a to an angle substantially equal to the angle value .sub.2. At an angle substantially equal to the angle value .sub.2, the foot takes up the position of the foot 21a shown in FIG. 2, in which FIG. 2 the angle value .sub.2 is about 90.

(23) FIG. 3 shows a side view of an ankle-foot orthosis according to the present invention, in which the foot support 3 is bent in relation to the rear foot support portion 5. The toot support 5 essentially makes an angle with the vertical direction in FIG. 3, in which FIG. 3 the angle is less than .sub.2, viz. about 45.

(24) When the heel is placed on the ground, the foot 21 will experience a downward slapping moment. While walking, a user first places his heel on the ground, keeping the foot 21a away from the ground surface. This phase of the gait cycle is known as the initial contact. Upon touching the ground surface, the foot experiences a reactive force of a magnitude of about seven times the user's body weight. This reactive force leads to a moment of force on the foot 21a, causing it to pivot about an axis in a user's lateral direction, which axis is located in or near the ankle 21b. This lever effect forces the foot 21a to slap. A user with foot drop is not able to take up these forces.

(25) The non-elastic straps 25 according to the present invention are capable of taking up at least a significant part of the initial slap of about seven times the body weight. The elastic straps 23 also contribute, to a lesser extent, toward taking up this slap and in addition to that dynamically return the foot to the neutral position. As a result, the stride will feel and look more natural when the orthosis 1 according to the present invention is used. In addition to that, the orthosis 1 according to the present invention leads to an energy-efficient stride.

(26) FIG. 3 shows the flexibility of the foot support 3, which enables the foot support 3 to closely abut the foot 21a during the stride. The foot support 3 is configured so that it can deform so as to continuously conform to the shape of the sole of the foot without this causing any discomfort to the user.

(27) The orthosis 1 according to the present invention further contributes toward reducing the inversion and eversion (sideways twisting of the foot 21a). Because the non-elastic straps 25 extend from one side of the foot support to the opposite side of the foot support 3, they are capable of taking up an inversion and/or eversion movement. When, for example, a left foot 21a twists inward in a so-called inversion movement, the tension on at least the non-elastic strap 25 that is connected to the left-hand side of the foot support 3 will increase. This non-elastic strap 25 thus limits the extent of twisting by transmitting a tilting moment opposed to the inversion movement to the foot support 3. The non-elastic straps 25 thus increase the stability for a user.

(28) FIG. 4 shows the rear side of an orthosis 1 according to the present invention. A heel opening 8 is provided in the lower leg support 7. The opening 8 is oval in shape in this exemplary embodiment so as to provide a proper abutment of the lower leg shell 2 against a user's heel.

(29) FIG. 5 shows in perspective view an embodiment of an ankle-foot orthosis 1 according to the present invention, in which the non-elastic straps 125 are arranged substantially parallel to each other. Each non-elastic strap 125 extends from its attachment to the foot support 3, along one side of the foot 21a, to a first fastener 17 for a non-elastic strap 25. The non-elastic strap 125 that is attached to the left-hand side of the foot support 3 extends along and over the left-hand side of the foot 21a to the first fastener 17 for a non-elastic strap 25.

(30) The elastic plantar flexion limiting means 123 are configured as a tight-fitting envelope 123 of the foot 21a. The envelope 123 is an elastic stocking, for example, which is connected to the lower leg shell 2. The envelope 123 is accessible to a foot 21a via a re-closeable closure on the front side of the envelope 123.

(31) FIG. 6 shows a side view of an embodiment of an ankle-foot orthosis 200 according to the present invention, in which the non-elastic plantar flexion limiting means 225 are provided under the underside of the foot support. A rigid plate 225 extends forward under the foot support 3, transversely to the lower leg support 7. The plate 225 is rigid to such an extent that it can impede pivoting of the foot support 3 beyond an angle .sub.2.

(32) In the foregoing, the invention has been described with reference to a few exemplary embodiments. Those skilled in the art will appreciate that many modifications and alternatives are possible within the scope of the invention. The invention is not limited to these exemplary embodiments, however. The protection sought is defined by the appended claims.