Note: Descriptions are shown in the official language in which they were submitted.
CA 02719771 2010-10-26
Title
ANKLE FOOT ORTHOSIS
Scope of the Invention
[0001] The present invention relates to orthotics, and in particular, to an
ankle foot
orthosis for correcting foot drop symptoms.
Background of the Invention
[00021 Foot drop is a condition where a person has a limited ability or an
inability to
raise his or her foot at the ankle joint due to weakness or paralysis of the
muscles that lift the
foot. This leads to difficulty in walking. When the user raises his or her
foot to take a step,
the toes tend to drag on the ground or the person must use their hip muscles
to exaggerate
lifting the foot above the ground.
[0003] Foot drop may be caused by muscle or nerve damage, muscle or nerve
disorders,
or central nervous system disorders. For example, an injury to the muscles
that control the
ankles and toes can cause foot drop. As another example, disorders that affect
the spinal cord
or brain, such as amyotrophic lateral sclerosis (ALS) or stroke, may cause
foot drop. In
addition, foot drop may be an unwanted side effect of various medications,
including some
chemotherapy drugs used to treat cancer and some drugs used to treat multiple
sclerosis.
[0004] Ankle foot orthoses (AFO) are known devices which are used to remediate
foot
drop symptoms.
100051 Known ankle foot orthoses include large splints which extend from the
top of the
user's calf down to the back of the heel and forward to the middle of the foot
or to the toes.
Examples of such splints are taught in U.S. Patent No. 6,827,696 to Maguire
and U.S. Patent
No. 7,270,644 to Ingimundarson. These splints lock the ankle joints so that
the sole of the
foot is kept perpendicular to the tibia axis, and prevent the toes from
dragging on the ground.
Such splints are uncomfortable and heavy, making it cumbersome to walk. These
splints are
also large and unsightly, thus drawing attention to the user's foot drop
condition. These
splints are generally not bendable, and therefore, prone to breakage.
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[0006] Many known ankle foot orthoses require professional fitting procedures,
which
includes taking impressions of the affected foot to be used in manufacturing a
custom sized
and shaped ankle foot orthosis. Such professional fittings procedures are
costly and there is a
delay between the fitting and the user receiving the ankle foot orthosis.
[0007] Many ankle foot orthoses also require the use of customized shoes. Such
customized shoes are costly, and do not allow users to buy conventional shoes.
Summary of the Invention
[0008] To at least partially overcome the disadvantages of previously known
ankle foot
orthoses, the present invention provides a new ankle foot orthosis.
[0009] An object of the present invention is to provide a new ankle foot
orthosis to
correct foot drop symptoms.
[0010] Another object of the present invention is to provide an ankle foot
orthosis which
is comfortable to wear and light in weight.
[0011] A further object of the present invention is to provide an ankle foot
orthosis which
is durable and washable.
[0012] Yet another object of the present invention is to provide an ankle foot
orthosis
which is relatively small in size and discrete.
[0013] Another object of the present invention is to provide a ankle foot
orthosis which is
inexpensive and which can be transferred from one piece of footwear to another
without any
difficulty.
[0014] A further object of the present invention is to provide an ankle foot
orthosis which
can be used with conventional shoes, boots, slippers and sandals.
[0015] Another object of the present invention is to provide an ankle foot
orthosis which
does not require the user to have a professional fitting.
[0016] The present invention provides a novel ankle foot orthosis. In one
aspect, the
present invention provides an ankle foot orthosis for correcting foot drop
symptoms.
[0017] The ankle foot orthosis comprises a cuff for securement around a user's
ankle,
and an attached elastic component comprising a first attached end and a second
closed-hook
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end; wherein the elastic component has an inherent bias to assume a condition
in which a
distance between the first end and the second end is an unextended length;
wherein when
tension is applied to the elastic component against the inherent bias, the
distance between the
first end and the second end increases to an extended length, and the inherent
bias attempts to
return the elastic component to the unextended length; wherein the first end
of the elastic
component is fastened to the cuff at the front of the user's ankle; wherein
the second end of
the elastic component is fastened to a vamp of a footwear garment being worn
on the user's
foot at a location above the user's foot and closer to the user's toes than to
the user's ankle.
[0018] The angle between the sole of the user's foot and an axis of the user's
tibia is
referred to as a drop angle. Preferably, the elastic component is in a
condition without
tension when the drop angle is less than 90 degrees, and the elastic component
is first placed
in a condition under a tension when the drop angle is an initial tension angle
in the range of
90 degrees to 100 degrees.
[00191 Preferably, when the user lifts his or her foot above the ground with
the user's
tibia generally vertical and the user's foot is relaxed, an equilibrium
condition occurs in
which the inherent bias of the elastic component equals a force required to
support the foot
and the drop angle is an equilibrium angle of 90 degrees.
[00201 Preferably, the inherent bias prevents the drop angle from exceeding a
maximum
angle of 135 degrees.
[0021] The initial tension angle is more preferably about 90 degrees. The
equilibrium
angle is more preferably in the range of 90 degrees to 100 degrees, and more
preferably
about 90 degrees.
[0022] Preferably, the cuff is wrapped securely around the user's ankle so as
to conform
to the size and shape of the user's ankle. The cuff is engaged around the
ankle to resist
sliding downwardly relative to the ankle.
[0023] Preferably, the cuff may be a panel which wraps around the user's
ankle. The
panel has two ends, such that when the panel is wrapped around the user's
ankle, one end is
secured to the other end to form a closed loop.
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[00241 The first end of the panel may, for example, be secured to the second
end of the
panel using a velcro hook and loop fastener. A fabric hook section is present
on the first
end of the panel and a fabric loop section is present on the second end of the
panel. When
the fabric hook section and the fabric loop section are pressed together,
hooks in the fabric
hook section catch loops in the fabric loop section to secure the first end
and the second end
together.
[00251 The panel may be made of many different types of materials, such as an
elastomer
or a textile. Preferred textiles are cotton, polyester, acrylic, nylon,
spandex and blends
thereof.
[00261 The cuff preferably has an outer layer and an inner layer. For example,
the cuff
may have an outer layer comprising an elastomer or a textile and an inner
layer comprising a
padding material selected from the group consisting of foam, felt, and
neoprene.
[00271 The elastic component may be, for example, an elastic band, an elastic
cord or a
shock cord.
[00281 The first end of the elastic component is preferably permanently
fastened to the
cuff at the front of the user's ankle by sewing, gluing or heating the elastic
to the cuff.
[00291 The permanently fastened end of the elastic component is preferably
protected by
a grommet that surrounds the elastic at the outer surface. The grommet may be
made from
plastic or metal.
[00301 The second end of the elastic component is preferably fastened to the
vamp of the
footwear garment by a snap hook. The snap hook may have a spring-loaded
closure.
Preferably, the snap hook is attached to the laces on the footwear garment.
Alternatively, this
snap hook may be attached to a closed loop or a closed band which is part of
the footwear
garment. Alternatively, this snap hook may be attached to one or more holes in
the footwear
garment.
[00311 The second end of the elastic component preferably fastens to the vamp
at a
location proximal to or at the user's toes.
[00321 The footwear garment to be used with the ankle foot orthosis of the
present
invention is preferably a shoe, a boot, a sandal, a slipper or a sock.
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Brief Description of the Drawings
[0033] Further aspects and advantages will become apparent from the following
description taken together with the accompanying drawings in which:
[0034] Figure 1 is a perspective view of an ankle foot orthosis in accordance
with a
preferred embodiment of the present invention.
[0035] Figure 2 is a partial perspective view of the ankle foot orthosis shown
in Figure 1
when applied to a user wearing a conventional shoe.
[0036] Figure 3 is a side view of the ankle foot orthosis applied to a user
wearing the
conventional shoe shown in Figure 2.
[0037] Figure 4 is a side view of the ankle foot orthosis applied to a user
wearing the
conventional shoe shown in Figure 2 when the user's foot is resting flat on a
horizontal
surface.
[0038] Figure 5 is a side view of the ankle foot orthosis applied to a user
wearing the
conventional shoe shown in Figure 2 when the user lifts his or her foot above
the horizontal
surface to take a step.
[0039] Throughout all the drawings in the disclosure, similar parts are
indicated by the
same reference numerals.
Description of the Preferred Embodiment
[0040] Reference is made to Figures 1 to 5 which show a preferred embodiment
of the
present invention.
[0041] Figure 1 illustrates a preferred embodiment of the present invention.
The ankle
foot orthosis 10 includes: a cuff 12 which is to be secured around a user's
ankle; and an
elastic component 14.
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[0042] The cuff 12 is a panel which is generally rectangular in shape.
Preferably, the
cuff 12 is about 15 cm to 40 cm long and about 8 cm wide, which allows for
wrapping the
cuff 12 around ankles of many different sizes.
[0043] The cuff 12 has an outer surface 70 and an inner surface 72. When
wrapped
around an ankle, the outer surface 70 faces outwards and away from the ankle,
while the
inner surface 72 faces inwards and is in direct contact with the ankle, with
or without a sock
wrapped around the ankle.
[0044] The cuff 12 has a first end 16 and a second end 18. The first end 16
has a fabric
hook section 20 on the outer surface 70 of the cuff 12. The second end 18 has
a fabric loop
section 22 on the inside of the extended outer surface 70 of the cuff 12.
[0045] When in use, the cuff 12 is wrapped around the user's ankle. The fabric
hook
section 20 on the first end 16 is pressed together with the fabric loop
section 22 on the second
end 18, such that the hooks in the fabric hook section 20 catch in the loops
in the fabric loop
section 22, thus securing the two ends 16, 18 to each other, and forming a
closed loop around
the ankle. The cuff 12 is wrapped securely around the user's ankle such that
is resists sliding
above the ankle and resists sliding below the ankle.
[0046] Any portion of the fabric hook section 20 can be pressed together with
any
portion of the fabric loop section 22 to secure the cuff 12 around the user's
ankle. This
allows the length of the cuff 12 to be adjusted to ankles of many different
sizes.
[0047] The cuff 12 can be made from many different types of materials. For
example,
the cuff 12 may be made of conumn textile materials such as cotton, polyester,
acrylic,
nylon, neoprene and blends thereof. The cuff 12 may also be made of
stretchable textile
materials such as spandex. Alternatively, the cuff 12 may be made of an
elastomer.
[0048] The cuff 12 is preferably padded. For example, the cuff 12 may have an
outer
layer and an inner layer. The outer layer can be made, for example, from any
of the different
textile materials described above. The inner layer can be made from foam to
provide
padding. The foam may be a closed cell structured foam, such as a compressible
closed cell
foam neoprene, or an open cell structured foam, such as an open cell
polyurethane.
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[0049] The padded inner layer will be wider by 4 to 5 cm to allow for comfort
and to
prevent slippage on the ankle.
[0050] The inner layer preferably has a thickness of about 3 to 5 mm. The
outer layer
preferably has a thickness of about 1 to 2 mm.
[0051] The elastic component 14 can be an elastic band, elastic cord, or shock
cord such
as a bungee cord.
[0052] The elastic component 14 is protected by a grommet 24 that is
permanently
fastened to the outer surface 70.
[0053] The grommet 24 can be made of many different types of materials, such
as plastic
or metal.
[0054] There is a fastener 32 at a second end of the elastic component 14.
[0055] The preferred fastener 32 is a snap hook with a closed gate 36. The
fastener 32 is
to be attached to the vamp of a footwear garment being worn on the user's
foot.
[0056] The fastener 32 can be made of many different types of materials, such
as plastic
or metal.
[0057] Figures 2 and 3 illustrate the preferred ankle foot orthosis 10 when
applied to a
user. The cuff 12 is wrapped around the user's ankle 50. The fabric hook
section 20 on the
first end 16 of the cuff 12 is pressed together with the fabric loop section
22 on the second
end of the cuff 12 to secure the two ends 16, 18 to each other and to form a
closed loop
around the ankle 50. Any portion of the fabric hook section 20 can be pressed
together with
any portion of the fabric loop section 22, allowing the user to adjust the
length of the cuff 12
so as to form a snug fit which conforms to the size and shape of the ankle 50.
The snug fit
helps to prevent the cuff 12 from sliding above the ankle 50 or below the
ankle 50.
[0058] The cuff 12 can be wrapped so that it is in direct contact with the
skin around the
user's ankle 50. Alternatively, the cuff 12 can be wrapped over a sock worn by
the user and
around the user's ankle 50.
[0059] Preferably, the cuff 12 has an inner layer of foam padding inside an
outer layer of
textile to provide cushioning.
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[0060] In the preferred embodiment illustrated in Figures 2 and 3, the user is
wearing a
conventional shoe 60. The shoe 60 has a vamp 62 with two parallel rows of
holes 64. The
two parallel rows of holes 64 extend from a location proximal to the front of
the ankle to a
location proximal to the toes. A lace 66 is threaded through the two parallel
rows of holes 64
in a crisscross configuration with the two ends of the lace 66 extending out
the top pair of
holes closest to the user's ankle. The user ties the two ends of the lace 66
together.
[0061] The elastic component 14 is attached to both the cuff 12 and the shoe
60.
[0062] The user pushes the spring-loaded closure 36 of the fastener 32 inwards
to open it.
The fastener 32 is hooked around lace 66 on the vamp 62 of the shoe 60. The
user releases
the closure 36 so that it closes, thus forming a secure attachment between one
end of the
elastic component 14 and the lace 66 on the shoe 60. Preferably, the fastener
32 attaches to
the lace 66 at the bottom pair of holes 64 which are closest to the user's
toes.
[0063] In alternative embodiments, the ankle foot orthosis 10 of the present
invention can
be used with any other type of footwear garment, including boots, slippers,
sandals and
socks.
[0064] In one alternative embodiment, the fastener 32 can be attached to the
laces of a
boot, slipper or sandal. In another alternative embodiment, the fastener 32
can be attached to
a closed ring or closed band, where the ring or band is part of a shoe, boot,
slipper or sandal.
In yet another alternative embodiment, holes can be punched, drilled or cut
into the vamp of
a shoe, boot, slipper, sandal or sock to allow the fastener 32 to attach
thereto.
[0065] As illustrated in Figures 4 and 5, when the ankle foot orthosis 10 of
the present
invention is applied to the user, the user's foot drop symptoms are corrected.
Without the
ankle foot orthosis 10, the user would only have a limited ability or an
inability to raise his or
her foot at the ankle joint. As such, when the user raises his or her foot to
take a step, the
user's toes will tend to drag on the ground. When the ankle foot orthosis 10
is applied to the
user, such foot drop symptoms are corrected.
[0066] As shown in Figure 4, before taking a step, the user's foot 200 rests
flat on the
ground 100. The ground 100 prevents the user's foot 200 from dropping about
the user's
ankle 50. There is a drop angle D of 90 degrees between the sole of the user's
foot 200 and
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the axis of the user's tibia 300. This is the initial tension angle where the
elastic component
14 is first placed in a condition under tension and there is no slack.
[0067] As shown in Figure 5, when the user lifts his or her foot above the
ground 100 to
take a step with the user's tibia 300 generally vertical and the user's foot
200 is relaxed, the
user's foot 200 will begin to drop at the toes. When this drop occurs, an
equilibrium
condition occurs in which the inherent bias of the elastic component 14 equals
a force
required to support the foot and the drop angle D is an equilibrium angle of
from 90 degrees
to 100 degrees.
[0068] The cuff 12 serves as an anchor for the elastic component 14. The
tensile force
necessary to support the foot 200 in an orientation where the sole of the foot
200 is
approximately perpendicular to the axis of the tibia 300 is transmitted
through the elastic
component 14. The entire tensile load is diffused through the cuff 12 and
distributed around
the ankle 50, including the lateral and medial sides.
[00691 The elasticity of the elastic component 14 helps the user to create a
natural gait
when walking. When the user raises his or her foot 200 above the ground to
take a step, the
elastic component 14 keeps the drop angle D at the equilibrium angle in the
range of 90
degrees to 100 degrees which effectively positions the foot 200 for a natural
and comfortable
heel to toe step, followed by a natural and comfortable lifting of the foot
200 after each step.
[0070] The attachment of the elastic component 14 to the cuff 12 at the front
of the user's
ankle 50 provides a simple, stronger and more effective anchor for the elastic
component 14.
By attaching to the cuff 12 at the front of the ankle 50, the elastic
component 14 does not
need to extend around to the side or back of the user's ankle 50. By attaching
to the cuff 12
at the front of the ankle 50, the elastic component 14 can raise the toes
directly towards the
front of the ankle 50, instead of towards the side of the ankle 50, thus
allowing for a more
natural and comfortable heel to toe step.
[0071] The attachment of the elastic component 14 to the vamp 62 at a location
proximal
to or at the user's toes is preferred. This allows the elastic component 14 to
raise the foot 200
close to or at the location which experiences the largest drop when the user
cannot raise his
or her foot 200 at the ankle joint.
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100721 The ankle foot orthosis of the present invention is more comfortable
and lighter in
weight than previous devices, such as splints. Unlike the previous splints,
the ankle foot
orthosis of the present invention is not prone to breakage. The ankle foot
orthosis of the
present invention is easily washed. It is relatively small in size and
discrete for the user to
wear, especially if hidden under pant legs. The ankle foot orthosis can be
transferred from
one footwear garment to another because it is easily attachable and
detachable. Many
conventional shoes, boots, slippers and sandals can be used with the ankle
foot orthosis of the
present invention.
[00731 Although this disclosure has described and illustrated preferred
embodiments of
the invention, it is to be understood that the invention is not restricted to
these particular
embodiments. Rather, the invention includes all embodiments that are
functional or
mechanical equivalents of the specific embodiments in features that have been
described and
illustrated herein. Many modifications will now occur to those skilled in the
art. For a
definition of the invention, reference is made to the following claims.
