U.S. patent application number 10/762613 was filed with the patent office on 2004-09-02 for plantar pressure and shear stress reduction insole for diabetic foot ulceration.
Invention is credited to Nguyen, Hienvu Chuc.
Application Number | 20040168354 10/762613 |
Document ID | / |
Family ID | 32912236 |
Filed Date | 2004-09-02 |
United States Patent
Application |
20040168354 |
Kind Code |
A1 |
Nguyen, Hienvu Chuc |
September 2, 2004 |
Plantar pressure and shear stress reduction insole for diabetic
foot ulceration
Abstract
The main purpose of this invention is to develop a new insole
design which can significantly reduce the plantar pressure under
the forefoot and heel, and can be used as replacement insole for
the diabetic shoe, diabetic healing shoe, and removable cast
walker. This new insole is consisting of shock absorbing and shear
reducing composite layers of Poron or soft EVA for the bottom
layer, Plastazote or cushioned polymer gel for the middle layer,
and a closed cell Neoprene top cover. These materials are
commercially available in sheets. The main advantage and uniqueness
of this invention, comparing to other existing insoles, are the
evenly spaced holes throughout the insole. The holes will
significantly reduce the direct plantar pressure and shear stress
dynamically exerting on the plantar skin upon loading. When there
is a focal point of pressure, the holes will be distorted or
stretched to the direction of the pressure which will also allow
the insole material to distorted or "give" resulting in reduction
of the peak plantar pressure and the associated shear stress. This
will also eliminate any pressure transferring problems as
encountered in other insoles. Removing the pressure will allow the
insole material to return back to the original state. Therefore,
dynamic direct plantar pressure and shear stress can be
significantly reduced by these holes.
Inventors: |
Nguyen, Hienvu Chuc; (Elk
Grove, CA) |
Correspondence
Address: |
Hienvu Chuc Nguyen
3926 Oak Hurst Circle
Fair Oaks
CA
95628
US
|
Family ID: |
32912236 |
Appl. No.: |
10/762613 |
Filed: |
January 23, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60445589 |
Feb 5, 2003 |
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Current U.S.
Class: |
36/43 |
Current CPC
Class: |
A43B 13/187 20130101;
A43B 7/147 20130101; A43B 17/02 20130101 |
Class at
Publication: |
036/043 |
International
Class: |
A43B 013/38 |
Claims
1. What I claim as my invention is for evenly spaced holes drilled
or punched through/partially through all any composite layers and
throughout the diabetic healing shoe insole, or removable cast
walker insole, to reduce peak plantar foot pressure and shear
stress. The shape of the holes can be round, square, oval, hexagon,
octagon, or can have a smaller round/octagon diameter on one
surface and a larger round/octagon diameter on the opposite
surface. These holes, can be varied in sizes from {fraction
(1/16)}" to 1/2" to accommodate different weight loading
requirements, and are separated by at least 1/4" to 1" away from
each others and in a square, round, hexagon, octagon, or
alternating patterns. When there is a focal point of pressure, the
holes will be distorted or stretched to the direction of the
pressure which will also allow the insole material to distorted or
"give" resulting in reduction of the peak plantar pressure and the
associated shear stress. This will also eliminate any pressure
transferring problems as encountered in other insoles. Removing the
pressure will allow the insole material to return back to the
original state:
Description
BACKGROUND OF THE INVENTION
[0001] There are 16 million people or 5.9% of the population in the
United States that have diabetes. Many people first become aware
that they have diabetes when they develop one of its major
complications such as blindness, heart disease, stroke, peripheral
vascular disease, and numbness or neuropathy in the feet. High
blood sugar level also affects the body immune system and cause
delayed wound healing.
[0002] Diabetic foot complications are the most common cause of
non-traumatic lower extremity amputations in the United States. The
risk of lower extremity amputation is 15 to 46 times higher in
diabetics than in normal persons, and the majority of diabetic foot
complications begin with the formation of skin ulcers on the bottom
of the foot.
[0003] One of the main causes for diabetic ulceration is the
increase in plantar pressure on the bottom of the foot; especially,
the forefoot and the heel area. Foot deformities, which are common
in diabetic patients, lead to focal area of high pressure. When an
abnormal focus of pressure is coupled with lack of sensation, a
foot ulcer can develop. Therefore, off-loading plantar foot
pressure is an important component in treating diabetic foot
ulcerations.
DESCRIPTION OF PRIOR ART
[0004] There are many off-loading techniques and devices available,
each having specific applications according to the anatomic
location of the wound. Off-loading devices made for non-ambulatory
use include airflow mattresses, soft padding for the bed and
wheelchair, and heel protectors such as the multipodus boot that
suspends the limb to completely remove pressure from the problem
area.
[0005] For ambulatory patients with plantar foot ulcerations, the
ultimate off-loading device is a total contact cast, which acts to
transfer weight away from the foot and redistributes the forces of
weight bearing proximally onto the leg. A removable cast walker
device performs much of the same off-loading as a total contact
cast but is often more easily tolerated by the patient because it
is removable for bathing and for daily wound care. Other
off-loading but less ideal devices include a half-shoe (or
so-called "wedge shoe"), a postoperative/surgical shoe with soft
accommodative padding layer. A randomized clinical study was
conducted to compare the effectiveness of total-contact casts,
removable cast walkers, and half-shoes to heal neuropathic foot
ulcerations in individuals with diabetes. The study reports that a
significantly higher proportion of patients were healed in 12 weeks
in the total contact cast group when compared with the two other
modalities (89.5% vs. 65%, and 58.3%) (Off-loading the diabetic
foot wound: a randomized clinical trial, Diabetes Care 2001
November;24(11):2016)
[0006] U.S. Pat. No. 5,197,942 (Brady) describes wearable foot
orthoses with wound aperture to offload plantar pressure when a
patient walk. However, most diabetic patients with foot ulceration
have insensate foot and orthoses with hard material could create
additional plantar foot ulceration.
[0007] U.S. Pat. No. 5,329,705 (Grim) describes removing grids of
removable resilient hexagon elements in the insole to offload the
plantar foot pressure. However, this practice will subsequently
transferring peak plantar pressure to other part of the foot.
Furthermore, as the pressure is reduced through the aperture (from
removing the hexagon elements) it will put additional pressure
around the wound edge and subsequently creating more skin
undermining and calluses around the wound.
[0008] U.S. Pat. No. 5,483,757 (Frykberg) describes insole with
preferably multiple evenly spaced holes extends through for
breathing. These are limited number of small holes with the main
purpose for air circulation through the insole. These hole design
has no effective peak plantar pressure reduction.
[0009] U.S. Pat No. 5,797,862, and U.S. Pat. No. 6,083,185 (Lamont)
describes diabetic boot and insole consisting of an upper layer
plastazote and lower layer of poron material which laminated
together with additional metatarsal and scaphoid paddings to
offload foot pressure. This kind of material is commercially
available in sheets which can be cut out to fit into a shoe or
boot. However, it still does not have the offloading capabilities
such as the new invention (see testing below).
SUMMARY OF THE INVENTION
[0010] The main purpose of this invention is to develop a new
insole design which can significantly reduce the plantar pressure
under the forefoot and heel, and can be used as replacement insole
for the diabetic shoe, diabetic healing shoe, and removable cast
walker.
[0011] This new insole is consisting of shock absorbing and shear
reducing composite layers of Poron or soft EVA for the bottom
layer, Plastazote or cushioned polymer gel for the middle layer,
and a closed cell Neoprene top cover. These materials are
commercially available in sheets.
[0012] The main advantage and uniqueness of this invention,
comparing to other existing insoles, are the evenly spaced holes
throughout the insole. The holes will significantly reduce the
direct plantar pressure and shear stress dynamically exerting on
the plantar skin upon loading. When there is a focal point of
pressure, the holes will be distorted or stretched to the direction
of the pressure which will also allow the insole material to
distorted or "give" resulting in reduction of the peak plantar
pressure and the associated shear stress. This will also eliminate
any pressure transferring problems as encountered in other insoles.
Removing the pressure will allow the insole material to return back
to the original state.
[0013] Therefore, dynamic direct plantar pressure and shear stress
can be significantly reduced by these holes.
[0014] This insole can also be used to offload plantar pressure of
deformed foot which has bony prominences due plantar fat pads
atrophy in people with rheumatoid arthritis.
[0015] This new insole, when used in conjunction with a shoe or
with removable cast walker, will replace the total contact cast,
which is the ultimate off-loading device for treating diabetic foot
ulcerations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1. is top view of the right insole
[0017] FIG. 2. is a side elevation view of the right insole
[0018] FIG. 3. is a cross sectional view of the right insole, taken
along line A-A of FIG. 1
[0019] FIG. 4. is top view of the right insole, of interest area
"A", showing non-loaded insole
[0020] FIG. 5. is a top view of the right insole, of interest area
"A", showing a loaded insole with focal pressure point
[0021] FIG. 6. is a cross sectional view of the region of interest
"A" upon loading, taken along line B-B
DETAILED DESCRIPTION
[0022] This invention of the off-loading insole for diabetic
ulceration consists of a shock absorbing composite layers insole,
which also has additional capability to reduce the peak plantar
foot pressure and shear stress on the plantar skin by evenly spaced
holes through the insole. See FIGS. 1, 2, 3.
[0023] The insole main shape can be of a foot, existing shoe
insole, or the outline of a post surgical shoe or removable cast
walker.
[0024] The bottom layer material is soft EVA with a thickness of
1/4" to 1/2" which has excellent shock absorption, high direct
impact performance, and high resiliency.
[0025] The middle layer material can be either pink Plastazote, or
cushioned polymer gel with a thickness of 1/4" to 3/8" to mainly
absorb the direct plantar pressure and to reduce the shearing
stress.
[0026] The top layer material is closed cell Neoprene with a
thickness of 1/8" and is used as the top cover for the insole.
[0027] All three materials are glued together to form a composite
layered insole which is 1/2" to 1" thick. These materials are
commercially available. See FIG. 2.
[0028] Main shear stress reduction is accomplished by the middle
layer since it has the elastic property to "slide" or "give"
between the top and bottom layers when the direction of force is
parallel or near parallel to the insole surface.
[0029] Additional plantar pressure and shear stress reduction are
accomplished by evenly spaced holes drilled or punched through all
layers of the insole. These holes, can be varied in sizes and
shapes to accommodate different weight loading requirements, and
are separated by at least 1/4" to 1" away from each others.
[0030] FIG. 4 shows shape of the holes when in a relaxed or
non-loaded position.
[0031] FIGS. 5 and 6 show that when there is a focal point of
pressure, the holes will be distorted or stretched to the direction
of the pressure which will also allow the insole material to
distorted or "give" resulting in reduction of the peak plantar
pressure and the associated shear stress. Removing the pressure
will allow the insole material to return back to the original
state. Therefore, additional dynamic direct plantar pressure and
shear stress can be significantly reduced by these holes.
Test Results of the Peak Plantar Pressure of Various Insoles
[0032] We conducted a study to determine the plantar pressure under
the medial forefoot and under the heel using:
[0033] 1. Plain surgical shoe
[0034] 2. Laminated insole with 1/4" pink Plastazote and 1/8" PPT.
This is the normal insole material for diabetic shoe.
[0035] 3. Laminated insole with 1/4" soft EVA for the bottom layer,
1/4" pink Plastazote for the middle layer, and 1/8" Spenco for the
top layer. One has no hole and another one has {fraction (3/16)}"
holes drilled through all layers of the insole and are evenly
spaced at 1/2".
[0036] The plantar pressures were measured using the F-Scan in-shoe
pressure measurement system (TekScan, South Boston, Mass.). The
test was performed on a treadmill at a walking speed of 1.5 mph
with a female subject weights 135 lbs and wearing a surgical shoe
with and without the insoles above. Data were collected and
tabulated as follow:
1 Plain Surgical Shoe Pressure Pressure Under Medial Forefoot 15
psi (10.35 N/Cm2) Pressure Under Heel 20 psi (13.8 N/Cm2)
[0037]
2 Insole with PPT and pink Plastazote and surgical shoe Number 1
Insole Without Holes Pressure Under Medial Forefoot 14 psi (9.66
N/Cm2) Pressure Under Heel 18 psi (12.42 N/Cm2)
[0038]
3 Insole with 1/4" soft EVA for the bottom layer, 1/4" pink
Plastazote for the middle layer, and 1/8" Spenco for the top layer,
and surgical shoe Number 2 insole Without Holes With Holes Pressure
Under Medial 13 psi (8.98 N/Cm2) 10 psi (6.9 N/Cm2) Forefoot
Pressure Under Heel 17 psi (11.73 N/Cm2) 15 psi (10.35 N/Cm2)
[0039] As indicated in the tables above, the peak plantar pressure
was further reduced by using insoles with evenly spaced holes.
[0040] Similar study conducted by Lavery LA and cohorts in
"Reducing Dynamic Foot Pressures in High-risk Diabetic Subjects
With Foot Ulcerations" (Diabetes Care 19(8):818-821, 1996) reports
mean peak pressure for ulcers under the 1.sup.st metatarsal heads
(medial forefoot) for the Total Contact Cast, DH Pressure Relief
Walker (Royce Medical, Camarillo, Calif.), Aircast Pneumatic
Diabetic Walker (Aircast, Summit, N.J.), Extra Depth Shoe as
7N/Cm2, 8N/Cm2, 12.3N/Cm2, and 39.5N/Cm2 respectively.
[0041] Another study conducted by Armstrong D G and cohorts in
"Total Contact Casts and Removable Cast Walkers" (J Am Podiatric
Medical Association 89(1):50-53, 1999) reports peak plantar heel
pressure for the Total Contact Cast, DH Pressure Relief Walker
Aircast Pneumatic Diabetic Walker, and P W Minor Extra Depth Shoe
(PW Minor and Son, Batavia, N.Y.) as 18N/Cm2, 19N/Cm2, 20N/Cm2, and
25N/Cm2 respectively.
[0042] Comparing to the above studies for peak plantar pressure
under the medial forefoot and the plantar heel, there is not a
substantial difference between the new invention insole and the
Total Contact Cast, which is a gold standard for offloading
diabetic foot ulceration, to offload the medial forefoot (6.9N/Cm2
vs 7N/Cm2). However, the new insole is much better to offload the
plantar heel pressure (10.35N/Cm2 vs 18N/Cm2).
* * * * *