Note: Descriptions are shown in the official language in which they were submitted.
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LOAD RELIEVING WOUND DRESSING AND WOUND HEALING SYSTEM
CROSS-REFERENCES
This application claims priority from U.S. Serial No. 11/065,469 filed
February
24, 2005 and U.S. Serial No. 60/772,244 filed September 30, 2005, the
specifications of
which are incorporated herein in their entirety.
TECHNICAL FIELD
The present application is directed to an improved wound dressing which is
also a
part of a wound healing system, and more specifically to a multi-layered wound
dressing
for maximizing the pressure or load transferred from a wound site during load
bearing.
BACKGROUND
Mechanical off-loading is an essential factor in the healing of foot plantar
surface
ulcers. The medical condition of peripheral neuropathy in diabetic patients
leads to the
loss of sensation such that skin injury and complete brealcdown, resulting in
ulcers, can
develop with no or minimal pain. These wounds tend not to heal because of
ongoing
mechanical trauma not felt at all by the patient as painful. Such wounds can
only be
healed by treatment which includes protecting them from mechanical trauma.
Methods
for healing plantar ulcers include providing a total contact cast for the
foot, which
provides substantial mechanical protection. This method is not ideal for
application in the
health care practice settings of primary care practitioners and
endocrinologists, where
such wounds are normally treated, because it requires skilled and specialized
care in
application, along witll frequent follow up, and is time consuming to apply.
Also, patients
perceive the cast to be an inconvenience at the early stages of such a wound,
which is
often perceived by them as not a serious matter. An alternative healing method
is to ask
the patient to follow a non-weight bearing regimen through the use of a
wheelchair,
crutches, or a walker. Such complete mechanical protection is possible only
with full
patient compliance. This alternative rarely proves to be effective in healing
wounds
within a reasonable time period, because compliance is extremely poor. A still
further
alternative to unloading pressure from the wound is discussed in U.S. Patent
Nos.
6,610,897 and 6,720,470. While such wound healing systems provide an
improvement
over conventional cast and non-weight bearing methods, they are often
difficult for
medical personnel to properly form, fit and apply to a patient.
A new alternative has been developed which further reduces plantar foot
pressure
at a wound site, is convenient for application by medical personnel, and which
is accepted
by the patient.
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BRIEF SUMMARY OF THE INVENTION
An improved load-relieving dressing ("LRD") and improved foot bed have been
developed and have been shown to increase mechanical off-loading performance
by
reducing foot plantar surface pressure at the wound site during load bearing.
The dressing
and foot bed combination of the present application are simple for health care
practitioners to apply, easy for patients to use and create a more favorable
environment
for wound healing.
Improved Load Relieving Dressin~
Improved features of the load relieving dressing ("LRD") include dressing
geometry, incorporation of new off-loading materials, multiple material
layers, dressing
thickness and use of the dressing within an improved foot bed or other foot
gear which do
not require the provider to make custom modifications.
During development of the present LRD it was learned that dressing geometry,
or
the shape of the dressing, plays an important role in providing a contact area
for the
remainder of the patient's foot surface. The LRD of the present application is
shaped to
correspond approximately and substantially to the typical load bearing regions
of the foot
surface, for example in the forefoot. Concentration of pressure in these
regions is a
contributing risk factor for the development of foot ulcers in patients
diagnosed with
diabetic neuropathy. By tailoring the geometry of the LRD to match the foot
region of
interest, the present invention effectively maximizes the contact area
available to transfer
load away from the wound site and thereby reduce plantar pressure.
Different geometries of dressings may be provided for different areas or
regions of
the foot. Preferably dressings are provided for the metatarsal head region,
the heel region
and the hallux region, since these are the typical load bearing regions of the
foot plantar
surface and, subsequently, are at the greatest risk for development of foot
ulcers. A
wound opening, or off-loading aperture(s), may be provided in each dressing.
The
location and diameter of the wound opening(s) may be varied based upon the
presentation
of the wound or wound sites. The LRDs for each of the regions cover
essentially all of
the regional weight-bearing anatomy of the foot. For example, the LRD for the
metatarsal
head region is positioned under the forefoot and covers essentially all of the
load bearing
portion of the forefoot, except the wound site, to maximize distribution of
forefoot plantar
pressure.
Specifically, the geometry of the metatarsal head region has a configuration
which
is designed to engage, or substantially engage, the pressure distribution on
the foot during
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load bearing. In the design of the present application, the load relieving
dressing for the
metatarsal head region may be used on either the left forefoot or the right
forefoot, since
rotation of the dressing enables alignment of the dressing with the pressure
distribution
surface of either forefoot region. The heel and hallux region LRDs may also be
interchanged between the right foot and left foot. In the metatarsal head
region, the LRD
functions much like an insole and enables the patient to walk more normally
when worn
alone. In an alternate embodiment, the geometry of the metatarsal LRD may be
enlarged
to provide a more complete contact surface for the metatarsal heads.
Additionally, in
order to maintain the position of the LRD, further attachment mechanisms, such
as an
anchor strap may be provided.
In order to minimize plantar pressure increases in areas adjacent to or
surrounding
the wound during load bearing, the LRD of the present application includes
multiple
material layers. Each of the layers is of a material for accomplishing a
specific purpose.
Additionally, the thickness of each of the layers may be varied. A cushioning
layer is
provided which interfaces with the plantar surface of the foot. The cushioning
layer
serves to reduce and/or limit pressure increases at the periphery of the wound
opening or
off-loading aperture of the LRD and in the immediate area of the LRD adjacent
to the
wound site, and also to limit shear forces at the LRD-skin interface. In the
non-load
bearing condition, the cushioning layer at the -periphery of the wound opening
may have a
substantially square edge portion, which eases under pressure. In the event
the material
selected for the cushioning layer does not ease under pressure, contouring of
the edge
portion at the periphery of the wound opening may be needed.
An off-loading layer is provided which is secured to the cushioning layer on a
surface away from the foot. The off-loading layer is of a thickness and
firmness sufficient
to maximize plantar pressure reduction at and around the wound site.
A conforming layer may also be provided which is secured to the off-loading
layer
at the surface opposite from the cushioning layer. The conforming layer serves
as a
flexible interface between the off-loading layer and the contact surface
engaged by the
foot and dressing combination, such as the floor, a foot bed, or other foot
gear, etc. The
additional flexibility resulting from use of the conforming layer provides
greater comfort
to the foot surface with which the LRD is engaged, as well as additional off-
loading of
plantar pressure at and around the wound site.
Optionally, an adhesive layer and/or other attachment means, as mentioned
above,
may be provided on the surface of the cushioning layer for securing engagement
with the
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foot. A peel-off double sided tape or other medically appropriate adhesive may
be used to
enable convenient application by the patient or medical personnel.
Alternatively, a wrap
having Velcro, straps or other conventional attachment mechanisms may be used
to
secure the LRD in position.
, As mentioned above, the thickness of each of the cushioning, off-loading and
conforming layers may also be varied. Generally, greater pressure reduction at
the wound
site is obtained by increasing dressing thickness. The LRD should be of a
sufficient
overall thickness to provide for substantial off-loading of the wound site
during walking,
without causing a patient to significantly alter their normal gait pattein.
Thus, the ideal
thiclcness enables a patient to maintain a steady gait during walking, while
allowing
maximum off-loading of pressure from the wound site with minimal pressure gain
across
the surface area of the LRD.
Other features and advantages of the LRD of the present application include
the
ability of the dressing to accommodate the delivery of adjunct wound therapies
to
promote healing. For example, an occlusive meinbrane may be used between the
layers
of the LRD to create a "well" in connection with the wound opening. Various
wound
healing therapies, such as antibiotics, antimicrobials, growth factors and
cell based
therapies, and exudate absorbants, may be delivered to the wound via placement
within
the well. Alternatively, the membrane layer may be comprised of a wound
contact
material attached to the cushioning layer of the LRD over the aperture to
provide support
to the skin surrounding the wound and prevent protrusion of the skin surface
into the
aperture area. In a preferred embodiment, the membrane layer is transparent
and porous,
allowing drainage of the wound to pass through to an absorbing agent, if
desired.
Improved Foot Bed
Additionally, an improved foot bed of the present application, or commercially
,available foot gear having foot beds, may also be used in conjunction with
the LRD of the
present application. The improved foot bed design includes multiple layers of
materials
of sufficient thickness to allow the LRD to automatically conform or mold into
the foot
bed, while also providing firm support for that portion of the foot plantar
surface which is
not engaged with the LRD. The foot bed further serves to maintain the LRD
properly
positioned on the foot, and reduces potential shifting of the LRD with respect
to the
wound site.
The layers of the improved foot bed may include: a top layer for engagement
with
the LRD; a middle layer having a "landing zone" portion which preferably
employs a
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visco-elastic material to automatically conform or mold around the LRD as it
is pressed
under load into the landing zone, and has a thickness at least as thick as the
LRD, and
may also include a support zone portion of a somewhat firmer material; and a
bottom
layer to provide a rigid surface for supporting the foot bed. In the middle
layer, the
landing zone portion would be provided substantially in the area of the foot
where the
wound is present, with the support zone being provided in the other areas of
the foot.
Alternatively, the improved foot bed may be provided without a top layer. In a
preferred
embodiment, the visco-elastic material of the landing zone of the middle layer
minimizes
potential shifting of the LRD by conforming or molding around the LRD
geometry.
The improved foot bed geometry or external shape is adapted for engagement
with
the desired foot gear. The coinbination of the improved LRD with the improved
foot bed,
preferably used within appropriate foot gear, provides an improved wound
healing system
for significant plantar pressure reduction at the wound site.
Other features and advantages will become apparent from the following detailed
description and from the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. l illustrates a perspective view of one of the embodiments of the
improved
LRD of the present application.
Fig. 2a-2b illustrates a sample of the pressure distributions on the various
regions
of a foot during load bearing, such as walking.
Figs. 3a-3c illustrate schematic perspective views of the improved LRD of the
present application for the metatarsal head region, heel region and hallux
region,
respectively.
Figs. 4a-4c illustrate side views of the improved LRD having various
thicknesses
in various layers.
Figs. 5a-5d illustrate the surface of the improved LRD for engagement with a
foot
having an adhesive layer; in 5a-5b with a covered wound opening and in 5c-5d
with an
open wound opening.
Fig. 6 illustrates a partial perspective view of a wound opening having a
membrane layer formed between layers of the LRD, and forming a well having
exudate
absorbing material supported therein.
Figs. 7a-7c illustrate bottom, side and wrapped views of a foot of a patient
supporting a LRD of the present application.
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Figs. 8a-8d illustrate perspective views of various embodiments of the
improved
foot bed of the present application.
Figs. 9a-9c illustrate use of the improved foot bed with the improved LRD,
where
Fig. 9a shows the approximate position of the improved LRD with respect to the
foot bed
during use, Fig. 9b shows use of an improved foot bed engaged with the
improved LRD a
wrapped foot of a patient and the landing zone portion conforms to the LRD,
and Fig. 9c
shows the memory characteristic of the material used in the landing zone
portion of the
LRD.
Figs. l0a-lOb show the wound healing system with the improved LRD and
improved foot bed on a foot of a patient within conventional foot gear.
Figs. 11 a and 1 lb illustrate use of the improved LRD of the present
application
used with one embodiment of a commercially available insole.
Figs. 12a and 12b illustrate use of the iinproved LRD used with another
embodiment of a commercially available insole.
Fig. 13 illustrates an alternate embodiment of the improved LRD showing the
top
cushioning layer having an asymmetrical configuration.
Fig. 14 illustrates a side view of the improved LRD having a contoured surface
in
the conforming layer.
Fig. 15 illustrates a perspective view of the wound opening of the improved
LRD
having a rounded aperture edge.
Fig. 16 illustrates a perspective view of an alternate embodiment of the
improved
LRD having an attachment mechanism in the fonn of an anchor strap for securing
the
LRD to the foot.
Fig. 17 illustrates the improved LRD having the anchor strap.
Fig. 18 illustrates a partial, sectional view of the improved LRD having a
membrane layer secured over the rounded aperture wound opening.
Fig. 19 illustrates a top view of the improved LRD of Fig. 16 with the peel-
off
adhesive backing removed and ready for application.
Fig. 20a illustrates a bottom view of the improved LRD of Figs. 16, 19.
Fig. 20b illustrates the improved LRD of Fig. 20a secured to a foot.
Fig. 21 illustrates a four material foot bed of the present invention.
Fig. 22 illustrates foot gear for use in connection with the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
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The load-relieving dressing and foot bed described here have been shown to
provide mechanical off-loading by reducing foot plantar surface pressure at
the wound
site during load bearing. The LRD and foot bed combination are simple for
health care
practitioners to apply, easy for patients to use and create a more favorable
environment
for wound healing.
Load Relieving Dressing
Referring now to Fig. 1, a load relieving dressing 10 or "LRD" of the present
application is shown. The LRD of the present application is provided with an
external
dressing geometry which is shaped to correspond approximately and
substantially to the
typical load bearing regions of the foot. Figures 2a and 2b demonstrate
barefoot pressure
distributions, with higher plantar pressures being measured in the highlighted
regions
indicated at H. Obviously, plantar pressures within the load bearing regions
of the foot
may vary greatly. In Fig. 2a, the highlighted areas of increased pressure
during load
bearing include areas of the forefoot, for example, the metatarsal head and
hallux regions,
as well as the heel area. While in Fig. 2b, measurements of the midfoot area
illustrate
areas of increased pressure.
The external geometry of the LRD of the present application preferably covers
essentially the increased pressure or weight-bearing anatomy of the foot by
region. Thus,
in Fig. 3a, the LRD has a substantially lobular configuration for engagement
with the
pressure distribution in the metatarsal head region of the forefoot, which is
substantially
symmetrical. In Fig. 3b, an LRD having an external geometry for use with the
pressure
distribution in the heel region is illustrated having an ovoid configuration.
In Fig. 3c, an
LRD having an external geometry for use with pressure distribution in the
hallux region is
illustrated as ovoid. Still f-urther in Fig. 13, an LRD having an external
geometry
covering the entire metatarsal region is provided. This lobular shape further
extended in
the lateral direction to better engage and support the lateral metatarsal
heads, and is
substantially asymmetrical in its external geometric shape.
The LRD includes a wound opening 12 or off-loading aperture through the LRD
for surrounding a wound site, the location and diameter of which aperture is
varied based
upon the presentation of the wound or wound sites. The wound opening may be
formed
by conventional stamping methods and may be provided in single or multiple
standard
locations, such as central, right and/or left locations. When the opening of
the LRD is
forined or modified by a health care practitioner specifically for a patient,
the preferred
method of formation or modification is by appropriate cutting instruments such
as a
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scalpel or scissors. In the illustrated embodiments, the LRD has a circular
configuration
with aii approximately one inch (25 mm) diameter aperture which extends
through all
three material layers. It should be understood that wound opening may be
provided in
other, non-circular shapes and appropriate sizes to further assist with wound
healing. The
aperture serves to offload the area around the ulcer. Additionally, a rounded
edge
surrounding the aperture, as in Fig. 15, is also provided to allow for a
smooth pressure
transition from the supportive top cushioning layer to the offloading
aperture. This
relieves the stress concentration at the aperture edge without exposing the
harder layers of
other LRD materials, such as EVA. The rounded aperture edge is essentially a
constant
radius cut of 5 mm.
The load relieving dressings of the present application may also be
interchangeable between feet and may be used on either the left foot or the
right foot,
since rotation of the dressing enables alignment of the dressing with the
pressure
distribution surface of either foot and/or the wound location. Additionally,
the LRD 10 of
the present application is preferably of multiple material layers of foam
material, where
certain of the layers are of off-loading or load relieving foams. It is
preferred that the
LRD have an overall thickness in the range of approximately 3 to 25 mm of foam
material, with the layers of material laininated together. The preferred
thiclrness of the
LRD enables a patient to maintain a steady gait during walking, while allowing
maxiinum
off-loading of pressure from the wound site during load bearing.
A first layer 14 of the LRD is for interfacing with the plantar surface of the
foot,
and cushioning the foot, particularly at the periphery of the wound opening,
during load
bearing. The first cushioning layer 14 is preferably of a material sufficient
to limit
pressure increases at the wound opening and within the dressing at the wound
opening,
such as a polyurethane foam material, for example, soft, supporting Poron
material.
Other available shear reducing gel materials such as a fabric coated shear
reducing gel,
Wonderflex silicone gel, from Silipos, may also be used to provide improved
comfort,
since the silicone layer reduces shear forces at the skin/LRD interface to
effectively
reduce discomfort and irritation which may be perceived by the subject. The
cushioning
layer 14 has a durometer of between 5-30 Shore A hardness. The thickness of
the
cushioning layer 14 is between 0-12 mm, and more preferably a range of about 3-
4 mm.
A second off-loading layer or load relieving layer 16 is engaged with the
first
cushioning layer 14 of material. The off-loading layer 16 is sufficiently
thick and firm to
reduce plantar pressure at and around the wound site. The firmer material
preferably used
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for the off-loading material layer is an ethylene vinyl acetate foam material.
The off-
loading layer 16 has a duroineter of between 15-60 Shore A hardness. The
thickness of
the off-loading layer 16 is between 0 to 12 mm. Materials such as Microcel
PuffRO EVA
from Acor Orthopaedic, Inc. or Cloud EVA from JMS Plastics Supply, Inc., which
are
slightly finner than otller layers, may be used to keep the ulcer area from
bottoming out.
As illustrated in Fig. 3a, the LRD may be provided with only a cushioning
layer 14 and an
off-loading layer 16.
An optional third conforming layer 18 is engaged with the off-loading layer
16.
The inclusion of a third conforming layer provides several unexpected
benefits. A third
layer allows reduction in the thickness of the off-loading layer 16, because
the
conforming layer 18 also provides pressure off-loading at the wound site. As a
result, the
LRD provides comparable pressure off-loading, but is more flexible, so it
better conforms
to the plantar aspect of the foot. The conforming layer is of a material
sufficient to
provide a flexible interface with a contact surface, such as the floor, a foot
bed, or other
foot gear, etc., being engaged by the foot during load bearing or walking, and
thus
provides better traction during walking. The material of the confonning layer
18 is
sufficient to conform to a foot surface during load bearing conditions for
providing
additional off-loading of pressure from the wound during load bearing. The
confonning
layer reduces impact stresses during load bearing, and retains or regains its
dimensional
properties under non-load bearing conditions, meaning it rebounds to its
original shape
regardless of the number of weight-bearing cycles that are applied. In the
illustrated
embodiment of Figs. 14 and 20a, the underside contoured portion or edge 200 of
the
conforming layer of the LRD has an elliptical quadrant Q of approximately 10-
14 mm by
3-20 mm, and more specifically 12.7 mm by 15 mm. This contour provides a more
streamlined fit when the LRD is pressed into the memory foam or other material
of the
footbed. Materials to be used for the conforming layer include polyurethane
foam
materials having a durometer of 5-30 Shore A hardness, and a thickness of 0 to
12 mm.
In a preferred embodiment, visco-elastic materials are used to improve the
overall
flexibility of the LRD, for example, slow recovery, very firm, Poron , and to
increase
traction during walking due to its deformation under load bearing conditions.
As shown in Fig. 4a, 4b and 4c, the thicknesses of individual layers may be
varied
to obtain the desired configuration of maximum pressure reduction for a
particular
patient. The preferred optimal thicknesses illustrated in Fig. 4a are, for
example, are:
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cushioning layer 14: approximately 3mm, off-loading layer 16: approximately
6mm and
conforming layer 18: approximately 3mm.
A further optional adhesive layer or layers 20 may also be provided on the
surface
of the cushioning layer for securing engagement of the LRD with the foot. A
peel-off
double sided tape or other medically appropriate adhesive, such as DuoDerm ,
Tegasorb R, A1levynOO, or other adhesives by ConvaTec, for example, may all be
used. In
Figs. 5a and 5e, an LRD is illustrated prior to removal of the peel-off
adhesive backing
22.. Fig. 5b illustrates the LRD with the peel-off backing removed, but with a
portion 24
of the adhesive remaining covering the wound opening 24. Such an application
may be
desired where the adhesive layer applied to the skin over the wound is an
exudate
absorbent, such as Versiva by ConvaTec. In Figs. 5c and 5d, the illustrated
LRD has an
adhesive layer 20 which also includes a wound opening 12 therethrough. Figs.
7a and 7b
illustrate the LRD applied to a patient's foot using an adhesive layer, and
with the wound
opening 12 aligned over the wound W. In Fig. 7c, the LRD is further secured to
the foot
using a self-adhering wrap or other bandage, however, it is understood that
other
attachment mechanisms may also be used.
In the Fig. 6 LRD illustrated, an occlusive membrane layer 26 is provided
between
the cushioning layer 14 and off-loading layer 16. As shown in Fig. 6, a
"well"or cavity
28 is formed within the wound opening and membrane layer 26 to support a
desired
wound healing therapy. In the Fig. 6 embodiment, Aquacel wound dressing by
ConvaTec is provided within the we1128. A variety of therapies may be placed
within the
well for delivery to the wound, such as antibiotics, antimicrobials, growth
factors and cell
based therapies, and other exudate absorbants. This may be accomplished either
by
incorporation of a membrane layer in the dressing 10 or by custom packing of
the LRD
wound aperture 12 by the healthcare practitioner.
An additional alternative embodiment of the membrane layer 26' may also be
provided as in Figs. 17-19. In this embodiment, the membrane layer 26' is a
section of
wound contact material, such as TegaporeOO, available from 3M, which is
specifically
designed to contact open wounds and allow drainage from the wound to pass
through to
an absorbing agent, if desired. This membrane layer 26' is strong enough to
support the
slcin surrounding the wound, and while engaging the skin does not apply a
significant
amount of pressure to the wound. Such wound contact material is also
transparent, which
enables visibility of the wound during and after application of the LRD. In
the Fig. 18
embodiment, the membrane layer 26' is approximately a 50 mm diameter, circular
section
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which is adhered securely between top cushioning layer 14, and an additional
attachment
mechanism in the form of a strap, or dorsal anchor strap 202.
As shown in Figs.17, 19 and 20a, the anchor strap 202 provides an extension of
the slcin adhesive layer 20 which extends beyond the boundary of the LRD 10
cushioning
layer 14 in both the medial and lateral directions. The LRD 10 is adhered to
the dorsal
anchor strap 202 which wraps around the sides of the foot and includes an
adhesive for
attachment to the dorsal surface D as in Fig. 20b. The strap is preferably a
woven nylon
fabric material which is laminated with the acrylic slcin adhesive forming the
adhesive
layer 20. The use of an attachment mechanism such as the anchor strap 202
provides
more contact area for adhesion to maintain the LRD 10 in place. As further
illustrated in
Fig. 19, an additional adhesive layer 20' on the anchor strap provides
improved adhesion
to secure the LRD to the planter surface of the foot. In the preferred
einbodiment the
adhesive layer 20' is a DuoDERM CGF adhesive product by ConvaTec. As best
shown
in Fig. 16, a top portion of the adhesive layer 20' is in contact with the
skin (once the
release liner is removed) and an opposite surface is adhered to the anchor
strap 202
underneath.
Manufacture of the LRD of the present application includes the steps of
laminating the desired foam material layers in the desired order to achieve
the preferred
thiclcness. Preferred lamination adhesives include all purpose cements such as
Duall-888,
from RH Products, Inc., for example. Next the foam layers may be machined to
the
desired external geometry and to form the wound opening 12 as previously
described.
A layer or layers of adhesive materia120, 20' or other attachment mechanisms
for
securing the LRD to the foot may next be applied. Finally, any desired wound
healing
therapies may be incorporated into the dressing.
Foot Bed and Wound Healing System
Figures 8a to 8d and 21 illustrate an improved foot bed of the present
application.
While the use of the LRD alone is intended and provides increased wound
healing, typical
wound healing practices generally include a protective insole and related foot
gear.
However, the effectiveness of such foot gear is dependent upon patient
compliance during
heightened risk for injury to the wound site. In the present application, the
preferred
embodiment of the improved LRD is provided for use in an iinproved foot bed.
In the improved foot bed 30 of the present application, a material layer is
provided
which has sufficient thickness to allow the LRD to automatically conform or
mold into
the foot bed. A material layer providing firm support for the foot plantar
surface not
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engaged with the LRD may also be provided. The foot bed of the present
application
maintains the LRD properly positioned on the foot, and reduces shifting of the
LRD with
respect to the wound site as shown in Fig. 9b. The external geometry of the
foot bed is
configured for engagement within any desired outer foot gear.
In the preferred embodiments of the present application, three or four
material
layers are provided. In the three layer embodiments of Fig. 8a: a top layer 32
is provided
for engagement with the LRD 10 (as shown in Fig. 9a) which is manufactured of
polyurethane material or PPT and of a tliickness of approximately 1 mm to 6
mm, and
preferably the top layer of the foot bed is 1.5 mm of supporting cellular
urethane such as
PoronO from Rogers Corp., which adds cushion and aids in shock absorption;
a middle layer 34 having a "landing zone" portion 36 which is generally in the
forefoot region of the foot bed, preferably employs a visco-elastic material,
available from
suppliers of Tempur-pedic0 or Tempur-MedO products, or visco-elastic
polyurethane
products such as Visco-CEL V0575, available from Rubberlite Inc., to
automatically
conform or mold around the LRD 10 as the LRD is pressed under load into the
landing
zone within the forefoot region, as well as support the rest of the foot. It
is desired that
the landing zone of the middle layer be of a material which may be compressed
to a
thickness'enabling the surface of the foot on which the LRD is secured to be
approximately level with the surface of the foot bed. Thus, the LRD and foot
bed provide
a surface which enables a normal walking gait, and which supports the foot
equally in
load bearing and non-loading sections. The middle layer has a thickness
approximately at
least as thick as the LRD, or between 10 mm and 30 mm, and more preferably
approximately 19 to 20 min; and
a bottom layer 38 of a more rigid material, for example, ethylene vinyl
acetate
("EVA") material, to provide a rigid and durable surface for supporting the
foot bed 30,
and of a thicl:ness of approximately 1 mm to 6 mm. Thus, the overall thickness
of the
foot bed may range from 12mm to 42 mm, and preferably approximately 30 mm.
In the four material embodiment of Figs. 8b, 8c and 8d and 21, an additional
support zone portion or heel portion 40 of a somewhat firmer material such as
EVA, an
extra firm memory foam, like Plastizote, or combinations of EVA and visco-
elastic
material, may also be provided as a portion of the middle layer 34. The
landing zone
portion 34 would be provided in the area of the foot where the wound is
present, with the
support zone supporting other areas of the foot not engaged with the LRD 10,
as shown in
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CA 02598810 2007-08-23
WO 2006/091735 PCT/US2006/006445
Figs. 8b, 8d. The use of such materials in the support zone portion 40
provides better heel
support and a self-conforming heel cup over time.
As shown in Fig. 9c, the top layer 32 and landing zone 36 of the middle layer
34,
conform to or mold around the LRD 10. As shown, the combination of the LRD 10
within the foot bed 30 serves to relieve pressure or off-load the wound W
during load
bearing, which can be seen by the indentation I formed in the foot bed 30 by
the LRD and
the relief section R where the wound opening 12 is located within the LRD
adjacent the
wound. Manufacture of the improved foot bed of the present application
includes the
steps of laininating the desired material layers in the desired order to
achieve the preferred
thickness and characteristics. Alternatively, layers of materials may be co-
extruded or cut
and glued together to form the desired patterns within the middle layer 34.
The improved LRD 10 of the present application may also be used with numerous
conventional foot beds. As shown in Figs. 11, the LRD 10 is used with a Don
Joy foot
bed 30' having two layers of material. In Fig. 12, the LRD 10 is shown engaged
within a
Royce Medical insole 30", with the hexagonal plugs 31 of the insole removed to
accommodate the external geometry of the LRD 10. Additionally, where
commercially
available one layer foot beds are used, thermoformed materials such as
Plastizote (not
illustrated) may be used with the present LRD 10.
The improved foot bed 30, LRD 10 and foot gear 44 combination, or the wound
healing system 42 of this application, are shown in Figs. 10a, lOb, 21 and 22.
The
combination of the improved LRD 10 with the improved foot bed 30, preferably
used
within appropriate foot gear 44 provides an improved wound healing system 42
for
significant plantar pressure reduction at the wound site. Fig. 22 illustrates
a wound care
shoe which is available from Darco, for off-loading the area of the foot being
treated.
Foot gear of this type provides the necessary depth to securely house the foot
bed 30.
There is also sufficient padding on the inside of the shoe to protect the
patient's foot. The
use of such a shoe, coinpared to other conventional, but more cumbersome
walker/boot
foot gear, adds a level of comfort and freedom that assists with increasing
patient
compliance. Such foot gear may include a rocker outsole for forefoot pressure
relief.
While embodiments of the invention have been described in detail herein, those
skilled in the art will appreciate that various modifications and alternatives
could be
developed in light of the overall teachings of the disclosure. Thus, these
arrangements are
illustrative only and not intended to limit the scope of the invention which
is to be given
the full breadth of any and all equivalents.
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