WO2006091735A2

WO2006091735A2 - Load relieving wound dressing and wound healing system

Info

Publication number: WO2006091735A2
Application number: PCT/US2006/006445
Authority: WO
Inventors: Anthony John Henderson; Timothy B. Hurley; Jan S. Ulbrecht
Original assignee: Diapedia, L.L.C.
Priority date: 2005-02-24
Filing date: 2006-02-24
Publication date: 2006-08-31
Also published as: WO2006091735A3; JP2008531130A; CA2598810A1; EP1850819A2

Abstract

An improved load relieving dressing for transferring pressure away from a wound on a foot of a patient. The dressing having a wound opening (12) formed through the dressing for surrounding a wound site. The dressing having an external shape which substantially conforms to the shape of the pressure distribution on the foot during load bearing. A first layer (14) of the dressing interfacing with and cushioning a foot during load bearing. The first layer is of a material sufficient to limit pressure increases at the wound opening and within said dressing adjacent the wound opening. An off-loading layer (16) is engaged with said first layer, and is of a material sufficiently thick and firm to reduce pressure at the wound site.

Description

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 breakdown, 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 with 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. 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 Dressing

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 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 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 pattern. Thus, the ideal thickness 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 membrane 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 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 LRX), 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 combination 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. 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. 10a- 10b show the wound healing system with the improved LRD and improved foot bed on a foot of a patient within conventional foot gear.

Figs. 1 Ia and 1 Ib 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 improved 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 foπn 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 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,

'In. 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. 3 a, 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. 3 c, an LRD having an external geometry for use with pressure distribution in the hallux region is illustrated as ovoid. Still further 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 formed 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 scalpel or scissors. In the illustrated embodiments, the LRD has a circular configuration with an 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 laminated together. The preferred thickness of the LRD enables a patient to maintain a steady gait during walking, while allowing maximum 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 for the off-loading material layer is an ethylene vinyl acetate foam material. The offloading layer 16 has a durometer 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 Puff® EVA from Acor Orthopaedic, Inc. or Cloud EVA from JMS Plastics Supply, Inc., which are slightly firmer than other layers, may be used to keep the ulcer area from bottoming out. As illustrated in Fig. 3 a, 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 conforming 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 confoπning 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: 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®, Allevyn®, or other adhesives by ConvaTec, for example, may all be used. In Figs. 5 a and 5 c, 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. hi 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 well 28. 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 Tegapore®, 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 skin 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 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 skin 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 skin 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 embodiment 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 thickness. 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 material 20, 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 improved 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 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 thickness 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 Poron® 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-pedic® or Tempur-Med® 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 mm; 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 thickness 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 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 laminating 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, 10b, 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, compared 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.

Claims

CLAIMS We claim:

1. A load relieving dressing for transferring pressure away from a wound on a foot of a patient comprising: a wound opening formed through said dressing for surrounding a wound site; a first layer of said dressing for interfacing with and cushioning a foot during load bearing, said first layer of a material sufficient to limit pressure increases at said wound opening and within said dressing adjacent said wound opening; an off-loading layer engaged with said first layer of a material sufficiently thick and firm to reduce pressure at a wound site; a conforming layer engaged with said off-loading layer and of a material sufficient to provide a flexible interface with a contact surface being engaged by a foot during load bearing, said material sufficient to conform to a foot surface during load bearing conditions, provide additional off-loading of pressure from a wound during load bearing, reduce impact stresses during load bearing, and to retain dimensional properties under non-load bearing conditions.

2. A load relieving dressing for transferring pressure away from a wound on a foot of a patient comprising: a wound opening formed through said dressing for surrounding a wound site; a first layer of said dressing for interfacing with and cushioning a foot during load bearing, said first layer of a material sufficient to limit pressure increases at said wound opening and within said dressing adjacent said wound opening; and an off-loading layer engaged with said first layer of a material sufficiently thick and firm to reduce pressure at a wound site.

3. The load relieving dressing of Claims 1 or 2, wherein said first layer further supports an attachment mechanism positioned intermediate said first layer and a foot of a patient for securing said load relieving dressing to a foot.

4. The load relieving dressing of Claims 1 or 2, wherein said dressing has a geometry shaped substantially to the pressure distribution on a foot of a patient during load bearing.

5. The load relieving dressing of Claim 4, wherein said wound opening may be positioned through any portion of said dressing for appropriately surrounding a wound site.

6. The load relieving dressing of Claims 1 or 2, wherein said dressing has a lobular geometry.

7. The load relieving dressing of Claims 1 or 2, wherein said dressing has a geometry which is substantially ovoid in configuration.

8. The load relieving dressing of Claim 5, further comprising a membrane layer positioned intermediate two adjacent layers of said dressing, said membrane layer supporting wound healing therapy materials at a location adjacent a wound for promoting wound healing.

9. The load relieving dressing of Claims 5 or 8, further comprising a membrane layer positioned over the wound opening of said dressing, said membrane layer providing support to the skin surface surrounding a wound.

10. The load relieving dressing of Claim 3, wherein said attachment mechanism comprises one or more adhesive layers.

11. The load relieving dressing of Claim 3, wherein said attachment mechanism comprises a strap for surrounding a foot of a patient.

12. A load relieving dressing for transferring pressure away from a wound on a foot of a patient comprising: a wound opening formed through said dressing for surrounding a wound site; said dressing substantially engaging a surface of a foot of a patient which supports a pressure distribution of a foot of a patient during load bearing; said dressing having a shape which substantially conforms to the shape of the pressure distribution on the foot during such load bearing; and said wound opening may be positioned anywhere within said dressing for appropriately surrounding a wound site.

13. A wound healing system for healing a wound on a toot ot a patient comprising: a load relieving dressing to be attached to an area about the wound of the foot, whereby said load relieving dressing provides support to the foot in said area and relieves load on the wound and includes a wound opening surrounding the wound; and a foot bed for engagement with a foot of a patient having said load relieving dressing, said foot bed having a base portion and a landing zone portion, said landing zone portion for engagement with said load relieving dressing, and having a thickness which is approximately equal to or greater than the thickness of the load relieving dressing, and of a material sufficiently compressible to fully conform to said load relieving dressing during load bearing, said base portion supporting said landing zone portion and providing a rigid base for supporting a patient during load bearing.

14. The wound healing system of Claim 13, wherein said foot bed is engaged within foot gear worn by a patient.

15. The wound healing system of Claim 13 , wherein said landing zone portion of said foot bed is positioned substantially within a metatarsal head region of a foot of a patient, said landing zone portion positioned adjacent a support zone portion secured to said landing zone portion and located on proximal and/or distal ends of said landing zone portion, said support zone portion of a firm material for supporting portions of the foot not engaged with said load relieving dressing, and said base portion supporting said landing zone portion and support zone portion.

16. An improved foot bed for transferring pressure away from a wound on a foot of a patient comprising: a base portion having a planer surface adapted to be under a foot and of a sufficiently rigid material for supporting said foot bed within appropriate foot gear or for engagement with the floor during load bearing by a patient; said base portion supporting a landing zone portion thereon, said landing zone portion for engagement with a load relieving dressing engaged on a foot of a patient, and having a thickness which is approximately equal to or greater than the thickness of the load relieving dressing, and of a material sufficiently compressible to fully conform to said load relieving dressing during load bearing; and said base portion supporting a support zone portion positioned to surround said landing zone portion for supporting portions of a foot of a patient which are not engaged with a load relieving dressing.

17. The improved foot bed of claim 16, wherein the landing zone portion is of a visco- elastic foam material.

18. A load relieving dressing for transferring pressure away from a wound on a foot of a patient comprising: a wound opening formed through said dressing for surrounding a wound site; said dressing substantially engaging a surface of a foot of a patient which supports a pressure distribution of a foot of a patient during load bearing; said dressing having an external shape which substantially conforms to the shape of the pressure distribution on the foot during such load bearing; said dressing having a first layer for interfacing with and cushioning a foot during load bearing, said first layer of a material sufficient to limit pressure increases at said wound opening and within said dressing adjacent said wound opening; and said dressing having a base layer of material sufficiently thick and firm to reduce pressure at a wound site and to provide a flexible interface with a contact surface being engaged by a foot during load bearing, said base layer conforming to a foot surface during load bearing conditions, providing additional off-loading of pressure from a wound during load bearing, reducing impact stresses during load bearing, and retaining dimensional properties under non-load bearing conditions.

19. The load relieving dressing of Claim 18, wherein said first layer further supports one or more adhesive layers positioned intermediate said first layer and a foot of a patient for securing said load relieving dressing to a foot.

20. The load relieving dressing of Claim 18, wherein said dressing is interchangeable and may be used on either a right foot of a patient or a left foot of a patient.

21. The load relieving dressing of Claim 18, wherein said dressing has a lobular geometry.

22. The load relieving dressing of Claim 18, wherein said dressing has a geometry which is substantially ovoid in configuration.

23. The load relieving dressing of Claim 18, further comprising a membrane layer positioned intermediate two adjacent layers of said dressing, said membrane layer supporting wound healing therapy materials at a location adjacent a wound for promoting wound healing.

24. The load relieving dressing of Claim 18 or 22, further comprising a membrane layer positioned over said wound opening of said dressing, said membrane supporting the skin surface surrounding a wound.