Abstract:
An orthopedic walking boot promotes rapid healing of diabetic foot ulcerations by lowering the maximum peak pressure imposed upon the foot. The walker has a hard unyielding shell which is designed for walking. The shell closely and rigidly supports a mid-sole in a foot-shaped bed. The mid-sole has a foot-shaped cavity with rounded sides adapted to form resilient support for the heel, arch and sides of a foot in addition to the bottom of a foot. A conformable inner-sole is adapted to fit over the foot-shaped cavity in the mid-sole and be compressed in response to foot pressure between the sides and bottom of the foot and the sides and bottom of the foot-shaped cavity in the mid-sole thereby compensating for small differences between the shape of the foot and the shape of the cavity. Weight applied to the foot is transferred to the walking shell by contact between the sides of the foot, arch, and heel and the arch, heel and sides of the foot-shaped cavity as well as the bottom of the cavity thereby decreasing the peak or maximum unit pressure on the plantar surface of the foot. A breathable bootie which wraps the foot and lower leg in a protective “cocoon” is preferably secured to the upper surface of the insole thereby preventing foreign materials from entering the foot cavity.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to orthopedic devices, and more particularly to an orthotic support for assisting in the stabilization and proper healing of ulcerative or pre-ulcerative conditions, plantar fasciitis or other conditions of the foot, especially for diabetic patients.  
           [0003]    2. Background of the Invention  
           [0004]    The present invention relates to orthotic or orthopedic devices that are used to immobilize, support and brace the foot and ankle. The sole or plantar surface of the foot is often subject to conditions or injuries, such as stone bruises, heel spurs, soft tissue injuries or injuries of the muscles, ligaments, bones or joints. Foot problems of this kind are often painful and exacerbated by the patient&#39;s need to walk during the healing process. The degree of immobilization and protection required varies with the severity and difficulty of the condition. Relief may sometimes be obtained by use of a molded inner-sole or orthotic pieces in a regular shoe to add stiffness or alter the pressure distribution on the foot. Another option is custom made shoes which, although expensive, may provide relief for minor conditions. These may be augmented with the use of ankle braces or crutches but provide little relief for more serious conditions.  
           [0005]    Diabetics are subject to especially severe and difficult foot problems. As the condition of diabetes gets worse, these patients begin to develop a problem called neuropathy, or polyneuropathy where they lose the sense of feeling in the plantar surface or bottom of the foot which may extend from the toes up the foot to the heel and eventually up to the lower leg or higher. Because there is no feeling, these patients are subject to severe pressure induced ulcerations which can be caused by high peak pressures, or by hard foreign particles that may get in their shoe which they do not realize are present. This often results in ulceration of delicate skin, which in diabetic patients is often very difficult to heal. Sometimes the festering ulcerations become infected, contain scar tissue and may result in secondary problems up to and including amputation. There were an estimated 54,000 amputations of this kind done in the United States in 1998. There are an estimated 23 million diabetics in the United States alone.  
           [0006]    Prior art solutions have attempted to solve the problem by attempting to control the pressure on the bottom or sole of the foot. For example, a company called Royce Medical Company has modified their ordinary leg walker by replacing the normal Poron™ inner-sole with about a ⅜ inch thick cross linked polyethylene foam inner-sole material known as “plastazote” where the upper surface is cut into small hexagon shapes of roughly ⅜ inch across. One or more of the hexagonal areas directly under the ulceration or pressure site can be removed to create a reduction in pressure at the ulcer site itself. This can sometimes cause a distended wound because the exudate coming out of the ulcerated area causes a distention of the ulcer site which eventually granulates in to form scar tissue that has to be shaved off to avoid high pressure in that area when the foot is placed in a normal shoe. Removal of support under part of the sole of the foot tends to increase pressure loading of remaining portions of the foot which are supported. Royce Medical Company is the owner of U.S. Pat. No. 5,464,385 entitled “Walker with Open Heel”.  
           [0007]    Another example of the prior art approach is the walker produced by a company called Aircast, known as the Aircast Diabetic Walker™. To the ordinary walker they install a layer of about ½ inch to ⅝ inch thick cross-linked polyethylene foam referred to in the industry as “plastazote” foam in the bottom of the walker. It is a flat material which takes a compression set. While this does tend to distribute pressure over more of the foot to some extent, the support is still provided mainly by the boney prominences of the foot where the heel and ball of the foot fully compress the foam material. High unit pressure is found in those areas. We describe this result as producing a parabolic pressure distribution curve with a very high peak right under the boney areas.  
           [0008]    Heretofore, the best available orthotic is a molded orthotic device which has been developed in the last several years using a technique called Total Contact Casting. Typically, a dressing is applied over the wound and then a piece of cotton or wool felt that will absorb exuding fluid is placed around the foot and held in place by a circularly knitted tubular material which is called a stockinet. Then, in one preferred method, a material called “conform”™ foam or “tempur”™ foam is used next. Approximately a ½ inch layer of this is placed under the arch and folded over the front of the toe down to the sides and pinched in on the sides creating somewhat of a cocoon below the ankle bones from the bottom of the foot up and over the forefoot. Over the top of this is wrapped some padding material for the cast which is either a cotton or polyester wool as is used for any other type of cast. Then a first layer of plaster or synthetic material is placed over the foot to form the cast and a wooden board is placed under the foot. Another layer of plaster or synthetic casting is plastered over the whole thing thus creating a “cocoon” for the foot. The “conform”™ foam or “tempur”™ foam has an open granular structure which compresses easily and rebounds extremely slowly. It will not sustain the body&#39;s weight without going to essentially zero thickness. We believe the Total Contact Cast nevertheless still produces a parabolic pressure distribution curve under the boney portions of the foot. Unfortunately, the total contact cast is heavy and not well designed for walking. The user has to pick the whole foot up and lay it down again, and it can only be used for about a week before it has to be removed and the foot cleaned and a new cast applied. The weight and bulkiness of the total contact cast create additional problems for diabetic patients. Patients can&#39;t remain immobilized to keep their weight off the cast. It is necessary for them to do some walking. Walking is beneficial because it actually stimulates the healing process. As a result, diabetics will start developing problems in other areas of their body because they are sensitive to pressure. Their tissues will break down at about half of what a young athlete can take without damage. The use of crutches can cause additional ulcers under the arms or on the hands.  
           [0009]    Modern medical theories suggest that there may be some threshold unit pressure maximum if healing is to occur. If higher pressures are produced in “hot” spots, healing may take an extended time or be difficult to obtain at all. It appears that what might be called the time-pressure integral may also play an important role. The time-pressure integral relates to the cumulative effect of activity by the patient which produces pressures under all of the foot over a given time period.  
           [0010]    It would be desirable to have a walker which can be used over an extended period of time and which improves upon the attributes of the total contact cast by reducing the peak plantar pressure operating on the injured foot while walking in the walker. We have demonstrated such an improvement with a new approach that utilizes the arch and side areas of the periphery of the foot to support part of the load on the foot and reduce the maximum peak pressure under the sole of the foot.  
         SUMMARY OF THE INVENTION  
         [0011]    The improved walking boot of the invention for diabetic and other patients reduces the maximum peak pressure applied to the bottom or plantar surface of the foot while standing or walking, as compared to the best prior art orthopedic devices. The new walking boot is referred to as the Bledsoe Conformer Boot. The walking boot has a premolded foot-shaped cavity and an inner-sole made of conformable material which is molded by foot pressure to the shape of the foot. It operates on the principle of preloading the arch and side edges of the foot to take and spread some of the weight load on the foot before the bottom of the foot is fully loaded. Supporting pressure for the foot is spread over a larger area to reduce the peak unit pressure at any particular area. This is an improvement over flat-bed boots even though they may have a contoured surface and be made of a flexible or spongy material and have a compressible insole.  
           [0012]    The improved walking boot has a walking shell having an inner surface with an upturned edge portion which forms an unyielding generally foot-shaped bed adapted to support a mid-sole. The walking shell has an upwardly angled forward portion which the tread follows to allow the boot to roll forward in a walking step. The rear portion of the heel on the tread is angled to improve walkability also. A mid-sole is supported and held in the generally foot-shaped bed of the walking shell. The mid-sole is premolded to form a foot-shaped cavity with upwardly and outwardly rounded side edges to form a resilient but non-compressively setting support for the arch and sides of the heel and foot in addition to the bottom of the foot. Over the foot-shaped cavity of the mid-sole is placed a conformable inner-sole formed from a pliable but compressibly settable material which is referred to as a self-molding material that takes the shape of the bottom portion of the foot when the foot is pressed into the foot-shaped cavity. In response to foot pressure between the sides, arch, and bottom of the foot and the sides, arch, and the bottom of the foot-shaped cavity in the mid-sole, the inner-sole conforms to the shape of the foot thereby compensating for small differences between the shape of the foot and the shape of the foot-shaped cavity. Weight applied to the foot compresses and molds the conformable inner-sole to fit tightly between the heel, arch, and sides of the foot and the sides and arch area of the cavity thereby preloading the foot along the heel, arch, and sides of the foot before the heel and ball of the foot are fully loaded by compressing the inner-sole and the mid-sole at the bottom of the cavity. The foot-shaped cavity in the mid-sole has a foot-shaped opening near the size of a selected average foot. The size and shape of the foot-shaped cavity and the thickness of the conformable inner-sole are selected to assure that the foot is preloaded along the sides and arch of the foot-shaped cavity before the foot is fully loaded on the bottom of its heel and ball areas. The cross sectional thickness of the mid-sole and the highly loaded areas under the heel and ball of the foot are selected to be a minimum thickness in order to minimize leg height differential and any relative motion tending to be caused by compression of the mid-sole arising because of periodic compression of the mid-sole in response to foot loading while walking. Relative motion between the foot and the foot-shaped cavity is minimized to prevent any tendency for chaffing.  
           [0013]    The walking shell has upwardly turned edges along the sides and heel areas which provide support to the outer lower surface of the mid-sole to prevent any spreading of the mid-sole in response to pressure from the weight of the patient. The upper surface of the foot-bed and the lower outer surface of the mid-sole are closely conforming so that unyielding support is provided by the rigid walking shell.  
           [0014]    The walking shell has a pair of upstanding struts which extend upwards on both sides of the leg, attached to the upturned edges of the shell which serve to secure the walking boot on the leg of the wearer. The walking boot further includes a durable and resilient soft protective bootie adapted for extending around the lower leg and foot and having an open bottom portion having sides all around the foot and a toe box that are secured to the upper surface of the inner-sole to form a soft protective bootie around the foot and lower leg. Attached to each of the struts is a sheath which is provided with patches of hook and loop material for the purpose of attaching the bootie to the shell. The bootie also has appropriately located patches of hook and loop material which together with encircling straps removably secure the structure to the leg. The shell also contains straps together with hook and loop material or other appropriate fastening means which hold the assembly snugly on the foot.  
           [0015]    The Bledsoe Conformer Boot is usable for the duration of the injury and does not have to be replaced every five to seven days as does the Total Contact Cast. The conformable inner-sole comprises an elastomeric foam having a skinned outer surface to prevent penetration by moisture, exudate or other liquids to which it might be exposed. Since these materials do not penetrate the inner-sole, the material is subject to washing and/or disinfecting if it is necessary to dress a wound or ulcerated area. Unlike the Total Contact Cast which is fixed on the lower leg and foot, the Bledsoe Conformer Boot is removable by the patient, as for example, at bed time. It is truly a walker which facilitates walking because it has good walkability due to the shape of the floor contacting surfaces. The bootie is made from a soft breathable foam material of about ¾ inch in thickness which together with the insole provides a protective “cocoon” to prevent foreign materials from entering the foot chamber. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a perspective view of the improved walking boot and bootie in the completely installed position;  
         [0017]    [0017]FIG. 2 is an exploded perspective view showing the walking shell, mid-sole and construction of the bootie secured to the inner-sole of the walker of FIG. 1;  
         [0018]    [0018]FIG. 2A illustrates a preferred manner in which the bottom edge of the bootie can be attached to the inner sole;  
         [0019]    [0019]FIG. 3A is a sectioned side elevation of the walker shell on the lines  3 A- 3 A of FIG. 2 showing one of the upwardly extending struts on the shell and fastening means which are used to secure the walker to the foot;  
         [0020]    [0020]FIG. 3B is a sectional elevational view of the walker shell of FIG. 3A on the lines  3 B- 3 B looking to the rear of the boot;  
         [0021]    [0021]FIG. 4A is a plan view of the mid-sole which is supported directly on its bottom surface by the inner surface of the walker shell;  
         [0022]    [0022]FIG. 4B is a side elevation of the mid-sole of FIG. 4A;  
         [0023]    [0023]FIG. 4C is a bottom view of the mid-sole of FIGS. 4A and 4B;  
         [0024]    [0024]FIG. 4D is a section in side elevation of the mid-sole for the walker shell of FIG. 4A-C along the lines  4 D- 4 D of FIG. 4A;  
         [0025]    [0025]FIG. 4E is a section in front elevation at the arch area of the mid-sole of FIG. 4A-C on the along the lines  4 E- 4 E of FIG. 4A;  
         [0026]    [0026]FIG. 4F is a section in elevation of the heel area of the mid-sole of FIG. 4A-C along the lines  4 F- 4 F of FIG. 4A;  
         [0027]    [0027]FIG. 5A is a plan view of the upper surface of the inner-sole which is supported by the mid-sole of FIGS.  4 A-F;  
         [0028]    [0028]FIG. 5B is a side elevation of the inner-sole of FIG. 5A which shows a flange extending laterally from the upper surface;  
         [0029]    [0029]FIG. 5C is a bottom view of the inner-sole of FIGS. 5A and 5B;  
         [0030]    [0030]FIG. 5D is a section in side elevation of the inner-sole of FIG. 5A-C along the lines  5 D- 5 D in FIG. 5A;  
         [0031]    [0031]FIG. 5E is a section in front elevation at the arch area of the inner-sole of FIGS.  5 A-C along the lines  5 E- 5 E of FIG. 5A;  
         [0032]    [0032]FIG. 5F is a section in front elevation of the heel area of the inner-sole of FIG. 5A-C along the lines  5 F- 5 F of FIG. 5A;  
         [0033]    [0033]FIG. 6A is a cross sectional representation in elevation through the heel area of the combined in-sole/mid-sole showing the position of the mid-sole below and the in-sole above before the weight of a foot is imposed upon the in-sole;  
         [0034]    [0034]FIG. 6B is a combination mid-sole and in-sole of  6 A after the weight of a patient&#39;s foot has been imposed upon the in-sole of FIG. 6A;  
         [0035]    [0035]FIG. 7A is a representation in elevation showing the heel area of a patient&#39;s foot standing on a flat hard surface;  
         [0036]    [0036]FIG. 7B is a schematic representation showing the parabolic nature of the high peak unit pressures generated by weight imposed upon the patient&#39;s heel to support the weight;  
         [0037]    [0037]FIG. 8A is a cross sectional representation in elevation of the heel area of a patient standing in a total contact cast with the foam layer collapsed;  
         [0038]    [0038]FIG. 8B is a schematic representation of the improved but still parabolic nature of the peak unit pressures produced in the heel area by the total contact cast in response to loading of the foot;  
         [0039]    [0039]FIG. 9A illustrates a cross section elevation in the heel area of the improved walking boot of the present invention showing how part of the load is supported on the sides of the in-sole/mid-sole combination in addition to the support provided to the bottom of the foot;  
         [0040]    [0040]FIG. 9B is a schematic representation of the forces imposed on the patient&#39;s foot in support thereof by the improved walker boot of FIG. 9A wherein the load is supported over a greater area without parabolic peaks;  
         [0041]    [0041]FIG. 10 is an outline of a person&#39;s foot indicating the amount of supported area when the foot is supported in different ways;  
         [0042]    [0042]FIG. 11 is a graphical representation of the data from Table II showing that the average peak pressure on the plantar surface of the foot is lower with the present invention than the next best prior art alternative;  
         [0043]    [0043]FIG. 12 shows a grid of average peak pressure measurements for a patient wearing an ordinary shoe;  
         [0044]    [0044]FIG. 13 is a grid of average peak pressure measurements for the same patient using the Total Contact Cast;  
         [0045]    [0045]FIG. 14 is a grid of average peak pressure measurements for the same patient showing lower peak pressures with the improved walker boot of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0046]    In the description that follows, the improved walking boot for diabetic and other patients of the invention, is designated generally by the reference numeral  10 . Throughout the description that follows, the same reference numerals will be applied to similar parts. Reference numerals with primes represent similar structure not exactly the same.  
         [0047]    [0047]FIGS. 1 and 2 illustrate the combination of a walking shell generally designated  12  and what is referred to as a protective “bootie” generally designated by the reference numeral  14 . This is more clearly seen in FIG. 2 where they are separated. FIG. 1 illustrates a combination in use on a patient&#39;s leg and foot  16  which will be referred to as foot  16 .  
         [0048]    Walking shell  12  in FIGS. 1 and 2 has an inner surface  18  and an outer surface  20  to which is attached a walking tread  22  preferably made of elastomeric material such as rubber. The shell is preferably bent slightly upwardly at what will be called a “rocker” line  24  which improves walkability of the structure when the patient moves forward. The tread follows the shape of the shell in this regard. An angled heel on the tread and an angled front greatly improve walkability.  
         [0049]    Inner surface  18  of the walking shell comprises a foot bed in the shell designed to receive and support a mid-sole  28  which is seen in more detail in FIGS.  4 A- 4 F. The mid-sole has a lower outer surface  30  which is supported by the inner surface  18  of walking shell  12 . Walking shell  12  has upwardly turned edges  32  in the heel area, edges  32 ′ in the side foot area and  32 ″ in the forefoot area. Although they need not be symmetrical, it is preferred that the upturned edges be generally the same on both sides. The lower outer surface of  30  of mid-sole  28  has upwardly rising side portions  34  at the heel,  34 ′ at the sides of the foot and  34 ″ in the forefoot area which correspond to the upwardly turned edges  32 ,  32 ′ and  32 ″ of the walker shell. These surfaces conform with each other to provide firm unmoving support for the mid-sole. Additionally, it may be desirable to secure by means of adhesive or tape with adhesive, the lower outer surface of the mid-sole  28  to the upper surface or surfaces of foot bed  26 .  
         [0050]    Walker shell  12  further includes a flange  36  which is preferably formed as an extension of the sides  32 ′ on each side of the shell. Attached to each one of the flanges  36  is an upright strut  38  comprising a pair of upright struts  38 . The upright struts  38  are attached to the flanges  36  by means of fasteners  39  best seen in FIGS. 3A and 3B. Each strut  38  is preferably covered with a cloth sheath  62  (attachment means) which is provided with spaced apart patches of hook and loop material  40  which are used to removably attach bootie  14  as seen in FIG. 1. Attachment straps  64  have hook and loop material on their underside to engage hook and loop material  40  on the sheath  62  covering the struts to encircle and secure the entire walking boot assembly to the lower leg and foot  16 . The outer surface of second back portion  58  has patches of hook and loop material to engage corresponding patches of hook and loop material  40  on the inside of the sheaths  62  as well as seen in FIGS. 1 and 3B. These constitute means for removably attaching booties  14  containing the lower leg and foot to the walker shell  12 . Buckles  42 , preferably two on each side of the shell are fastened to the shell. Fastening means include a pair of straps  44  also having hook and loop material  46  at appropriate locations. These straps  44  strap over the bootie and foot to hold the walker shell and bootie  14  components in place.  
         [0051]    Protective bootie  14  is best seen in FIGS. 1 and 2. Bootie  14  is made with soft flexible spongy foam material which preferably breathes to some extent when it is wrapped around and secured to cushion the patient&#39;s foot. Bootie  14  has a toe box  48 , a tongue  50 , side panels  52 , a first back portion  54  and a second back portion  58 . An inner-sole generally indicated by the reference numeral  60  is seen forming the bottom of bootie  14  on which the sole of the foot will rest. Appropriately placed hook and loop material  62  is fastened to the bootie at appropriate places which makes it possible to enclose the injured foot within the bootie as shown in FIG. 1.  
         [0052]    The foot is placed in bootie  14  and the open flaps  52  are crossed over the tongue  50  and fastened with hook and loop material  62 . The second back portion is wrapped around the lower leg and heel and also fastened with hook and loop material  62 . The foot and bootie are placed in the shell and the straps  44  are passed over the overlapping side portions and tongue of bootie  14  where they are secured by hook and loop material  46 .  
         [0053]    An improved supporting platform for the bottom of the feet is provided by the combination of a pre-molded mid-sole illustrate in FIGS.  4 A- 4 F and a self-molding inner-sole illustrated in FIGS.  5 A- 5 F. In FIGS.  4 A- 4 F, mid-sole  28  is pre-molded to have a lower outer surface adapted to be received in the foot bed of the walker shell and an upper surface  66  raised above the lower surface  30  and having a foot shaped cavity generally designated  68 . Foot-shaped cavity  68  has a bottom surface  70  spaced below upper surface  66 . Mid-sole  28  is formed, preferably in one structure, from a material having the characteristic that it will rebound from pressure force imposed by a foot and will not take a compression set, thereby essentially retaining its pre-molded shape after use. Yet it is flexible and will yieldingly deform to a limited degree when loaded by a foot. Most significantly, the foot shaped cavity  68  has upwardly and preferably outwardly curving sides which rise to a foot shaped opening  72  at upper surface  66 . Foot shaped cavity  68  has upwardly curving side walls  74  around the heel area, upwardly curving side walls  76  along the sides of the foot in the mid-foot area and upwardly curving side walls  78  in the forefoot area. The upwardly curving walls at any given elevation generally lie parallel the foot shaped opening  72 . Also provided is an arch support area  80  which rises smoothly from the bottom in the normal manner of arch supports. The contour lines “C” in FIG. 4A are meant to indicate changes in elevation much as in a topographical map. It should be noted that this depressed area which comprises the foot shaped cavity  68  is fairly deep, especially at the heel area and in the vicinity of the front of the mid-foot where the ball of the foot will be placed. The depth may range from approximately ¾ inch to as much as approximately 1 inch in the deepest areas. The exact depth and size of the foot-shaped cavity is largely a matter requiring some experimentation to obtain the best results.  
         [0054]    With the foot shaped cavity about the same or slightly larger than the outline of a foot, the unique pre-molded cavity provides peripheral side edge support for the foot during standing or walking which is superior to any form of flat bed or contoured flat surface and reduces “peak pressure” on any particular area of the bottom of the foot. Peak pressure is meant to indicate the maximum unit pressure applied to any given portion of the foot while walking in the boot structure. Part of the load is spread around the sides of the foot rather than just being supported on the bottom of the foot, as is the case when the foot is placed on a flat surface. When the foot is placed on a flat surface, peak pressures can be expected mainly under the heel and ball of the foot where forces from the foot bones are primarily applied and where there is a minimum of protection underneath the boney projections in those areas in the form of flesh, muscle and fatty tissue. The exact shape and curvature of the walls in the foot shaped cavity is largely a matter of trial and error and subject to the difficulty that feet do not come in a standard uniform shape or size. Nevertheless, the basic principle of providing a foot shaped cavity with sloping walls has been shown to reduce the maximum or peak unit pressure and the average unit pressure over the best alternative currently available, namely the Total Contact Cast. Because there are differences in shape and size of feet, the mid-sole of the invention is preferably used in combination with an inner-sole  60  having generally a foot shaped outline but having quite different characteristics.  
         [0055]    Inner-sole  60  is illustrated in FIGS.  5 A- 5 F. The combination of inner-sole  60  and mid-sole  28  is illustrated in FIGS. 6A and 6B. Referring now to FIGS.  5 A-C, inner-sole  60  has a foot receiving upper surface  82  and a lower outer surface  84  comprising a bottom surface adapted to fit over upper surface  66  of mid-sole  28 , especially over the foot-shaped cavity  68 . Upper surface  82  of inner-sole  60  preferably has a slightly depressed contoured upper surface as indicated in FIGS.  5 D- 5 F. This is largely a matter of feel and comfort which help center the foot. The bottom surface or underside  84  is also contoured as indicated by the contour lines C in FIG. 5C. A raised contoured arch area  86  may be included for comfort, better fit and arch support. A peripheral flange  88  is preferably provided all around the inner-sole. The peripheral flange is useful for securing the inner-sole against movement and provides a convenient means of attachment to bootie  14  as indicated in FIG. 2A by sewing, adhesive or other means.  
         [0056]    Inner-sole  60  is preferably formed in one piece from a material having a self-molding characteristic in response to pressure from a foot. It is a spongy preferably foam material having the characteristic that it does not readily rebound from pressure force and will take a compression set in response to foot pressure. The material should compress readily for more than half of its thickness before it begins to significantly resist further compression caused by the foot. Inner-sole  60  preferably is molded from an elastomeric foam material having a skinned outer surface to prevent absorbing fluids from ulcerated areas of a patient&#39;s foot. Because the inner-sole can be cleaned, it does not require discarding after a period of use by a patient as does the Total Contact Cast.  
         [0057]    [0057]FIGS. 6A and 6B illustrate how the mid-sole  28  and inner-sole  60  work together to distribute foot loading to the boot shell over a greater peripheral area of the foot. These are simplified diagrams which exclude all the other components of the walking boot of FIG. 1 for purposes of clarity. For purposes of illustration, these may be considered cross sections through the heel area of FIG. 4F and FIG. 5F, although the same advantage is observed around the rest of the foot.  
         [0058]    [0058]FIG. 6A illustrates the initial condition before the materials have been subject to foot pressure. In FIG. 6B, inner-sole  60  has been self-molded by exposure to foot pressure and compressed to a significant degree, especially in the bottom area  90  of FIG. 6B. The side wall areas  92 ,  94  have been compressed also, but to a lesser extent than the bottom  90 , as compared to the original thickness of inner-sole  60 . Although inner-sole  60  in its compressed configuration remains flexible and retains some compressibility, it is essentially compression set. It does not return to its original shape when the foot is removed whereas mid-sole material  28  always returns essentially to its initial shape when force imposed by the foot is removed. The result is an altered foot-shaped cavity  68 ′ which has been self-molded by the foot to form upwardly and outwardly curving side walls  92 ,  94  around the heel and other sides of the foot. Pressure from the foot has caused the inner-sole to mold itself closely to the foot and tightly against the upwardly and outwardly curving walls of mid-sole  28 . It can be seen that the load imposed on the foot by the weight of the person is not concentrated only on bottom  90  but is also partially resisted by the side portions  92 ,  94  because the shape and thickness of the material is selected so that the outer peripheral edges of the foot come in contact with the side walls of the foot-shaped cavity  68 ′ before the foot bottoms out at the bottom  90 . It should also be noted that the cross sectional thickness  96  of mid-sole  28  is selected to be a lesser thickness under those parts of the foot having boney protrubences, here the heel, thereby minimizing leg height differential and any relative motion between the foot and the sides of the foot-shaped cavity  68 ′ which is supporting the foot, which could otherwise be caused by periodic compression of the mid-sole in response to foot loading while walking.  
         [0059]    [0059]FIGS. 7A, 8A and  9 A schematically represent various supporting structures which might be considered as being in the nature of vertical cross sections through the heel portion of a supporting structure in FIGS. 8A and 9A. FIGS. 7B, 8B and  9 B are schematic representations of the force distribution acting on the supported portion of the heel. The magnitude of the force is indicated by the length of the arrows.  
         [0060]    [0060]FIG. 7A illustrates the foot  16  supported on a board  96 . This is a condition which would be experienced walking on a hard surface in bare feet. The heel bone is not far under the surface of the skin and fleshy padding. Although the fleshy padding is able to distribute the weight to some extent, the distribution of weight is limited and a fairly high pattern of peak forces  98  support the weight over a limited area. The forces vary, of course, from zero when the foot is in the air to a maximum when the heel comes down and the weight of the body is rolled over it. FIGS.  7 B- 9 B are meant to indicate the maximum force distribution on the foot which occurs while walking or standing. In FIG. 7B, this maximum force is distributed over an area  100  which exhibits what we call a parabolic force distribution. The forces are highest in the center and drop off rapidly near the edges.  
         [0061]    [0061]FIG. 8A schematically represents the Total Contact Cast  102 . The cast material itself is material such as plaster of paris or a synthetic cross linked polymer mixture. Not all of the layers of wrapping are shown here under the cast, but one possible feature that is shown is the elastomeric foam material  104 . The board  96  is shown as it is usually a component of the Total Contact Cast. It can be seen that the supported area  106  is significantly larger than the area  100  of FIG. 7. The peak forces  108  are significantly smaller than are in FIG. 7B but they still have what we refer to as a parabolic shape with the highest forces applied to the lowermost boney parts of the foot. Most of the supporting force is in the center and falls off rapidly to each edge.  
         [0062]    [0062]FIGS. 9A and 9B represent the improved walking boot  10  of the invention. FIG. 9A shows the unyielding walking shell  12  having a tread  22 , closely supporting mid-sole  28  and preventing it from spreading outward. Inner-sole  60  has been substantially compressed by the weight of the foot to the point where it provides substantial resistance to further compression. Because the foot is “wedged” into the foot shaped cavity  68 ′, the force to support the weight on the foot is distributed over a significantly larger area  110  and the resulting peak forces  112  in FIG. 9B are measurably less than FIG. 8B. Since the Total Contact Cast of FIG. 8A is the best known prior art structure, this means the improve walking boot of the invention represents an advance in the art of Orthopedic devices.  
         [0063]    [0063]FIG. 10 is an orthotic of a person&#39;s foot indicating schematically the amount of supported area when the foot is supported in different ways. The area  120  might be the imprint of a damp bare foot on dry concrete. With a normal arch, the weight is distributed over a relatively small area compared to the area of the bottom of the boot. The area  122  is believed to be the kind of supported area that a contoured but generally flat and somewhat resilient walker orthotic in-sole might provide. There is more supported area to reduce unit pressure imposed on the bottom of the foot, but the supported area is still significantly less than the total available area. The dotted area  124  is meant to symbolize the amount of supported area that can be provided by the invention. Because part of the support for the foot comes from the peripheral areas of the foot, the foot load is spread over a still greater area with resulting lower unit pressure at any given location around or on the bottom of the foot.  
         [0064]    A way has been found to measure plantar pressures under the foot using the Novel Pedar in-shoe pressure measurement system made by Novel of Dusseldorf, Germany. The Novel system has an insert which looks like the inner-sole in a shoe and is shaped like a foot so it will fit right into a shoe. The in-shoe sensor has an upper grid and a lower grid separated by a layer of silicone with a vinyl layer on the top and bottom of the in-shoe pressure measurement device. The grids form a plurality of little squares distributed regularly over the area of the in-shoe pressure measurement device. Conductors representing each of the little sensor squares are connected to a programmed computer which measures changes in capacitance that occur when the grids are moved closer to each other in response to pressure forces. The device is approximately 2 mm thick with approximately 99 sensors per insole and roughly 1 sensor per square centimeter depending upon the insole size. The Novel Pedar in-shoe pressure measurement device is calibrated by means of a diaphragm using a known air pressure to push down on the insole. Very low pressures below about 1 or 2 newtons per centimeter square are treated by the software as zero pressure.  
         [0065]    A series of comparisons were made using the Novel device to compare the performance of the best available orthopedic device, the Total Contact Cast, with the improved walking boot of the invention. Eighteen normal subjects without any prior foot or ankle problems were employed in this study. There were 7 females and 11 males in the study with an average weight of 85.6 kilograms and an average height of 177 centimeters. Data on these 18 subjects is given Table 1 below. The results of the tests are given in Table II and displayed graphically in FIG. 11.  
                                                         TABLE 1                                   SUBJECT   AGE   WEIGHT   HEIGHT                                        Sub 1   27.0   82.7   182.9           Sub 2   46.0   86.4   182.9           Sub 3   34.0   77.3   170.0           Sub 4   27.0   62.7   154.0           Sub 5   33.0   87.3   190.3           Sub 6   49.0   75.0   177.8           Sub 7   27.0   47.7   154.9           Sub 8   45.0   115.9   193.0           Sub 9   49.0   125.0   190.5           Sub 10   39.0   100.0   188.0           Sub 11   66.0   113.6   190.5           Sub 12   38.0   117.3   162.6           Sub 13   21.0   95.5   170.2           Sub 14   34.0   66.4   177.8           Sub 15   27.0   63.6   167.6           Sub 16   35.0   86.4   188.0           Sub 17   26.0   65.9   162.6           Sub 18   46.0   72.7   172.7           average   37.2   85.6   176.5           standard dev.   11.3   21.9   12.7                      
 
         [0066]    The present invention has been given the name Bledsoe Conformer Diabetic Boot or “Boot”. Each subject was asked to walk  1 .) in the Bledsoe Conformer Diabetic Boot and  2 .) in a well-padded Total Contact Cast which is also referred to as a short leg cast. The Total Contact Casts were all administered by the same casting technician using the same techniques applied by the Baylor University Medical Center, Dallas, Tex. to treat diabetic ulcers. The subjects were randomly assigned to the order of testing for the two conditions and asked to walk several times at a self-selected speed down a ten-meter walkway. Approximately 15 steps for each condition were used for averaging and statistical analysis. Paired t-tests were used to compare between the short leg cast results and the boot results at an alpha level of 0.05 for the statistical tests. The tests were naturally conducted over a period of weeks because it takes a great deal of time and effort to prepare and apply the Total Contact Cast to the individual feet. Pressure maps of each Novel insole were divided into three regions called masks: heel, midfoot, and forefoot. The heel is generally the area from the back of the heel to the front of the heel, the midfoot is generally the area from the front of the heel to the ball of the foot, and the forefoot is the area from the ball of the foot to the toes. Each mask area included a certain number of the sensor squares.  
         [0067]    Although a number of different measurements were made, peak plantar pressure is considered to be most significant to the diabetic ulceration problem because of theories that below a certain peak plantar pressure new ulcers will not form and ulcers already formed will heal.  
                                                                                                                 TABLE II                           PEAK PRESSURE - N/cm 2                  TOTAL   HEEL   MIDFOOT   FOREFOOT            SUBJECT   BOOT   CAST   BOOT   CAST   BOOT   CAST   BOOT   CAST                    Sub 1   15.2   23.3   14.3   16.0   8.1   7.9   13.6   23.0       Sub 2   10.7   19.1   9.6   12.5   5.2   10.3   10.5   19.1       Sub 3   14.3   22.3   12.9   14.5   5.3   8.7   14.3   22.3       Sub 4   11.9   12.9   9.2   12.6   3.9   5.3   11.8   8.5       Sub 5   14.2   21.7   12.9   16.6   5.6   11.6   13.3   21.6       Sub 6   9.9   22.6   7.8   9.1   7.5   4.0   8.5   22.6       Sub 7   13.7   14.5   12.6   11.8   7.2   8.0   12.8   14.2       Sub 8   19.7   26.8   11.6   26.1   4.9   12.7   18.9   23.8       Sub 9   13.2   21.0   9.5   17.0   3.2   10.5   13.2   20.8       Sub 10   11.3   20.5   9.6   16.3   2.7   11.6   11.2   19.1       Sub 11   20.5   24.1   20.5   16.3   9.7   16.3   11.6   23.8       Sub 12   12.9   18.3   11.6   6.0   8.9   8.1   11.9   18.3       Sub 13   13.7   20.3   13.7   10.2   8.6   9.8   9.7   20.3       Sub 14   13.5   14.8   12.6   12.9   10.2   5.8   12.2   14.0       Sub 15   13.8   20.2   12.8   20.2   3.7   6.5   9.8   9.6       Sub 16   18.4   21.9   18.4   21.9   6.1   9.0   8.1   10.6       Sub 17   14.5   15.6   13.2   12.9   13.2   9.6   9.3   15.2       Sub 18   10.0   12.5   9.9   8.5   9.6   5.1   4.6   11.1       average   14.0   19.6   12.4   14.5   6.9   8.9   11.4   17.7       stdev   2.9   3.9   3.1   4.8   2.8   3.1   3.0   5.2       T-test       0.00000       0.07730       0.05910       0.00002                  
 
         [0068]    Table II has four columns containing comparative data for each subject wearing the boot and the cast. The data is paired and given in terms of newtons of force per centimeter squared. The left hand column gives the peak pressure in newtons per centimeter square that was found anywhere on the foot. The other three columns from left to right give the peak pressure respectively in the heel, midfoot and forefoot area for each of the Bledsoe Conformer Boot and the Total Contact Cast. Averages and standard deviations were calculated for each column of data. In each case the average peak pressure for the boot was lower than the average peak pressure for the Total Contact Cast in every area of the foot. The difference was considered to be statistically significant in at least the midfoot and forefoot areas in this test and in another test was considered to be statistically significant in each of the heel, midfoot and forefoot areas. The cross bar and stem sitting on top the vertical data bars in FIG. 11, as indicated by asterisks  118 , are meant to represent the scope of the range of the data contained within the data bar. This is true for all data bars.  
         [0069]    [0069]FIGS. 12, 13 and  14  show representations of the sensor quadrants for a single patient wearing the shoe, the Total Contact Cast and the Bledsoe Conformer Boot. Each of the small squares can be considered a pressure sensor of the Novel Pedar in-sole sensing device. A grid of numbers at the left and above identify the sensor squares. A graphical code for the pressure reading is given on the right hand side of each chart in newtons per square centimeter. The values are indicated as being greater than or equal to the number corresponding to the graphical code. While the scale shown only goes up to 30 newtons per square centimeter, it should be understood that some of these values actually went up to a figure of 60 newtons per centimeter squared but this was not reflected in the charts. The heel in these charts is on the left hand side of the chart. A blank area in the shoe chart indicates a failure of the sensors to record a pressure value.  
         [0070]    What is significant about these charts is that they illustrate the difficulty of the problem because of the varying contours of the plantar surface of the foot and the boney projections which distribute weight nonuniformly and in fact create “hot” spots. In the shoe example of FIG. 12 it can be seen that there is an area of high pressure in excess of 30 newtons per square centimeter which appears to be near the big toe area. There are pressures in excess of 22 newtons per square centimeter in the area of the ball of the foot. The Total Contact Cast of FIG. 13 exhibits lower pressures overall but there are still some areas in excess of 22 newtons per square centimeter. In contrast, the Bledsoe Conformer Boot in this example had no areas anywhere on the foot that were equal to or greater than 15 newtons per centimeter squared.  
         [0071]    In the best mode, the walker shell is formed from aluminum sheet because it is lightweight and will bend should it be necessary to make slight adjustments. The self-molding inner-sole is a closed cell off-white PVC foam from Saint-Gobain Performance Plastics Corporation, Granville, N.Y. under the designation HAFG  16  having an overall thickness of about ½ inch. The material has a density of about 7.5 pounds per cubic feet and a hardness on the Shore  00  scale which is said to be about 56. The material has the characteristic that it will readily compress to less than half its thickness and if compressed to less than half its thickness for a significant period of time by the foot, tends to retain the compressed shape. It has a fairly flat increase in deflection before it begins to resist.  
         [0072]    The mid-sole is preferably made from Bayflex® 904 obtained from the polymer division of Bayer Corporation. It is described as a microcellular polyurethane foam system which was developed for use in applications requiring a microcellular core and a tough abrasion-resistant outer surface. It is formulated to a “hardness” of about 65-75 on the Shore  00  scale.  
         [0073]    Although the invention has been disclosed above with regard to a particular and preferred embodiment, it is not intended to limit the scope of this invention. It will be appreciated that various modifications, alternatives, variation, etc., may be made without departing from the spirit and scope of the invention as defined in the appended claims.