BRIEF SUMMARY OF THE INVENTION

[0001] The present invention relates to low friction materials formed into patches with compound curvature. These patches can lower the magnitude of frictional loads acting against the skin of a living being. These patches can reduce the likelihood of tissue damage in a living being.

BACKGROUND

[0002] Many persons are affected by areas of sensitive and/or damaged skin and tissue such as ulcerations, blisters, corns, abrasions, calluses, hot spots, bursas and other forms of tissue trauma. Persons with limited sensation in their limbs, paralysis, diabetes, and those with poor blood flow can be particularly susceptible to skin and tissue damage.

[0003] Medical professionals have traditionally understood that skin and tissue damage can result from loads applied to the skin. These loads can be due to weight bearing of the body or other bumps and blows to the skin.

[0004] Loads to the skin can be either static or dynamic. A static load is a nonvarying load typically caused by the weight of a mass at rest. A paralyzed patient whose body mass is frequently at rest could experience a high static load on the skin.

[0005] A dynamic load is a load that varies over time. A runner would experience high dynamic skin loads as each foot alternatively hitting the ground and then being lifted.

[0006] A load acting perpendicular to the surface of the skin is called a normal load. In everyday practice we might refer to the normal load as the pressure or compressive load. The normal load plays a role in understanding the effects of friction loading.

[0007] In everyday language we might refer to the results of friction loads as rubbing or abrading. The friction load can be no greater than the normal load times the coefficient of friction. If L _f is the friction load, L _n is the normal load and CoF is the coefficient of friction then:

L _f < L _n ^x CoF

[0008] If for example a very high normal or pressure load is applied to a surface that is very slippery, i.e. has a low CoF, then friction load will be low. [0009] Shear stress is a force applied parallel to a face of a material over a given area. A friction load, which acts parallel to the surface of the skin, results in shear stress on the body. While friction acts on the surface of the skin, shear stresses, also known as shear loadings, also act on the tissues below the skin.

[0010] Like the normal load, shear loading can also be static or dynamic. For example a person with paralysis positioned on a high friction surface may experience high static shear loadings. On the other hand a runner whose foot was contacting a high friction surface would experience high dynamic shear loadings on the tissues in the bottom of the foot.

[0011] What is not well enough understood in the medical community is the role that shear stresses play in tissue damage. The vast majority of efforts to date have focused on reducing tissue damage by reducing the normal or pressure load i.e. "pressure offloading". This approach however is problematic. Pressure loads are typically a result of supporting the mass of a body. When a pressure load is removed from one area of the body, the mass of the body does not change and so another area of the body must take an increased pressure load.

[0012] Removing pressure from areas of the body such as the bottoms of the feet can be particularly troublesome as it can reduce the mobility of the patient. For example a Total Contact Cast (TCC), Charcot Restraint Orthotic Walker (CROW) or other therapeutic footwear can reduce mobility. The reduction in mobility then leads to further medical problems. This is known in medical circles as a downward spiral.

[0013] A common approach to reducing localized pressure load is the use of a material such as shaped foam to redistribute the pressure load to another area of the body. Unfortunately many materials such as certain types of foam can have a very high coefficient of friction, especially when wet. Unappreciated by medical professionals is that while they may be reducing the pressure load locally they may be inadvertently increasing friction and shear loads.

[0014] In fact pressure loads can be surprisingly well tolerated by the skin and underlying tissue, unless the load becomes very high. This can be especially true when the pressure loads are of short enough duration to avoid occlusion of blood flow in the underlying tissue. Shear on the other hand can be more problematic. [0015] Even low to moderate dynamic shear loadings can be very damaging when the number of repetitions is high. Worse, tissue damage can occur in just a few repetitions when the shear load is high. Shear loadings by definition can be very distortional and cause tearing in biological tissues. A blister can be nothing more than tears in a layer of the skin which are then filled with fluid.

[0016] Static shear loads are also a problem. For example a person who is comatose or suffers from paralysis, even if positioned carefully, may experience high static shear stresses in some tissues. These shear stresses can stretch, weaken and eventually tear tissue microstructures. Shear stresses can also occlude blood flow much more easily than can pressure loads alone. The occlusion of blood flow can lead to damage of tissue.

[0017] If an area is "bony," minimizing friction becomes more important. In bony areas the tissue underlying the skin is thinner and shear stresses are more concentrated than in an area with a greater amount of soft tissue. These bony areas are much less tolerant of high shear stresses and much more susceptible to skin and tissue damage. This is true in the case of both static and dynamic loadings. Often these "bony" areas, also known as bony prominences, have highly contoured surfaces. These highly contoured surfaces can be reflected in the configuration of footwear, insoles, orthotic and prosthetic devices. Typical areas of bony prominences are: the bones in the heel, the elbow, shoulder blades, the head, toes, sacrum, coccyx, ischial tuberosities and the greater trochanters. However, other areas may also have bony prominences especially in persons with amputations or deformities.

[0018] Reduction of shear and friction can prevent skin and tissue damage. However, friction also performs the valuable function of adding to stability, control and/or suspension. Friction can be especially valuable in aiding walking stability and the suspension of limbs in prosthetic sockets. Some materials are poorly suited for preventing tissue damage. Foam materials which bear on the skin have proven to be especially poor choices from the standpoint of friction and shear.

[0019] Many prior art devices are available that attempt to protect or heal tissue. Most are not low friction. [0020] For example Moleskin patches can be used to cover corns and calluses. Unfortunately Moleskin patches have a relatively high CoF against the skin. J. Martin Carlson "Functional Limitations From Pain Caused by Repetitive Loading on the Skin: A Review and Discussion for Practioners, With New Data for Limiting Friction Loads" JPO Journal of Prosthetics and Orthotics (Nov 2006) 96. Additionally these patches can have problems conforming to highly contoured surfaces such as around bony prominences.

[0021] Amputees have attempted to use cotton, wool or foam liners to reduce friction where artificial limbs contact the skin. These liners do not always have a low coefficient of friction against the skin, particularly when damp. The use of liners additionally can have the downside of reducing friction over a wide area which can negatively impact stability, control and/or suspension.

[0022] Persons suffering from diabetes have used socks designed to reduce friction. These socks reduce friction over a large area while attempting to balance the friction required for stability and control during walking. The result is the use of materials that are much higher friction than optimal for tissue protection or healing. Further the low friction materials in socks can become very high friction when damp.

[0023] Creams and oils have also been used to reduce friction. Unfortunately they tend to reduce friction over a wide area and degrade stability and control, especially in use on the feet. After a period of use creams and oils tend to "dry up" and can actually have the undesirable effect of increasing the coefficient of friction which leads to further tissue damage.

[0024] Gel inserts for prosthetic sockets and footwear insoles are also available and can reduce frictional and shear loads only to a limited extent. These inserts are typically very thin and can have limited effectiveness as they can only accommodate limited motions before they reach the limit of their travel. Thicker gel inserts become unattractive due to weight and bulk.

[0025] In the prior art there have been some efforts to reduce friction by reducing the CoF. Prior art devices can work well in some applications. For example prior art patches with a very thin layer of film material can work well on flatter surfaces, such as surfaces found on some standard footwear insoles. Many prosthetic devices, orthotic devices and the human body, however, often have highly contoured surfaces that these patches have difficulty accommodating. This is especially true in the highly contoured areas around bony prominences where friction and shear relief can be needed most.

[0026] Applying a prior art patch to a highly contoured surface often results in the formation of wrinkles on the patch. For example wrinkles tend to form when the prior art patch is applied to a highly contoured surface approximating a partial sphere of radius about 5 inches or less. A wrinkled prior art patch can be a problem functionally as it can have greater friction in the areas of wrinkling. A wrinkled prior art patch with a high coefficient of friction may have the unexpected result of increasing frictional and shear loads.

[0027] Prior art patches with wrinkles also can have poor aesthetic qualities. End users tend to perceive wrinkled prior art patches as incorrectly or poorly applied. Poor aesthetics and degraded performance tend to cause users, including medical professionals, to forgo application of prior art patches.

[0028] Prior art patches tend to wrinkle and cause a great deal of difficulty in the fabrication of orthotic and prosthetic devices. Often prior art patches wrinkle so badly when applied that they must be removed leaving no protection from damaging friction and shear loads. Various methods of applying prior art patches, including ironing, to highly contoured surfaces have been attempted, with limited success. Prior art patches can be cut into small strips or have wrinkles cut and flattened to help the patch conform better to highly contoured surfaces. These methods can be difficult, time consuming and leaves edges in the areas needing the greatest friction reduction.

[0029] Unfortunately highly contoured surfaces are often in areas most in need of friction management. A patch that could be placed on a highly contoured surface without wrinkling would meet a long felt need of users of footwear, orthotics and prosthetics.

SUMMARY OF THE INVENTION

[0030] The present invention relates to using a layer of material that has very low friction to provide an interface with a support surface. The support surface normally would support the skin either directly or through a covering, such as sock fabric. The present invention provides a low friction interface even if a support surface is highly contoured. A layer of low-friction material could be placed, preferably, on the surface of the object that bears on the skin and faces the skin, although applying the layer with an adhesive directly on the skin is also contemplated. The purpose of the low friction material is to lower the frictional loads that the surface of the object can exert against the skin.

[0031] The use of one or more intervening layers is contemplated in the present invention. Layers such as a sock or sheet placed between the skin and the surface of an object do not adversely affect the performance.

[0032] The patch of the present invention has compound curvature. A small compound curved patch may be pre-cut or custom cut to desired size. The compound curved patch can have a pressure sensitive adhesive on one surface. An adhesive layer, foam backing layer or stretch fabric backing can be bonded to the low friction material. A release liner can be placed upon the exposed adhesive. Many types of release liners can be used but a polyethylene release liner could be used due to its ability to easily conform to a compound curve. When a release liner is removed, the compound curved patch can be placed on the surface of the skin or on an object that bears on the skin.

[0033] The compound curved patch could be configured in many ways. For example a compound curved patch could be small so as to cover an area of damaged tissue on a toe or large enough to cover a bed mattress or wheelchair seat. A compound curved patch may have one or more compound curves, especially when configured for placement on a larger surface such as a wheelchair seat.

[0034] Polytetrafluoroethylene (PTFE) and some other low friction materials may behave as ductile materials; these materials can exhibit both elastic and plastic deformation characteristics. A material that is deformed plastically does not return to its original shape but undergoes irreversible deformation retaining its deformed shape. It is possible to plastically deform a low friction material, such as PTFE, so that the low friction material will retain its deformed shape.

[0035] It is also possible to plastically deform more than one material such that they will retain their deformed shape. One or more materials can be deformed to create a compound curved patch. Unlike the prior art patches, a compound curved patch can be less susceptible to wrinkling.

[0036] Compound curved patches can have a differing number of layers. The present invention can have a layer of PTFE bonded to a fabric layer. The fabric layer can be a somewhat elastic, flexible material such as Lycra or a Lycra blend. One side of the fabric can be covered with a pressure sensitive adhesive and a release liner.

[0037] Using a pressure sensitive adhesive layer with a release liner or a fabric backing may not always be preferable. A compound curved patch might be bonded to an object by another means. One example would be the use of a dry melt adhesive to bond PTFE to a foam footwear insole. Another example would be the use of a pressure sensitive adhesive placed directly on a PTFE layer.

[0038] A thermoforming process can be used to plastically deform a patch and create the desired compound curvature. In one process a mold can be used during thermoforming. A mold can be made from many different materials, for example the mold could be a plaster model of a foot or a prosthetic device. The mold could also be made from other materials such as plastic, wood, steel or aluminum as needed.

[0039] The materials that make up the patch can be supported approximately around their perimeter during a thermoforming process. A material holder can be used to support the patch materials around their perimeter. The material holder could be configured to have many shapes and/or be made of differing materials such as plastic or aluminum.

[0040] The material holder can be two concentric rings approximately seven inches in diameter, but could be almost any diameter. For example the material holder might be two inches in diameter or 2 yards in diameter. A material holder closely configured to the desired patch size can reduce material waste. The concentric rings of the material holder can be designed such that the layers of the patch are supported between the outside diameter of the first ring and the inside diameter of the second ring. The material holder can support the patch materials in a manner similar to how a needlepoint hoop supports needlepoint fabric. The compound curved patch materials could be supported during the forming process by other means. For example, materials in the compound curved patch could be supported by squeezing them between the bottom surface of a first material holder and a top surface of a second material holder.

[0041] The compound curved patch materials can be heated during the thermoforming process to a temperature that allows the materials to easily plastically deform. Alternatively the materials of the patch could be heated separately and then assembled into a patch. Temperatures between 200°F and 400°F could be used depending on the materials used in the patch. Some release liners start to degrade above 300°F. In one example the materials of the patch can be heated at 300°F using hot air. A patch using PTFE as the low friction material and using other higher temperature materials may heated at a higher temperature, for example 550°F. The disclosed temperatures are not intended to serve as a limitation but only as a guide to enable one skilled in the art to easily thermoform patches.

[0042] The materials of the compound curved patch can be heated before or during the deformation process. One method of heating the materials in the compound curved patch can be to heat the mold itself and then stretch the materials over the heated mold. Another method could be to heat the materials by radiant heat, convection or adding a layer of heated thermal material to the forming process.

[0043] A vacuum process can be used to draw the compound curved patch materials to the shape of a mold. The process of drawing the compound curved patch materials to the mold causes plastic deformation in the materials. After cooling the compound curved patch materials retain approximately the shape of the mold. Other methods of deforming the compound curved patch materials can also be used. For example a compliant rubber stamp or pressure chamber could be used to deform the compound curved patch materials over a mold.

[0044] The compound curved patch materials could be deformed by a mold with two halves. A mold with two halves may be configured such that when the mold halves come together only a thin space exists between them. The space between the mold halves could be approximately the same as the thickness as the compound curved patch materials being formed. When compound curved patch materials are sandwiched between mold halves the materials can deform plastically. [0045] It is contemplated that the compound curved patch materials could be deformed by many different processes. For example using a rigid mold is not required, the materials could be deformed using a high pressure gas in a process similar to blow molding.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIG. 1 is a plan view of a layer of materials according the present invention.

[0047] FIG. 2 is a sectional view taken on line 2-2 in FIG. 1 showing the layers used.

[0048] FIG. 3 is a sectional view according to the present invention.

[0049] FIG. 4 is a perspective view with shading showing a highly contoured surface in an orthotic device.

[0050] FIG. 5 is a sectional view showing a patch with compound curvature according to the present invention and an orthotic device.

[0051] FIG. 6 is a plan view of a prior art low friction patch placed on a highly contoured surface.

[0052] FIG. 7 is a plan view of a compound curved patch according to the present invention placed on a highly contoured surface.

[0053] FIG. 8 is perspective view showing a foot and ankle indicating areas of sensitive skin.

[0054] FIG. 9 is a sectional view of a foot in footwear showing possible placement of the present invention.

[0055] FIG. 10 is a plan view according to the present invention.

[0056] FIG. 11 is an exploded sectional view taken on line 11-11 in FIG.10 showing the layers used.

[0057] FIG. 12 is an exploded sectional view according to the present invention.

[0058] FIG. 13 is a plan view according to the present invention.

[0059] FIG. 14 is a sectional view taken on line 14-14 in FIG.13 showing the layers used.

[0060] FIG. 15 is a plan view according to the present invention.

[0061] FIG. 16 is a sectional view taken on line 16-16 in FIG.15 showing the layers used.

[0062] FIG. 17 is a perspective view according to the present invention. DETAILED DECRIPTION OF THE PREFERRED EMBODIMENTS

[0063] FIGS. 1 and 2 illustrate a simple form of the invention which includes a composite sheet 10 of suitable size which can be used to cut into patches or pieces with a compound curved area 26. The purpose of the compound curved area 26 is to cover/engage protuberances that have come under or may come under load or stress.

[0064] By protuberance is meant a lump, nodulation, outgrowth, bulge, prominence, projection, or protrusion that may be found on the human body. Such protuberances are typically covered with a skin portion that may come under load or stress due to friction or shear forces or both by engaging a surface of an object.

[0065] By compound curved shape is meant that the patch has been physically conformed to a three dimensional surface having curvatures defined by at least two radii. The center of the different radii being located in any one of the three dimensions. The compound curved shape conforms generally to the protuberance without wrinkles or folds between the compound curved shape and the protuberance.

[0066] The composite sheet 10 can include a thin layer of PTFE as a low friction material 20. The layer of PTFE in this example can be approximately 3 mils in thickness.

[0067] The low friction material 20 can be bonded to a thin fabric layer 22. In this embodiment the fabric layer 22 can be a Lycra of approximately 5 mils thickness. The fabric layer 22 can be made from any number of materials including a non-woven cellulose based material made from fifty percent wood pulp and fifty percent polyester. The fabric layer 22 can be bonded to the low friction material 20 by an adhesive 21. In this embodiment the adhesive 21 can be a dry melt adhesive. The adhesive 21 could also be many other adhesives including a pressure sensitive adhesive.

[0068] The sheet 10 can be used for cutting out various configurations of patches with a compound curved area 26, such as shown in dotted lines at 15. Compound curved patches can be configured for use with various devices or parts of the body of a living being. Sheet 10 can be used in large areas or can be cut for small areas as desired. A pressure sensitive adhesive 23 with a release liner 24 can be placed on the compound curved patch. A release liner 24, such as Permaprint MAC-IP2000 made by the MACtac Company, can be generally conformed to the compound curved area 26.

[0069] A compound curved patch may be placed on an object with the low friction material 20 facing the skin. The compound curved patch may be placed on a number of surfaces such as a footwear insole, orthotic or prosthetic device. The compound curved area 26 can be located proximate a highly contoured surface on the body of a living being. The purpose of applying the compound curved patch is to lower the frictional loads an object can exert against the skin. The compound curved patch with compound curved area 26 does not need to have a certain number of layers.

[0070] FIG. 3 shows an embodiment of the current invention with two layers. A compound curved patch 30 comprises a layer of low friction material 31 and a layer of adhesive 32. It is further contemplated in another embodiment of the current invention only one low friction layer could be used.

[0071] FIG. 4 shows an orthotic device 40 with a highly contoured surface 41. A compound curved patch could be placed on the highly contoured surface 41 of the orthotic device 40.

[0072] FIG. 5 is a sectional view showing a compound curved patch 53 and an orthotic device 52. In this embodiment the compound curved patch 53 can be configured in the shape of a partial sphere having a first radius 54. The compound curved patch 53 can be placed on a prosthetic or orthotic device 52.

[0073] The prosthetic or orthotic device 52 has a highly contoured surface. In this example the highly contoured surface of the prosthetic or orthotic device 52 approximates a partial sphere with a second radius 55. The second radius 55 is greater than the first radius 54. The compound curved patch 53 generally has a smaller cross sectional radius than the prosthetic or orthotic device 52 on which it is placed.

[0074] The compound curved patch 53 has a low friction layer 50 made from PTFE film. A second layer 51 can be a pressure sensitive adhesive. In this example the compound curved patch 53 is configured to have a smaller curvature than the prosthetic or orthotic device 52, i.e., the compound curved patch 53 has a smaller cross sectional first radius 54 than the prosthetic or orthotic device 52 second radius 55. The difference in curvature between the compound curved patch 53 and the prosthetic or orthotic device 52 greatly reduces wrinkling of compound curved patch 53 after placement.

[0075] A compound curved patch according to the present invention does not need to have a smaller radius in all cross sections than the surface onto which it is to be placed. It is only necessary that a compound curved patch generally have a smaller or equal curvature than the surface to which it is to be placed for the compound curved patch to remain wrinkle free after application.

[0076] Materials with thin walls, such as thin layers of PTFE, are susceptible to buckling and the formation of wrinkles. Thin flat prior art patches 60 are also susceptible to the same buckling or wrinkling behavior. FIG.6 shows a flat prior art patch 60 placed on a highly contoured surface. The surface 62 of prior art patch 60 tends to buckle and form wrinkles 61.

[0077] FIG. 7 shows a compound curve patch 70 placed on a highly contoured surface. Before application the compound curved patch 70 had a smaller curvature than the surface on which it was placed. The surface 71 of compound curved patch 70 remains wrinkle free after application.

[0078] The compound curved patch may take various configurations to suit different applications. For example a compound curved patch can be cut to an oval shape. The compound curved patch could also be configured to have a slightly smaller curvature than a prosthetic or orthotic device.

[0079] Compound curved patches can also be configured for application to surfaces having different highly contoured surfaces. For example differently sized footwear can have various highly contoured surfaces. A compound curved patch could be configured for said footwear. One method of configuring a compound curved patch for application to various highly contoured surfaces can be to assure that the compound curved patch has a smaller amount of curvature than any surface on which it would be placed.

[0080] FIG. 8 shows a human foot 80 with areas of sensitive skin 81, 82 on the heel 84 and the toe 83. The present invention could be configured to provide a low friction surface with compound curvature for reducing shear and friction loads proximate a toe 83 or heel 84. For example a compound curved patch 30 with a low friction surface 31 could be configured to fit proximate an area of sensitive skin 81.

[0081] FIG. 9 shows configurations of the present invention. Bony prominences can be located in areas proximate the metatarsal heads 98, heel bone 94 and bones in the toe 95, 97. It is contemplated that the present invention could reduce shear and friction loads in highly contoured areas such as around a bony prominence in the heel 93. A compound curve patch 99 could be configured to reduce shear and friction loads proximate a bony prominence in the heel 93. A compound curved patch 96 could also be configured to reduce shear and friction loads proximate bony prominences associated with the bones in the toes 95, 97.

[0082] FIG. 10 illustrates a compound curved patch 100 in a rectangular configuration. An exploded section view of compound curved patch 100 is shown in FIG. 11. FIG. 10 omits release liner layer 103. In this embodiment the low friction layer 101 has compound curvature configured to accommodate features of a living being. The compound curved patch 100 shown in FIG. 10 could be placed over an area of sensitive skin 82.

[0083] The compound curved patch 100 comprises a low friction layer 101, such as PTFE, bonded to a foam layer 105. The foam layer 105 could be substantially thicker than the low friction layer 101. The low friction layer 101 can be bonded to the foam layer 105 by an adhesive 104. The foam layer 105 could be one quarter inch thick, but could be practically any thickness desired.

[0084] A pressure sensitive adhesive layer 102 can be placed, on the periphery of the top surface of the compound curved patch 100 as shown in FIG. 10. A release liner layer 103 may overlay the adhesive layer 102. When placed proximate an area of sensitive skin, the low friction layer 101 reduces shear and friction loads against the skin. The pressure sensitive adhesive 102 in this embodiment can be in contact with the skin.

[0085] FIG. 12 shows an exploded sectional view of an embodiment of the present invention. A low friction layer 120 having compound curvature can be bonded to a foam layer 123 by an adhesive 122. The low friction layer 120 could be ultra high molecular weight polyethylene or PTFE. Low friction layer 120 provides a low friction surface for reducing shear and friction loads against the skin. The low friction layer 120 has compound curvature that can be configured to accommodate highly contoured surfaces on the body of a living being.

[0086] In this embodiment adhesive 122 could be a dry melt adhesive. Foam layer 123 can have a pressure sensitive adhesive 124 and a release liner layer 125 attached. Adhesive layer 124 can be configured for attachment to a surface other than the skin, for example footwear, an orthotic or prosthetic device. The pressure sensitive adhesive 124 could alternatively be configured for attachment to the skin. In this embodiment the pressure sensitive adhesive 124 can extend across the foam layer 123.

[0087] FIGS. 13 and 14 show another embodiment of the present invention. In this embodiment the invention can be configured to fit footwear 92 shown in FIG. 9. A compound curved patch 135 can be configured to fit proximate the heel between footwear 92 and a foot. A low friction material layer 130 can be bonded by an adhesive layer 131 to foam layer 132. The low friction material 130 can be placed proximate a heel.

[0088] Another embodiment of the present invention, shown in FIG. 15 can be a compound curved patch 160 configured to fit footwear 92 and reduce shear and friction loads against the toes. The compound curved patch 160 can be configured to fit proximate the toes between the footwear 92 of a living being and a foot. Compound curved patch 160 could be configured with layers similar to the previous embodiments.

[0089] Compound curved patch 160 can have a low friction material layer 165 bonded to foam 163 by a dry melt adhesive 164. A pressure sensitive adhesive 162 can be configured to help compound curved patch 160 maintain position in footwear 92. A release liner layer 161 can cover a pressure sensitive adhesive 162. The release liner layer 161 has been omitted from FIG. 15.

[0090] Although the embodiment in FIG. 16 can have five layers, a different number of layers could be used. Additional rigidity can help retain the shape and/or position of compound curved patch 160 proximate footwear 92. A thin layer of a more rigid material such as polypropylene could be bonded to the foam material 163 to provide additional rigidity for the compound curved patch 160. Compound curved patch 160 could also be configured with additional rigidity by other methods such as using more rigid foam material 163.

[0091] Fig. 17 shows another embodiment of the present invention. This embodiment can be a compound curved patch 170 configured to reduce shear and friction loads against a toe 83. In this embodiment a low friction layer 172 with compound curvature can be bonded to foam 171 by an adhesive. In this embodiment a dry melt adhesive could be used. The patch 170 can be configured to slip over the distal end of toe 83. The purpose of the patch 170 can be to relieve the frictional loads on a portion of the skin. For example patch 170 could reduce frictional loads against sensitive skin 82 on a toe 83.

[0092] Compound curved patch 170 could be configured in many different ways. The compound curved patch 170 could be configured with different layers such that the low friction material 172 faced away from the skin and the foam 171 was proximate the skin. The compound curved patch 170 could also be configured with perforations, notches, holes, etc. as needed.

[0093] The present invention also encompasses the following. A film with a compound curve is plastically deformed; is positioned proximate a part of the body with a highly contoured surface; and curvature of the film is less than the curvature of the part of the body.

[0094] Many other configurations for compound curved patches are conceivable. Low friction materials of various dimensions, shapes, and locations could be employed. For example, the low friction material can be configured for other people or for animals other than humans. Also, different areas of sensitive skin and/or damaged skin than those depicted above may exist. In such instances, low friction materials can be configured to meet the needs of the person or animal. These variations and many others can be within the scope of the invention.

[0095] The present invention should not be considered limited to the particular examples described above, but rather should be understood to cover all aspects of the invention as fairly set out in the claims arising from this application. For example, while suitable sizes, materials, fasteners, and the like have been disclosed in the above discussion, it should be appreciated that these are provided by way of example and not of limitation as a number of other sizes, materials, fasteners, and so forth may be used without departing from the invention. Various modifications as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the present specifications. The claims, which arise from this application, are intended to cover such modifications and structures. The present invention can be configured to reduce friction and shear loads against the skin, including sensitive and/or damaged skin.