Abstract:
A cast or support assembly includes inner double knit padding material in which the outer layer is woven or knit to have substantial size openings, while the inner layer of the double knit material to be located against the skin of the patient is more closely woven or knit. Additional casting fabric is also provided, with this casting fabric being impregnated with water hardenable material. The outer casting fabric may include openings extending through it, so that the entire cast assembly has ventilation openings allowing air circulation to accomplish rapid drying following wetting of the assembly by sweat, rain, or by swimming, for example.

Description:
FIELD OF THE INVENTION 
   This invention relates to orthopedic casts or supports. 
   BACKGROUND OF THE INVENTION 
   Concerning prior work of others, reference is made to U.S. Pat. No. 5,334,442, granted Aug. 2, 1994, which discloses “triple layer” fabric portions adhered to both sides of a pliant sheet impregnated with water hardenable material. However, this proposed construction appears to be relatively complex, will be costly to produce, and the construction precludes uses where overlapping bonding of the casting material is appropriate. Reference is also made to U.S. Pat. No. 5,807,295, in which the possibility of using double knit material as an undercast padding is mentioned. However, no constructional details or specific information is provided. 
   Orthopedic casts or supports for immobilization of injuries normally include an absorbant soft padding material next to the skin and stiff or rigid outer casting material. Because casts are normally kept on for several weeks, they may become damp or wet from the cast application, sweat, rain, or from swimming, as examples. When the inner padding is wet for long periods of time, it is harmful and irritating to the patient. In severe cases, maceration of the skin can occur. 
   INVENTION SUMMARY 
   Accordingly, a principal object of the invention is to provide a quick drying cast system which will readily permit drying, following sweating or wetting of the cast by rain or swimming, as examples. 
   In accordance with one illustrative embodiment of the invention, a cast padding is formed of double knit type material with a relative close weave or knit on the side to face the skin, and a relatively open weave or knit on the side away from the skin, for increased air circulation. The double knit type construction provides open areas underneath the hardened casting material for air to circulate, resulting in quicker and more efficient drying of both the cast and cast padding. These open spaces also allow the water to easily flow out of the padding, meaning that the double knit construction does not hold as much water initially as do many of the more traditional padding materials like foam, felt, batting, etc. This ability to allow water to flow out rapidly, in combination with the air circulation after application, results in a finished cast assembly that will have a much quicker drying time than traditional cast applications. In-house drying tests have shown that using spacer material in place of cast padding allows a traditional cast to dry out approximately twice as fast as the commonly used synthetic padding. The spacer cast padding may be supplied in one of three different forms: (1) in a tubular configuration of various sizes, (2) as blanks, or (3) as rolls with various widths. In a tubular configuration the injured part of the body, such as a forearm, may be slid into the tube or sleeve much the same way as stockinette is currently applied, and a hardenable material applied over it. Because the spacer material has its own intrinsic padding properties, there is no need for additional moisture absorbing padding as with traditional casting methods. In roll form, the double knit padding can be continuously rolled around the injured anatomy in an overlapping fashion very similar to the manner in which traditional cotton or synthetic cast padding is currently applied. The material may also be cut into a shaped blank which has been designed for a specific portion of the anatomy, and this blank is placed on the body and trimmed if necessary prior to the application of the hardenable cast material. 
   The hardenable material may be of any conventional type; but preferably has openings in it to facilitate additional air circulation. The outer hardenable material may be a blank of double knit material and/or a single-layered knit tape, both of which would be impregnated with a known water hardenable material, such as urethane, and both of which would preferably have holes through the material for air circulation, as noted above. It is again noted that conventional casting tape may be employed by itself around the double knit padding; and that a blank, perhaps with a thumb hole, could also be used by itself as the outer casting material. 
   Instead of water activated hardening material, other hardening materials may be employed, such as a two part system in which hardening occurs soon after mixing the two materials and applying them to the casting fabric. 
   The double knit type padding preferably extends beyond the casting material around the edges thereof by a short distance such as ¼ inch or ⅛ inch, to avoid scratching or abrasion of the skin by the potentially rough edges of the hardened material. The padding material may be folded back over the edges and adhered to the cast material by lamination to create a finished and more comfortable edge. 
   When reference is made to double knit type material or “spacer” material in the present specification and claims, reference is made to material which has first and second spaced woven or knit fabric layers, with an openwork matrix of filaments extending between the two fabric layers, and with the filaments being integrally woven or knit into the two layers. To provide sufficient padding for the anatomy the spacer should have a thickness of between 0.100″ and 0.25″, preferably between 0.125″ and 0.15″. One preferred configuration for the matrix of filaments is an “X” or crisscrossing pattern of the interconnecting filaments. This will ensure that the fabric has a high resistance to compression and will maintain the distance between the first and second layers which is desirable for increasing the drying characteristics of the fabric. This configuration also ensures that the necessary padding and protection are provided for the anatomy under the hardened casting material. 
   It is also noted that the assembly of the double knit type padding with the breathable construction and outer casting material, also with holes or comprised of loosely woven or knit material, preferably does not have any further outer covering, so that circulation of air is promoted. If the hardenable material is made of a knit material with many holes, additional strength may need to be added by adding either single or multiple layers of additional casting material in select areas to act as stays and providing additional strength in only the necessary areas. 
   It is difficult to knit a spacer in a tubular form with the appropriate movement to account for the varying diameters of the anatomy. For example, it is necessary that the padding material have sufficient radial stretch to conform to the varying diameters of the hand, wrist, and forearm without wrinkling. An acceptable extensibility range is 50% to 200% with the ideal extensibility being approximately 100%. It is preferable that the radial extensibility be greater than the lengthwise extensibility. To increase the radial extension of the tubular configuration, it is possible to use spacer material in combination with other materials. It is preferable that this second material is one that has large extensibility. A single strip or multiple strips of the second material can be integrated into the tube, thereby creating multiple longitudinal strips of the spacer material and the second material. These strips would be sewn or bonded together to create a more flexible and conformable tube structure. Another method of increasing the bias movement of the spacer material to better conform to the anatomy is by knitting it into alternating thick and thin strips and then forming it into a tube. The thick portions would be double-knit and the thin portions would be a single-knit with the potential for larger movement. This type of construction can be achieved during a single manufacturing step, greatly reducing the labor associated with creating a tubular spacer over the above mentioned method of sewing in separate strips of material. 
   Increased conformability can also be achieved by contouring the tubular spacer to more closely replicate the curves of the anatomy. For example, for an upper extremity application, it is possible to vary the diameter of the tube by knitting the appropriate shape and/or sewing it into a specific pattern to allow for the differences between the hand, wrist and forearm. 
   Modifications to the tubular geometry can be made to provide for easier application. These can include, but are not limited to, creating a pre-made thumbhole or providing a thumb piece for receiving or supporting the thumb. 
   The padding can also be provided in the form of a blank shaped to fit the specific part of anatomy to be immobilized. The blank can be either knitted into the appropriate shape during manufacturing or cut to the shape after the material is manufactured. In one embodiment, this blank can be provided in an oversized shape and then trimmed to the correct dimensions during application in order to accommodate the most sizes of anatomy as possible with one size blank. 
   It is also possible, but not necessary, to supply the spacer material with a type of adhesive that will stick to either the skin or underlying stockinette. A similar layer of adhesive can be used on the opposite side of the padding, adjacent to the coated blank, to prevent the water hardenable resin from penetrating the padding while stored in the package. This same layer of adhesive can serve an additional role of attaching a covering material to the padding in the areas of the padding extending beyond the edge of the coated blank around the entire product. 
   The blank can also be supplied with varying thicknesses to provide more padding in strategic locations, i.e., over bony prominences. This additional padding can be achieved either during the knitting process or added as additional pieces after manufacturing and secured by adhesive or similar means. Additional padding can also be placed in an appropriate location prior to the application of the casting material to give the patient further protection from the cast saw during cast removal. Padding pieces may also be provided and placed over bony prominences, around the edges (i.e. thumbhole) or any other necessary areas to provide further protection for the user. 
   A third form that the spacer padding material can be provided in is in roll form. It would be applied by wrapping it around the part of the anatomy to be immobilized. Because of the thickness and resiliency of the spacer material, only one layer of wrapping would be necessary to provide sufficient padding. When using traditional padding, two to four layers must be used, resulting in a longer application time, more water retention and decreased air circulation. To decrease the bulk in the overlapping areas, the edges of the roll may by thermoformed or knitted to be lower in profile. 
   To increase the rapid drying characteristics of the double-knit cast padding, the fibers used to make the material can be made of any material and then coated with a hydrophobic material, such as SCOTCHGARD®. It is also possible to use a combination of different fibers in specific constructions within the spacer matrix and outer layers. Knitting with specific fiber combinations can create a wicking effect to pull the moisture away from the skin. This wicking action will increase the drying properties underneath a cast or support applied over the spacer cast padding. 
   Another feature of the invention allows for increasing air circulation under the cast by knitting or forming holes throughout the hardenable spacer material blank or any other casting material applied over the padding. 
   Other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description and from the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows tubular cast padding made of double knit type material in which the inner layer of the double knit material is more finely knit than the outer layer; 
       FIG. 2  is an enlarged view of the outer area of the padding shown in  FIG. 1 ; 
       FIG. 3  is an enlarged view of the more finely knit surface on the inside layer of the double knit type padding shown in  FIG. 1 ; 
       FIG. 4  is a perspective view of the assembly, showing the padding and casting material, with the patient&#39;s arm not shown; 
       FIG. 5  is a cross-sectional view taken along line  5 - 5  of  FIG. 4 ; 
       FIG. 6  shows a casting or support assembly as applied to the forearm of a patient; 
       FIG. 7  shows a padding blank formed of spacer or double knit type material; 
       FIG. 8  shows the blank of  FIG. 7  applied to the forearm of a patient; 
       FIG. 9  shows spacer cast padding in the form of a tape being wrapped onto the forearm of a patient; 
       FIG. 10  shows a tubular assembly of spacer material padding with strips of high bias movement alternated with the spacer material; and 
       FIG. 11  shows the padding assembly of  FIG. 10  mounted on the forearm of a patient. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring more particularly to the drawings,  FIG. 1  shows a tube  12  of double knit type material, which is intended for use as padding underneath a cast or support. As mentioned above, the double knit material involves an inner layer such as that shown in  FIG. 3  and at area  14  of  FIG. 1  of a finely knit or woven structure to provide a smooth surface next to the skin providing additional comfort for the patient. Incidentally, another method resulting in a smooth comfortable surface on the inner face of the padding material is to laminate a single layer of fabric to one surface of the double knit material. The outer surface of the double knit material, for example at area  16  and as shown enlarged in  FIG. 2 , is of a relatively coarse woven or knit structure and may have openings such as those shown at  18  in  FIG. 2 , to permit improved air circulation through the outer portion of the padding  12 . In one sample product, the openings  18  are approximately ⅛-inch long and are 1/16-inch in their lesser transverse dimension. The outer surface should have approximately 20% to 65% open area with about 40% open area being preferable. 
   It is further noted that the inner and outer layers  14  and  16  may be formed of different fibers. More specifically, the inner layer  14 , next to the skin, may be knit from hydrophobic fibers, and the outer layer  18  can be knit of hydrophilic fibers, thereby “attracting” the moisture from the skin and drawing it away from the hydrophobic layer  14 . An alternative configuration utilizes both hydrophobic and hydrophilic fibers in the same inner layer  14 . The hydrophobic fibers would be arranged closest to the skin and the hydrophilic fibers closest to the spacer yarns. This arrangement will draw any moisture away from the skin towards the spacer yarns to be rapidly evaporated. This configuration not only improves the quick dry feature of the padding, but also gives the patient a much dryer surface next to their skin in much less time. Hydrophobic materials which may be used include polyester and polypropylene; while hydrophilic materials would include fibers made up of a bundle of fine fibers, or polyester monofilaments which are etched to retain moisture. Incidentally, monofilament yarns will hold less water and dry out quicker than multifilament yarns. It is preferable that a quick dry padding be composed mainly of monofilament yarns or lower filament yarns for this reason. Incidentally, a “lower” filament yarn is a yarn formed of only one or only a few monofilaments so that it is still substantially hydrophobic. 
     FIG. 4  shows cast padding  12  and casting material  13  as they might appear in use, but without the inner forearm around which they would be mounted. The padding  12  may have a soft, finely woven or knit inner surface and a loosely woven or knit and/or apertured outer surface as described above in connection with  FIGS. 1-3 . The water hardenable casting material  13  may or may not be apertured as well, with the apertured configuration increasing air circulation and reducing drying time. Both of these materials  12  and  13  may be provided with a thumbhole  14 . 
   The padding  12  may be knit in a tubular manner, as shown in  FIG. 1 , or it may be formed as a flat blank of double knit type material and formed into tubular configurations by the stitching  17  as shown in  FIG. 4 . The edges of the casting material  13  may optionally be overlapped in the area  15 , and the overlapping layers laminate together in this area creating circumferential support. Concerning dimensions, the padding tube  12  may, for example, be approximately two inches in diameter, and may be any desired length. It may be provided in various diameters and lengths for snugly fitting over portions of the body such as the forearm or lower leg, for specific examples. Other methods of forming a flat blank into a tube include adhesive, ultrasonics, taping, or any other method of bonding the edges together. 
     FIG. 5  shows a cross section of the spacer or double knit type configuration of the padding  12  and the casting material  13  of  FIG. 4  through the line  5 - 5 . In practice, the padding  12  is initially applied to the injured part of the anatomy, such as the forearm; and subsequently the casting material  13  is dipped in water for activation and is applied over the padding  12 . It is also an option to dip both layers into the water at the same time and apply them both as a single unit. 
   Preferably, the casting material  13  may be initially flat and then may be wrapped around the injured portion of the anatomy; and can be optionally secured in place by overlapping, by VELCRO® type hook and loop fastening, by straps, or by a supplemental casting tape. 
   Now, turning to  FIG. 6  of the drawings, the double knit type padding material is shown at reference number  12  extending beyond the edges of the water hardenable type double knit material  22  as indicated at reference  36 ,  38 , and  40 . While finishing the cast, this excess padding can then be folded back over the edges of the material  22  to create a finished edge and provide the wearer with more comfort. The water hardenable double knit material  22  is a shaped blank with the thumbhole forming part of the blank, and it is dipped in water prior to being applied to the forearm  24 . The water hardenable material  22  becomes rigid to provide immobilization within the usual time period for standard casting products following application, such as 3 to 7 minutes. It is possible to make the water hardenable material  22  with apertures  26 , which extend all of the way through both layers of the water hardenable material to increase airflow and facilitate more rapid drying. 
   The casting material  22  may be held in place in any desired manner. For example, the edges  28  may overlap and bond to one another in these areas by lamination of the layers. Alternatively, a casting tape may be employed to wrap around the forearm and secure the casting material  22  in place. The water hardenable casting tape may also be provided with relatively large holes or apertures to permit air circulation through to the padding  12 . 
   As a further alternative, a single additional strip of either hardenable or non-hardenable casting material may be employed to bridge across the opening  34  between the two edges of the water hardenable blank  22 , with the activatable water hardenable material bonding and laminating the layers together. 
   Where casting tape is employed in addition to the water hardenable blank  22 , the openings  26  in the blank  22  may be relatively large to ensure adequate air circulation all the way from the outer surface of the water hardenable material through to the padding material  36 . However, even without openings in blank  22 , the spacer type padding provides significantly decreased drying time of the assembly because of the previously mentioned air circulation beneath the cast. The spaced apart layers of the double knit construction allow for the evaporation of water to occur not only through the inner and outer surfaces, but also through the two open ends of the finished cast. 
   Referring now to  FIGS. 7 and 8  of the drawings,  FIG. 7  shows a blank  52  of spacer or double knit type padding material for the forearm, with a thumb hole  54 . Also shown in  FIG. 7  are optional dots of pressure-sensitive adhesive  56  which may be present to help maintain the padding material in place on the anatomy by engaging with either the underlying stockinette or skin of the patient as the casting material is applied over it. Alternatively, if the pressure-sensitive adhesive is applied on the opposite side of the padding blank and extends over the entire surface, it serves the additional function of preventing the resin from the casting material from getting into and through the spacer padding. 
   In  FIG. 8 , the blank  52  is shown applied to the forearm  58  of a patient with the thumb  60  extending through the thumb hole  54 . The edges  62  and  64  are preferably trimmed, for example as indicated by the dashed line  66  so that the padding blank fits smoothly on the forearm of the patient, preferably without overlapping edges. Additional clips or tape may be used to secure the two free edges together without gaps. In use, the casting or splinting material would then be applied over this padding. 
     FIG. 9  shows another embodiment where a roll of spacer material undercast padding  70  is wrapped over the forearm  72  of a patient. The tape  70  may have a notch  73  adjacent the thumb  74  to make it fit more smoothly. Once wrapped, the free end of the tape may be secured in place by pressure sensitive adhesive, clips, etc., if necessary. In order to prevent bulk in the overlapping areas, the longitudinal edges  71  of the spacer padding may be thermoformed or knitted flat. 
   Referring now to  FIGS. 10 and 11 , an undercast padding assembly  78  is shown before and after application to a forearm respectively. It includes wide strips of spacer or double knit type material  80  and narrow, more stretchable strips  82  interleaved between the broader strips of spacer material. The strips  82  have large inherent bias movement or stretchable qualities so that the entire assembly will readily follow the shape of the anatomy, such as the forearm  84  as indicated in  FIG. 11 . The strips may be of LYCRA®, stockinette material or any other woven or knitted material with sufficient bias movement, for examples. It is further noted that the stretchable strips or areas  82  may be single layer knit materials formed integrally with the spacer or double material  80  as the material is knit or woven. 
   Concerning the double knit type material, it may be made on a double needle bar Raschel warp knitting machine, available from the Mayer Company of Germany. Double knit type fabrics knitted into a shape and/or of varying thickness can be made on machines available from H. Stoll GmbH &amp; Co. of Stollweg 1, D-72760 Reutlinger, Germany. Tubular double knit type material may be made on specialized circular knitting machines. 
   In the foregoing detailed description, one preferred embodiment of the invention is disclosed. Various modifications and somewhat different constructions may be employed without departing from the spirit and scope of the invention. Thus, for specific example, in some cases, the apertured casting blank need not be of double knit material but casting blanks or tapes of other apertured or very open knit fabrics may be employed, with the apertured double knit padding material underlying the casting material. It is also noted that, in addition to the forearm, the padding material and outer water hardenable material may be employed on casting assemblies for the foot or leg or other portions of the anatomy. It is further noted that instead of discrete holes, the outer layer of the double knit type padding material may be very coarsely woven or knit so that visible openings are present in the fabric; and the inner layer of the double knit padding may be somewhat more tightly woven or knit so that no visible openings are present through this inner layer. Concerning the filaments to be employed, a flat monofilament may be employed, as it has excellent hydrophobic properties. It is also contemplated that the undercast padding spacer material may be treated with anti-microbials, an anti-odor treatment or the like to minimize the odor beneath a cast once it has been worn for an extended period of time. Concerning activation of the casting material, this can be accomplished by dunking the casting material in water, either before or after application to the patient. Accordingly, the present invention is not limited to the precise embodiments shown in the drawings and described in detail hereinabove.