Thermoplastic cast having outstanding deformability and rigidity, and production method for same

Abstract

A thermoplastic cast, which is easy to reuse or implant, and a production method for same, are described. The cast includes a core material to which is attached polycaprolactone while being made in a mesh shape by the mutual crossing over and connecting of threads having a predetermined diameter, with the weaving of a plurality of strands of thin threads; and a structure which is made using a polycaprolactone composite and is formed so as to surround the outer part of the core material by means of insert injection. The patient experiences no discomfort despite the cast being structurally robust, because ventilation properties are improved due to the cast being formed in a mesh shape and because the structure, which is made using the polycaprolactone composite, is formed so as to surround the outer part of the core material by means of insert injection.

Claims

1. A thermoplastic cast for covering and fixing the body such as a fractured part of a patient, the thermoplastic cast comprising: a structure configured to cover at least a part of the fractured part of the patient, wherein: the structure includes a thermoplastic resin such that the structure can be deformed to conform the part of the fractured part by heating, the structure is formed as a mesh shaped body having a plurality of rhombus shaped air ventilation holes, the thermoplastic cast further comprises a core material for supporting the structure; and the core material defines a limit of deformation of the structure when the structure becomes plastic by heating, the core material has a thinner thickness than the structure and have a mesh shape, the core material is stretched when an external force is applied to the core material and returns to original shape when the external force is not applied to the core material, and the core material is deformable to a shape in which a long diagonal of at least one of the plurality of rhombus shaped air ventilation holes becomes a short diagonal of the at least one of the plurality of rhombus shaped air ventilation holes, and wherein the short diagonal of the at least one of the plurality of rhombus shaped air ventilation holes becomes the long diagonal of the at least one of the plurality of rhombus shaped air ventilation holes, and the core material configured to restrict the elongation of the structure in the lengthwise direction of each of the sides forming the at least one of the plurality of rhombus shaped air ventilation holes.

2. The thermoplastic cast of claim 1, wherein the structure is formed so as to have a cross section of which a height is larger relative to a width such that sufficient rigidity may be gained with respect to an external force or impact.

3. The thermoplastic cast of claim 1, wherein the structure includes a polycaprolactone composite.

4. The thermoplastic cast of claim 3, wherein a fiber reinforced glass fiber or a polyethylene terephthalate fiber is added to the polycaprolactone composite.

5. The thermoplastic cast of claim 3, wherein a polyethylene or a polyurethane is added to the polycaprolactone composite.

6. The thermoplastic cast of claim 3, wherein a nucleating agent made of a talc is added to the polycaprolactone composite.

7. The thermoplastic cast of claim 1, wherein: the core material is obtained by weaving a plurality of strands of thin yarn, and the core material includes polycaprolactone attached to the strands.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1a and 1b illustrate an embodiment of a conventional cast.

(2) FIGS. 2a and 2b illustrate another embodiment of a conventional cast.

(3) FIG. 3 is a cross-sectional view illustrating an embodiment of a thermoplastic cast according to the present invention.

(4) FIG. 4 is a photograph of an embodiment of a core material according to the present invention, produced in the shape of a mesh.

(5) FIG. 5 is a use state diagram illustrating an embodiment in which a mold, a guide cap, and a pressure applying member are used according to the present invention.

(6) FIG. 6 is a schematic diagram illustrating an embodiment in which a structure is formed through insert injection by using a mold on the outer portion of a core material to which is attached polycaprolactone, according to the present invention.

(7) FIGS. 7A and 7B are cross-sectional views illustrating an embodiment in which an outer cover is formed on a structure according to the present invention.

(8) FIG. 8 is a use state diagram illustrating an embodiment of a fixing member installed in a thermoplastic cast according to the present invention.

(9) FIG. 9 is a production flow chart illustrating the steps in the production method for a thermoplastic cast of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

(10) Hereinafter, the composition and effects of the present invention are described in greater detail through the accompanying drawings illustrating exemplary embodiments thereof.

(11) The present invention relates to a thermoplastic cast used for covering and thereby fixing or correcting a fractured part of a patient and, as illustrated in FIG. 3, the thermoplastic cast according to the present invention is composed of a core material 10 and a structure 20 formed so as to surround the outer portion of the core material and made of a polycaprolactone (PCL) composite.

(12) As illustrated in FIG. 3, the core material 10 is made in a mesh shape (mesh shaped body) by connecting threads, each of which has a predetermined diameter and is obtained by weaving a plurality of strands of thin yarn, and then attaching polycaprolactone on the outer portion of the threads by: impregnating a thermoplastic polycaprolactone with the mesh shaped body, using polyethylene terephthalate (PET) fiber of which the external circumferential surface is coated with polycaprolactone and melting the polycaprolactone coated part with heat, or melting the polycaprolactone fiber included in the mesh shaped body with heat. For this, a common yarn, a blended yarn in which polyethylene terephthalate fiber and polycaprolactone fiber are mixed, or the polyethylene terephthalate fiber of which the external circumferential surface is coated with polycaprolactone is used as the thread forming the mesh shaped body.

(13) In the present invention, as described above, the core material 10 is made of the thread which is composed of the plurality of strands, and thus may be freely formed into various forms, and is also light and not easily damaged.

(14) Moreover, as described above, in the present invention, when the thermoplastic polycaprolactone is impregnated with the mesh body, the polycaprolactone coated part of the polyethylene terephthalate fiber is melted, or the polycaprolactone fiber is melted with heat and then cooled, the mesh shaped body is stiffened by the polycaprolactone, which is attached to the outer portion of the thread, such that the shape can be maintained as it is, and even when an external force is applied from the outside, is not excessively stretched and easily returns to its original shape after being stretched to an appropriate length.

(15) On the external circumferential surface of the core material 10, the structure 20 is formed so as to surround the core material 10, and here, the structure 20 is composed of the polycaprolactone composite that has polycaprolactone as the main component, and due to such a composition, may be firmly coupled with the polycaprolactone that is attached to the external circumferential surface of the thread. Consequently separation or peeling due to differences in the material between the core material 10 and the structure 20 is prevented.

(16) Here, the structure 20 is formed so as to have a rectangular cross section of which the height is larger relative to the width such that sufficient rigidity is achieved with regard to an external force or impact.

(17) Also, as described above, the structure 20 is composed of the polycaprolactone composite, and such a polycaprolactone composite is composed of polycaprolactone, which is the main component, and an additive composed of fiber reinforced glass fiber or polyethylene terephthalate fiber. The strength of the structure 20 is enhanced by such an additive, and thus, since the width of the structure 20 may be reduced, the fraction of a rhombus shaped air ventilation hole is increased to improve the air-permeability, and it also becomes possible for the structure 20 to be lightweight.

(18) Moreover, polyethylene (PE) or polyurethane (PR) may also be added as an additive to the structure, and such polyethylene and polyurethane increases the time it takes for the structure 20 to be hardened and also improves the impact resistance such that sufficient time may be gained for the medical procedure of applying the cast on the affected area, and the structure also becomes robust with regard to external impact.

(19) As described above, in the cast of the present invention, since the core material 10 is composed of thread, elongation in the lengthwise direction of each of the sides forming the rhombus is restricted, but deformation of the rhombus (for example, a shape in which the long diagonal of the rhombus becomes the short diagonal, and the short diagonal becomes the long diagonal) is easily achieved such that a medical procedure is easily performed on a body part, and since the core material 10 is surrounded with the structure 20 made of the polycaprolactone composite, structural integrity may be achieved such that the body is robustly supported.

(20) An outer cover 30 may be formed/attached over the entire outer portion of the structure 20 or on an area thereof, and such an outer cover 30 is a rubber material and is formed through dipping, insert injection, or sheet fusion.

(21) The cast (1) formed as such an above-described structure is produced through a mesh shaped body forming step S100, a polycaprolactone attaching step S200, a core material laying step S300, a structure forming step S400, and an outer cover forming step S500, and the like, as illustrated in FIG. 9. Hereinafter, detailed description is given for each of the steps.

(22) (1) Mesh Shaped Body Forming Step S100

(23) This step is the step for forming the mesh shaped by, as illustrated in FIG. 4, mutually crossing over and connecting threads having a predetermined diameter, and here, the thread used in forming the mesh shaped body is the thread composed of the common yarn, the blended yarn in which polyethylene terephthalate fiber and polycaprolactone fiber are mixed, or the polyethylene terephthalate fiber of which the external circumferential surface is coated with polycaprolactone, and thus the binding force with the structure 20 composed of the polycaprolactone composite is improved. Description thereof will be given later.

(24) Also, it is desirable for the diameter of the thread, which forms the mesh shaped body while being in a state in which the plurality of strands of thin yarn are woven, to be 13 mm so as to have the appropriate strength and elasticity.

(25) (2) Polycaprolactone Attaching Step S200

(26) This step is the step for producing the core material 10, after the mesh shaped body composed of thread is produced through such an above-described mesh shaped body forming step S100, by placing such a mesh shaped body in a polycaprolactone impregnation tank to be impregnated with polycaprolactone, or by attaching polycaprolactone on the outer portion of the thread by applying heat to the mesh shaped body composed of the polyethylene terephthalate fiber of which the external circumferential surface is coated with polycaprolactone. Consequently, the strength of the core material 10 is improved while the core material 10 is able to maintain the form of the mesh shaped body such that the below-described structure forming step S400 may be easily performed.

(27) In the present invention, one of three methods is selected as the method for attaching polycaprolactone to the outer portion of the thread to produce the core material 10. The first method is the method for attaching polycaprolactone to the outer portion of the thread by dipping and impregnating the mesh shaped body composed of thread in the polycaprolactone impregnation tank which is holding a polycaprolactone solution dissolved by a solvent and is maintained at a constant temperature. The second method is the method for attaching polycaprolactone to the outer portion of the thread by applying heat to the mesh shaped body in a state in which the mesh shaped body composed of polyethylene terephthalate fiber of which the external circumferential surface is coated with polycaprolactone is inserted in a heating device such as a microwave oven to thereby melt the polycaprolactone coated on the outer portion of the polyethylene terephthalate fiber, and this method has an advantage in that polycaprolactone is more uniformly attached over the entirety of the outer portion of the thread when compared to the previous method of attaching polycaprolactone on the outer portion of the thread through impregnation. The third method is the method for attaching polycaprolactone on the outer portion of the thread by applying heat to the mesh shaped body in a state in which the mesh shaped body formed from polyethylene terephthalate fiber and polycaprolactone fiber are inserted in a heating device such as a microwave oven to thereby melt the polycaprolactone fiber.

(28) When polycaprolactone is attached to the outer portion of the thread through impregnation, the polycaprolactone solution used is that which is held in the polycaprolactone impregnation bath and diluted with a solvent such as tetrahydro furan (THF), and the like, and thus the polycaprolactone is dried while being easily percolated between the plurality of thin yarns forming the mesh shaped body such that the diameter of the mesh shaped body after being impregnated with polycaprolactone, that is, the cross section of the core material 10, is also uniform.

(29) It is desirable for the cross-sectional diameter of the mesh shaped body (core material) to be 25 mm when the polycaprolactone composite is attached to the inner and outer portions of the mesh shaped body having a cross-sectional diameter of 13 mm, and this enables the core material 10 to have an appropriate stiffness when cooled through the below-described cooling step S300 such that the core shape 10 maintains the mesh shape when performing the subsequent structure forming step S400 and is thus easily handled, and allows a binding performance to be gained with the structure 20 which is composed of the polycaprolactone composite that surrounds the outer portion of the core material.

(30) The polycaprolactone in the polycaprolactone composite attached to the outer portion of the thread is a thermoplastic resin that is easily softened in the temperature range of 5580 C. and has non-adhesive and crystalline properties at room temperature, and thus when the polycaprolactone composite is cooled by being attached to the inner and outer portions of the mesh shaped as described above, the shape of the mesh shaped body can be maintained at room temperature.

(31) (3) Core Material Shape Defining Step S300

(32) This step is the step for shaping into a defined shape the core material 10, which is unable to be maintained in the form of the mesh shaped body when undergoing the process of impregnation, and the like, and is thus deformed into an arbitrary shape, and through this step, the core material 10 may be easily placed inside of a mold.

(33) For example, in the case of attaching polycaprolactone on the outer portion of the thread through impregnation, when performing the polycaprolactone attaching step S200, after placing a solvent-diluted concentration of the polycaprolactone solution in the polycaprolactone impregnation bath which, as described above, is maintained in the temperature range of 4060 C., the mesh shaped body is dipped in this polycaprolactone impregnation bath to thereby attach the polycaprolactone. During this process, the mesh shaped body may be unable to maintain the original shape and thus be deformed into an arbitrary shape, and in this case, it is not easy to insert the core material 10 into the mold used for attaching the structure 20 on the outer portion of the core material.

(34) To overcome this, in the present invention, before inserting the core material 10 inside of the mold, the shape of the core material 10, which was deformed into an arbitrary shape, is defined by applying pressure to, and inserting, the core material 10 in a shape template 2 in which is formed a groove in the shape of a defined mesh shaped body as illustrated in FIG. 5, and for this, the shape template is provided with a guide cap 2A, in which a plurality of guiding protrusions are formed protruding upwardly to have a mesh shape, and a pressure applying member 2C disposed above the guide cap 2A and applying pressure to, and thereby pushing, the core material 10 toward the groove 2B in the shape template. Due to such a configuration, when the core material 10 is first placed on the guide cap 2A and the pressure applying member 2C is then lowered toward the shape template 2, the shape is defined when the core material 10 placed on the guide cap 2A moves downward by sliding along the guiding protrusions of the guide cap 2A to be placed inside of the shape template, and thereby, the core material 10 can be easily placed in the mold for attaching the structure 20 on the outer portion of the core material.

(35) Here, when the core material 10 to which is attached polycaprolactone on the outside thereof is stiffened, it may be very difficult to perform the shape defining operation, and thus in order to overcome this, it is desirable for the shape defining operation to be undertaken in a state in which flexibility is provided to the core material 10 by heating the core material 10 in a heater, and the like, before performing the shape defining operation.

(36) (4) Structure Forming Step S400

(37) This step is the step for inserting the core material having the defined shape in a mold for insert injection to form, by means of injection, the structure 20 composed of the polycaprolactone composite on the outer portion of the core material 10, so as to surround the core material 10.

(38) When the core material 10 is defined in the shape of a mesh through the above core material shape defining step S300, this core material 10 having the defined shape is placed inside of the mold for insert injection to form, by means of injection, the structure 20, which is composed of the polycaprolactone composite, on the outer portion of the core material 10 so as to surround the core material 10. For this, as illustrated in FIG. 6, in the present invention, a mold 3, inside of which is formed the groove 3A which is made in the same shape as the shape of the mesh shaped body, composed of a top/bottom pair is prepared, and in a state in which the core material 10 is placed inside of the groove 3A of the mold 3, the polycaprolactone composite, of which the main component is polycaprolactone, is injected (insert injection) such that the structure 20 made of the polycaprolactone composite surrounds the external circumferential surface of the core material 10. Here, as described above, the structure 20 has polycaprolactone, which is the same material as the core material 10, as the main component, and an additive such as fiber reinforced glass fiber or polyethylene terephthalate fiber, and the like, is mixed therein to further improve the strength, and polyethylene or polyurethane is added in order to gain sufficient time to perform the medical procedure for applying the cast, while also improving the impact resistance.

(39) Also, a nucleating agent including talc may be added to the polycaprolactone composite which forms the structure 20, and due to the addition of such a nucleating agent, crystallization of the polycaprolactone composite may be accelerated such that solidification of the polycaprolactone composite is quickly achieved during injection, and excessive crystallization of the polycaprolactone composite is prevented such that a uniform strength may be expected, and also the productivity is improved.

(40) The structure 20 which is formed through insert injection on the outer portion of the core material 10 is formed so as to have a rectangular cross section of which the height is larger relative to the width such that sufficient rigidity may be gained with respect to an external force or impact. Here, the structure 20 is formed to have a width in the range of 56 mm and a height in the range of 5.56.5 mm, and thereby the cast having sufficient rigidity and flexibility may be realized. Also, since the structure 20 is formed through insert injection using the mold 3 which, as described above, has a smooth surface, the structure 20 having a smooth surface is produced.

(41) Meanwhile, when the core material 10 is inserted and placed inside of the mold 3, the core material 10 may not be positioned in the center of the groove 3A formed in the mold 3 and instead be positioned toward one side or toward the bottom of the mold 3, and in this case, there is a concern that the polycaprolactone formed on the outer portion of the core material may not be formed to a uniform thickness, and thus it is desirable to form a spacer (not shown) in the shape of a protrusion in the groove 3A which is formed inside of the mold 3 such that the core material 10 may be positioned in the center of the groove 3A in the mold 3.

(42) Also, when the cast is applied to the affected area of the patient, according to the part on which the cast is applied, there may be a portion of the mesh shaped cast which is deformed to a greater degree relative to the other portions, and in this case, the portion at which the structures 20 mutually cross each other may not be realized as a flat surface and instead protrude in an upward or downward direction, and when protruding in a downward direction, the protruding portion may press the skin of the patient such that the patient feels discomfort. Thus, in the present invention, in order to prevent this, when forming the structure 20, an inwardly recessed groove is formed in the portion at which the mesh shaped structures 20 cross over with each other, or the thickness of the portion at which the structures 20 cross over with each other is formed to be relatively thinner, and here, the recessed groove may be formed by forming a protruding portion (not shown) in the mold 3 for forming the structure 20, and the structure of which the crossing portion of the structure 20 is relatively thinner may be realized by making the thickness of the portion in the mold which forms this portion relatively thinner.

(43) As above, in the present invention, since the structure 20 is formed using the mold through insert injection, the structure 20 having a uniform thickness may be quickly formed and is thus easily mass produced, and also, since by attaching polycaprolactone on the outer portion of the thread, the core material 10 having an unevenly shaped surface is surrounded by the structure 20 having a smooth surface, the discomfort felt by the patient may be relieved even when the cast 1 contacts the skin of the patient.

(44) (5) Other Cover Forming Step S500

(45) This step is the step for forming the outer cover 30 on the outer portion of the structure 20, and this step may be selectively performed as needed.

(46) By passing through the above structure forming step S400, the cast 1 having the smooth surface is produced and thus even when contacting the skin of the patient, the patient does not feel discomfort. However, since the structure 20 becomes hard after the cast is applied on the affected area of the patient and then cooled, the patient may feel discomfort, and thus, in the present invention, the outer cover 30 made of a rubber material may be further formed on the structure 20 to relieve the discomfort of the patient, and here, the outer cover 30 may be formed through the below two methods.

(47) As illustrated in FIG. 7A, the first method is the method for forming the outer cover 30 made of the rubber material on the entirety of all four surfaces of the structure 20, and here, the outer cover 30 is formed by dipping and then undipping the entirety of the structure 20 in a storage tank which holds a mixed solution of a binder and a rubber solution (dipping), by placing the structure 20 inside of the mold, such as in the structure forming step S400, and inserting the rubber which is in a liquid state on the external circumferential surface thereof (insert injection), or by installing a sheet made of rubber material on the outer portion of the structure 20 and then using heat to fuse the sheet made of rubber material to the structure 20 (sheet fusion).

(48) As illustrated in FIG. 7B, the second method is the method for forming the outer cover 30 on only the bottom surface of the structure 20, and here, among the four surfaces of the structure, only the bottom surface which contacts the skin of the patient is dipped in the storage tank that holds the mixed solution of binder and rubber solution and then undipped to form the outer cover 30, and when the outer cover 30 formed on the bottom surface of the structure 20 is formed in the shape of protrusions, ventilation may thereby be achieved.

(49) When the outer cover 30 made of the rubber material is formed, such as above, on the cast 1 of the present invention, the outer cover 30 acts as a cushioning material such that even when the cast directly contacts the skin of the patient, the pressure applied on the skin is reduced, and consequently the generation of pain due to pressure from the cast is prevented, and also, it is not necessary to install a separate skin protector, and the like, on the bottom of the cast 1.

(50) When applying the thermoplastic cast 1 of the present invention, which is formed to have a structure such as described above, on the affected area of the patient, the cast 1 which is at room temperature is first softened by heating in a heating device such as a hot water heater or a microwave oven and is thereby made into a freely deformable state, and then, after being applied so as to surround the affected area of the patient which is fractured or needs correcting, the cast 1 is gradually cooled to room temperature in a state in which both ends of the cast which are in contact with each other, are fixed by the cast 1 using a fixing member F as illustrated in FIG. 8, and thereby solidified to complete the application of the cast 1.

(51) Here, the fixing member F used for fixing both ends of the cast may be one of any configuration, including a clip-type or a buckle-type, that fixes both ends of the cast 1, but in order to allow an x-ray examination, and the like, to be performed while the cast 1 is being worn, is desirably made of a plastic material, instead of a metal material.

(52) Also, when it is necessary for the cast 1 to be removed from the affected area of the patient or be corrected, the cast may be removed from the affected area merely by removing the fixing member F installed on both ends and then spreading apart both ends of the cast 1, and thus disassembly is comparatively simple. Also, when reapplying the cast 1 to the affected area of the patient, the disassembled cast 1 may be reheated and softened, and then easily modified or reapplied by once again going through the above-described process for applying the cast 1.

(53) As described above, in the present invention the cast is formed to be mesh shaped such that ventilation is improved, and since the structure composed of the polycaprolactone composite is formed through insert injection so as to surround the outer portion of the core material, the cast is structurally robust while at the same time the patient does not feel discomfort, and since the structure is composed of thermoplastic material, the cast has the advantage of being able to be modified or reused as needed.