Method for manufacturing an implant, manufacturing a mold shell arrangement and using a mold shell arrangement

Abstract

Method for manufacturing an implant (400), the procedure comprises the following steps: - Introducing a product material into a mold shell arrangement (100) which is formed from a shell material, and - Creating the implant (400), characterized by the fact that as product material a mixture containing a polyol component, a polyisocyanate component and a blowing agent is used, which produces the implant (400) by means of a foam casting process and a melt-processable material is used as shell material and the melt-processable material contains a fluoropolymer.

Description

Application area and technical background

[0001] The invention relates to a method for manufacturing an implant. The method comprises the following steps: - Introducing a product material into a mold shell arrangement formed from a shell material, and - Creating the implant.

[0002] The invention further relates to the manufacture and use of a mold tray arrangement.

[0003] Generic processes are used, for example, to manufacture medical products such as meniscus implants. With medical products, it is particularly important that they have the exact desired shape and are free of residues. For example, such medical products are made of polyurethane (PUR).

[0004] In processes of this type, mold trays made of polytetrafluoroethylene (PTFE), also known under the brand name Teflon, are typically used. PTFE exhibits particularly advantageous resistance to chemical attack for this purpose. However, such mold trays must be manufactured using a complex process, typically involving the separate steps of pressing and sintering. This is because PTFE, in the form used in processes of this type, cannot be processed using the far less complex injection molding method. For economic reasons, these mold trays are therefore reusable and used to manufacture a variety of medical products.

[0005] Due to the aforementioned stringent requirements for medical products, it is essential to thoroughly clean PTFE molds after each use, removing even the smallest residues. In practice, this is very time-consuming, and experience has shown that after repeated use of a PTFE mold assembly, adequate cleaning can no longer be reliably achieved. In particular, after repeated use of PTFE mold assemblies, the problem arises that the manufactured products become increasingly difficult to demold and, especially, tend to stick together on the inner surface of the cavities formed by the mold assemblies.

[0006] Another problem with the use of PTFE molds is that, due to the complex manufacturing process and the associated high price of a single mold shell arrangement, they are not suitable for the economical production of different medical products in small quantities.

[0007] Furthermore, even PTFE molded shell arrangements are ultimately not wear-resistant.

[0008] A well-known alternative is the use of silicone mold assemblies. However, these have proven less suitable in practice because they quickly become brittle. Furthermore, there is a certain risk that silicone particles will detach during production and contaminate the manufactured products.

[0009] From DE 100 06 851 A1 a method for producing artificial skullcaps on a (meth)acrylate basis using a two-part casting mold is known.

[0010] A method for producing a foamed polymer molded part using a molding tool is known from EP 1 714 767 A2.

[0011] DE 20 2008 017 446 U1 relates to a two-part foam mold with shell-shaped plastic inserts.

[0012] DE 20 08 084 A discloses a two-part casting or drawing mold for the production of molded parts, in particular from polyurethane foam, wherein the casting or drawing mold consists of a melt-processable epoxy resin.

[0013] The subject of DE 39 00 809 A1 is a process for producing latex foam from a latex foam containing gelling, vulcanizing and processing aids.

[0014] Furthermore, a fluoropolymer based on modified polytetrafluoroethylene (PTFE) is known which can be processed from the melt ("The great freedom of fluoropolymers", Kunststoffe 10 / 2010, pages 232-234). Task and solution

[0015] It is therefore an object of the invention to provide a method for manufacturing an implant which enables more economical and flexible production. Furthermore, it is an object of the invention to provide a mold shell arrangement for use in a method according to the invention, as well as the use of a mold shell arrangement for use in a method according to the invention.

[0016] This is achieved according to the invention by a method according to claim 1, a manufacturing method for a mold tray arrangement according to claim 9, and the use of a mold tray arrangement according to claim 10. Exemplary embodiments of the invention are described, for example, in the respective dependent claims, which are hereby expressly incorporated into the description.

[0017] According to a first aspect, the invention relates to a method for manufacturing an implant. The method comprises the following steps: - Introducing a product material into a mold shell arrangement formed from a shell material, and - Creating the implant.

[0018] According to the invention, a meltable material is used as the shell material.

[0019] The inventive method enables the production of the mold shell assembly to be carried out using a significantly less complex process, such as injection molding. This considerably reduces the cost of a mold shell assembly. Consequently, the mold shell assemblies can be used as disposable mold shell assemblies, meaning they are used only to produce a single implant and then discarded. This eliminates the need for time-consuming cleaning steps between each use of the process. Furthermore, it allows for greater flexibility in accommodating different requirements regarding the shape of the implant, even for small production runs, without incurring excessive costs.Another advantage is the achievement of a consistent quality of the implant being manufactured, without impurities, especially in the form of detached shell material particles, being introduced into the implant during the manufacturing process.

[0020] In particular, the method is advantageously applicable for the production of a meniscus implant or an implant intended to replace other body parts or tissues.

[0021] The mold shell arrangement is preferably manufactured by injection molding. According to the invention, it is therefore preferred if the method further comprises a step for manufacturing the mold shell arrangement, wherein the mold shell arrangement is further preferably manufactured by injection molding.

[0022] Furthermore, the method preferably includes a step of inserting the mold shell assembly into a holder. Such a holder allows the mold shell assembly to be held in position during a manufacturing process. The holder can be a known design. This holder can be of a known type; for example, it can have a cavity for receiving the mold shell assembly, which is accessible by means of a removable cover. The holder can also be designed as a press, which, for example, uses manually operated screws, hydraulic cylinders, or other means to generate pressure in the form of compression of the mold shell assembly. The holder can also be designed to hold several mold shell assemblies simultaneously, thus enabling the production of multiple implants in a single pass.

[0023] Preferably, the mold shell assembly is tempered, particularly after being placed in a holder and before the implant is produced. Tempering can take place within a temperature range of 35 °C to 60 °C, preferably 40 °C to 55 °C, and particularly over a period of 0.5 to 2 hours.

[0024] The choice of shell material should ideally be based on the implant to be manufactured.

[0025] The melt-processable material contains a fluoropolymer. Surprisingly, it has been found that the use of a fluoropolymer-containing shell material or a fluoropolymer-containing mold shell arrangement is particularly suitable for the production of open-porous implants.

[0026] In particular, the melt-processable material may be in the form of a polymer compound or polymer blend containing a fluoropolymer.

[0027] In a further embodiment, the melt-processable material can contain the fluoropolymer as its main component. The term "main component" here means a fluoropolymer content of at least 50% by weight, based on the total weight of the shell material.

[0028] In a further embodiment, the melt-processable material can have a proportion of the fluoropolymer of 50 wt.% to 99.8 wt.%, in particular 50 wt.% to 90 wt.%, preferably 50 wt.% to 80 wt.%, more preferably 50 wt.% to 70 wt.%, based on the total weight of the melt-processable material.

[0029] The fluoropolymer is preferably selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene (TFE) copolymers and combinations, in particular blends, thereof.

[0030] The TFE copolymers mentioned in the previous paragraph may contain comonomer units selected from the group consisting of hexafluoropropylene units, perfluoroalkyl vinyl ether units, perfluoro-(2,2-dimethyl-1,3-dioxol) units, chlorotrifluoroethylene units and combinations thereof.

[0031] The comonomer units can have a minimum proportion of 0.2 mol%, based on the total weight of the fluoropolymer.

[0032] Preferably, the melt-processable material further comprises, i.e., in addition to the fluoropolymer, another, preferably non-fluorinated, polymer, which is preferably selected from the group consisting of polyphenylene sulfide (PPS), polyphenylene sulfone (PPSO2), polyamide (PA), polyimide (Pl), polyamide-imide (PAI), polyether-imide (PEI), derivatives thereof, copolymers thereof and combinations, in particular blends, thereof.

[0033] It has been shown in particular that in the case of a mixture containing PTFE and at least one of the polymers mentioned in the previous paragraph, the material properties of PTFE can be modified to such an extent that PTFE becomes melt-processable. This makes it possible to process a shell material whose main component is PTFE by injection molding, thereby achieving the advantages already mentioned above, especially simpler and more cost-effective production.

[0034] The melt-processable material may contain a proportion of the aforementioned additional polymer of a maximum of 30 wt.%, in particular a maximum of 20 wt.%, based on the total weight of the melt-processable material.

[0035] The melt-processable material, in particular the fluoropolymer mentioned in the preceding paragraphs, may in a further embodiment additionally contain additives, especially in the form of fillers. Suitable additives may be selected from the group consisting of boron nitride, silicon carbide, molybdenum disulfide, carbon fibers, glass beads, hollow glass spheres, glass fibers, carbon black, carbon particles, graphite, and combinations thereof.

[0036] A particularly preferred melt-processable material according to the invention is that known as Moldflon. ® Commercially distributed modified polytetrafluoroethylene. Regarding further characteristics and advantages of such a polytetrafluoroethylene, reference is made to DE 10 2009 018 636 A1, the disclosure content of which is incorporated by explicit reference into the present description.

[0037] The implant is produced using foam casting (reaction injection molding) or a reaction foam casting process.

[0038] The product material is a mixture containing a polyol component, a polyisocyanate component, and a blowing agent. The polyol component reacts with the polyisocyanate component in a nucleophilic polyaddition to form polyurethane, with the presence of the blowing agent leading to the formation of a polyurethane foam. For the purposes of this invention, a polyol component is understood to be an alcohol compound with two (diol component) or more hydroxyl groups. Similarly, a polyisocyanate component is understood to be an isocyanate compound with two (diisocyanate component) or more isocyanate groups.

[0039] The polyol component and / or the polyisocyanate component can be present as monomers, oligomers, and / or polymers. Furthermore, it is preferred that the polyol component and / or the polyisocyanate component are liquid or liquefiable, preferably within a temperature range of 20 °C to 45 °C, particularly 25 °C to 40 °C.

[0040] Suitable polyol components can be selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, trimethylolpropane, glycerin, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, polycaprolactonediol, polycaprolactonetriol, polyethylene glycol and mixtures thereof.

[0041] Suitable polyisocyanate components can be selected from the group consisting of diphenylmethane diisocyanate, toluene-2,4-diisocyanate, naphthylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-diisocyanatodicyclohexylmethane, butane diisocyanate, lysine diisocyanate and mixtures thereof.

[0042] Suitable propellants can be selected, for example, from the group consisting of water, carbon dioxide, air, nitrogen, nitrogen oxides, noble gases, fluorocarbons, carbamates, methylal or mixtures thereof.

[0043] If necessary, further components, in particular a fibrous component such as collagen-containing fibers, can be added to the mixture.

[0044] According to the invention, it is therefore preferred if the implant produced is made of foamed polyurethane (PUR). Foamed polyurethane, which is produced by means of a foaming process, has proven to be an advantageous material for use in implants. It is chemically resistant and is well accepted by the human or animal body. Furthermore, it advantageously allows for the open-pore structure described below.

[0045] The mold shell arrangement preferably creates an open-pore state of the implant surface during the implant fabrication process. This effect is typically based on an anti-adhesive surface of the mold shell arrangement, which can be achieved, for example, by using a shell material containing PTFE and / or TFE copolymer. The use of the blowing agent can also promote open porosity. The open porosity of the implant offers the particular advantage of vascular ingrowth, cell migration with simultaneous potential nourishment through pore channels, and in-vitro seeding with autologous cells prior to implantation.

[0046] A two-part mold shell arrangement is particularly preferred. This allows for simpler manufacturing of the mold shell arrangement, especially when producing elongated implants with a relatively small diameter, such as a meniscus implant.

[0047] According to a preferred embodiment, the inventive method for producing a plurality of implants is carried out repeatedly in succession, with each mold assembly being used to produce exactly one implant. This allows each mold assembly to be disposed of after a single use, thus avoiding costly cleaning processes and leading to increased flexibility. In other words, the mold assemblies are preferably disposable. If the holder is designed to produce several implants simultaneously, such a method can also be carried out multiple times in parallel to produce a corresponding plurality of implants.

[0048] In a further embodiment, after the implant has been produced and in particular before it has been demolded from the mold shell arrangement, it may be provided to temper the mold shell arrangement, in particular in a temperature range of 40 °C to 60 °C, preferably 45 °C to 55 °C.

[0049] According to a second aspect of the invention, the invention relates to a method for manufacturing a mold tray assembly that can be used to carry out the method described in the first aspect of the invention. The method is characterized in that the mold tray assembly is made of a meltable material. Such a mold tray assembly is considerably cheaper to manufacture than mold tray assemblies according to the prior art. It can therefore preferably be a disposable mold tray assembly. This allows the advantages already described in connection with the first aspect of the invention to be achieved.

[0050] Regarding further features and advantages of the method, full reference is made to the explanations given in the context of the first and second aspects of the invention.

[0051] Finally, the invention relates to the use of a mold shell arrangement made of a melt-processable material as a disposable mold shell arrangement for manufacturing an implant. The mold shell arrangement is used in a method according to the invention for manufacturing an implant according to the invention. This achieves the advantages already described above.

[0052] Regarding further features and advantages of its use, full reference is made to the previous description. Brief description of the characters

[0053] Further features and advantages of the invention will become apparent upon consideration of the exemplary embodiments described below with reference to the accompanying figures. Individual features of the invention may be implemented individually or in combination with one another. The exemplary embodiments serve only to illustrate the present invention, which is in no way limited to them.

[0054] The figures show schematically Fig. 1 a method according to the invention, Fig. 2 a holder with molded shell arrangements produced according to the invention, Fig. 3 a mold shell arrangement produced according to the invention, Fig. 4 an upper part of a molded shell arrangement produced according to the invention, Fig. 5 a lower part of a molded shell arrangement produced according to the invention, Fig. 6 an implant manufactured according to the invention. Detailed description of the exemplary implementations

[0055] Fig. Figure 1 shows a flowchart of a method according to the invention.

[0056] In step S1, a mold shell assembly is first produced. For this purpose, a shell material is used, which in this case is a mixture of PTFE and another polymer that modifies the properties of PTFE in such a way that it can be melt-processed. Accordingly, the mold shell assembly can preferably be produced by injection molding.

[0057] In step S2, the mold tray assembly is placed into a holder. The holder has corresponding recesses into which the mold tray assembly can be inserted.

[0058] In step S3, a product material is introduced into the mold assembly, which in this case is a mixture containing a polyol component, a polyisocyanate component, and a blowing agent. The product material is distributed evenly in a designated cavity of the mold assembly so that it completely fills the cavity.

[0059] In step S4, the implant is produced. In this case, the implant consists of foamed polyurethane. Implant production can be carried out using a reaction foam casting process and, from a reaction mechanics perspective, is based on a nucleophilic polyaddition.

[0060] In step S5, the implant is removed from the mold assembly. The implant can then be used, for example, sent to a doctor.

[0061] In step S6, the mold assembly is disposed of. Therefore, the mold assembly is a disposable mold assembly. If further implants are to be manufactured, separate mold assemblies are produced for each one.

[0062] Fig. Figure 2 shows a holder 10 which can be used to carry out the method according to the invention. The holder 10 has a main block 20 in which a total of six recesses 22 are formed. Each of the recesses 22 is designed to receive a mold tray arrangement.

[0063] Adjacent to each of the recesses 22 is a retaining block 30, which can be moved towards the respective recess 22 by means of a first screw 32 and a second screw 34. In this way, pressure can be easily exerted on a mold shell assembly located in the respective recess 22 by tightening the two screws 32, 34, in order to hold it in place. Two of the recesses 22 each contain a mold shell assembly 100. The mold shell assembly 100 will be discussed in more detail with reference to the following figures.

[0064] Fig. Figure 3 shows a mold shell arrangement 100. The mold shell arrangement 100 is designed in two parts, namely an upper part 200 and a lower part 300. A cavity 110 is formed between the upper part 200 and the lower part 300, in which an implant can be manufactured. In addition, vent channels 120 are formed between the upper part 200 and the lower part 300, from which excess product material can escape.

[0065] Fig. Figure 4 shows the upper part 200. The upper part 200 has a raised section 210 and an internal recess 220. The raised section 210 and the recess 220 serve in particular to engage in corresponding complementary projections or recesses of the retaining blocks 30 and thus to fix the upper part 200.

[0066] Furthermore, in the upper part 200 a part of the cavity 110 is defined by providing a corresponding recess.

[0067] Fig. Figure 5 shows the lower part 300. In the lower part 300, a portion of the cavity 110 is defined by a corresponding recess. Furthermore, the lower part 300 has an internal, recessed surface 310, which serves to fix it to the upper part 200.

[0068] In the Fig. 4 and Fig. Figure 5 shows that the recesses widen in such a way that, after assembling the upper part 200 and the lower part 300, a horseshoe-shaped (U-shaped or crescent-shaped) and wedge-shaped cavity is defined. This allows, for example, the creation of a correspondingly shaped meniscus implant, which is particularly advantageous.

[0069] Fig. Figure 6 shows a meniscus implant 400. The meniscus implant is made of foamed polyurethane (PUR) and has a horseshoe-shaped (U-shaped or crescent-shaped) wedge form. This corresponds to a correspondingly wedge-shaped cavity 110, as shown in the Fig. 3 to 5 were explained.

[0070] The meniscus implant 400 is manufactured using the method according to the invention. This allows it to preferably have an open-pored surface.

[0071] The meniscus implant 400 can be manufactured particularly advantageously using the described method according to the invention, since no complex and therefore expensive manufacturing process is necessary for the respective mold shell assemblies 100. Instead, these can be easily produced using injection molding. Due to the cost-effective manufacturing process, the mold shell assemblies can be disposed of after a single use, thus eliminating the need for complex cleaning steps. This reduces the costs of manufacturing a meniscus implant 400 and increases flexibility.

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