WO2010043620A1 - Medical product comprising ultrahigh molecular weight polyethylene - Google Patents

Medical product comprising ultrahigh molecular weight polyethylene Download PDF

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Publication number
WO2010043620A1
WO2010043620A1 PCT/EP2009/063352 EP2009063352W WO2010043620A1 WO 2010043620 A1 WO2010043620 A1 WO 2010043620A1 EP 2009063352 W EP2009063352 W EP 2009063352W WO 2010043620 A1 WO2010043620 A1 WO 2010043620A1
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WO
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Patent type
Prior art keywords
fiber
fibers
windings
product
polymer matrix
Prior art date
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PCT/EP2009/063352
Other languages
French (fr)
Inventor
Roelof Marissen
Carina Sacha Snijder
Original Assignee
Dsm Ip Assets B.V.
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Classifications

    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, E.G. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02Prostheses implantable into the body
    • A61F2/30Joints
    • A61F2/32Joints for the hip
    • A61F2/36Femoral heads ; Femoral endoprostheses
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61LMETHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION, OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICAL ARTICLES
    • A61L27/00Materials for grafts or prostheses or for coating grafts or prostheses
    • A61L27/14Macromolecular materials
    • A61L27/16Macromolecular materials obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C53/00Shaping by bending, folding, twisting, straightening or flattening; Apparatus therefor
    • B29C53/56Winding and joining, e.g. winding spirally
    • B29C53/58Winding and joining, e.g. winding spirally helically
    • B29C53/60Winding and joining, e.g. winding spirally helically using internal forming surfaces, e.g. mandrels
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, E.G. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02Prostheses implantable into the body
    • A61F2/30Joints
    • A61F2/3094Designing or manufacturing processes
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, E.G. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02Prostheses implantable into the body
    • A61F2/30Joints
    • A61F2/3094Designing or manufacturing processes
    • A61F2/30965Reinforcing the prosthesis by embedding particles or fibres during moulding or dipping
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, E.G. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02Prostheses implantable into the body
    • A61F2/30Joints
    • A61F2002/30001Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
    • A61F2002/30108Shapes
    • A61F2002/30199Three-dimensional shapes
    • A61F2002/30289Three-dimensional shapes helically-coiled
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, E.G. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2230/00Geometry of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2230/0063Three-dimensional shapes
    • A61F2230/0091Three-dimensional shapes helically-coiled or spirally-coiled, i.e. having a 2-D spiral cross-section
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C53/00Shaping by bending, folding, twisting, straightening or flattening; Apparatus therefor
    • B29C53/80Component parts, details or accessories; Auxiliary operations
    • B29C53/8008Component parts, details or accessories; Auxiliary operations specially adapted for winding and joining
    • B29C53/8016Storing, feeding or applying winding materials, e.g. reels, thread guides, tensioners
    • B29C2053/8025Storing, feeding or applying winding materials, e.g. reels, thread guides, tensioners tensioning
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C53/00Shaping by bending, folding, twisting, straightening or flattening; Apparatus therefor
    • B29C53/80Component parts, details or accessories; Auxiliary operations
    • B29C53/82Cores or mandrels
    • B29C53/821Mandrels especially adapted for winding and joining
    • B29C53/822Single use mandrels, e.g. destructible, becoming part of the wound articles
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS
    • B29K2223/00Use of polyalkenes or derivatives thereof as reinforcement
    • B29K2223/04Polymers of ethylene
    • B29K2223/06PE, i.e. polyethylene
    • B29K2223/0658PE, i.e. polyethylene characterised by its molecular weight
    • B29K2223/0683UHMWPE, i.e. ultra high molecular weight polyethylene
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29LINDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00Other particular articles
    • B29L2031/753Medical equipment; Accessories therefor
    • B29L2031/7532Artificial members, protheses

Abstract

A process for manufacturing a product, the process comprising the steps of providing windings of at least one fiber onto a mandrel, adhering at least some of the windings to adjacent windings and removing the mandrel from the windings, wherein the product is a medical product and the fiber comprises at least one fiber consisting of UHMwPE.

Description

MEDICAL PRODUCT COMPRISING ULTRAHIGH MOLECULAR WEIGHT

POLYETHYLENE

The invention relates to a process for manufacturing a medical product comprising ultrahigh molecular weight polyethylene (UHMWPE). The invention also relates to a medical product obtainable by the process.

Medical products such as artificial joints typically utilize a combination of polymer and metallic alloys. The metallic alloys are employed for the articulation and the polymer is employed as the soft socket. The polymer part wears against the metal articulation part during use, and ultrafine particles of polymer are loosened into the body over time. These particles are known to cause resorption of the periprosthetic bone. This results in loosening of the prosthesis components, possibly requiring even revision surgery.

Attempts to overcome this problem by improving abrasion resistance are made e.g. in US6168626B1 which discloses an artificial joint made by irradiating a raw UHMWPE molded article for introducing crosslink in polymer chains, compression- deforming the crosslinked UHMWPE molded article after heating up to its compression- deformable temperature, and cooling the molded article. The abrasion resistance is improved by molecular orientation of UHMWPE induced by the crosslink in the polymer chains and deforming at an elevated temperature. However, this process requires irradiation which necessitates special equipments.

The object of the present invention is therefore to provide a process for manufacturing a medical product with simple means.

This object is achieved according to the invention by a process according to claim 1. According to the invention a process for manufacturing a medical product is provided, wherein the process comprises providing windings of at least one fiber onto a mandrel, adhering at least some of the windings to adjacent windings and removing the mandrel from the windings. When one fiber is wound, the fiber is a fiber consisting of UHMwPE. When more than one fiber is wound, at least one of the fibers is a fiber consisting of UHMwPE. The process of the invention provides a medical product that is substantially form stable, due to the local adherence of the fibers, without the need of the irradiation step. The adhering of the windings herein refers to the windings being fixed to each other directly or via other medium. Examples of the way of the adhering are explained referring to preferred embodiments. The UHMwPE fiber provides a good abrasion resistance and strength. A suitable process according to the invention comprises winding the fibers onto a rotating mandrel.

UHMWPE is understood to be a preferably linear polyethylene with an intrinsic viscosity (IV, as determined on solutions in decalin at 135°C) of at least 4 dl/g, preferably at least 8 dl/g. The preparation and properties of UHMWPE fibers are described in numerous publications including GB 204214 A and WO 01/73171 A1 and such fibers are commercially available, for instance with the trademark Dyneema® of DSM (NL). Preferably, fibers with extremely high purity are used, such as Dyneema Purity®. Preferably, UHMWPE fibres made by the gel-spinning process such as described in GB 204214 A and WO 01/73171 A1 are used in the present invention. However, UHMWPE fibers can also be prepared by melt-spinning of UHMWPE, although the mechanical properties such as tenacity are more limited compared to the UHMWPE fibres made by the gel-spinning process. The upper limit of the molecular weight of the UHMWPE which can be melt-spun is lower than the limit with the gel- spinning process. The melt-spinning process is widely known in the art, and involves heating a PE composition to form a PE melt, extruding the PE melt, cooling the extruded melt to obtain a solidified PE, and drawing the solidified PE at least once. The process is mentioned e.g. in EP1445356A1 and EP1743659A1 , which are incorporated herein by reference.

Various forms of fiber can be employed in the process according to the invention. A "fiber" includes a body whose length is far greater than the transverse dimensions, and comprises a monofilament, a multifilament yarn, (partially) fused yarn, staple fibers, and the like. The fiber may have a generally circular cross section, or have an anisotropic cross section such as a rectangular and elliptical cross section and may thus be a tape. The fiber may also be braids, woven tapes, braided tapes made of one type of fiber or a mixture of different types of fibers. Suitable fibers include multifilament yarns, the thickness and number of filaments not being critical. Suitable yarns have a titer of for example 10 to 4000 dtex. The filament thickness from which the yarns are made may vary from for example 0.3 to 20 dpf. It is also possible to use a yarn spun from short filaments or staple fibers. Preferably, however, multifilament yarns are used.

The fiber may be made from a drawn polymer film. Such drawn polymer films are preferably slitted to form tapes or bands. Films may be prepared by feeding a polymeric powder between a combination of endless belts, compression- moulding the polymeric powder at a temperature below the melting point thereof and rolling the resultant compression-moulded polymer thereby forming a film. Another preferred process for the formation of films comprises feeding a polymer to an extruder, extruding a film at a temperature above the melting point thereof and drawing the extruded polymer film. If desired, prior to feeding the polymer to the extruder, the polymer may be mixed with a suitable liquid organic compound, for instance to form a gel, such as is preferably the case when using ultra high molecular weight polyethylene. In this case, the liquid organic compound needs to be removed from the film for suitable use in a medical product. The residual content of the liquid organic compound is preferably less than 200 ppm, more preferably less than 100 ppm, even more preferably less than 50 ppm. The maximum acceptable content varies depending on the type of the medical product. Drawing, preferably uniaxial drawing, of the films to produce tapes may be carried out by means known in the art. Such means comprise extrusion stretching and tensile stretching on suitable drawing units. To attain increased mechanical strength and stiffness, drawing may be carried out in multiple steps. The resulting drawn tapes may be used as such for filament winding to make the medical product, or they may be cut to their desired width, or split along the direction of drawing. The width of suitable tapes usually depends on the width of the film from which they are produced. In the product and method according to the invention, the width of the tapes preferably is at most 5 mm. The optimum width is dependent on the size and curvature of the final product. A larger size and lower curvature allow the use of a wider tape. The linear density of the tapes can be varied over a large range, for instance between 2 and 1000 g/km (in other words between 20 and 10000 dtex). The invented process allows medical products and articles to be produced without appreciable wrinkling. The possibility of providing a medical product without wrinkle is advantageous since wrinkles decrease the local abrasion resistance and strength and may lead to forming of particles from the material of the medical product. The process according to the present invention is especially advantageous in the case where the medical product has a curved shape, i.e. curved in one or more directions. It is in general more difficult to make a product having a curved shape without wrinkles compared to a flat product. With a product having a curved shape, or a curved product, it is meant in the context of this application, a product which, when positioned on a flat surface, has a ratio of maximum elevation with respect to said surface to the largest linear dimension within the projected surface of the product on the flat surface of at least 0.10. The higher this ratio is, the more difficult it is to make a - A -

product without wrinkles with conventional processes. With the process according to the present invention, a curved product can be made without wrinkles having this ratio of at least 0.20, or even 1.0.

A curved product may have a shape which is curved substantially in one direction, e.g. a cylinder or a tube shaped. In this case, the width of the tape is essentially limited by the largest dimension of the mandrel substantially perpendicular to the curve direction. A curved product may also have a shape curved in more than one direction, e.g. shapes at least partly including a spherical shape, a hemispherical shape. In this case, the width of the tape is more limited to prevent winkles. The tapes having a width of at most 5 mm usually allows them to be used for making medical products which typically have a dimension of 5-50 cm. Preferably, the width of the tapes is at most 3 mm, more preferably at most 1 mm.

A further advantage of the process according to the invention is that the fibers may be oriented in any desired directions across the surface of the mandrel, whereby a wrinkle-free object with more homogeneous properties or controlled in homogeneity may be obtained.

A preferred embodiment of the process according to the invention comprises the step of exposing the at least some of the windings to a temperature within the melting point range of the fibers for a time sufficient to at least partly fuse adjacent windings, hereinafter also referred as the fusing step. This may be done by placing the body made by the windings in an oven. This embodiment is preferable for the manufacture of medical product, since it does not require any additional materials for the adhering step. This results in that care needs to be taken for the suitability of only the fibers for medical products. In one embodiment, this fusing step involves compression moulding the windings at the temperature within the melting point range of the fibers. The pressure applied to the windings promotes the fusing of the windings and consolidates the product, which leads to its better integrity.

The person skilled in the art will generally be able to choose a suitable combination of the elevated temperature, pressure as well as time to adequately consolidate the product by routine experiment. The desired compression moulding will generally take place in about 1 minute to a few hours, preferably about 5 to 45 minutes. Elevated pressures may vary widely, but are preferably higher than about 7 MPa, more preferably higher than about 10 MPa, even more preferably higher than about 15 MPa. In general higher pressures are more favourable, because they allow better fusion and because the meting temperature (and accompanying decrease of orientation) increases under pressure. The skilled person will be able to determine the upper limit for the pressure through routine experiments.

In general, the temperature is chosen below the melting point of the fibers. Temperatures below the melting point cause better preservation of the molecular orientation of the fibers. Higher temperatures yield better fusion of the fibers. Surprisingly it was found that even temperatures above the melting point allow a slight preservation of the orientation. The elevated temperature is preferably selected between 600C below and 15°C above the melting or softening temperature of the fibers, and more preferably between 500C below and 100C above the melting or softening temperature of the fibers. In the case that the fibers to be fused are polymeric, the suitable temperature for most practical applications is between 800C and 380°C. In case the fibers to be fused are UHMWPE fibers the suitable temperature for most practical applications is between 1 100C and 1600C. Due to the applied pressure, the fibers are substantially kept tensioned, thus preventing the good mechanical properties from being lost or significantly diminished as a result of molecular relaxation of the polymeric fibers. In a preferred embodiment, after the winding step, pressure is applied to the body made by the winding, and subsequently the temperature is increased to the desired temperature. While the pressure is still applied, the body made by the winding is cooled down to a temperature sufficiently below the melting point of the polymer. For UHMWPE, a temperature of 80 °C is sufficiently low. The body is then demoulded. In this way it is avoided that the polymeric fibers go through relaxation which would decrease the mechanical properties thereof, throughout the process. In the process, the body made by the windings substantially has the shape required in the final medical product, prior to compressing. This largely prevents wrinkles from occurring, which is beneficial for the various properties including abrasion resistance of the medical product.

The mould may be of a different shape than the mandrel. This causes the medical product to have a different thickness at different parts of the product.

Before the compression moulding step, the body made by the windings may be provided with a polymer film layer, which layer has a lower melting point than the fibers. Such a polymer film layer further stabilizes the body made by the windings before and during the compression moulding step. The polymer film layer may extend over part or substantially the entire surface of the body made by the windings. During the compression moulding, the polymer film layer may at least partly melt and form an integral part of the compression moulded medical product.

The body made by the windings may also be enclosed in a polymer film envelope having a lower melting point than the fibers. A vacuum is applied to the envelope. The vacuum removes the air from the windings and prevents oxidative degradation during the compression moulding. Preferably the polymer film envelope is in virtually full contact with the surfaces of the body made by the windings, prior to applying the vacuum inside the envelope. This prevents the body made by the windings from deforming or even collapsing when applying the vacuum pressure. Such an embodiment of the process maintains the quality during transport of the body made by the windings and increases its coherence. The polymer film envelope may at least partly melt and form an integral part of the compression moulded medical product

In another embodiment, the at least some of the windings is locally exposed to the temperature within the melting point range of the fibers. This will result in a local adhering of the fibers by fusing. With local adhering is meant that at most 20 wt% of the fibers are adhered to adjacent fibers in any direction, e.g. across the surface of the medical product or over the thickness thereof. The fibers locally melt, and recrystallize to form integral and bonding connection between the adjacent fibers. The occurrence of melting and recrystallization can be measured by DSC (Differential Scanning Calorimetry). This may be accomplished in a number of ways. The local adhering of the adjacent fibers may for instance be accomplished by local heating means such as IR sources, heated cutting elements and the like.

In another embodiment of the process, the process comprises applying a polymer matrix to the at least some of the windings and adhering the at least some of the windings via the polymer matrix. Suitable polymer matrices to be used in the product and method according to the invention comprise polymers as used for standard composites, as long as they do not have adverse effect on the human body. Examples of the suitable polymers are polyolefins with a low melting point, e.g. linear low-density polyethylene. Also, if care is taken to prevent remainders of toxic isocyanates, polyurethanes may be used. Furthermore, polyvinyls and polyacrylics may be used if toxic residues are prevented. The term polymeric matrix refers to a material that binds or holds the fibers together. The matrix may enclose the fibers in their entirety or in part. The polymer may be a thermoplastic material or mixtures of a thermosetting material and a thermoplastic material, or a thermosetting material. The polymer matrix may be applied as a solid material, e.g. a powder and the powder may be exposed to a temperature within the melting point range of the polymer matrix for a time sufficient to at least partly fuse the polymer matrix. The polymer matrix may be applied to the fibers before, during or after the winding step. The fibers may be wetted, preferably with water, to render them some temporary stickiness, and the polymer matrix may be applied thereon. The particles of polymer matrix are locked between the fibers after winding on the mandrel. The polymer matrix melts and adheres the adjacent windings to each other during the heating step. Suitable polymer matrix can be many polymers, but preferably polyethylene, which may be UHMWPE.

The polymer matrix may also be applied as a liquid material and then be solidified. The liquid polymer matrix may be applied by spraying, dipping, and the like, before, during or after winding the fiber onto the mandrel. The liquid polymer matrix may be solidified by e.g. curing of the polymer matrix or evaporating the carrier fluid in the polymer matrix. In a first embodiment, the fibers are fed through a liquid polymer matrix prior to the winding, subsequently fed through a positioning eye on a rotating mandrel having approximately the inner shape of the medical product, such as an artificial joint. A second preferred method comprises dry winding and subsequent impregnation of the windings with a liquid polymer matrix. A third preferred method comprises dry winding and spraying the surface of the body made by the windings with a liquid polymer matrix.

The liquid polymer matrix may consist of a polymer in a liquid form, or the polymer matrix is a polymer solution and/or polymer dispersion. The advantage of using polymer matrix solutions and/or dispersions is that the liquid carrier can be evaporated later and thus create the desired low matrix content in the final product. A low matrix content is desirable because the matrix tends to decrease mechanical properties of the final product. It turned out that the amount of carrier fluid is preferably at least 20% by mass, more preferably at least 30% by mass, and most preferably at least 40% by mass of the total weight of the polymer matrix solution and/or dispersion. The body obtained after the step of adhering at least some of the windings to adjacent windings may be further compression moulded. This step makes the medical product more form stable and mechanically stronger. The person skilled in the art will be able to choose a suitable combination of the elevated temperature, pressure and time to adequately consolidate the product, as described above. In one embodiment, the fibers consist of UHMwPE fibers. This embodiment provides especially favourable mechanical properties including abrasion resistance.

Different types of fibers may also be used in one medical product. By combining different fibers the performance of the medical product can be even better adjusted to specific needs. Other fibers to be suitably applied in the product according to the invention include a number of biocompatible fibers. Suitable drawn polymeric fibers are prepared from a polymeric material whose macromolecules exhibit a certain degree of chain slip at a temperature below the melting point, i.e. in the solid phase, under the influence of an imposed stress. The orientation induced improves the mechanical properties such as abrasion resistance. Examples include various polyolefin fibers, such as for example a non-UHMWPE polyethylene fiber, a polyetherester copolymer fiber, a polyurethane fiber, a polyethylene terephthalate fiber. Other types of the biocompatible fibers include a carbon fiber, a ceramic fiber and a glass fiber. The fibers may also be of a biodegradable and biocompatible material. Examples include a fiber of the so-called Corglaes™. Corglaes™ is described by GRIFFON D. J. ; DUNLOP D. G. ; HOWIE C. R. ; GILCHRIST T. ; SALTER D. M. ; HEALY D. M. in Journal of biomedical materials research, ISSN 0021-9304 , 2001 , vol. 58, no6, pp. 638-644. Also a glass fiber known by the name of FiberLive™ from Vivoxid Ltd may be used. In order to be reasonably biocompatible and to allow bone growth, the ceramic or glass material preferably contains less than 50% silicon oxide. These biocompatible fibers of various materials mentioned above give e.g. better creep resistance and other functionalities. Depending on the needs, different types of fibers may be used at different location of the medical product. In a particularly advantageous embodiment, various functional materials are added to the medical product, such as a bone growth promoter and a growth factor. Examples of include calcium phosphate, hydroxyl apatite and a growth- hormone-releasing hormone. Also, antibiotics may be added. These functional materials may be added to the fibers before, during or after the winding step. The functional materials may also be added to the polymer matrix in a suitable form. When these functional materials are added to the fibers as a powder, it may be applied to the fibers by using liquid as a temporary binder. The bone growth promoter is especially advantageous in an artificial joint, as this provides good bone ingrowths at the location where bone connection is desired. Especially advantageous embodiment uses a biodegradable and biocompatible fiber mentioned above, in combination with calcium phosphate.

Other fibers may be used, such as aramid fibers, polybenzoxazoles fibers, poly(p-phenylene-2, 6-benzobisoxazole) fibers (PBO, Zylon®), and poly(2,6- diimidazo-(4,5b-4',5'e)pyridinylene-1 ,4(2,5-dihydroxy)phenylene) fibers (better known as M5® fibers). These fibers with unproven biocompatibility are preferably used only at the inner part of the product, where the fibers do not come into contact with the body. They may provide more strength and stiffness than biocompatible fibers. A product with different types of fibers at the inner part and at the surface part may be made e.g. by winding a first type of fiber onto the mandrel and subsequently winding a second type of fiber onto the body made of the first type of fiber. Alternatively, a biocompatible binder is applied and forms a surface layer of the medical product which comes into contact with the body.

The fibers preferably have a tensile strength of at least 1.6 GPa, more preferably at least 1.8 GPa, and most preferably at least 2 GPa, and a tensile modulus of at least 50 GPa. More preferably, the tensile strength is at least 2.5 and even 3 GPa and the modulus at least 70 and even 90 GPa. The tensile properties of the fibers are determined by a method as specified in ASTM D885M. The use of fibers with such a high modulus and tensile strength allows objects to be manufactured with good flexural stiffness and high resistance to extraneous forces.

A preferred product according to the invention comprises an amount of fibers of at least 60 wt% of the total mass of the product. Even more preferred is a product wherein the amount of fibers is at least 75 wt% of the total mass of the product, and most preferably at least 85 wt% of the total mass of the product. Especially in the case that all the fibers are polyethylene, the amount of the fibers can be essentially 100 wt%. Such high mass (or volume) fractions of fibers in the medical product are very beneficial to the mechanical properties thereof. These high reinforcement fractions (or low polymer matrix fractions) are normally not achieved in composite products made by any method and by filament winding in particular. Such "polymer matrix poor" products normally lead to resin starved areas of the product. These areas are unwanted. When filament winding composite products, polymer matrix fractions of around 60% by mass and more are not uncommon. Some matrix material may be removed by applying bleeding and/or peel ply materials, but this is cumbersome. Moreover polymer matrix fractions less than 40% by mass are not achievable by such process. This problem has been solved according to one embodiment of the invention by using polymer matrix solutions and/or dispersions. The process yields substantially complete impregnation of the fibers and/or films but after drying only 20% by mass of matrix is typically present. According to the process of the invention, a medical product is made by winding one fiber, or preferably a plurality of fibers onto a mandrel. The process preferably comprises unwinding bobbins of fibers under tension. In a preferred embodiment the medical product is manufactured by simultaneously winding a plurality of fibers such as fiber bundles onto the mandrel using supply means during the filament winding process. Suitable supply means comprise a creel provided with bobbins, and eventually guiding means, for instance in the form of dispensing tubes, to guide the fibers over the surface of the mandrel. This measure allows for filament winding with reduced production times, while keeping the device simple. It is especially advantageous in case of producing large series of products. A plurality of fibers is preferably comprised between 10 and 60 fibers, and more preferably between 24 and 48. A compromise between manageability and production time is hereby obtained.

During the filament winding process the supply means preferably move relative to the mandrel. In still another preferred embodiment the supply means adjust the length of a fiber spanning the distance between the mandrel surface and the supply means. This measure leads to a more constant tension on the fibers and therefore to a product with a better quality. Adjusting the free length of the fibers between supply means and mandrel surface may for instance be carried out by providing supply means in the form of fiber dispensing tubes, provided with electro motors that act on the fiber bobbins. According to a preferred embodiment the supply means is provided with a means for controlling the tension of a fiber between the mandrel surface and the supply means during the filament winding.

Control of the tension in the fibers is favourable for the mechanical properties of the product or article, and in particular for its stiffness and strength. The control means may control the tension of all the fibers in the same manner. Alternatively, each fiber is controlled independently. The independent control of the tension of the fibers is especially advantageous when the fibers are of different types.

Filament winding patterns are naturally restricted to "about geodetic patterns", although this is not necessary for the invention. A winding trajectory is geodetic when it spans the shortest distance between two points on the surface of the product. The design of winding patterns requires special care regarding the choice of a pattern that fulfils the "about geodetic pattern" and prevents local accumulation of fibers at certain locations. Optimal medical products are preferably wound in such a way that local accumulations are sufficiently "diluted" or spread over the product surface. Modern software, known per se, allows filament winding specialists to design winding patterns with sufficient "dilution" of local fiber accumulations. Also, trial and error methods may be employed to obtain adequate winding patterns.

In a preferred embodiment the medical product is produced by filament winding fibers onto a mandrel with polar surfaces, which mandrel rotates around a central shaft, the polar surfaces being that part of the mandrel where the central shaft enters or exits. Fibers are positioned onto such a mandrel substantially over its surface and its polar surfaces. In this way a substantially closed product is obtained.

The closed product may be removed from the mandrel by subsequently partitioning the closed product. The closed product may be partitioned in two halves, thus producing two similar medical products in one time. An artificial hip joint or an artificial knee joint is efficiently obtained in this way. The partitioning may be done by a heated cutting device. The device heated to a sufficient high temperature will cause the fibers on the cut surface to be locally fused together. Depending on the shape of the product, the substantially closed product may be partitioned into three or more pieces. For example, an artificial shoulder joint having a shape close to a quarter of a sphere may be obtained by partitioning the substantially closed product into four pieces.

Due to the presence of the shaft during winding, the apex of the medical products will generally have an opening when the shaft is removed after the winding process. Such an opening, if present after winding and/or pressing, may for instance be closed by inserting in it a fitting plug. This process may be further enhanced by adopting a non-geodetic pattern on the polar surfaces. Because of the presence of the shaft, the fibers may be wound around this shaft under tension and in a non-geodetic pattern (in the end article). When removing the shaft, the non-geodetic fibers under tension reposition from their non-geodetic pattern to a pattern that is closer to a geodetic pattern, thereby reducing the opening and/or clamping, and thereby better fixing the plug.

The mandrel may be made of a material soluble to a solvent that does not dissolve or have adverse effect on the fiber. For example, a mandrel may be made of a water-soluble material, such as water soluble polymers, or even salt or sugars. The removal of the medical product from the mandrel may in this case be done by placing into water the closed product surrounding the mandrel and washing the dissolved mandrel out of the product. This is especially suitable for making a product in which the partitioning step is not appropriate. A product which is suitably made by this process includes a medical balloon. In the embodiment where the fiber is adhered by fusing, the medical product is readily removed from the mandrel without there being any need to dry and/or cure any polymer matrix, and can therefore be readily finished by edge trimming for instance, e.g. by using the heated cutting device that was mentioned earlier.

The number of fibers positioned on the mandrel during filament winding may be varied and is generally such that the desired thickness is reached. In the process according to the invention, many different winding patterns for the fibers are in principle possible.

Preferred medical products according to the present invention includes an artificial hip joint, an artificial shoulder joint, an artificial knee joint and a medical balloon. Particularly advantageous embodiments contain a bone growth promoter, a growth factor and/or an antibiotic.

Claims

1. A process for manufacturing a product, the process comprising the steps of: a) providing windings of at least one fiber onto a mandrel, b) adhering at least some of the windings to adjacent windings and c) removing the mandrel from the windings, wherein the product is a medical product and the fiber comprises at least one fiber consisting of UHMwPE.
2. The process according to claim 1 , wherein the step b) involves the step of b1 ) exposing the at least some of the windings to a temperature within the melting point range of the fibers for a time sufficient to at least partly fuse adjacent windings.
3. The process according to claim 2, wherein the step b1 ) involves compression moulding the windings at the temperature within the melting point range of the fibers.
4. The process according to claim 2, wherein the step b1 ) involves locally exposing the at least some of the windings to the temperature within the melting point range of the fibers.
5. The process according to claim 1 , wherein the step b) involves the step b2) of applying a polymer matrix to the at least some of the windings and adhering the at least some of the windings via the polymer matrix.
6. The process according to claim 5, wherein the step b2) involves applying the polymer matrix as a solid material and exposing the polymer matrix to a temperature within the melting point range of the polymer matrix for a time sufficient to at least partly fuse the polymer matrix.
7. The process according to claim 5, wherein the step b2) involves applying the polymer matrix as a liquid material and solidifying the polymer matrix.
8. The process according to any one of the preceding claims, further comprising the step of compression moulding the medical product.
9. The process according to any one of the preceding claims, wherein the fiber further comprises at least one biocompatible fiber selected from a group consisting of a polyethylene fiber, a polyetherester copolymer fiber, a polyurethane fiber, a polyethylene terephthalate fiber, a carbon fiber, a ceramic fiber and a glass fiber.
10. The process according to any one of the preceding claims, wherein part of the fibers is wound in a pattern that is at least partly non-geodetic.
11. A medical product obtainable by any one of the preceding claims.
12. The process according to claim 1 1 , wherein the medical product has a curved shape.
13. The medical product according to claim 1 1 or 12, wherein the product is selected from a group consisting of an artificial hip joint, an artificial shoulder joint, an artificial knee joint and a medical balloon.
14. The medical product according to claim 1 1 , 12 or 13, containing a bone growth promoter, a growth factor and/or an antibiotic.
PCT/EP2009/063352 2008-10-17 2009-10-13 Medical product comprising ultrahigh molecular weight polyethylene WO2010043620A1 (en)

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EP08166869 2008-10-17

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2644057A1 (en) * 1989-03-09 1990-09-14 Squibb Bristol Myers Co orthopedic implant
US5160472A (en) * 1984-10-24 1992-11-03 Zachariades Anagnostis E Method of producing composite structures of ultra-high-molecular-weight polymers, such as ultra-high-molecular-weight polyethylene products
WO1995021054A1 (en) * 1994-02-03 1995-08-10 United Kingdom Atomic Energy Authority Fibre reinforced composite artefact and method for manufacturing same
US5609638A (en) * 1994-11-29 1997-03-11 Zimmer, Inc. Reinforced polyethylene for articular surfaces
WO2001045766A1 (en) * 1999-12-22 2001-06-28 Advanced Cardiovascular Systems, Inc. Medical device formed of ultrahigh molecular weight polyolefin
WO2005065911A1 (en) * 2004-01-07 2005-07-21 Dsm Ip Assets B.V. Process for manufacturing a prosthetic joint

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5160472A (en) * 1984-10-24 1992-11-03 Zachariades Anagnostis E Method of producing composite structures of ultra-high-molecular-weight polymers, such as ultra-high-molecular-weight polyethylene products
FR2644057A1 (en) * 1989-03-09 1990-09-14 Squibb Bristol Myers Co orthopedic implant
WO1995021054A1 (en) * 1994-02-03 1995-08-10 United Kingdom Atomic Energy Authority Fibre reinforced composite artefact and method for manufacturing same
US5609638A (en) * 1994-11-29 1997-03-11 Zimmer, Inc. Reinforced polyethylene for articular surfaces
WO2001045766A1 (en) * 1999-12-22 2001-06-28 Advanced Cardiovascular Systems, Inc. Medical device formed of ultrahigh molecular weight polyolefin
WO2005065911A1 (en) * 2004-01-07 2005-07-21 Dsm Ip Assets B.V. Process for manufacturing a prosthetic joint

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