HK1245621B - Orthopedic implant - Google Patents

Description

Plastic implants

Technical Field

The present invention relates to an implant that is particularly useful in craniomaxillofacial plastic surgery.

background

It is known to use reinforced composite materials made from particulate fillers or reinforcing fibers. Existing fiber reinforced composite materials have high strength properties, and the handling characteristics of the composite material can be significantly improved by selecting a multiphase resin matrix for the composite material.

On the other hand, bioactive materials, namely bioactive ceramics and glasses, as well as sol-gel processed silica, have seen considerable development. These materials can be used, for example, to adhere bone to a biomaterial surface after the material has come into contact with tissue. Another advantage of bioactive glass is its antimicrobial effect on microorganisms. However, bioactive ceramics and glasses are quite brittle and therefore not easily used in their original form in implants.

For example, WO 88/03417 proposes a biocomposite material for bone surgery applications, comprising at least one bioceramic sheet and at least one material component made of at least one polymer or a corresponding material. The material component and the bioceramic component share at least one common boundary surface and include at least one reinforcing element made of a substantially resorbable material, such as a polymer, copolymer, polymer blend, and/or ceramic material. The material component may include a binder material substantially made of a resorbable polymer, copolymer, or polymer blend. The material component exhibits an open porosity, at least under tissue conditions.

Despite advances in biomaterial research, methods for their clinical application, and tissue engineering, individual replacements of bone, cartilage, and soft tissue are insufficient from a surgical perspective in tumor, trauma, and tissue reconstruction surgery. The necessity and indication for developing new materials stem from the shortcomings of using allografts. Metals are not bioactive or osteoconductive, and their use leads to stress shielding and bone atrophy of adjacent bones. Metal implants cause serious problems in magnetic resonance imaging (MRI) when diagnosing patient diseases and due to heating of the implant during imaging. Therefore, there is still a need for alternative implants for medical use.

OBJECTIVES AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a biocompatible material which does not have the disadvantages listed above, or at least reduces these disadvantages to a minimum. In particular, it is an object of the present invention to provide an implant for medical, dental and surgical applications, such as a bone graft for repairing bone defects and for fixing bone fragments of fractures.

A typical implant according to the invention consists of:

a surface layer consisting of fibers and a matrix, the surface layer having a first surface and a second surface opposite to each other and having a thickness of at most 5% of the maximum dimension of the surface layer;

- a porous biodegradable portion having a first surface and a second surface opposite to each other and having a thickness of 1 to 8 mm, wherein the first surface thereof is attached to the second surface of the surface layer, and

a membrane layer made of collagen, the membrane layer having a first surface and a second surface opposite to each other, wherein the first surface thereof is attached to the second surface of the porous portion and does not cover the edge of the porous portion,

The porous portion comprises a material selected from the group consisting of bioactive glass, bioactive ceramics, hydroxyapatite, tricalcium phosphate, and mixtures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 schematically shows an implant according to a first embodiment.

Fig. 2 schematically shows an implant according to a second embodiment.

Fig. 3 schematically shows an implant according to a third embodiment.

4A and 4B schematically illustrate an implant according to a fourth embodiment.

Detailed Description of the Invention

A typical implant according to the invention consists of:

a surface layer consisting of fibers and a matrix, the surface layer having a first surface and a second surface opposite to each other and having a thickness of at most 5% of the maximum dimension of the surface layer;

- a porous biodegradable portion having a first surface and a second surface opposite to each other and having a thickness of 1 to 8 mm, wherein the first surface thereof is attached to the second surface of the surface layer, and

a membrane layer made of collagen, the membrane layer having a first surface and a second surface opposite to each other, wherein the first surface thereof is attached to the second surface of the porous portion and does not cover the edge of the porous portion,

The porous portion comprises a material selected from the group consisting of bioactive glass, bioactive ceramics, hydroxyapatite, tricalcium phosphate, and mixtures thereof.

Therefore, implant according to the present invention has utilized the benefit of capillary effect, because fluid can penetrate into the inside of the biodegradable porous part of implant.Therefore the porous part of implant strengthens the growth of new bone, cartilage etc., and non-biodegradable surface layer provides mechanical strength and anatomical type.Another benefit is that it allows to manufacture the implant material that is very similar to real bone, i.e. avoids using allograft. On the other hand, due to the increase of magnetic resonance imaging, it is not too desirable to have traditional metal implant.Therefore, the present invention provides both safe (cannot have the risk of being contaminated like allograft) and do not interfere with the currently used imaging system (and metal can interfere) implant.

In this specification, curing refers to polymerization and/or crosslinking. The matrix is understood to be the composition of the continuous phase; an uncured matrix is a matrix that is in its deformable state but can be cured (i.e. hardened) to a substantially non-deformable state. An uncured matrix may already contain some long chains, but substantially no polymerization and/or crosslinking has occurred. In this specification, polymerization can be carried out by any known means, such as autopolymerization, photopolymerization, thermal polymerization, ultrasound or microwave polymerization. Curing of the resin produces a composite material, in which the cured resin forms the matrix.

The surface layer can be porous or non-porous, and wherein non-porous refers to that for the fluid existing at the implantation site, this material is impermeable basically.Be porous at the surface layer, i.e. perforation (due to its material or after the specific perforation step during its manufacture), under the situation that its porosity is preferably less than the porosity of biodegradable part.For example, its average pore size can be 0.8-500 micron.

The biodegradable portion is a porous portion with interconnected porosity and an average pore size of 100-1000 microns. The porosity allows extracellular fluid and cells to penetrate the porous portion and allows bone, blood cells and other tissues to grow inward. The porous portion is typically degraded over a period of several weeks (e.g., biodegradable polymers) to several years (e.g., hydroxyapatite), and is replaced by new bone. When considering bone in-growth, the optimal pore size for intraosseous application is 100-500 microns, but the porous portion can optionally include larger holes. In addition, in order to reduce the attachment of the dura mater to the implant, the inner surface of the porous portion can be mostly covered with a membranous material made of collagen (e.g., Medtronic's Durepair Dura Regeneration Matrix ^™ ). This may be advantageous in some cases, for example, for patients with increased pressure in the brain, which will cause the dura mater to contact the surface of the porous portion. The membranous material does not fully cover the surface of the porous portion, but exposes its edge. This ensures that body fluid can penetrate the porous portion. For example, when considering from the edges of the porous portion, 1-2 mm of each edge may not be covered by the membrane.

The thickness of the surface layer can be, for example, 0.2-4.0 mm. For example, in cranial applications, a thickness of 0.5-1.0 mm may be suitable for the surface layer; in load-bearing implants, a thickness of 1.0-3.0 mm may be suitable for this layer. Typically, the thickness of the surface layer can be 0.2, 0.3, 0.5, 0.7, 1, 1.5, 1.7, 2, 2.5, 3, or 3.5 mm to a maximum of 0.3, 0.5, 0.7, 1, 1.5, 1.7, 2, 2.5, 3, 3.5, or 4.0 mm.

The thickness of the membrane made of collagen can be, for example, 0.05-0.80 mm. The thickness can be, for example, from 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7 or 0.75 mm to at most 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75 or 0.8 mm.

The porous part can be manufactured, for example, by sintering, laser sintering, molding suitable materials, electrospinning, 3D printing or by grinding. The surface layer can be non-biodegradable, i.e. inert, or it can be biodegradable. The material used is naturally selected according to the required degradation rate. When the surface layer is biodegradable, its degradation time is at least ten times that of the porous part. This allows the bone surface to grow inward and mature before the surface layer loses its mechanical strength. Slowly biodegradable outer surface laminates can be made of fibers such as bioactive glass, sodium calcium metaphosphate, cellulose, hemp or starch and by slowly degradable polylactide, polycaprolactone polymer or polysaccharide as a material of the matrix.

One suitable example of a bioactive glass is glass S53P4, which is a resorbable bioactive glass having a composition of 53% _SiO2 , 23% _Na2O , 20% CaO and 4% _P2O5 (available, for example, from BonAliveBiomaterials Ltd, Turku, Finland ₎ .

In the case where the surface layer is also biodegradable, the implant is preferably attached to the bone by a slowly biodegradable screw. This enables the surgeon to avoid a second operation to remove the screw, so it is particularly beneficial in pediatric surgery.

The non-biodegradable fibers of the surface layer may be any suitable fibers known in the art, for example selected from inert glass fibers, silica/quartz fibers, carbon/graphite fibers, inert ceramic fibers, aramid fibers, zylon fibers, polyethylene fibers, polytetrafluoroethylene fibers such as fibers, poly(p-phenylene-2,6-benzobisoxazole) fibers, poly(2,6-diimidazo(4,5-b4',5'-e)pyridinyl-1,4-(2,5-dihydro)phenylene fibers, poly(1,2-dapoxetine) ... Olefin fibers, fibers made from olefin copolymers, polyester fibers, polyamide fibers, and mixtures thereof. Poly(p-phenylene-2,6-benzobisoxazole) fibers and poly(2,6-diimidazo(4,5-b4',5'-e)pyridinyl-1,4(2,5-dihydro)phenylene fibers belong to a group called rigid-rod polymer fibers. It will be apparent to those skilled in the art that any other known fibers can be used in the present invention, as long as appropriate adhesion can be achieved between the fiber and the substrate to achieve the desired mechanical properties and the fiber is biocompatible.

According to one embodiment of the invention, the fibers are selected from inert glass fibers. According to another embodiment, the glass fibers are made of a glass composition of E-glass, S-glass, R-glass, C-glass or bioactive glass.

According to another embodiment, the diameter of the fiber is 4-25 μm. The diameter of the fiber can be, for example, from 3, 5, 6, 10, 15, 20, 25, 30, 40, 45, 50, 60, 70 or 80 μm to a maximum of 5, 6, 10, 15, 20, 25, 30, 40, 45, 50, 60, 70, 80, 90 or 100 μm. Nanoscale fibers, i.e., fibers with a cross-sectional diameter of 200-1000 nm, can also be used.

The fibers may be in the form of a fiber fabric or a fiber mat, and they may be oriented in two directions, three directions, four directions, or they may be randomly oriented.

The matrix can be made of a resin composed of monomers selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-hexyl acrylate, styrene acrylate, allyl acrylate, methyl methacrylate, polymethyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, tetrahydrofurfuryl methacrylate, benzyl methacrylate, morpholinoethyl methacrylate, diurethane dimethacrylate, acetoacetoxyethyl methacrylate (AAEM), methacrylate. Ester-functionalized dendrimers, other methacrylated hyperbranched oligomers, hydroxymethyl methacrylate, hydroxymethyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, tetrahydrofurfuryl methacrylate, tetrahydrofurfuryl acrylate, glycidyl methacrylate, glycidyl acrylate, triethylene glycol diacrylate, tetraethylene glycol dimethacrylate, tetraethylene glycol diacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, trimethylolethane triacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol Pentaerythritol tetramethacrylate, pentaerythritol tetraacrylate, ethylene dimethacrylate, ethylene diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate (TEGDMA), ethylene glycol diacrylate, diethylene glycol diacrylate, butanediol dimethacrylate, butanediol diacrylate, neopentyl glycol dimethacrylate, hydroxyethyl methacrylate, urethane dimethacrylate, star methacrylated polyester, hyperbranched methacrylated polyester, neopentyl glycol diacrylate, 1,3-butanediol dimethacrylate, 1,3-butanediol diacrylate, 1,4-butanediol dimethacrylate acrylate, 1,4-butanediol diacrylate, 1,6-hexanediol dimethacrylate, 1,6-hexanediol diacrylate, di-2-methacryloyloxyethyl hexamethylene dicarbamate, di-2-methacryloyloxyethyl trimethyl hexamethylene dicarbamate, di-2-methacryloyloxyethyl dimethylphenyl dicarbamate, di-2-methacryloyloxyethyl dimethylcyclohexane dicarbamate, methylene-bis-2-methacryloyloxyethyl-4-cyclohexylcarbamate, di-1-methyl-2-methacryloyloxyethyl hexamethylene dicarbamate, di-1-methyl-2-methacryloyloxyethyl Methylene-bis-1-methyl-2-methacryloyloxyethyl-4-cyclohexylcarbamate, di-1-chloromethyl-2-methacryloyloxyethyl-hexamethylene-bis-1-methyl-2-methacryloyloxyethyl-trimethylhexamethylene-bis-1-methyl-2-methacryloyloxyethyl-dimethylphenylenedicarbamate, di-1-chloromethyl-2-methacryloyloxyethyl-dimethylphenylenedicarbamate, di-1-chloromethyl-2-methacryloyloxyethyl-trimethylhexamethylene-bis-1-methyl-2-methacryloyloxyethyl-dimethylphenylenedicarbamate, di-1-chloromethyl-2-methacryloyloxyethyl- Methylene-bis-2-methacryloyloxyethyl-4-cyclohexylcarbamate, di-1-methyl-2-methacryloyloxyethyl-hexamethylene-bis-carbamate, di-1-methyl-2-methacryloyloxyethyl-trimethylhexamethylene-bis-carbamate, di-1-methyl-2-methacryloyloxyethyl-dimethylphenylenedicarbamate, di-1-methyl-2-methacryloyloxyethyl-dimethylcyclohexyldicarbamate, methylene-bis-1-methyl-2-methacryloyloxyethyl-4-cyclohexylcarbamate, di-1-chloromethyl-2-methacryloyloxyethyl-trimethylhexamethylene- Methylhexamethylene dicarbamate, bis-1-chloromethyl-2-methacryloyloxyethyl-dimethylphenyl dicarbamate, bis-1-chloromethyl-2-methacryloyloxyethyl dimethylcyclohexane dicarbamate, methylene-bis-1-chloromethyl-2-methacryloyloxyethyl-4-cyclohexylcarbamate, 2,2-bis(4-(2-hydroxy-3-methacryloyloxy)phenyl)propane (BisGMA), 2,2'-bis(4-methacryloyloxyphenyl)propane, 2,2'-bis(4-acryloyloxyphenyl)propane, 2,2'-bis[4-(2-hydroxy-3-acryloyloxyphenyl)propane, 2,2'-bis (4-Methacryloxyethoxyphenyl)propane, 2,2'-bis(4-acryloyloxyethoxyphenyl)-propane, 2,2'-bis(4-acryloyloxypropoxyphenyl)propane, 2,2'-bis(4-acryloyloxy-propoxyphenyl)propane, 2,2'-bis(4-methacryloyloxydiethoxyphenyl)-propane, 2,2'-bis(4-acryloyloxydiethoxyphenyl)propane, 2,2'-bis[3-(4-phenoxy)-2-hydroxypropane-1-methacrylate]propane, 2,2'-bis[3-(4-phenoxy)-2-hydroxypropane-1-acrylate]propane, polyetheretherketone, and mixtures thereof.

The matrix may of course also consist of a mixture of one or more monomers and one or more polymers.

According to one embodiment, the matrix material is an acrylate polymer. According to one embodiment, the matrix resin is selected from the group consisting of substituted and unsubstituted dimethacrylate and methacrylate. Some particularly advantageous matrix materials (monomers) are methyl acrylate, methyl methacrylate, methacrylate-functionalized dendrimers, glycidyl dimethacrylate (bis-GMA), triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA). These materials can be used as blends, and they can form interpenetrating polymer networks (IPNs). They can also be functionalized with bioactive molecules to produce the contact effect of similar drugs. The combination of monomer and polymer is also suitable for use, including modified resin systems containing iodine-containing antimicrobial side groups, which provides the additional benefit of enhancing radiopacity for the resin system. When matrix is biodegradable, any biocompatible and slowly biodegradable resin and polymer can be used.

The implant may further include modifier particles in the porous portion. These modifier particles may, for example, be bioactive and, for example, improve the osteoconductivity of the implant. The particles may be in the form of a particulate filler or fiber. The weight fraction of these modifier particles in the implant may, for example, be 5-30% by weight, such as 5, 10, 15, 20, or 25% by weight to a maximum of 10, 15, 20, or 30% by weight.

According to one embodiment, the modifier particles are selected from the group consisting of bioactive ceramics, silica gel, titanium gel, silica xerogel, silica aerogel, soda silica glass, titanium gel, bioactive glass ionomer, Ca/P doped silica gel and mixtures thereof. Of course, any combination of the materials described can also be used.

The porous portion of the implant may also contain other particulate filler materials, such as metal oxides, ceramics, polymers and mixtures thereof.Metal oxides may, for example, be used as radio- or X-ray opaque materials or as coloring materials.

The porous portion of the implant can also contain therapeutically active agents or cells such as stem cells, proteins such as growth factors and/or signaling molecules. Several cells including hematopoietic bone marrow cells, fibroblasts, osteoblasts, regenerative cells, stem cells, such as embryonic stem cells, mesenchymal stem cells or adipose stem cells can be seeded into the implant. Embryonic stem cells may or may not be human-derived. The stem cells seeded into the implant can be cultured in an ex vivo bioreactor, can be cultured in other parts of the body before the formed tissue is inserted into its final location, or can be cultured directly at the location where regeneration and reconstruction therapy is needed.

The size and shape of the implant are selected based on the intended use. The diameter of the implant can be, for example, 5 to 500 mm. According to one embodiment, the thickness of the implant is approximately 1.05 to 8.1 mm. The thickness of the implant generally depends on the thickness of the bone it is replacing. The porous portion generally forms the majority of the implant thickness, while the surface layer is significantly thinner.

The implant may also have different shapes, as will be explained in more detail in conjunction with the accompanying drawings. The implant may therefore have a substantially flat upper surface and an extension on another surface. The surface layer of the implant generally has a shape that conforms to the anatomical structure of the bone to be covered. Thus, the surface layer may be substantially flat, have a slightly concave form, or be substantially U-shaped (when used for long bones such as legs or arms).

The surface layer is typically such that its thickness is significantly smaller than the other two dimensions (the other two dimensions define the maximum surface area of the surface layer). The porous portion typically has a cylindrical or rectangular shape, i.e., its thickness is greater than the thickness of the surface layer relative to the other two dimensions. In addition, the surface area of the surface of the porous portion facing the surface layer is typically smaller than the surface area of the surface layer. In addition, according to a preferred embodiment, the porous portion is attached to the surface layer at a position where the surface layer extends beyond each edge of the porous portion. According to one embodiment, the porous portion is substantially attached to the middle of the surface layer.

Therefore, the surface layer typically extends beyond each edge of the porous portion. This allows the implant to be attached to bone or other tissue by any suitable means. For example, when used in brain surgery, the porous portion has essentially the same shape and thickness as the piece of skull removed during surgery. The surface layer has a slightly larger surface area, allowing the implant to be attached to the skull. In fact, the implant can be attached to the skull using screws at the edges of the surface layer. For example, the surface layer can be provided with small holes for attachment. In this way, the surface layer provides the porous layer with additional strength during healing and bone ingrowth, which will greatly improve the outcome of the surgery and the patient's quality of life during the healing period.

When viewed from the side, a typical implant thus has a surface layer on top, an outer surface (first surface) and an inner surface (second surface). A porous portion (the outer surface (first surface) facing the inner surface of the surface layer) is attached to the inner surface, i.e., below the surface layer. The implant does not contain any other parts other than these three parts (i.e., the surface layer, the porous portion, and the membrane layer made of collagen).

Implants can be used to rebuild bone in the trauma, defect or surgery of disease.By providing the immediate repair of the anatomical shape of bone and the sufficient mechanical support of the remaining bone blocks, blood and bone-forming cells are infiltrated into the implant from adjacent tissues to carry out the implant reconstruction for the damaged or missing part of the skeleton.Usually, demand exists in the skull bone defect after repairing neurosurgery and trauma, reconstruction of orbital floor and jaw, but implants can also be used for orthopedics and spinal surgery and fixation of bone fragments.When there is a long bone weakened due to disease or when part of the cortical bone is lost, implants can be used to strengthen the long bone and cover the opening of the cortical bone loss.

The implant is preferably manufactured as follows. First, a mold for the surface layer is made, either according to a standard or custom form. In the latter case, the custom form is typically obtained through medical imaging. The surface layer is then formed on the mold, for example by adding several layers of fabric or matting and a resin that forms a matrix. This step is well known in lamination technology. A separately manufactured porous portion is then positioned on the surface layer and cured. During the curing process, the porous portion adheres to the layer.

The surface layer may comprise one, two, three, four or five layers of textile material in the form of a fibre mat or a woven fibre fabric. When the aim is a thicker surface layer, more than five layers may of course also be possible.

The present invention also relates to the use of the implant according to the invention in dental and medical applications. Such uses are, for example, for the replacement of bones or the support of fractures. The specific embodiments and details listed above, together with the composite materials, also apply to such uses.

Some embodiments of the present invention are explained in more detail in the drawings, which should not be interpreted as limiting the scope of the claims. The reference signs should also not be interpreted as limiting the scope of the claims.

Experimental part

Example 1

Fabrication of implants with porous portions made of bioactive glass

Computed tomography (CT) was used to image the patient's cranial defect, and the CT data was used to create a virtual 3D reconstruction, which was used to design the shape of the implant's two components: a surface layer, which was anatomically shaped and made of a fiber-reinforced composite material; and a porous portion, which formed the inner surface of the bioactive glass. To create the surface layer, a mold of the implant's outer surface was made, and two layers of E-glass fiber fabric weighing ²²⁰ g/m² were laminated to the mold after impregnating the fabric with a bisphenol A resin system: a 50:50 glycidyl dimethacrylate-triethylene glycol dimethacrylate system with a thermal initiator system containing benzoyl peroxide. Simultaneously, the porous portion, made of bioactive glass, which would be adhered to the fiber-reinforced composite laminate, was manufactured as described below.

500-micron-sized bioactive glass granules of glass type S53P4 are sintered in a platinum mold at 600°C into an open-pore form within the skull. After sintering, the bioactive glass granules form the porous portion of the implant. After sintering at the aforementioned temperature, interconnected porosity with pore sizes ranging from 100 to 200 microns is present. The thickness of the bioactive glass portion is the thickness of the skull at that specific part of the skull, in this case 6 mm.

The porous portion of the implant is placed on a resin-impregnated fiberglass fabric in a mold. Excess resin penetrates the surface of the bioactive glass particles to a depth of less than 1 mm, so that the bioactive glass portion greater than 5 mm is not penetrated by resin. The resin is cured under vacuum at 110°C for 20 minutes, and the implant is then removed from the mold and completed. The implant is then sterilized and packaged.

Example 2

Fabrication of implants with porous portions made of hydroxyapatite.

The method for manufacturing an implant having a porous hydroxyapatite (HA) portion follows the method described in Example 1, with the exception of the manufacture of the hydroxyapatite portion (porous portion). A block of hydroxyapatite (Berkeley Advanced Biomaterials, Inc, USA) with an interconnected porosity of 100 to 200 microns was ground to the form and thickness of the opening in the skull. After grinding the HA block, it was adhered to the fiber-reinforced composite layer as described in Example 1.

Detailed Description of the Figures

In the following, the same reference numerals are used for the same or similar components in different embodiments and/or figures.

Figure 1 schematically illustrates an implant according to a first embodiment. The implant is placed in an opening in a patient's skull 1. The implant consists of a surface layer 4 and a porous portion 5 attached to its underside. The porous portion 5 essentially fills the hole in the skull. The implant is placed on the patient's dura mater 3 and brain 2. The surface layer 4 overlaps the skull 1 and therefore extends beyond each edge of the porous portion 5.

FIG2 schematically illustrates an implant according to a second embodiment. In this embodiment, the second inner surface of the porous portion 5 is further largely covered by a collagen membrane 6. This membrane 6 prevents the dura mater from penetrating the pores of the porous portion 5 of the implant and may be beneficial in clinical cases of prolonged elevated intracranial pressure.

FIG3 schematically illustrates an implant according to a third embodiment. In this embodiment, the implant is used to replace a missing portion of the femur following bone tumor surgery. The porous portion 5 of the implant fills the bone cavity, and a fiber-reinforced surface layer 8 made of a slowly biodegradable material strengthens the implant and gives it an anatomical shape.

Figures 4A and 4B schematically illustrate another embodiment. Figure 4A is a side view showing a surface layer 4, wherein the first surface of the surface layer is the surface shown as the upper surface in the figure, and the second surface is the surface opposite the first surface in the figure, i.e., the lower surface. The porous portion 5 is attached to the second surface of the porous portion 4, wherein the first surface is also the surface shown as the upper surface in the figure, and the second surface is the lower surface in the figure. If a membrane made of collagen is used, it will adhere to the lower surface of the porous portion, but it will not completely cover the lower surface of the porous portion.

FIG4A further illustrates, in dashed lines, openings 9 and 9' for attaching the implant to the patient's bone. FIG4B illustrates a top view of the implant of FIG4A. The porous portion 5 is shown in dashed lines below the surface layer 4, and each corner of the surface layer 4 is provided with an opening 9 and 9'. These openings can be used to attach the implant to the bone using screws.

Claims (13)

1. An implant comprising: - A surface layer composed of fibers and a matrix, having a first surface and a second surface opposite to each other, and having a thickness of up to 5% of the maximum dimension of the surface layer; - A porous biodegradable portion having a first surface and a second surface opposite to each other and having a thickness of 1-8 mm, wherein its first surface is attached to the second surface of the surface layer, and - A membrane layer made of collagen, the membrane layer having a first surface and a second surface opposite to each other, wherein the first surface is attached to the second surface of the porous portion and does not cover the edge of the porous portion. The porous portion comprises materials selected from the group consisting of bioactive glass, bioactive ceramics, hydroxyapatite, tricalcium phosphate, and mixtures thereof. 2. The implant according to claim 1, wherein the surface layer is non-biodegradable. 3. The implant according to claim 1 or 2, wherein the matrix is made of resin selected from polyester, epoxy resin, acrylate and mixtures thereof. 4. The implant according to claim 3, wherein the matrix resin is selected from the group consisting of substituted and unsubstituted dimethacrylates and methacrylates. 5. The implant according to claim 1 or 2, wherein the fibers of the surface layer are selected from S-glass fibers, E-glass fibers, carbon fibers, aramid fibers, and mixtures thereof. 6. The implant of claim 1, wherein the surface layer is biodegradable and its degradation rate is at least ten times greater than that of the porous portion. 7. The implant of claim 6, wherein the matrix is made of a polymer selected from polylactide, polycaprolactone polymers, polysaccharides, and mixtures thereof. 8. The implant according to claim 6 or 7, wherein the fibers of the surface layer are selected from bioactive glass fibers, sodium calcium metaphosphate fibers, cellulose fibers, hemp fibers, starch fibers, and mixtures thereof. 9. The implant according to claim 1 or 2, wherein the porous portion is cylindrical or rectangular. 10. The implant according to claim 1 or 2, wherein the diameter of the fiber is 4-25 μm. 11. The implant according to claim 1 or 2, wherein the thickness of the implant is 1.25-8.25 mm. 12. The implant according to claim 1 or 2, wherein the thickness of the membrane layer is 0.05-0.80 mm. 13. The implant according to claim 1 or 2, wherein the thickness of the surface layer is 0.2-4 mm.