EP2237808A2

EP2237808A2 - Open-pore biocompatible surface coating for an implant, method for producing the same, and use thereof

Info

Publication number: EP2237808A2
Application number: EP09707895A
Authority: EP
Inventors: Hans Schmotzer
Original assignee: Smith and Nephew Orthopaedics AG
Current assignee: Smith and Nephew Orthopaedics AG
Priority date: 2008-02-05
Filing date: 2009-01-22
Publication date: 2010-10-13
Also published as: WO2009097968A2; WO2009097968A3; DE102008044951A1

Abstract

The invention relates to an open-pore biocompatible surface layer for an implant, disposed on a raw surface of the implant, and an implant made of an open-pore biocompatible surface layer, wherein pores of the surface layer are filled at least partially, preferably at least 80%, and particularly preferably completely, with a bioactive, preferably resorbable filler material. The invention further relates to a method for producing such a surface layer and such an implant, and further, an implant having such a surface layer, and the use of such a surface layer according to the invention for an implant, or as an implant.

Description

Open-pore biocompatible surface layer for an implant, method of manufacture and use

Description

The invention relates to an open-pore biocompatible surface layer for an implant according to the preamble of patent claim 1, an implant according to the preamble of patent claim 2 and a method for producing an open-pore biocompatible surface layer for or as an implant according to the preamble of patent claim 18, an implant with or from such a surface layer according to the preamble of patent claim 23 and a use of the surface layer for implants according to the preamble of patent claim 24.

Implants and especially joint and bone replacement implants are becoming increasingly important in restorative and curative medicine. In the case of an implantation of joint or bone replacement implants, these are cemented cementlessly in the bone according to the current state of the art. A key factor in the success of such cementless anchoring of a metallic orthopedic implant to or in a bone is the rate at which bone tissue bonds to the implant. This speed is critically dependent on the type and structuring of the surface of the metallic implant. For this reason, such surfaces have in the past been provided with a predefined surface roughness, optionally additionally having a bioactive coating applied to the metal substrate of the metallic orthopedic implant. Porous layers, in particular open-porous structures, which have a pore size which allows ingrowth of bone tissue into these, usually metallic, structures have hitherto proven suitable for producing such surface layers which promote the growth of bone cells.

These porous structures have a thickness in the range of 1 mm or more in current joint and bone replacement implants. Such a thickness is necessary and useful with regard to a good and stable connection between bone and implant, but is problematic in that a good connection between implant and bone is only guaranteed if the porous structure is at least predominantly, but preferably completely, is crossed by ingrown bone tissue. Due to the high thickness of the porous structure, it is therefore essential in terms of achieving a good and stable connection between implant and bone that a ingrowth of bone tissue in the porous structure as quickly as possible take place so that contact between bone cells and porous structure possible forms quickly and comprehensively and stabilizes the connection between implant and bone in this way.

The ingrowth of bone into an open-porous structure represents a multi-step process in which bone cells together with blood vessels for nutrient and oxygen supply to the bone cells and the later bone in the pores of the open-porous structure must immigrate to the largest possible and stable connection of the bone cells and the later bone with the pores, respectively, to ensure the particular inner surface of the open-pore structure and thus the implant. However, an important aspect of ingrowing bone cells into a porous structure is the fact that bone cells can not migrate directly into an empty cavity, but always require a surface in the form of a substrate or matrix to which they adhere and along which they are divide and distribute and "move" in this way.

Heretofore, such bone tissue ingrowth-promoting surfaces have been provided in the form of porous surfaces which were either uncoated or provided with a thin surface coating which typically contained calcium phosphate.

However, in all of the aforementioned cases, the pores were so large in relation to bone cells that, although a lengthening of the bone cells along the pore matrix, ie their inner surface, took place, but the pores over a geraumen period hollow and vacancies that were not filled with bone tissue, since the bone was very slowly from the wall regions of the pores in the direction of pore cavity. However, this had the disadvantage that the bone on the implant or pore surface formed only a thin layer whose, in particular mechanical, stability was low, so that the connection between the implant and bone was not allowed or only extremely cautious , Only with complete ingrowth of the bone into the entire pore cavities, the latter being filled up with bone tissue, a stable and reliable connection between bone and implant was formed.

In order to accelerate the growth of bone on an implant according to the previous methods, a coating of the implant with hydroxyapatite, which was preferably applied by means of plasma spraying, was often performed. A disadvantage of this method, however, is that the pores of the implant layer starting only from the implant surface and only superficially can be coated with hydroxyapatite and the coating often does not reach to the bottom of the pore. Rather, there is the risk that the pores are clogged at the opening side when using this method, so that the pore bottom is no longer accessible for a coating. In addition, such a hydroxyapatite coating has a low solubility under physiological conditions so that bone cells can not penetrate into deeper layers of the coating and can not fully penetrate into the hydroxyapatite coating.

In particular, due to the risk of pore blockages when applying a hydroxyapatite coating on an implant using plasma spraying, a significant disadvantage of the method there is, inter alia, that only a coating of pores is possible, which extends from the implant surface substantially perpendicular to this extend. A coating of transverse pores in a three-dimensional pore network is not possible with this plasma spray coating method, so that a further disadvantage of the local method is that at best a bone growth to a joint replacement implant, but no actual bone ingrowth into a three-dimensional pore structure of an implant , as described for example in WO 2007/051519, is possible.

The object of the invention is to provide an open-pore biocompatible surface layer having a three-dimensional pore structure into which a rapid and space-filling ingrowth of osteoblasts is possible, as well as the provision of a method for producing such an open-pored biocompatible surface layer. Furthermore, it is the object of the invention to provide an implant with or consisting of such a surface layer as well as its use for implants.

This object is achieved by an open-pore biocompatible surface layer according to claim 1 and claim 2, by a method for producing an open-pore biocompatible surface layer according to claim 18 and by an implant according to claim 23 and a use of such a surface layer according to claim 24.

In particular, the object is achieved by an open-pored biocompatible surface layer, wherein pores of the surface layer are at least partially, preferably at least 30% and particularly preferably completely filled with a filling material.

According to a variant of the invention, this open-pored biocompatible surface layer is arranged on a raw surface of a substrate that is present as an implant or as an implant blank.

According to another variant, the open-pore biocompatible surface layer is self-supporting and forms the implant itself without the need for a substrate. The latter variant is particularly advantageous when the implant is not intended to carry out any essential supporting function but, for example, a filling and / or stabilizing and / or connecting function.

According to the invention, the open-pored surface layer can be formed entirely from a metal foam or have a metal foam. Such an embodiment is particularly advantageous in the case of a self-supporting structure of the open-pore biocompatible surface layer.

According to a preferred embodiment of the invention, the filling material is soluble under physiological conditions and / or, in particular by migrating osteoblasts, resorbable and preferably bioactive.

The essential essence of the invention is that by a filling of, in an open-pore biocompatible surface layer of an implant, existing pores with a filling material, the free pore volume of the pores in the surface layer is reduced, wherein the filler in turn preferably has a bioactivity and preferably by ingrowing osteoblasts and from these resulting bone tissue at least partially, preferably for the most part, can be absorbed. The filling material in turn has a micro- and nano-pore structure and / or a three-dimensional matrix structure into which ingrowth and migration of osteoblasts is possible. The free cross-section of these micro- and nano-pores is reduced by a factor in the range of 100 to 10,000 compared to the cross-section of the pores of the surface layer, so that in these micro- and nanopores ingrowing cells, for example osteoblasts, which receive the filler present there and / or Due to the small internal volume and the larger inner surface of the micro- and nanopores, these micro- and nanopores can be filled almost completely within a few days to weeks.

An important advantage of this surface layer according to the invention is, in particular, that a very large bioactive surface, which is optimally suitable for the growth of bone cells, is created by the filling material introduced into the pores of the surface layer. It should be noted that the term "micropores and nanopores" in the context of this invention, a three-dimensional matrix, for example in the form of a gel or in the form of a preferably surface-rich leaf, mesh or honeycomb structure, such as this example in a Silica gel, a pebble xerogel or silica sol as well as in silica hydrosols present.

Advantageously, the osteoblasts can migrate into this three-dimensional matrix or into the micropore space of the filling material and adhere and grow to solid constituents of the filling material. In this way, it is possible that a filling of the pore space of the surface layer emanates not only from a wall of pores of the surface layer, but also from the first empty according to the prior art space within the originally free, respectively empty pore volume of the surface layer pores, now However, according to the invention filled with the aforementioned bioactive and preferably resorbable filling material.

Since the ingrowth and multiplication of the osteoblasts now take place almost simultaneously in the entire pore volume of the surface layer, a generation of a strong, stable and resilient connection between bone and implant over the prior art is greatly accelerated, so that the bone or Bone and the implant much faster than before can fulfill its original function within the body again.

According to one embodiment of the invention, the pores of the open-pored surface layer are connected to form a coherent three-dimensional pore network, wherein the surface layer is formed as a framework structure and at least a plurality of pores via at least one lateral opening formed in a lateral boundary of the pore is, channel and / or tunnel-like communicate with each other in communication.

An embodiment of such a framework structure has proven to be particularly advantageous, since a particularly firm connection between the bone tissue and the framework structure and thus also the implant on which the framework structure is formed can be achieved by ingrowth of bone tissue into such a framework structure. In particular by tunnel-like interconnected pores takes place a mutual enclosure of skeletal structure material and bone tissue, so that such a compound can be claimed not only on pressure, but excellently on train without the bone cells detach from the implant surface, as a in the surface layer of ingrown bone tissue can completely penetrate the pore network and in this way builds up a bone structure which extends through the pore network and also runs within the surface layer or the framework structure. In this way, the ingrowing bone tissue traverses and undermines the surface of the surface layer or the contiguous pore network in a manner which ensures an intimate connection of the surface layer with the bone tissue and prevents detachment of the bone tissue from the surface layer, for example under tensile load.

The thickness of the surface layer or the framework structure according to the invention is in the range of 0.1 mm to 2.5 mm, preferably in the range of 0.3 mm to 1.9 mm and particularly preferably in the range of 0.5 mm to 1.5 mm.

Furthermore, the porosity of the surface layer, or framework structure, is in the range of 20% to 70%, preferably in the range of 30% to 60%, and more preferably in the range of 40% to 50%, it being understood that the porosity is within the Surface layer is formed substantially homogeneously, so that takes place within the entire surface layer, a uniform intergrowth of bone tissue with the framework structure of the surface layer. According to the invention, the maximum cross section of the pores of the surface layer is in the range from 10 .mu.m to 800 .mu.m, preferably in the range from 50 .mu.m to 600 .mu.m and more preferably in the range from 100 .mu.m to 300 .mu.m, the size of the pore cross section or the respective free volume of a pore according to an embodiment of the invention is approximately equally distributed within the surface layer.

According to an alternative embodiment, however, it can be provided that the closer the pore or the pore cavity is arranged to a raw surface of an implant blank, the smaller the pore volume, the smaller the pore volume, so that the pore cross-section, i. the free pore volume, decreases from an outer region of the surface layer in the direction of the raw surface of the implant, so that on the one hand an optimized anchoring of ingrown bone and also an optimized connection of the surface layer is ensured with an implant substrate. Depending on the implant type, or its intended use or application, such a pore volume gradient can also be provided in the opposite direction.

According to the invention, the surface layer, namely the framework structure, consists of a material that is not absorbable or absorbs slowly under physiological conditions, namely a metal and / or a ceramic and / or a polymer.

By the possibility of using different materials for the production of the framework structure, the implant can be adapted to the respective intended use, for example with regard to the type of implant. For example, a femoral component, which is usually subjected to a very high load, have a framework structure made of a metal, while a finger joint replacement may have a framework structure of ceramic and a component for a disc replacement a framework structure of a polymer. In this way, an implant can be individually adapted to a purpose, wherein a metal, for example, has a very high stability and toughness, while a ceramic can be lightweight, but very hard, and a framework structure of a polymer can have some flexibility.

In the case of the use of a metal framework structure, it is preferred that the framework structure or the surface layer is formed of preferably edged metal particles, titanium being the preferred material. These titanium particles are coated or bonded according to the invention with silicon particles, wherein silicon particles, for example by a superficial melting of the titanium particles may be compounded with these. The amount of silicon particles used for coating ranges from 0.5% to 8.5% by weight ± 1.5% by weight, preferably 0.5% to 3.0% Wt .-% and particularly preferably 1.0 wt .-% ± 0.5 wt .-%.

According to the invention, a titanium powder whose particles have a particle size in the range from 90 μm to <500 μm, preferably in the range from 150 μm to <300 μm, is preferably used as the titanium particle. The silicon particles used are preferably silicon powder having a particle size of ≦ 80 μm, preferably ≦ 40 μm and particularly preferably ≦ 20 μm, so that titanium particles coated with silicon particles are present as compound particles having an axial ratio of ≦ 5: 2. A particle size distribution measured in percent by volume with respect to particle size in accordance with ISO / DIS 13322-1 is given in the following table:

The coated with silicon particles titanium particles, which are present as compound particles, have a particle size of ≥ 90 microns, preferably ≥ 150 microns, wherein the above-defined particle size distribution is maintained.

According to a preferred embodiment, an intermediate layer is provided between the raw surface of the implant and the surface layer. Such an intermediate layer is useful, for example, if the base material of the substrate to be coated is not suitable directly for a coating by means of vacuum plasma spraying, such as a polymer or a ceramic, or an extremely high strength is required, depending on the respective Can apply application. In this case, the raw surface of the implant can first be coated with a dense base layer, which preferably consists of a bio-inert material, which is preferably a metal. As a metal is due to its bioinert properties and its very high strength and its low specific gravity titanium preferred. However, it is also silicon or compounded with silicon titanium into consideration. Other bioinert metals, such as tantalum, platinum, or other biocompatible metals, are also useful as basecoat materials, as in the following for the preparation of frameworks called metals.

Further, the metal used to make the framework structure may be titanium alloys. In addition, as another metal cobalt and / or alloys of this metal, stainless steel, in particular stainless steel, magnesium and / or alloys thereof, zirconium and / or alloys thereof, tantalum and / or alloys thereof, and mixtures and alloys of all of the aforementioned metals into consideration ,

If the framework structure is to be made of a ceramic, it is preferably selected from the group comprising alumina and zirconia, alumina-reinforced zirconia, zirconia-reinforced alumina and silicon nitride being materials suitable according to the invention. Further, additives may be added to these metal oxides. In addition, the ceramic can also be made of a mixture of these oxides.

If the framework structure is made of a polymer, this is selected from the group comprising polyetheretherketone (s) (PEEK), polyaryletherketone (s) (PAEK), polyimide (s) (PI), polyurethane (s) (PU), polycarbonate urethane (e) (PCU), polyetherimide (s) (PEI), polyethylene, especially ultra-high molecular weight polyethylene (UHMWPE), preferably crosslinked UHMWPE, polypropylene, and mixtures of these polymers.

As mentioned above, in particular for the case that the framework structure is made of a ceramic or a polymer, according to the invention an intermediate layer is provided which is provided between the raw surface of the implant and the surface layer, ie the framework structure. The intermediate layer is preferably made of titanium and has silicon; However, it can also consist of all other aforementioned metals or their alloys. The intermediate layer has a layer thickness of <200 .mu.m, preferably of <100 .mu.m and particularly preferably in the range of 30 .mu.m to 50 .mu.m.

According to the invention, the implant blank consists of one of the abovementioned metals, wherein, in particular, the raw surface of the implant blank has titanium and / or zirconium and / or alloys of these two metals. Another alloy from which the raw surface of the implant can be made is a biocompatible cobalt-based alloy.

In particular, the materials mentioned in the last section are characterized by a very high stability and good biocompatibility, so that they are predestined for use under physiological conditions.

The following substances are provided according to the invention as filling material for filling in the pores of the surface layer or the framework structure: calcium phosphate, in particular hydroxylapatite and / or tricalcium phosphate, bruschite (CaHPO ₄ .2H ₂ O), calcium sulfate, silicon oxide, in particular in the form of silica gel, preferably pebble xerogel, titanium oxide, gelatin, collagen, extracellular matrix proteins, growth factor (s), bone-forming protein (s), hydrogel (s), substance (s) having antibiotic activity and mixtures of the aforementioned substances.

The particle size of the optionally crystalline substances used as filling material is in the range of 0.005 μm to 50 μm, preferably in the range of 0.01 μm to 5 μm and particularly preferably in the range of 30 nm to 100 nm.

According to the invention, these substances can preferably be applied to the framework structure by precipitation or by electrophoresis using a sol-gel process with a water-based and / or silicate-based binder, preferably also in the form of a dip bath, and, if desired, into the pores of the framework structure are filled, with respect to the type of application is no restriction, as long as a filling of the pores at least partially, preferably at least 80% and particularly preferably completely guaranteed. According to one embodiment of the invention, the filling material introduced into the pores of the framework structure has micropores having an average free micropore cross section in the range of 0.1 nm to 100 μm, preferably in the range of 0.3 nm to 30 nm.

By means of the surface layer according to the invention or the scaffold structure according to the invention, a possibility is thus created to ensure an optimal anchoring of a bone on or in an implant, respectively its surface layer / framework structure, whereby a ingrowth of a bone into this surface layer or framework structure according to the invention This method greatly accelerates previous options and thus optimizes the success of an orthopedic procedure in which an orthopedic implant is to be anchored in or on a bone.

In principle, the surface layer or the framework structure can be produced in different ways; it should be emphasized, however, that depositing titanium particles by means of a vacuum plasma spraying method on a raw surface of the implant is preferred for generating the framework structure on the implant. Since the framework structure in this case is composed of individual interconnected metal particles, a variation of the type and size or dimensioning of the metal particles to each desired properties of the implant is well adaptable, since the particles are applied in layers and over a thermal process in regions, in particular pointwise, be connected to each other. In this way it is possible to produce a surface with a very good biocompatibility in the sense of a bioinert or slightly bioactive property, which has an inherently large inner surface as well as a very good mechanical strength and stability and also with regard to abrasion, even under abrasive stress only has an extremely low wear and therefore significantly increases and improves the life and comfort of implants, especially over the current state of the art.

Furthermore, the object is achieved by a method for producing an open-pored biocompatible surface layer for an implant, in particular joint and / or Bone replacement implant, as well as solved by a method for producing an implant consisting of such an open-pore biocompatible surface layer, wherein the following steps are carried out:

a) producing an open-pored biocompatible surface layer in the form of a framework structure, optionally on a raw surface of a plan Implan tat blank, and

b) filling of pores of the open-pored surface layer with a bioactive, preferably resorbable, filling material at least partially, preferably at least 30%, and particularly preferably completely.

According to the invention, step a), that is to say the production of an open-pored biocompatible surface layer in the form of a framework structure, is carried out by means of a vacuum plasma spraying method in which metal particles, preferably titanium particles, are applied to the raw surface of an implant blank, optionally directly above the raw surface of the implant Implant blanks initially an intermediate layer, preferably from one of the aforementioned metals, such as titanium, which is optionally provided with silicon, may be applied and thus not directly the raw surface of the implant blank, but the intermediate layer attached thereto is coated with the titanium particles. These metal particles used for producing the skeleton structure preferably have a sintering aid which forms an alloy with the respective metal which melts at a lower temperature than the pure metal used in each case. These metal particles are then applied, preferably by means of a vacuum plasma spraying method, to the raw surface of the implant or to the intermediate layer arranged on the raw surface of the implant for producing the framework structure.

Furthermore, a PVD (physical vapor deposition) method and / or a CVD (chemical vapor deposition) method can also be used to produce the framework structure, preferably metallic substances on the raw surface of the implant blank or on the intermediate layer applied thereon deposit. The latter two methods are particularly suitable for deposition of metallic substances on an existing framework made of a ceramic or a plastic. Of course, these two methods are also suitable to coat a framework of a metal structure.

According to one embodiment of the invention, the open-pore biocompatible surface layer is treated in the form of a scaffold structure by means of an arc which occurs between the raw surface of the implant blank and / or an intermediate layer on the implant blank and / or the framework structure on the implant blank, and a counter electrode is generated during and / or after application of metal, in particular titanium and / or compound particles.

According to the invention, the arc between the raw surface of the implant, or a surface layer located on the implant and a counter electrode can be applied directly to the implant during the application of the titanium and / or compound particles; Alternatively, however, the arc can also be applied after application of the titanium or compound particles. Another alternative is to use the arc process during and after application of the titanium and / or compound particles.

In the former case, namely in the case of the simultaneous application of the particles and the application of the arc, in addition to the internal, plasma-forming circuit of the coating process, a second circuit between a Plasmatron, respectively the plasma gun, and the component are switched, so that via the electrical conductive plasma a transmitted arc can be adjusted. It is also possible to generate the arc, not to produce it from the plasmatron or the spray gun, but by means of a provided counter electrode.

The use of an arc during or after the application of titanium or compound particles on a raw surface of an implant has the significant advantage of a JouPschen heating high resistance resistances, ie in this case at the contact points between the titanium or compound grains, respectively - on particles because these are constricted areas and thus an increased electrical resistance. In addition, especially in the case of Tensile layer of the sintering aid to the thus coated titanium particles is a higher ohmic resistance, as the titanium particles themselves, so that here Joule heat is produced, resulting in a limited local only to the points of contact of the grains heating, especially in the coating layer, through which the sintering necks connecting the particles are reinforced.

In summary, this heat released on the spot leads to additional local sintering and thereby to reinforcement of sintered necks between the titanium granules, without at the same time causing sintering and / or smoothening of the remaining regions of the particles and of the substrate surface. This advantageous effect causes in the coating a strong increase of their shear strength by a factor of 2 to 3 compared to the same coating parameters in the production, but without transferred arc. Compared to conventional coating methods, the joint use of a sintering aid and a transferred arc can achieve a six- to seven-fold increased shear strength compared to a pure, open-pored titanium layer.

It should be mentioned at this point that the arc is understood to be any type of energy action, in particular electrical, by means of which a JouFscher thermal effect can be achieved at narrowed points. A major advantage of using an arc, however, is that this immediately during the application of Titanbzw. Compound particles can be applied, so that the coating process ultimately runs in one stage and requires no additional process step, although a subsequent reinforcement of the sintering necks through the use of an arc is conceivable.

Moreover, it should be noted that the part of the contact resistance, which is due to the sintering aid, can be influenced by the choice of Sinterhilfsmittels and the thickness thereof according to the invention, so that a targeted very high solidification of the open-pore surface layer can be achieved with a contiguous pore network , Silicon or cobalt are preferably used according to the invention as sintering aid, if titanium is used as the material for producing the framework structure, silicon particles preferably containing silicon particles in an amount in the range from 0.5% by weight to 8.5% by weight. % ± 1.5 wt%, preferably 0.5 wt% to 3.0 wt%, and more preferably 1.0 wt% ± 0.5 wt%.

In the case of the use of other aforementioned metals for the preparation of the framework structure is used as a sintering aid another known from the prior art biocompatible metal which forms in a mixture with the base material of the framework structure, a low-melting alloy, such as a eutectic, to a superficial melting of the To allow to be applied metal particles.

Furthermore, an angular titanium powder having a particle size in the range from 90 μm to <350 μm, preferably in the range from 150 μm to <200 μm, which was preferably ground and inventively produced preferably via the hydride stage, is used as the titanium particle.

The silicon particles used are silicon powder having a particle size ≦ 80 μm, preferably <40 μm and particularly preferably ≦ 20 μm. With regard to the particle size distribution, reference is made to the above statements.

The titanium particles are coated with silicon particles in such a way that the coated titanium particles, which are now referred to as compound particles, have a particle size ≥ 90 μm, preferably ≦ 150 μm, again taking into account the predefined particle size distribution.

Because of these size ratios, it is possible to coat the titanium particles with silicon particles and thus to provide a high surface area which, in the event of subsequent melting during a vacuum plasma coating process, for bonding particles or for connecting particles to a substrate is available. Furthermore, it is possible to coat titanium particles with silicon particles in compliance with the abovementioned particle sizes so that an edged periphery of the coated titanium particles, ie the compound particles, is substantially retained and the compound particles have an axial ratio of <5: 2.

Furthermore, the vacuum plasma injection process parameters are adjusted so that the compound particles are only superficially melted and compacted when hitting the raw surface of the implant, respectively on the intermediate layer, if present, only slightly, so that their original geometry, in particular with respect to the axial ratio , largely preserved. In this way it is possible, by means of the angular particles which impinge on a substrate surface, to form a structure which is connected to each other substantially only over points and edges of the individual angular particles, so that a kind of cage is created in the form of a framework structure. from which the contiguous pore network is formed and through whose cavities bone substance can grow and grow.

As mentioned above, it is possible that the raw surface of the implant prior to a coating process with compound particles having a base layer, i. H. is coated with an intermediate layer, which may be formed depending on the base material of a raw implant body and preferably made of pure titanium and / or silicon-coated titanium.

According to a preferred embodiment, the application of the intermediate layer takes place in the same vacuum plasma spray coating process as the application of the actual surface layer, with the self-explanatory application of the intermediate layer before the surface layer is applied.

The base or intermediate layer is produced with a layer thickness of <200 μm, preferably of <100 μm, and particularly preferably in the range of 30 μm to 50 μm.

A surface layer or three-dimensional open-porous framework structure produced according to the above statements on preferably metallic implant materials brings three major advantages, which consist on the one hand that the micro roughness of the surface structure produced stimulating effect on ingrowing bone tissue. Furthermore, a macroroughness and the open-pored framework structure itself ensure a very good bond between ingrown bone and implant material, and moreover, the material thickness of the surface layer, respectively the framework structure, provides an optimally suitable thickness which is optimized as an integration zone for the ingrowth of bone material and a firm, resilient and secure hold of the bone on the implant, respectively, vice versa, ensures.

According to the invention, step b) is carried out by immersing the framework structure in a bath, preferably a sol bath, which contains the substances which serve as filling material for filling the pores of the surface layer. These substances are either dissolved in the bath and / or, preferably homogeneously, dispersed. In this way, a filling of the pores of the surface layer or the framework structure with the filler materials is easily possible because they can penetrate together with the liquid bath medium in the pores and cavities of the framework structure.

As filling material for filling the pores of the surface layer or the framework structure, substances are used which are selected from a group comprising: calcium phosphate, in particular hydroxylapatite and / or tricalcium phosphate, calcium sulfate, silicon oxide, in particular in the form of silica gel, preferably pebble xerogel , Titanium oxide, gelatin, collagen, extracellular matrix proteins, growth factor (s), bone-forming protein (s), hydrogel (s), substance (s) with antibiotic activity, optionally pharmacologically active substances, in particular inflammatory and / or or analgesic substances, as well as mixtures of the aforementioned substances.

Since these substances mentioned are used in a liquid solution or suspension, preferably in a silica-hydroxyapatite matrix, which is in its liquid state in this stage of the process, this liquid matrix can penetrate the pores of the surface layer or the framework structure well and completely so that for filling the pores of the surface layer or the framework structure only a it is necessary to immerse the surface layer or the framework structure or the entire implant in the bath containing the filler substance baths.

According to one embodiment of the invention, the penetration of the silica-hydroxyapatite matrix together with the filler substances into the pores of the surface layer or the framework structure can be assisted by auxiliary measures known from the prior art, which can be mechanical and / or electrical in nature. It is also conceivable that surface tension reducing agents are used to achieve, as far as possible, complete and rapid filling of the pores.

After the pores of the surface layer or skeleton structure are filled with the filler substances, the SoI, i. in particular the silica-hydroxyapatite matrix, which is present in the form of a mixture, heat-treated and dried, the silica initially solidifying to a gel in which the disperse silicas are arranged net, leaf or honeycomb with a surface-rich structure and by another Drying to a xerogel solidifies. In turn, this xerogel possesses micro- and nano-pores, which favor bone cell ingrowth and ingrowth, and provide good support due to the large surface area of the micropores.

It should be mentioned at this point that the method according to the invention can in principle be applied to any framework structure suitable for an implant, even if this framework structure is not present on a raw surface of an implant blank but is present alone or attached to another surface.

The foregoing performance of filler materials is not exhaustive at this point, but it should be emphasized that substances which are suitable, bone ingrowth and growth, as well as optional adjuvants and additives, may also be used as filler materials, with a selection of those to be used Substances and their respective concentration in the silica hydroxyapatite matrix, depending on the condition of the bone, in particular bone type and bone age, can be varied. Furthermore, it should be emphasized that these Füllmaterialsub usually punched easily and quickly by bone cells are absorbable, these Füllmaterialsubstanzen be at least partially absorbed into the bone cells, so that the pore volume of the surface layer or the framework structure is increasingly interspersed with bone, wherein the filling material substances are at least partially replaced, preferably for the most part, by this bone substance, so that in the optimal final state only more bone substance is present within the pore volume of the surface layer or the framework structure after the filling substance substances have been dissolved and / or absorbed and rebuilt by the bone cells and / or were taken up or removed via blood vessels also ingrown into the framework structure.

Furthermore, the object according to the invention is achieved by an implant, in particular joint replacement implant, which has a surface layer corresponding to the above specification and / or is produced by a method according to one of claims 14 to 18.

Furthermore, the object according to the invention is achieved by the use of a surface layer according to the above specification and / or the aforementioned manufacturing method, wherein the surface layer for hip shanks, shells for hip joints, femoral components for a knee replacement, tibial components for a knee replacement, components for a shoulder joint replacement, components for an elbow joint replacement, components for a toe joint replacement, components for a finger joint replacement, for a component for fusion of vertebrae of the lumbar spine, for components for a disc replacement, transgingival implant systems, for orthodontic implant systems and tooth replacement implants is suitable.

As already mentioned above, the surface layer according to the invention with its filled with filling pores for the above-mentioned areas of application in a very good manner, since a cementless anchoring of bone to the implants due to the excellent properties of the surface layer according to the invention, Namely, due to the micropores present in the filling material, is ensured, which ensure an optimized ingrowth and growth of bone on the surface layer and thus on the implant.

Further embodiments of the invention will become apparent from the dependent claims.

The invention will be explained in more detail with reference to the following exemplary embodiments.

Starting from a ground, edged titanium powder produced via the hydride stage, it is compounded in a first step with a small amount of a fine silicon powder. The titanium powder has a particle size of less than 350 microns and the silicon powder such a maximum of 65 microns. The resulting spray powder or the resulting compound particles consist of still edged particles with a maximum axial ratio of 5: 2. Next, this compounded powder is applied to the implant surface as an open-pored structure. The open-pore layer itself has a layer thickness of 0.5 mm to 1.5 mm and a porosity of 40% to 50%. The size of the pores, determined as the maximum diameter, is 150 μm to 400 μm. The opening of these pores against the outside is in the range of 150 microns to 500 microns. This layer is applied by means of a vacuum plasma spraying method and using a simultaneous arc. The plasma spray parameters are adjusted in this process so that the titanium particles are slightly melted, but are only slightly compacted upon impact with the substrate, namely the raw surface of the implant and already applied particles. The applied arc additionally bonds the deposited titanium particles together as well as the sintering necks connecting them and their connection to the substrate, i. the surface of the implant, reinforced. It creates a coherent network of mutually connected titanium particles and at the same time a coherent, internal porosity.

The porosity of the titanium layer applied by means of a vacuum plasma spraying method according to the invention is continuous up to an intermediate layer which is arranged above the raw surface of the implant. The intermediate layer serves an improved Adhesion of the surface layer, or the framework structure on the substrate and is formed as a thin dense titanium layer which has been deposited on the raw surface of the implant. This intermediate layer has a thickness of about 50 microns.

In the case of the subsequent application of an arc process to the substrate on which the particles are to be applied, this substrate serves as an electrode or grounding. By the arc, which couples into the applied particles, a JouPsche heating is generated at their junctions with each other and with the substrate, which represent a high-ohmic contact resistance, which causes a local sintering of these joints without the porosity and roughness in other areas of both the substrate and the applied particles is affected. Thus, the roughness and continuous porosity, which is optimally suited for ingrowth of bone tissue, sustained while the strength and cohesion of the particles with each other and with the substrate due to the application of the arc process is sustainably improved.

The vacuum plasma-sprayed layers, in particular in combination with the arc process, have a good adhesion to the substrate and with respect to the particles with one another and a good shear resistance within the layer.

After the open-pore biocompatible surface layer, or the framework structure, has been produced in the aforementioned manner, a filling of the pores of this surface layer or of the framework structure with a bioactive resorbable pore filling material is subsequently carried out. This consists of a silica xerogel with embedded hydroxyapatite particles having a size of 10 nm to 500 nm. This filling material also has extracellular matrix proteins, growth factors, bone-forming proteins, antibiotics, as well as gelatin and collagen. These substances are present in a liquid silica-hydroxyapatite matrix. To fill the pores of the surface layer or the framework structure, this is immersed in a bath, which is formed by the silica-hydroxyapatite matrix and the other ingredients. After the pores of the surface layer or the framework structure are filled with the liquid silica-hydroxyapatite matrix and its other ingredients, the surface layer or the framework structure is removed from the bath, the silica-hydroxyapatite matrix is dried and crosslinked by means of a thermal treatment. This thermal treatment forms a nanoporous xerogel matrix that has a loose network of polysilicic acid molecules and hydroxylapatite particles. This loose network is ideal for ingrowth of osteoblasts.

It should be noted that the scaffold structure according to the invention together with the filling material filling the pores of this scaffold structure can be used not only in connection with implants but also as bone filling material, if a scaffold structure filled with filling material is introduced, for example, into bone cavities, bone cracks or otherwise damaged bones , Also in this case filled with filling material framework structure is ideal for ingrowth of bone cells, the latter can grow from all sides in the framework structure or the filler, provided that it is freely accessible. This is the case if the framework structure is not arranged on a raw surface of an implant or on another surface, but is present as such.

It should also be mentioned that it is also possible to implement pharmacologically active substances in the filling material which can be taken up by the bone cells or released into the bloodstream and, for example, have an anti-inflammatory and / or bone growth-accelerating effect there.

The highly porous scaffold structure can be of any size and shape that is suitable, with rods, cylinders, blocks, and wedge-shaped scaffold structures being explicitly advantageous.

In summary, it can be stated that both the open-pore biocompatible surface layer according to the invention for an implant, an implant produced from this surface layer and the method according to the invention for producing the same constitute a new and advantageous technology compared with the prior art, by which a rapid and effective ingrowth of Bone cells in one open-porous surface layer is ensured. This is accomplished by providing within the pores of the open cell surface layer a matrix to which bone cells can adhere well and within which these bone cells can spread, divide and propagate well.

It should be noted at this point that all the parts described above are considered to be alone and claimed in each combination as essential to the invention. Variations thereof are familiar to the person skilled in the art.

Claims

Patsentansp

An open-pore biocompatible surface layer for an implant, which is arranged on a raw surface of the implant, characterized in that

Pores of the surface layer at least partially, preferably at least

30%, and most preferably completely, are filled with a filling material.

2. Implant consisting of an open-pore biocompatible surface layer, wherein pores of the surface layer are at least partially, preferably at least 30%, and more preferably completely, filled with a filling material.

3. Surface layer according to one of the preceding claims, characterized in that the filling material is resorbable or soluble under physiological conditions.

4. Surface layer according to one of the preceding claims, characterized in that etich et that the filling material is bioactive.

5. Surface layer according to one of the preceding claims, characterized in that the pores of the open-pored surface layer are connected to form a coherent three-dimensional pore network, wherein the surface layer is formed as a framework structure and wherein at least a plurality of the pores via at least one lateral opening, which in a lateral boundary of the pore is formed, channel and / or preferably tunnel-like communicate with each other.

6. Surface layer according to one of the preceding claims, characterized in that the open-pored surface layer is formed entirely from a metal foam or has a metal foam.

7. Surface layer according to one of the preceding claims, characterized in that the layer thickness of the surface layer on a raw surface of the implant in the range of 0.1 mm to 2.5 mm, preferably in the range of 0.3 mm to 1.9 mm and eichnet particularly preferably in the range of 0.5 mm to 1.5 mm.

8. Surface layer according to one of the preceding claims, characterized in that the surface layer, namely the framework structure, has a porosity in the range from 20% to 70%, preferably in the range from 30% to 60% and particularly preferably in the range from 40% to 50%.

9. Surface layer according to one of the preceding claims, characterized in that the maximum cross section of the pores is in the range from 10 μm to 800 μm, preferably in the range from 50 μm to 600 μm and particularly preferably in the range from 100 μm to 300 μm.

10. Surface layer according to one of the preceding claims, characterized in that the surface layer, namely the framework structure, consists of a material that is not absorbable or absorbs slowly under physiological conditions, namely a metal and / or a ceramic and / or a polymer.

11. Surface layer according to claim 10, characterized in that the surface layer is formed of, preferably edged, metal particles, in particular titanium particles, with an amount in the range from 0.5% by weight to 8.5% by weight ± 1.5 wt .-%, preferably 0.5 wt .-% to 3.0 wt .-% and particularly preferably 1.0 wt .-% ± 0.5 wt .-%, silicon particles coated, in particular compounded, are ,

The surface layer according to any of the preceding claims 10 or 11, characterized in that the metal is selected from a group comprising: titanium and / or alloy (s) thereof, cobalt and / or alloy (s) thereof, stainless steel in particular stainless steel, magnesium and / or alloy (s) thereof, zirconium and / or alloy (s) thereof, tantalum and / or alloy (s) thereof, as well as mixtures of said substances; the ceramic is selected from the group comprising: alumina, zirconia, alumina-reinforced zirconia, zirconia-reinforced alumina, silicon nitride, additives, and mixtures of said substances; the polymer is selected from a group comprising: polyetheretherketone (s) (PEEK), polyaryletherketone (s) (PAEK), polyimide (s) (PI), polyurethane (s) (PU), polycarbonate urethane (s) (PCU ), Polyetherimide (s) (PEI), polyethylene, in particular ultra-high molecular weight polyethylene (UHMWPE), preferably crosslinked UHMWPE, polypropylene, and mixtures of said substances.

13. Surface layer according to one of the preceding claims 1 and 3 to 12, characterized eichn et se, that between the raw surface of the implant and the surface layer, an intermediate layer is provided, the titanium and / or silicon, wherein the intermediate layer has a layer thickness of <200 microns , preferably of <100 microns, and more preferably in the range of 30 microns to 50 microns.

14. Surface layer according to one of the preceding claims 1 and 3 to 13, characterized in that the raw surface of the implant comprises CoCrMo and / or titanium and / or zirconium and / or alloys thereof.

Surface layer according to one of the preceding claims, characterized in that the filler comprises substances selected from the group consisting of: calcium phosphate, in particular hydroxylapatite and / or tricalcium phosphate, bruschite, calcium sulphate, silica, in particular in the form of silica gel , preferably pebble xerogel, titanium oxide, gelatin, collagen, extracellular matrix proteins, growth factor (s), bone-forming proteins, hydrogel (s), substance (s) with antibiotic activity, optionally pharmacologically active substances, such as in particular anti-inflammatory and / or analgesic substances , as well as mixtures of the aforementioned substances.

16. Surface layer according to claim 15, characterized in that a particle size of filling material used, optionally crystalline, substances in the range of 0.005 .mu.m to 50 .mu.m, preferably in the range of 0.01 .mu.m to 5 .mu.m and more preferably in the range of 0 , 03 μm to 0.5 μm.

17. Surface layer according to one of the preceding claims, as characterized by gekennz that the filling material filled in the pores of the framework structure has micropores and nanopores with an average free pore cross section in the range of 0.1 nm to 100 nm, preferably in the range of 0.3 nm to 30 nm.

18. A method for producing an open-pored biocompatible surface layer for an implant or an implant consisting of an open-pore biocompatible surface layer, in particular articular or bone replacement implant, characterized by the following steps: a) producing an open-pore biocompatible surface layer in the form of a framework structure, optionally on a raw surface an implant blank, and b) filling of pores of the open-pore surface layer with a, in particular bioactive, preferably absorbable, filler material at least partially, preferably at least 30%, and particularly preferably completely.

19. Method according to claim 18, characterized in that

Step a) by means of vacuum plasma spraying method and / or by means of PVD (physical vapor deposition) and / or by means of CVD (chemical vapor deposition) and / or carried out by means of sol-gel method and / or by sintering.

20. The method according to any one of the preceding claims 18 or 19, as by ge kennz eichnet that the framework structure is treated by means of an arc between the raw surface of the implant blank and / or an intermediate layer on the implant blank and / or the framework structure is produced on the implant blank, and a counter electrode during and / or after application of metal, in particular titanium and / or compound particles.

21. The method according to any one of the preceding claims 18 to 20, characterized gekennz eichnet that

Step b) is carried out by means of the following steps: b.l) immersing the framework structure in a sol bath in which filler substances are dissolved and / or dispersed; b.2) heat treating, drying and crosslinking the sol to form a porous xerogel.

22. The method according to any one of the preceding claims 18 to 21, characterized in that are used as filling material substances which are selected from a group comprising: Calciutnphosphat, in particular hydroxylapatite and / or tricalcium phosphate, calcium sulfate, silica, in particular in the form of silica gel, preferably pebble xerogel, titanium oxide, gelatin, collagen, extracellular matrix proteins, growth factor (s), bone-forming proteins, hydrogel (s), substance (s) having antibiotic activity and mixtures of the aforementioned substances.

23 implant, in particular joint replacement implant having a surface layer or consisting of a surface layer, characterized in that the surface layer according to one of claims 1 to 17 and / or formed by a method according to any one of claims 18 to 22.

24. Use of a surface layer and / or an implant according to one of claims 1 to 17, and / or prepared by a method according to one of claims 18 to 22 for hip stems, shells for hip joints, femoral components for a knee replacement, tibial components for a knee replacement, components for a shoulder joint replacement, components for an elbow joint replacement, components for a toe joint replacement, components for a finger joint replacement, for a component for fusion of vertebral bodies of the lumbar spine, for components for a Intervertebral disc replacement, for transgingival implant systems, for orthodontic implant systems, tooth replacement implants, and bone (replacement) implants.