COATING OF A STRUCTURED IMPLANT SURFACE

Abstract

An implant component which comprises a solid material region and a surface structure connected to the solid material region is disclosed. A coating is provided on the surface structure, said coating comprising, in addition to an At % proportion of Ti as a main component, at least one further coating component, wherein one of the at least one further coating components is silver having an At % proportion of 15-25 At %. The surface structure here comprises undercuts which are coated with said coating.

Claims

1. An implant component which comprises: a solid material region; a surface structure connected to the solid material region; a coating which is provided on the surface structure, wherein the coating comprises an At % proportion of Ti as a main component, and Ag having an At % proportion of 15-25 At % as a further component; and wherein the surface structure comprises undercuts which are coated with the coating.

2. The implant component according to claim 1, wherein the undercuts of the surface structure are at least partially formed by an open-pore structure.

3. The implant component according to claim 2, wherein the open-pore structure was generated by means of a plasma spray coating.

4. The implant component according to claim 2, wherein the open-pore structure comprises substantially regularly arranged unit cells and the unit cells are designed as tetrapod-like basic elements.

5. The implant component according to claim 2, wherein the open-pore structure has a porosity of 10% to 80% and/or a pore width of 45 μm to 1000 μm.

6. The implant component according to claim 1, wherein the surface structure is formed with a thickness of up to 4 mm, 3 mm, 2.5 mm, 2 mm, 1.5 mm, 1 mm or 0.5 mm.

7. The implant component according to claim 1, wherein the silver proportion of the coating is at least 18 At % and at most 25 At %.

8. The implant component according to claim 1, wherein the coating comprises an At % proportion of N and/or an At % proportion of Nb as a further coating component.

9. The implant component according to claim 1, wherein the is a Physical Vapor Deposition (PVD) coating.

10. The implant component according to claim 1, wherein the component Ag is present as islets in the coating.

11. The implant component according to claim 1, wherein the coating has a thickness of 1-6 μm.

12. The implant component according to claim 1, wherein the solid material region comprises an alloy comprising titanium.

13. A method for applying a coating onto an implant component, wherein the method comprises the steps of: providing of an implant component of claim 1, wherein the implant component is formed with a solid material region and with a surface structure connected to the solid material region, and the surface structure comprises undercuts; introducing of the implant component into a coating chamber; providing of at least one target made of a metallic material which comprises at least one of the coated components; locking of the coating chamber; providing of an atmosphere with a pressure of 0.001 to 0.01 mbar; igniting of an electric arc for evaporation of the metallic material of the at least one target; and coating of the surface structure with the evaporated metallic material of the at least one target.

14. The method according to claim 13, wherein the surface structure is formed by particles melted to one another, which surface structure is applied by means of a plasma spraying method onto the solid material of the implant component.

15. The method according to claim 13, wherein the surface structure is constructed from unit cells and formed by means of a layer melting method.

Description

DETAILED DESCRIPTION

[0060] In the context of the present invention, a coating is understood to mean a coating applied by a technical method. Examples of such technical methods are gas phase deposition (CVD—Chemical Vapor Deposition or PVD—Physical Vapor Deposition) or else plasma spraying methods such as, in particular, the already aforementioned titanium plasma spraying method.

[0061] As described above, a coating according to the invention includes titanium and silver, as well as up to two further coating components. For the sake of simplicity, such a coating is referred to below as titanium-silver coating, it being understood that said coating can also include further coating components. In addition, it is noted that the coating by the technical coating process can contain up to a proportion of 3%, 2% or 1% contaminants in the form of other elements or compounds. This also applies, in particular, to a coating which consists of certain coating components.

[0062] The application of the coating here occurs on a surface structure of the implant component. One method with which such a surface structure can be generated is a plasma spraying method. In the plasma spraying method, substantially in a vacuum, a plasma beam is generated, which is supplied with metal particles which melt in the high-energy beam and are accelerated. Subsequently, the molten metal particles strike the surface of the implant component and connect to it to a greater extent. The metal particles can comprise titanium or a titanium alloy or substantially consist thereof.

[0063] A surface structure generated by the plasma spraying method can have a roughness (Ra) in the range of 20 μm to 80 μm. In addition, a surface structure generated with this method comprises in particular undercuts.

[0064] It was noted that these undercuts are not sufficiently coated with a conventionally used antimicrobial coating for the desired effect to develop. It has then been assumed that this is in particular due to a lower silver proportion in this region.

[0065] In addition, a surface structure generated with a plasma method is can be porous. The porosity can be in a range of 10% to 60%, or in a range of 15% to 60%, or in a range of 20% to 50% (measured according to ASTM F1854).

[0066] In these ranges, in addition, a sufficient pore width for the ingrowth of tissue, in particular of bone tissue, can be provided. Thus, the surface structure in particular has pore widths in a range of approximately 45 μm to 80 μm, or in a range of 50 μm to 70 μm. The average pore width of all the pores can also be in this range (arithmetic average).

[0067] Another method generates the surface structure by means of an additive method. In particular, layer melting methods are suitable for this purpose, such as, for example, the already aforementioned electron beam layer melting method. The advantage of additive methods is that the surface structure can be formed in a defined and regular manner on the implant component. In the case of such an additive method, the solid material and the surface structure of the implant component can be produced substantially in the same production step.

[0068] As presented above, the surface structure can comprise unit cells, from which it is constructed. The unit cells in turn can be constructed from at least one element type, in particular from exactly one basic element type such as, for example, a tetrapod-like basic element. In this regard, reference is made in particular to the porous structures disclosed in patent application WO 2017/005514 A1, which is included hereby by reference.

[0069] One advantage of a porous structure produced with an additive method is that the porosity, the pore width, the pore size and/or the pore shape can be produced in a regular manner. In addition, the formation of the surface structure allows for predetermined mechanical properties such as, for example, a (direction-dependent) elasticity. Thus, the surface structure can be arranged in particular for a certain tissue such as, for example, bone tissue or connective tissue.

[0070] By an additive method, a predefined and in particular also higher porosity of the surface structure can also be produced. Thus, the porosity can be 50% to 80%, or 65% to 75% (measured according to ASTM F1854).

[0071] Furthermore, in an additive method, the sufficient pore width for the ingrowth of tissue, in particular of bone tissue, can be provided in a simple manner. Thus, the surface structure has in particular pore widths in a range of approximately 100 μm to 1000 μm, or in a range of 300 μm to 900 μm, or in a range of 500 μm to 800 μm. Due to the regularity of the structure, the average pore width is also substantially predetermined and deviates only little from the target size as a result of the production process (for example, the arithmetic average can deviate by less than 50 μm). In other words, the variance is lower in additive methods than in other methods such as, for example, in the aforementioned plasma spraying methods.

[0072] The pore sizes generated in the above methods can have a ratio between widest and smallest pore width which is less than 4:1, 3:1, or 2:1.

[0073] The coating of the surface structure comprises one, two or three layers of the coating, in which the silver is in embedded form. In particular, the silver is in the form of silver islets (silver agglomerates), i.e., silver or silver atoms are arranged next to the mesh of the remaining coating components. Due to the size of the silver atoms, it is assumed that only a small proportion of the silver, if any at all, is interstitially arranged in the mesh.

[0074] In particular, it was observed that the silver is in the form of silver agglomerates in the titanium-silver coating.

[0075] In other words, the silver is present in the mesh of the coating but not integrated therein. The silver agglomerates can be present in a range of 1 μm to 50 μm, or in a range of 5 μm to 30 μm.

[0076] Moreover, it is assumed that the efficacy of the silver arises in particular because the silver transitions in the implanted state of the implant component in contact with the body fluid by local unit formation into the ionic state and thus develops its antimicrobial effect. That this local unit formation can occur is very effectively made possible by an arrangement of these islets on the surface of the coating. This arrangement is achieved due to an at least partially simultaneous coating of the implant component with titanium nitride and silver.

[0077] The coating has an infection-inhibiting effect due to its antimicrobial properties. It is assumed that the present silver proportion of the coating disturbs the formation of a biofilm which these bacteria develop. Due to this disturbance, the protection brought about by this biofilm is then no longer sufficient for the bacteria, so that they can be attacked a greater extent by the immune system of patients or else by active ingredients.

[0078] Moreover, it was observed that the silver in ionic form can be dissolved out of this coating. It is assumed that these silver particles which are ionized on the surface of the coating, in the immediate surroundings of the implant component form an action zone (“inhibition zone”) in which they develop an antimicrobial effect. Consequently, not only is it possible with the coating to prevent an infection propagating directly from the surface of the implant component, but in particular it is also possible to prevent an infection in patient tissue adjoining the implant component.

[0079] The At % proportion of silver can be lower than the At % proportion of titanium. In other words, it is not necessary for a stoichiometric distribution to be present. The distribution can be superstoichiometric or substoichiometric.

[0080] The silver proportion, together with the proportion of titanium and possible further coating components, leads to a change of the mechanical properties compared to a coating without silver proportion, in addition to the aforementioned antimicrobial effect. In particular, the coating becomes softer and more ductile due to this structure.

[0081] It is assumed that, due to a ductility associated therewith, the mechanical resistance or strength of the coating furthermore is still sufficient to withstand the mechanical influences occurring during an implantation of the implant component. Such mechanical influences arise, for example during the generation of a press fit of an implant component in the bone tissue, due to contact of an implant component with a fastening element, such as, for example, during the screwing in of bone screws for fastening a plate, or during the mounting with another implant component, such as, for example, in a spondylodesis structure.

[0082] For this reason, the present coating is particularly suitable for implant components which, after implantation, support the skeleton of a patient or replace portions of this skeleton. In such implant components, a mechanical loading of the coating generally occurs during the implantation and the assembly of multiple implant components. After the implantation, in particular due to daily loading of the implant in the body of a patient, tensions and expansions in the coating occur due to elastic deformations. Here too, the present coating is advantageous since it withstands said deformations without losing its protective effect.

[0083] As described above, the coating components can be selected so that the coating is mainly suitable for implant components, wherein abrasion occurs mainly during the implantation of the implant component and/or the assembly of multiple components. It has been noted that, for this purpose, a thickness of the coating of less than 10 μm, in particular of 2.5-6 μm, 3.5-5.5 μm, or approximately 4.5 μm is sufficient. This also applies to the above-described TiNb—Ag coating which has a particularly high adaptability to a deformation of the surface structure.

[0084] Furthermore, in the present coating, due to the silver proportion, a difference of its material properties, in particular of the elasticity, compared to the underlying material of the surface structure can be partially reduced. A sufficient mechanical resistance and adhesion of the coating can also be promoted thereby.

[0085] In summary, the present coating for the surface structure of an implant component thus has both advantageous antimicrobial properties and advantageous mechanical properties which are useful for an implant component which is coated at least in sections with this coating.

[0086] Such a coating can be produced by the already aforementioned physical gas deposition (PVD method). Before the introduction into the coating chamber, the implant component provided with the coating, including its surface structure, can be cleaned with water.

[0087] The implant component is then introduced into the coating chamber which is subsequently evacuated. For the subsequent processes, the implant component can be heated to 400 to 600° C., in order to improve the motility of ions on the surface structure of the implant component and thus achieve a better adhesion and distribution of the coating on the surface structure and on a surface structure of the solid material, which is to be coated and possibly situated beneath.

[0088] Moreover, it is possible to carry out a cleaning of the implant surface by ion etching. Here, the implant component is bombarded with ions (for example, titanium ions, argon ions) under an inert atmosphere, in particular an argon atmosphere, in order to remove an oxide layer possibly present on the surface of the uncoated surface structure. A better adhesion of the coating on the surface structure of the implant component is also achieved thereby.

[0089] After this optional cleaning, the application of the coating onto the implant component under an atmosphere occurs. As for the atmosphere, in the case of the use of nitrogen as coating component, an atmosphere containing at least nitrogen is used. Otherwise, the coating occurs under an atmosphere substantially consisting of an inert gas.

[0090] As previously described above, this coating, depending on its desired composition, can be carried out with at least one silver target, at least one titanium target and at least one further target with a further coating component. Likewise, it is possible to use one or more targets comprising the At % proportions of silver, titanium and possibly further coating components provided for the coating. Here, the composition of the coating is consequently determined in particular by the composition of the at least one target.

[0091] In order to bring about a scattering of the evaporated target material on gas particles in the coating chamber so that they reach the surfaces of undercuts or pores to a greater extent, the coating occurs under the aforementioned low-pressure regions.

[0092] Once the desired atmosphere is set, the evaporation process of the at least one target starts. Particularly, an electric arc is used for this purpose, which dissolves material out of the targets due to a strong current by means of an electrical discharge and converts it into the gas phase. During this discharge, in particular voltages in a range of 15-30 V, or in a range of 20-25 V as well as currents in a range of 40-70 A are used. However, it is understandable to a person skilled in the art that other methods for evaporating the targets can be used, such as, for example, thermal evaporation, electron beam evaporation or laser beam evaporation.

[0093] At least during part of the coating process, when targets with different materials are used, the coating occurs simultaneously, in order to generate the above-described Ag islet structure.

[0094] Depending on the material of the surface structure, which is to be coated, a negative voltage of 100 V to 1500 V can be applied to said material in order to improve the adhesion and the layer homogeneity. To achieve the most uniform possible coating of the surface structure, the targets and the implant components can also be moved relative to one another during the coating process.

[0095] After the coating has occurred, and after a cooling phase, the coating chamber is ventilated again, and the coated implant component can be removed. The cooling can occur with the support of a gas atmosphere (for example, nitrogen or an inert gas) for improved heat removal, so that the cooling process is accelerated.