AU2008301028B2

AU2008301028B2 - Endoprosthesis component

Info

Publication number: AU2008301028B2
Application number: AU2008301028A
Authority: AU
Inventors: Helmut D. Link; Roger Thull
Original assignee: Waldemar Link GmbH and Co KG
Current assignee: Waldemar Link GmbH and Co KG
Priority date: 2007-09-17
Filing date: 2008-08-07
Publication date: 2013-04-04
Anticipated expiration: 2028-08-07
Also published as: BRPI0816831B1; ES2363111T3; CN101801315B; ZA201002205B; TWI457113B; IL204029A; DE502008003301D1; ATE506032T1; DK2190386T3; AR068525A1; BRPI0816831A2; WO2009036846A1; CN101801315A; MX2010002929A; EP2190386A1; EP2190386B1; JP5255640B2; PL2190386T3; AU2008301028A1; TW200920329A

Abstract

The invention relates to an endoprosthesis component (17) and a method for producing an endoprosthesis component (17). The endoprosthesis component (17) comprises a body (23) determining the shape of the endoprosthesis component (17). The body (23) is coated with an outer layer (25) on surface sections (22) that are in contact with human tissue when the endoprosthesis component is in the implanted state, said outer layer comprising a nitride, an oxynitride, or an oxide based on a refractory metal and comprising silver and/or copper. According to the invention, an intermediate layer (24) is disposed between the outer layer (25) and the body (23) such that parts of the intermediate layer (24) are accessible from the exterior. The endoprosthesis component (17) is produced using the method according to the invention. The invention allows the outer layer (25) to be used to create a long-term antimicrobial action and, in addition, allows the intermediate layer (24) to act on the surrounding tissue.

Description

Endoprosthesis component The invention relates to an endoprosthesis component 5 with a body predefining the shape of the endoprosthesis component. On surface portions with which the endopros thesis component in the implanted state is in contact with human tissue, the body is covered with an outer layer. The outer layer comprises a nitride, an oxyni 10 tride or an oxide based on a refractory metal; further more, the outer layer contains silver and/or copper. The invention further relates to a method for producing such an endoprosthesis component. 15 Endoprosthesis components used to replace parts of the human skeleton must satisfy a number of requirements. The endoprosthesis component has to be sufficiently stable to ensure that it can take up the forces that occur in the skeleton. In addition, those elements of 20 the endoprosthesis component that are in contact with the tissue, including bone substance, of the human body in the implanted state must have good biocompatibility. It is already known for surface portions of the endo 25 prosthesis component that are designed for contact with human tissue to be covered with a layer composed of a hard material, for example a nitride, an oxynitride or an oxide based on a refractory metal. Hard material coatings of this kind combine good mechanical properties 30 together with good biocompatibility. However, problems occasionally arise concerning the ac ceptance of such endoprosthesis components by the human body. For example, microorganisms may attach themselves 35 to the surface of the endoprosthesis component and in 4054115 1 (GHMatters1 P83373 AU so doing hinder the acceptance of the endoprosthesis component in the human body. The risk of microorganisms on the surface of endoprosthesis components is greater, the more invasive the procedure needed to implant the 5 endoprosthesis component into the body, and the greater the surface area across which the endoprosthesis compo nent comes into contact with the tissue of the body. Operations in which an invasive procedure is needed, and in which the endoprosthesis is brought into contact 10 with human body tissue across a large surface area, are, for example, head/shaft prosthesis shafts, or those in which the femur is replaced completely by an endoprosthesis. 15 It is known from WO 03/094774 to oxidize the surface of an implant, made of metal or a metal alloy, and to pro vide the resulting hard material layer with silver par ticles in order to obtain an antimicrobial action. Since hard material layers react only very slowly with 20 the surrounding body tissue, the silver particles are released from the hard material layer over a long pe riod of time. A hard material coating of this kind can therefore provide good long-term action. Directly after insertion of the implant, however, a large number of 25 microorganisms may be present in the environment of the implant. The quantity of silver particles released by the hard material layer is too small to be effective against a larger number of microorganisms. 30 It would be advantageous if the present invention would make available an endoprosthesis component of the type mentioned at the outset and a method for producing such an endoprosthesis component, where there is less chance of the acceptance of the endoprosthesis component in 35 the human body being hindered by microorganisms. 2 The present invention provides in a first aspect an endoprosthesis component which comprises a body prede fining the shape of the endoprosthesis component and in 5 which, on surface portions with which the endoprosthe sis component in the implanted state is in contact with human tissue, the body is covered with an outer layer which comprises a nitride, an oxynitride or an oxide based on a refractory metal, the outer layer containing 10 silver and/or copper wherein an intermediate layer is arranged between the outer layer and the body and wherein parts of the intermediate layer are accessible from the outside. 15 A number of terms will first be explained. A body that predefines the shape of the endoprosthesis component differs from the shape of the endoprosthesis component, at least in the area in which the surface of 20 the endoprosthesis component is designed for contact with human tissue, only in terms of coatings that are additionally applied to the surface. It is not generally the entire surface of the endopros 25 thesis component that is designed to establish a con nection to human tissue. Instead, the endoprosthesis component may comprise areas on its surface that are designed to interact, for example, with a further endo prosthesis component, for example in order to form a 30 joint. In the context of the invention, it is not nec essary for the entire area of the surface designed for contact with the human tissue to be covered with an outer layer or an intermediate layer. Instead, it may suffice if surface portions of these areas are covered 35 with an outer layer and/or an intermediate layer. 3 The outer layer is understood as a layer that is in di rect contact with the environment. An outer layer, therefore, is not covered by a further layer. The outer 5 layer does not have to provide full surface coverage; it may also have interruptions or may be applied only as islands. An intermediate layer is covered at least on parts of 10 its surface with an outer layer. In areas where no outer layer is applied or where the outer layer has in terruptions, the intermediate layer itself is in direct contact with the environment. The intermediate layer is therefore partially accessible from the outside. On the 15 surface of the endoprosthesis component, locations where the intermediate layer is accessible from the outside alternate with locations where the intermediate layer is not accessible from the outside. The interme diate layer is made of a different material than the 20 material from which the endoprosthesis component is made. The term human tissue is to be understood widely. It includes all elements of the human body with which an 25 endoprosthesis can come into contact, for example in cluding bone too. Refractory metals are base metals with high melt points from the fourth, fifth and sixth side groups. These in 30 clude titanium, zirconium and hafnium from the fourth side group, vanadium, niobium and tantalum from the fifth side group, and chromium, molybdenum and tungsten from the sixth side group. Refractory metals that are especially suitable for the coating of endoprosthesis 35 components are titanium, zirconium, niobium and tanta 4 4054115 1 (GHMatter) P83373.AU lum. Nitride, oxynitride or oxide based on a refractory metal are understood as compounds that ions of a re fractory metal form with oxygen and/or nitrogen as re active gas. These compounds are distinguished by great 5 hardness; the layer obtained is therefore also referred to as hard material layer. If the outer layer additionally comprises silver and/or copper, the formation of the nitride, oxynitride or ox 10 ide involves not only ions of the refractory metal and a reactive gas, but also silver and/or copper ions. The silver and/or copper ions are integrated into the coat ing obtained. The outer layer has a long-term antim icrobial action through the silver and/or copper con 15 tained. The antimicrobial action is combined with good mechanical properties such as hardness and high abra sion resistance. By providing an intermediate layer between the outer 20 layer and the body, which intermediate layer is par tially accessible from the outside, it is possible for the surface of the endoprosthesis component not only to have the long-term antimicrobial action of the hard ma terial coating, but also other effects. Thus, for exam 25 ple, the intermediate layer may be designed such that it releases a higher dose of an antimicrobial substance within a short time. The higher dose then acts against infections directly after the operation. 30 The body predefining the shape of the endoprosthesis component may be made of metal or of a metal alloy. Particularly suitable metals are titanium and titanium alloys. The term outer layer also includes a layer that has been created in several application runs. The ap 35 plication of a layer in several application runs will 5 4054115 I (GHMattersI P83373 AU be considered particularly in cases where the layer created in one application run is too thin. The intermediate layer may be a layer of silver, copper 5 and/or gold. The intermediate layer preferably gives full surface coverage. Such an intermediate layer cor rodes much more quickly than the hard material of the outer layer when in contact with human tissue. A higher dose of antimicrobial particles is therefore released. 10 In areas where the intermediate layer is accessible from the outside, the outer layer is interrupted. The interruptions may have diameters of just a few pm or may be much larger. In the case of microscopic inter 15 ruptions with a minimum diameter of just a few pm, this is referred to as a porous outer layer. Macroscopic in terruptions with diameters in the mm range, for exam ple, permit access to the intermediate layer from the outside over a larger surface area. In particular, the 20 outer layer may be designed such that the interruptions take up a proportion of at least 20% of the surface, preferably at least 40%, more preferably at least 60%. The antimicrobial action may be strengthened if the 25 outer layer has a microstructure or nanostructure with distinct peaks. A distinct peak in a surface structure is understood as a formation in which the surface, starting from one extreme, falls off in all directions at an angle of more than 45 degrees relative to the di 30 rection of the surface. Electrically conductive peaks, compared to smooth surfaces, generate a strong electric field in their environment, which field has a negative effect on microorganisms. 6 An aspect of the invention further relates to a method for producing such an endoprosthesis component. To pro duce the endoprosthesis component, a body is first made ready that predefines the shape of the endoprosthesis 5 component. Surface portions of the body that are in tended for a connection to human tissue are provided with a coating which, although at this time not yet covered with an outer layer, will, however, be referred to as intermediate layer for the sake of simplicity. No 10 particular requirements are placed on the surface structure of the intermediate layer. The surface may therefore be smooth, macrostructured, micro-structured or nanostructured. 15 Moreover, targets are made ready from which the mate rial later to form the coating may be released. It is possible to make available a single target, which com prises both the refractory metal and also the silver and/or copper. It is also possible, however, to make 20 available several targets, in which case a first target comprises a refractory metal, and a second target com prises silver and/or copper. Ions of the refractory metal and ions of silver and/or 25 copper are released from the one or more targets. In order to release the ions, for example, an electric arc may be generated between an electrode and the target, which electric arc delivers so much energy to the tar get that ions are released. Another possible way of de 30 livering sufficient energy locally to the target may be to direct a laser beam at the target. One alternative, albeit an expensive one, is for the energy to be deliv ered by an electron beam. 7 The free ions are conducted, together with a reactive gas, onto surface portions of the body covered with the intermediate layer in such a way that an outer layer forms through which the intermediate layer is accessi 5 ble. To do so, a voltage may be applied between the target and the body so as to accelerate the ions in the direction of the body. The reaction vessel with target and body contains a reactive gas, for example oxygen or nitrogen, or a mixture of oxygen and nitrogen. The ions 10 of the refractory metal and the ions of silver and/or copper react with the reactive gas, and molecules are formed which contain all three constituents. In one em bodiment, TiAgN molecules are formed. The outer layer according to an embodiment of the invention occurs as a 15 result of the reaction taking place on the surface of the body. The reaction may take place under vacuum, preferably under high vacuum. Methods of this kind are referred to as plasma coating methods. An improved hold of an applied layer can be achieved if the surface of 20 the body is treated beforehand by sand-blasting. There are several options by means of which it can be ensured that the outer layer forms such that the inter mediate layer remains accessible. For example, a porous 25 outer layer having microscopic interruptions can be generated by delivering so much energy to the single target or the several targets that not only ions are released from the targets, but also fragments with a maximum diameter of over 20 pm. The fragments move ran 30 domly in all directions and impinge on that surface of the body on which the outer layer forms. At the loca tions where the fragments impinge, a piece of the form ing outer layer is struck out. A porous outer layer forms through which the intermediate layer is accessi 35 ble. 8 anl51 , i (lHM.re.I P3373 AU Another possible way of ensuring accessibility to the intermediate layer is to use a mask made of tempera ture-stable material to cover the surface portion of 5 the body that is to be coated. The mask covers parts of the surface and leaves other parts of the surface free. The mask may, for example, have a mesh-like or lattice like form. The outer layer then only forms as islands at the places that are left free by the mask. After the 10 temperature-stable material has been removed, the in termediate layer is accessible in accordance with the mask. A material is referred to as being temperature stable when it is resistant to the conditions that arise in plasma coating methods. The temperature-stable 15 material may, in particular, be a metal. If the parameters of the plasma coating method are suitably chosen, an outer layer is obtained that has a microstructure or nanostructure with distinct peaks. 20 If the intermediate layer is made of silver, copper and/or gold, it may likewise be applied by means of a plasma coating method. Alternatively, it is possible to apply the intermediate layer to the body by means of 25 electrochemical deposition. The present invention further provides in an aspect a method for producing an endoprosthesis component, with the following steps: a. Making available a body that predefines the 30 shape of the endoprosthesis component, surface portions of the body, which are intended for a connection with human tissue, being provided with an intermediate layer; 9 4054115 1 (GHMatters) P83373.AU b. Making available a refractory metal and also silver and/or copper in the form of one or more targets; c. Releasing ions of the refractory metal and 5 also ions of the silver and/or copper from the one or more targets; d. Conducting the ions, together with a reactive gas, onto surface portions of the body covered with the intermediate layer, so that an outer layer forms 10 through which the intermediate layer is accessible. The invention is described by way of example below on the basis of an advantageous embodiment and with refer ence to the attached drawings, in which: 15 Fig. 1 shows an endoprosthesis comprising several endo prosthesis components; Fig. 2 shows an endoprosthesis component according to 20 the an embodiment of the invention; Fig. 3 shows an enlarged detail from a cross section through Fig. 2; 25 Fig. 4 shows the view from Fig. 3 in the case of an other embodiment of the invention; Fig. 5 shows the view from Fig. 3, in the case of a further embodiment of the invention; and 30 Fig. 6 shows an enlarged detail of the surface of the endoprosthesis component according to Fig. 2, in the case of one embodiment of the invention. 10 405411S i (GHMattes) P83373.AU An endoprosthesis shown in Fig. 1 is designed to re place a part of the human skeleton reaching from the hip to below the knee. A spherical joint head 10 forms an articulation surface that is designed to interact 5 with an acetabulum. The joint head 10 is connected to a head piece 11 of the endoprosthesis by a screwed con nection. The part of the endoprosthesis replacing the shaft of the femur comprises three endoprosthesis com ponents 12, 13, 14. The endoprosthesis components 12, 10 13, 14 are connected to one another and also to the head piece 11 by screwed connections. A knee piece 15 forms an articular connection to a shaft 16, which is designed to connect the endoprosthesis to a tibia. 15 The endoprosthesis components 12, 13, 14 are available in different lengths, such that the endoprosthesis can be adapted to different lengths of femurs. Fig. 2 shows an endoprosthesis component 17, corresponding to the endoprosthesis components 12, 14, 14, in an enlarged 20 view. The endoprosthesis component 17 comprises a screw pin 18, and a screw hole 19 indicated by broken lines. By way of the screw pin 18 and the screw hole 19, the endoprosthesis component 17 can be connected at its two ends to similar endoprosthesis components, for example 25 the endoprosthesis components 12, 13, 14. The screw pin 18, the screw hole 19 and the adjacent end faces 20 and 21 thus form areas of the surface of the endoprosthesis component 17 that are designed to interact with other endoprosthesis components. By contrast, the lateral 30 surface 22 of the endoprosthesis component 17 is de signed to make contact with human tissue in the im planted state. In the area of the lateral surface 22, the body 23 pre 35 defining the shape of the endoprosthesis component 17 11 Andi 1 t(tHMttarm P83373 AU is covered with an intermediate layer 24 and an outer layer 25. The intermediate layer 24, composed of sil ver, completely covers the body 23 in the area of the lateral surface 22. The outer layer 25 covering the in 5 termediate layer 24 is a hard material coating which was created by means of a plasma coating method from titanium, nitrogen and silver. In the illustrative embodiment shown in Fig. 4, the 10 outer layer 25 is porous. The intermediate layer 24 can exert an antimicrobial action on the surrounding tissue through microscopic interruptions in the outer layer 25. 15 Fig. 6 shows a plan view of the lateral surface 22 of the endoprosthesis component 17 in an enlarged repre sentation. The intermediate layer 24 is covered by the outer layer 25 only in individual islands. The outer layer 25 thus has macroscopic interruptions through 20 which the surrounding tissue can come into direct con tact with the intermediate layer 24. In the areas in which the outer layer 25 is applied to the intermediate layer 24, the intermediate layer 24 can be dense as shown in Fig. 3 so that no direct contact exists be 25 tween the surrounding tissue and the intermediate layer 24. In Fig. 5, the outer layer 25 has a nanostructure with pronounced peaks 26. With electrically conductive peaks 30 26, an electric field forms around the peaks 26 and strengthens the antimicrobial action of the outer layer 25. The intermediate layer is not shown in Fig. 5. 12 anSS1 I rnHUManlarsl PA3373 AU

Claims

1. An endoprosthesis component which comprises a body 5 predefining the shape of the endoprosthesis component and in which, on surface portions with which the endoprosthesis component in the implanted state is in contact with human tissue, the body is covered with an outer layer which comprises a nitride, an oxyni 10 tride or an oxide based on a refractory metal, the outer layer containing silver and/or copper wherein an intermediate layer is arranged between the outer layer and the body and wherein parts of the interme diate layer are accessible from the outside. 15

2. The endoprosthesis component as claimed in claim 1, wherein the intermediate layer is composed of silver, copper and/or gold. 20

3. The endoprosthesis component as claimed in claim 1 or 2, wherein the outer layer is interrupted, and wherein the interruptions occupy a proportion of the surface area of at least 20%, preferably of at least 40%, more preferably of at least 60%. 25

4. The endoprosthesis component as claimed in any one of claims 1 through 3, wherein the outer layer is po rous. 30

5. The endoprosthesis component as claimed in any one of claims 1 through 4, wherein the outer layer has a mi crostructure or nanostructure with distinct peaks.

6. A method for producing an endoprosthesis component, 35 with the following steps: 13 a. Making available a body that predefines the shape of the endoprosthesis component, surface portions of the body, which are intended for a connection with human tissue, being provided with 5 an intermediate layer; b. Making available a refractory metal and also silver and/or copper in the form of one or more targets; c. Releasing ions of the refractory metal and 10 also ions of the silver and/or copper from the one or more targets; d. Conducting the ions, together with a reactive gas, onto surface portions of the body covered with the intermediate layer, so that an outer 15 layer forms through which the intermediate layer is accessible.

7. The method as claimed in claim 6, wherein the ions are released from the one or more targets by means of 20 an electric arc.

8. The method as claimed in claim 6, wherein the ions are released from the one or more targets by means of laser. 25

9. The method as claimed in claim 6, wherein the ions are released from the one or more targets by means of an electron beam. 30

10. The method as claimed in any one of claims 6 through 8, wherein, in step a), a body is made avail able in which the intermediate layer consists of sil ver, gold and/or copper. 14 4054115 1 (GHMatters) P83373 AU

11. The method as claimed in any one of claims 6 through 9, wherein, in step c), fragments with a di ameter of more than 20 pm are additionally released from the target, and wherein, in step d), the frag 5 ments are conducted onto the body.

12. The method as claimed in any one of claims 6 through 10, wherein, before step d), the surface por tion of the body to be coated is covered with a mask 10 made of a temperature-stable material.

13. An endoprosthesis is substantially as herein de scribed with reference to any one or more of the drawings. 15

14. A method substantially as herein described with reference to any one or more of the drawings.

15 An'1I% I1 IGHMattersi P83373.AU