IMPLANT AND METHOD FOR COATING AN IMPLANT

Abstract

An implant, in particular a joint implant, has ultra-high molecular weight polyethylene as the base material and a coating thereon for oxidation and/or wear protection, the coating having a biocide layer and includes a barrier layer covering the biocide layer. Compared to the uncoated base material, the coating reduces both the access of oxygen to the base material and any material escaped from the base material.

Claims

1. An implant, with ultra-high molecular weight polyethylene as a base material and a coating located thereon, the coating comprising a biocide layer and a barrier layer covering the base material and, compared to the uncoated base material, is adapted to reduce both access of oxygen to the base material and exit of material from the base material, wherein the coating only partially covers the base material, at a surface section lying outside a sliding surface of the implant.

2. The implant according to claim 1, wherein the biocide layer comprises a biocidal active ingredient which is selected from the group consisting of silver, copper and zinc, ions thereof and metal complexes thereof, or a mixture or alloy comprising two or more of these elements.

3. The implant according to claim 2, wherein the barrier layer has a thickness and porosity adjusted to release the biocidal active ingredient from the biocide layer through the barrier layer in an antimicrobial, non-cytotoxic amount.

4. The implant according to claim 1, wherein the biocidal active ingredient has an average grain size of 5 to 100 nm, an average thickness of the biocide layer is 5 to 100 nm, and an average thickness of the barrier layer is 5 to is 500 nm.

5. The implant according to claim 1, wherein the barrier layer has a base material which is selected from the group comprising an organic base material, a sol-gel, a lacquer and a siliconized base material.

6. The implant according to claim 1, wherein the barrier layer has an inorganic base material which is selected from the group comprising SiO.sub.2, SiC, a metal oxide, and a non-biocidal metal.

7. A method for coating an implant, wherein a multi-layer coating comprising a biocide layer and a barrier layer is applied to ultra-high molecular weight polyethylene so that the coating only partially covers base material, at a surface section lying outside a sliding surface of the implant.

8. The method according to claim 7, wherein an oxygen-impermeable layer is applied as the barrier layer.

9. The method according to claim 7, wherein the polyethylene is cross-linked by beta or gamma radiation.

10. The method according to claim 9, wherein the polyethylene is cross-linked by radiation before the multi-layer coating is applied.

11. The method according to claim 9, wherein the polyethylene is cross-linked by radiation after the multi-layer coating is applied.

12. The implant according to claim 1, wherein the barrier layer has a base material which is selected from the group comprising a plasma polymer, a sol-gel, a lacquer and a siliconized base material.

13. The implant according to claim 1, wherein the barrier layer has an inorganic base material which is selected from the group comprising SiO.sub.2, SiC, TiO.sub.2, Al.sub.2O.sub.3, and titanium and medical grade stainless steel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] An exemplary embodiment of the invention are explained in more detail below with reference to a drawing. In the figures:

[0026] FIG. 1 shows a coated component of an implant in perspective view,

[0027] FIG. 2 shows further implant components in a sectional representation,

[0028] FIG. 3 shows in a diagram the depth-dependent oxidation index of a base material of the implant in comparison with an unclaimed comparison product.

DETAILED DESCRIPTION OF THE INVENTION

[0029] An implant, marked all together with reference numeral 1, is designed as an inlay of an artificial joint. Implant 1 has a modified hemispherical basic shape, with a spherical surface section 2 being adjoined by a frustoconical surface section 3. In the middle of spherical surface section 2, in the arrangement according to FIG. 1 at the uppermost point of implant 1, there is a disk 4, which is arranged concentrically to the central axis of the overall rotationally symmetrical implant 1 The end face of disk 4, designated 5, is provided with a coating 10, which serves to protect against wear and oxidation.

[0030] The coating 10, which is partially located on the outside of implant 1, is made up of a biocide layer and a barrier layer covering said biocide layer and is applied directly to the base material of implant 1. The base material of implant 1 is ultra-high molecular weight polyethylene, which was cross-linked using beta or gamma radiation.

[0031] Implant 1 is intended to be inserted into an outer part 6, which is visible in FIG. 2. Outer part 6, which, in contrast to implant 1, is made of a metallic material, has on its inside a concave surface section 7 and an adjoining conical section 8. The geometry of the sections 7, 8 is adapted to the shape of the spherical surface section 2 or the frustoconical surface section 3. On the outer surface of part 6, an intermeshing structure 9 can be seen in the area of conical section 8. In the middle of the inside of part 6 there is a central recess 11, which serves to insert disk 4 in a positive manner. A concavely curved recess on the outside of part 6, which is smaller in comparison to recess 11 and is also designed concentrically to the central axis of implant 1 and part 6, is designated 12. Furthermore, FIG. 2 shows an inner part 13 which interacts with implant 1 and has a spherical section 14 and an adjoining flange section 15.

[0032] In the diagram according to FIG. 3, a measurement curve MK shows the relationship between the depth x (in millimeters) below the surface of the base material of implant 1 and the measured oxidation index OXI. The measurements were carried out on samples that were artificially aged for two weeks. The samples were coated in multiple layers, as already described in connection with FIG. 1.

[0033] In addition, a comparison curve VK is plotted in the diagram according to FIG. 3, which refers to uncoated samples, whereinapart from the coatingthe preparation of the samples and the execution of the tests were carried out in the same way as in the case of the measurement curve MK. As can be clearly seen from FIG. 3, significantly better results were achieved with the coated samples than with the uncoated comparison samples in the entire measuring range, which is reflected in the fact that the measurement curve MK is significantly below the comparison curve VK. Coating 10 thus offers effective protection against oxidation of the base material, that is, ultra-high molecular weight polyethylene.

LIST OF REFERENCE NUMERALS

[0034] 1 implant [0035] 2 spherical surface section [0036] 3 frustoconical surface section [0037] 4 disk [0038] 5 end face [0039] 6 outer part [0040] 7 concave surface section [0041] 8 conical section [0042] 9 intermeshing structure [0043] 10 coating [0044] 11 central recess [0045] 12 outside recess [0046] 13 inner part [0047] 14 spherical section [0048] 15 flange section [0049] MK measurement curve [0050] VK comparison curve [0051] OXI oxidation index [0052] x [mm] depth in mm