Metal Implants
An implant with a metal structure for use in a surgical procedure, in which at least part of the metal structure is coated with a biocompatible metal such as titanium by plasma spraying of the metal powder. Biocidal metal cations are then absorbed by ion exchange into the coating, so that after being implanted the biocidal ions gradually leach out into the surrounding body fluids and suppress infection. The ion exchange properties of the coating may be modified by pretreatment with dilute phosphoric acid.
1 . An implant, the implant comprising a metal structure, wherein at least part of the surface of the implant incorporates a coating of a biocompatible metal deposited by plasma-spraying a powder of the biocompatible metal, and the coating incorporates biocidal metal cations in the coating.
2 . The implant of claim 1 wherein the biocidal metal cations comprise silver ions.
3 . An implant as claimed in claim 2 wherein the loading of silver ions in the coating is from 1 to 100 μg/cm 2 .
4 . An implant as claimed in claim 1 wherein the plasma coated structure is either anodized or treated with phosphoric acid.
5 . The implant of claim 1 wherein the plasma-coated structure containing biocidal metal is coated with hydroxyapatite.
6 . A method of making an implant, the implant comprising a metal structure, the method comprising the steps of plasma spraying a powder of a biocompatible metal on to at least part of the surface of the metal structure so as to form a coating of the biocompatible metal, and then contacting the coating with a solution containing a biocidal metal, such that cations of the biocidal metal are incorporated into the coating.
7 . A method as claimed in claim 6 wherein the coating is first contacted with phosphoric acid before being contacted with the solution containing the biocidal metal.
8 . A method as claimed in claim 6 wherein the coated structure is anodized prior to contacting with the solution of biocidal metal.
9 . A method as claimed in claim 6 wherein the plasma-coated structure containing biocidal metal is coated with hydroxyapatite.
10 . A method as claimed in claim 6 wherein the biocidal metal is silver.
11 . A method as claimed in claim 5 wherein additional biocidal metal cations are loaded into the hydroxyapatite.
12 . A method as claimed in claim 9 wherein the hydroxyapatite-coated structure is treated with a solution containing biocidal metal cations to incorporate at least some of the latter biocidal metal cations into the hydroxyapatite coating.