Orthopedic implant having a crystalline calcium phosphate coating and methods for making the same

Abstract

An orthopedic implant having a metal surface and a calcium phosphate layer disposed on at least part of the metal surface is described. The calcium phosphate layer has an average crystallite size of less than about 100 nm in at least one direction and dissolves for more than 2 hours in vitro. The calcium phosphate layer is substantially free of carbonate. The coating, which is formed on a sodium titanate surface, has increased shear strength and tensile strength. The coating is formed by a solution deposited hydroxyapatite process under inert conditions. The pH of the solution varies by less than 0.1 pH unit/hour during coating formation.

What is claimed is: 
     
         1 . A calcium phosphate coating on a surface of an orthopedic implant, wherein the calcium phosphate coating has a surface area of about 15 m 2 /g to about 200 m 2 /g. 
     
     
         2 . The calcium phosphate coating of  claim 1 , wherein the calcium phosphate coating is substantially free of carbonate as measured by infrared spectroscopy.