Bone prosthesis with porous coating

Claim 1

In a bone prosthesis comprising a substrate of a metallic material and a porous coating of said metallic material bonded to and extending over at least a portion of the surface of said substrate, with said porous coating consisting essentially of a multiplicity of spherical particles of said metallic material bonded together at their points of contact, and with said particles defining between themselves a plurality of connected interstitial pores extending through said porous coating to said surface of said substrate, the improvement wherein said porous coating consists essentially of first and second layers of said particles, with the particles in said first layer being bonded to said substrate and said first layer being bonded to said second layer, the particles in said first and second layers being distributed upon said substrate and said first layer, respectively, at substantially uniform surface densities and the particles in said first and second layers being of from +30 to -20 U.S. Standard mesh size, and the distribution of said particles in each of said layers is such that, as determined by mercury intrusion porosimetry, the average pore size in said porous coating is from 390 microns to 465 microns, the volume occupied by pores in said coating of up to 200 microns in pore size is no more than 20 percent of the total volume of porosity in said coating, and the volume occupied by pores in said coating of 800 microns or more in pore size is no more than 14 percent of the total volume of porosity in said coating.