Gradient porous implant

An acetabular cup comprising:

• a bearing surface;
• and
• a generally hemispherical shaped shell having an inner solid substrate layer and a porous outer bone contacting layer surrounding said bearing surface, said porous outer bone contacting layer having a first porosity adjacent an equatorial region of said shell and a second porosity adjacent a polar region of said shell, said second porosity being greater than said first porosity,
• wherein said porous layer is thicker in said polar region than at said equatorial region, and
• wherein said pore size decreases continuously along said outer shell surface on moving from said polar region to said equatorial region.

An acetabular cup comprising:

• a bearing surface;
• and
• a shell surrounding said bearing surface, said shell having an outer generally hemispherical surface for contacting bone, said hemispherical surface having a pole and an equator, said shell having an inner solid substrate layer with a porous outer layer said porous outer layer having a first thickness and a first porosity adjacent an equatorial region of said hemispherical surface and a second thickness and a second porosity adjacent a polar region of the hemispherical surface, said second porosity and said second thickness being greater than said first porosity and said first thickness,
• wherein said thickness decreases sinusoidally on moving from said polar region to said equatorial region.