Surface texture of hip implants

Four 36-mm CoCr femoral head implants were measured with both contact and noncontact systems. The analysis reviewed parameters that could improve surface characterization knowledge. Several 2D and 3D parameter calculations were made on unworn CoCr femoral heads that were manufactured by different processes. The 2D calculations were completed on a 24-mm trace taken through the apex of each femoral head. In general, the surface finish Ra ranges from 11 nm to 3 nm. Review of the surface finishes revealed that the Rsk ranges from negative to slightly positive. The 3D calculations were completed on a 0.9 mm² area taken from the apex of each femoral head. Close inspection of the heads showed a severe problem with pitting on the heads, which is invariably caused by a poor process. Data indicate that a 3D tool can identify issues with bearing surfaces that can be masked by a 2D profiling system.