Surface finish of metal joint replacement components

The surface finish of cobalt chrome metal joint prostheses is realized through MICROLOY®technology, which subjects the semi-finished components to various elaboration processes of CNC machining, subsequent processes of grinding and polishing until obtaining an extremely high degree of geometrical precision and roughness in order to reduce polyethylene wear.


The MICROLOY® surface treatment achieves very high degrees of geometric precision and low roughness values of metal surfaces which articulate with polyethylene components, with the aim of reducing polyethylene wear.

MICROLOY® finishing on the femoral condyles of the total knee prosthesis allows a 48% reduction of the polyethylene insert wear compared to traditional finishing treatments. [Gigante et al., 2013]

Permedica utilizes MICROLOY® technology for the surface finish of the following metal joint prostheses:

• GKS Prime – femoral components (condyles) and tibial components (tibial plate)
• GKS Prime Flex Mobile Bioloy – femoral components (condyles) and tibial components (tibial plate)
• GKS Prime Flex – femoral components (condyles)
• GKS One – femoral components (condyles)
• GKS Butterfly – tibial pivot and femoral bushnut
• Femoral heads in CrCo alloy
• Jump System double mobility insert


Traditional surface finishes of metal joint prosthetic components (knee femoral condyles and tibial plates, hip femoral heads and metal inserts) consist of surface grinding using multi-axial CNC machines (CNC; error ca. 50-100 μm), followed by manual polishing to obtain a surface roughness of Ra = 0,04 μm.

The principle limits of this traditional treatment is a shape error that is generated in respect to the theoretical shape of the prosthetic component.

Permedica MICROLOY® technology consists of high precision multi-axial CNC grinding which allows grinding of the component followed by mirror polishing of the metal surface, until obtaining roughness values similar to those of ceramic (Ra = 0,01 μm) completely eliminating all manual polishing operations and therefore any shape errors over 0,05 μm.