Surface roughness of the proximal and distal bearing surface of mobile bearing total knee prostheses

Proximal and distal articulations Surface roughness measurements were done on 8 mobile bearing knee designs immediately after removal from sterile packaging. Roughness parameters Ra and Rp based on ISO 97, representing mean deviation from the smooth Surface line and mean peak to smooth surface line, were recorded using a contact surface profilometer at 10 random sites in the anteroposterior and mediolateral direction on the femoral and tibial metal components and the proximal and distal surface of the ultra-high molecular weight polyethylene (PE) inserts. No differences were found for surface roughness values for the metal components. Surface roughness values were greater for the distal PE bearing surfaces compared with the proximal PE bearing surfaces for each design tested. The roughness values for the PE inserts showed a directional dependence. Complex kinematics of mobile bearing knees coupled with this rougher distal interface could influence the rate of generation of wear particles and total volume of particles produced especially in the early postoperative period.