Barry Zide

Gas Cluster Ion Beam Polishing of Orthopedic Implants

One of the major causes of failure of orthopedic implants used in hip replacement surgery is the generation of excessive wear particles. These wear particles accumulate in the joint and initiate an autoimmune reaction which can weaken the bone-implant joint, leading to failure and revision surgery. The relatively poor implant surface finish created by current mechanical polishing techniques has been identified as a major cause of wear particle generation. Gas cluster ion beams (GCIB) have been successfully used to reduce the surface roughness of orthopedic implants. In GCIB, a high-pressure gas, such as argon, is supersonically expanded through a nozzle into vacuum. This adiabatic expansion results in the condensation of clusters consisting of tens to thousands of gas atoms weakly held together by Van der Waals forces. These clusters are then ionized and accelerated towards the target substrate. Upon impact, they create a strong lateral sputtering effect resulting in a net smoothing of the surface. Lapped flat coupons and production femoral balls made of ASTM 1537 cobalt-28 chromium-6 molybdenum surgical implant alloy were processed by GCIB utilizing gas clusters of argon and oxygen. Surface morphology was characterized before and after processing by atomic force microscopy and white light optical profilometry. As shown in Figure 1 GCIB processing was able to successfully remove asperities and create a tribologically improved surface on both flat test coupons and on production components.Copyright