The goal of Phase II is to further establish the safety and efficacy of depositing a zirconia coating on cobalt-chromium (Co-Cr) alloy orthopaedic components to substantially decrease wear of the mating polyethylene part. More than 350,000 total knee and total hip replacements are presently performed in the U.S. each year. In several recent review articles, 1-4 UHMWPE wear debris and the accompanying granuloma formation were identified as the primary complications in long range joint replacement survival. UHMWPE wear in total hip arthroplasty is estimated to be typically as high as 200 micrometers per year. During Phase I, the effects of a zirconia coating on Co-Cr devices to reduce wear to the mating UHMWPE part were investigated. Mechanical wear tests (one million reciprocating cycles) showed that UHMWPE disks articulated against the zirconia coated Co-Cr canine femur heads wore 70% less than UHMWPE articulated against non-coated Co-Cr. Analysis showed that zirconia coated Co-Cr is significantly more lubricious and harder than the untreated metal. Phase II will continue to refine zirconia coatings on Co-Cr using a number of tests including a 10,000,000-cycle joint simulation study.
A method for improving wear resistance in UHMWPE is urgently needed; manufacturers and orthopaedic surgeons are keenly interested in minimizing UHMWPE wear. Major orthopaedic manufacturers with whom we have a close working relationship have expressed interest in commercializing the process once joint simulator test results become available. The market for zirconia coating of Co-Cr components is therefore significant.
