Reduced Wear with Oxidized Zirconium Femoral Heads

Wear-related complications have been a major cause of revisions and reoperations following total hip arthroplasty. In the past, several materials have shown promise for reducing polyethylene wear, but they have draw-backs. Elimination of polyethylene from prosthetic designs has not gained wide acceptance because it limits design flexibility and introduces other risks: fractures with ceramic-on-ceramic bearings and metal-ion release with metal-on-metal bearings1,2. In an attempt to address the problem on the femoral side, opposite the polyethylene, ceramic modular heads were introduced because their surfaces are more abrasion-resistant and produce less friction than do metal surfaces, thereby reducing abrasive and adhesive wear of the polyethylene3. The use of oxide ceramics for the articulating femoral head can reduce wear by 25% to 50%4-6. However, ceramics such as monolithic zirconia and alumina are susceptible to brittle fracture, with the need for immediate revision1. On the acetabular side, highly crosslinked ultra-high molecular weight polyethylene was used for liners more than thirty years ago7-9. This practice was ended after a brief time because of commercial considerations, but subsequent clinical results have indicated that these liners undergo substantially less wear than do conventional ultra-high molecular weight polyethylene liners. Recently, manufacturers have introduced new highly crosslinked ultra-high molecular weight polyethylene acetabular liners, which also offer the potential of reducing wear10,11. However, laboratory results have indicated that the relative advantage of such polyethylene can be reduced when it articulates against rougher surfaces12. Metallic cobalt-chromium (CoCr) femoral heads do not have the same risk of fracture as ceramic heads, but their surfaces become roughened as a result of abrasive and oxidative wear3. Evidence of this roughening can be seen on retrieved heads, and both clinical and …