No Difference in Conventional Polyethylene Wear Between Yttria-stabilized Zirconia and Cobalt-chromium-molybdenum Femoral Heads at 10 Years.

ABSTRACT

BACKGROUND: Concerns have arisen regarding deterioration of wear properties of yttria-stabilized zirconia (YSZ) femoral head on conventional polyethylene (PE) bearings due to YSZ phase transformation. QUESTIONS/PURPOSES: The purpose of this study was to determine if there is a difference in long-term PE wear properties between YSZ and cobalt-chromium-molybdenum (Co-Cr-Mo) femoral heads. METHODS: Ten-year radiographic wear assessment was performed on a cohort of patients enrolled in a prospective randomized clinical trial comparing total hip arthroplasty with YSZ or Co-Cr-Mo femoral heads on conventional, non-cross-linked PE. RESULTS: PE linear wear, annualized wear, and steady-state wear rates remained low and similar between groups. No cases of osteolysis were observed. CONCLUSIONS: Measured conventional PE wear was similar between YSZ and Co-Cr-Mo femoral heads with the steady-state wear rates for both remaining below the generally accepted threshold at which osteolysis typically occurs. Whether clinically relevant phase transformation with YSZ femoral heads occurs is uncertain; however, the use of YSZ femoral heads in this study was not associated with increased PE wear, osteolysis, or deterioration of wear properties.