Abstract
Introduction
Two types of ceramic materials currently used in total hip replacements are third generation hot isostatic pressed (HIPed) alumina ceramic (commercially known as BIOLOX®forte, CeramTec) and fourth generation alumina matrix composite ceramic consisting of 75% alumina, 24% zirconia, and 1% mixed oxides (BIOLOX®delta, CeramTec). Delta ceramic hip components are being used worldwide, but very few studies have analyzed retrieved delta bearings. The aim of this study is to compare edge loading ‘stripe’ wear on retrieved femoral heads from delta-on-delta, delta-on-forte and forte-on-forte ceramic bearings revised within 2 years in vivo.
Material and Methods
Ceramic bearings revised at one center from 1998 to 2010 were collected (61 bearings). Eleven delta heads revised between 1–33 months were compared to 24 forte femoral heads with less than 24 months in vivo (Figure 1). The surface topography of the femoral heads was measured using a RedLux AHP (Artificial Hip Profiler, RedLux Ltd, Southampton, UK). Three representative samples were examined with a FEI Quanta 200 Scanning Electron Microscope (SEM).
Results
The median time to revision for delta femoral heads was 12 months, compared to 13 months for forte femoral heads. Sixteen out of 20 forte femoral heads and 6 out of 11 delta femoral heads had edge loading wear (Figure 2). The average volumetric wear rate for forte was 0.96 mm3/yr (median 0.13 mm3/yr), and 0.06 mm3/yr (median 0.01 mm3/yr) for delta (p=0.03). There was no significant difference (p>0.05) in age, gender, time to revision or femoral head diameter between the two groups.
Conclusions
Edge loading wear occurs in BIOLOX®delta ceramic bearings. Edge loading wear volumes and wear rates are less in these bearings compared to BIOLOX®forte bearings. These findings are consistent with hip simulator studies. Early analysis of retrieved implants is important to check the in vivo performance of biomaterials.
