Metal ion release: also a concern for ceramic-on-ceramic couplings?

BIOLOX delta is the newest ceramic composite material of the BIOLOX family and its use in hip devices represents a good alternative to Metal-on-Metal or Metal-on-Polyethylene coupling. Some Metal-on-Metal hip devices have shown chromium and cobalt release, which promoted toxic effects. Furthermore, the ceramic composite contains trivalent chromium, even if strongly bound to the alumina lattice. The present study is aimed at detecting any 'in vivo' release of chromium ions from BIOLOX delta bearings in the blood, erythrocytes and urine of patients. Twenty patients implanted with total hip arthroplasty (THA) with BIOLOX delta-BIOLOX delta couplings and 21 subjects with no implanted prostheses were studied. Inductively coupled plasma mass spectrometry equipped with dynamic reaction cell was used for analysis. In the THA group the Cr ions values were; in blood mean 0.21 µg/l (±0.09), in serum 0.21 µg/l (±0.12), in normalized erythrocytes 0.13 µg/l (±0.09), in normalized urine 0.12 µg/g creatinine (±0.13). In the control group the Cr ions values were; in blood mean 0.22 µg/l (st dev 0.14), in serum 0.17 µg/l (±0.08), in normalized erythrocytes 0.13 µg/l (±0.11), in normalized urine 0.07 µg/g creatinine (±0.08). The Lab reference values were 0.1-5.0 µg/l for blood, 0.1-0.5 µg/l for serum, 0.14-4.58 µg/l for normalised erythrocytes and 0.05-2.2 µg/l for urine. All samples in both groups resulted in chromium levels within the normal reference range and the safety of BIOLOX delta ceramics, in terms of chromium ions release, has been demonstrated.