Abstract
The present research evaluated the course of cobalt and chromium in the blood and urine after the revision of metal-on-metal with a ceramic-on-polyethylene total hip arthroplasty. Seven patients were enrolled for hip prosthesis revision owing to ascertained damage of the implant. Metals in the blood and urine were evaluated before and after the hip revision. The double measurement before the total hip revision revealed high levels of metal ions (on average, 88.1 µg/L of cobalt in the blood, 399.0 µg/g of creatinine cobalt in the urine, 46.8 µg/L of chromium in the blood, and 129.6 µg/g of creatinine chromium in the urine at the first measurements), with an increasing trend between the first and second dosage. Within a week after the hip revision, the levels of metal ions significantly decreased by approximately half. Four to six months after the operation, the cobalt levels were found near to the reference values, whereas the chromium levels reached 25% of the values measured before the revision. The revision of malfunctioning metal-on-metal implants produced a dramatic decrease of metal ions in biological fluids, although it did not completely rescue the chromium level.
Highlights
A consequence of metal ion debris accumulation in periprosthetic tissues caused by malfunctioning metal-on-metal (MoM) total hip prostheses (THPs) is so-called metallosis [1]
From a population of 72 patients with MoM THPs with a large diameter femoral head ASRTM DePuy (Raynham, MA, USA) and 1 patient with hip resurfacing subjected to a device alert recall program, as previously studied [2], 19 (26%) were judged eligible for an MoM prosthesis revision according to the malfunctions of their hips based on the pain score (Harris Hip Score), X-ray evaluation, inclination angle of the cup, and high metal ion levels in biological fluids
Six out of the seven patients who submitted to a revision of an MoM THP according to the criteria explained above had an inclination angle of the MoM prosthesis greater than 50◦ (57 ± 6◦); 45◦ was the inclination angle of the seventh patient
Summary
A consequence of metal ion debris accumulation in periprosthetic tissues caused by malfunctioning metal-on-metal (MoM) total hip prostheses (THPs) is so-called metallosis [1]. Metal-on-polyethylene bearings cause a significant increase in metal ions [5]. The increase in metal ions is generated by corrosive action in the synovial fluid of accumulated metal debris [6], inducing macrophage activation, osteolysis, and implant malfunctioning. The toxic effects as a consequence of metal ion release are almost exclusively caused by Co (so-called arthroprosthetic cobaltism). Systemic adverse effects typically occur with blood Co concentrations higher than 300 μg/L, with polycythemia and hypothyroidism being the first signs of toxicity [11]
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