The elevation of metal levels in serum and urine during post-operative follow-up is a frequent find following the implantation of certain models of metal-on-metal hip prostheses. Among 45 patients with the same resurfacing prostheses, chromium (Cr) and cobalt (Co) levels in serum and urine were determined at 3, 4, 5, and 6 years after surgery. In the same period, levels of Cr, Co and molibdene (Mo) in scalp hair were also measured. Mean Cr and Co levels in serum were 8.29 mg/L (SD 17.97) and 8.38 mg/L (SD 21.97), respectively, whereas in urine levels were 16.20 mg/L (SD SD 32.55) and 75.40 mg/L (SD 190.86), respectively. In hair, mean Cr level were 163.27 mg/g (SD 300.62), mean Co level 61.98 mg/g (SD 126.48), and Mo 31.36 mg/g (SD 37.86). A high concordance was observed between chromium-urine and chromium-serum and between cobalt-urine and cobalt-hair. A moderate concordance was present between cobalt-urine and cobalt-serum, and between cobalt-hair and cobalt-serum. Eleven patients required revision surgery, five of them due to metallosis and periarticular cyst. At 1 year after reintervention, analytics were performed again and the following decrease rates were found: 42.8% in Cr levels, 51.1% in Mo levels, and 90.3% in Co levels. Keywords: hip; resurfacing arthroplasty; metal levels; metallosis; hairThe biggest long-term complication of hip arthroplasties is component wear, followed by the manifestation of acetabular and femoral osteolysis and the eventual failure due to component loosening. The search for solutions to this issue, more worrisome in young patients, has lead to the introduction of new ceramic materials and metal alloys. Recently, it has been found that some metal-on-metal (m-o-m) friction arthroplasties may produce a variety of clinical alterations derived from the presence of metal ions, especially chromium and cobalt, in blood and urine. 1 Although no fetal nor carcinogenic complications have been described, 2 increased levels of these metals may lead to renal and hepatic alterations, as well as local lesions known as ALVALs (aseptic lymphocyte-dominant vasculitis-associated lesions). [3][4][5] On the other hand, increased levels of molybdenum may exert negative effects on fertility. This becomes particularly important when we take into account that the population group most likely to carry this type of hip prosthesis comprises young patients, and therefore, reproductive implications must be considered. 6 Different follow-up protocols have been published which include guidelines about the normal values of ions in blood and urine, maximum tolerable levels, 7 and the convenience of monitoring. 8,9 These analytical assessments require special care when taking and moving samples, and they are not routinely performed in the laboratories of general hospitals. Furthermore, such samples may become altered sometimes due to the ingestion of food products, the effects of drugs, or environmental factors. 10,11 Hair features a remarkable potential as biomarker, since it reflects the historical ex...
