Metal ions related complications after hip arthroplasty

The problems of metal ions accumulation and related complications after metal-on-metal hip arthroplasty have been concerned by joint surgeons. Furthermore, metal ions released resulting from taper fretting and corrosion at the head-neck junction of prosthesis are also research hotspot in the field of arthroplasty. Whether the complications associated with metal ions are as serious as expected, its specific manifestations, mechanisms and other issues are still controversial. There is no consensus on the clinical detection methods and standards of metal ions. The present study reviews the literatures and summarizes the above issues, in order to have a deeper understanding of these issues. As far as the form of complication is concerned, there are local and systemic reactions. The former is mainly an adverse reaction of local tissue, especially pseudotumor. However, the incidence of pseudotumor and its risk factors are controversial. There is no clear evidence of systemic complications such as carcinogenicity and teratogenicity. The molecular mechanism of cobalt-chromium toxicity involves many signal transduction pathways, and its histopathological mechanism includes macrophage-mediated nonspecific immunity and lymphocyte-mediated specific immunity. The former is mainly related to the wear dose, while the latter is related to metal sensitivity with great individual difference. The method of metal ion concentration determination is still controversial. The inductively coupled plasma mass spectrometry (ICP-MS) is widely used at present, and the determination of metal ion concentration critical value has important guiding significance for clinical practice. Britain's 7 μg/L proposal was once discussed as a standard, while there are many different views currently. In summary, it is thought that the complication of metal ion after hip arthroplasty is the result of cobalt chromium metal ion activating nonspecific immunity and specific immunity. Abnormal activation of many signaling pathways leads to local soft tissue reactions, while systemic complications do not have clear evidence. Furthermore, there is no uniform standard for the detection of metal ion concentration. This index is not recommended in clinical practice. We should have a comprehensive assessment of the patient's situation.