Metal Ion Concentrations in Body Fluids after Implantation of Hip Replacements with Metal-on-Metal Bearing – Systematic Review of Clinical and Epidemiological Studies

Abstract

IntroductionThe use of metal-on-metal (MoM) total hip arthroplasty (THA) increased in the last decades. A release of metal products (i.e. particles, ions, metallo-organic compounds) in these implants may cause local and/or systemic adverse reactions. Metal ion concentrations in body fluids are surrogate measures of metal exposure.ObjectiveTo systematically summarize and critically appraise published studies concerning metal ion concentrations after MoM THA.MethodsSystematic review of clinical trials (RCTs) and epidemiological studies with assessment of metal ion levels (cobalt, chromium, titanium, nickel, molybdenum) in body fluids after implantation of metalliferous hip replacements. Systematic search in PubMed and Embase in January 2012 supplemented by hand search. Standardized abstraction of pre- and postoperative metal ion concentrations stratified by type of bearing (primary explanatory factor), patient characteristics as well as study quality characteristics (secondary explanatory factors).ResultsOverall, 104 studies (11 RCTs, 93 epidemiological studies) totaling 9.957 patients with measurement of metal ions in body fluids were identified and analyzed. Consistently, median metal ion concentrations were persistently elevated after implantation of MoM-bearings in all investigated mediums (whole blood, serum, plasma, erythrocytes, urine) irrespective of patient characteristics and study characteristics. In several studies very high serum cobalt concentrations above 50 µg/L were measured (detection limit typically 0.3 µg/L). Highest metal ion concentrations were observed after treatment with stemmed large-head MoM-implants and hip resurfacing arthroplasty.DiscussionDue to the risk of local and systemic accumulation of metallic products after treatment with MoM-bearing, risk and benefits should be carefully balanced preoperatively. The authors support a proposed „time out“ for stemmed large-head MoM-THA and recommend a restricted indication for hip resurfacing arthroplasty. Patients with implanted MoM-bearing should receive regular and standardized monitoring of metal ion concentrations. Further research is indicated especially with regard to potential systemic reactions due to accumulation of metal products.

Do Patients With a Failed Metal-on-metal Hip Implant With a Pseudotumor Present Differences in Their Peripheral Blood Lymphocyte Subpopulations?

“…However, the reliability of metal ion levels for clinical prognostic remains questionable [17] with no clear cutoff values [19] and interlaboratory variability in measurements [21]. In addition, not all patients with high metal ion levels and high wear develop an adverse tissue reaction [4,6,10].…”

Increased risk for extended acetabular reconstruction in failed hip resurfacing as compared to failed total hip arthroplasty

“…Comparison was made against a contemporary cohort of patients undergoing THA revision in the same period of time. We demonstrated that more than half of the HR patients suffered second or third grade acetabular defects according to the Paprosky classification [18]. In about three-fourths of the revisions an impaction bone grafting with either autogenous or allogenous cancellous bone was necessary.…”

“…pseudotumors) and ultimately lead to bone destruction. As increased ion blood levels may represent an indicator for HR failure, monitoring of ion blood levels is recommended in all patients [17,18].…”

Les prothèses de hanche au cobalt sont-elles dangereuses ?

“…Ce dosage permet aussi de surveiller la performance de l'implant [29][30][31]. Par exemple, une prothèse mal positionnée ou présentant un défaut de conception s'usera anormalement entraînant une libération accrue d'élé-ments métalliques mis en évidence par le dosage du cobalt dans le sang circulant.…”