Friday, March 14, 2014

Blood cobalt levels, device type may predict metal-on-metal hip failure

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Blood cobalt levels, device type may predict metal-on-metal hip failure

Langton D. BMJ Open. 2014;doi:10.1136/ bmjopen-2012-001541

 
January 31, 2014
 
Elevated concentrations of cobalt in the blood and device type may predict early failure of metal-on-metal hip replacements, according to researchers from the United Kingdom.
   
“The results suggest that elevated blood meta ion concentrations are associated with early failure of [metal-on-metal] MoM devices secondary to adverse reactions to metal debris,” David J. Langton, MRCS, abd colleagues wrote in a recently published study.
 
Researchers performed a retrospective analysis of 299 resurfacings in 278 patients who had Articular Surface Replacement ([ASR] DePuy, Leeds, UK) and Birmingham Hip Resurfacing ([BHR] Smith & Nephew, Warwick, UK). The patients reported complications possibly related to metal wear debris and had “slight/occasional pain.” Harris Hip Scores were 95 or greater at the time of venesection. The researchers instituted a blood metal ion screening protocol, ultrasound scanning and joint aspiration to determine the blood cobalt concentration.

 Follow up was annual unless symptoms dictated otherwise. Mean postoperative follow-up was 70 months and the mean follow-up post-venesection was 36 months.
 
Langton and colleagues found blood cobalt concentration and device to be significant risk factors for failure of the hip joint. They found females with high cobalt blood concentration and an ASR device had the highest failure risk. Patients with the BHR device had an 89% reduced risk of revision.
“Cobalt concentrations greater than 20 μg/L are frequently associated with metal staining of tissues and the development of osteolysis,” researchers wrote. “Development of soft tissue damage appears to be more complex with females and patients with ASR devices seemingly more at risk when exposed to equivalent doses of metal debris.” – by Christian Ingram
 
Disclosure: Langton is an unpaid consultant for Wright Medical and has been reimbursed for individual talks for DePuy and Finsbury. Multiple coauthors are expert witnesses in ongoing litigation regarding MoM hip joints and/or have received reimbursement for travel to educational meetings by Smith & Nephew, Zimmer, DePuy and Wright Medical. One coauthor has received reimbursement for DePuy educational sessions.

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