Two recent U.K. studies have found that elevated blood metal ion levels are an indicator of metal hip implant failure. However, the two studies disagree as to whether metal ion testing is appropriate as a screening test in asymptomatic patients. Blood and serum cobalt (Co) and chromium (Cr) concentrations are considered reliable indicators of wear rates following metal-on-metal (MOM) hip arthroplasty. But the exact relationship between metal ion testing results and outcomes is still debated. According to a study published March 12 in BMJ Open, blood metal ion tests can be used as a clinical indicator of increased risk of joint failure in asymptomatic patients. The researchers followed 278 patients with “no pain” or “slight/occasional” pain for a mean of 70 months. The researchers found that elevated blood Co levels were associated with an increased likelihood of early joint failure and Co concentrations greater than 20 μg/l were frequently associated with adverse local tissue response. Male patients with low Co concentrations had a very low incidence of adverse tissue reactions. “Ion concentrations, if low, can be reassuring to both patients and surgeons and can also allow rationalization of resources,” write the authors, led by David Langton, MRCS, who reports that […]
Two recent U.K. studies have found that elevated blood metal ion levels are an indicator of metal hip implant failure. However, the two studies disagree as to whether metal ion testing is appropriate as a screening test in asymptomatic patients. Blood and serum cobalt (Co) and chromium (Cr) concentrations are considered reliable indicators of wear rates following metal-on-metal (MOM) hip arthroplasty. But the exact relationship between metal ion testing results and outcomes is still debated.
According to a study published March 12 in BMJ Open, blood metal ion tests can be used as a clinical indicator of increased risk of joint failure in asymptomatic patients. The researchers followed 278 patients with “no pain” or “slight/occasional” pain for a mean of 70 months. The researchers found that elevated blood Co levels were associated with an increased likelihood of early joint failure and Co concentrations greater than 20 μg/l were frequently associated with adverse local tissue response. Male patients with low Co concentrations had a very low incidence of adverse tissue reactions.
“Ion concentrations, if low, can be reassuring to both patients and surgeons and can also allow rationalization of resources,” write the authors, led by David Langton, MRCS, who reports that 40 patients with blood Co greater than 20 μg/l have undergone revisions with macroscopic metal staining of the local tissues detected in all patients and bone loss in 35. “In light of these findings, at our unit patients with grossly elevated metal ion concentrations are now offered revision surgery in the absence of symptoms.”
Another group of researchers led by Shiraz Sabah, M.D., similarly found that blood metal ions from 907 patients were significantly elevated in failed hips. However, Sabah’s group concluded that “blood metal ions had poor sensitivities and negative predictive values making them an inadequate screening test” and “discourage surgeons from performing revision surgery based on raised blood metal ions alone” in a presentation at the 2013 American Academy of Orthopaedic Surgeons Annual Meeting (March 19-23; Chicago).
