Concerns over the toxicity of cobalt-chrome ‘metal on metal’ artificial hips have led to more than 50,000 British patients being told to have blood tests and X rays.
Artificial hips have, of course, given extra mobility to thousands of patients, as well as providing freedom from pain. However, different combinations of materials can be used to manufacture the prosthesis. Metal-on-metal implants were introduced in the 1990s, as they seemed to offer better mobility, especially for younger patients, who were likely to put more pressure on the joint.
It has transpired that the performance of this class of prosthesis is unpredictable and after working well they may suffer a ‘catastrophic breakdown’ with release of debris from the bearing surface that can enter the bloodstream or surrounding soft-tissue. The Cobalt-Chrome, articulating against itself, could then lead to toxic levels of metal causing tissue necrosis and putting patients at risk.
These implants are now being phased out after NHS guidelines introduced in 2013 said that hip replacements with failure rates greater than five per cent should not be used. Women are thought to be particularly at risk because of the size of components used.
Revision surgery may be required in some cases and testing is underway to look at the extent of the problem. This means regular assessment of a large number of blood samples with a real need for precision and reliability. Many of the blood samples obtained from patients will be digested in a Discover SP-D automated microwave digestion system from CEM, prior to analysis. This is the world's only fully automated sequential microwave acid digestion system producing a clear aqueous digest suitable for elemental analysis by ICP, ICP-MS, or AA.
Plus, as each vessel can have its own method, samples can be ‘mixed and matched’ within the automation rack, giving great flexibility. The combination of acid and microwave irradiation focusing on a small cavity has reduced digestion time to just 10 minutes. ‘Snap-on’ vessel caps and attendance-free operation also makes the Discover SP-D very easy to use and suitable for rush analysis.
Also, thanks to the 4 ml option offered by CEM’s Discover SP-D, investigators checking samples from patients with suspected metal-on-metal hip failure need only micro gram sample sizes.
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