Patients with cobalt-related thyroid problems often exhibit symptoms similar to those of hypothyroidism, such as difficulty concentrating, feeling physically weak and lethargic, and poor reflexes. Again, patients with malfunctioning artificial hip devices found to have thyroid issues tested with extremely high cobalt levels, and in at least one case, thyroid function markedly improved after the patient underwent hip revision surgery that halted metal ion buildup.
Cobalt toxicity can lead to depleted levels of crucial neurotransmitters such as dopamine and serotonin, as well an increase in free radicals that can cause damage to neurologically sensitive areas that are vulnerable to oxidative stress , such as the sheath protecting the nerve fibers of the brain and spinal cord.
Some common adverse neurological effects of excess cobalt in the bloodstream are short-term memory loss, fatigue, headaches, blurred vision,and increasing loss of hearing. Cases of patients with hip device-related cobalt toxicity also reported tinnitus and unexplained paraesthesia (“pins and needles” sensation), and most tested with moderately high cobalt levels (between 20 and 100 μg/L).
Though all of these patients saw their symptoms improve after hip revision surgery, the degree of improvement varied. Furthermore, researchers haven’t firmly established whether or not neurological damage from cobalt toxicity is completely reversible after cobalt levels return to normal, and so,we may later discover that patients can develop lifelong problems.
Though hepatotoxicity from excess cobalt is thought to be rare because the liver has a high toxicity threshold for cobalt uptake, it can prove fatal. At least one recorded patient, who exhibited a shockingly-high serum cobalt level of 6521μg/L after implantation with a cobalt-chromium hip device, was diagnosed with hepatotoxicity and eventually died from multiple organ failure.
Are Modern Hip Device Designs To Blame?
Many researchers, including Philip Pastides and his colleagues in the UK, believe that they are.
In an extensive editorial on recent metal-on-metal hip implant research in the World Journal of Orthopedics, Pastides explains that even though the total metal debris contributed from the stem-trunnion interface is less than the amount that comes off from the main articulating surfaces (that is, the ball and the cup rubbing against each other during normal movement) – which was one of the major design aims of modern hip devices – this particular type of debris may actually be more biologically active and therefore potentially more harmful.
A “Modern Orthopedic Failure”
This means that the particles released from stem-trunnion friction may cause more adverse tissue reactions, including osteolysis, and can contribute more to disastrous loosening. Though Pastides and his team reviewed mainly literature on metal-on-metal hips, they believe similar issues are at play in non-MoM hip implants as well. Particularly convincing were measurement comparisons between various ion levels from patients suffering complications from modular THR replacements and those having similar issues from hip resurfacing (in which there is no stem-trunnion junction to speak of).
The authors denounce metal-on-metal hip implants in no uncertain terms, calling them a “modern orthopedic failure” that promise better fit but at the expense of much higher wear rates than expected. Such wear, they say, causes destruction of surrounding bone and tissue that often proves “devastating” to hip replacement patients, who are still mostly unaware of the potential risks of their hip implants.
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