The cause of metal-on-metal hip implant related pain caused by cobalt, can be from both toxicity to or hypersensitivity. A study reported at the 2013 annual meeting of the American Academy of Orthopedic Surgeons evaluated patients with metal-on-metal hip replacements who returned to the hospital for revision surgery because of pain. They compared 50 patients who had unexplained pain with 48 patients who had loosening of the hip joint, malallignment, infection, or fracture.
They discovered that 60% of the group with unexplained pain had a condition called ALVAL, or asceptic lymphocytic vasculities-associated lesions, which is a sign of adverse tissue reactions caused by metal debris in the hip. ALVAL was not related to excessive joint wear. Ten times as many patients with pain alone had high ALVAL scores than those with the usual caused for pain. Twelve percent of patients get metal deposits in their soft tissues.
Surgical replacement sooner than later would help prevent advanced tissue damage as well as systemic illness that can result in widespread vasculitis as well as the effects of toxicity to cobalt that can result in cardiomyopathy, neuropathy, hypothyroidism, and hypercoagulation. If you are interested in reading about Dr. Len's experience with both these conditions in 2011 click here.