Metal-on-metal hips are primarily made of cobalt and chromium. When these components rub together with normal use, the parts wear down and corrode, causing metal to leach into the surrounding tissues and bloodstream. Once in the bloodstream, the metal content can cause metal poisoning called metallosis. Side effects may include implant failure, necrosis (tissue and bone death), and organ damage. These side effects may require revision surgery to treat.
Pseudo tumors are also a side effect of the metal poisoning. The tumors are soft tissue changes in the surrounding tissues and bone of the hip prosthetic. According to a study published June 2015, a systematic review examined the blood test results from nearly 10,000 patients that had received a metal-on-metal hip implant. The results showed that the patients had metal ion concentrations “consistently higher” than previous blood tests performed immediately following the hip replacement. The levels of cobalt and chromium metal ions were particularly alarming.
Other symptoms of metal poisoning include: skin rashes, cardiomyopathy (abnormal heart muscle function which leads to difficulty pumping blood through the body), sensory changes such as hearing or vision loss, depression, cognitive impairment, mood swings, fatigue, kidney function impairment, and thyroid dysfunction which leads to weight gain, fatigue, neck discomfort and feeling cold.
Metal-on-metal hip implant manufacturers such as Wright Medical, DePuy Orthopaedics and parent company Johnson & Johnson, Stryker, Smith & Nephew and Zimmer Biomet Holdings have been under fire in recent years for their allegdly failed hip implant designs. Many patients have come forward with lawsuits seeking compensation for their pain and negative impacts that they say failed hips have brought into their life.