Metal-on-Metal Hip Implant Patients Vulnerable to Formation of PseudotumorsJun 5, 2012 | Parker Waichman LLP
A new study published in the Journal of Bone and Joint Surgery reports that the use of large diameter metal-on-metal hip implant devices in total hip replacement surgery may significantly increase the risk that patients will develop a pseudotumor. A pseudotumor is reaction that occurs as a result of metal debris being shed from a metal-on-metal hip replacement device into the tissue surrounding the implant.
The prospective cohort study, conducted by researchers at Isala Klinieken hospital in The Netherlands, looked at a total of 119 patients who underwent 120 metal-on-metal total hip replacements with large-diameter femoral heads between January 2005 and November 2007. A total of 42 patients, or 39%, eventually developed pseudotumors. According to the study authors, patients who exhibited elevated serum metal ion levels had a four times increased risk of developing a pseudotumor.
Because of the high incidence of pseudotumors seen among patients with large-diameter metal-on-metal total hip implant devices, the authors of the study recommended that patients fitted with such devices should be closely monitored.
Metal-on-metal hip implants first began raising safety concerns after the August 2010 recall of DePuy Orthopaedics' ASR hip implant devices. A growing number of reports worldwide have since linked metal-on-metal hip replacements with loosening, and significant soft tissue reactions thought to be the result of increased levels cobalt and chromium ions shed by metal-on-metal hip implants.
In May of last year, the U.S. Food & Drug Administration (FDA) asked 21 makers of metal-on-metal hip implants to conduct safety studies of their devices. In June, the agency will convene a panel of outside advisers to discuss the problems related to metal-on-metal hip replacements.
In February, regulators in the U.K. advised that patients fitted with large metal hip implants for total hip replacement – those with bearings of 36 mm or above – should undergo annual blood tests to check cobalt and chromium, as well as MRIs for any patient who does exhibit high metal ion levels. Similar warnings have also been issued in Canada.