Study Finds Pseudotumors in More than One Quarter of Metal-on-Metal Hip RecipientsSep 16, 2013
A new research study from the Netherlands reports that after hip replacement with a metal-on-metal device, pseudotumor formation occurred in 28 percent of hips.
From 2005 through 2010, 129 patients (149 hips) underwent hip replacement surgery at Martinit Hospital in Groningen, The Netherlands, receiving a Birmingham Hip Resurfacing [BHR] implant, from Smith & Nephew of the United Kingdom. With four patients lost to follow-up, the final cohort in the study was129 patients (143 hips), Healio.com reports.
Researchers collected data on patient and surgical characteristics, clinical hip outcome scores, metal ion levels in the blood, and radiographs. Patients underwent computer tomographic (CT) scans. Three patients underwent revision (surgery to remove and replace the device) before the study was done and 11 patients underwent revision after the study started. The study was published September 4 in The Journal of Bone & Joint Surgery.
Researchers found a pseudotumor—an enlargement that resembles a tumor, resulting from inflammation, fluid accumulation, or other causes—in 39 patients through CT scan, according to Healio. Seven patients underwent revision because of a symptomatic pseudotumor, and 10 patients with a pseudotumor presented with complaints involving groin pain and discomfort, a noticeable mass, or paresthesia (a tingling or burning sensation). Study results showed symptomatic pseudotumors were significantly larger than asymptomatic pseudotumors. A predictor of pseudotumor formation included a blood cobalt level of less than 85 nmol/L.
“In our opinion,” the researchers wrote, ‘patients with a symptomatic pseudotumor should have a revision,” according to Healio. The researchers recommend CT scan as the best technique for diagnosing pseudotumors, along with monitoring of cobalt and chromium ion levels.
Metal-on-metal hip implants have come under scrutiny because of reports of high failure rates and the release of metallic debris into surrounding tissue and the bloodstream. Metal-on-metal hip devices from manufacturers including Biomet, Inc., Johnson & Johnson’s DePuy unit, Smith & Nephew, Stryker Corporation, and Zimmer Holdings Inc., have been recalled worldwide and patients whose hips failed have filed numerous lawsuits. The U.S. Food and Drug Administration (FDA) issued new guidelines for monitoring patients with all-metal hip devices and the agency is considering changes to the process for approving such devices.