Researchers have found in 28 percent of patients implanted with hip devices constructed with metal-on-metal bearings developed pseudotumors.
The researchers studied 129 patients who had been implanted at Martinit Hospital, Groningen, The Netherlands, with a total of 149 hips from 2005 through 2010; patients underwent metal-on-metal hip resurfacing arthroplasty with a metal-on-metal femoral head and an acetabular shell, according to Helio.com. Patients were implanted with the Birmingham Hip Resurfacing (BHR) system manufactured by Smith & Nephew, Birmingham, United Kingdom.
Three patients underwent revision surgery prior to completion of the study and another 11 patients underwent revision surgery after the study began; four patients were lost to follow-up, which led to a total cohort of 129 patients and 143 hips, according to Helio.com. Research data was conducted on each patient as were T4Etomographic scans and tissue samples, which were histologically examined in patients who underwent revision surgery. The average patient follow-up was 41 months; CT testing revealed pseudotumors in 39 patients, according to Helio.com.
Seven patients underwent revision because of a symptomatic pseudotumor, and 10 patients with a pseudotumor presented with complaints involving groin pain and discomfort, an obvious mass, and paresthesia (tingling, burning). The study found that symptomatic pseudotumors were significantly larger than asymptomatic pseudotumors, according to Helio.com. Also, a pseudotumor formation predictor involved a serum cobalt level of less than 85 nmol/L. At five years, implant survival rate was 87.5 percent.
The study reviewed the BHR system manufactured by Smith & Nephew, Birmingham, United Kingdom. “In our opinion, patients with a symptomatic pseudotumor should have a revision, and patients with a BHR with complaints need to be screened for a pseudotumor. Serum cobalt and chromium ion levels may be used for screening, but we find CT to be the best technique for diagnosing pseudotumors,” the researchers wrote. “Further follow-up of our patients with asymptomatic pseudotumors will provide more information on whether these pseudotumors progress over time and become symptomatic,” the study authors added, according to Helio.com
We recently wrote that the metal-on-metal devices can cause synovitis—inflammation of the joint lining—and this significant adverse side effect can appear long before patients experience symptoms, according to another study that found that MRI can be used to identify synovitis, said researchers at the Hospital for Special Surgery. The finding is important because it shows that MRI can be used to identify metal-on-metal hip implants that will likely fail before patients suffer symptoms typical with a failed device. In fact, say the researchers, MRIs are a helpful tool in identifying patients who need revision surgery before their bodily tissue suffers additional damage that makes revision surgery much more difficult and complex, according to Health Canal.
Metal-on-metal hip implants have long raised safety concerns in response to reports that the devices lead to early failure and other complications by releasing metal ions into the patient’s bloodstream and surrounding tissue. We’ve repeatedly written that research has linked metal-on-metal hip implant devices to a number of adverse events such as tissue necrosis, pain at the implant site that sometimes spreads to the groin and back, inflammation, swelling, metal poisoning, high failure rates, osteolysis (bone loss), and fluid collection/solid masses around the hip joint. The issue appears to be with the metal used in the construction of the implants, which was touted to last for at least two decades.
