CHICAGO — The results of a prospective, award-winning study suggest that ultrasound can successfully screen asymptomatic patients with large head metal-on-metal total hips for progressive pseudotumors.
The team, lead by Donald S. Garbuz, MD, MGHSc, FRCSC, of Vancouver, British Columbia, presented the findings at the Hip Society Specialty Day Meeting, here. They won the Hip Society’s John Charnley Award for their investigation.
Garbuz and colleagues studied 40 patients who had both ultrasounds and metal artifact reduction sequence (MARS) MRI read by one experienced musculoskeletal radiology. The study group included 28 men and 12 women with a mean age of 54 years who did not have any prior ultrasound or MRI during follow-up of their arthroplasty procedures and had WOMAC scores greater than 75 points.
“Both tests, ultrasound and metal-reduction MRI, performed well for the detection of pseudotumors. However for screening or initial diagnosis, I would say to you that ultrasound in an experienced ultrasonographer’s hand would be the preferred method due to its 100% sensitivity and lower cost,” Garbuz said.
The study showed no false negatives with ultrasound and slightly less sensitivity than with the MRI method used. MRI produced one false negative in the study, but it had 100% specificity, he noted.
“If you get an ultrasound properly done and it is normal, it means you do not have a pseudotumor,” Garbuz said.
There was 92.5% agreement between ultrasound and MRI findings; they did not agree in three cases, according to Garbuz.
“We had no gold standard available for diagnosis,” and that was a study weakness, he said.
Concerning the cost-analysis the researchers did, if every patient with large-head metal-on-metal (MoM) arthroplasty undergoes ultrasound and subsequent MARS MRI, the cost savings is $250,000 to $750,000 per 100,000 patients screened, Garbuz said.
“If you think about the number of patients who have these implants in, that is quite a cost savings to the system,” Garbuz said, noting that patients in this study were among 360 patients with large head MoM hip arthroplasty in their database.
Garbuz DS. Diagnostic accuracy of MRI versus ultrasound for detecting pseudotumors in asymptomatic metal-on-metal THA. Presented at: Hip Society Specialty Day Meeting; March 23, 2013; Chicago.
Disclosure: Garbuz is a paid consultant for Zimmer and receives research support from DePuy and Zimmer.