MANCHESTER — Surgeons can use MRI and ultrasound equipment to detect metallosis in potential metal-on-metal total hip replacement revision patients, but researchers from the United Kingdom have recommended taking patient symptoms into consideration as well, according to a recent presentation.
“Although ultrasound and MRI are useful in the treating of metal-on-metal patients, there is a significant percentage of hips that have pain with negative radiology findings,” Naveed Ahmed, MBBS, MSc, of Prince Charles Hospital in Merthyr Tydfil, United Kingdom, stated in his presentation at the British Orthopaedic Association Congress, here.
Ahmed and colleagues retrospectively examined imaging results from 25 hips (16 patients) between March 2011 and May 2012: 23 hips had ultrasound scans and 21 of these hips also had MRI scans preoperatively. The patients’ average age range was 37 years to 69 years. Ultrasound was done an average of 50 months after primary total hip replacement. The MRI and ultrasounds were reported by musculoskeletal radiologists. All patients had blood tests for cobalt and chromium levels, Ahmed said.
“During surgery, multiple samples were taken from the acetabulum, capsule, as well as tissue lining the femoral neck and sent for histopathology,” he said.
The researchers analyzed fluid collected from patients during revision surgery for evidence of metallosis. MRIs were positive for fluid collection in 16 patients, while ultrasound was positive in 18 patients.
Four patients had both negative MRI and ultrasound results, but were still revised due to pain and were found to have “histopathology positive metallosis,” according to Ahmed. The histopathologist involved in the study defined metallosis as the “presence of sheets of macrophages with dark brown pigmentation in the cytoplasm under polarized light,” Ahmed said. One patient had a positive ultrasound and negative MRI result; similarly, one patient had a positive MRI with a normal ultrasound, he said.
“MRI and ultrasound are useful in screening of hips with metal-on-metal arthroplasty,” Ahmed told Orthopaedics Today Europe. “Still there are a significant percentage of hips which have failed with negative radiology findings.”
– by Jeff Craven
Ahmed N. Paper #20. Presented at: British Orthopaedic Association Congress; Sept 11-14, 2012; Manchester.
For more information:
Naveed Ahmed, MBBS, MSc, can be reached at Gurnos Rd., Merthyr Tydfil CF47 9DT, United Kingdom; email: email@example.com
Disclosure: Ahmed has no relevant financial disclosures.