MRI EVALUATION OF PAINFUL HIP AFTER METAL-ON-METAL TOTAL HIP ARTHROPLASTY

Abstract

Aim: To determine the MRI findings in patients with persistent painful metal on metal (MOM) hip arthroplasty and compare the results with a control group of patients with MOM or metal on polyethylene THA without symptoms.

Methods: 20 patients with normal inflammatory markers and normal plain radiographic imaging that had undergone primary THA were enrolled to this study. Patients were chosen to be included in 4 groups;

1. Patients having metal-on-polyethylene THA or resurfacing without pain (Control group),

2. Patients having MOM THA or resurfacing with high levels of metal ions (cobalt and chromium) and having pain

3. Patients having MOM THA or resurfacing with high levels of metal ions but having no pain and

4. Patients having MOM THA or resurfacing with low levels of metal ions and having no pain.

Operated hips were evaluated with MRI by one musculoskeletal radiologist who was blinded to the radiographic findings and clinical symptoms. All images were assessed for the presence of a juxtaarticular or periprosthetic abnormalities, including fluid collections, soft tissue masses, osseous abnormalities, and patterns of contrast enhancement of lesions.

Results: 5 patients were included in each group. All patients had undergone their THA at least 1 year prior to the MRI examination (mean 18 months). MRI findings including muscle atrophies, joint effusions, stress fractures, bone marrow oedema and muscle avulsions were equally distributed in all groups.

Conclusions: MOM THA or high metal ion levels had no specific MRI findings to explain the hip pain in these groups of patients.