Metal Artifact Reduction Sequence MRI Abnormalities Occur in Metal-on-polyethylene Hips

BACKGROUND: To determine the importance of MRI abnormalities in metal-on-metal (MoM) bearings, it is important to understand the baseline features of this diagnostic tool in conventional metal-on-polyethylene (MoP) bearings. QUESTIONS/PURPOSES: What are the frequency, size, and types of MRI-documented adverse local tissue reactions in asymptomatic patients with MoP bearings? METHODS: We recruited 50 patients 5 years after a MoP total hip arthroplasty from a pool of patients in our joint registry who had a Harris hip score of >90. To be included, patients had to be without pain and have adequate radiographs. Our data set included 50 asymptomatic patients with MoP bearings who underwent a metal artifact reduction sequence MRI. RESULTS: MRI abnormalities were seen in 14 of 50 (28%) asymptomatic patients who were studied. Thirteen of the 14 abnormalities were cystic thin-walled lesions with a mean of 18 cm3 (range, 1-79 cm3). CONCLUSIONS: MRI abnormalities were noted in nearly one-third of asymptomatic patients with MoP bearings. Decisions concerning revision of MoM bearings should not be based on isolated MRI findings because MRI abnormalities are commonly seen regardless of bearing type. A number of factors should determine the need for intervention including pain, mechanical symptoms, abductor weakness, component type, component position, and ion levels as well as MRI findings. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.