title: Repeated magnetic resonance imaging in 154 hips with large-diameter metal-on-metal hip replacement.
abstract: OBJECTIVE
  The US Food and Drug Administration and the UK Medicines and Health Regulation Agency recommend using MRI in the evaluation of patients with large-diameter metal-on-metal (LD-MoM) hips. Such recommendations do not take into account the relevance of repeated cross-sectional imaging. We therefore investigated the natural course of pseudotumors in patients with LD-MoM hip replacements.
  
  
  METHODS
  Of 888 ASR patients (1,036 hips) 674 patients (798 hips) underwent 2 follow-up visits at our institution. Of these, we identified 124 patients (154 hips) who had undergone repeated clinical assessment including MRI and whole-blood metal ion assessment.
  
  
  RESULTS
  A change in classification in imaging findings between the 2 MRIs was seen in 17 of the 154 hips (11%). In 13 hips (8%), a significant progression of the pseudotumor was evident, while in 4 (3 %) there was a retrogressive change. 10 of these 13 hips had had a normal first MRI. Patients with a progressive change in the scans did not differ significantly from those without a change in MRI classification regarding follow-up time, time interval between MRIs, or changes in whole-blood Cr and Co levels between assessments.
  
  
  CONCLUSIONS
  A change in classification was rare, considering that all patients had a clinical indication for repeated imaging. Progression of the findings did not appear to correlate clearly with symptoms or whole-blood metal values.
authors.affiliation: Coxa Hospital for Joint Replacement , Tampere , Finland.
authors.forename: Aleksi
authors.initials: A
authors.lastname: Reito
authors.forename: Petra
authors.initials: P
authors.lastname: Elo
authors.forename: Timo
authors.initials: T
authors.lastname: Puolakka
authors.forename: Jorma
authors.initials: J
authors.lastname: Pajamäki
authors.forename: Jyrki
authors.initials: J
authors.lastname: Nieminen
authors.forename: Antti
authors.initials: A
authors.lastname: Eskelinen
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000295:instrumentation*; D002858:Chromium Alloys; D003560:Cysts / Q000209:etiology / Q000473:pathology; D005122:Exudates and Transudates; D005260:Female; D005500:Follow-Up Studies; D006104:Granuloma, Plasma Cell / Q000209:etiology / Q000473:pathology*; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D061825:Metal-on-Metal Joint Prostheses / Q000009:adverse effects*; D008875:Middle Aged; D011183:Postoperative Complications / Q000209:etiology / Q000473:pathology; D011474:Prosthesis Design
chemical_list: D002858:Chromium Alloys