title: Good sensitivity and specificity of ultrasound for detecting pseudotumors in 83 failed metal-on-metal hip replacements.
abstract: OBJECTIVE
  Ultrasound is used for imaging of pseudotumors associated with metal-on-metal (MoM) hips. Ultrasound has been compared with magnetic resonance imaging, but to date there have been no studies comparing ultrasound findings and revision findings.
  
  
  METHODS
  We evaluated the sensitivity and specificity of preoperative ultrasound for detecting pseudotumors in 82 patients with MoM hip replacement (82 hips). Ultrasound examinations were performed by 1 of 3 musculoskeletal radiologists, and pseudotumors seen by ultrasound were retrospectively classified as fluid-filled, mixed-type, or solid. Findings at revision surgery were retrieved from surgical notes and graded according to the same system as used for ultrasound findings.
  
  
  RESULTS
  Ultrasound had a sensitivity of 83% (95% CI: 63-93) and a specificity of 92% (CI: 82-96) for detecting trochanteric region pseudotumors, and a sensitivity of 79% (CI: 62-89) and a specificity of 94% (CI: 83-98) for detecting iliopsoas-region pseudotumors. Type misclassification of pseudotumors found at revision occurred in 8 of 23 hips in the trochanteric region and in 19 of 33 hips in the iliopsoas region.
  
  
  CONCLUSIONS
  Despite the discrepancy in type classification between ultrasound and revision findings, the presence of pseudotumors was predicted well with ultrasound in our cohort of failed MoM hip replacements.
authors.affiliation: Coxa Hospital for Joint Replacement , Tampere , Finland.
authors.forename: Olli
authors.initials: O
authors.lastname: Lainiala
authors.forename: Petra
authors.initials: P
authors.lastname: Elo
authors.forename: Aleksi
authors.initials: A
authors.lastname: Reito
authors.forename: Jorma
authors.initials: J
authors.lastname: Pajamäki
authors.forename: Timo
authors.initials: T
authors.lastname: Puolakka
authors.forename: Antti
authors.initials: A
authors.lastname: Eskelinen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000295:instrumentation; D015331:Cohort Studies; D005260:Female; D006104:Granuloma, Plasma Cell / Q000175:diagnosis* / Q000000981:diagnostic imaging* / Q000473:pathology; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008670:Metals / Q000009:adverse effects*; D008875:Middle Aged; D011237:Predictive Value of Tests; D012086:Reoperation; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D017211:Treatment Failure; D014463:Ultrasonography / Q000379:methods*; D006113:United Kingdom
chemical_list: D008670:Metals