title: What is the natural history of asymptomatic pseudotumours in metal-on-metal hip resurfacing patients?
abstract: OBJECTIVE
  We assessed the natural history of asymptomatic pseudotumours associated with metal-on-metal hip resurfacings (MoMHRs), and factors associated with future revision.
  
  
  METHODS
  In 2007-2008, we identified 25 MoMHRs (21 patients; mean age 59.9 years; 76% female) with asymptomatic pseudotumours. All patients underwent identical initial assessment (ultrasound, blood metal ions, radiographs, Oxford Hip Score [OHS]) and were considered asymptomatic because they denied experiencing hip symptoms, were satisfied with their MoMHR surgery, and had good or excellent OHSs (≥34). In 2012-2013, repeat assessments were performed in all non-revised patients.
  
  
  RESULTS
  Revision for pseudotumour was performed/recommended in 15 MoMHRs (60%) at a mean 2.7 years (range 0.4-6.4 years) from initial assessment, with 14 developing symptoms before revision. Non-revised MoMHRs (n = 10) underwent repeat ultrasound at a mean 5.1 years (range 4.0-6.5 years) later, with no changes in pseudotumour volume (p = 0.956) or OHS (p = 0.065) between assessments. High blood cobalt (p = 0.0048) and chromium (p = 0.0162), large pseudotumours (p = 0.0458), low OHS (p = 0.0183), and bilateral MoMHRs (p = 0.049) predicted future revision. Patients with blood metal ions above established unilateral/bilateral thresholds and/or initial pseudotumours &gt;30 cm3 had an 86.7% sensitivity, 70.0% specificity, 81.2% positive predictive value, and 77.8% negative predictive value for future revision.
  
  
  CONCLUSIONS
  MoMHR patients with initially asymptomatic pseudotumours often become symptomatic and require revision. Patients with high blood metal ions and/or pseudotumours &gt;30 cm3 should remain under annual surveillance or be considered for revision (especially in patients also having lower initial OHSs, bilateral MoMHRs, and/or those becoming symptomatic). Less regular surveillance of patients outside these parameters appears acceptable.
authors: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Nuffield Orthopaedic Centre, Oxford - UK.
authors: Gulraj S
authors: GS
authors: Matharu
authors: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Nuffield Orthopaedic Centre, Oxford - UK.
authors: Simon J
authors: SJ
authors: Ostlere
authors: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Nuffield Orthopaedic Centre, Oxford - UK.
authors: Hemant G
authors: HG
authors: Pandit
authors: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Nuffield Orthopaedic Centre, Oxford - UK.
authors: David W
authors: DW
authors: Murray
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D015331:Cohort Studies; D005260:Female; D006104:Granuloma, Plasma Cell / Q000175:diagnosis / Q000209:etiology* / Q000628:therapy; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D007592:Joint Diseases / Q000175:diagnosis / Q000209:etiology* / Q000601:surgery; D008297:Male; D061825:Metal-on-Metal Joint Prostheses / Q000009:adverse effects*; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation