title: Magnetic resonance imaging findings in symptomatic versus asymptomatic subjects following metal-on-metal hip resurfacing arthroplasty.
abstract: BACKGROUND
  Although pseudotumors have been reported at the sites of well-functioning and painful metal-on-metal hip prostheses, there are no objective data on the magnitude of the adverse reaction. This observational study was performed to investigate the ability of modified magnetic resonance imaging (MRI) to detect and quantify adverse synovial responses in symptomatic and asymptomatic subjects following metal-on-metal hip resurfacing. We hypothesized that the magnitude of the synovial reactions would be greater in symptomatic patients.
  
  
  METHODS
  Sixty-nine patients (seventy-four hips) with hip resurfacing were divided into three groups: asymptomatic (twenty-two hips), symptomatic with a mechanical cause (twenty), and unexplained pain (thirty-two). The volume of synovitis was calculated on MRI for all patients.
  
  
  RESULTS
  Synovitis was detected in fifteen asymptomatic hips (68%), fifteen (75%) with symptoms with a mechanical causes, and twenty-five (78%) with unexplained pain. The mean volume (and standard deviation) of the synovitis in these groups was 5 ± 7 cm³, 10 ± 16 cm³, and 31 ± 47 cm³, respectively. The coefficient of repeatability between the examiners was 1.8 cm³ for measurement of synovitis. Of the thirteen subjects with revision arthroplasty, six had an adverse local tissue reaction. This subgroup had the highest volumes of synovitis on MRI.
  
  
  CONCLUSIONS
  An adverse synovial reaction was detected on MRI in both symptomatic and asymptomatic subjects. We found a larger volume of synovitis in symptomatic patients; this increase reached significance only in the group with an adverse local tissue reaction. Synovial volume on MRI may be a valuable marker in the longitudinal assessment of asymptomatic patients with a metal-on-metal hip resurfacing and in identifying patients with adverse local tissue reaction.
authors.affiliation: Adult Reconstruction and Joint Replacement Division, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA.
authors.forename: Danyal H
authors.initials: DH
authors.lastname: Nawabi
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Hayter
authors.forename: Edwin P
authors.initials: EP
authors.lastname: Su
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Koff
authors.forename: Giorgio
authors.initials: G
authors.lastname: Perino
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Gold
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Koch
authors.forename: Hollis G
authors.initials: HG
authors.lastname: Potter
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D058070:Asymptomatic Diseases; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D005549:Foreign-Body Reaction / Q000175:diagnosis* / Q000209:etiology; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D061825:Metal-on-Metal Joint Prostheses / Q000009:adverse effects*; D008875:Middle Aged; D010014:Osteolysis / Q000175:diagnosis / Q000209:etiology; D011183:Postoperative Complications / Q000175:diagnosis* / Q000209:etiology; D011475:Prosthesis Failure / Q000009:adverse effects; D012086:Reoperation; D015203:Reproducibility of Results; D013585:Synovitis / Q000175:diagnosis* / Q000209:etiology