title: MRI findings in painful metal-on-metal hip arthroplasty.
abstract: OBJECTIVE
  The objective of our study was to compare the frequency of osseous and soft-tissue abnormalities in patients presenting with hip pain after resurfacing arthroplasty and after total hip arthroplasty (THA), correlate the MRI findings with histologic results, and determine which MRI findings are predictive of aseptic lymphocytic vasculitis-associated lesions.
  
  
  METHODS
  The MRI examinations of patients with metal-on-metal hip prostheses placed at resurfacing arthroplasty (n=31) or THA (n=29) were reviewed for osteolysis, synovitis, extracapsular disease, synovial pattern, and mode of decompression into adjacent bursae. Regional muscles and tendons were assessed for tendinosis, tear, atrophy, and edema. Histologic and operative findings were reviewed in 19 patients (20 hips) who underwent revision surgery. Chi-square tests were performed to detect differences between the resurfacing arthroplasty and THA groups. The Wilcoxon rank sum test was performed to detect differences in MRI findings in patients with and those without aseptic lymphocytic vasculitis-associated lesions.
  
  
  RESULTS
  Synovitis was detected in 77.4% of resurfacing arthroplasty hips and 86.2% of THA hips. Extracapsular disease was present in 6.5% of resurfacing arthroplasty hips and 10.3% of THA hips. Osteolysis was detected in 9.7% of resurfacing arthroplasty hips and 24.1% of THA hips. There was no difference in the incidence of synovitis (p=0.51), osteolysis (p=0.17), or extracapsular disease (p=0.67) between the resurfacing arthroplasty and THA groups. Patients with aseptic lymphocytic vasculitis-associated lesions had higher volumes of synovitis (p=0.04) than patients without aseptic lymphocytic vasculitis-associated lesions. Extracapsular disease and muscle edema were seen only in patients with aseptic lymphocytic vasculitis-associated lesions.
  
  
  CONCLUSIONS
  Synovitis is common in patients with metal-on-metal hip prostheses and occurs with a similar incidence after resurfacing arthroplasty and after THA; osteolysis and extracapsular disease are uncommon. The MRI signs most suggestive of aseptic lymphocytic vasculitis-associated lesions are high volumes of synovitis, extracapsular disease, and intramuscular edema.
authors.affiliation: Department of Radiology and Imaging, Hospital for Special Surgery, Weill Cornell Medical College of Cornell University, 535 E 70th St, New York, NY 10021, USA.
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Hayter
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Gold
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Koff
authors.forename: Giorgio
authors.initials: G
authors.lastname: Perino
authors.forename: Danyal H
authors.initials: DH
authors.lastname: Nawabi
authors.forename: Theodore T
authors.initials: TT
authors.lastname: Miller
authors.forename: Hollis G
authors.initials: HG
authors.lastname: Potter
mesh_terms: D018771:Arthralgia / Q000209:etiology*; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D005260:Female; D062785:Hemiarthroplasty / Q000009:adverse effects*; D006621:Hip Joint / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D061825:Metal-on-Metal Joint Prostheses / Q000009:adverse effects*; D008875:Middle Aged; D009135:Muscular Diseases / Q000175:diagnosis / Q000209:etiology; D009408:Nerve Compression Syndromes / Q000175:diagnosis / Q000209:etiology; D010014:Osteolysis / Q000175:diagnosis / Q000209:etiology; D012086:Reoperation; D013585:Synovitis / Q000175:diagnosis / Q000209:etiology; D014657:Vasculitis / Q000175:diagnosis / Q000209:etiology