title: MRI versus radiography of acromioclavicular joint dislocation.
abstract: OBJECTIVE
  Acromioclavicular joint injuries are usually diagnosed by clinical and radiographic assessment with the Rockwood classification, which is crucial for treatment planning. In view of the implementation of MRI for visualization of the acromioclavicular joint, the purpose of this study was to describe the MRI findings of acromioclavicular joint dislocation in comparison with the radiographic findings.
  
  
  METHODS
  Forty-four patients with suspected unilateral acromioclavicular joint dislocation after acute trauma were enrolled in this prospective study. All patients underwent digital radiography and 1-T MRI with a surface phased-array coil. MRI included coronal proton density-weighted turbo spin-echo and coronal 3D T1-weighted fast field-echo water-selective sequences. The Rockwood classification was used to assess acromioclavicular joint injuries at radiography and MRI. An adapted Rockwood classification was used for MRI evaluation of the acromioclavicular joint ligaments. The classifications of acromioclavicular joint dislocations diagnosed with radiography and MRI were compared.
  
  
  RESULTS
  Among 44 patients with Rockwood type I-IV injuries on radiographs, classification on radiographs and MR images was concordant in 23 (52.2%) patients. At MRI, the injury was reclassified to a less severe type in 16 (36.4%) patients and to a more severe type in five (11.4%) patients. Compared with the findings according to the original Rockwood system, with the adapted system that included MRI findings, additional ligamentous lesions were found in 11 (25%) patients.
  
  
  CONCLUSIONS
  In a considerable number of patients, the MRI findings change the Rockwood type determined with radiography. In addition to clinical assessment and radiography, MRI may yield important findings on ligaments that may influence management.
authors.affiliation: Department of Radiology, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria. stefan.nemec@meduniwien.ac.at
authors.forename: Ursula
authors.initials: U
authors.lastname: Nemec
authors.forename: Gerhard
authors.initials: G
authors.lastname: Oberleitner
authors.forename: Stefan F
authors.initials: SF
authors.lastname: Nemec
authors.forename: Michael
authors.initials: M
authors.lastname: Gruber
authors.forename: Michael
authors.initials: M
authors.lastname: Weber
authors.forename: Christian
authors.initials: C
authors.lastname: Czerny
authors.forename: Christian R
authors.initials: CR
authors.lastname: Krestan
mesh_terms: D000173:Acromioclavicular Joint / Q000293:injuries*; D000293:Adolescent; D000328:Adult; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011859:Radiography; D012783:Shoulder Dislocation / Q000145:classification / Q000175:diagnosis* / Q000000981:diagnostic imaging