title: MR imaging of the intraarticular disk of the acromioclavicular joint: a comparison with anatomical, histological and in-vivo findings.
abstract: OBJECTIVE
  To characterize MRI features of the intraarticular disk of the acromioclavicular joint.
  
  
  METHODS
  We studied the appearance of 11 acromioclavicular joints of six cadavers (subjects aged 57-89 years at the time of death) and six healthy shoulders on T1-weighted, T2 (TSE)-weighted, STIR and PD (fat saturated) magnetic resonance imaging (MRI) and compared the findings with observations during dissection and histological examination.
  
  
  RESULTS
  Macroscopic examinations showed two wedge-shaped disks underneath the superior and above the inferior joint capsule in nine specimens. In two specimens the acromioclavicular joints were degenerated. Histologically, the disk tissue consisted of fibrocartilage whereas the joint cartilage was partly degenerated, containing zones of fibrocartilage amidst degenerated hyaline cartilage, which may explain the similar signal intensity of both structures in all sequences used. MR appearance of the intraarticular structures of the acromioclavicular joint was similar in cadaveric and healthy shoulders.
  
  
  CONCLUSIONS
  The difficulties related to imaging the acromioclavicular joint may be explained by the anatomy. Similar signal intensity of cartilage and disk may be explained by their similar histological structure (fibrocartilage). MRI findings should be interpreted with respect to the variable anatomy. These results may serve as a basis for further radiological studies of the acromioclavicular joint.
authors.affiliation: Orthopädische Universitätsklinik Regensburg, Im Asklepios Klinikum Bad Abbach, Kaiser-Karl-V.-Allee 3, 93077 Bad Abbach, Germany. gheers@t-online.de
authors.forename: Guido
authors.initials: G
authors.lastname: Heers
authors.forename: Jürgen
authors.initials: J
authors.lastname: Götz
authors.forename: Thomas
authors.initials: T
authors.lastname: Schubert
authors.forename: Henrik
authors.initials: H
authors.lastname: Schachner
authors.forename: Ulrich
authors.initials: U
authors.lastname: Neumaier
authors.forename: Joachim
authors.initials: J
authors.lastname: Grifka
authors.forename: Achim
authors.initials: A
authors.lastname: Hedtmann
mesh_terms: D000173:Acromioclavicular Joint / Q000033:anatomy & histology* / Q000601:surgery; D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D002358:Cartilage, Articular / Q000033:anatomy & histology; D004210:Dissection; D005260:Female; D006652:Histological Techniques; D006801:Humans; D017746:Joint Capsule / Q000033:anatomy & histology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results