title: [Isolated lesion of the infraspinatus at the myotendinous junction: a new lesion].
abstract: OBJECTIVE
  We have identified a previously unpublished lesion of the infraspinatus muscle at the myotendinous junction. We describe its presentation and MRI appearance, notably the absence of other tendinous pathology in the rotator cuff.
  
  
  METHODS
  We retrospectively reviewed 25 patients with isolated infraspinatus lesions and associated edema identified on the fat-suppressed T2-weighted images of MRI. Imaging exams and medical records collected over a 7-year period were reviewed by a team of radiologists and surgeons specializing in the shoulder. A presentation of the mechanism of injury, radiological analysis of MRI scans and other investigations (arthro-CT and EMG studies) were carried out; all MRI included at least two fat-suppressed T2-weighted (transverse and coronal) sequences and one T1-weighted (transverse) sequence.
  
  
  RESULTS
  The lesion was characterized by tearing or delamination at the myotendinous junction, which was accompanied by edema of the infraspinatus muscle in the initial phase. Over time the edema was seen to resolve and muscle atrophy and fatty degeneration became predominant. We identified two groups by the onset of their symptoms. In the "chronic" group (44%), onset was gradual, with these patients frequently having had one or more infiltrations at presentation to us. In the "acute" group (56%), there was an initial traumatic event that was variable in intensity and mechanism.
  
  
  CONCLUSIONS
  This isolated lesion of the infraspinatus at the myotendinous junction has not been previously described. It is recognized by its characteristic MRI appearance and is not generally seen on CT arthrograms as there is no communication with the joint. Its natural history appears to be of a progression from edema to fatty degeneration with or without myotendinous retraction and scarring. Its etiology has not yet been clearly established.
authors.affiliation: IRM des Sources. Clinique de la Sauvegarde, Lyon. tavernierthierry@wanadoo.fr
authors.forename: Th
authors.initials: T
authors.lastname: Tavernier
authors.forename: G
authors.initials: G
authors.lastname: Walch
authors.forename: R
authors.initials: R
authors.lastname: Barthelemy
authors.forename: L
authors.initials: L
authors.lastname: Nove-Josserand
authors.forename: J P
authors.initials: JP
authors.lastname: Liotard
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D017006:Rotator Cuff / Q000473:pathology*; D000070636:Rotator Cuff Injuries