title: A comparative analysis of fatty infiltration and muscle atrophy in patients with chronic rotator cuff tears and suprascapular neuropathy.
abstract: BACKGROUND
  Little is known of the mechanisms that lead to the muscle changes associated with rotator cuff disorders. We have observed that the magnetic resonance imaging (MRI) appearance of fatty infiltration (FI) and muscle atrophy (MA) differ between chronic cuff tears and suprascapular neuropathy, suggesting different pathophysiology. This study compares the different MRI changes that occur in chronic cuff tears and suprascapular neuropathy.
  
  
  METHODS
  Two groups were retrospectively identified: (1) RCT group (20 shoulders): patients with chronic tears of the supraspinatus and/or infraspinatus without electromyographic (EMG) evidence of suprascapular neuropathy; (2) neuro group (17 shoulders): patients with EMG documented suprascapular nerve dysfunction and absence of a rotator cuff tear. Magnetic resonance arthrograms were analyzed for the degree of FI and MA, and the morphology of the muscle was assessed, in particular the muscle border, pattern of FI, and extent of involvement.
  
  
  RESULTS
  The muscle changes that occur following chronic cuff tears differ from that following denervation secondary to suprascapular neuropathy, especially with respect to the muscle border, degree of perineural fat, and overall distribution of FI. Highly specific and characteristic morphological patterns of FI exist for both chronic cuff tears and suprascapular neuropathy.
  
  
  CONCLUSIONS
  Chronic rotator cuff tendon tears and suprascapular neuropathy are both associated with FI and MA of the rotator cuff muscles. The pattern of FI is markedly different in the 2 situations. These findings have diagnostic potential and may serve as a basis for further research concerning type, severity, and evolution of FI under different conditions and after treatment.
authors: Department of Orthopaedics, University of Zürich, Balgrist University Hospital, Zürich, Switzerland.
authors: Silvan
authors: S
authors: Beeler
authors: Eugene T H
authors: ET
authors: Ek
authors: Christian
authors: C
authors: Gerber
mesh_terms: D000273:Adipose Tissue / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001175:Arthrography; D002908:Chronic Disease; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology; D009133:Muscular Atrophy / Q000473:pathology*; D010523:Peripheral Nervous System Diseases / Q000473:pathology*; D012189:Retrospective Studies; D017006:Rotator Cuff / Q000294:innervation / Q000473:pathology*; D000070636:Rotator Cuff Injuries; D012782:Shoulder / Q000473:pathology; D013708:Tendon Injuries / Q000473:pathology*
keywords: Anatomic Study; Fatty infiltration; Imaging; muscle atrophy; rotator cuff tear; suprascapular neuropathy