title: Quantitative analysis of muscle and tendon retraction in chronic rotator cuff tears.
abstract: BACKGROUND
  Musculotendinous retraction is a limiting factor for repair of long-standing rotator cuff tears. However, it is currently unknown to what extent the muscle and tendon contribute to the degree of total retraction. Further understanding of this may possibly influence the strategy of musculotendinous reconstruction.
  
  
  OBJECTIVE
  To analyze the contribution of muscle and tendon to the process of myotendinous retraction.
  
  
  METHODS
  Cross-sectional study; Level of evidence, 3.
  
  
  METHODS
  Magnetic resonance imaging of 130 shoulders with intact (n = 20) or completely torn supraspinatus tendons was analyzed. Fatty infiltration of the supraspinatus muscle was graded according to Goutallier stages. The degree of retraction of the tendon stump and of the musculotendinous junction was assessed.
  
  
  RESULTS
  There were 30 shoulders without evidence of supraspinatus fatty infiltration, 25 with stage 1, 23 with stage 2, 25 with stage 3, and 15 with stage 4 changes. The corresponding tear sizes (distance of tendon end from greater tuberosity) were 4, 21, 27, 37, and 41 mm; the distance of the myotendinous junction from the greater tuberosity was 22, 33, 39, 48, and 48 mm; and the length of the tendons (distance of tendon end to myotendinous junction) was 19, 13, 12, 11, and 8 mm, respectively. In Goutallier stage 3 and above, and in case of a positive tangent sign, the musculotendinous junction was, in 90% of the cases, retracted to or beyond the glenoid.
  
  
  CONCLUSIONS
  Musculotendinous retraction in chronic rotator cuff tears results mainly from shortening of the muscle fibers but in advanced stages results also from shortening of the tendon tissue itself. The present data demonstrate, for the first time, that the residual tendon stump in a tendon tear does not have the length of the original tendon and is further shortened over time. Therefore, direct anatomic tendon reinsertion will result in lengthening of the supraspinatus muscle greater than what it would have been before the tear.
authors.affiliation: Orthopedic Department, Balgrist University Hospital, University of Zurich, CH-8008 Zurich, Switzerland.
authors.forename: Dominik C
authors.initials: DC
authors.lastname: Meyer
authors.forename: Mazda
authors.initials: M
authors.lastname: Farshad
authors.forename: Nadja A
authors.initials: NA
authors.lastname: Amacker
authors.forename: Christian
authors.initials: C
authors.lastname: Gerber
authors.forename: Karl
authors.initials: K
authors.lastname: Wieser
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D003287:Contrast Media; D003430:Cross-Sectional Studies; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000293:injuries*; D011446:Prospective Studies; D017006:Rotator Cuff / Q000033:anatomy & histology; D000070636:Rotator Cuff Injuries; D013708:Tendon Injuries / Q000175:diagnosis*; D055815:Young Adult
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA