title: Rotator cuff muscles lose responsiveness to anabolic steroids after tendon tear and musculotendinous retraction: an experimental study in sheep.
abstract: BACKGROUND
  Long-standing rotator cuff tendon tearing is associated with retraction, loss of work capacity, irreversible fatty infiltration, and atrophy of the rotator cuff muscles. Although continuous musculotendinous relengthening can experimentally restore muscular architecture, restoration of atrophy and fatty infiltration is hitherto impossible.
  
  
  OBJECTIVE
  Continuous relengthening with pharmacological stimulation of muscle growth using an anabolic steroid or insulin-like growth factor (IGF) can reverse atrophy and fatty infiltration as well as improve the work capacity of chronically retracted rotator cuff muscles in sheep.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Sixteen weeks after tenotomy of the infraspinatus (ISP) tendon, atrophy and fatty infiltration had developed in the retracted ISP muscle. The musculotendinous unit was continuously relengthened in 14 sheep during 6 weeks: Four sheep were treated without pharmacological stimulation, 4 with intramuscular administration of an anabolic steroid, and 6 with IGF before final repair and rehabilitation (12 weeks). Changes were documented by intraoperative measurements of muscle work capacity, histology, and computed tomography/magnetic resonance imaging.
  
  
  RESULTS
  Musculotendinous relengthening by continuous traction resulted in gains of length ranging from 0.7 cm in the IGF group to 1.3 cm in the control group. Fatty infiltration progressed in all groups, and the muscle's cross-sectional area ranged from 71% to 74% of the contralateral side at sacrifice and did not show any differences between groups in weight, volume, histological composition, or work capability of the muscle. The contralateral muscles in the anabolic steroid group, however, showed significantly higher (mean ± standard deviation) muscle work capacity of 10 ± 0.9 N·m than the contralateral muscles of the control group (6.8 ± 2.4 N·m) (P < .05). This was accompanied by an increased mean muscle fiber area as well as by an unusual gain in the animals' weight after injection of the anabolic steroid.
  
  
  CONCLUSIONS
  Subcutaneous continuous relengthening of a chronically retracted musculotendinous unit is feasible and advances the retracted musculotendinous junction toward its original position. This does not change the muscle work capacity. Whereas anabolic steroids have been shown to be effective in preventing classic degenerative muscle changes after tendon tears, neither an anabolic steroid nor IGF contributes to regeneration of the muscle once degenerative changes are established.
  
  
  CONCLUSIONS
  The findings demonstrate that muscle cells lose reactiveness to an anabolic steroid and IGF once retraction has led to fatty infiltration and atrophy of the muscle. Retraction of the muscle after tendon tears must be avoided by early repair, particularly in an athlete, as no regeneration can be achieved by mechanical or pharmacological means at this time.
authors.affiliation: Balgrist University Hospital, University of Zürich, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Gerber
authors.forename: Dominik C
authors.initials: DC
authors.lastname: Meyer
authors.forename: Brigitte
authors.initials: B
authors.lastname: Von Rechenberg
authors.forename: Hans
authors.initials: H
authors.lastname: Hoppeler
authors.forename: Robert
authors.initials: R
authors.lastname: Frigg
authors.forename: Mazda
authors.initials: M
authors.lastname: Farshad
mesh_terms: D045930:Anabolic Agents / Q000494:pharmacology*; D000818:Animals; D001284:Atrophy / Q000188:drug therapy / Q000473:pathology; D006801:Humans; D009119:Muscle Contraction / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000473:pathology / Q000601:surgery; D009277:Nandrolone / Q000031:analogs & derivatives* / Q000494:pharmacology; D000077603:Nandrolone Decanoate; D017006:Rotator Cuff / Q000187:drug effects* / Q000473:pathology / Q000601:surgery; D000070636:Rotator Cuff Injuries; D012756:Sheep; D013002:Somatomedins / Q000494:pharmacology*; D013708:Tendon Injuries / Q000188:drug therapy* / Q000473:pathology / Q000601:surgery; D013710:Tendons / Q000187:drug effects / Q000473:pathology / Q000601:surgery; D014143:Traction
chemical_list: D045930:Anabolic Agents; D013002:Somatomedins; D009277:Nandrolone; D000077603:Nandrolone Decanoate