title: Tendon response to pharmaco-mechanical stimulation of the chronically retracted rotator cuff in sheep.
abstract: OBJECTIVE
  Chronic tearing of tendons is associated with molecular and structural alterations causing biomechanical changes, which compromise musculotendinous function and become limiting factors for tendon repair. This study investigated the histological response of chronically retracted sheep rotator cuff tendons to mechanical and pharmacological stimulation in view of tendon repair.
  
  
  METHODS
  Sixteen weeks after experimental release of the infraspinatus tendon in 20 sheep, the retracted musculotendinous unit was subjected to continuous traction either with [anabolic steroids (nandrolone) group/insulin-like growth factor (IGF) group] or without (control group) additional pharmacological treatment during 6 weeks. A new degeneration score for tendinous tissues (DSTT), based on established knowledge on histological changes associated with tendon degeneration, was used for histological analysis at the time of tendon release, at the beginning of continuous re-lengthening and at repair in all animals.
  
  
  RESULTS
  The DSTT score (inter-observer correlation: r = 0.83), quantifiably representing tendon degeneration, improved from 15.5 (SD 1.3) points before to 9.8 (SD 3.8) points after re-lengthening. It improved in a qualitatively and quantitatively similar fashion if pharmacological stimulation was added. The nandrolone group improved from 13.7 (SD 1.6) to 9.8 (SD 1.9) and the IGF group from 13.3 (SD 3.6) to 8.8 (SD 1.8) points.
  
  
  CONCLUSIONS
  Mechanical stimulation significantly reduced tissue degeneration. However, the addition of a pharmacological stimulation with anabolic steroids or IGF had neither a measurable positive nor negative effect on the degenerative process. Therefore, this investigation does neither support the additional pharmacological use of the anabolic steroid nandrolone or of IGF decanoate for restoration of tendon degeneration, nor otherwise provide evidence for additional tendon damage, if those substances are used to alter the muscular metabolism.
authors.affiliation: Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zurich, Switzerland, karl.wieser@balgrist.ch.
authors.forename: Karl
authors.initials: K
authors.lastname: Wieser
authors.forename: Mazda
authors.initials: M
authors.lastname: Farshad
authors.forename: Dominik C
authors.initials: DC
authors.lastname: Meyer
authors.forename: Philipp
authors.initials: P
authors.lastname: Conze
authors.forename: Brigitte
authors.initials: B
authors.lastname: von Rechenberg
authors.forename: Christian
authors.initials: C
authors.lastname: Gerber
mesh_terms: D000287:Administration, Topical; D045930:Anabolic Agents / Q000008:administration & dosage*; D000728:Androgens / Q000008:administration & dosage; D000818:Animals; D002908:Chronic Disease; D004195:Disease Models, Animal; D004343:Drug Implants; D005260:Female; D006133:Growth Substances / Q000008:administration & dosage*; D007273:Injections, Intramuscular; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage*; D008863:Microspheres; D009277:Nandrolone / Q000008:administration & dosage*; D017006:Rotator Cuff / Q000187:drug effects / Q000473:pathology* / Q000601:surgery; D000070636:Rotator Cuff Injuries; D012756:Sheep; D013708:Tendon Injuries / Q000188:drug therapy* / Q000473:pathology / Q000601:surgery; D013710:Tendons / Q000187:drug effects / Q000473:pathology / Q000601:surgery; D014143:Traction; D014945:Wound Healing / Q000187:drug effects
chemical_list: D045930:Anabolic Agents; D000728:Androgens; D004343:Drug Implants; D006133:Growth Substances; D007334:Insulin-Like Growth Factor I; D009277:Nandrolone