title: Fatty infiltration does not progress after rotator cuff repair in a rabbit model.
abstract: OBJECTIVE
  The purpose of this study is to evaluate the changes in fatty infiltration of the rotator cuff after it is repaired.
  
  
  METHODS
  The supraspinatus muscle was unilaterally detached from the greater tuberosity in 15 New Zealand white rabbits. Six weeks after muscle detachment, 5 rabbits were killed to halt the process of fatty infiltration and 10 rabbits underwent primary repair of the rotator cuff. Six months after repair, the remaining 10 rabbits were killed, and the muscle specimens were examined microscopically to evaluate the muscle with respect to fatty infiltration.
  
  
  RESULTS
  Fatty infiltration was evident 6 weeks after detachment of the supraspinatus tendon (P = .0012, analysis of variance). This infiltration was greatest at the musculotendinous junction (P = .0005) and decreased toward the muscle origin (P = .29). Six months after repair of the supraspinatus, there was no progression of fatty infiltration in the repaired muscle as compared with the controls (P = .3).
  
  
  CONCLUSIONS
  Fatty infiltration of the rotator cuff in this animal model occurs as early as 6 weeks after a rotator cuff tear. After repair of the rotator cuff, the process of fatty infiltration does not progress any further. The changes that take place in this rabbit model in the first 6 weeks after a rotator cuff tear appear to be irreversible even with successful rotator cuff repair.
  
  
  CONCLUSIONS
  The presence of fatty infiltration of a torn rotator cuff does not preclude a successful repair. The repair can prevent further progression and atrophy of the rotator cuff, but the changes that appear in the muscle as early as 6 weeks after a rotator cuff tear appear to be irreversible.
authors.affiliation: Department of Orthopaedic Surgery, Boonshoft School of Medicine, Wright State University, Dayton, Ohio 45409, USA. ljrubino@hotmail.com
authors.forename: L Joseph
authors.initials: LJ
authors.lastname: Rubino
authors.forename: Dominic C
authors.initials: DC
authors.lastname: Sprott
authors.forename: Harold F
authors.initials: HF
authors.lastname: Stills
authors.forename: Lynn A
authors.initials: LA
authors.lastname: Crosby
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D000818:Animals; D022125:Lacerations / Q000473:pathology / Q000601:surgery*; D019637:Orthopedic Procedures; D011184:Postoperative Period; D011817:Rabbits; D017006:Rotator Cuff / Q000473:pathology* / Q000601:surgery*; D000070636:Rotator Cuff Injuries; D013997:Time Factors