title: Chronic massive rotator cuff tear in rats: in vivo evaluation of muscle force and three-dimensional histologic analysis.
abstract: BACKGROUND
  Massive rotator cuff tear repair is frequently complicated by unsatisfactory clinical results due to possible tendon retraction, muscle atrophy, and fatty degeneration. The objective of this study was the development of a chronic massive tear in a rat model and the evaluation of the muscle force in vivo and of the histologic changes in a 3- dimensional manner.
  
  
  METHODS
  To simulate massive rotator cuff tears, both the supraspinatus (SS) and the infraspinatus (IS) tendons were surgically detached from the right humerus of 15 male adult Sprague-Dawley rats. Twelve weeks postoperatively, all animals underwent isometric tension recordings of both the SS and IS muscles. Histologic analysis and image deconvolution processing were performed to estimate the presence and the distribution of atrophy in 3 dimensions.
  
  
  RESULTS
  An overall 30% and 35% reduction in muscle force of the SS and IS muscles, respectively, was observed compared with the left uninjured shoulder (P < .005). Histologic analysis revealed that the degeneration and the fatty infiltration were more evident near the tendon and at the dorsal side in both muscle groups.
  
  
  CONCLUSIONS
  These results show that functional impairment of SS and IS muscles after chronic massive tendon tears could be attributed to the decrease in muscle force production during their repair on the greater tuberosity and, second, to the comparatively greater degeneration of their dorsal part.
authors: First Orthopaedic Department, Aristotle University of Thessaloniki, G. Papanikolaou General Hospital, Exohi, Thessaloniki, Greece. Electronic address: kostasditsios@gmail.com.
authors: Konstantinos
authors: K
authors: Ditsios
authors: First Orthopaedic Department, Aristotle University of Thessaloniki, G. Papanikolaou General Hospital, Exohi, Thessaloniki, Greece.
authors: Achilleas
authors: A
authors: Boutsiadis
authors: Department of Physiology, Medical School, Aristotle University of Thessaloniki, Greece.
authors: Dorothea
authors: D
authors: Kapoukranidou
authors: Department of Physiology, Medical School, Aristotle University of Thessaloniki, Greece.
authors: Athanasios
authors: A
authors: Chatzisotiriou
authors: Department of Physiology, Medical School, Aristotle University of Thessaloniki, Greece.
authors: Ioannis
authors: I
authors: Kalpidis
authors: Department of Physiology, Medical School, Aristotle University of Thessaloniki, Greece.
authors: Maria
authors: M
authors: Albani
authors: First Orthopaedic Department, Aristotle University of Thessaloniki, G. Papanikolaou General Hospital, Exohi, Thessaloniki, Greece.
authors: Anastasios
authors: A
authors: Christodoulou
mesh_terms: D000818:Animals; D002908:Chronic Disease; D008297:Male; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000473:pathology* / Q000503:physiopathology; D009133:Muscular Atrophy / Q000473:pathology / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017006:Rotator Cuff / Q000473:pathology / Q000503:physiopathology; D000070636:Rotator Cuff Injuries; D012421:Rupture; D013708:Tendon Injuries / Q000473:pathology* / Q000503:physiopathology; D013710:Tendons / Q000473:pathology / Q000503:physiopathology
keywords: 3-D atrophy; Rat model; isometric tension recordings