title: Evaluation of cartilage degeneration in a rat model of rotator cuff tear arthropathy.
abstract: OBJECTIVE
  Rotator cuff tears are the most common injury seen by shoulder surgeons. Glenohumeral osteoarthritis develops in many late-stage rotator cuff tear patients as a result of torn cuff tendons, termed "cuff tear arthropathy." However, the mechanisms of cuff tear arthropathy have not been fully established. It has been hypothesized that a combination of synovial and mechanical factors contribute equally to the development of cuff tear arthropathy. The goal of this study was to assess the utility of this model in investigating cuff tear arthropathy.
  
  
  METHODS
  We used a rat model that accurately reflects rotator cuff muscle degradation after massive rotator cuff tears through either infraspinatus and supraspinatus tenotomy or suprascapular nerve transection. Using a modified Mankin scoring system, we found significant glenohumeral cartilage damage after both rotator cuff tenotomy and suprascapular nerve transection after only 12 weeks.
  
  
  RESULTS
  Cartilage degeneration was similar between groups and was present on both the humeral head and the glenoid. Denervation of the supraspinatus and infraspinatus muscles without opening the joint capsule caused cartilage degeneration similar to that found in the tendon transection group.
  
  
  CONCLUSIONS
  Our results suggest that altered mechanical loading after rotator cuff tears is the primary factor in cartilage degeneration after rotator cuff tears. Clinically, understanding the process of cartilage degeneration after rotator cuff injury will help guide treatment decisions in the setting of rotator cuff tears.
  
  
  METHODS
  Basic science study, animal model.
authors.affiliation: Department of Veterans Affairs, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA; Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA.
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Kramer
authors.forename: Blake M
authors.initials: BM
authors.lastname: Bodendorfer
authors.forename: Dominique
authors.initials: D
authors.lastname: Laron
authors.forename: Jason
authors.initials: J
authors.lastname: Wong
authors.forename: Hubert T
authors.initials: HT
authors.lastname: Kim
authors.forename: Xuhui
authors.initials: X
authors.lastname: Liu
authors.forename: Brian T
authors.initials: BT
authors.lastname: Feeley
mesh_terms: D000818:Animals; D002356:Cartilage / Q000473:pathology; D002357:Cartilage Diseases / Q000209:etiology / Q000503:physiopathology*; D004195:Disease Models, Animal; D005260:Female; D058430:Humeral Head / Q000473:pathology; D010003:Osteoarthritis / Q000209:etiology / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017006:Rotator Cuff / Q000503:physiopathology*; D000070636:Rotator Cuff Injuries; D012421:Rupture; D012540:Scapula / Q000473:pathology; D012785:Shoulder Joint / Q000503:physiopathology*; D013708:Tendon Injuries / Q000150:complications / Q000503:physiopathology*
keywords: Animal Model; Basic Science Study; Massive rotator cuff tear; arthropathy; articular cartilage; histology; osteoarthritis