title: Biomechanical analysis of bursal-sided partial thickness rotator cuff tears.
abstract: BACKGROUND
  Treatment of partial thickness supraspinatus tendon tears is controversial with no clearly defined treatment algorithms based on severity of tears. This study aims to evaluate the relationship between depth of partial thickness tears and strain.
  
  
  METHODS
  Bursal-sided partial thickness tears were created at 1 mm increments in depth at the anterior portion of the supraspinatus tendon to 3/4 tendon width on ten fresh-frozen shoulder specimens. The supraspinatus muscle was dynamically loaded from 0-50N, and strain recorded at both the anterior and posterior portions of the tendon.
  
  
  RESULTS
  Strain in the intact posterior portion increased monotonically with tear depth and supraspinatus force. Strain in the torn anterior portion decreased with increasing tear thickness and loading force. At 60% thickness tear, strain was significantly higher (P = 0.023) in the intact posterior portion compared to intact tendon. As the tear thickness exceeded 50% tendon thickness, the strain in the intact tendon rapidly increased nonlinearly.
  
  
  CONCLUSIONS
  Biomechanical results herein suggest increasing potential for tear propagation in the transverse plane with increasing depth of tears, and biomechanically supports repairs of grade III (>50% thickness).
authors.affiliation: Department of Orthopaedic Surgery, Northwestern University, Chicago, IL 60611, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Yang
authors.forename: Hyung-Soon
authors.initials: HS
authors.lastname: Park
authors.forename: Steven
authors.initials: S
authors.lastname: Flores
authors.forename: Steven D
authors.initials: SD
authors.lastname: Levin
authors.forename: Mohsen
authors.initials: M
authors.lastname: Makhsous
authors.forename: Fang
authors.initials: F
authors.lastname: Lin
authors.forename: Jason
authors.initials: J
authors.lastname: Koh
authors.forename: Gordon
authors.initials: G
authors.lastname: Nuber
authors.forename: Li-Qun
authors.initials: LQ
authors.lastname: Zhang
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002061:Bursa, Synovial / Q000473:pathology*; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011336:Probability; D017006:Rotator Cuff / Q000473:pathology*; D000070636:Rotator Cuff Injuries; D012680:Sensitivity and Specificity; D012785:Shoulder Joint / Q000473:pathology* / Q000503:physiopathology; D013180:Sprains and Strains / Q000473:pathology; D013314:Stress, Mechanical; D013708:Tendon Injuries / Q000473:pathology* / Q000503:physiopathology; D013718:Tensile Strength