title: Decreasing glenoid inclination improves function in shoulders with simulated massive rotator cuff tears.
abstract: BACKGROUND
  A massive rotator cuff tear leads to poor shoulder function as evidenced by diminished glenohumeral abduction and superior translation of the humeral head compared to its normal position. The inclination angle of the glenoid has been associated with rotator cuff tears. The objective of this study was to quantify the effect of a decreased glenoid inclination angle on glenohumeral kinematics during active abduction in shoulders with a simulated, massive rotator cuff tear.
  
  
  METHODS
  Eight fresh-frozen full upper extremities were tested using a dynamic shoulder testing apparatus. After recording the kinematics of the intact shoulder, a massive rotator cuff tear was surgically simulated. An osteotomy of the glenoid was then performed and the inclination angle was decreased by 30 degrees . The translation of the humeral head during abduction and the maximum abduction angle were recorded.
  
  
  RESULTS
  With an intact rotator cuff minimal humeral head translation on the glenoid occurred and the maximum abduction angle was mean 85.5 degrees (SD 7.4 degrees ). A massive rotator cuff tear resulted in superior translation of the humeral head with impingement on the acromion. The maximum abduction angle was mean 15.5 degrees (SD 9.4 degrees ). Decreasing the inclination angle of the glenoid resulted in a significant reduction of superior humeral head translation during abduction and there was no impingement on the acromion. The maximum abduction achieved was mean 28.5 degrees (SD 17.0 degrees ).
  
  
  CONCLUSIONS
  From a clinical perspective the reduced superior translation may decrease shoulder pain since the humeral head no longer impinges on the acromion. Further investigations are necessary to assess if the improvement in abduction is clinically significant.
authors.affiliation: Department of Orthopaedic and Trauma Surgery, University Hospital Freiburg, Hugstetter Str. 55, 79106 Freiburg, Germany.
authors.forename: Gerhard G
authors.initials: GG
authors.lastname: Konrad
authors.forename: Max
authors.initials: M
authors.lastname: Markmiller
authors.forename: John T
authors.initials: JT
authors.lastname: Jolly
authors.forename: Axel E
authors.initials: AE
authors.lastname: Ruter
authors.forename: Norbert P
authors.initials: NP
authors.lastname: Sudkamp
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: McMahon
authors.forename: Richard E
authors.initials: RE
authors.lastname: Debski
mesh_terms: D002102:Cadaver; D006801:Humans; D066298:In Vitro Techniques; D007593:Joint Instability / Q000503:physiopathology*; D008875:Middle Aged; D016059:Range of Motion, Articular; D020127:Recovery of Function; D017006:Rotator Cuff / Q000503:physiopathology*; D000070636:Rotator Cuff Injuries; D012785:Shoulder Joint / Q000503:physiopathology*