title: The influence of partial subscapularis tendon tears combined with supraspinatus tendon tears.
abstract: BACKGROUND
  With the advent of arthroscopy, more partial subscapularis tears are being recognized. The biomechanical effects of partial subscapularis tears are unknown, and there is no consensus as to their treatment. Therefore, the objective of this study was to evaluate and to quantify the changes in range of motion and glenohumeral kinematics for isolated subscapularis partial tears, combined subscapularis and supraspinatus tears, supraspinatus repair, and combined supraspinatus and subscapularis repair.
  
  
  METHODS
  Six cadaveric shoulders were tested in the scapular plane with 0°, 30°, and 60° shoulder abduction under 6 conditions: intact; ¼ subscapularis tear; ½ subscapularis tear; ½ subscapularis and complete supraspinatus tear; supraspinatus repair; and supraspinatus and subscapularis repair. Maximum internal and external rotation and glenohumeral kinematics were measured under physiologic muscle loading condition. A repeated measures analysis of variance with a Tukey post hoc test was used for statistical analysis.
  
  
  RESULTS
  Maximum external rotation was significantly increased after ¼ subscapularis tear at 30° abduction and in all abduction angles with ½ subscapularis tear (P < .05). The 2 repair conditions did not restore external rotation to the intact level. At maximum internal and external rotation, there was a significant superior shift in the humeral head apex position with ¼ subscapularis tear at 30° abduction and with ½ subscapularis tear at 60° abduction (P < .05). Repair of the supraspinatus tendon partially corrected abnormal kinematics; however, neither repair restored abnormal kinematics to intact.
  
  
  CONCLUSIONS
  Additional repair of the partial subscapularis tear with supraspinatus tear did not affect external rotation or glenohumeral kinematics. Further studies are needed to evaluate different subscapularis repair techniques.
  
  
  METHODS
  Basic science study, biomechanics.
authors: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System and University of California, Irvine, CA, USA; Department of Orthopedic Surgery, Sungkyunkwan University College of Medicine, Samsung Medical Center, Seoul, South Korea.
authors: Jae Chul
authors: JC
authors: Yoo
authors: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System and University of California, Irvine, CA, USA.
authors: Michelle H
authors: MH
authors: McGarry
authors: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System and University of California, Irvine, CA, USA.
authors: Bong Jae
authors: BJ
authors: Jun
authors: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System and University of California, Irvine, CA, USA.
authors: Jonathan
authors: J
authors: Scott
authors: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System and University of California, Irvine, CA, USA. Electronic address: tqlee@med.va.gov.
authors: Thay Q
authors: TQ
authors: Lee
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D017006:Rotator Cuff / Q000503:physiopathology* / Q000601:surgery; D000070636:Rotator Cuff Injuries; D012782:Shoulder / Q000503:physiopathology / Q000601:surgery; D000070599:Shoulder Injuries; D012785:Shoulder Joint / Q000503:physiopathology* / Q000601:surgery
keywords: Subscapularis; arthroscopy; kinematics; range of motion