QUANTIFICATION OF THE DYNAMIC GLENOHUMERAL STABILITY PROVIDED BY THE ROTATOR CUFF MUSCLES IN THE LATE COCKING PHASE OF THROWING

  • Seok-Beom Lee
  • Shawn W. O'Driscoll
  • Bernard F. Morrey
  • Kai-Nan An
Keywords: dynamic stability, rotator cuff, late cocking, dynamic stability index

Abstract

The purpose of this study was to investigate quantitatively the dynamic glenohumeral stability provided by the rotator cuff muscles in the late-cocking phase of throwing. Using ten cadaveric shoulders, a new biomechanical parameter (dynamic stability index) was calculated considering compressive and shear forces to the glenoid provided by each cuff muscle. The rotator cuff muscles provided the joint with significant dynamic stability in the late cocking. However, the dynamic stability provided by the cuff muscles with the arm in coronal plane significantly decreased when compared with that in the scapular plane. Rehabilitation of the throwing athletes should emphasize strengthening of the external and internal rotators. Moving the arm into the coronal plane in the late cocking phase should be avoided by a specific strengthening program to prevent further anatomic damage to the static stabilizers.