Effect of Arm Elevation and Rotation on the Strain in the Repaired Rotator Cuff Tendon

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Abstract
In 14 cadaveric shoulders, a rotator cuff tear (2 cm wide and 1.5 cm long) was created and repaired under a 3-kg tensile force with the arm in adduction. Strain on the repaired tendon was measured at 0°, 15°, 30°, and 45° of elevation in the sagittal, scapular, and coronal planes and from 60° of internal rotation to 60° of external rotation. The strain in all of the planes decreased significantly with the arm elevated more than 30°. With 30° of elevation in the scapular and coronal planes, the strain increased in internal rotation and decreased in external rotation. In all of the positions measured, the strain in the sagittal plane was significantly greater than in the other planes. We concluded that more than 30° of elevation in the coronal or scapular plane and rotation ranging from 0° to 60° of external rotation compose the safe range of motion after repair of the rotator cuff.