Effect of arm elevation and rotation on the strain in the repaired rotator cuff tendon. A cadaveric study.

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 degrees, 15 degrees, 30 degrees, and 45 degrees of elevation in the sagittal, scapular, and coronal planes and from 60 degrees of internal rotation to 60 degrees of external rotation. The strain in all of the planes decreased significantly with the arm elevated more than 30 degrees. With 30 degrees 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 degrees of elevation in the coronal or scapular plane and rotation ranging from 0 degrees to 60 degrees of external rotation compose the safe range of motion after repair of the rotator cuff.