Effect of shoulder immobilization position and activities of daily living on the stiffness of the repaired supraspinatus tendon

Background: Although tension on the supraspinatus tendon may be increased by wearing an abduction brace in an improper position or activities of daily living with the operated arm in the brace, the amount of tension has not been objectively evaluated. Methods: Eighteen patients who underwent arthroscopic rotator cuff repair were enrolled. The stiffness of the repaired supraspinatus tendon was measured with ultrasound elastography to estimate the tension on the repaired tendon. Measurements were performed in 5 immobilization positions (0°, 30°, and 45° of arm elevation in the scapular plane; 30° of arm elevation in the scapular plane+60° (horizontal adduction) and −60° (horizontal abduction)) and 3 static positions simulating drinking, brushing teeth, and dressing. Findings: Stiffness at 30° of scapular plane elevation was lower than 0° of scapular plane elevation (P = 0.034), 30° of elevation in the scapular plane+60° (P < 0.001), and −60° (P < 0.001). There was no significant difference in the stiffness between 30° and 45° of scapular plane elevation (P = 1.000). The stiffness was the greatest at 30° of elevation in the scapular plane−60° among the 5 immobilization positions. The stiffnesses at drinking and brushing teeth were greater than 30° of scapular plane elevation (P < 0.001). Interpretation: Immobilization with the arm ≥30° of elevation in the scapular plane may be an optimal position for minimizing stiffness or tension on the repaired tendon. Drinking and brushing teeth may need to be performed using the non-operated arm to protect the repaired tendon.