Optimal shoulder immobilization postures following surgical repair of rotator cuff tears: a simulation analysis

Background: There is a high incidence of retear following surgical repair of rotator cuff tears. Postoperative shoulder immobilization is commonly prescribed to protect the repair; but there is no consensus on the best immobilization postures. Methods: A generic musculoskeletal model of the shoulder was used to simulate postoperative immobilization of full thickness rotator cuff tears involving the supraspinatus only and the supraspinatus concomitantly with the infraspinatus or subscapularis. Optimal immobilization postures, which simultaneously minimized the stresses in the repaired tendons and the angle of humerus elevation, were obtained. Results: For isolated supraspinatus tears, elevation of the humerus in planes close to the scapular plane was suggested. When the infraspinatus was also involved, planes posterior to the scapular plane were suggested; while, if the subscapularis was also involved, planes anterior to the scapular plane and internal rotation were suggested. The required thoracohumeral elevation angles ranged from 58 degrees to 109 degrees, depending on the tear length and the muscles involved. The optimal postures reduced the stresses in the repaired tendons by between 29% and 90%. Conclusion: Prescription of immobilization posture for a patient should be based on the conditions of the tear repaired. Appropriate choice of immobilization posture will reduce the stress in the repair, and as such has the potential to reduce retear rates. Level of evidence: Basic Science Study, Computer Modeling. (C) 2013 Journal of Shoulder and Elbow Surgery Board of Trustees.