The object of the present study of autopsy specimens was to evaluate distal numeral migration during abduction allowed by sequential severance of capsular and ligamentous structures stabilizing the shoulder joint. A kinesiologic testing device continuously registered distal humeral migration, abduction angle, rotation, and flexion-extension. No distally directed force was applied to the humerus except the weight of the apparatus. Significant distal migration was recorded in the entire range of abduction (0°-60°) after solitary severance of the coracohumeral ligament as well as the proximal part of the anterior joint capsule. Further sectioning of the proximal part of the posterior capsule did not significantly increase distal humeral migration. Maximum distal migration (25 mm) was measured at 20° of abduction. Applying an internal torque to the humerus significantly prevented distal migration as long as the posterior capsule was kept intact. Clinical testing for distal humeral migration should be performed with the shoulder joint at 20° of abduction and neutral rotation. Furthermore, distal humeral migration can be significantly reduced by internal rotation of the humerus when the posterior joint capsule is intact.
From The Biomechanics Laboratory. Orthopaedic Hospital, University of Aarhus, Aarhus, Denmark.
Reprint requests to Peter Helmig, M.D., Orthopaedic Hospital, Randersvej 1, DK-8200 Aarhus N, Denmark.
Received: September 27, 1988.