Dynamic loading of the shoulder during the Codman exercise

Studies of biomechanical loading on proximal humerus fixation plates (PHP) have been limited to cadaveric models of non-uniform magnitudes of axial, bending, and torsional loads or static, physiological-like loading. The goal of this investigation was to develop an in vivo association between the dynamic loading on the shoulder joint with anatomic position to better understand PHP loading. The motion of the right arm and thorax during the performance of the Codman exercise of five healthy male volunteers was studied using an opto-electronic motion capture system. Time referenced angular joint positions were calculated using Euler angles, from which angular velocities and accelerations were derived, and the net shoulder moments were calculated using the anthropometry for elderly females (ges 60 yrs.). Results indicate that the PHP may experience minimal moment loads from medial/lateral arm rotations. The results also suggest that the Codman exercise may not be entirely active.