In Vivo Assessment of Scapulohumeral Rhythm During Unconstrained Overhead Reaching in Asymptomatic Subjects

摘要

This study assessed shoulder motion using bone-fixed sensors to quantify scapulohumeral motion during unconstrained raising and lowering of the arm. Electromagnetic tracking devices rigidly fixed to bone pins recorded active scapular and humeral motion. We found a significant difference in the ratio of glenohumeral elevation to scapular upward rotation during arm raising (2.3) and lowering (2.7). Each degree of glenohumeral elevation yielded scapular upward rotation of 0.43° (raising) compared to downward rotation of 0.37° (lowering), across the motion arc. Until 125° of glenohumeral elevation, the scapula internally rotated then externally rotated with further elevation. Scapular upward rotation and posterior tilting progressively increased until maximal elevation. Scapulohumeral rhythm was greatest in the first increment of raising the arm and higher overall when lowering the arm. Understanding these data allows improved evaluation of potential motion abnormalities in patients with shoulder pathology and may improve treatment for restoration of normal shoulder motion.