Abductors of the Shoulder Wheeless

Description: abduction of shoulder is a smooth, integrated motion which has been termed scapulohumeral rhythm by Codman;
- disruption of this smooth motion is important since asymmetrical movement usually indicates a chronic pathological disorder of the shoulder;
- there is a 2:1 ratio of movement in GHJ & scapulothoracic joints;
- Clavicle also plays part in elevation of the arm, w/ about 40 deg of motion occurring at sternoclavicular joint & 20 deg in AC joint during full abduction of the shoulder;
Wheeless' Textbook of Orthopaedics