Abductors of the Shoulder

- Discussion:
    - see: rotator cuff
    - 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;

- Role of Rotator Cuff in Shoulder Abduction:

    - w/ suprascapular nerve block (which elminates supraspinatus & infraspinatus function) there is still full abduction of arm although it is about 50% weaker;
    - remaining teres minor and subscapularis provide glenohumeral compression and humeral depression;
    - as arm is abducted to 90 deg direction of pull of deltoid approximates that of the supraspinatus;
    - hence pts w/ large tears of rotator cuff can often actively keep the arm abducted to 90 deg but may not be able to initiate abduction to 90 deg

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Friday, January 4, 2013 10:30 am