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This movement may be broken down into two parts: True abduction of the arm, which takes the humerus from parallel to the spine to perpendicular; and upward rotation of the scapula, which raises the humerus above the shoulders until it points straight upwards.
Downward rotation would be prevented by co-contraction of other muscles that elevate the spine, the upper fibers of the trapezius, which is an upward rotator. When the shoulder is fixed, levator scapulae rotates to the same side and flexes the cervical spine laterally.
Additional muscle deficits can contraindicate tendon transfer, namely the serratus anterior muscle or the muscles-to-be-transferred themselves. Serratus anterior muscle deficit is another cause of scapular winging and decreases the efficacy of an Eden–Lange procedure, but it can be overcome with a simultaneous pectoralis major transfer .
The pec minor also works in conjunction with the rhomboid muscle and levator scapulae to perform downward rotation of the scapulae. Muscles which attach to the scapulae that adduct and extend the arm include the posterior deltoid muscles, the teres major, and minor stabilizing contribution from some rotator cuff muscles (infraspinatus and teres ...
Iliac crest, lumbar fascia, spines of lower six thoracic vertebrae, lower 3-4 ribs, inferior angle of scapula Floor of bicipital groove of humerus Teres major: Lower third of lateral border of scapula: Medial lip of bicipital groove of humerus Teres minor: Upper two thirds of lateral border of scapula Greater tubercle of humerus Lateral rotation
The upper and lower fibers tend to rotate the scapula around the sternoclavicular articulation so that the acromion and inferior angles move up and the medial border moves down (upward rotation). The upper and lower fibers work in tandem with serratus anterior to upwardly rotate the scapulae, and work in opposition to the levator scapulae and ...
Animation of the shoulder joint. The muscles shown are subscapularis muscle (at right), infraspinatus muscle (at top left), teres minor muscle (at bottom left) The movement of the scapula across the rib cage in relation to the humerus is known as the scapulohumeral rhythm, and this helps to achieve a further range of movement. This range can be ...
The coracoid process acts as an attachment and origin for a large number of muscles (attached muscles not labeled here). The coracoid process is a thick curved process attached by a broad base to the upper part of the neck of the scapula; [2] it runs at first upward and medially; then, becoming smaller, it changes its direction, and projects forward and laterally.