CHAPTER 8 Structure and Function of the Shoulder Complex


confi guration of each structure plays a role in the kine- matics of the individual joints and in upper extremity movement as a whole.


BONES Sternum


The sternum is the fl at, long bone located in the midline of the anterior thorax and acts as an anterior anchor for the ribs. The regions of the sternum are, from proxi- mal to distal, the manubrium, the body, and the xiphoid process. The clavicular facets are located on each side of the manubrium and are the site of the sternal articulation with the clavicle. Between the two facets is the jugular notch (sternal notch), which is located at the superior border of the manubrium.


Clavicle


The clavicle is the curved bone that articulates medially with the sternum and laterally with the scapula. The costal facet of the clavicle links to the fi rst rib. In the anatomical position, the clavicle lies about 20° posterior to the frontal plane and slightly above the horizontal plane. The bone has a convex shape medially and curves to a concave shape laterally.


Scapula


The scapula is located on the posterolateral aspect of the thorax. In the anatomical position, it is typically at the level between T2 and T7 vertebrae. The scapula has three sides, or borders: the medial (or vertebral) border, the lateral (or axillary) border, and the superior border. The medial border runs parallel to the vertebral column and is typically about 6 cm from the spine. The upper corner of the medial border is the superior angle, and the lower corner is the inferior angle of the scapula. The lateral border runs from the inferior angle to the lower border of the glenoid cavity. The superior border runs from the superior angle to the base of the coracoid process.


The scapular spine divides the posterior surface of the scapula into the supraspinous fossa and the infraspi- nous fossa. The lateral end of the scapular spine fl attens to form the prominent acromion process. The coracoid process protrudes from the anterior surface of the scapula and is the site of attachment for several muscle groups. The subscapular fossa is located on the ventral surface of the scapula. Figure 8.2 depicts the landmarks of the scapula.


The acromion process protrudes laterally and forms a shelf over the glenoid fossa (Fig. 8.3). Within the concave fossa are the supraglenoid and infraglenoid tubercles. These tubercles serve as muscle attachment sites: The long head of the biceps attaches to the supraglenoid


B


Inferior angle


Coracoid process


Acromion process


Superior border


Glenoid cavity


Superior angle


155


Lateral border


Subscapular fossa


A


Superior angle


Suprascapular notch


Superior border


Coracoid process


Acromion process


Medial border


Inferior angle


Supraspinatus fossa


Medial border


Infraspinatus fossa


Lateral border


Figure 8.2 Landmarks of the scapula. (A) Anterior view of the scapula. (B) Posterior view. (From Roy S, Wolf SL, Scalzitti DA. The Rehabilitation Specialist’s Handbook, 4th ed. Philadelphia, PA: F. A. Davis Company, 2013: p. 51, with permission.)


Supraglenoid tubercle


Acromion process


Coracoid process


Glenoid fossa


Lateral border


Infraglenoid tubercle


Figure 8.3 Frontal plane view of the scapula showing the glenoid fossa. (From Starkey C, Brown D. Examination of Orthopedic & Athletic Injuries, 4th ed. Philadelphia, PA: F. A. Davis Company, 2015, p. 603, with permission.)


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