Shoulder p2

• The shoulder region is a complex of 20 muscles, three bony articulations, and three soft tissue moving surfaces (functional joints) that permit the greatest mobility of any joint area found in the body.
• The primary purpose of the shoulder is to put the hand in a position for function.
• The shoulder is able to place the hand in about 16,000 different positions,1 thereby allowing the hand to produce myriad functions that we usually take for granted.
• The shoulder complex not only provides a wide range of positions for hand placement, but it also stabilizes the upper extremity for hand motions, lifts and pushes objects, elevates the body, assists with forced respiratory inspirations and expirations, and even bears weight when walking with crutches or performing handstands.
• Mobility, however, is at the expense of structural stability.
• The only bony attachment of the upper extremity to the trunk is at the sternoclavicular joint.
• Thus, support and stabilization of the shoulder are primarily dependent on muscles and ligaments.
• Muscles acting on this complex structure do not act alone but rather in concert with other muscles to provide for its smooth function.
• If ligaments become disrupted or muscles are unable to provide their normal function, normal motion within the shoulder complex is lost and the upper limb’s efficiency is hampered.
• When we speak of the shoulder complex, we include all of the structures that provide upper limb movement at this most proximal upper extremity joint.
• The entire shoulder complex is held to the axial skeleton by a combination of the bony attachment between the sternum (manubrium) and clavicle and the muscles originating from the axial skeleton and attaching to the bony shoulder complex structures.
• The bones connecting the shoulder complex to the axial skeleton are the manubrium (of the axial skeleton) and the clavicle (of the shoulder complex).
• The manubrium, along with the left and right clavicles and scapulae, form an incomplete girdle.
• The structure, often referred to as the shoulder girdle, is incomplete since a true girdle completely surrounds a structure.
• The bony structures of the shoulder complex include the sternum, clavicle, scapula, and humerus; the joints make up the connections between each of these bones; and the soft tissue connection between the scapula and the thorax.
• When discussing the shoulder joint, reference is made to only the glenohumeral joint: the humerus and scapula as they form the shoulder joint and the soft tissue structures that surround this joint.
• The term “shoulder joint” is often used incorrectly to refer to the entire shoulder complex.
• Each of the elements included in the shoulder complex are presented and discussed in this chapter.
• The entire shoulder complex is held to the axial skeleton by a combination of the bony attachment between the sternum (manubrium) and clavicle and the muscles originating from the axial skeleton and attaching to the bony shoulder complex structures.
• The bony structures of the shoulder complex include the sternum, clavicle, scapula, and humerus; the joints make up the connections between each of these bones; and the soft tissue connection between the scapula and the thorax.
• The bones connecting the shoulder complex to the axial skeleton are the manubrium (of the axial skeleton) and the clavicle (of the shoulder complex).
• The superior aspect of the manubrium contains a shallow depression for the medial clavic- ular attachments.
• Sitting between the two clavicular facets on the manubrium is the sternal or jugular notch, a prominent con- cavity that is easily palpated.
• On the lateral aspects of the manubrium immediately adjacent and inferior to the clavicular facets are the slightly concave facets for attachment of the first ribs.
• The clavicle (L

  clavicula, diminutive of clavus, key) is S-shaped, like a crank, with its forward convexity at its sternal end to clear the brachial plexus and upper extremity vascular bundle and its forward concavity at the humeral end.
• In the anatom- ical position, the long axis of the clavicle is slightly above the horizontal plane,resting 20° to the frontal plane.
• The acromial end of the clavicle, like the sternal end, is enlarged and is palpated as a protuberance.
• The scapula (L scapula, shoulder blade) is a flat, triangular-shaped bone with three sides and three angles that sits against the posterior thorax.
• Animals that stand and run in a quadruped position, such as horses and dogs, do not have clavicles, and their scapulae are on the lateral surfaces of the thorax.
• In an anatomical resting position, the medial vertebral border of the scapula is approximately 5 to 6 centimeters, or two to three finger-widths, from the thoracic spinous processes and between thoracic levels 2 (T2) and 7 (T7).
• Bipedal humans have a strong, well-developed clavicle that acts as a lateral strut to the scapula and the humerus, increasing glenohumeral mobility to permit greater motion in reaching and climbing activities.
• The scapula has a dual function: to provide a place for muscles controlling the glenohumeral joint to venture from and to provide a stable base from which the glenohumeral joint can function.
• The scapula (L scapula, shoulder blade) is a flat, triangular-shaped bone with three sides and three angles that sits against the posterior thorax.
• The inferior angle of the scapula where the vertebral border and lateral border meet is palpated by following the vertebral border distally.
• The lateral axillary border of the scapula angles upward and laterally from the inferior angle toward the glenoid fossa.
• In an anatomical resting position, the medial vertebral border of the scapula is approximately 5 to 6 centimeters, or two to three finger-widths, from the thoracic spinous processes and between thoracic levels 2 (T2) and 7 (T7).
• The glenoid fossa is the superior lateral aspect of the scapula that forms the concave portion of the glenohumeral joint.
• The scapula has a dual function: to provide a place for muscles controlling the glenohumeral joint to venture from and to provide a stable base from which the glenohumeral joint can function.
• The superior border of the scapula is difficult to palpate but lies essentially parallel to the spine of the scapula.
• The inferior angle of the scapula where the vertebral border and lateral border meet is palpated by following the vertebral border distally.