The shoulder girdle attaches the free upper extremity (arm) to the trunk. The scapula has no direct or indirect connection with its counterpart of the opposite side. It is only indirectly attached to the trunk by means of the clavicle that closes the girdle ventrally (in front). The girdle remains open dorsally (in back) and is freely movable.

The Scapula

The scapula, or shoulder blade, is a large, flat, triangular-shaped bone with several marked processes. It is situated on the dorsal aspect of the thorax and is attached by muscles only. It lies between the levels of the second and seventh ribs with its vertebral border about two inches lateral to the vertebral column. In thin subjects, it can be easily palpated. It has two surfaces, three borders, and three angles which can be recognized.

The anterior surface of the scapula is directed toward the ribs and is comparatively smooth. It is marked by a concave and somewhat shallow depression, termed the subscapular fossa. The posterior surface is slightly convex and is divided into two unequal areas by a narrow ridge or crest of bone called the spine. The spine of the scapula terminates laterally in a large triangular projection, the acromion process, which forms the tip of the shoulder and can be felt through the skin. The portion of the posterior surface above the spine is called the supraspinous fossa; and below it, the infraspinous fossa.

The three borders are designated as the vertebral, the axillary, and the superior. The vertebral border is approximately parallel to the vertebral column. The upper (superior) border is the shortest and is thin and sharp. At its lateral end, there is a depression, the scapular notch, and a thick beaklike projection, the coracoid process. The coracoid process curls forward beneath the clavicle and can be palpated in a depression on the thorax (the infraclavicular fossa). Frequently, in thin subjects, it may form a rather prominent projection. The axillary border is the thickest and lies close to the armpit, or axilla.

The three angles are designated medial, inferior, and lateral.

1. The medial angle is formed by the junction of the superior and vertebral borders.
2. The inferior angle is formed by the union of the vertebral and axillary borders.
3. The lateral angle, formed by the junction of the superior and axillary borders, is the thickest part of the bone and is sometimes called the head of the scapula. The head presents a smooth, slightly depressed, articular surface, the glenoid fossa or cavity, which accommodates the head of the humerus. The glenoid lip is a fibrocartilaginous rim attached around the margin of the glenoid cavity. The head is separated from the main portion (body) of the bone by a thickened, slightly constricted part, called the neck.

The Clavicle

The clavicle or collarbone is a long, slender

S-shaped bone with a middle portion, the shaft or body, and two extremities. The sternal extremity is rounded. The acromial extremity is flat. The shaft, or body, has two surfaces, a superior and an inferior, separated by anterior and posterior borders. The medial two-thirds of the anterior border presents a convexity and the lateral one-third presents a concavity. The superior surface is comparatively smooth and can be easily palpated. Near its sternal end, a broad, roughened area called the costal tuberosity marks the inferior surface. Laterally, near the posterior border is a well-marked roughened eminence, the coronoid tubercle.

NOTE: The terms “tubercle” and “tuberosity” are used interchangeably

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