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BONES OF THE SHOULDER AND ARM

BIG PICTURE

The bones of the skeleton provide a framework to which muscles, tendons, and ligaments attach. The bony structure of the shoulder and arm consists of the clavicle, scapula, and humerus (Figure 29-1A). Synovial joints and ligaments connect bone to bone.

Figure 29-1:

A. Osteology of the upper limb (right side). Superior (B) and anterior (C) views of the clavicle. Anterior (D) and posterior (E) views of the scapula. Anterior (F) and posterior (G) views of the humerus.

CLAVICLE

The clavicle, or collarbone, is the only bony attachment between the upper limb and the axial skeleton (Figure 29-1B and C). It is superficial along its entire length and shaped like an “S.” The clavicle provides an attachment for muscles that connect the clavicle to the trunk and the upper limb. The following landmarks are found on the clavicle:

  • Acromial end. Articulates laterally with the acromion of the scapula and forms the acromioclavicular joint.

  • Sternal end. Articulates medially with the manubrium and forms the sternoclavicular joint.

  • Conoid tubercle. Located on the inferior surface of the lateral clavicle and serves as an attachment for the coracoclavicular ligament.

SCAPULA

The scapula, or shoulder blade, is a large, flat triangular bone with two angles (superior and inferior), three borders (superior, lateral, and medial), two surfaces (costal and posterior), and three processes (acromion, spine, and coracoid) (Figure 29-1D and E). The following landmarks are found on the scapula:

  • Subscapular fossa. Located anteriorly and characterized by a shallow, concave fossa. Because the subscapular fossa glides upon the ribs, it is also known as the costal surface. Serves as an attachment for the subscapularis muscle.

  • Acromion. A large projection of the anterolateral surface of the spine; the acromion arches over the glenohumeral joint and articulates with the clavicle.

  • Spine. Very prominent and palpable; the spine subdivides the posterior surface of the scapula into a small supraspinous fossa and a larger infraspinous fossa. Serves as an attachment for the trapezius and deltoid muscles.

  • Supraspinous fossa. Located on the posterior surface of the scapula and superior to the spine of the scapula. Serves as an attachment for the supraspinatus muscle.

  • Infraspinous fossa. Located on the posterior surface of the scapula and inferior to the spine of the scapula. Serves as an attachment for the infraspinatus muscle.

  • Suprascapular notch. A small notch medial to the root of the coracoid process where the suprascapular nerve courses. The superior transverse scapular ligament converts the suprascapular notch into a foramen.

  • Glenoid cavity (fossa). A shallow cavity that articulates with the head of the humerus to form the glenohumeral joint...

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