Clavicle

Key Features & Anatomical Relations

The clavicle (or collar bone) is one of the two bones that form the pectoral girdle, the other being the scapula. It’s classified as a long bone and includes the following bony features:

- parts: acromial end, body, and sternal end;

- surfaces: superior and inferior surfaces, and anterior and posterior borders;

- landmarks: conoid tubercle, trapezoid line, groove for subclavius muscle, impression for costoclavicular ligament, and sternal and acromial facets.

More information regarding these and other bony features can be found in the Parts, Surfaces and Landmarks tabs for this bone.

The clavicle is located:

- anterior to the subclavian vessels and the brachial plexus;

- superior to the first rib, its costal cartilage, and the subclavius muscle;

- medial to the acromion of the scapula;

- lateral to the manubrium of sternum.

It articulates with the:

- scapula at the acromioclavicular joint;

- manubrium of sternum at the sternoclavicular joint.

The clavicle contributes to the formation of the:

- jugular notch;

- infraclavicular fossa, where the clavicle forms its superior boundary.

Ossification

Ossification of the clavicle occurs at three ossification centers, these are found in the:

- body of the clavicle, two centers are located here and appear in utero during weeks five to six, making the clavicle the first bone to ossify;

- sternal end of the clavicle, which appears during late adolescence.

These ossification centers fuse with each other by the twenty-third year, making the clavicle the last bone to complete ossification (Standring, 2016).

Variations

In males, the clavicle is generally longer, thicker, and more curved than in females. Furthermore, the acromial end of the clavicle is positioned superior to the sternal end in males, while the opposite is usually observed in females.

The left clavicle is often longer and weaker than the right clavicle and, in some individuals, the clavicle is pierced by a branch of the supraclavicular nerve.

Surface Anatomy

The following bony features of the clavicle are relevant to surface anatomy:

- the superior surface and anterior border of the clavicle are subcutaneous, making the clavicle easily palpable along its entire length;

- the sternal ends of both the right and left clavicles contribute to the formation of the jugular notch;

- the acromial end of the clavicle usually rises higher than the acromion of the scapula, therefore marking the location of the acromioclavicular joint.

List of Clinical Correlates

- Fracture of clavicle (most commonly fractured bone)

- Cleidocranial dysotosis/cleidocranial dysplasia

- Dislocation of sternoclavicular joint

- Dislocation of acromioclavicular joint

References

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.