The Clavicle is a long bone having a prismatic shaft, and at its inner (sternal) end a rounded head; while its outer (acromial) end is flattened into a more or less square shape. The shaft forms a double curve, being convex forwards internally and convex backwards externally; the upper surface, subcutaneous throughout, is rounded and smooth; the anterior border is rough, internally for the attachment of the pectoralis major, and externally for that of the deltoid; the posterior border is roughened internally for the attachment of the sterno-mastoid, and externally, where the acromion process begins, there is a tubercle, called the conoid tubercle, for the attachment of the conoid ligament. The inferior surface is also rough; at its sternal end there is a deep pit for the attachment of the rhomboid ligament, and in its middle third a groove for the subclavian muscle; from the conoid tubercle, outwards and forwards, proceeds an oblique ridge for the attachment of the trapezoid ligament.

Fig. 1. - The Right Clavicle (Superior View).

The clavicle articulates internally with the upper end of the sternum, and externally with the acromion process of the scapula.

Ossification

The clavicle is the first bone of the body to ossify, the process commencing in the shaft very early in foetal life. The secondary centre, or epiphysis, appears at the sternal end in adult life, and ossification is complete about the twenty-fifth year.

Sterno-Clavicular Joint

Sterno-Clavicular Joint, between the sternal end of the clavicle and the outer part of the upper edge of the sternum. A gliding joint, so only gliding movements possible. There are no movements round a distinct axis, but movements which depress or raise the scapula will cause the clavicle to move also, in both its joints.