Clavicle of right side viewed from below (left image) and from above(right image)
The clavicle is a long bone that connects trunk with upper limb.
It is also known as collar bone.
Its main function is support of the shoulder and transmittal of upper limb weight to the trunk through the sternum.
Clavicle can be divided into a cylindrical part called the shaft, and two ends – medial and lateral.
The lateral end is also called acromial end and is flat from above downwards. It articulates with the acromion process of the scapula through a facet. The articular surface for the acromioclavicualr joint gives attachment to the joint capsule.
The medial end is called sternal end, is quadrangular in shape. This part articulates with the clavicular notch of the manubrium sterni to form the sternoclavicular joint. It also articulates with first costal cartilage via extension of the articular surface. The articular surface for the sternum gives attachement to the fibrous capsule all round, to the articular disc posterosuperiroly; and to the interclavicular ligament superiorly.
The shaft of the clavicle can be divided into the lateral one third and the medial two thirds.
The lateral one third of the shaft is flattened from above downwards. It has two borders, anterior which is concave anteriorly and posterior which is convex posteriorly. Between the two borders are two surfaces- the superior surface and inferior surface. While the superior surface is subcutaneous, the inferior surface has elevation called the conoid tubercle and a ridge called the trapezoid ridge.The anterior border gives origin to the deltoid muscle and the posterior border provides insertion to the trapezius muscle. The conoid tubercule andtrapezoid ridge give attachment to the conoid and trapezoid parts of the coracoclavicular ligament.
The medial two thirds of the shaft of the clavicle is rounded and has four surfaces.
- The anterior surface- It is convex forwards.
- The posterior surface- It is thickened and smooth.
- The superior surface- This surface iss rough in its medial part.
- The inferior surface- It has a rough oval impression at the medial end. It harbors a longtitudinal groove called subclavian groove in its lateral half.
The anterior surface gives origin to the pectoralis major. The rough superior surface gives origin to the clavicular head of the sternocleidomastoid. The oval impression on the inferior surface gives attachment to the costoclavicular ligament. The subclavian groove gives insertion to the subclavius muscle and the margins of the groove give attachment to the clavipectoral fascia.
Determination of Side.
- The lateral end is flat, and the medial end is large and quadrilateral.
- The shaft is slightly curved, so that it is convex forwards in its medial 2/3, and concave forwards in its lateral 1/3.
- The inferior surface is grooved longitudinally in its middle 1/3.
Female clavicle is shorter, lighter, thinner, smoother, and less curved than in males . The lateral end of the clavicle is a little below the medial end in females whereas In males, the lateral end is either at the same level or slightly higher than the medial end.
Text adapted from BD chaurasia