The clavicle, or collarbone, connects the upper limb to the trunk. It is classed as a long bone, but is relatively short, attaching medially to the sternum, and laterally articulating with the acromion of the scapula.
It can be palpated along its length, and is visible under the skin in many people.
This article is about the anatomy of the clavicle, bony landmarks, and the clinical scenarios that result from injury or malformation.
The bony prominences of the clavicle are found on the inferior surface of the bone. They are enlarged, roughened areas of the bone, acting as attachment sites for ligaments.
The conoid tubercle is found near the acromial end of the clavicle. It is the attachment point of the conoid ligament - the medial part of the coracoclavicular ligament.
Also near the acromial end of the sternum is the trapezoid line. It is where the trapezoid ligament (the lateral part of the coracoclavicular ligament) attaches.
At the sternal end of the clavicle is the impression for costclavicular ligament. it is a rough oval depression that the costoclavicular ligament binds to.
The clavicle has three main functions
- Attaches the upper limb to the trunk.
- Protects the underlying neurovascular structures supplying the upper limb.
- Transmits force from the upper limb to the axial skeleton.
Clinical Relevance: Fracture of the Clavicle
One of the functions of the clavicle is to transmit forces from the upper limb to the axial skeleton. This makes it the most commonly fractured bone in the body. Fractures commonly result from a fall onto the shoulder, or onto an outstretched hand.
The most common point of fracture is the junction of the medial 2/3 and lateral 1/3.
After fracture, the lateral end of the clavicle is displaced inferiorly by the weight of the arm, and medially, by the pectoralis major. The medial end is pulled superiorly, by the sternocleidomastoid muscle.
The suprascapular nerves (medial, intermedial and lateral) may be damaged by the upwards movement of the medial part of the fracture. These nerves innervate the lateral rotators of the upper limb at the shoulder – so damage results in unopposed medial rotation of the upper limb – the ‘waiters tip’ position.