The Clavicle

Fig 1.0 - The anatomical position of the clavicle

Fig 1.0 – The anatomical position of the clavicle

The clavicle (collarbone) extends between the sternum and the acromion of the scapula.

It is classed as a long bone, and can be palpated along its length. In thin individuals, it is visible under the skin. 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.

In this article, we shall look at the anatomy of the clavicle – its bony landmarks and clinical correlations.


Bony Landmarks

The clavicle is a slender bone with an ‘S’ shape. Facing forward, the medial aspect is convex, and the lateral aspect concave. It can be divided into a sternal end, a shaft and an acromial end.

Sternal (medial) End

The sternal end contains a large facet – for articulation with the manubrium of the sternum at the sternoclavicular joint.

The inferior surface of the sternal end is marked by a rough oval depression for the costoclavicular ligament (a ligament of the SC joint).

Shaft

The shaft of the clavicle acts a point of origin and attachment for several muscles – deltoid, trapezuis, subclavius, pectoralis major, sternocleidomastoid and sternohyoid

Acromial (lateral) End

The acromial end houses a small facet for articulation with the acromion of the scapula at the acromioclaviclar joint. It also serves as an attachment point for two ligaments:

  • Conoid tubercle – attachment point of the conoid ligament, the medial part of the coracoclavicular ligament.
  • Trapezoid line –  attachment point of the trapezoid ligament, the lateral part of the coracoclavicular ligament.

The coracoclavicular ligament is a very strong structure, effectively suspending the weight of the upper limb from the clavicle.

Fig 1.1 - Bony landmarks of the inferior surface of the clavicle.

Fig 1.1 – Bony landmarks of the inferior surface of the clavicle.

Clinical Relevance: Fracture of the Clavicle

A function of the clavicle is to transmit forces from the upper limb to the axial skeleton. Thus, the clavicle is 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.

Fig 1.2 - X-Ray of a clavicular fracture. Note how the medial end is raised and the lateral end lowered

Fig 1.2 – X-Ray of a clavicular fracture. Note how the medial end is raised and the lateral end lowered.

Quiz

Which of the following is not a function of the clavicle?
Attaches upper limb to trunk
Protects underlying neurovascular structures
Transmits force from the upper limb to the axial skeleton
Movement on flexion of the shoulder

Quiz

What attaches to the clavicle at the conoid tubercle?
Conoid ligament
Trapezoid ligament
Pectoralis major
Sternocleidomastoid

Quiz

What attaches to the clavicle at the trapezoid line?
Conoid ligament
Trapezoid ligament
Pectoralis major
Sternocleidomastoid

Quiz

What is the most common point of fracture of the clavicle?
Acromial end
Sternal end
Junction between the medial 2/3 and lateral 1/3
Junction between the medial 1/3 and lateral 2/3

Quiz

Which nerve can be damaged in a clavicular fracture?
Median nerve
Suprascapular nerves
Axillary nerve
Accessory nerve

 

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