The clavicle (from Latin clavès, “small key”) is a bone in the upper part of the thorax, located between the top of the breastbone and the top of the shoulder. It is involved in the shoulder joint.

The clavicle is a bone of the upper limb, it articulates inwardly with the sternum and outwardly with the acromion (protuberance of the scapula – formerly scapula). It is a short, elongated S-shaped bone (the first convexity of the S is forward and the second is back). It is palpable under the skin. Associated with the scapula, it forms the scapular (or pectoral) girdle which attaches the upper limbs to the skeleton.

Several muscles are inserted at the level of the clavicle.

On its upper face, four muscles fit into different areas:

• The pectoralis major muscle,
• The deltoid muscle,
• The trapezius muscle,
• The sternocleidomastoid muscle.

On its underside, is inserted:

• Le muscle subclavier,
• The conoid and trapezoid ligaments,
• The costo-clavicular ligament that unites the clavicle to the first rib.

The clavicle is located in the path of large blood vessels and nerves that go to the upper limb passing under its inner third.

The clavicle, being connected with the acromion of the scapula, participates in the shoulder joint. It keeps the arm away from the upper part of the thorax. This position helps to counter dislocation of the shoulder.

Clavicle fracture : the superficial position of the clavicle makes it one of the most frequent fracture sites (10% of fractures) (,) especially in children and young adults. In the majority of cases (75%), it is fractured in its middle third. It usually occurs during a fall on the shoulder or violent sports contact (eg rugby).

dislocation :

• Acromioclavicular: dislocation of the joint that joins the clavicle to the acromion. Frequent pathology that usually occurs in sports accidents and traffic accidents.
• Sternoclavicular: dislocation of the joint between the clavicle and the sternum, it is four times less frequent than the acromioclavicular.

Sternocostoclavicular hyperostosis : rare pathology of unknown cause, it results in hypertrophy and condensation of the sternum, collarbones and first ribs. It preferentially affects the middle-aged man. The main symptom is painful swelling in the breastbone.

Tumors of the clavicle : Bone tumors of the chest wall can very rarely localize on the collarbone or the sternum.

Canal syndrome of the costo-clavicular clamp: compression of the nerves in the root of the arm (the brachial plexus) and / or vessels in the collarbone. There are different causes: most often, this compression is related to the posture with a horizontalization of the clavicles, or more rarely, to the presence of a supernumerary rib. The clinical signs are very varied: fatigue, heaviness, numbness and / or tingling of the upper limb, coldness of the hand, swelling, phlebitis of a limb and in the most serious cases, Raynaud’s syndrome.

Pathologies of the clavicle essentially have traumatic causes which are difficult to prevent.

Nevertheless, it is advisable to consume foods rich in calcium and vitamin D in order to strengthen the bones and reduce the risk of fractures (11).

Physical examination : carried out by the doctor, it first includes the questioning (general, on the causes of the accident). It is followed by the physical examination of the clavicle: inspection and palpation (displacement of the shoulder, deformation of the angle in relation to the clavicle, bony protrusion under the skin, mobility of the shoulder joint rarely possible. because too painful).

Radiography: a medical imaging technique that uses x-rays. A standard reference examination, a frontal x-ray of the collarbone confirms the diagnosis of a fracture. It also makes it possible to check the condition of adjacent bone and joint structures.

In the case of the canal syndrome of the costo-clavicular clamp, it makes it possible to highlight a deformation of the clavicle which would be at the origin of the compression.

In the fetus, the clavicle is the first bone to begin ossification (formation of bone structure) from the 30th day in utero and the last to complete it at the age of 25 years.

In Greek mythology, it is by attacking at the level of the collarbone and the shoulder, the only part of the body not protected by his armor, that Achilles manages to kill Hector after he has killed his cousin Patroclus.

In birds, the two collarbones are fused and form the bone of the furcula. This fusion is adapted to the flight function. It is in particular this bone that we break to bring good luck when we eat a chicken. Since birds are descendants of certain dinosaurs, this furcula bone is found in particular in tyrannosaurs (12).