Subclavius muscle

Origin and insertion

The subclavius muscle originates by a strong tendon from the sternal end of the 1st rib, near its articulation with the costal cartilage. The tendon spreads superolaterally into a muscle belly that inserts into the lower surface of the middle third of the body of clavicle (groove for subclavius muscle). 

The subclavius is enclosed by the clavipectoral fascia, which is a fibrous connective tissue that spans the interval between the clavicle and pectoralis minor muscle. The pectoralis major muscle courses superficial to the subclavius and clavipectoral fascia. The brachial plexus, suprascapular artery, subclavian artery and subclavian vein pass deep to the subclavius muscle.

Innervation

The subclavius is innervated by the subclavian nerve (C5-6), a small branch that arises from the superior trunk of brachial plexus.

Blood supply

The subclavius muscle receives arterial blood from the clavicular branch of thoracoacromial artery, with contributions from the suprascapular artery.

Function

The main function of the subclavius muscle is the active stabilization of the clavicle at the sternoclavicular joint during movements of the shoulder and arm. Furthermore, its contraction leads to a depression of the sternal end of the clavicle and subsequent elevation of the first rib. This movement is rather insignificant, but still helps to prevent dislocation of the clavicle at the sternoclavicular joint during certain types of activity.

Additionally, the subclavius is important to prevent injury of the adjacent subclavian blood vessels and the superior trunk of the brachial plexus in case of a fractured clavicle.

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