The subclavius is a small muscle tucked between the first rib and the clavicle, depressing the clavicle and acting as a shock absorber protecting the subclavian vessels from clavicular fracture fragment injury. In midshaft clavicle fractures the subclavius is the muscle between the fracture fragments and the subclavian artery — its preservation as an intact soft tissue layer prevents catastrophic vascular injury in most cases.
| Origin | Junction of the first rib and its costal cartilage |
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| Insertion | Inferior groove on the middle third of the clavicle |
| Nerve Supply | Nerve to subclavius (C5, C6) from the upper trunk of the brachial plexus |
| Blood Supply | Clavicular branch of the thoracoacromial artery |
| Actions | Depresses and anchors the clavicle at the sternoclavicular joint; Protects the underlying subclavian vessels from clavicular fracture fragments |
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Subclavius serves a protective role in clavicle fractures — between the inferior clavicular cortex and the subclavian artery. In grossly displaced clavicle fractures the subclavius may be torn, increasing vascular risk. Subclavius transfer (subclavius transfer to the distal clavicle) has been described for AC joint reconstruction but is rarely used clinically.
The subclavius is not palpable on surface examination due to its position deep to the clavicle and pectoralis major.
Subclavius acts as a protective buffer between displaced clavicle fracture fragments and the subclavian artery — its integrity reduces risk of vascular injury.
