The clavicular head of the pectoralis major is the upper portion of the fan-shaped pectoral muscle, providing the primary force for arm flexion and horizontal adduction from the anterior position. It is separately innervated by the lateral pectoral nerve (C5, C6) and can act somewhat independently from the sternocostal head. In body builders, the clavicular head is the most visible and sought-after portion of the pectoral muscle, forming the upper chest definition.
| Origin | Anterior surface of the medial half of the clavicle |
|---|---|
| Insertion | Lateral lip of the bicipital groove of the humerus, with the clavicular fibres inserting most inferiorly in a folded arrangement |
| Nerve Supply | Lateral pectoral nerve (C5, C6) |
| Blood Supply | Pectoral branch of the thoracoacromial artery |
| Actions | Flexion of the arm at the shoulder; Horizontal adduction of the arm; Internal rotation of the arm |
|---|
At low shoulder flexion angles the clavicular head is the primary horizontal adductor, with the sternocostal head contributing more at mid-range adduction. The folded insertion on the bicipital groove places the clavicular fibres on the deep surface of the sternocostal fibres, a curious arrangement that reverses their apparent origin-to-insertion direction at the humerus.
Clavicular head pectoralis major tears are less common than sternocostal head tears and typically produce a slightly different deformity pattern — less medial muscle roll, more superior defect. Distinction from sternocostal head tears by MRI guides surgical repair decisions. The clavicular head is the portion at risk during anterior shoulder arthroplasty approaches that split the deltopectoral interval adjacent to the clavicular origin.
The clavicular head is palpable as the upper border of the pectoral muscle between the anterior deltoid and the sternocostal head during resisted shoulder flexion and horizontal adduction.
Upper pectoral tear producing shoulder flexion weakness and a visible upper chest defect, managed surgically for complete tears in active individuals.
