The anterior deltoid is the clavicular head of the deltoid muscle, providing the primary force for shoulder flexion and horizontal adduction. It is the largest contributor to the bench press movement and is heavily recruited during pushing activities. In shoulder replacement surgery, the anterior deltoid must be carefully preserved and reattached to prevent the anterior deltoid detachment that compromises shoulder function after arthroplasty. It is also the preferred site for vaccine administration in adults.
| Origin | Anterior border and superior surface of the lateral third of the clavicle |
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| Insertion | Deltoid tuberosity of the humerus alongside the middle and posterior fibres |
| Nerve Supply | Axillary nerve (C5, C6) |
| Blood Supply | Anterior circumflex humeral artery |
| Actions | Flexion of the arm; Internal rotation of the arm; Horizontal adduction of the arm; Assists in arm abduction in the scapular plane |
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During reaching forward the anterior deltoid accelerates the arm into flexion while the rotator cuff depresses the humeral head to prevent superior migration. Anterior deltoid overactivity combined with rotator cuff weakness creates the anterior superior impingement pattern.
Anterior deltoid injection technique for vaccines requires targeting the thickest part of the muscle belly in the lateral upper arm, avoiding the deltoid tuberosity below and the axillary nerve which crosses the deltoid at the level of the surgical neck of the humerus. Incorrect vaccination technique with medial placement causes shoulder injury related to vaccine administration (SIRVA) from injection into the subacromial bursa.
The anterior deltoid muscle belly is the rounded mass on the anterior shoulder, clearly palpable and often visible during resisted shoulder flexion and horizontal adduction.
Shoulder injury related to vaccine administration from injection too high or too medial placing the vaccine into the subacromial bursa rather than the deltoid muscle, producing inflammatory shoulder pain managed with corticosteroid injection.
