Serratus anterior is the key muscle holding the scapula against the thorax and rotating it upward for arm elevation. Long thoracic nerve palsy produces the classic lateral scapular winging — the medial border and inferior angle lift away from the thorax when the patient presses against a wall. Without upward rotation, full shoulder elevation is impossible.
| Origin | Outer surfaces of ribs 1-8 (or 1-9) as digitations interleaving with the external oblique origin |
|---|---|
| Insertion | Entire medial border and inferior angle of the scapula (costal surface) |
| Nerve Supply | Long thoracic nerve (C5, C6, C7) |
| Blood Supply | Lateral thoracic artery and thoracodorsal artery perforators |
| Actions | Protracts the scapula (major function); Holds the medial scapular border against the thorax; Rotates the glenoid upward (working with the trapezius in overhead elevation) |
|---|
Serratus anterior and lower trapezius form the upward rotation force couple at the scapula — both must be active for normal scapulohumeral rhythm. Serratus anterior also provides the 'punch' of boxing by protacting the scapula to extend reach.
Long thoracic nerve injury from heavy backpack pressure, direct blow to the lateral chest, or viral neuritis produces serratus anterior palsy. Recovery is usually spontaneous over 12-24 months. Eden-Lange transfer (levator scapulae and rhomboid major to the lateral scapular border) provides surgical stabilisation for persistent winging causing significant disability.
Serratus anterior is palpable on the lateral chest wall below the axilla as the finger-like digitations along the ribs, becoming prominent during push-up or forward reaching.
Serratus anterior paralysis producing lateral winging managed with physiotherapy for 12-24 months before Eden-Lange transfer for persistent disability.
