The serratus anterior muscle arises as eight digitations from the upper eight ribs. The first digitation is the largest, and it inserts into the upper costal surface of the vertebral border of the scapula. The next three digitations insert into the whole of the vertebral border, and the lower four digitations insert into the scapular angle. Denervation or removal of the lower four digitations does not produce winging of the scapula if the upper four digitations are intact.

The long thoracic nerve is not at risk during surgery because the supply to the upper four digitations of the serratus anterior lie slightly deeper on the chest wall, separated from the vascular pedicle of the flap by a definite fascial layer.

The upper four digitations are supplied mainly by branches of the lateral thoracic artery. The lower four digitations are supplied by a single branch (72%), two branches (24%), and multiple branches (4%) of the thoracodorsal pedicle as well as the lateral thoracic and intercostal vessels (1). The branch(es) pierces the fascia over the serratus anterior superficial to the nerve supply (approximately in the midaxillary line) and runs with it to the lower four digitations. The vascular and nerve supplies to the latissimus dorsi muscle have been described in detail elsewhere (2, 3, 4).