Agenesis of the Serratus Anterior Muscle: A Cause of Winged Scapula

To the Editor.— We recently performed an exploratory thoracotomy on a 64-year-old man with bronchogenic carcinoma of the left upper lobe. Preoperatively, he was noted to have a "winged" scapula on the affected side, an abnormality existing as far back as he could remember. The cause of his deformity became obvious, when in the course of making the operative incision, a total absence of the serratus anterior was discovered. The serratus anterior muscle arises from the outer surfaces of the upper eight or nine ribs and inserts along the medial aspect of the scapula on its costal surface. Its major function is to draw the scapula forward, especially its inferior angle, thereby allowing upward rotation of the scapula, necessary for full arm abduction. It also holds the medial border of the scapula against the thoracic cage. Any paralysis of the muscle results in "winging." The muscle is supplied by the