Depressor Anguli Oris Flap


The depressor anguli oris flap is a full-thickness musculocutaneous flap that provides functional (both sensory and motor) lower lip and oral sphincter reconstruction (40). Flap dimensions reflect the size of the underlying depressor muscle and are approximately 4 cm long by 2 cm wide. The vascular pedicle is the inferior labial artery off the facial artery entering the flap near the oral commissure. Sensation is derived from the mental nerve (trigeminal) and the motor innervation is from the marginal branch of the facial nerve. These two nerves are dissected independent of the vascular pedicle and are sufficiently released to allow transposition of the flap. The flap is based c superiorly with its medial border originating at the modiolus. It extends inferiorly along the buccolabial fold (marionette line) encompassing the underlying depressor anguli oris muscle. The layers of the flap include skin, depressor anguli oris muscle, and mucosa. Harvesting additional tissue laterally from the labial-gingival sulcus o can enlarge the mucosal component. The flap pivots into position, bringing the depressor anguli oris muscle into the same orientation as the lost orbicularis oris muscle. The facial artery must occasionally be divided near the inferior aspect of the flap to allow transposition. Mucosal advancement or a ventral tongue flap reconstitutes the vermilion border.


The depressor anguli oris flap is most favorable for lateral ipsilateral defects involving up to 60% of the lower lip (Fig. 23). Total lower lip reconstruction can be accomplished with bilateral flaps.


The upper lip and modioli are undisturbed and the full length of the lower lip is reconstructed, minimizing the problem of postoperative microstomia. The principal advantages to this method are recreation of a sensate lower lip with sufficient motor activity to recreate a functional oral sphincter, avoidance of microstomia, preservation of upper lip structure and function, and provision of all lip elements by a single flap.


A functional donor deficit of commissure depression is evident in scowling. The commissure also rises excessively during smiling as a consequence of the unopposed action of the lip elevators.

Commissure Lip Reconstruction
Figure 23 The depressor anguli oris flap for dynamic and sensate repair of a lower lip defect (see text).
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