Functional Lower Lip and Oral Sphincter Reconstruction With Innervated Depressor Anguli Oris Flaps

G. R. TOBIN

EDITORIAL COMMENT

The objective of the procedure, which is to restore the oral sphincter with innervated muscle, is correct. In practice, the technique is cumbersome, because in most cases simple reapproximation of the remnants of the orbicularis muscle may suffice. Further experience with this flap, particularly applicable to postcancer patients, demonstrates that the flap can be extended down along the so-called jowls below the horizontal ramus of the mandible. This is most helpful in reconstructing the upper portion of the lower lip, providing sufficient height with good sphincter restoration.

The innervated depressor anguli oris (DAO) musculocutaneous-mucosal flap is a compound flap that provides functional lower lip and oral sphincter reconstruction with all the necessary components: skin cover, mucosal lining, vermilion, oral sphincter, and sensation.

INDICATIONS

Depressor anguli oris flaps reconstruct sensate lips and functional oral sphincters of normal dimensions in one operation without invading or denervating the upper lip. All previously described methods of lower lip reconstruction suffer from one or more of the following disadvantages:

Partial sacrifice or denervation of the upper lip and its orbicularis oris sphincter
Transection of the orbicularis oris sphincter lateral to the oral commissure
Obliteration of the oral commissure
Microstomia

Lip-switch flaps (1, 2) sacrifice upper lip and transect its orbicularis oris sphincter, denervate the orbicularis oris medial to the donor site, fail to restore oral circumference, and produce denervated reconstructions (although partial reinnervation subsequently occurs (3)). Inferiorly based nasolabial flaps (4) denervate the upper lip and produce partially or totally denervated reconstructions. They also destroy functional orbicularis oris around the commissure. Inferior pedicle cheek transposition flaps (5) transect the orbicularis oris at the commissure and fail to reconstruct the lower lip sphincter or provide sensation. Lateral advancement cheek flaps (6, 7, 8, 9) denervate the upper lip, transect the orbicularis oris muscle at the commissure, and fail to reconstruct the lower lip sphincter. The myoplastic modification of the Bernard method (10) overcomes some of these disadvantages by preserving upper lip innervation and by avoiding transection of orbicularis oris at the commissure when short advancements are done for small defects. Microstomia and obliteration of the oral commissure occur with Estlander, “fan” (11, 12), and Karapandžić (13) flaps; however, the Karapandžić method is the only technique that reconstructs the oral sphincter and preserves motor and sensory innervation to the extent of depressor anguli oris reconstructions.

One depressor anguli oris flap reconstructs over half of a lower lip (Figs. 171.1 and 171.2), and bilateral depressor anguli oris flaps reconstruct an entire lower lip of normal length (Fig. 171.3). The principal advantages of this technique are (a) reconstructed lips with normal sensation and functional oral sphincters, (b) avoidance of microstomia in reconstruction of large defects, (c) preservation of upper lip structure and function, and (d) provision of all lip elements by one flap in one operation. The principle of innervated facial musculocutaneous flap lip reconstruction can be extended to innervated depressor labii inferioris and facial platysma flaps, which also restore sensation and sphincter function in specific anatomic circumstances.

Depressor anguli oris flaps are my first choice for lateral defects involving between one third and two thirds of the lower lip. Based on the preceding discussion, my total approach to lower lip reconstruction is as follows: