This lecture focuses on labial defects, basic facial wound closure considerations and tips on surgery of the pinna.

The lips and cheek have two epithelial surfaces: the outer skin and inner mucosa. Between these two surfaces are two thin muscles, the outer orbicularis oris muscle and the inner buccinator muscle. Other facial muscles insert at this level, including the levator nasolabialis, caninus, levator labii maxillaris, platysma, zygomaticus and sphincter colli profundus - pars palpebralis. The cheeks (buccae), which form the lateral walls of the vestibular cavity, are morphologically similar to the lips with which they are continuous.

A rich arterial and venous network supplies the skin, mucosa, muscle and fibroelastic tissue of the lips and cheeks. The facial artery divides to form the superior labial artery, inferior labial artery and the angularis oris artery. The infraorbital artery contributes circulation to the upper lip and cheek whereas the posterior, middle and anterior mental arteries supplement circulation to the anterior aspect of the lower lip. Because of this tremendous collateral circulation, the flap techniques developed for labial and buccal defects have a high probability of survival when care is taken to incorporate one or two branches of these vessels into the flap base.

Labial defects, secondary to trauma or the surgical removal of diseased tissue, can be closed with a variety of techniques, depending on the size and location of the defect. Surgical options and clinical examples of these techniques will be discussed in the lecture:

 Triangle/rectangular closure

 Labial advancement flap

 Buccal rotation technique

 Labial pivot flap

 Labial lift-up technique

 Labial pull-down technique

 Skin flap options in labial reconstruction.

Significant defects involving the facial skin and pinnal regions can be reconstructed, in most cases with skin undermining/advancement, transposition flaps or advancement skin flaps. There are several flap variations that can be used, depending on the size and location of the skin defect. It is the author's experience that local 90-degree transposition flaps can close most of these wounds without resorting to more challenging flap techniques, including the auricular and omocervical axial pattern flaps: these flaps are best reserved for large skin defects involving the head. Clinical surgical examples in this lecture will demonstrate the effective use of local skin flap techniques. It is important to keep in mind that defects adjacent to the eyelids must be thoughtfully closed, in order to avoid postoperative skin tension that can result in compromise to lid function.

It is possible to remove a variety of tumours involving the pinna without necessarily resecting the entire structure. The outer skin of the pinna transitions in laxity and thickness as you ascend to the tip of the ear. For the sake of simplicity the ear can be divided into thirds. The terminal third of the pinna is thinner and the cutaneous surfaces are more closely affixed to the interposing cartilage. The lower third of the ear and associated base of the pinna has looser, thicker outer skin that is relatively free of the cartilage. The central third of the ear is a transition between the base and terminal pinnal areas. As you ascend, the skin in this central zone becomes thinner and begins to merge with the underlying cartilage. In dogs, there is a wide variety of ear shapes and configurations. Surgical planning must take into account these variations.

What does this mean in terms of pinnal reconstructive surgery? The terminal third of the ear, in most cases, is best resected based on the 'tighter' anatomical relationship between the pinnal cartilage and outer skin surfaces. Skin flaps are a better option for reconstruction of the lower half to two-thirds of the pinna: there is ample donor skin available for transposition flap development.

Clinical examples of pinnal defects secondary to trauma or tumour removal will be demonstrated in the lecture.

References

1.  Pavletic MM. Atlas of Small Animal Wound Management and Reconstructive Surgery. 3rd ed. Ames, Iowa: Wiley-Blackwell. 2010.