Cheek Reconstruction

Esthetic Subunits

Traditionally, the cheek may be divided into four subunits: medial, lateral, buccal, and zygomatic. ^, In some texts, infraorbital and parotidomasseteric subunits are described, which are roughly analogous to the medial and lateral subunits, respectively. Taken together, the medial, zygomatic, and buccal subunits constitute the midcheek.

Work by Mendelson has redefined the midcheek by taking into account fascial spaces and retaining ligaments identified in anatomical studies ( Fig. 28.1 ). He divides the midcheek, which is itself defined as the area between the lower eyelid and nasolabial junction, into the lid-cheek, malar, and nasolabial segments, separated by the palpebromalar groove and nasojugal groove. This categorization more faithfully reflects the transition between the thin skin of the eyelid and the distinct contours of the malar and nasolabial segments, particularly in the aging face.

Skeletal

The facial skeleton underlying the cheek consists of zygoma, maxilla, and mandible.

Layers

The layers of soft tissue in the cheek correspond to the basic five layers found in the scalp ( Box 28.1 ). From superficial to deep, the layers are skin, followed by a layer of dense subcutaneous fat which is separated into lobules enclosed by fibrous septa. The third layer, the superficial musculoaponeurotic system, or SMAS, was first described in 1976 by Mitz and Peyronie. The SMAS is continuous with frontalis superiorly and platysma inferiorly, between which it envelops the muscles of facial expression. There is another, looser layer of fat between this and the fifth layer, that of the periosteum or deep fascia, which is often absent in the face where the tissues do not overlie bone or skeletal muscle. In areas of the face not overlying bone, different layers are encountered. For example, in the parotid region this is represented by the parotid fascia, and in the buccal subunit of the cheek, the innermost layer is the buccal mucosa.

Fascia

Fascial structures provide an anchor between bone and skin and provide soft tissue contours throughout the body. Though there is no deep fascia in the face, the principle remains valid, with fascial condensations fixing the soft tissue of the face to the underlying facial skeleton. The retaining ligaments of the face were first examined by Furnas in 1989. He described several groups of ligaments, that remain essential to our understanding of the soft tissue structure of the cheek, contributing to the formation of the contour of the face ( Box 28.2 ). They have since been studied in some detail and are of particular relevance for esthetic plastic surgical procedures such as rhytidectomy. In reconstruction, it may be necessary to disrupt intact retaining ligaments in order to gain sufficient mobilization of flaps, or to recreate the effect of the retaining ligaments using deep sutures. They are discussed in greater detail in other chapters.

Muscles

The majority of the muscles of the cheek are muscles of facial expression ( Box 28.3 ). They are embryologically derived from the second branchial arch and are supplied by the nerve of that arch: the facial nerve. The exception is masseter. As a muscle of mastication it is derived from the first branchial arch, and is supplied by the mandibular division of the trigeminal nerve. ^,