Cheek

(1)

Department of Anatomy, Medical School Democritus University of Thrace, Alexandroupolis, Evros, Greece

Abstract

The cheek constitutes the face’s largest anatomic and aesthetic unit. The soft tissues and the fasciae of the cheek are arranged concentrically over its bony skeleton. From an anatomic and surgical point of view, these structures are layered as follows: skin, subcutaneous tissue, musculoaponeurotic layer (SMAS-mimic muscles), parotidomasseteric fascia, buccal space and contents, deep muscular layer, and retaining ligaments. Surgically important nerves and vessels travel through these layers often changing planes. All types of local flaps can be derived from the cheeks providing a wide range of restoration options. Random pattern advancement, transposition, and rotation flaps work well in this region and are used to reconstruct primarily the cheek itself, but also the nearby nose, lips, and lower lid.

The cheek is a convex area of either side of the face constituting the face’s largest anatomic and aesthetic constituent. It is bounded superiorly by the zygomatic arch and the orbital-cheek crease, inferiorly by the lower border of the mandible, laterally by the preauricular crease, and medially, from up to down, by the nasofacial sulcus, the nasolabial crease, and the labiomandibular creases (Fig. 5.1).

Fig. 5.1

The boundaries of the cheek

According to the morphologic-anatomic differences of the bony foundation and the soft tissue covering it, the cheek can be further subdivided into infraorbital, zygomatic, nasolabial, buccal, and parotidomasseteric subunits (Fig. 5.2).

Fig. 5.2

Cheek subunits

The above subunits of the cheek are primarily anatomic in orientation as opposed to their aesthetic value. In contrast with other areas of the face such as the nose that the subunit approach during reconstruction focused attention, the cheek demands less symmetry due to the fact that its counterpart is not comparable from the same point of view.

5.1 Layered Anatomy

The soft tissues and the fasciae of the cheek are arranged concentrically over the bony skeleton. From an anatomic and surgical point of view, these structures are layered as follows:

Skin

Subcutaneous tissue

Musculoaponeurotic layer (SMAS-mimic muscles)

Parotidomasseteric fascia

Buccal space and contents

Deep muscular layer

Retaining ligaments

Surgically important nerves and vessels travel through these layers often changing planes.

5.1.1 Skin

The skin of the cheek histologically consisted of the same components across genders and its subunits. Keratinized epithelium, hair follicles, and sebaceous and sweat glands are not homogenous throughout its entirety showing differences in thickness (ranging from 0.6 mm at the infraorbital subunit to 2.1 mm at the nasolabial subunit), quality, and laxity in each of the cheek’s subunits and across genders.

5.1.1.1 Skin and Cheek Subunits

5.1.1.1.1 Infraorbital Subunit

The skin of the infraorbital subunit is very thin with little laxity that becomes even thinner as it reaches the eyelids. Reconstructive options that involve this neighboring area to the lower lid may easily lead to ectropion. Skin incisions here must always run horizontally, parallel to the direction of the infraorbital RST lines. Every tension that is applied to the lower lid must be very carefully calculated with respect to the above factors. In addition, incisions can be camouflaged in the lower lid crease and almost become invisible after a short time.

5.1.1.1.2 Zygomatic Subunit

The zygomatic subunit is defined by the bony zygomatic complex. The skin of this subunit is attached to the underlying fascia due to fibrous retaining ligaments. The zygomatic subunit transitions from a convex area, the malar prominence, to a flatter one. Effort should be made to rebuild this protrusion by choosing an appropriate flap thickness.

5.1.1.1.3 Parotidomasseteric (Preauricular) Subunit

This subunit is bounded by the preauricular crease and a line that begins at the anterior center third of the zygomatic subunit and ends in front of the mandible’s corner. This area corresponds to the underlying parotid gland. The skin of the parotidomasseteric subunit is moderately thin and to some degree fixed to the underlying fascia showing a relative absence of laxity, especially at its most lateral preauricular part. As the skin continues medially, the thickness, laxity, and tissue availability increase particularly in elders. Incisions at this area can be hidden in the preauricular crease.

5.1.1.1.4 Buccal Subunit

The buccal cheek subunit consists of skin thicker than the rest of the other subunits, which is freely mobile over the underlying fasciae and fat. Its most medial border is the labiomandibular crease. Just lateral to the crease, the labiomandibular fold is formed by an excess of subcutaneous fat (jowl fat pad). Flaps that include the buccal subunit of the cheek become very flexible with abundant excessive tissue movement.

5.1.1.1.5 Nasolabial Subunit

The skin of the nasolabial subunit resembles the characteristics of the skin of the buccal subunit, being thick and mobile, but encompasses an important facial complex, the nasolabial crease and the nasolabial fold.

The nasolabial crease is the boundary between the cheek and the lips. Lateral to this, the nasolabial fold descends from the side of the nose to the angle of the mouth (Mallouris et al. 2013). The nasolabial crease is formed by direct (due to the absence of SMAS) dermal attachments from the underlying levator labii superioris alaeque nasi and orbicularis oris muscles (Gassner et al. 2008). The nasolabial fold is formed by the redundancy of subcutaneous fat (nasolabial fat pad) that is present lateral to the nasolabial crease in contrast to the almost absent fat medial to the nasolabial crease on the lips.

Close proximity of the nasolabial subunit with nasal ala, lip, and commissure must be considered for possible distortion, which must be prevented during flap reconstruction. The nasolabial crease does not only represent the medial boundaries of the cheek to the lips and the nose but also constitutes a line where a scar can easily be camouflaged. Furthermore, the nasolabial crease parallels the axis of the facial artery and serves as a landmark to its course.

The relaxed skin tension lines (RSTLs) on the cheek run horizontally at its upper-medial part and curve in a vertical direction as they descend to its mid- and lower third (Fig. 5.3).

Fig. 5.3

Relaxed skin tension lines (RSTLs) at the cheek

5.1.2 Subcutaneous Layer

Just under the cheek skin lays the subcutaneous layer (Fig. 5.4). The subcutaneous layer of the cheek mainly consists of fat and connective tissue fibers running through it connecting the SMAS layer with the dermis. Vascular perforators run vertically into the subcutaneous layer as they come from the deep arteries and pass through the SMAS layer to the overlying skin. In the same manner, final neural rami are distributed to the skin undersurface. The subcutaneous layer does not show a homologous thickness like other regions of the head. It varies from being very thick in the nasolabial area and very thin (almost disappearing) close to the eyelids and the lips. The subcutaneous tissue of the cheek is characterized by the way that the fat of this layer is arranged. The subcutaneous fat is compartmentalized in multiple, distinct superficial fat pads or pockets. Retaining ligaments usually border these compartments. Within these compartments the adipose tissue is accumulated in different volumes forming the unique contour of the cheek. The fat pads that are found in the cheek have been described in detail (Owsley 1993; Pessa et al. 1998; Rohrich and Pessa 2007; Gierloff et al. 2012; Pilsl et al. 2012). The main superficial fat pads of the cheek are the malar fat pad, the nasolabial fat pad, and the jowl fat pad.

Fig. 5.4

Subcutaneous layer of the cheek and superficial fat pads

5.1.2.1 Superficial Fat Pads of the Cheek (Fig. 5.4)

The nasolabial fat pad extends lateral and parallel to the nasolabial crease and is responsible for the formation of the nasolabial fold.

The malar fat pad is located lateral to the nasolabial fat pad at the zygomatic region where it thickens to form the malar prominence. It extends superiorly toward the inferior and lateral orbital margins. Its lateral part may extend even up to the parotis. This fat pad plays an important role in facial rejuvenation procedures.

The jowl fat pad is the most inferiorly situated fat pad and lying lateral to the depressor anguli oris muscle.

The aging process in addition to the synchronous loss of ligament suspension results in fat pad ptosis. This leads to an increased prominence of the folds and the characteristic appearance of the elder face.

5.1.3 SMAS and Superficial Muscle Layer

The third layer of the cheek consisted of the SMAS and the superficial layer of the mimic muscles.

5.1.3.1 SMAS

The SMAS (superficial musculoaponeurotic system) is a single and continuous fibromuscular tissue layer of the face (Fig. 5.5). It consists of collagen, elastin and muscle fibers, fat cells, and interstitial fluid. The SMAS layer varies in its micro- and macrostructure among different areas and can appear as more adipofascial or musculofascial in nature. It has no bony attachments and supports the overlying skin. This layer contains the tendon fibers of the mimic muscles that attach to the overlying skin and thus plays an important functional role in facial movement, as it distributes the forces of the muscles to the skin.

Fig. 5.5

The SMAS in lateral face

The SMAS, first described in detail as a single structure by the classic anatomic work of Mitz and Peyronie (1976), was originally defined as the fibromuscular layer in the parotid and cheek area that divides the subcutaneous fat in two discrete layers and that it is in continuity superior with the frontalis muscle and inferiorly with the platysma. Prior the definition of the SMAS by Mitz and Peyronie (1976), Skoog (1974) had already introduced dissection in a deep (“sub-SMAS”) plane for face-lifts.

Ever since its introduction, much controversy was raised in important cadaveric and histologic studies that rose questions that have not yet been definitively answered. The main points of disagreement can be summarized as follows: a clear anatomic definition, extent of SMAS in the various regions of the face and the head, the form of relation to the mimic muscles (having been described as enveloping, overlying, or merging), the number of facial muscles related to the SMAS, whether it is separate from the parotid fascia, or if it is a distinct layer from the head and neck superficial fascia (De Castro 1980; Jost and Levet 1984; Ruess and Owsley 1987; Thaller et al. 1990; Stuzin et al. 1992; Gosain et al. 1993; Yousif et al. 1994; Fuleihan 1994; Har-Shai et al. 1996, 1997; Gardetto et al. 2003; Levet 2004; Gassner et al. 2008). Parallel to the controversies regarding the SMAS, a variety of face-lifting techniques had been developed related to it (Skoog 1974; Owsley 1983; Hamra 1990; Mendelson 1992; Kamer 1996; Baker 1997).

In the posterior cheek, the SMAS lies over the parotid fascia as a clear, relatively dense layer and adheres firmly with it in a zone of 2–3 cm (Gardetto et al. 2003). Thus, the elevation of the SMAS in this area is difficult and can be achieved only by sharp dissection.

Inferiorly the SMAS passes the lower border of the mandible becoming continuous with the platysma muscle and lies over the investing layer of the deep cervical fascia. Superiorly it crosses over the zygomatic arch and becomes continuous with the temporoparietal fascia of the temple.

Extending over the masseter muscle, the SMAS covers in its upper half the zygomatic and the upper buccal branch of the facial nerve (that are running beneath the masseteric fascia) and the parotid duct. Over the lower half of the masseter, it becomes the roof of an avascular areolar tissue layer, the “premasseteric space” Mendelson et al. (2008). This layer lies immediately superficial to the masseteric fascia which constitutes its floor. It passes over the buccinator muscle, where Gassner et al. (2008) demonstrated the presence of a zone of fusion between SMAS and buccinator muscle.

In the upper cheek, the SMAS is continuous with the inferolateral portion of the orbicularis muscle. Anteriorly, medial to the zygomaticus major and to the nasolabial fold, the SMAS becomes a thin, fragile, and discontinuous fibrous network connected in variable extent and a lesser or greater degree with the mimic muscles. Τhe SMAS in this region does not appear as a clear identifiable, dissectible layer. The histologic differences of SMAS in the various areas of the face (Gardetto et al. 2003; Ghassemi et al. 2003; Gassner et al. 2008), especially those posterior and lateral to the nasolabial fold, led some authors to deny the presence of a SMAS at the anterior region of the cheek (Jost and Levet 1984; Levet 2004; Gassner et al. 2008) or even at the whole cheek (Gardetto et al. 2003). At the modiolus the SMAS merges with the orbicularis oris, zygomaticus major, and buccinator muscles.

5.1.3.2 Superficial Mimic Muscle Layer

The superficial layers of the muscles that are associated with the cheek are the orbicularis oculi, levator labii superioris alaeque nasi, levator labii superioris, zygomaticus minor, zygomaticus major, risorius, platysma, and depressor anguli oris muscles. These muscles can be topographically distinguished in an upper and a lower group (Figs. 5.6 and 5.9).

5.1.3.2.1 Orbicularis Oculi Muscle

The inferior segment of the circularly running fibers of the orbital part of the orbicularis muscle (see Chap. 3) constitutes the superficial muscle layer of the infraorbital region of the cheek (Fig. 5.6). Often the lower border of the orbicularis oculi muscle lies over the upper lip levator muscle complex, and its lateral border may extend over the upper third of the zygomaticus major muscle.

Fig. 5.6

The upper group of the superficial cheek muscles: orbicularis oculi, levator labii superioris alaeque nasi, levator labii superioris, zygomaticus minor, zygomaticus major

5.1.3.2.2 Suborbicularis Oculi Fat (SOOF)

Immediately under the inferolateral portion of the orbicularis oculi muscle and over the periosteum, a fat pocket termed “suborbicularis oculi fat” or SOOF is found (Fig. 5.7). This fat pocket belongs to the deep fat pockets of the face. The SOOF was described as a submuscular and supraperiosteal fat excess that is situated over the zygoma and acts as a mechanism for the orbicularis oculi muscle to glide (Aiache and Ramirez 1995; Aiache 2001). It is analogous to the retro-orbicularis oculi fat (ROOF) of the supraorbital area. It shows a horizontal medial part and a vertical lateral part (Hwang et al. 2008; Rohrich et al. 2009). Due to this it has been described having a “hockey stick head shape” with a horizontal length measuring 48 mm and a vertical height of 27 mm (Hwang et al. 2007c). The SOOF may slightly extend over the inferolateral orbital rim and protrude also slightly from the periphery of the orbicularis oculi muscle over the lip levator muscles.

Fig. 5.7

The SOOF. The buccal extension of the buccal fat pad is seen below the lip levators

5.1.3.2.3 Levator Labii Superioris Alaeque Nasi Muscle

The lateral slip of the levator labii superioris alaeque nasi (see Chap. 4) is the muscular border between cheek and nose (Fig. 5.6). It inserts to the upper lip and blends with fibers of the orbicularis oris and levator labii superioris muscles. It belongs to the upper lip levator muscles.

5.1.3.2.4 Levator Labii Superioris Muscle

The fibers of the levator labii superioris muscle (Fig. 5.6) originate from the infraorbital rim, just above the infraorbital foramen. The muscle runs inferiorly and slightly oblique to the upper lip. Before it inserts, its fibers blend with fibers of the zygomaticus minor muscle. It inserts to the upper lip between the insertions of the lateral slip of the levator labii superioris alaeque nasi and the zygomaticus minor muscles.

Branches of the facial and infraorbital arteries supply the muscle. Levator labii superioris is innervated by the zygomatic and buccal branches of the facial nerve.

Levator labii superioris muscle elevates the upper lip.

5.1.3.2.5 Zygomaticus Minor Muscle

The zygomaticus minor muscle has been found to be present in approximately 36–42 % of individuals (Pessa et al. 1998; Waller et al. 2008).

The zygomaticus minor muscle originates (Fig. 5.6) from the lateral aspect of the zygomatic bone just behind the zygomaticomaxillary suture. Some of its fibers originate from the orbicularis oculi muscle. It runs downward and medially into the upper lip. As it continues, its fibers blend with fibers of the orbicularis oculi muscle in various sites, which is the reason that the zygomaticus minor is in many cases difficult to distinguish (Youn et al. 2012). It inserts to the upper lip, but before its insertion, it blends with levator labii superioris muscle.

The superior labial branch of the facial artery supplies the muscle. Innervation is supplied by rami of the zygomatic and buccal branches of the facial nerve. It elevates the upper lip.

5.1.3.2.6 Zygomaticus Major Muscle

The zygomaticus major muscle (Fig. 5.6) originates from the zygomatic bone, anterior to the zygomaticotemporal suture and lateral to the origin of the zygomaticus minor muscle.

Because the zygomaticus major muscle serves as an important landmark to deep-plane (sub-SMAS) dissection, many attempts have been made to identify its upper part and origin by using several bony landmarks (Mowlavi and Wilhelmi 2004; Spiegel and DeRosa 2005; Miller et al. 2007).

A simple and accurate landmark depicting the origin of the zygomaticus major muscle was proposed by Tremolada et al. (1994). According to them, its origin is represented by the point where a line that connects the lateral canthus with the mandibular angle crosses the inferior edge of the zygomatic bone (Fig. 5.8). The origin of the zygomaticus major sometimes may be covered by the inferolateral part of the orbicularis oculi muscle.

Fig. 5.8

Origin of zygomaticus major muscle (According to Tremolada et al. 1994)

The zygomaticus major runs in an oblique direction toward the angle of the mouth.

It may appear bifid, having two separate muscle bands, in the 35–40 % of individuals (Pessa et al. 1998; Hu et al. 2008). In these cases the muscle originates normally and at the infrazygomatic region divides in a superior and an inferior bundle. The superior bundle inserts at the oral commissure and the inferior below it. Its mean width is approximately 12 mm (Pessa et al. 1998).

The muscle fibers insert into the labial angle, where they blend with the fibers of the levator anguli oris, the depressor anguli oris, and orbicularis oris muscles, risorius, buccinator. The muscle fibers that converge at the oral commissure form a tendinous node that firmly attaches to the dermis at the labial angle that is termed modiolus (see Chap. 6). The zygomaticus major muscle short before its insertion at the commissure is bifurcated into one superficial and one deep insertion head where the levator anguli oris muscle passes between them (Nairn 1975; Frellinger et al. 1987). In a detailed study, Shim et al. (2008) found that the above pattern is present in 60 % of the cases while in about 24 % the muscle divides into three insertion heads and in the remainder no division occurs. Depending on the insertion pattern, the muscle fibers blend each time with different muscle fibers of the modiolar region.

Its vascular supply comes from the superior labial branch of the facial artery. The muscle is innervated by rami of the zygomatic and buccal branches of the facial nerve.

This muscle belongs to the levator muscles of the oral commissure as it draws the angle of the mouth upward and laterally.

5.1.3.2.7 Risorius Muscle

The risorius (Fig. 5.9) is an inconstant muscle that is present in only 6 % of the individuals (Pessa et al. 1998). When present, the risorius muscle is variable in shape and form and is located at the lateral aspect of the cheek.

Fig. 5.9

The lower group of the superficial cheek muscles

Its fibers usually arise from the SMAS over the parotis and from the platysma muscle. It may also originate from the zygomatic arch. Depending on its origin, the muscle fibers run anteriorly in an oblique or horizontal axis. It inserts to the angle of the mouth.

The superior labial branch of the facial artery supplies the risorius. Buccal branches of the facial nerve innervate the muscle. Risorius retracts the angle of the mouth laterally.

5.1.3.2.8 Platysma Muscle

The platysma muscle (Fig. 5.9) is a neck muscle (see Chap. 8) but its lateral fibers cover a wide area of the inferior cheek. Superiorly the platysma becomes continuous with the SMAS, representing an anatomically homogenous unit that maintains its muscular consistency and direction of fibers as it crosses the mandible. The lateral fibers of the platysma muscle, coming from the neck, cross the mandible, pass over and cover the lower part of the parotid fascia and the masseteric fascia, and run superomedially. They continue deep to the risorius muscle, reaching the posterolateral border of the depressor anguli oris. They converge with the facial muscles at the lower lip. A portion of platysma muscle fibers also converges to the modiolus of the angle of the mouth and is referred to as platysma pars modiolaris.

The platysma muscle pulls the lower lip down and the corner of the mouth downward and laterally.

5.1.3.2.9 Depressor Anguli Oris Muscle

The depressor anguli oris muscle belongs to the depressor muscles of the oral commissure.

The depressor anguli oris muscle (Fig. 5.9) originates from the mandible inferior to the mental foramen and some fibers from the platysma. It has a linear origin that extends from the mental tubercle to a lateral distance of about 36 mm (Hur et al. 2008). Its muscle fibers run upward converging toward the angle of the mouth. It inserts to the angle of the mouth with its fibers blending with fibers of the orbicularis oris and risorius muscles. The inferior labial branch of the facial artery and the mental branch of the maxillary artery supply the muscle. The buccal and mandibular branches of the facial nerve innervate the depressor anguli oris. The depressor anguli oris pulls the angle of the mouth downward and laterally.

5.1.4 Parotidomasseteric Fascia

Just below the SMAS is a thin and glazed fascia that lies over the parotis posteriorly and over the masseter muscle anteriorly, termed the parotidomasseteric fascia (Fig. 5.10). This fascia can be found having a variable thickness and transparency, making the underlying structures slightly distinguishable.

Fig. 5.10

The parotidomasseteric fascia and the parotid-cutaneous ligament

The parotidomasseteric fascia is formed from the continuation of the investing layer of the deep cervical fascia to the head. The investing layer of the deep cervical fascia at the mandible splits in a lateral and a medial layer to surround the outer and the inner surfaces of the mandible body, respectively. As it extends superiorly, the lateral layer covers the outer surfaces of the parotis and masseter muscle and is termed parotidomasseteric fascia. Above the zygomatic arch, the parotidomasseteric fascia corresponds to the loose areolar tissue layer of the temporal area but is quite different in nature. The parotidomasseteric fascia must not be confused with the masseter muscle fascia that invests directly the masseter muscle and lies in deeper layer.

The parotidomasseteric fascia covers the parotid duct, branches of the facial nerve, and the transverse facial artery that runs beneath it and may be felt as they protrude. It also lies over the buccal fat pad and extends anteriorly blending with the epimysium of the facial muscles.

Over the parotis the fascia may show a variable thickness and strength and is densely adherent to the overlying SMAS. A false retaining ligament found here, the parotid-cutaneous ligament, amplifies the restraint of the skin. The parotid-cutaneous ligament (Fig. 5.10) is situated as a fibrous band along the posteroinferior part of the parotid gland that originates from the parotid fascia and running to the dermis anchors the skin. It is felt as resistance when elevating the skin over the parotis and has to be released. In contrast to the above area, over the lower half of the masseter muscle, Mendelson et al. (2008) described a loose areolar space, the “premasseter space”, that exists between the parotidomasseteric fascia and the SMAS platysma. This space contains no vital structures and can serve as a safe avascular sub-SMAS dissection plane.

5.1.5 Buccal Space

The parotid masseteric fascia bounds the lateral border of the buccal space found beneath it. It is filled by the buccal fat pad and its extensions and important structures that are contained in this compartment. The contents of the buccal space are the buccal fat pad and its extensions that almost fill the space, the parotid duct and minor salivary glands, the inconstant accessory parotid gland, buccal nodes, and nerves and vessels (Fig. 5.11). The nerves found in this space are the motor buccal nerve (branch of the facial nerve) and the sensory buccal nerve (division of V3). The vessels found here are the facial artery and vein and the buccal artery, all of which are examined below.

The buccal fat pad (of Bichat) is one of the deep fat pads that provide fullness to the cheek. Bichat was the first to describe it in (1802) as an encapsulated (with a thin capsule), fatty mass that fills the buccal space and has the buccinator muscle medially and the masseter muscle laterally. It shows a body and multiple extensions. The buccal fat pad is well developed and evident in infants. In adults its mean volume ranges from 9 to 10 ml, being grater in males, and its mean thickness is 6 mm (Loukas et al. 2006b). It plays an important role in suckling, mastication, and aesthetics, as it is located in a protrusive position of the cheek. Zhang et al. (2002) described in details the body and the processes of the buccal fat pad. He mentioned that the body of the buccal fat pad consists of three lobes (an anterior, an intermediate, and a posterior), fixed by ligaments to the surrounding structures. According to this description that has been further accepted (Loukas et al. 2006b; Yousuf et al. 2010), the anterior lobe is triangular in shape, is located below the zygoma, and extends anterior to the buccinator, under the zygomatic major, filling the deep space below the labii superioris muscle. The intermediate lobe is developed in children and thin in the adults and is situated around the posterior and the anterior lobe. The posterior lobe is located in the masticatory space and the surrounding spaces. The buccal fat pad shows four extensions: the pterygoid process, the pterygopalatine process, the buccal process, and the temporal process. The pterygoid process fills the pterygoid space, while the pterygopalatine extends to the pterygopalatine fossa. The temporal process is the buccal fat pad’s extension into the temporal region. This extension in the temporal area is termed as deep temporal fat pad that lies between the temporalis fascia and the outer surface of the temporalis muscle (the superficial temporal fat pad is not a part of this extension but a distinct entity) (Stuzin et al. 1989, 1990). Functionally this extension allows the temporalis muscle to glide easily under the zygomatic arch. The buccal process is the most superficial and is the extension of the buccal fat pad body below the parotid duct. The parotidomasseteric fascia covers the buccal fat pad in its lateral aspect, and the buccal branch of the facial nerve and the parotid duct are related to it. The buccal branch of the facial nerve crosses usually (74 %) superficial to the buccal fat pad but sometimes (26 %) small branches of the nerve pass through its buccal extension (Hwang et al. 2005). The arteries that supply the buccal fat pad are derived from the buccal and deep temporal branches of the maxillary artery, from the transverse facial branch of the superficial temporal artery, and from branches of the facial artery. The buccal fat pad has been widely used as a flap in the closing of oroantral fistulas. It is also a very useful tool in mucosa resurfacing in nearby to it through and through cheek defects.

Fig. 5.11

Buccal space and its contents

The parotid duct (Stensen’s duct), with a length of 6–7 cm, arises from the anterior border of the parotis and runs horizontally over the masseter muscle. At its anterior border, it turns sharply, passing through the buccal fat pad, pierces the buccinator, and opens to the oral cavity, opposite the upper second molar. Its trajectory can be represented by a line connecting the tragus with the commissure. The buccal branches of the facial nerve are related to the parotid duct as they are running parallel, above and below to it. The parotid duct passes along the lateral surface of the buccal fat pad and its buccal extension. It has been reported that in 26 % of the individuals the parotid duct can also be found deep to the buccal extension of the fat pad (Hwang et al. 2005).

The facial artery courses through the buccal space at its anterior part while the facial vein is found slightly posterior.

5.1.6 Deep Muscle Layer

The deep muscle layer of the cheek consists of the masseter, buccinator, and levator anguli oris muscles.

5.1.6.1 Masseter Muscle

The masseter muscle (Fig. 5.12), a quadrilateral in shape muscle, anatomically belongs to the masticatory muscles but topographically it occupies the frontal half of the parotidomasseteric region of the cheek. The parotid gland lies over its posterior part, and the buccal, the lower zygomatic branches of the facial nerve, and the parotid duct run over its surface. The masseter muscle consists of three layers that blend anteriorly: the superficial layer being the largest, the intermediate layer, and the deep layer.

Fig. 5.12

Deep muscle layer of the cheek

The superficial layer originates by a thick aponeurosis from the maxillary process of the zygomatic bone and the anterior two-thirds of the inferior border of the zygomatic arch. The intermediate layer originates from the deep surface of the anterior two-thirds of the zygomatic arch and from the lower border of its posterior third. The deep layer originates from the deep surface of the zygomatic arch.

The fibers of the superficial layer run inferiorly and posteriorly to the mandible in an oblique axis, while the fibers of the intermediate and deep layer run in the same direction slightly more vertical.

The superficial layer inserts into the angle and the lower posterior half of the lateral surface of the mandibular ramus, the intermediate layer into the central part of the ramus, and the deep layer into the upper part of the ramus and the coronoid process.

It has not been clarified whether fibers of the masseter muscle are attached to the auricular disk of the temporomandibular joint (Yung et al. 1990; Velasco et al. 1993; Loughner et al. 1996). It has been reported that in about the half of the individuals, muscle fibers of the deep layer of the masseter attach to the auricular disk and capsule (Matsunaga et al. 2009).

The masseter muscle is supplied by the masseteric branch of the maxillary artery and small branches, which arise from the facial and the transverse facial arteries. Additionally, the deep temporal artery contributes to the masseter supply by means of a small muscular branch (Won et al. 2012). The masseter receives its nerve supply from a branch of the anterior trunk of the mandibular nerve.

The masseter primarily elevates the mandible to occlude the teeth.

5.1.6.2 Buccinator Muscle

The buccinator muscle (Fig. 5.12) is a thin and quadrilateral muscle that forms the base of the bucal space, and fills the gap between the maxilla and the mandible.

It originates in the form of a horseshoe from the maxilla, the mandible, and the pterygomandibular raphe. Its superior border is attached to the outer surface of the alveolar process of the maxilla, its posterior border to the anterior margin of the pterygomandibular raphe, and its inferior border to the outer surface of the alveolar process of the mandible.

The fibers of the buccinators run almost parallel to the angle of the mouth. The posterior part of the muscle is situated initially deep to the ramus of the mandible and to the masseter muscle being separated from them by the buccal fat pad. Its anterior part runs under the zygomaticus major, risorius, levator, and depressor anguli oris muscles and under the facial artery, the facial vein, and branches of the facial and buccal nerves. The parotid duct, after curving the frontal border of the masseter muscle, pierces the buccinator at the level of the maxillary third molar and enters the mouth opposite the maxillary second molar tooth. Deep in the muscle lies the submucosal layer of the oral cavity.

The buccinator muscle has been described as consisting of four muscle fiber bands: the upper band originating from the maxilla, the second band originating from the pterygomandibular raphe, the third band extending from the mandible, and an inconstant most inferior band originating from the mandible under the previous one, running to the midline and merging with its contralateral (Mortellaro et al. 2001; D’Andrea and Barbaix 2006; Hur et al. 2011).

The buccinator inserts into the labial angle, the upper and the lower lip in the following manner: The upper fibers of the buccinator continue as fibers of the lower part of the orbicularis oris muscle while the lower fibers continue as fibers of the upper part of the orbicularis oris muscle, intersecting each other.

The uppermost fibers continue as fibers of the upper part of the orbicularis oris muscle and the lowermost fibers continue as fibers of the lower part of the orbicularis oris muscle.

Small muscle fibers of the buccinator muscle, lengthening from 3 to 10 mm, form a distinct bundle that extends to the terminal portion of the parotid duct, functioning in the saliva secretion (Kang et al. 2006).

The vascular supply of the buccinator muscle has been described in detail due to its use as a flap for intraoral covering (Bozola et al. 1989; Carstens et al. 1991; Zhenmin Zhao et al. 1999). It receives its blood supply from branches of the facial and the internal maxillary arteries. The facial artery provides posterior, inferior, and anterior branches to the buccinator, which supply the posterior, inferior, and anterior portions of the muscle, respectively. The internal maxillary artery contributes to the vascular supply of the buccinator mainly due to the buccal artery and a contribution of the posterior-superior alveolar artery.

The buccal artery after branching from the second part of the maxillary artery runs deep into the mandibular ramus, anterior and inferior to the lateral pterygoid muscle, and supplies the posterior part of the buccinator. It anastomoses with the posterior buccal branch of the facial artery.

The posterior-superior alveolar artery enters the posterior-superior part of the buccinator and supplies this part of the muscle. Small branches of the infraorbital artery also supply the anterior-superior part of the buccinator.

The buccal branch of the facial nerve provides the motor innervation to the buccinator muscle.

The buccinator compresses the cheek and also acts to propel food during mastication, sucking, and whistling. Problems affecting the relationship between the cheek muscles and teeth can sometimes contribute to accidental soft tissue injuries during chewing. Patients who frequently experience biting inside of cheek may benefit from understanding the possible causes, including bite alignment issues and habits that affect chewing patterns. It also participates in the lateral retraction of the oral commissure.

5.1.6.3 Levator Anguli Oris Muscle

The levator anguli oris muscle (Fig. 5.12) belongs to the levators of the oral commissure muscles and is the deepest muscle of the upper lip levator complex. It is rectangular in shape with a length of 4.8 cm and a width of 1.2 cm (Ewart et al. 2005).

Levator anguli oris muscle originates from the canine fossa of the maxilla, approximately 1 cm inferiorly to the infraorbital foramen. The muscle runs inferiorly, covered by the levator labii superioris and zygomaticus minor muscles. It inserts into the labial angle, converging with the fibers of the zygomaticus major, depressor anguli oris, and orbicularis oris and the fibers of the other muscles that form the modiolus.

The levator anguli oris muscle is supplied by the superior labial branch of the facial artery and the infraorbital branch of the maxillary artery. It receives its nerve supply from the rami of the zygomatic and buccal branches of the facial nerve. Levator anguli oris muscle raises the angle of the mouth.

5.1.7 Retaining Ligaments

Several ligaments support the facial skin in its normal anatomic position against gravitational forces. These ligaments, referred to as retaining ligaments, were first described by Furnas (1989). The retaining ligaments of the cheek draw attention due to their role in the aging process and in the rejuvenation procedures of the face (Stuzin et al. 1992; Pilsl and Anderhuber 2010; Furnas 1994; Mendelson 1995, 2009). The retaining ligaments run as fibrous bands from the deep facial structures to the overlying dermis. The retaining ligaments of the cheek are found in specific locations and can be felt as resistance to flap elevation and must be released as they cross through the dissection plane.

Several retaining ligaments have been described in the cheek (zygomatic ligament, masseteric ligament, mandibular ligament, platysma-auricular ligament, buccomaxillary ligament, platysma-mandibular ligament, subcutaneous parotid masseteric ligament) and are often the same ligaments with different nomenclature. The bands of the ligaments may originate from the periosteum and are termed as true retaining ligaments, or they may originate from the SMAS and insert as the previous into the dermis and are termed as false retaining ligaments.

The true ligaments of the cheek (Fig. 5.13) that arise from the osseous background of the cheek are the following.

Fig. 5.13

True retaining ligaments at the cheek

The zygomatic ligament (McGregor’s patch) originates as a series of fibrous septa from the periosteum at the junction of the zygomatic arch and zygomatic body just lateral to the zygomaticus major muscle.
The masseteric ligaments are found as they extend along the anterior border of the masseter muscle.
The mandibular ligament originates from the periosteum of the external surface of the mandibular body, 5 mm superiorly to the inferior edge and lateral to the depressor anguli oris muscle.

5.1.8 Arterial Supply

The cheek receives its blood supply mainly from branches of the external carotid artery, with a minor contribution of the internal carotid artery due to a small branch of the ophthalmic artery. The arteries of the external carotid that contribute to its arterial vasculature are the infraorbital, the transverse facial, and the facial arteries. The contribution of the internal carotid system happens by the small zygomaticofacial artery.

5.1.8.1 Infraorbital Artery

The infraorbital artery is one of the three branches of the maxillary artery, together with the mental and buccal arteries, that supply the face.

The infraorbital artery arises from the third part of the maxillary artery. It enters the orbit through the posterior part of the inferior orbital fissure. It runs on the floor of the orbit along the infraorbital groove and enters the infraorbital canal in company with the infraorbital nerve. On its course in the infraorbital groove and canal, it gives branches for the inferior rectus and inferior oblique muscles, the nasolacrimal sac and the anterior superior alveolar artery, and sometimes the middle superior alveolar artery.

The artery emerges onto the face through the infraorbital foramen (Fig. 5.14). The infraorbital artery is located in the middle and superficial of the infraorbital nerve bundle in about 74 % of the cases, lateral to it in 20 %, and in the remainder medial to it (Hu et al. 2006). As it exits to the face, through the infraorbital foramen, it lies under levator labii superioris muscle and very quickly divides into its lower lid, nasal, and superior labial and cheek branches.

Fig. 5.14

The infraorbital artery at the face

The lower lid branches run upward under the cover of the orbicularis oculi muscle, and after piercing it they distribute to the skin of the lower eyelid. The nasal branches of the infraorbital artery distribute to the lateral side of the nose. The superior labial branches are larger and numerous. They run inferiorly between the levator labii superioris and the levator anguli oris and are distributed to the upper lip and the anterior part of the cheek. Multiple anastomosing branches connect the infraorbital artery with the angular, the dorsal nasal, the transverse facial, and the buccal arteries.

5.1.8.2 Zygomaticofacial Artery

The zygomaticofacial artery constitutes the contribution of the internal carotid artery to the cheek. It is a branch of the lacrimal artery, which in turn is branched from the ophthalmic artery of the internal carotid. The lacrimal artery runs forward at the junction of the orbital roof and the orbit lateral wall. Within the orbit, it gives off the zygomatic artery, which subdivides into the zygomaticotemporal and zygomaticofacial artery.

The zygomaticofacial artery appears on the cheek (Fig. 5.15) through the zygomaticofacial foramen and supplies the skin of the malar region. The zygomaticofacial foramen varies in its position and is expected to be found in a mean distance of 1.1 cm from the inferolateral orbital margin (Loukas et al. 2008). When the zygomaticofacial artery exits, it immediately supplies the skin of the malar region. In cases where the inferolateral portion of the orbicularis oculi muscle extends over the zygomaticofacial foramen, the artery pierces the muscle to reach the subcutaneous tissue. The zygomaticofacial artery anastomoses with the transverse facial and zygomaticoorbital arteries.

Fig. 5.15

Zygomaticofacial artery

5.1.8.3 Superficial Temporal Artery: Preauricular Course

The superficial temporal artery is the smaller of the two terminal branches of the external carotid artery (the other one being the maxillary artery). The bifurcation of the external carotid artery happens at the level of the neck of the mandibular condyle, deep or even within the parotis that identifies the origin of the superficial temporal artery. The artery runs upward as a continuation of the external carotid artery and passes over the zygomatic arch continuing along the side of the head where it bifurcates to the frontal and parietal branches.

Its long course can be distinguished in two parts: a first preauricular part at the cheek and a second temporal part above the zygomatic arch.

5.1.8.3.1 Preauricular Course

After its origin, the superficial temporal artery continues upward giving off the transverse facial artery after which it appears at the superior border of the parotid gland. It pierces the parotidomasseteric fascia and continues along within the SMAS temporoparietal fascia layer.

Ascending from the parotid gland, the superficial temporal (Fig. 5.16) artery passes at a distance ranging from 0.5 to 1.0 cm in front of the anterior edge of the tragus, in a depth of up to 1.0 cm. The mean diameter of the superficial temporal artery here ranges between 2 and 2.7 mm (Stock et al. 1980; Lang 1995; Chen et al. 1999; Pinar and Govsa 2006).

Fig. 5.16

Superficial temporal artery at the preauricular region and its relation to the superficial temporal vein and the auriculotemporal nerve

Even though many variations exist, the most usual in the pretragal area is that superficial temporal vein which accompanies the artery, runs laterally to it and in a more superficial level. The auriculotemporal nerve runs lateral or superficial to the artery and in a variable unpredictable relation to the vein. As many scalp and facial flaps involve a preauricular incision and a preauricular flap elevation, the above relation of the vessels and the distance from the tragus must be kept in mind so as to avoid injury.

The superficial temporal artery gives off two small branches, the middle and the lower auricular arteries (the upper auricular artery is branched from a higher level at the temporal course of the superficial temporal artery) that contribute to the supply of the auricle (see Chap. 7).

5.1.8.4 Transverse Facial Artery

The transverse facial artery (Fig. 5.17) arises from the superficial temporal artery before it emerges from the gland. In 70 % of cases, it arises as one branch and in the rest as two or three (Yang et al. 2010). It is situated in a plane deep to the facial nerve.

Fig. 5.17

The transverse facial artery

In their detailed study, Yang et al. (2010) found out that the transverse facial artery usually divides within in the parotid substance into two trunks that in most cases emerge from the anterior border of the gland, as superior and inferior branches, and described their course as follows.

The superior branch, the largest one, emerges from the upper part of the parotis and courses forward into the cheek, located between the zygomatic arch and the parotid duct in a distance of about 1.5 cm inferiorly to the zygomatic arch. It usually gives off a descending branch that crosses the parotid duct and supplies the area below the duct together with the inferior branch. The superior branch also gives branches to the superior part of the masseter, to the zygomaticus major, and multiple branches to the soft tissues of the malar area.

The inferior branch, smaller than the previous, emerges from the lower part of the parotis and runs superficial to the masseteric fascia, coursing inferior to the parotid duct. It distributes to the masseter muscle terminating as muscular or as cutaneous branch. The inferior branch in about 27 % terminates its course within the parotid gland as muscular branch.

Due to its numerous branches, the transverse facial artery supplies the parotid gland, the parotid duct, the facial nerve, the masseter muscle, and a large area of the cheek skin.

An important large cutaneous perforator of the transverse facial artery (Fig. 5.18), located approximately 3 cm lateral and 3.5 cm inferior to the lateral canthus, provides the main direct blood supply to the skin of the preauricular area and the lateral cheek, defining its vascular territory (Whetzel and Mathes 1992, 1997; Schaverien et al. 2009). The territory, perfused by this perforator, extends superiorly 1–2 cm above the zygomatic arch, inferiorly 2 cm above the border of the mandible, anteriorly over the malar eminence to the lateral canthus, and posteriorly 1–2 cm anterior to the ear (Whetzel and Mathes 1992; Whetzel and Stevenson 1997). This perforator branch is sectioned during elevation of flaps when dissecting in this area. However, the viability of the flaps is guaranteed due to collateral flow from the multiple anastomosing branches of the neighboring arteries.

Fig. 5.18

Cutaneous perforator of the transverse facial artery

The transverse facial artery anastomoses with the zygomaticoorbital, the lacrimal and the infraorbital arteries superiorly, the facial and the masseteric arteries anteriorly, and the buccal artery deeply.

The development of the transverse facial artery is anatomically and functionally related inversely to the development of the facial artery. The facial artery may be underdeveloped and end as superior or inferior labial artery (see Sect. 5.1.8.7). In these cases the missing territory of the facial artery is “taken over” to a variable extent, by the ipsilateral transverse artery (Cormack and Lamberty 1994).

A giant and largely dilated transverse facial artery has also been reported to counterpoise the complete agenesis of a facial artery (Tubbs et al. 2005).

5.1.8.5 Buccal Artery

The buccal artery (Fig. 5.19) is a small branch that arises from the second part of the maxillary artery. It runs between the medial pterygoid and the attachment of the temporalis muscle, crosses the buccinator, and just anterior to the anterior edge of the masseter muscle pierces the buccal fat. It supplies the skin of an area over the buccinator muscle and anastomoses with branches of the infraorbital and facial artery.

Fig. 5.19

Buccal artery

The artery is located about 3 cm lateral to the oral commissure and at the same level 5 mm medial to the medial aspect of the masseter muscle.

5.1.8.6 Facial Artery (Facial Part)

The facial artery is a long, major facial vessel, with important branches, that starts from the carotid triangle and usually ends to the inner canthus. This long course can be distinguished into a cervical and facial part. The cervical part of the facial artery is the segment from its carotid artery origin to the point where it curves around the lower border of the mandible to enter the face (see Chap. 8).

The cervical part of the facial artery as it comes from the posterior aspect of the submandibular gland reaches the lower mandibular border, curves around it, passes just in front of the anterior edge of the masseter muscle, pierces the deep fascia, and enters the face. At this point the facial artery, with its accompanying vein, lies immediately under the platysma and crosses with the mandibular branch of the facial nerve lying underneath it. When a dissection in this area is performed, it must be protected, as it lies very superficial at this point (where its pulsation is most palpable). In this region, its external diameter is about 2.6 mm (Pinar et al. 2005).

5.1.8.6.1 Facial Part

As the facial artery enters the face (Fig. 5.20), it courses tortuously up and forward toward the alar base, lying under the platysma and the fat of the cheek. It ascends passing lateral to the oral commissure in a distance that has been reported to range between 8 and 23 mm (Loukas et al. 2006a; Pinar et al. 2005; Park et al. 1994; Schulte 2001). Most of the time the facial artery is expected to be 1.5–2.0 cm lateral to the oral commissure and running up medial to the nasolabial fold (Fig. 5.21). The range of the distance from the oral commissure where the facial artery can be found is of great importance when designing a Gillies fan flap or a Karapandzic flap for lip reconstruction; the viability of these flaps requires an intact facial artery that must be identified and preserved.

Fig. 5.20

The facial artery at the cheek

Fig. 5.21

The facial artery passes 1–2 cm lateral to the oral commissure and usually lies medial to the nasolabial fold (blue dotted line). The mean distances of the origin points of the facial artery branches are indicated

Near the angle of the mouth, the facial artery is under the cover of the zygomaticus major (or it may pass through its insertion heads) and the risorius muscles. It is superficial to buccinator and levator anguli oris muscles. Here it gives off small branches to the anterior part of the buccinator and to the zygomaticus major muscles. Above the labial commissure level in the upper lip, the facial artery usually lies medially in relation to the nasolabial sulcus. Turning cephalad, it passes either over or through the levator labii superioris and runs along the side of the nose, usually through the levator labii superioris alaeque nasi, toward the inner canthus, where it anastomoses with the dorsal nasal artery. Partial myotomy of the above superficial muscles must be done to expose the facial artery in cases that it is needed in flap surgery. The buccal fat pad is situated under the artery at this point. The distal and terminal part of the facial artery, after giving off its last branch, the lateral nasal artery, is termed the angular artery.

The branches (Fig. 5.20) given off by the facial part are the premasseteric artery, the labiomental artery, the inferior and superior labial arteries (see Chap. 6), and the inferior alar and the lateral nasal arteries (see Chap. 4). As mentioned above the terminal part of the artery distal to its terminal branch is named angular artery.

The premasseteric artery is a small and not always present branch that arises at the lower border of the mandible and ascends along the anterior border of the masseter muscle. The labiomental artery is an inconstant branch running horizontally to the chin.

After giving off the lateral nasal artery, it ascends along the nasal side, immediately under the skin, giving off small branches and finally anastomoses with the dorsal nasal artery, which establishes the communication between the external and internal carotid arteries.

The mean distances of the points where the facial artery branches originate are shown in Fig. 5.21.

The facial part of the facial artery anastomoses with the mental artery, the transverse facial artery, the infraorbital artery, and the ophthalmic artery (due to the dorsal nasal artery).

The facial artery shows multiple (mean six) perforating branches that supply large areas of facial skin and are more densely located at the level of the commissure (Fig. 5.22).

Fig. 5.22

Facial artery perforators to the skin

5.1.8.7 Facial Artery Variations

The variations and the branching pattern of the facial artery have been investigated thoroughly (Mitz et al. 1973; Kozielec and Jozwa 1977; Midy et al. 1986; Niranjan 1988; Whetzel and Mathes 1992; Park et al. 1994; Crouzet et al. 1998; Nakajima et al. 2002; Pinar et al. 2005; Loukas et al. 2006a).

Surprisingly great differences exist, ranging from frequency of types of branching patterns, in their description and nomenclature (specifically regarding the arteries to the nose) among the investigators.

A variation of the facial arteries course is exhibited when the artery is underdeveloped, and thus, the artery does not reach its normal ending point.

In general the result is that each type is missing a subsequent branch starting from the angular artery. Four major types of facial artery exist (Fig. 5.23). The first two types are the most common and represent about the 90 % of cases.

Fig. 5.23

Facial artery variations

5.1.8.7.1 Typical

In the typical form, the facial artery is completely developed and ends with its final angular artery.

5.1.8.7.2 Ending as Lateral Nasal

In this form, the angular artery is absent and the facial artery ends to its lateral nasal branch. In this type, sometimes the angular artery is present as “ectopic.” It arises individually at the level or from a slightly lower point of the commissure and ascends to the inner canthus.

5.1.8.7.3 Ending as Superior Labial

When both angular and lateral nasal arteries are not present, the facial artery ends to the superior labial artery. In these cases, often a “reverse” inferior alar artery is branched from the columellar artery and courses along the inferior margin of the nostril.

5.1.8.7.4 Ending as Inferior Labial

In very rare cases, the facial artery consists, in its facial part, only of the inferior labial artery.

In the various types where the facial artery is underdeveloped, other neighboring arteries of the face—infraorbital, ophthalmic, transverse facial, or even a hyperdeveloped contralateral—assume the role of supplying the area.

It has been clarified that contrary to what previously had been believed, no ethnic differences exist in the pattern of the facial artery branching (Koh et al. 2003; Loukas et al. 2006a).

5.1.9 Venous Drainage

The small veins of the cheek generally follow the associated arteries and converge to larger ones that drain to the named larger veins of the cheek. The facial vein provides the major venous drainage to the cheek. It appears to the cheek (Fig. 5.24) as continuation of the angular vein running at the side of the nose (see Chap. 4).

Fig. 5.24

The venous drainage of the cheek

The facial vein continues running within the buccal space lying above the buccal extension of the buccal fat pad. Although the facial vein runs in a same direction as the facial artery it is situated posterior to the facial artery in a variable distance. At the level of the nasal ala the mean distance of the facial vein and artery has been measured to be 16.3 mm and at the oral commissure 13.6 mm (Zhao et al. 2000). As the facial vein proceeds to the lower border of the mandible it approximates the artery and the two vessels run in close proximity. It crosses the lower mandibular border lying beneath the platysma and continues down in the neck where it drains into the common facial vein and the internal jugular vein.

The facial vein at the cheek receives the lateral nasal (superior alar) and the inferior alar veins of the nose, the venae commitante of the lips, and the buccinator and masseteric veins. It communicates also with the infraorbital vein.

The transverse facial, infraorbital, mental, and buccal veins contribute to the venal system of the cheek draining the first into the superficial temporal vein and the next three into the pterygoid venous plexus.

5.1.10 Sensory Innervation

Sensory innervation of the cheek comes from the infraorbital nerve and zygomaticofacial nerve, branches of the maxillary division of the trigeminal nerve, and the auriculotemporal, the mental, and the buccal nerves, branches of the mandibular division, the third and largest division, of the trigeminal nerve (Fig. 5.25). The anterior branch of the great auricular nerve (C2-C3) with its final filaments, contributes to the innervation of the skin of the parotidomasseteric region.

Fig. 5.25

Sensory innervation of the cheek

5.1.10.1 Infraorbital Nerve

The intraorbital continuation of the maxillary nerve just after it passes through the inferior orbital fissure is named the infraorbital nerve constituting actually the terminal branch of the maxillary nerve. It courses on the floor of the orbit along the infraorbital groove in common course with the infraorbital artery and enters the infraorbital canal.

The infraorbital nerve (Fig. 5.26) exits to the face through the infraorbital foramen. It lies under levator labii superioris and over levator anguli oris muscles and divides into its terminal palpebral, nasal, and superior labial branches. The terminal branches of the infraorbital nerve in about 40 % of the cases exit the infraorbital foramen as a completely separated bundle; in the remainder they may be fused and separate after a short course (Hu et al. 2006).

Fig. 5.26

The infraorbital nerve

The palpebral branches of the infraorbital nerve run upward under the cover of the orbicularis oculi muscle, and after piercing it they distribute to the skin of the lower eyelid. Near the lateral canthus, they anastomose with branches of the facial and zygomaticofacial nerves. The nasal branches of the infraorbital nerve distribute to the skin of the lateral side of the nose and to the ala. They anastomose with the external nasal nerve. The multiple superior labial branches are the larger one. They run inferiorly under cover of the levator labii superioris muscle and are distributed to the skin and the mucosa of the anterior part of the cheek and the upper lip. They anastomose with filaments of the facial nerve.

The infraorbital foramen is located at a point usually 8–10 mm below the inferior orbital rim and approximately 25–30 mm from the midline (Fig. 5.27). This point may range between 3 and 15 mm from the inferior orbital rim and between 18 and 33 mm from the midline (Aziz et al. 2000; Chrcanovic et al. 2011).

Fig. 5.27

Landmarks of infraorbital nerve

5.1.10.1.1 Infraorbital Nerve Blockade

Excision of small or medium lesions and minor flap reconstruction can be achieved by local or better by regional anesthesia. The infraorbital block provides anesthesia to the half of the upper lip in its whole thickness and can be performed either extraorally or intraorally (Fig. 5.28).

Fig. 5.28

Block of the infraorbital nerve. (a) Extraorally. (b) Intraorally

For an extraoral nerve block, the infraorbital foramen is palpated inferior to the infraorbital rim. If this is unclear, then the point of injection is situated 2.5 cm lateral to the midline and 1 cm below the orbital rim. At this point about 1 ml of local anesthetic solution is injected just above the bone with the needle carried slightly cephalad. Entering the foramen should be avoided because direct injection within the foramen may result in nerve damage.

At an intraoral block of the infraorbital nerve, the needle is inserted slightly lateral to the buccal sulcus above the first premolar teeth. It proceeds upward, parallel to the long axis of the first premolar and targeting the infraorbital foramen. When the tip of the needle is palpated near the foramen, the anesthetic solution is injected.

5.1.10.2 Zygomaticofacial Nerve

The zygomaticofacial nerve is the second of the two branches of the zygomatic nerve along with the zygomaticotemporal nerve (see Chap. 2) that is branched from the maxillary nerve and runs along the inferolateral border of the orbit.

The zygomaticofacial nerve exits the face (Fig. 5.29) through the zygomaticofacial foramen that is situated in the zygomatic bone 2 cm lateral and 2 cm inferior to the lateral canthus. It pierces the overlying orbicularis oculi muscle and distributes in an area to the skin over the prominence of the cheek up to the lateral canthal area. It anastomoses with the zygomatic branches of the facial nerve and the palpebral branches of the maxillary nerve.

Fig. 5.29

Zygomaticofacial nerve

5.1.10.3 Auriculotemporal Nerve: Preauricular Course

Although the auriculotemporal nerve supplies only in a small part of the posterior zygomatic subunit, its first part runs at the cheek just in front of the auricle together with the superficial temporal artery and vein.

The auriculotemporal nerve is a branch of the posterior trunk of the mandibular nerve and is located at the posterior border of the cheek. As the mandibular nerve descends from the foramen ovale and after giving off the nervous spinosus (meningeal branch) and the nerve to the medial pterygoid, it divides into an anterior and a posterior trunk. The posterior trunk gives off the auriculotemporal nerve along with the lingual and inferior alveolar nerves.

The auriculotemporal nerve arises from the mandibular nerve mostly by one or two and seldom by three or four roots. In the cases where it arises by two roots, these usually encircle the middle meningeal artery. It then runs backward lying on the surface of tensor veli palatini and under the lateral pterygoid muscles and passes between the neck of the mandible and the sphenomandibular ligament.

The auriculotemporal nerve exits the cheek (Fig. 5.30) behind the temporomandibular joint within the superficial substance of parotis. It then runs upward, passing over the posterior root of the zygomatic arch to the temporal area.

Fig. 5.30

Auriculotemporal nerve at the cheek

The auriculotemporal nerve runs parallel to the superficial temporal artery located in 80 % superficial or posterior to it (Jeong et al. 2010). It is of clinical interest that the auriculotemporal nerve in about one-third (30 %) has a direct relationship with the temporal artery that could constitute a trigger for migraine headaches (Janis et al. 2010). In its course it gives off branches to the external acoustic meatus and the anterior portion of the auricle, the temporomandibular joint, the parotis, and over the zygomatic arch the final superficial temporal branches (see Chap. 2).

5.1.10.4 Buccal (Sensory) Nerve

The buccal nerve is branched from the anterior trunk of the mandibular nerve (V3) at the infratemporal fossa. It runs anteriorly between the two heads of the lateral pterygoid and then inferiorly through the lower part of the temporalis muscle, continuing to the undersurface of the mandibular ramus.

The nerve appears in the cheek (Fig. 5.31) close to the anterior border of the masseter muscle, superficial to the buccinator muscle, and anastomoses with buccal branches of the facial nerve (Standring 2008). It supplies the skin and mucosa of the central part of the cheek.

Fig. 5.31

Buccal nerve

5.1.10.5 Mental Nerve

The mental nerve, after its exit through the mental foramen, results in branches that mainly supply the chin and the lower lip (see Chap. 6) but it also contributes due to some short rami to the innervation of the nearby cheek skin.

5.1.10.6 Great Auricular Nerve

The anterior branch of the great auricular nerve (see Chap. 8) due to its final filaments innervates the skin of the parotidomasseteric area.

5.1.11 Motor Innervation

Motor innervation of the mimic muscles that are distributed to the cheek comes from the peripheral branches of the facial nerve. There is a highly variable anatomy in the branching pattern of the facial nerve and in the course of these branches to the cheek, temple, and neck, and what follows is an averaged description.

5.1.11.1 Facial Nerve

The facial nerve trunk exits the posterior cranial fossa entering the temporal bone via the internal acoustic meatus. After coursing through the facial (Fallopian) canal, it emerges from the base of the skull at the stylomastoid foramen.

5.1.11.1.1 Extratemporal Course

At this point, the main nerve trunk lies in a depth of approximately 2–2.5 cm, in front of the mid-earlobe. But the classical precise landmarks useful in parotid surgery are the cartilaginous tragal pointer of the external auditory canal with the nerve situated 1 cm deep and inferior to this, the tympanomastoid suture line where the trunk is identified 6–8 mm below it, and the posterior belly of digastric where the nerve lies 1 cm deep to this.

As the facial nerve emerges from the stylomastoid foramen, it gives off the digastric branch for the posterior belly of the digastric muscle, the stylohyoid branch for the stylohyoid muscle, and communicating branches with the transverse cervical nerve and the posterior auricular nerve (see Chap. 2).

It then runs anteroinferiorly over the styloid process for a distance approximately 12 mm and enters the parotis through its posteromedial surface.

5.1.11.1.2 Intraparotid Course

Within the parotid gland, the nerve soon divides into its two primary trunks, the temporofacial (superior) trunk and cervicofacial (inferior) trunk lying over the retromandibular vein and the external carotid artery. The two primary trunks branch further resembling the so-called “pes anserinus” (goose’s foot) and form the parotid plexus. The presence of the facial nerve plexus within the parotid substance divides the gland into its surgically so-called superficial and deep “lobes.”

From the two main temporofacial and cervicofacial trunks that form the parotid plexus, the facial nerve gives rise to five main terminal branches. These branches diverge within the parotid gland and exit the gland by its anterior margin. The five terminal branches supply the mimic muscles of the face and are named according to the region that they are distributed: temporal (or frontal), zygomatic, buccal, marginal mandibular, and cervical. The facial nerve, within the parotid substance, courses superficially to the retromandibular vein. The inferior branches of the facial nerve in 5–10 % of the cases have been reported to lie deep to the retromandibular vein (Wang et al. 1991; Kopuz et al. 1995).

The terminal branches of the facial nerve can be predicted to exit the anterior margin of the parotis, approximately 4 cm anterior to the tragus along the transverse axis of the zygomatic arch (Wilhelmi et al. 2003).

5.1.11.1.3 Frontal Branch

The frontal (temporal) branch of the facial nerve (Fig. 5.32) runs mostly at the temple to supply mainly the mimic muscles that surround the upper and lateral orbit. At the cheek area, the nerve is involved due to its initial course at the zygomatic subunit: The frontal branch arises from the temporofacial trunk and leaves the upper border of the parotid gland. It travels deep to the parotidomasseteric fascia toward the middle third of the zygomatic arch. As it crosses the superficial surface of the zygomatic arch, it divides into two to four rami. Above the zygomatic arch, it travels along the undersurface of the temporoparietal fascia (Stuzin et al. 1989). The area of increased nerve jeopardy is the zone where the nerve crosses the zygomatic arch. At this area the nerve lies very superficial even within the temporoparietal fascia as stated by Stuzin et al. (1989) or in a deeper plane, over the periosteum, as stated by Owsley and Agarwal (2008) and Trussler et al. (2010) (see Chap. 2).

Fig. 5.32

The facial nerve

5.1.11.1.4 Zygomatic Branch

The zygomatic branch (Fig. 5.32) arises from the temporofacial trunk of the facial nerve division usually as two or three rami and very rare as a single ramus (70, 27, and 3 % respectively) (Saylam et al. 2006a).

Course

After emerging from the posterior border of the parotid gland, the zygomatic branches course initially below the lower border of the zygomatic arch under cover of the parotidomasseteric fascia. As they reach the orbicularis oculi muscle, they travel through the SOOF becoming more superficial and innervate the muscle from its undersurface. The superior ramus crosses the zygomatic bone in the same depth as the frontal branch of the facial nerve, ascends to the lateral orbital rim and innervates the lateral part of the orbicularis oculi muscle. Some tiny branches may be encountered traveling to the lower lateral border of the orbicularis oculi muscle over the zygomaticus major muscle.

The inferior ramus continues medially to the infraorbital region, passing below the origin of the zygomaticus major muscle, and innervates the lower part of the orbicularis oculi muscle from its undersurface. Precisely the orbicularis oculi muscle is supplied by means of neural plexuses. The superior ramus of the zygomatic nerve forms an anastomotic plexus with the temporal branches of the facial nerve that supplies the superolateral part of the orbicularis oculi, and the inferior ramus forms a same plexus with connections to the buccal branch that supplies the inferolateral part of the orbicularis oculi muscle (Ouattara et al. 2004). Small branches of the inferior ramus innervate the upper part of the upper lip levators. Typical neural interconnections between the zygomatic and the buccal branches exist, but furthermore they form also the angular nerve (see below).

The course of the zygomatic branch lies always under the oblique line that connects the tragus and the lateral palpebral commissure, and from the midpoint of this line, its vertical distance varies from 6 to 29 mm (mean 19 mm) (Saylam et al. 2006a).

5.1.11.1.5 Buccal Branch

The buccal branch (Fig. 5.32) originates from either the temporofacial trunk or the cervicofacial trunk, or from both of them.

Course

The buccal branch emerges from the parotid gland usually (60 %) as a double branch (an upper and a lower) or as single (40 %). It runs horizontally forward, beneath the parotidomasseteric fascia in close relation to the parotid duct. When presented as one branch, it runs in most of the cases inferior to the duct, and when the buccal branch is presented as dual, the upper branch runs superior and the lower branch inferior to the duct. The mean vertical distance of the buccal branch either inferior or superior to the parotid duct is 5.5 mm (range between 1 and 14 mm) (Pogrel et al. 1996). The buccal branches (or a single branch), after emerging from the anterior border of the parotis, run over the masseter muscle fascia (which must not be confused with the overlying parotidomasseteric fascia). It crosses superficial to the buccal fat pad but sometimes (26 %) small branches of the nerve pass through the buccal extension of the buccal fat pad (Hwang et al. 2005). As it passes over the buccinator muscle, it sends rami to it and, finally, results in its final subbranches. The lower subbranches enter to the inferior segments of the orbicularis oris muscle and the upper portion of the depressor anguli oris muscle from their undersurface and innervate them. The upper subbranches continue under the cover of the zygomaticus major and the upper lip levator muscles but run above the levator anguli oris muscle and reach the upper segments of orbicularis oris muscle from its undersurface. They innervate the upper part of the orbicularis oris muscle and the lower part of the upper lip levators and lower part of the nasal muscles. In cases where a second (upper) branch is present, it runs also beneath the zygomaticus major and the upper lip levator muscles and supplies the same former muscle groups.

Caminer et al. (2006) found that the buccal branch, after receiving a contribution from the zygomatic branch, forms a branch and term it the angular nerve, which runs superiorly, crosses over the medial canthus, and supplies the medial part of orbicularis oculi, the procerus, and a part of the corrugator (oblique head) (Caminer et al. 2006).

The buccal branch of the facial nerve is connected to the sensory buccal nerve of the mandibular nerve (Rodel and Lang 1996) and to the external nasal nerve. Moreover, it anastomoses with the inferior ramus of the zygomatic nerve, forms a plexus, and participates in the innervation of the inferolateral part of the orbicularis oculi muscle (Ouattara et al. 2004). As mentioned above it participates along with the inferior ramus of the zygomatic nerve to the formation of the inferolateral orbital nerve plexus (Ouattara et al. 2004).

5.1.11.1.6 Marginal Mandibular Branch

The marginal mandibular branch (Fig. 5.32) originates from the cervicofacial trunk of the facial nerve.

Course

It emerges from the caudal border of the parotis usually as two branches (60–65 %) and less often as one branch (23 %). Three branches occur seldom (9 %). Rarely (3 %), the marginal mandibular branch may be present as four branches (Dingman and Grabb 1962; Ziarah and Atkinson 1981). The emergence point of the nerve from the parotis is usually on the mandibular angle level, or very close to it.

The marginal mandibular branch passes in a trajectory that runs to the lower border of the mandible and then curves up and forward to the lower lip and chin. In this course it has an importance to surgery in relation to the inferior border of the mandible. In a variable percentage of approximately 47–80 %, the nerve runs superior to the lower border of the mandible and in the remainder inferiorly to the lower border (Dingman and Grabb 1962; Ziarah and Atkinson 1981). In the later cases, the marginal mandibular branch, running down, crosses once across the inferior border of the mandible and, turning up, crosses it again for the second time in the vast majority of people, at the point where the facial artery crosses the mandible or posterior to it and, rarely, anterior to this point. When the marginal mandibular branch appears having more than one branches, these are distributed the same superiorly and inferiorly in relation to the lower border of the mandible. The marginal branch when coursing below the inferior border of the mandible runs in a variable distance from it, usually up to 1.5–2 cm. Incisions that are placed at least 3 cm below the inferior border always ensure the integrity of the nerve.

The classic descriptions of the anatomy of the marginal mandibular branch of the facial nerve refer that the nerve runs deep to the platysma. However, Owsley and Agarwal (2008) “put” the nerve in a deeper plane and described the detailed and accurate planar anatomy of its course. According to them, the marginal mandibular nerve emerges from the parotid and initially lies deep to the parotidomasseteric fascia or its neck continuation: the investing layer of the deep cervical fascia when a branch (or branches) extends below the lower mandibular border. Near the point where the facial artery curves around the mandibular border, the marginal mandibular nerve penetrates the parotidomasseteric fascia (investing layer of the deep cervical fascia) that continues immediately deep to the platysma, changing level and becoming more superficial. The nerve is at great risk in thin patients with a thin layer of subcutaneous tissue. Moreover the variability in thickness and development of the platysma muscle that also in older patients might be very thin in this area make it difficult to determine clearly the anatomy of the fascial layers, jeopardizing even more the mandibular branch.

The nerve crosses the anterior facial vessels always lying superficially to them. Continuing forward becomes more superficial and penetrates the muscles of the lower lip and chin to their undersurface.

The marginal mandibular branch supplies the risorius, the inferior part of the orbicularis oris, the depressor anguli oris, the depressor labii inferioris, and the mentalis muscles. It shows interconnections with the buccal, the zygomatic, and the cervical branches of the facial nerve and the sensory mental nerve (Schwember and Rodrigez 1988; Rodel and Lang 1996; Hwang et al. 2007b).

5.1.11.1.7 Cervical Branch

The cervical branch originates from the cervicofacial trunk of the facial nerve, usually as one and seldom as two branches, and travels down to the neck to innervate the platysma muscle (see Chap. 8).

5.1.11.1.8 Branching and Anastomotic Patterns of the Facial Nerve

In an attempt to sort out the variability of the branching pattern and the existing anastomoses of the facial nerve, Davis et al. (1956), in their classic anatomic study of 350 facial nerves, grouped these in six types.

Type I

In type I (13 %), no anastomoses occur between the adjacent branches and the five terminal branches spread out to the face in a radial form.
Type II

In type II (20 %), anastomoses occur between the various branches of the temporofacial trunk, to a distal point beyond the anterior border of the parotis.
Type III

In type III (28 %), a single and large anastomotic branch, which runs beyond the anterior margin of the parotis and crosses the parotid duct, connects the temporofacial and the cervicofacial trunks.
Type IV

In type IV (24 %), anastomotic branches, forming loops, exist between the temporal, zygomatic, and buccal branches.
Type V

Type V (9 %) is characterized by two anastomotic branches that connect the cervicofacial with the temporofacial trunks.
Type VI

In type VI (6 %), a rich anastomotic network exists connecting all of the branches of the facial nerve except for the cervical one.

5.2 Flaps Derived from the Cheek

All types of local flaps can be derived from the cheeks providing a wide range of restoration options. Random pattern advancement, transposition, and rotation flaps work well in this region and are used to reconstruct primarily the cheek itself, but also the nearby nose, lips, and lower lid.

5.2.1 Flap Design Concerning Vascular Anatomy

The blood supply of the cheek skin is mainly originating from branches of the facial, transverse facial, and infraorbital arteries. The rest of the arteries encountered at the cheek supply smaller areas that often overlap to the major vascular territory of the facial, transverse facial, and infraorbital arteries (Fig. 5.33). Neighboring arteries also contribute to the cheek skin perfusion at its periphery. For instance, the zygomaticoorbital artery, an artery that runs at the temple, supplies the skin of the zygomatic subunit. Likewise the submental artery contributes to the supply of the inferior cheek.

Fig. 5.33

Vascularization of the cheek skin

The skin of the cheek receives its blood supply from cutaneous and myocutaneous perforators that diverge from the underlying arteries and form the arterial plexuses. As already mentioned important cutaneous perforators are derived from the transverse facial and facial arteries.

Due to the rich anastomotic network that exists at the cheek, extensive collateral flow is ensured even from adjacent vascular territories. This enables the cheek to provide safely all types of local flaps wherever they will be based. Hence the decision on choosing what type and where to base a cheek flap accounts more in the factors out of the strict vascular anatomy.

5.2.2 Danger Zones of the Facial Nerve at the Cheek

The facial nerve is fully protected, without any risk during flap surgery, as long as it remains within the parotis, forming its plexus. The terminal branches exit the anterior margin of the parotis, as already mentioned, approximately 4 cm anterior to the tragus along the transverse axis of the zygomatic arch (Wilhelmi et al. 2003). As the branches of the facial nerve travel through the fascial layers, they course to superficial planes in predicted areas which constitute zones where the nerve is in increased jeopardy during surgery (Fig. 5.34).

Fig. 5.34

Zones at risk of the facial nerve at the cheek. Red indicates the zones where the facial nerve is at great risk. Purple indicates the zone where the facial nerve is at a relative risk

The danger zone where the temporal branch is in great risk is the zone where it crosses the zygomatic arch. This zone with high rate of accuracy corresponds to the middle third of the zygomatic arch.

The marginal mandibular branch(es) is in great risk within a zone 2 cm above and 3 cm below the inferior mandibular border extending at the buccal and submandibular areas, and its frontal tip curves above the inferior border of the mandible at the anterior border of the masseter muscle (location of facial artery).

The buccal branch is in a relative risk as long as it travels in a deep plane and is at risk of injury more frequently in flap elevation at the sub-SMAS plane (see below). The buccal branch, either one or two, is expected to be found at the buccal area usually in a zone of 1 cm above and 1 cm below the line that connects the oral commissure to the tragus.

5.2.3 Flap Elevation Concerning Anatomic Planes

A flap derived from the cheek can be raised in the subcutaneous level or in a deeper level below the SMAS layer.

5.2.3.1 Subcutaneous Dissection Plane

Most of the flaps that are derived from the cheek are elevated at the subcutaneous plane (Fig. 5.35). This is the safest plane of elevation, so far as all of the vital anatomic structures lie beneath the SMAS.

Fig. 5.35

Dissection in the subcutaneous plane

The flap consists of skin and subcutaneous tissue and is raised by sharp dissection. Several perforating vessels coming from deep to the skin are encountered and transected but bleeding is easily controlled by cauterization.

The thickness of the flap depends not only on the depth of the excised area, thus the needed volume that has to be restored, but also of the extent of the flap that has to be raised. Small flaps can be raised just dissecting between the subcutaneous fat, leaving a portion of fat below the skin and a portion above the SMAS. Given that almost most of the flaps that are derived from the cheek are of random pattern, those of great extent must be elevated in a deep subcutaneous level, thick enough to include enhanced vascular supply. Even though the subcutaneous plane is a safe plane, when dissecting deep one must be cautious not to change by mistake the dissection plane and to have in mind exactly what might run beneath the dissection area. SMAS is not clearly identifiable in every cheek unit; neither the subcutaneous layer is of same thickness in every cheek subunit and differs also among the individuals. The course and the depth of the facial nerve at every cheek subunit must be constantly considered even if the dissection is subcutaneous.

At the infraorbital the subcutaneous fat is very thin and the dissection plane lies at the level over the orbicularis oculi muscle with the final branches of the zygomatic and buccal branches of the facial nerve well protected as they run to its undersurface. At the zygomatic subunit, at its anterior third, the malar fat pad facilitates the subcutaneous dissection, but moving posterior the subcutaneous fat thins and the frontal branch of the facial nerve crosses the mid-third of the zygomatic arch. Although the encountered fasciae of that area cover the frontal nerve, the fusion of planes at this level risks inadvertent nerve injury. At the parotid subunit, no danger for the facial nerve exists as it is well protected by the parotid gland. At the buccal subunit, the buccal branches of the facial nerve are in relative danger when dissecting at a deep subcutaneous plane. Even though the buccal branches are protected by the overlying parotidomasseteric fascia and SMAS, the SMAS might become very thin at this area and dissection must proceed with care so as to avoid an accidental transition of the dissection plane to a deeper one. At the inferior border of the buccal subunit, the marginal nerve is protected by the platysma and the deep cervical fascia but the subcutaneous dissection must be always performed with great caution. As the buccal subunit transitions to the nasolabial subunit, the presence of the nasolabial fat pad makes the subcutaneous dissection very easy and safe. Having in mind the course of the facial nerve is of paramount importance even when dissecting through the subcutaneous fat, especially where it crosses very superficially (lower border of mandible, zygomatic arch) as it is easy to harm. The retaining ligaments that are encountered in the region where a cheek flap is raised are felt as resistance in flap elevation and must be released by sharp dissection.

5.2.3.2 Deep (Sub-SMAS) Dissection Plane

It has been proven that the SMAS is not an avascular layer as it was believed but contains arterial vascularity within its mass from branches of the perforators that pass through it on their perpendicular way to the subdermal plexus (in contrast the SMAS does not contain veins) (Schaverien et al. 2009).

In certain circumstances like in patients with microcirculation deficiency (smokers, diabetics, those with peripheral artery disease and radiation in head and neck) and where a large flap has to be elevated, deep dissection under the SMAS layer (Fig. 5.36), similar to the deep-plane face-lift, adds perfusion to the overlying skin and increases flap mobility. This dissection comes in question in large rotation flaps where large areas of cheek skin have to be elevated with or without a neck extension (cervicofacial flap, see Chap. 8) or a thoracic extension (facial cervicothoracic flap, see Chap. 9). The flap is then termed as composite or deep-plane flap. The deep-plane flap (composite) is actually an implementation of the deep-plane rhytidectomy as was described by Hamra (1990). The deep-plane flap was first described by Barton and Zilmer (1982), but was popularized by Kroll et al. (1994) and focused attention furthermore (Becker and Langford 1996; Longaker et al. 1997; Delay et al. 1999; Tan and MacKinnon 2006).

Fig. 5.36

Dissection in the deep plane

This plane enhances the flap viability and thickness but puts the facial nerve at risk of injury, needing meticulous and very careful dissection. Precisely, the deep-plane dissection is a real sub-SMAS dissection only where SMAS exists.

Elevation starts with sharp preauricular dissection; thus the SMAS is adherent to the underlying parotidomasseteric fascia. Usually the preauricular incision starts as subcutaneous for about 1–2 cm and then deepens to the sub-SMAS plane, avoiding this adherent zone. At this stage the facial nerve and its plexus are well protected deep to the parotid substance. The parotid-cutaneous ligament is felt as resistance and is released. Anterior to the border of the parotis, the dissection proceeds bluntly over the parotidomasseteric fascia. The underlying buccal and zygomatic branches of the facial nerve, the parotid duct, and the outer surface of the buccal fat may be found to be glistening. The fascia is thin and clear and protrudes beneath the parotidomasseteric fascia. At the lower half of the masseter muscle, the sub-SMAS dissection proceeds more easily and quickly by bluntly dissecting in the areolar tissue plane that overlies the parotidomasseteric fascia and was defined by Mendelson et al. (2008) as “the premasseter space.” The platysma muscle, due to its variable extent and development, will not be found in a standard area during this step of dissection. The deep dissection proceeds deep to the platysma muscle, which constitutes the SMAS continuation. Due to the fact that this type of dissection concerns rotation flaps that extend also inferiorly to the neck, it is implied that the platysma muscle has been already found at the neck and raised with the neck part of the composite flap.

Fibrous septa of the masseteric ligament that are found are freed up and dissection continues. Reaching the lower anterior border of the masseter is the danger zone of the marginal mandibular branch of the facial nerve. As already mentioned near the point where the facial artery curves around the mandibular border, the marginal nerve penetrates the parotidomasseteric fascia or its neck continuation: The investing layer of the deep cervical fascia becomes more superficial and continues immediately deep to the platysma crossing the facial vessels (Owsley and Agarwal 2008). Here dissection is performed bluntly with extreme caution and the nerve must be protected. If dissection needs to continue further medially, the mandibular ligament has to be released.

At the upper part close to and specifically over the zygomatic arch, the dissection must transition to a subcutaneous plane. This protects the rami of the frontal branch from injury, as they cross its mid-third from deep to superficial fascial planes, ingrown within the temporoparietal fascia. Moving forward the origin and the lateral border of the zygomaticus major muscle is reached (identification helped by the line proposed by Tremolada, see above) and dissection proceeds above the muscle. Maintaining the dissection plane superficial or subcutaneous over the zygomaticus major muscle, the zygomatic branches of the facial nerve are avoided and protected as they travel on the deep muscle surface. Depending on the needed flap extent, the zygomatic retaining ligaments are released and dissection remains at the same level over the zygomatic muscles. At the periorbital zone, dissection can be performed over the orbicularis oculi muscle and not under it, as it is done in deep rhytidectomies. Thus the final branches of the zygomatic and buccal branches of the facial nerve are well protected as they run to its undersurface.

5.2.4 Rhomboid Flaps

The rhomboid flaps can be used to close small- and moderate-sized defects located at every subunit of the cheek. Even though the rhomboid flap is a random pattern flap, vascularity is never a problem, and at any axis the flap is arranged, it always survives. When creating the rhomboid defect, the flap limb can be derived from four positions around it. The decision on which of the four alternatives will be used must be based upon the tissue availability and maximal laxity of the chosen donor site and positioning of scars as possible along the relaxed skin tension lines. For defects that lie at the periphery of the cheek, the options are restricted to the presence of facial features, like the eyelids, lips, nose, and auricle, and special care must be given not to distort their normal position.

5.2.4.1 Rhomboid Flap at Reconstruction of the Nasolabial Alar Base Area

The patient presented had a nevus at the upper nasolabial fold in close proximity to the alar lobule (Fig. 5.37a, b). The rhomboid flap is outlined having its base superiorly (Fig. 5.37c, d). The lesion is excised in rhomboid manner creating a small defect (Fig. 5.37e). The flap is undermined in the subcutaneous plane (Fig. 5.37f) and is controlled if it reaches the defect without tension (Fig. 5.37g). A key suture is placed and the donor site is closed firstly (Fig. 5.37h). The flap is sutured in place without tension and the restoration is completed without any distortion. A great part of the suture line is positioned parallel to the nasolabial fold and to the alar-facial sulcus (Fig. 5.37i).

Fig. 5.37

(a, b) A nevus located at the upper nasolabial fold close to the alar lobule. (c, d) Rhomboid flap outlined. (e) Excision of the lesion. (f) Flap raised. (g) Flap transferred to the defect without tension. (h) Closure of the donor site. (i) Final closure

5.2.4.2 Rhomboid Flap at Reconstruction of the Infraorbital Area

In the presented case (Fig. 5.38a, b), a basal cell carcinoma is located at the infraorbital subunit. The risk in this area involves the distortion of the lower eyelid from the positioning of the rhomboid flap. Having that in mind, the rhomboid flap is placed in an axis that no (or minimal) tension will act on the eyelid (Fig. 5.38a, b). The lesion is excised in the usual manner (Fig. 5.38c). The superiorly based flap is raised in the subcutaneous plane (Fig. 5.38d) and reaches the defect without any tension or pulling down of the eyelid (Fig. 5.38e). The donor site is sutured (Fig. 5.38f) and the restoration is completed achieving the goals (Fig. 5.38g). Although the rhomboid flap is not a round flap, sometimes pincushioning may occur but it resolves quickly (Fig. 5.38h, i). Care is taken when selecting the appropriate position of the rhomboid flap so that two limbs of the multininear scar are camouflaged within natural rhytids. This leads to a very good aesthetic result, especially in small defects.

Fig. 5.38

(a, b) Lesion located at the infraorbital subunit and the rhomboid flap outlined. (c) Lesion excised. (d) The rhomboid flap raised. (e) Flap transferred to the defect. (f) Closure of the donor site. (g) Final restoration. (h) At 2 months postoperative, slight pincushioning is still present. (i) At 6 months postoperative, the pincushion has resolved and the result is excellent

5.2.4.3 Rhomboid Flap at Reconstruction of the Zygomatic Area

In the case presented (Fig. 5.39a), a rhomboid flap is used to cover a defect at the zygomatic subunit. The rhomboid flap is positioned so as to borrow preauricular tissue for the covering (Fig. 5.39b, c). The lesion is excised in the usual manner as a rhombus (Fig. 5.39d) and the flap is raised in the subcutaneous plane (Fig. 5.39e). This donor site may provide a slightly stiff flap that does not reach the recipient site immediately without tension (Fig. 5.39f). This problem resolves with ease by further undermining (the surrounding skin) (Fig. 5.39g). Donor site is closed at first (Fig. 5.39h) followed by suturing of the flap to the recipient site (Fig. 5.39i). The postoperative result shows a satisfactory restoration (Fig. 5.39j).

Fig. 5.39

(a) A lesion located at the zygomatic subunit. (b, c) Rhomboid flap outlined. (d) Lesion excised. (e) Flap raised. (f) Flap does not reach the defect at once and further undermining is needed. (g) The defect now is reached without tension. (h) Closure of the donor site. (i) Final restoration. (j) Postoperative result at 6 months

5.2.4.4 Rhomboid Flap at Reconstruction of the Lateral Canthal Area

Cheek skin can be transferred superiorly, by means of a rhomboid flap to reconstruct the lateral canthal area (Fig. 5.40a). The chosen rhomboid flap (Fig. 5.40b, c) takes advantage of the cheek skin laxity, produces minimal distortion, and does not put the frontal branch of the facial nerve at risk. The flap was raised in the subcutaneous plane and covered the defect (Fig. 5.40d).

Fig. 5.40

(a) A basal cell carcinoma at the lateral canthal area. (b, c) Outline of the rhomboid flap. (d) Flap sutured in place

5.2.4.5 Rhomboid Flap at Reconstruction of the Buccal Area

Medium and relatively large buccal defects can be reconstructed by transferring skin from the parotidomasseteric region by means of a rhomboid flap. Decision and careful planning is based upon the size of the defect and the availability of the needed skin from the parotidomasseteric region. If the defect is expected to be large, this approach is better to be considered in older patients with excessive skin laxity. Distortion of facial features is usually not the problem in small- and medium-sized defects that are located in a central position at the buccal area as long as they are not in close adjacency to the restoration.

Restriction in the orientation and the choice of the base when designing a rhomboid flap in this area is that vertical scars over the body of the mandible and the neck that may be produced must be avoided. A vertical incision on the neck may result in a scar that contracts causing a band and over the mandible may result in a scar that stretches becoming indrawn and difficult to correct (Jackson 2007). Thus, a rhomboid flap that transfers parotidomasseteric skin to the recipient site can be based either superiorly or inferiorly.

5.2.4.5.1 Superiorly Based Rhomboid Flap

A basal cell carcinoma is located at the lower buccal subunit in the patient presented (Fig. 5.41a). A superiorly based rhomboid flap is outlined so as to transfer skin from the parotidomasseteric subunit to close the defect, avoiding vertical scars over the mandibular body (Fig. 5.41b, c). Excision is performed and clear margins are revealed by frozen section biopsies (Fig. 5.41d). The flap is raised in a deep level, above the parotidomasseteric fascia (Fig. 5.41e). The flap was transferred to the defect (Fig. 5.41f) and the donor site closed primarily. In large defects, despite the skin laxity, some degree of tension is expected (Fig. 5.41g). The postoperative appearance at 3 months following surgery shows a satisfactory result (Fig. 5.41h, i).

Fig. 5.41

(a) Basal cell carcinoma at the buccal subunit of the cheek. (b, c) Rhomboid flap is outlined. (d) Excision performed. Platysma fibers are left intact at the base of the defect. (e) Flap raised above the parotidomasseteric fascia. (f) Flap transferred to the defect. (g) Immediate postoperative view. Despite the fair skin laxity, some degree of tension occurred. (h) Result at 3 months. (i) Symmetry and contour undisturbed

5.2.4.5.2 Inferiorly Based Rhomboid Flap

In a lesion located at the same region as in the previous patient but in a slightly higher position (Fig. 5.42a), an inferiorly based rhomboid flap can be used for the reconstruction (Fig. 5.42b, c). Closure of the inferiorly based rhomboid flap would be easier than if the flap was based superiorly, and this can be done in this situation as long as no vertical line lies on the mandibular body. The reconstruction was performed in the usual manner (Fig. 5.42d) resulting in a satisfactory closure (Fig. 5.42e).

Fig. 5.42

(a) A lesion at the buccal subunit. (b, c) The inferiorly based rhomboid flap outlined. (d) Rhomboid flap closure. (e) Postoperative appearance

5.2.5 Bilobed Flaps

The bilobed flap, a double transposition flap that is mostly used in the nose, can also be included in the armamentarium of cheek reconstruction based in the same principles. The flap is a random pattern flap and can resurface moderate-sized defects at the anterior cheek.

5.2.5.1 Bilobed Flap at Reconstruction of the Buccal Subunit

The patient presented in Fig. 5.43a had an ulcerative basal cell carcinoma of the buccal subunit of the cheek. The site of surgical excision is marked and the outline of a laterally based bilobed flap is created (Fig. 5.43b, c). The flap next to the defect will transfer skin of the lower cheek and is designed in an axis of 45° to the axis of the primary defect and at the same or slightly smaller size. The second flap is outlined at the upper part of the neck and is situated to an axis of approximately 45° to the axis of the first limb and smaller in size. Thus, the total angle of transposition of the bilobed flap is about 90°. The elasticity of the cheek skin allows a design of the bilobed flap of up to 90° for each flap and a total of 180°, easy rotation in cases where a so large rotation arc is needed. One Burow’s triangle is excised at the base of the flap and a second one at the apex of the second lobe to allow easier rotation without the formation of dog-ears.

Fig. 5.43

(a) Basal cell carcinoma of the buccal subunit. (b, c) Plan of excision and outline of the bilobed flap. (d) Flap elevated. (e) Flap transferred to defect. (f) Final closure of the defect. (g) Postoperative result at 1 year

The flap is elevated in the subcutaneous plane and rotated into position (Fig. 5.43d, e). It is sutured into position with ease (Fig. 5.43f). Usually there is no need of wide undermining, especially in old patients with loose skin. The bilobed flap does not need as extensive undermining and mobilization as the corresponding rotation flap that would be used in the same area, but leads to extensive and obvious scaring (Jackson 2007). This is obvious in the postoperative result where the multicircular nature of the scars cannot be camouflaged in linear natural creases (Fig. 5.43g).

5.2.5.2 Bilobed Flap at Reconstruction of the Upper Lip

In certain circumstances the bilobed flap provides many advantages that must be taken under consideration and seems to be an appropriate reconstructive solution. In the case presented, a basal cell carcinoma is located at the most anterior border of the cheek. The defect that will be created involves the nasolabial area and extends to the skin of the lateral region of the upper lip. The oral commissure is intact but in very close proximity to the defect. Any restoration must not interrupt its normal position. A bilobed flap in this situation provides to the upper lip similar skin tissue from the lower lip (Fig. 5.44a, b). It does not need extensive mobilization and most importantly ensures an undisturbed commissure. The oral commissure is balanced between the two lobes of the flap maintaining its normal position under neutralized tension.

Fig. 5.44

(a, b) Outline of the excision and the bilobed flap. (c) Lesion needed to be excised deep to the perioral muscles. (d) The first lobe is elevated superficial to the muscle layer. (e) First flap fits to the defect. (f) The flap fully mobilized based in a narrow pedicle. (g) Second lobe into place. (h) Immediate postoperative view. (i) Result at 9 months. No distortion of the commissure

The lesion is excised and free tumor margins are revealed by frozen section biopsies. Deep excision was performed to the level of perioral muscles (Fig. 5.44c). The first lobe of the flap is elevated at the plane just superficial to the perioral muscles so as to provide the needed bulk, leaving intact the modiolus and the muscles attached to it (Fig. 5.44d).

The flap is transposed to the recipient side (Fig. 5.44e). There is no need to excise the Burow’s triangle as long as a standing cone is not formed. The flap is raised as usual (Fig. 5.44f). Even though its base is relatively narrow, vascularization is ensured by the several perforators of the facial artery. The second lobe covers the secondary defect with ease (Fig. 5.44g). Final closure is achieved easily and without tension (Fig. 5.44h) and the final result is very satisfactory and there is no distortion of the oral commissure (Fig. 5.44i).

5.2.6 Subcutaneous Island Pedicle Flaps (V-Y Advancement Flaps)

The subcutaneous island pedicle flaps are a very useful tool in cheek reconstruction because they can be harvested from every cheek subunit that provides adequate mobility (usually from the nasolabial and malar area) and advanced to a variety of recipient sites of the cheek. The island pedicle flaps are advancement flaps that provide immediately adjacent to the defect skin excellent in texture and color match. These flaps are random pattern flaps and receive their blood supply from perforators that arise from deeper regional axial vessels and ascend to its subcutaneous pedicle. The concept of a detached from its surrounding tissues “skin island” as a flap that is based only to its underlying subcutaneous tissue was first introduced by Esser (1917) and popularized by Barron and Emmett (1965).

The placement of the flap base and the direction of the axis of movement depend on the area to be reconstructed and ideally must be determined by the direction of the RST lines.

5.2.6.1 Subcutaneous Island Pedicle Flap Horizontally Advanced at Reconstruction of the Infraorbital Area

This flap uses the looser cheek skin from the area lateral to the lesion and advances it medially to the infraorbital defect.

The outline of the island pedicle flap is presented in a patient with a small lesion located at the median part of the infraorbital area (Fig. 5.45a, b). The excision is outlined in rectangular form and the island flap is designed as a triangle in a length two times the dimension of the rectangle side. The flap borrows skin from the malar region, which provides excess and mobile tissue to transfer. The flap will be positioned on a horizontal axis and its trailing edges are placed along the RSTLs (Fig. 5.45c).

Fig. 5.45

(a, b) A lesion of the median suborbital region and the design of an island pedicle flap. (c) Incisions placed along RST lines. (d) The defect after excision of the lesion. (e) The skin island fully freed from the surrounding skin. (f, g) Undermining is performed in the subcutaneous plane (in a centrifugal dissection) in the whole perimeter of the flap, beveling slightly away from the pedicle. (h) Flap control. (i) Back-cutting of the leading edge of the flap in subcutaneous plane maximizes mobility and decreases tension to the lower eyelid. (j) Final closure in a V-Y fashion. The flap has been positioned horizontally (in a horizontal axis). (k) Result at 1 month after surgery. (l) No traction to the lower eyelid

The lesion is excised in healthy margins (Fig. 5.45d) and the skin island detached from the surrounding tissues (Fig. 5.45e). Mobilization of the flap is performed by blunt dissection through the subcutaneous plane in each of the flap sites and its apex for a distance of about 1.5 cm beveling slightly away from the pedicle (Fig. 5.45f, g). Performing dissection in this way, widens the flap base increasing the vascularization. During this stage fibrous bands that are encountered must be detached from the flap periphery providing thus additional mobility. During the deep subcutaneous dissection stage, special attention is given in the course of nerves and large vessels so as to protect and not damage them.

The flap is controlled continuously (Fig. 5.45h) if it sets without any tension, especially in this area where a downward tension to the lower eyelid may result to ectropion. If additional mobility is needed, a portion of the skin of the leading edge of the flap can be detached from the base by back-cut in a subcutaneous plane (Fig. 5.45i). This maneuver decreases tension and does not compromise the flap when at least the 60 % of the skin island, at this area, remains attached to the pedicle. The flap is advanced and sutured in a V-Y closure and its final position lies horizontally (Fig. 5.45j). The reconstruction resurfaced the defect successfully without any distortion of the eyelid (Fig. 5.45k, l).

5.2.6.2 Subcutaneous Island Pedicle Flap Obliquely Advanced at Reconstruction of the Malar Region

In the case presented in Fig. 5.46a, a lentigo maligna is located at the malar region. The island pedicle that is outlined has its movement axis in an oblique position as this is determined by the direction of the RST lines and its base located inferolaterally (Fig. 5.46b, c). The length of the triangle is twice the length of the rectangle side. The lesion was excised in clear margins (Fig. 5.46d) and the flap was undermined in the usual manner (Fig. 5.46e). The flap is sutured in place in a V-Y fashion (Fig. 5.46f).

Fig. 5.46

(a) Lesion at the malar region. (b, c) Outline of the island pedicle flap. (d) Lesion excised. (e). The flap undermined. (f) Final closure in a V-Y fashion. The flap has been positioned obliquely (in an oblique axis)

5.2.6.3 Subcutaneous Island Pedicle Flap Vertically Advanced at Reconstruction of the Superomedial Cheek Area

In defects that are located at the superomedial cheek aspect (even immediately below the lower eyelid) or even higher at the medial canthal area, a vertical, inferiorly based island flap can be used successfully. In a basal cell carcinoma located at the superomedial part of the cheek (Fig. 5.47a), a vertical island pedicle flap was planned to close the defect (Fig. 5.47b, c). The trailing edges of the flap were positioned parallel to the nasal sidewall and the nasolabial groove defining its vertical orientation. Again the flap length is 2 times the length of the rectangle side. The flap was undermined as usual, advanced superiorly, and covered the defect (Fig. 5.47d). Gravity is not a problem and a risk of ectropion is minimal. The way that the donor site is closed supports the elevated flap, and withstands gravitational forces with its vertical orientation.

Fig. 5.47

(a) Pigmented basal cell carcinoma. (b, c) Vertical island pedicle flap outlined. (d) Final closure in a V-Y fashion. The flap has been positioned in a vertical axis

5.2.6.4 Subcutaneous Island Pedicle Flap Vertically Advanced at Reconstruction of the Buccal Subunit

The characteristics of the buccal subunit allow the design and advancement of large subcutaneous island pedicle flaps (Fig. 5.48). The advancement axis of flap here is almost vertical as it is imposed by the direction of the RSTLs at the buccal subunit.

Fig. 5.48

(a–c). Large subcutaneous island pedicle flaps can be derived from the buccal subunit of the cheek. The direction of the RSTLs determines the axis of movement

5.2.6.5 Double Island Pedicle Flap at Reconstruction of the Zygomatic Area

Two island pedicle flaps, evenly opposed or angled as in the case presented, can be created so as to share a defect. Two adjacent nevi located at the zygomatic and temporal subunit were excised, and the total defect was reconstructed by a double island pedicle flap (Fig. 5.49a, b). Dissection of the flaps was done with extreme care preserving the branches of the facial nerve. One flap advanced skin from the preauricular area while the other from the temporal area. The two flaps were sutured in place sharing the produced defect (Fig. 5.49c). The final result is functionally and aesthetically satisfactory (Fig. 5.49d, e).

Fig. 5.49

(a, b) Two angled island pedicle flaps. (c) The two flaps shared the defect. (d, e) Result at 2 months and at 1 year. No impairment of the facial nerve occurred

5.2.7 Nasolabial Subcutaneous Island Pedicle Flaps

When an island pedicle flap has its subcutaneous base at the nasolabial area (along the course of the facial artery) and its axis along to it, it is then termed as nasolabial island flap. An island flap situated at this position reclaims all of the advantages of this area: availability of elastic and mobile skin and subcutaneous tissue, generous blood supply through perforators of the facial artery, and scar camouflage. Moreover, due to the fact that the closure of the produced donor defect of an island flap needs minor secondary tissue movement, important nearby facial features (upper and lower lip, ala, commissure) remain undistorted even when large flaps are raised.

5.2.7.1 Nasolabial Subcutaneous Island Pedicle Flap at Reconstruction of the Medial Cheek-Upper Lip-Alar Junction Area

In the patient presented in Fig. 5.50a, a recurrent basal cell carcinoma is located at the junction of the cheek-upper lip-alar base, presenting in cystic form and a deeply invasive nodule. The patient had a nasal restoration of the alar lobule and rim 1 year ago with an unclear, superiorly based nasolabial flap.

Fig. 5.50

(a) A recurrent basal cell carcinoma. (b, c) Excision lines and a nasolabial island flap outlined. (d) Excision performed leaving a deep defect. (e) Mobilization of the flap. (f) Bulky tissue is advanced to the defect. (g) Immediate postoperative view. (h, i) Satisfactory result at 2 months postoperative. Lip retains its position and function. (j) Contour is fully imputed. No attempt to restore the previously restored nasal ala was made at this stage. Scars are hidden within the RST lines

Despite the fact that a nasolabial flap had already been used at the first operation, a new one is outlined (Fig. 5.50b, c) but longer than in the usual manner so as to widen the vascular plexus beyond the former, thereby catching as many as possible of the several perforators of the facial artery that are encountered densely near the mouth angle and enhance its robustness. This description concerns to the conventional nasolabial flap and not to the flaps that are based in only one single facial perforator as facial artery perforator flaps (Hofer et al. 2005) and is beyond the purpose of the present book.

Tumor excision was performed in a deep tissue plane (Fig. 5.50d), and tumor margins were revealed by frozen section biopsies. Thus, this reconstruction requires not only resurface of the skin but also restoration of the bulk. The thickness of the subcutaneous layer at the nasolabial area can provide this needed amount of tissue.

The flap was undermined, slightly beveling, around its subcutaneous pedicle for about a 2–2.5 cm distance (Fig. 5.50e). Dissection is carried out bluntly and sharply down to the level of the cheek muscles. Fibrous bands (from the pedicle) to the surrounding fat are encountered and released.

Additional mobility is gained if a portion of the skin of the periphery of the flap is detached from the pedicle by back-cut in the subcutaneous plane. This maneuver decreases tension and does not compromise the flap when at least the central third of the skin island remains attached to the pedicle. The subcutaneous pedicle of an island flap can be narrowed at this degree and still perfuse the skin island only in the nasolabial area, where the facial artery encounters as already mentioned numerous perforators. The nasolabial island flap was advanced to the defect (Fig. 5.50f) and sutured in place without tension (Fig. 5.50g). The postoperative appearance at 2 months following surgery shows a satisfactory functional and aesthetic result (Fig. 5.50h–j).

5.2.7.2 Nasolabial Island Flap at Reconstruction of the Medial Canthal-Nasal Side Area

The nasolabial flap can reach even more superiorly located midsized defects of the medial canthal region and the nasal side. The patient seen in this case had an ulcerative basal cell carcinoma of the medial canthal-nasal area. The proposed excision and the nasolabial flap were outlined (Fig. 5.51a, b). The lesion was excised and clear margins were revealed by frozen section biopsies (Fig. 5.51c). A part of the underlying periosteum had to be sacrificed, but the remainder provided a sufficiently vascularized bony bed. The medial canthal tendon was preserved. After undermining, the flap was advanced superiorly, covered the defect, and was sutured in place (Fig. 5.51d).

Fig. 5.51

(a, b) Outline of the nasolabial flap. (c) The defect after excision. The lower edge of the anterior limb of the medial canthal tendon is pointed. (d) Flap sutured in place

5.2.8 Cheek Rotation Flaps

The wide surface of the cheek and its tissue laxity constitutes an ideal donor site for rotation flaps of various extents. Cheek rotation flaps are very reliable random pattern flaps as long as a strong vascular plexus and a wide base support them. The arc length of the rotation flap at the cheek adheres to the general rules of the rotation flap design but it is determined by the variable skin laxity of the different cheek subunits and must be individualized after thorough examination of the skin properties.

5.2.8.1 Deep-Plane Cheek Rotation Flap Inferiorly Based

The patient seen at this case had a recurrent basal cell carcinoma previously treated by surgery and radiotherapy (Fig. 5.52a). The rotation flap was designed having its base inferiorly (Fig. 5.52b). The lesion was excised as a triangle and clear margins were revealed by frozen section biopsies (Fig. 5.52c). The lesion was excised at the deep subcutaneous level but the flap elevation transitions in a deep, sub-SMAS, level (Fig. 5.52d). Previous radiation had impaired the microcirculation, and the deep dissection plane increases the vascularity of the flap. The flap was rotated and sutured in place with ease (Fig. 5.52e). The postoperative result at 4 months following surgery is shown in Fig. 5.52f.

Fig. 5.52

(a) A recurrent basal cell carcinoma located at the cheek. (b) The flap outlined. (c) The defect is triangulated and restoration is performed with an inferiorly based cheek rotation flap. (d) Flap is raised in the deep plane. (e). Rotation flap sutured in place. (f) Postoperative result at 4 months

5.2.8.2 Cheek Rotation Flap Medially Based at Reconstruction of the Upper Buccal Subunit

The buccal subunit provides rotation flaps that usually can be designed with an arc shorter than usual due to the laxity of this region. Such a case is seen in Fig. 5.53a–c. The lesion was excised in clear margins (Fig. 5.53d) and the flap was elevated in the subcutaneous plane. There is no risk of damage for the buccal branches of the facial nerve. The flap fills the surgical defect without tension (Fig. 5.53e) accomplishing an excellent result (Fig. 5.53f).

Fig. 5.53

(a) A lesion at the upper buccal subunit. (b, c) A rotation flap with a relative short arc is able to reach the defect. (d) The lesion is excised as a triangle. (e) The rotation flap sutured in place. (f) Result at 12 months

5.2.8.3 Cheek Rotation Flap Medially Based at Reconstruction of the Lower Buccal Subunit

The same flap as in the previous case, also with a short arc, can be placed in a more inferior position to reconstruct a defect at the lower buccal subunit (Fig. 5.54a, b). Even though the flap is raised at the subcutaneous plane, meticulous dissection must be performed as long as the flap here is situated at the danger zone of the marginal mandibular branch of the facial nerve (Fig. 5.54c). The rotation flap was dissected, was mobilized, and reached the defect (Fig. 5.54d). Final suturing was performed without tension (Fig. 5.54f), and the early postoperative result was satisfactory without any facial nerve damage (Fig. 5.54g).

Fig. 5.54

(a) A basal cell carcinoma located at the lower buccal subunit. (b) The rotation flap outlined. (c) The flap is situated at the danger zone of the marginal mandibular branch of the facial nerve. (d) Flap raised at the subcutaneous level. (e) The flap fully mobilized to reach the defect without tension. (f) Immediate postoperative view. (g) Result at 2 months

5.2.8.4 Cheek Rotation Flap Inferiorly Based at Reconstruction of the Lateral Canthal Area

The patient presented in Fig. 5.55a had a basal cell carcinoma located at the lateral canthal region. The rotation flap that was used in this case was designed with a relative long arc (Fig. 5.55b, c). This was determined by the laxity of the donor site aiming in a flap without tension that could distort the recipient area. The flap was dissected in a superficial subcutaneous plane (Fig. 5.55d), with extreme care over the zygomatic arch, so as to avoid damage of the frontal branch of the facial nerve. The rotation flap reached the defect tensionless without causing any distortion (Fig. 5.55e).

Fig. 5.55

(a) A basal cell carcinoma located at the lateral canthal region. (b, c) Outline of an inferiorly based rotation flap with a relative long arc. (d) Elevation of the flap at the superficial subcutaneous plane. (e) The flap is sutured in place without any tension

5.2.8.5 Cheek Rotation Flap Laterally Based at Reconstruction of the Infraorbital Subunit (Imre Flap)

Defects of the infraorbital subunit of the cheek can be closed by a laterally based rotation according to the initial description of Imre (1928) that transfers tissue from the nasolabial subunit (Fig. 5.56a, b). The flap is raised in the subcutaneous plane. It is undermined in that extent where it reaches the defect without tension and is sutured in place (Fig. 5.56c). As with any incision that is made in the infraorbital crease, edema of the eyelid may occur as a complication in the early postoperative period, which resolves within the first year (Fig. 5.56d, e).

Fig. 5.56

(a, b) The defect is triangulated and from its base a curved incision is outlined along the nasolabial crease. A small Burow’s triangle is excised at the inferior distal end. (c) Flap sutured in place. (d) Result at 1 month. Edema of the lower lid is present. (e) Result at 1 year. Lower lid edema is completely resolved

5.2.9 Cheek Rotation-Advancement Flaps

5.2.9.1 Mustardé Flap

Mustardé originally described this flap for the reconstruction of wide lower eyelid defects (Mustardé 1991). However, it is a very useful rotation-advancement flap that can be used to transfer skin from the lateral cheek-resurfacing medium to large defects that are located at the infraorbital region.

The patient presented in Fig. 5.57a had a large cystic basal cell carcinoma of the infraorbital subunit of the cheek. The defect is triangulated and the Mustardé flap is outlined (Fig. 5.57b, c). The incision line of the flap starts from the base of the triangle running laterally and curves upward and outward from the lateral canthus. This is done to anchor the flap in a level superior to the eyelid reducing the pull of the flap to it and avoiding thus ectropion formation. The incision line then descends into the preauricular skin crease and typically ends to the earlobe. If additional mobilization will be needed, the incision can be extended around the ear lobule into the retroauricular region and ending at the neck. The tumor is excised above the level of orbicularis oculi muscle and clear margins are revealed by frozen section (Fig. 5.57d).

Fig. 5.57

(a) Cystic basal carcinoma of the infraorbital region. (b, c) Excision of the lesion in a triangular form and the outline of the Mustardé flap. (d) Tumor excised. The orbicularis oculi muscle is intact. (e) The flap is elevated in the subcutaneous (face-lift) plane. (f) Flap sutured in place. Deep sutures anchor the flap to periosteum. (g) Postoperative result at 6 months

The undermining of the flap is performed in the subcutaneous plane (Fig. 5.57e), and elevation starts from its superior and medial part. Even though elevation of the flap is performed above the SMAS layer, great attention must be given not to lose that plane when dissecting over the zygomatic arch so far as the frontal branch of the facial nerve crosses the zygomatic arch and lies very superficially. Elevation continues over the parotidomasseteric area at the base of the flap usually up to the mandibular angle in the same face-lift plane, and almost the whole cheek is undermined and raised. The flap is checked if it rotates reaching the recipient site without any tension. This is of great importance because even a small degree of tension will act on the lid drawing it down and leading to severe ectropion. If despite the wide undermining the flap fits under tension, additional mobilization is gained from its retroauricular and neck extension.

After adequate mobilization has been achieved, the flap is sutured in place (Fig. 5.57f). The flap is anchored with absorbable subcutaneous sutures to the periosteum of the frontal process of the maxilla and to the periosteum of the supraorbital rim and the zygomatic bone. Mobilization of the skin of the temple may be also needed to facilitate donor site closure. The postoperative result at 6 months shows a satisfactory reconstruction (Fig. 5.57g). Of the abovementioned preventive measures taken, minimal pulling down of the lower lid often occurs but seldom needs secondary correction.

5.2.9.2 Mustardé Flap for Malar Reconstruction

The patient presented in Fig. 5.58a had a basal cell carcinoma of the lateral infraorbital region. According to the principles of the original Mustardé flap, with a same design, a laterally positioned flap can be used to reconstruct the defect located just lateral to the infraorbital subunit. The defect is triangulated and the flap is outlined (Fig. 5.58b, c). The flap is elevated in the usual manner, deep to the subcutaneous plane, and resurfaces the defect with ease (Fig. 5.58d, e). The use of this flap results in a very satisfactory postoperative appearance (Fig. 5.58f).

Fig. 5.58

(a) A basal cell carcinoma located just lateral to the infraorbital subunit of the cheek. (b, c) The flap outlined. (d) Flap elevated. (e) Flap in place. (f) Result at 9 months postoperatively

5.2.9.3 Cheek Rotation-Advancement Flap Inferiorly Based

Preauricular skin can be transferred medially to close defects by means of inferiorly based cheek rotation-advancement flaps. At the patient presented in Fig. 5.59a–c, an inferiorly based cheek rotation-advancement flap was used to reconstruct a small defect of the zygomatic subunit.

Fig. 5.59

(a, b) A small inferiorly based cheek rotation-advancement flap is used to reconstruct a defect of the zygomatic subunit. (c) Flap sutured in place

5.2.9.4 Deep-Plane Cheek Rotation-Advancement Flap Anteriorly Based

A patient with microvascular disease exhibits a large basal cell carcinoma located at the zygomatic subunit of the cheek (Fig. 5.60a). Excision of the lesion and reconstruction of a cheek rotation-advancement anteriorly based flap and raised in the deep plane was planned. The flap was outlined (Fig. 5.60b, c). It slightly extends to the upper neck in a quite similar to the cervicofacial flap (see Chap. 8) manner. The lesion was excised in a circular manner in tumor free margins (Fig. 5.60d). The frontal branch of the facial nerve lies deeper of the excision plane. A triangle was excised triangulating the defect (Fig. 5.60e).

Fig. 5.60

(a) A large basal cell carcinoma located at the zygomatic subunit of the cheek. (b, c) Flap design. The flap is extended to the upper neck. (d) Excision of the lesion. (e) Defect triangulated. (f) Sub-SMAS elevation of the flap. The platysma muscle is incorporated on the undersurface of the flap and the parotidomasseteric fascia, left in place, very thin and shiny. (g) A thick and robust flap was raised. (h) Flap sutured in place. (i, j) Result at 6 months

The lesion was excised at the deep subcutaneous level but the flap elevation transitioned from cephalad to caudal in a deep, sub-SMAS, level and a thick and robust flap was raised (Fig. 5.60f, g). The flap was sutured in place without tension resurfacing the defect (Fig. 5.60h). The final result is satisfactory, as long as symmetry and contour are maintained and the scars remain quite hidden (Fig. 5.60i, j).

5.2.10 Cheek Flaps for Nose and Lip Reconstruction

The cheek can also be a donor site and transfer tissue in nasal reconstruction. This includes usually the reconstruction of the nasal lobule, the nasal lining, the medial canthal region as presented above, and in selected cases the nasal side.

5.2.10.1 Island Pedicle Flap at Reconstruction of the Upper Nasal Sidewall

An island pedicle flap donated from the cheek can reconstruct midsized defects of the nasal sidewall. Although this is not the ideal reconstructive option (shallowing of nose-cheek junction will occur), the island pedicle flap provides an extremely viable, quick, and one-flap solution in selected patients.

The patient seen in Fig. 5.61 had an ulcerative basal cell carcinoma of the nose that led to a through and through nasal defect. The medical status of the patient imposed a short lasting operation and reconstruction with a well-vascularized flap. Moreover at this area there is no need to reconstruct any deep (mucosal or bony) structure. A flap needs only to cover the defect overlapping and anchored to a zone of healthy bone margin. Thus, it must survive over this narrow (weak vascular) bed, and with time the bare undersurface reepithelializes without any contraction. The designed island flap fulfills these demands and is perfused by a rich anastomotic network from the several arteries that are distributed to its base and was chosen for the restoration (Fig. 5.61a, b). After undermining in the way already described, the flap was advanced superiorly, covered the through and through defect, and was sutured in place (Fig. 5.61c). The restoration results in a flattening in some degree of the nasal-facial line (Fig. 5.61d).

Fig. 5.61

(a, b) Outline of the flap. (c) Flap in position. (d) Final result

5.2.10.2 Island Pedicle Flap at Reconstruction of the Lower Nasal Side

In small nasal side defects that are located just next to a shallow nose-cheek junction, an island pedicle flap from the nearby nasolabial cheek can give a satisfactory result.

The patient demonstrated in Fig. 5.62 had a small nevus located at the nasal side. The proposed defect was too small and did not involve the lobule and the nose-cheek junction appeared to be shallow. An island pedicle flap was designed from the vicinity of the nasolabial fold with a length twice the length of the side of the defect (Fig. 5.62a, b). The flap was advanced and closure was achieved in a V-Y fashion without any distortion (Fig. 5.62c). The flap is almost fully camouflaged as being the upper part of the nasolabial fold. This reconstruction must be avoided in larger defects.

Fig. 5.62

(a, b) A small nevus at the nose-cheek junction. (c) Flap sutured in place

5.2.10.3 Cheek Advancement Flap at Reconstruction of the Nasal Side

Cheek advancement flaps horizontal to the dorsal sidewall of the nose have been used in the past. After the introduction of the nasal subunit principle, the maintenance of the nasofacial sulcus that is distorted by this method gained interest. The excision is outlined as a square and the flap is outlined with the incision lines running laterally to the cheek and parallel to natural creases. The base of the flap is slightly wider than its leading edge and its length twice the length of the defect (Fig. 5.63a, b). Two small triangles at its base are excised to prevent dog-ear formation.

Fig. 5.63

(a, b) Cheek advancement flap outlined. (c) Flap advanced and sutured in place. (d) Result at 5 months

The flap is advanced to the defect and sutured in place. The upper limb of the flap does not exercise any tension to the lower lid, and the lower limb is placed at the nasolabial line (Fig. 5.63c). The postoperative result shows a satisfactory result with minimal distortion of the nasal-facial sulcus (Fig. 5.63d).

From the perspective of a subunit approach, this flap is ideal to resurface the cheek in a combined nose-cheek defect up to the nose-cheek junction and to resurface the rest of the nose defect with a second flap or a skin graft (Jackson 2007).

5.2.10.4 Nasolabial Flaps in Nasal Reconstruction

A nasolabial flap can be used in nasal reconstruction for its lateral wall and ala but also for the columella usually as a two-stage pedicled flap.

The nasolabial flap, even widespread in nasal reconstruction, never gives an excellent result at once because it almost always leads to pincushioning and flattening of the nasofacial sulcus. However, it is easy to design and to perform, is very reliable, and seldom gets lost. Thus, it has been characterized as a favorite flap of inexperienced surgeons (Jackson 1985). Despite its disadvantages, it remains a very useful and extremely safe tool especially in old patients with comorbidities and reduced healing reserves. As mentioned this type of reconstruction is very quick to perform, needing reduced operating time, is ideal for patients with a poor medical history, and can resurface quite large nasal defects with minimal risk. If the flap can be thinned safely, this will reduce the possibility of pincushioning. Otherwise, the produced pincushion can be corrected by a debulking procedure in a second time but this often is denied by the old patients that do not have special aesthetic demands. If aesthetics comes in first priority, a rather different reconstructive solution must be considered. In an attempt to reduce the possibility of the pincushioning and the shallowing of the nasofacial groove, wide undermining of the donor and defect sites, significant thinning of the flap, excision of large Burow’s triangle that improves the transposition movement, and the application of periosteal sutures to maintain the nasofacial sulcus have been proposed (Zitelli 1990).

A nasolabial flap that reconstructs the nose is based most of the time superiorly but can also be based inferiorly. Despite the fact that the nasolabial flap is not the optimal solution in external nasal coverage, in contrary it provides a big amount of tissue for successful internal nasal lining in the fashion of a turn-over flap.

5.2.10.4.1 Superiorly Based Nasolabial Flap for Reconstruction of Medial Alar Defects

In the case presented, a patient has a basal cell carcinoma at the medial third of the ala that involves also the junction of three nasal subunits (Fig. 5.64a).

Fig. 5.64

(a) A basal cell carcinoma at the junction of the alar tip sidewall subunits of the nose. (b, c) The area of the proposed excision and the superiorly based nasolabial flap is outlined. (d) The surgical defect. The underlying lateral crus of the alar cartilage is intact. (e) The flap raised in a deep level. The levator labii superioris alaeque nasi muscle is clearly seen. (f) Flap transpositioned to the defect. (g) The flap is sutured in place

The nasolabial flap is outlined having its base superiorly and two Burow’s triangles are outlined to be excised if needed (Fig. 5.64b, c). The needed length of the flap is determined by measuring with a gauze. The flap is of random pattern and receives its blood supply due to its subcutaneous and subdermal plexus that is perfused from branches of vessels (nasal branches of infraorbital, angular, dorsal nasal) round its base. The lesion was excised in clear margins revealed by frozen section biopsies. The defect involved full-thickness skin and nasalis muscle and not the underlying lateral crus of the alar cartilage and its perichondrium (Fig. 5.64d). The flap is raised in a deep level to gain enhanced vascularity due to the medical status of the patient (significant peripheral vascular disease) (Fig. 5.64e). The flap is transferred almost horizontally to reach the defect (Fig. 5.64f).

The flap was sutured in place covering the defect and the donor site was closed easily placing the closure line into the natural nasolabial line (Fig. 5.64g). No thinning of the flap was done at this stage so as not to compromise its vascularity.

5.2.10.4.2 Superiorly Based Nasolabial Flap for Reconstruction of Lateral Alar Defects

If the alar defect lies very close to the alar-facial sulcus and even a small skin portion of the junction has to be reconstructed, it becomes more difficult to restore the normal anatomy.

In the case presented, a basal cell carcinoma located at the lateral portion of the alar lobule just adjacent to the alar-cheek groove (Fig. 5.65a) is planned to be excised and the defect reconstructed with a nasolabial flap superiorly based (Fig. 5.65b, c). The arc of “rotation” in these situations is the minimum possible. The flap was undermined in the usual way, transferred to the recipient site, and sutured in place (Fig. 5.65d). The postoperative result shows that even the flap has not been pincushioned in a great degree; however, the alar-facial sulcus has been moderately flattened (Fig. 5.65e).

Fig. 5.65

(a) Lesion located at the alar lobule just adjacent to the alar-cheek sulcus. (b, c) A superiorly based nasolabial flap is outlined. (d) The flap sutured in place. (e) Result at 6 months

5.2.10.4.3 Superiorly Based Nasolabial Flap for Nasal Sidewall Reconstruction

Based on the same principles, the nasolabial can reconstruct sidewall defects of the nose. A basal cell carcinoma is located at the nasal sidewall in the patient seen in Fig. 5.66a. A superiorly based nasolabial flap is outlined in the usual manner but situated in a higher position than in the previous cases (Fig. 5.66b). The closure needs more undermining than in the lower positioned nasolabial flaps with the aim also to avoid extensive traction to the lower lid. After this has been done, the flap is sutured in place (Fig. 5.66c).

Fig. 5.66

(a) Basal cell carcinoma of the nasal sidewall. (b) Nasolabial flap outlined. (c) Flap sutured into position

5.2.10.5 Nasolabial Flaps as Turn-In Flaps in Nasal Lining

The nasolabial flap provides a big amount of tissue for successful internal nasal lining in lateral large through and through nasal defects in the fashion of a turn-over flap. In the case of Fig. 5.67, a large amount of tissue was needed to line the nose internally. A nasolabial turn-in flap was chosen as the best solution (Fig. 5.67a). The flap was incised to its whole perimeter in a manner of a skin island and then raised in the subcutaneous plane, leaving a subcutaneous pedicle at its base (Fig. 5.67b).

Fig. 5.67

(a) A one-stage nasolabial flap is outlined for internal nasal lining. (b) Flap raised and turned to the defect. (c) Internal nasal lining reconstruction completed

A strip of 4–5 mm of skin at its base adjacent to the defect was deepithelialized prior the final setting. This maneuver does not trap skin tissue that could lead to cyst formation. The flap was turned into place and sutured with the remained nasal mucosa (Fig. 5.67c).

5.2.10.6 Two-Stage Nasolabial Flap for Lip Skin Reconstruction

The nasolabial flap provides a great amount of tissue that can be used for the reconstruction of large lip skin defects. A basal cell carcinoma located at the lateral subunit of the upper lip is shown in the patient demonstrated in Fig. 5.68a. A superiorly based nasolabial flap is planned to reconstruct the defect (Fig. 5.68b, c). After excision in clear margins has completed, the flap is raised at the subcutaneous tissue level (Fig. 5.68d) and transposed medially to close the defect (Fig. 5.68e). The flap is sutured in place and the nasolabial defect is closed directly. The flap pedicle remains for a period of 2–3 weeks and at the second surgical stage is divided and the final restoration takes place (Fig. 5.68f).

Fig. 5.68

(a) Basal cell carcinoma of the upper lip. (b, c) The proposed excision and a superiorly based nasolabial flap are outlined. (d) The flap is elevated. (e) Transposition to the defect with ease final suturing. Pedicle remains for 2–3 weeks. (f) Pedicle divided

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(1)

Department of Anatomy, Medical School Democritus University of Thrace, Alexandroupolis, Evros, Greece

Abstract

Fig. 5.1

The boundaries of the cheek

Fig. 5.2

Cheek subunits

5.1 Layered Anatomy

The soft tissues and the fasciae of the cheek are arranged concentrically over the bony skeleton. From an anatomic and surgical point of view, these structures are layered as follows:

Skin

Subcutaneous tissue

Musculoaponeurotic layer (SMAS-mimic muscles)

Parotidomasseteric fascia

Buccal space and contents

Deep muscular layer

Retaining ligaments

Surgically important nerves and vessels travel through these layers often changing planes.

5.1.1 Skin

5.1.1.1 Skin and Cheek Subunits

5.1.1.1.1 Infraorbital Subunit

5.1.1.1.2 Zygomatic Subunit

5.1.1.1.3 Parotidomasseteric (Preauricular) Subunit

5.1.1.1.4 Buccal Subunit

5.1.1.1.5 Nasolabial Subunit

The relaxed skin tension lines (RSTLs) on the cheek run horizontally at its upper-medial part and curve in a vertical direction as they descend to its mid- and lower third (Fig. 5.3).

Fig. 5.3

Relaxed skin tension lines (RSTLs) at the cheek

5.1.2 Subcutaneous Layer

Fig. 5.4

Subcutaneous layer of the cheek and superficial fat pads

5.1.2.1 Superficial Fat Pads of the Cheek (Fig. 5.4)

The nasolabial fat pad extends lateral and parallel to the nasolabial crease and is responsible for the formation of the nasolabial fold.

The jowl fat pad is the most inferiorly situated fat pad and lying lateral to the depressor anguli oris muscle.

5.1.3 SMAS and Superficial Muscle Layer

The third layer of the cheek consisted of the SMAS and the superficial layer of the mimic muscles.

5.1.3.1 SMAS

Fig. 5.5

The SMAS in lateral face

5.1.3.2 Superficial Mimic Muscle Layer

5.1.3.2.1 Orbicularis Oculi Muscle

Fig. 5.6

The upper group of the superficial cheek muscles: orbicularis oculi, levator labii superioris alaeque nasi, levator labii superioris, zygomaticus minor, zygomaticus major

5.1.3.2.2 Suborbicularis Oculi Fat (SOOF)

Fig. 5.7

The SOOF. The buccal extension of the buccal fat pad is seen below the lip levators

5.1.3.2.3 Levator Labii Superioris Alaeque Nasi Muscle

5.1.3.2.4 Levator Labii Superioris Muscle

Branches of the facial and infraorbital arteries supply the muscle. Levator labii superioris is innervated by the zygomatic and buccal branches of the facial nerve.

Levator labii superioris muscle elevates the upper lip.

5.1.3.2.5 Zygomaticus Minor Muscle

The zygomaticus minor muscle has been found to be present in approximately 36–42 % of individuals (Pessa et al. 1998; Waller et al. 2008).

The superior labial branch of the facial artery supplies the muscle. Innervation is supplied by rami of the zygomatic and buccal branches of the facial nerve. It elevates the upper lip.

5.1.3.2.6 Zygomaticus Major Muscle

The zygomaticus major muscle (Fig. 5.6) originates from the zygomatic bone, anterior to the zygomaticotemporal suture and lateral to the origin of the zygomaticus minor muscle.

Fig. 5.8

Origin of zygomaticus major muscle (According to Tremolada et al. 1994)

The zygomaticus major runs in an oblique direction toward the angle of the mouth.

Its vascular supply comes from the superior labial branch of the facial artery. The muscle is innervated by rami of the zygomatic and buccal branches of the facial nerve.

This muscle belongs to the levator muscles of the oral commissure as it draws the angle of the mouth upward and laterally.

5.1.3.2.7 Risorius Muscle

Fig. 5.9

The lower group of the superficial cheek muscles

The superior labial branch of the facial artery supplies the risorius. Buccal branches of the facial nerve innervate the muscle. Risorius retracts the angle of the mouth laterally.

5.1.3.2.8 Platysma Muscle

The platysma muscle pulls the lower lip down and the corner of the mouth downward and laterally.

5.1.3.2.9 Depressor Anguli Oris Muscle

The depressor anguli oris muscle belongs to the depressor muscles of the oral commissure.

5.1.4 Parotidomasseteric Fascia

Fig. 5.10

The parotidomasseteric fascia and the parotid-cutaneous ligament

5.1.5 Buccal Space

Fig. 5.11

Buccal space and its contents

The facial artery courses through the buccal space at its anterior part while the facial vein is found slightly posterior.

5.1.6 Deep Muscle Layer

The deep muscle layer of the cheek consists of the masseter, buccinator, and levator anguli oris muscles.

5.1.6.1 Masseter Muscle

Fig. 5.12

Deep muscle layer of the cheek

The masseter primarily elevates the mandible to occlude the teeth.

5.1.6.2 Buccinator Muscle

The buccinator muscle (Fig. 5.12) is a thin and quadrilateral muscle that forms the base of the bucal space, and fills the gap between the maxilla and the mandible.

The uppermost fibers continue as fibers of the upper part of the orbicularis oris muscle and the lowermost fibers continue as fibers of the lower part of the orbicularis oris muscle.

The buccal branch of the facial nerve provides the motor innervation to the buccinator muscle.

The buccinator compresses the cheek and also acts to propel food during mastication, sucking, and whistling. It also participates in the lateral retraction of the oral commissure.

5.1.6.3 Levator Anguli Oris Muscle

5.1.7 Retaining Ligaments

The true ligaments of the cheek (Fig. 5.13) that arise from the osseous background of the cheek are the following.

Fig. 5.13

True retaining ligaments at the cheek

The zygomatic ligament (McGregor’s patch) originates as a series of fibrous septa from the periosteum at the junction of the zygomatic arch and zygomatic body just lateral to the zygomaticus major muscle.
The masseteric ligaments are found as they extend along the anterior border of the masseter muscle.
The mandibular ligament originates from the periosteum of the external surface of the mandibular body, 5 mm superiorly to the inferior edge and lateral to the depressor anguli oris muscle.

5.1.8 Arterial Supply

5.1.8.1 Infraorbital Artery

The infraorbital artery is one of the three branches of the maxillary artery, together with the mental and buccal arteries, that supply the face.

Fig. 5.14

The infraorbital artery at the face

5.1.8.2 Zygomaticofacial Artery

Fig. 5.15

Zygomaticofacial artery

5.1.8.3 Superficial Temporal Artery: Preauricular Course

Its long course can be distinguished in two parts: a first preauricular part at the cheek and a second temporal part above the zygomatic arch.

5.1.8.3.1 Preauricular Course

Fig. 5.16

Superficial temporal artery at the preauricular region and its relation to the superficial temporal vein and the auriculotemporal nerve

5.1.8.4 Transverse Facial Artery

Fig. 5.17

The transverse facial artery

Due to its numerous branches, the transverse facial artery supplies the parotid gland, the parotid duct, the facial nerve, the masseter muscle, and a large area of the cheek skin.

Fig. 5.18

Cutaneous perforator of the transverse facial artery

A giant and largely dilated transverse facial artery has also been reported to counterpoise the complete agenesis of a facial artery (Tubbs et al. 2005).

5.1.8.5 Buccal Artery

Fig. 5.19

Buccal artery

The artery is located about 3 cm lateral to the oral commissure and at the same level 5 mm medial to the medial aspect of the masseter muscle.

5.1.8.6 Facial Artery (Facial Part)

5.1.8.6.1 Facial Part

Fig. 5.20

The facial artery at the cheek

Fig. 5.21

The mean distances of the points where the facial artery branches originate are shown in Fig. 5.21.

The facial part of the facial artery anastomoses with the mental artery, the transverse facial artery, the infraorbital artery, and the ophthalmic artery (due to the dorsal nasal artery).

The facial artery shows multiple (mean six) perforating branches that supply large areas of facial skin and are more densely located at the level of the commissure (Fig. 5.22).

Fig. 5.22

Facial artery perforators to the skin

5.1.8.7 Facial Artery Variations

A variation of the facial arteries course is exhibited when the artery is underdeveloped, and thus, the artery does not reach its normal ending point.

Fig. 5.23

Facial artery variations

5.1.8.7.1 Typical

In the typical form, the facial artery is completely developed and ends with its final angular artery.

5.1.8.7.2 Ending as Lateral Nasal

5.1.8.7.3 Ending as Superior Labial

5.1.8.7.4 Ending as Inferior Labial

In very rare cases, the facial artery consists, in its facial part, only of the inferior labial artery.

It has been clarified that contrary to what previously had been believed, no ethnic differences exist in the pattern of the facial artery branching (Koh et al. 2003; Loukas et al. 2006a).

5.1.9 Venous Drainage

Fig. 5.24

The venous drainage of the cheek

5.1.10 Sensory Innervation

Fig. 5.25

Sensory innervation of the cheek

5.1.10.1 Infraorbital Nerve

Fig. 5.26

The infraorbital nerve

Fig. 5.27

Landmarks of infraorbital nerve

5.1.10.1.1 Infraorbital Nerve Blockade

Fig. 5.28

Block of the infraorbital nerve. (a) Extraorally. (b) Intraorally

5.1.10.2 Zygomaticofacial Nerve

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5.1 Layered Anatomy

5.1.1 Skin

5.1.1.1 Skin and Cheek Subunits

5.1.1.1.1 Infraorbital Subunit

5.1.1.1.2 Zygomatic Subunit

5.1.1.1.3 Parotidomasseteric (Preauricular) Subunit

5.1.1.1.4 Buccal Subunit

5.1.1.1.5 Nasolabial Subunit

5.1.2 Subcutaneous Layer

5.1.2.1 Superficial Fat Pads of the Cheek (Fig. 5.4)

5.1.3 SMAS and Superficial Muscle Layer

5.1.3.1 SMAS

5.1.3.2 Superficial Mimic Muscle Layer

5.1.3.2.1 Orbicularis Oculi Muscle

5.1.3.2.2 Suborbicularis Oculi Fat (SOOF)

5.1.3.2.3 Levator Labii Superioris Alaeque Nasi Muscle

5.1.3.2.4 Levator Labii Superioris Muscle

5.1.3.2.5 Zygomaticus Minor Muscle

5.1.3.2.6 Zygomaticus Major Muscle

5.1.3.2.7 Risorius Muscle

5.1.3.2.8 Platysma Muscle

5.1.3.2.9 Depressor Anguli Oris Muscle

5.1.4 Parotidomasseteric Fascia

5.1.5 Buccal Space

5.1.6 Deep Muscle Layer

5.1.6.1 Masseter Muscle

5.1.6.2 Buccinator Muscle

5.1.6.3 Levator Anguli Oris Muscle

5.1.7 Retaining Ligaments

5.1.8 Arterial Supply

5.1.8.1 Infraorbital Artery

5.1.8.2 Zygomaticofacial Artery

5.1.8.3 Superficial Temporal Artery: Preauricular Course

5.1.8.3.1 Preauricular Course

5.1.8.4 Transverse Facial Artery

5.1.8.5 Buccal Artery

5.1.8.6 Facial Artery (Facial Part)

5.1.8.6.1 Facial Part

5.1.8.7 Facial Artery Variations

5.1.8.7.1 Typical

5.1.8.7.2 Ending as Lateral Nasal

5.1.8.7.3 Ending as Superior Labial

5.1.8.7.4 Ending as Inferior Labial

5.1.9 Venous Drainage

5.1.10 Sensory Innervation

5.1.10.1 Infraorbital Nerve

5.1.10.1.1 Infraorbital Nerve Blockade

5.1.10.2 Zygomaticofacial Nerve

5.1.10.3 Auriculotemporal Nerve: Preauricular Course

5.1.10.4 Buccal (Sensory) Nerve

5.1.10.5 Mental Nerve

5.1.10.6 Great Auricular Nerve

5.1.11 Motor Innervation

5.1.11.1 Facial Nerve

5.1.11.1.1 Extratemporal Course

5.1.11.1.2 Intraparotid Course

5.1.11.1.3 Frontal Branch

5.1.11.1.4 Zygomatic Branch

Course

5.1.11.1.5 Buccal Branch

Course

5.1.11.1.6 Marginal Mandibular Branch

Course

5.1.11.1.7 Cervical Branch

5.1.11.1.8 Branching and Anastomotic Patterns of the Facial Nerve

5.2 Flaps Derived from the Cheek

5.2.1 Flap Design Concerning Vascular Anatomy

5.2.2 Danger Zones of the Facial Nerve at the Cheek

5.2.3 Flap Elevation Concerning Anatomic Planes

5.2.3.1 Subcutaneous Dissection Plane

5.2.3.2 Deep (Sub-SMAS) Dissection Plane

5.2.4 Rhomboid Flaps

5.2.4.1 Rhomboid Flap at Reconstruction of the Nasolabial Alar Base Area

5.2.4.2 Rhomboid Flap at Reconstruction of the Infraorbital Area

5.2.4.3 Rhomboid Flap at Reconstruction of the Zygomatic Area

5.2.4.4 Rhomboid Flap at Reconstruction of the Lateral Canthal Area

5.2.4.5 Rhomboid Flap at Reconstruction of the Buccal Area