Facial plast Surg 2017; 33(05): 470-482
DOI: 10.1055/s-0037-1606855
Original Article
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Facial Layers and Facial Fat Compartments: Focus on Midcheek Area

Yves Saban1, Roberto Polselli2, Dario Bertossi3, Charles East4, Olivier Gerbault5
  • 1Ear Nose Throat, Facial Plastic Surgery, Maxillo-Facial Surgery, Nice, France
  • 2Ear Nose Throat, Facial Plastic Surgery, Marina di Carrara, Italy
  • 3Department of Maxillofacial Facial Surgery, Policlinico GB Rossi, Verona, Italy
  • 4Rhinoplasty London, Facial Plastic Surgery, London, United Kingdom
  • 5Department of Plastic Surgery, Polyclinique Esthétique Marigny 3-5, Cours Marigny, France
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Address for correspondence

Yves Saban, MD, PHM
Private Office 31 Avenue Jean Médecin
06000 Nice
France   

Publikationsverlauf

Publikationsdatum:
29.September 2017 (online)

 

Abstract

Facial cosmetic procedures are doubtless in constant augmentation directly related to fillers and botulinum toxin injections. Many articles are published in the literature to warn about the complications of these aesthetic procedures. The need for a clear anatomic classification and review of deeper ultrastructural studies on adipose tissues in the midface area are obvious. This study aims: (1) To present midface anatomy of clinical relevance in a practical way for surgeons and cosmetologists. (2) To analyze the facial fasciae related to the fat compartments. (3) To show pictures of anatomic dissections of these anatomic structures. (4) To suggest an anatomic classification. The authors analyzed the facial anatomic layers and the facial fat compartments through facial anatomical dissections and experience in the field of facial surgical and cosmetic procedures. The authors propose a dynamic three-dimensional concept of facial layers related to muscle actions and facial fat compartmentalization in the midcheek area. A “lip–lid” superficial system associated with the malar fat pad represents the first layer; two deeper lip levator systems stratification explains the deep fat compartments as an anatomic division related to fasciae extensions. Facial grooves and segments correspond to these systems action. Moreover, the importance of ultrastructural studies has been underlined.


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Following the observation concerning the scientific topics discussed in medical meetings and scientific articles since the 2000s, we notice the incredible increase of communications concerning the facial volumes related to facial beauty, and the facial muscles according to aging and wrinkles. The comparison of this observation with the real social trend that establishes the emergence of filling products, fat, or fillers in the cosmetic market and of neuromuscular modulators, such as botulinum toxin explains the renewed importance of the anatomic studies of the facial fat compartments, facial muscles, and septa. Undoubtedly, the simple explanation is the huge financial market in this area that is expanding despite times of economic crisis in western countries. Moreover, active researches on stem cells are exceeding a simple cosmetic interest and constitute a major way for the future of the medicine. Facial fat is known as a heterogeneous entity that can be subdivided into different anatomical compartments. Recent research states that each of these compartments has different adipocytes and different extracellular collagenous matrix, which gives them different properties.

On the other hand, recent clinical publications have reported adverse outcomes and severe complications, such as blindness, nasal or forehead necrosis, which are not epiphenomenal and moreover can happen even to experienced physicians. These accidents have opened a new field of anatomic researches on specific anatomic sectors, facial vascularization, and on new technologies which could seem less important few years ago. Thus, safety and effectiveness of cosmetic procedures need to be balanced in modern cosmetic practice.

A study of anatomic variations about the periorbital and midface muscles and a simpler classification of the fat pads will be presented hereafter that may bring progress in better and simpler morphologic understanding of these structures and aesthetic analysis.

Historical Studies of the Facial Layers

The superficial fascia (SF) has been described as the superficial musculoaponeurotic system (SMAS) by Mitz and Peyronie in 1976,[1] following Tessier's suggestion (1974) during a meeting of the French Society; however, it was first described in the 19th century by Velpeau (1825)[2] as a unit: “the SF is formed on the overall surface of the body and may be thin or very thick; may be a loose tissue or very fibrotic.” Similar descriptions were stated by Paillard[3] in 1827 and later by others; but in 1910, Sterzi,[4] an anatomist from Padova made the first and the most complete anatomic and histologic study of the subcutaneous tissue and the SF, completely ignored by plastic surgeons. Micheli-Pellegrini[5] [6] in 1988 and 1992 tried to propagate this research. Some conclusions in Sterzi's works are: “on slim cadavers, the SF is more evident than on obese ones; the subcutaneous tissue has two layers divided by the SF, which is a fibrous membrane seen on the neck, face, head…; it is situated on the subcutaneous tissue between the superficial and the deep fat layers; muscle fibers can be seen on it; in the cervicofacial area it is the same, but in the deep fat layer on the neck and in a significant part of the head it becomes loose fibrous tissue, which allows it to slide over the muscular fasciae or the periosteum;… on babies the SF is very thin and more elastic, whereas on old people it is thicker and less elastic, contributing to the flaccidity of the skin.” Regarding the mimetic muscles and the SF, Sterzi stated that “the orbicularis muscles and those from the chin are directly fixed to the dermis, and it is not possible to demonstrate that they are surrounded by a true fascia; at the parotid region, there is a clear fascia that has continuity with the zygomatic muscles and with the anterior and posterior layers of the platysma.”


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Surgical Anatomy of the Facial Anatomic Layers: The Importance of the Facial Fasciae

The face can be considered to be divided into two very different anatomic–functional spaces, separated by the deep facial fascia: the superficial space of facial expression innervated by the facial nerve (i.e., the facial mask) and the deep visceral space innervated by other nerves such as trigeminal, oculomotor nerves, or spinal accessory nerve.

The mimic face is a stratification of five anatomical layers. From superficial to deep, one can describe: layer number 1: skin; layer number 2: subcutaneous fat and tela retinaculum cutis; layer number 3: SMAS; layer number 4: sub-SMAS space which can be either a fat layer (deep fat) or an areolar and undermining plane; layer number 5: deep facial fascia, which separates the superficial space or space of the facial expression, from the visceral deep space or masticatory space.

Numbering these anatomical layers (called 1, 2, 3, 4, and 5) may help the surgeon to know in real time at which depth he is performing his surgical dissection. The colors and frames differentiate the three superficial layers: brilliant white of the dermis, yellow lobules of the fat, brown of the SMAS muscle or brilliant transparency of the aponeurosis, all constituting simple landmarks. So the surgeon may decide to follow the most favorable plane of dissection.

The SMAS and the Muscles of Facial Expression Which Do Not Belong to the SMAS

The concept that the SMAS, layer number 3, represents a unique layer covering the face and the neck is attractive. This is not only a new concept: old anatomical works have already established that a double layer of fibrous tissue, the SF covers the whole human body underneath the skin. The SMAS ([Fig. 1]) is a composite anatomical double fascia layer derived from and part of the SF, which can include different mimic muscles in between its two fasciae. Where the fascia is present without intervening muscle, the superficial and deep layers of the sheath are fused. The superficial fascial layer is thin where it overlies the muscles. In contrast, the deep layer of the fascia is thicker, more supporting and provides a gliding surface at the interface with the underlying fourth layer.[7] This layer can be relatively thin and transparent, and then the underlying structures can become visible ([Fig. 1]). This does not mean that these deeper structures are part of the SMAS nor that the SMAS has disappeared. Conceptually, we can distinguish the anatomy, the surgery, and the function. Surgically the SMAS can be dissected as a muscular-aponeurotic layer; inversely, functionally, the mimetic muscles, which are part of it, conserve their function related to their interrelationship due to their functional nervous link and of the anatomic fibrous septa that interconnect them. Moreover, all these muscles present an extensive range of variations either in their presence or their direction or their power.

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Fig. 1 The SMAS layer. Anatomic dissection of the right hemiface showing the layer number 3: SMAS. The skin and subcutaneous fatty layer have been removed. The layer number 3, the SMAS, is exposed. One can recognize, from cephalic to caudal: frontalis muscle, superficialis temporalis fascia, orbicularis oculi pars orbitalis and pars palpebralis, preparotid fascia, and platysma muscle which most lateral fibers are investing the parotid SMAS, going upward till the zygomatic area. Deeper structures such as the zygomaticus major and minor muscles, the suborbicularis oculi fat are visible by transparency through a very thin aponeurotic almost invisible SMAS layer. SMAS, superficial musculoaponeurotic system.

Layer Number 4 ([Fig. 2]) Is A “Spaced Layer”

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Fig. 2 Layer number 4: “spaced” layer and facial ligaments—three-fourth right posterolateral view of the lateral face (“metaface”). Anatomic dissection (different dissection than [Fig. 1]) performed in the spaced layer number 4. This “spaced” layer is located between the SMAS and platysma (layer number 3) that is lifted anteriorly, and the deep facial fascia (layer number 5), which is still covering the parotid–masseteric area; deep to this transparent layer number 5, one can observe from caudal to cephalic the dark colored masseter muscle through which facial nerve buccal branches are running, the light brown colored parotid salivary gland. Please note the anterior extension of the parotid gland on top of the masseter muscle. The frontalis branch of the facial nerve is indicated (black arrow); at the cephalic part, the frontal branch of the temporal artery runs anteriorly, cephalic to the frontal nerve. The dissection cannot go forward anteriorly: facial ligaments that are perpendicular crossing structures are blocking the progression. From top to bottom: zygomatic ligaments; Mac Gregor's patch containing an artery that is the perforating branch of the transverse facial artery arising from below the anterior parotid pole; parotid and masseteric ligaments in front of the masseter; caudally the mandibular notch where the facial neurovascular pedicle is crossing the mandible inferior border. These ligaments form a vertical line that separates the “metaface” dissected here, and the “mesoface” or midface of facial expression located anteriorly. (Image provided courtesy of Saban and Polselli.[14])

Limited by two fasciae: superficially by the SMAS and deeper by the deep facial fascia, this space does not have its fascia; it can be alternatively an areolar gliding space (Merkel's space; areolar space between parotid SMAS and parotid capsule or masseteric aponeurosis) or a fatty compartment (as cheek fat pads), then called deep fat compartment.

In facial surgery, such as deep face lifts, the dissection performed in the layer number 4 requires lifting the SMAS (layer number 3); the SMAS can be used as a landmark for the dissection. Its brilliant light reflections and its fibrous aspect are different from the subcutaneous lobules of yellow fatty tissue; these visual landmarks can be used by the surgeon who is going to progress between two fibrous layers: the SMAS superficially and the deep facial fascia in-depth. This plane number 4 allows an easy dissection, even if the facial fibrous layers numbers 3 and 5 are weak with a risk to be accidentally crossed, then exposing the deeper structures. The dissection is performed without major obstacle in the plane between the SMAS superficially and the deep facial fascia in-depth, until a vertical line drawn from the lateral side of the orbital process. At this level, one can find from top to bottom many of the various facial ligaments ([Fig. 2]). Thus the layer number 4 appears at the same time as a space of sliding and as an area crossed by powerful structures controlling the position and the mobility of the superficial soft tissue forming the facial mask. Moreover, these ligaments and deep mimic muscles form anatomic boundaries that divide the subcutaneous fat and deep fat in distinct subcompartments.[8] This is particularly visible in the central face area: located in the layer number 4, the deep mimic muscles and the retaining ligaments are perpendicular structures crossing the different facial layers and connecting the deep anatomic elements to the skin or other muscles. So, we could compare the SMAS as a ship's sail and the deep muscles and the ligaments (which correspond to muscles “in regression”) to a tie rod.


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The Retaining Ligaments of the Face and the Boundaries of the Fat Compartments

The main authors who described the ligaments of the face are Mac Gregor (1959), Psillakis,[9] Furnas,[10] Stuzin et al.[11] These are two types: the proper osteocutaneous retaining ligaments (zygomatic, Mac Gregor, mandibular ligaments) and the superficial/deep fascia bands (the anterior platysma-cutaneous, the masseteric-cutaneous, the platysma-auricular or parotid-cutaneous) ([Fig. 2]). Furnas and Stuzin et al's anatomical works have highlighted the presence of numerous fibrous strips, directly inserted on the periosteum of the zygomatic bone posteriorly to the zygomaticus minor muscle, that insert fan-shaped at the level of the skin situated 4.5 cm anterior to the tragus, with vertical bundles 8 × 3 × 0.5 mm; there are true bony attachments, the pulling of which determines a real cutaneous mobilization.

The masseteric-cutaneous ligaments must be transected in the surgical procedures that need to proceed more anteriorly. The platysma-cutaneous and cutaneous-masseteric ligaments correspond to variable oblique aponeurotic extensions between the anterior border of the platysma, the masseter, and the dermis of the midcheek; for Stuzin et al and Furnas, they form a dimple and constitute an excellent support during the face lift. The branches of the facial nerve run underneath the premasseteric fascia.

The mandibular ligament inserts on the periosteum 1 cm over the mandibular border in its previous first third, on the line of insertion of the platysma and the depressor anguli oris; it runs fan-shaped horizontally 5 mm toward the skin. The traction on the skin (pinch test) allows highlighting this ligament. This marks the boundary between the attached muscular anterior segment and the neurovascular middle segment of the mandible. It opposes gravity: lateral to the mandibular ligament, the jowl can form, while medially only wrinkles, mainly the marionette lines, can be observed. The ramus marginalis mandibularis nerve always crosses the mandible dorsally to the mandibular ligament, in a subplatysmal position. The injections performed at the level of the ligament do not present any danger, except for certain vascular branches of the submental artery that is caudal to the ligament.

One can state that these ligaments create a barrier of fixation, which separates the lateral part of the face or metaface from the mesoface or midface; midface is the face of the facial expression and thus the one that ages faster. In the metaface, posteriorly, deep to the deep facial fascia, lay the temporal and masseter masticatory muscles and the parotid gland covered with its capsule, which joins with the premasseteric fascia forming the deep facial fascia.

Following Mendelson and Jacobson,[12] “the superficial muscles are more closely related to the overlying subcutaneous layer than they are to the deeper structures. The superficial flat muscles have a minimal direct attachment to the bone. They are indirectly stabilized to the skeleton by a ligament, located at the lateral border of the muscles. The frontalis is fixed by the superior temporal ligament along the superior temporal line, the orbicularis oculi is stabilized by the main zygomatic ligament at its inferolateral border, and the platysma is stabilized at its upper border by the upper key masseteric ligament.”

To summarize the compartmentalization of the face, one can consider the facial fasciae, the facial muscles of expression and their surrounding fat allowing their gliding mechanism. Classification is not yet clear, and there is no consensus in nomina anatomica about these anatomic structures. Keeping in mind the facial layers from 1 to 5, one can use their nomenclature to name the fat compartments, following the same denominations. From a layered stratification viewpoint, the superficial mimic face is divided into two main fat spaces: subcutaneous (the superficial fat compartment) and sub-SMAS (the deep fat compartment); whereas, the visceral face, located deep to the deep facial fascia is divided in the same manner into superficial structural fat compartment and deep buccal fat compartment. Another classification could be suggested as: fat 2 (subcutaneous), fat 4a (superficial sub-SMAS), 4b (deep sub-SMAS), 5a (structural deep), and 5b (deep buccal sub-fascial). This will be analyzed infra.

Looking at the three-dimensional (3D) volumes, compartmentalization is directly related to strong muscles fasciae expansions to the deep aspect of the skin and, in depth, to fasciae connections to the bones. Thus a “3D system” is created allowing mimic muscles to move the skin during mimicry, to glide on the surrounding structures, to act together with the synkinetic muscles corresponding to embryologic development.

Considering the different midfacial areas and facial expressions, that is, the look and the smile, one can separate the periorbital system and the perioral system.

Following Mendelson and Jacobson,[12] “the migratory path of the evolving muscles, including their connections and the multiple levels of the muscles, explain the definitive location of the facial nerve branches. In the anterior face, the migrated muscle masses are mainly located over and around the orbital and oral cavities.”

Contributing to the brow expression and the look, the periorbital area is dominated by the upper face function and the brow movements. Levator muscles are only the frontalis, while corrugator supercilii, depressor supercilii, procerus, orbicularis oculi and its expansions are mainly depressor muscles.

Contributing to the smile, considering the infraorbital area, one must consider both the periorbital muscles and the levator muscles of the upper lip. Most of these muscles are elevating the upper lip and the infraorbital (malar) area, contributing to the look. Nevertheless, their function is ambiguous as they are acting at the same time on the lower lid, the nose, and the upper lip.

Contributing to lower face mimicry, one can divide on the one hand the depressor muscles (depressor anguli oris, depressor labii inferioris, platysma) except the mentalis muscle that contracts the lower part of the chin. On the other hand, two other important intervening elevator muscles are the zygomaticus major and the levator anguli oris muscle.

Looking at the extreme range of interindividual variations of facial expressions,[13] one can imagine the range of anatomic variations in the anatomy of the mimic muscles, mainly in the midface which mixes look and smile expressions.

Anatomic dissections of this infraorbital area show, in fact, a large range of anatomic variations of the orbicularis oculi muscle, pars orbitalis, in the periorbital area.


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Anatomic Variations of the Lateral and Medial Bundles of the Orbicularis Oculi, Pars Orbitalis

In classic anatomy textbooks, even the most famous ones, the zygomaticus minor muscle, for example, may be unclear. It must have a bony insertion on the zygomatic bone, medially to the zygomaticus major. However, many times it is drawn without any bony insertion and presenting an extension upward to the superficialis temporalis fascia. This cannot be the zygomaticus minor muscle neither the zygomaticus major nor the orbicularis oculi, the orientation of which is acting like a sphincter. Some anatomists consider this muscle to be the most lateral portion of the orbitalis pars of the orbicularis oculi muscle. Nevertheless, this is a different muscle that can be called “zygomaticus superficialis” ([Fig. 3]); it takes an aponeurotic insertion on the fascia temporalis superficialis and extends to the upper lip, located in the same superficial layer as the orbicularis oculi.[14] Rüge, a German anatomist described an “auriculolabialis” muscle. This “zygomaticus superficialis” muscle acts like a high risorius, pulling laterally and upward the upper lip and the lateral cheek, and creating, therefore, wide crow feet wrinkles which can extend till the temple hair. It often results in skin expansions responsible for midcheek vertical wrinkles.

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Fig. 3 Zygomaticus superficialis: orbicularis oculi inferior–lateral extension and zygomatic muscles. Anatomic dissection of the right hemiface (different dissection than [Figs. 1] and [2]; lateral view). Subcutaneous dissection exposing the SMAS layer number 3, the skin and subcutaneous fatty layers are elevated anteriorly. Inserted cephalically on the superficialis temporalis fascia, a powerful superficial (layer number 3: SMAS) muscle is running anteriorly and downward, below the caudal border of the orbicularis oculi muscle. Located lateral and caudal to the orbicularis oculi pars orbitalis, superficial to the zygomaticus major located in-depth and caudally, this muscle lies in the same layer as the orbicularis oculi. Its fibers are attaching to the deep aspect of the skin. This inconstant anatomic variation of the orbicularis oculi pars orbitalis may be called “zygomaticus superficialis muscle.” SMAS, superficial musculoaporeurotic system. (Image provided courtesy of Saban and Polselli.[14])

Following the same analysis, one can consider the variations of the most medial bundles of the orbitalis pars of the orbicularis oculi muscle. This bundle belongs to the proper orbicularis oculi muscle and has a sphincter-shaped anatomy. Nevertheless, sometimes, in people presenting a huge midcheek and nasojugal groove separating the nasolabial segment from the adjacent midcheek segments, the anatomic dissection shows a particular muscle ([Figs. 4] and [5]). This muscle is darker and thicker than the adjacent orbicularis oculi, even if it lies in the same anatomic layer, and is directly connected to it, sharing the same aponeurosis; it gets a bony insertion on the frontal process of the maxillary bone, cephalic to the levator labii superioris alaeque nasi muscle, below the medial canthal tendon; then it runs obliquely in the nasojugal midcheek segment surrounded by the nasolabial fat and goes straight to the deep aspect of the midcheek skin where it inserts. So this muscle is responsible for the superomedial elevation of the midcheek, of the thickness of the nasojugal segment, and of the nasojugal and midcheek grooves. Its action leads to oblique wrinkles below the bunny lines. One may call this muscle “levator genae” or midcheek elevator. Moreover, the anatomic variations of these muscles in the midface may lead to consider the “levator genae” (cheek elevator) acting as the support for the deep aspect of the superficial nasolabial fat pad.

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Fig. 4 Levator genae muscle: orbicularis oculi muscle inferior–medial extension. Anatomic dissection of the right hemiface (different dissection than [Figs. 1] [2] [3]; front view). Subcutaneous dissection has been performed showing an oblique muscle inserted below the medial canthal tendon and running obliquely till the midcheek where it inserts on the deep aspect of the skin. This muscle does not belong to the orbicularis oculi and is different from the LLSAN that is more medial; it is not the levator labii superioris muscle that is inserted more laterally on the orbital rim and running to the upper lip. This is an anatomic variation of the orbicularis oculi pars orbitalis, or a different and inconstant muscle that may be named “levator genae” (cheek elevator). See also [Fig. 5]. LLSAN, levator labii alaeque nasi; SMAS, superficial musculoaponeurotic system.
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Fig. 5 Levator genae muscle: CT scan original picture. One can observe an oblique muscle inserted on the frontal process of the maxillary bone, the direction of which is not a sphincter but is attaching to the cheek. It is a cheek elevator muscle (“levator genae” in Latin). CT, computed tomography.

Following the anatomic variations of the orbicularis oculi muscle expansions, one can consider the most medial bundle in the upper lid that is named depressor supercilii ([Fig. 6]). It is a well-known muscle, which also presents anatomic variations and can be absent.

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Fig. 6 Depressor supercilii muscle; anatomic dissection of the central hemiface (different dissection than [Figs. 1] [2] [3] [4]; front view). The dissection has been performed below the subcutaneous fat of the radix and glabella. A skin–subcutaneous fat flap is pulled laterally on the right side. Procerus muscles are inserted on both sides of the nasal bones, close to the midline. One can observe the depressor supercilii muscles inserted superolaterally to the procerus; deeper and more lateral the medial fibers of the orbicularis oculi muscle are pulled with the skin flap.

To summarize, there is not one single orbicularis oculi muscle, pars orbitalis; there may be at least three expansions that are acting without any sphincter action: depressor supercilii, zygomaticus superficialis, and levator genae. These muscles are present from birth and explain both interindividual variations in facial expressions already visible in childhood and different ways of aging.


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Inferior Orbicularis Oculi Muscle, Pars Orbitalis, Anatomic Variations of the Middle Bundles

Clinical Value

Looking at the strength of the orbicularis oculi pars orbitalis muscle sphincter fibers in the midcheek area, one can observe during anatomic studies that sometimes these fibers can extend very low in the midcheek and can be very powerful ([Fig. 7]) (see also [Fig. 1]), while in others they can be dispersed and weak ([Fig. 8]), invested by the subcutaneous fat. The physiologic action of this muscle is not to close the lids, which is related to the pars palpebralis of the orbicularis oculi muscle, from which it is separated by the orbicularis retaining ligament (ORL) bony insertions. They are responsible for the elevation of the cheek during the smile, giving volume to the midcheek area, and sometimes deepening the palpebromalar groove. Thinking in 3D, these loose connections between a weak orbicularis and the skin through a weaker tela retinaculum cutis explains why people presenting loose and rare fibers show a vertical negative vector responsible for bad midface aging appearance.

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Fig. 7 Orbicularis oculi pars orbitalis inferior anatomic variations: Strong type. The inferior part of the orbicularis oculi is exposed after resection of the skin and subcutaneous fat, while the residual skin is pulled downward showing one of the zygomatic ligaments crossing the muscle fibers and running from the bone to the skin. The orbicularis fibers are strong, without free space and not invested by subcutaneous fat lobules. From these fibers, multiple fasciae creating the tela retinaculum cutis link the muscle to the skin, through the subcutaneous fat, thus generating the midcheek facial three-dimensional segment.
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Fig. 8 Orbicularis oculi par orbitalis inferior anatomic variations: Weak type. Compared with [Fig. 7]; in this case, muscles fibers are weaker and invested by fat lobules. One can also observe the nasolabial fat compartment, still not dissected, lying medial.

Moreover, precise dissections of the caudal extension of the orbicularis oculi bundles in the midcheek area lead us to propose what could be called the “superficial levator lip–lid system” or lip–lid system. The orbicularis muscle does not end where there are no more visible muscular fibers during the dissection: a true layer of fibrous extensions follows, extending the muscle layer[1] medially to the levator labii alaeque nasi muscle where its fascia fuses with the neighbor ones,[2] caudally to the nasolabial fold where it inserts, fusing with the dermis and the connecting fibers of the tela retinaculum cutis of the upper lip. These connections of the lip–lid system give another viewpoint of the relationships between the upper lip and the lower lid related to the nasolabial fold.

To summarize the relationships between orbicularis oculi muscle and midcheek appearance, one must consider the whole midcheek anatomy.

The three superficial layers forming the facial mask in the midcheek area are the skin, the subcutaneous fat (malar fat pad), and the “superficial levator lip–lid system” related to the orbicularis oculi muscle pars orbitalis and its expansions. They are directly related embryologically to the lamina infraorbitalis. The other muscles, even the mimic muscles, and fat pads are located deeper.

To understand the relationships between the anatomy and the facial appearance and their variations, one must consider the variants of the midcheek anatomy.

The basic anatomy is to consider the link between these three layers. In anatomy, there are three different layers, but functionally there is only one, which may be called superficial cutaneoadipomuscular system. The parameters are the following:[1] the skin is exposed to the exogenous alterations and the endogenous actions related to the muscle contractions;[2] the subcutaneous fat must be conceived not like a free layer but, on the contrary, as completely linked and attached to the deep aspect of the skin and to the superficial aspect of the orbicularis oculi muscle (which can be invested by the fat lobules), thanks to the tela retinaculum cutis directly related to the numerous and strong fibrous septa arising out of the muscle and attaching to the skin, thus creating a honeycomb net filled with fat lobules. The height and thickness of the subcutaneous fat will give the midcheek volume. According to Rohrich and Pessa,[8] this malar fat pad corresponds to the medial cheek fat pad compartment.[3] The orbicularis oculi orbitalis pars is responsible for the strength and the extension of the malar area superficial appearance.

The best aesthetic anatomy could be summarized as the following ([Fig. 9]):[1] complete orbicularis oculi muscle including the lateral and medial extensions (levator genae, zygomaticus superficialis) and complete sphincter muscular bundles;[2] nice subcutaneous fat amount reaching a high level close to the eyelashes and over passing the lid–cheek junction;[3] good quality of skin and good healthy way of life. The better the anatomy, the better is the midcheek appearance. On the contrary ([Fig. 10]), weak orbicularis oculi muscle presenting rare bundles, low level of subcutaneous fat, loose tela retinaculum cutis, and bad quality of life will lead to a bad facial appearance with huge negative vectors, deep folds, and tear trough deformity.

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Fig. 9 Strong “lip–lid” midcheek anatomical type. Complete muscular bundles of the “lip–lid system” leads to nice facial appearance, without vertical negative vectors.
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Fig. 10 Weak “lip–lid” midcheek anatomical type. Incomplete muscular bundles do not give good support to the lip–lid system thus resulting in bad facial appearance including vertical negative vectors and subcutaneous fat dissociation in nasolabial and malar fat pads, and deep facial grooves.

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Subcutaneous Fat Compartments in Midface

Going forward in the subcutaneous fat analysis, each of the three midcheek segments has a distinctly different thickness of subcutaneous fat. The subcutaneous layer is thinnest in the lid–cheek segment adjacent to the lid proper. In the malar segment, the layer is moderately thick and uniform, whereas it is markedly thicker in the nasolabial segment, which has the thickest layer of subcutaneous fat of the face. Where the subcutaneous fat is thicker, the retinaculum fibers are lengthened and more prone to weakness and distension. The thick subcutaneous fat in the nasolabial segment is named the malar fat pad, which is confusing terminology, given that its position is predominately medial to the prominence of the zygoma in the perioral part of the midcheek.[12]

The superficial nasolabial and malar fat compartments ([Figs. 11] and [12]) form the midcheek fat compartments. Superficial and lateral to the zygomaticus major muscle, the zygomatic fat pad (the “middle cheek” fat compartment[8] is the confusing name: it incorrectly seems to suggest that this middle fat lies in the infraorbital area or is located in between different layers) lies between so-called medial[8] or malar fat pad and lateral temporal-cheek fat. The superior border is defined by the superior cheek septum.

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Fig. 11 Superficial fat compartment. So-called cheek, or malar or infraorbital, or medial fat pad, the need of clarifying the nomenclature is obvious. Compare this fig. to [Figs. 9], [10], and [12] (see text).
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Fig. 12 The superficial infraorbital fat compartment (colored in green) has been elevated and pulled downward to show the underlying orbicularis oculi muscle. This infraorbital fat is separated from the superficial nasolabial fat by fascia expansions arising from the deeper muscles such as the division between the lip–lid system from the orbicularis oculi pars orbitalis and the nasolabial from the central levator system (see text).

We would like to suggest renaming these superficial fat compartments following their anatomical usual location, making them more natural: nasolabial (superficial 1), infraorbital (superficial 2), zygomatic (superficial 3), and lateral or parotidomasseteric (superficial 4).


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The Nasolabial Levator System and Deep Cheek Fat Compartments

The nasolabial levator system is located deep to the superficial midcheek levator system (i.e., the “lip–lid system”) related to the orbicularis oculi that give the appearance and the volume of the midcheek. According to the bony insertions and the classic anatomy, one can consider two parts in the nasolabial levator system: the central system and the lateral system. The muscles elevating the ala of the nose and the central part of the upper lip compose the central system: levator labii alaeque nasi (LLSAN). This muscle is mainly located in the nasojugal groove and corresponds to the medial border of the superficial nasolabial fat pad. Moreover, in some dissections, fibers of the zygomaticus minor muscle could be seen passing superficially to the facial vein and intermingling with the LLSAN, creating a lateral dilator nasi effect responsible for a relief lateral to the ala during the smile. According to these observations, one may consider that these muscles are sharing the same fascia, just deep to the orbicularis oculi system; thus a nasolabial deep fat compartment can be individualized in between these two layers of superficial and deep levator systems, and medial to the facial vein ([Fig. 13]). One must not confuse this nasolabial deep fat to the suborbicularis oculi fat (SOOF) that is deeper and more lateral ([Fig. 14]).

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Fig. 13 Deep nasolabial fat compartment. Anatomic dissection of the right hemiface (different dissection than previous figures); front view. The superficial fat compartments have been removed. The nasolabial fold is marked by the upper lid skin limit section. The zygomaticus muscles have been resected just below the level of the orbicularis oculi muscle, to free and to show the facial vein that runs straight obliquely, very deeply in the face. Between the nasolabial fold and the facial vein (dyed in blue) is located the deep nasolabial fat compartment. Lateral to the facial vein is the deep infrazygomatic fat compartment.
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Fig. 14 Deep nasolabial fat compartment. Anatomic dissection of the right hemiface (different dissection than previous figures); lateral view. The lip–lid system (L) corresponding to the superficial musculoaponeurotic system (SMAS) (layer number 3) and extending from the orbicularis oculi muscle is lifted anteriorly. Dissection progresses in the spaced layer number 4. One can observe in the center of the picture the zygomaticus major muscle (ZM); the zygomatic branch of the facial nerve runs over it; below is the superior buccal branch emerging from the anterior pole of the parotid gland (P) running forward, following the Stensen's duct (not dissected here) and crosses the deep facial fascia superficially and the deep buccal fat pad (Bichat's fat pad).[2] On the upper part, the flap lifting is blocked on the orbicularis retaining ligament (O). Cephalic to the zygomaticus major bony insertion lies the suborbicularis oculi fat (SOOF),[1] which covers the zygomatic bone and arch. Considering the ZM, it constitutes a remarkable landmark as pointed out by Hamra: cephalic is the SOOF;[1] in-depth is the deep buccal fat pad (Bichat's fat pad);[2] anterior is the infrazygomatic fat;[3] superficial is the deep cheek fat compartment.

The upper lip deep lateral levator system must be considered ([Fig. 15]). It is composed by the levator labii superioris medially, by the zygomaticus minor in the middle, and by the zygomaticus major muscle laterally, while the levator anguli oris is located deeper in another plane. Precise dissection of this area shows fibrous septa connecting these muscles together and to the bones (maxilla and zygoma) in depth ([Fig. 16A]). These muscles' bony insertions form the medial and caudal limits of the SOOF as defined by Aiache and Ramirez[15] or prezygomatic fat compartment,[7] together with the zygomatic ligaments. Superficial to these muscles is a deep fat pad located under the orbicularis oculi muscle. Deep to these muscles lays another fat pad which corresponds to the exit point of the infraorbital nerve and where the facial nerve's superior buccal branches run, crossing superficially the infraorbital sensory nerve ([Fig. 16B]–[D]). This last fat pad may correspond to the deep nasolabial fat pad bordered superficially by the levator anguli oris muscle, and in depth by the buccinator muscle.

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Fig. 15 Deep lip levator muscular system. Dissection of [Figs.1] and [7] continued. Deep to the lip–lid superficial system, the deep lip levator system is formed by fasciae connections relying on the zygomaticus major, zygomaticus minor, and levator labii superioris muscles; the most medial is the levator labii alaeque nasi. Superficial to it is the deep compartment divided by the facial vein into the deep nasolabial fat compartment and deep cheek compartment.
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Fig. 16 Deep nasolabial fat compartment. Fibrous septa and deep fat compartments. Sequence of dissection. Dissection of [Figs. 1], [7], and [15] continued. (A) The dissection of the fibrous septum connections in front of the zygomaticus muscles. (B) The deep nasolabial fat pad is pulled with forceps, showing the deeper levator anguli oris, and the facial nerve branches that are horizontally crossing this area. (C) The infraorbital nerve is exposed, which is located under the levator labii superioris (retracted by the hooks) and superficial to the levator anguli oris in-depth. The nerve is surrounded by the loose fat lobules, pulled by the forceps. (D) The superior buccal branch of the facial nerve crosses the infraorbital nerve superficially within the deep nasolabial fat compartment.

The observation of these muscles' bony insertions leads to underline an oblique line of levator muscle insertions (levator labii superioris, zygomaticus minor, zygomaticus major) that starts on the inferior bony orbital ridge medially and ends downward close to the masseter muscle insertion laterally, following the zygomatic ligaments ([Figs. 17] and [18]). Thus, it constitutes an important anatomic oblique line (the levator oblique insertion line), caudal to the ORL, with which it forms a triangle and which corresponds to the upper limit of the contraction of these levator muscles. In between the ORL insertions and the oblique levator line of insertion lies the triangular-shaped SOOF. That also explains the deep aspect of the midcheek groove, which separates the nasolabial midcheek segment from the malar midcheek segment.

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Fig. 17 The suborbicularis oculi fat (SOOF) and the zygomatic ligaments. Same dissection as [Figs. 1], [7], [15] [16] [17] [18] [19]. Previous stage: the orbicularis oculi pars orbitalis is elevated, at the level of the orbicularis retaining ligament (ORL); caudally, the soft tissues are pulled downward to show the zygomatic ligaments that resist to the traction. The SOOF is located between these ligaments: ORL cranially and zygomatic ligaments caudally.
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Fig. 18 The deep facial fascia and the zygomatic fat pads. Another dissection: Lateral view of the zygomatic area after resection of the three first layers. Below and lateral to the orbit, the suborbicularis oculi fat extends laterally till the auricle and fuses with the suprazygomatic fat pad. Deep temporal pedicles, dyed in blue, are crossing these two structural deep zygomatic fat compartments perpendicularly. The caudal border is the bony insertions of the zygomatic muscles. Where the bone (periosteum) is visible, is the orbicularis retaining ligament that has been resected together with the orbicularis oculi muscle. One can observe the oblique line of the levator muscles of bony insertion. Caudally, the facial nerve has been exposed, together with the transverse facial artery and the Stensen's parotid duct colored in blue by the dye. They form the transverse facial pedicle. (Image provided courtesy of Saban and Polselli.[14])

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The Deep Facial Fascia (Layer Number 5) and the Deep Structural and Visceral Fat Compartments

The deep facial fascia (layer number 5) separates the superficial spaces of the facial mask innervated by the facial nerve (VII), from the visceral deep spaces innervated by trigeminal nerve (V), the oculomotor nerves (III, IV, VI), and the muscles of orientation (sternocleidomastoid muscle and spinal accessory nerve XI). One can consider by assimilation that the orbital septum and the periosteum of the skull bones correspond to the deep facial fascia.

“Considering the description of the deep facial fascia, it is a composite anatomic structure representing a continuation of the deep cervical fascia cephalad into the face. By assimilation to the SMAS concept in one unique structure, it may be possible to understand the deep facial fascia as a unique layer separating the facial mask from the visceral face, the importance of which lies in the fact that the facial nerve branches within the cheek lie deep to this deep fascial layer.”[11]

The dissection deep to the three first layers proceeds in the spaced layer number 4 which can correspond either to a detachable areolar space, the Merkel's space in the cranial area, or to an adipose sub-SMAS deep space in the midface. The deep facial plane has been exposed ([Figs. 2] and [18]). It is very polymorphic and organized into different areas: the deep temporalis fascia in the temporal region; the capsule of the parotid gland in the preauricular and retromandibular areas; the masseteric fascia. In the buccal space, the deep facial fascia separates the deep buccal Bichat's fat pad from the superficial mimic face. It results in the fusion of the masseteric fascia and the buccinator fascia, splitting to follow the Stensen's duct ([Fig. 19]) till its penetration into the buccinator muscle ([Fig. 20]); the superficial layer of the deep facial fascia appears like an anterior extension of the parotid gland capsule, while the deep layer of the deep facial fascia corresponds to an anterior extension of the masseteric fascia. The facial nerve is running in between these two fasciae ([Fig. 21] [histologic section]).

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Fig. 19 The deep facial fascia: Histologic section. The masseter muscle is covered by its aponeurosis (arrow). The SMAS (S) and the skin are superficial. Following anteriorly (on the right part of the picture), one can note the splitting of the masseter aponeurosis in two layers surrounding the Stensen's duct (D).
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Fig. 20 Deep facial fascia and Bichat's fat pad. Another dissection showing the Stensen's duct crossing the buccal fat pad (Bichat's fat pad); the deep facial fascia has been dissected from the masseter muscle and is pulled anteriorly till the buccinators muscle. This deep facial fascia separates the mimic face from the deep face.
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Fig. 21 Histologic section showing the parotid–masseteric fasciae fusion over the facial nerve. Cross-section through parotid gland, masseter muscle, facial nerve, and facial fasciae. Also, observe the different facial layers and the tela retinaculum cutis. The glandular acini of the salivary gland allow to follow the capsule that covers the facial nerve superficially at its exit point of the gland, just superficial to the masseter (central at the lowest part of the picture), and associated with the transverse facial artery. The facial nerve is lying just below the parotid capsule and superficial to the masseter fascia.

Different deep fat compartments belong to these deep facial structures, even if there is still no established consensus. One could consider two different kinds of deep fat pads following their location. They can be either “structural” fat pads that can be crossed perpendicularly by neurovascular pedicles from trigeminal nerve branches or “visceral” which correspond to the unique buccal fat pad. The structural fat compartments are: the temporal fat pad (suprazygomatic fat pad), located in the division of the deep temporalis fascia (between layers 5a and 5b); the prezygomatic fat pad (SOOF) which presents sometimes an unusual lateral extension which can reach the suprazygomatic fat pad, located between the layer 5a and the zygomatic periosteum ([Fig. 18]). On the contrary, the buccal fat pad (Bichat's)[16] is an important anatomic structure located deep in the 5b layer, in the buccotemporal space ([Fig. 22]), between the fascia of the buccinator muscle and the fascia of the masseter muscle. The buccal fat is unique in humans and cannot be considered in the same way as the structural fat compartments. However, its morphological, aesthetic, cosmetic, and surgical importance is considerable. Three relevant anatomic structures (Stensen's duct, facial vein, zygomaticus major muscle), forming the “buccal star,” cross the anterior part of this buccal space ([Fig. 23]). It has four extensions: buccal, pterygoid, pterygopalatine, and temporal ([Fig. 24]); the latter one is also known as the deep temporal fat pad of the temporal region and is found between the deep layer of the deep temporal fascia and the proper temporalis muscle.

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Fig. 22 Bichat's buccal fat pad topographic anatomy. Different anatomic dissection from other photos. All the facial layers and superficial soft tissues have been resected, along with the layer number 5 deep facial fascia. The buccal fat pad appears between the masseter and the maxilla, while its temporal extension can be seen just above the zygomatic arch.
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Fig. 23 The “buccal star.” Different anatomic dissection: Right side; lateral view. The superficial anatomic structures crossing the buccal space are forming an asterisk: Stensen's salivary canal horizontally, zygomaticus major muscle oblique medially, and the facial vein oblique laterally. In depth, the bottom is formed by the buccinator muscle while the masseter is visible laterally. (Image provided courtesy of Saban and Polselli.[14])
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Fig. 24 Drawing of the Bichat's buccal fat pad. The zygomatic arch (1, 1') has been resected and masseter reflected[2] posteriorly. The extensions of the buccal fat pad are shown and the parotid–masseteric fascia[8] is enveloping the Stensen's parotid salivary canal[5] till it penetrates the buccinators muscle.[4] It has four extensions: buccal,[7] pterygoid, pterygopalatine, and temporal (7'). (Image provided courtesy of Testut L. Traité d'anatomie humaine. Paris, France: Doin; 1931: pp550.)

Facial layers and facial fat compartments related to the facial mimic function form a multilayer system overlying the masticatory system and the buccal Bichat's fat pad located in and filling the buccal–temporal space ([Figs. 25] and [26]).

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Fig. 25 Anatomy of the facial layers in the midface area. Different dissection from the previous ones. Right face is shown from the front view. See also [Fig. 26] for better understanding. The multiple facial layers have been dissected to show their relationships. The nasolabial superficial and deep fat compartments have been resected to show the muscles. One can observe from lower lid to oral commissure, the muscles: orbicularis oculi pars orbitalis; llsan; levator labii superioris; levator anguli oris; zygomaticus major; modiolus; buccinators; platysma; depressor anguli oris. The fat compartments: superficial; suborbicularis oculi fat; deep fat compartment; buccal fat pad (Bichat's fat pad). Note also the Stensen's parotid salivary canal, white color, just caudal to the zygomaticus major muscle.
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Fig. 26 Facial multilayer anatomy summarized. Oblique cross-section of the right face, shown from medial view. The section is performed from the medial canthus to the oral commissure. Mimic muscles and facial fat compartments present an alternate anatomy; from cephalic to caudal: First layers forming the lip–lid system: palpebral skin, the superficial fat compartment (malar fat pad), orbicularis oculi muscle pars orbitalis (superficial cutaneoadipomuscular system). Fourth layer: superficial nasolabial fat compartment. Levator labii superioris muscle. The deep nasolabial fat compartment where the infraorbital and facial nerves run. Levator anguli oris. Buccal fat pad (buccal part). Buccinator muscle. The mucosa of the oral cavity.

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Anatomy of the Facial Adipose Tissues: Ultrastructural New Concepts

Three different types of facial adipose tissue can be identified[17] which are located either superficially (dermal white adipose tissue) or deep (subcutaneous white adipose tissue [sWAT]): fibrous (perioral location), structural (major part of the midface), and deposit (buccal fat pad and deep temporal fat pad). Dynamically, deep sWAT is considered a slow renewal tissue with characteristic turnover times of around 10 years.[18] These various fat types present differences in their adipocytes size and collagenous matrix composition. Ghassemi et al[19] stated a classification of these different fat tissues: two different types can be identified: Type 1 can be found in the medial and lateral midface and parts of the periorbital region, as well as in the temple, forehead, and neck. Here, the adherence is loose, whereas in type 2 in perioral and nasal areas, as well as in the area of the eyebrows, a strong linkage is present between the facial muscles, the collagenous meshwork surrounding the adipocytes, and the skin.

Microstructural Classification of Facial Adipose Tissue Depots

Recent researches stated that extracellular matrix in adipose tissues (ATs) is not a passive scaffold but an active player in different morphologic and physiologic processes[20] and that its specific modification can even be a hallmark of metabolically changed adipocytes.

Besides the macroscopic compartmental classification of facial AT, a microstructural modification of different fat compartments in an aging face has not been described properly. The first attempt to describe the microscopic differences in the structure of various facial fat compartments taking into account both the morphology of adipocytes and the local collagen content was undertaken only recently by Sbarbati et al[21] who subdivided the sWAT depots using the results of transmission electron microscopy and scanning electron microscopy into three groups:[1] deposit (metabolic) WAT;[2] sWAT;[3] and fibrous WAT. Based on these results, Bertossi et al[22] proposed a classification of the fat compartments from the medium third of the face (the malar, periorbital, labial, nasal, and buccal fat pads) using the same methods as Sbarbati et al and have shown that these fat compartments present some significant ultrastructural differences particularly in the facial connective tissue that seems to be characterized by different embryonic origin in comparison with the AT of the other body fat. While the body and limbs fats have mesoderm origin, the facial connective tissue seems to be derived from neural ectoderm.


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Conclusion

Connections of mimetic facial muscles to the dermis are made through the subcutaneous and deep AT divided in compartments and attached to the skin and the muscles, forming the superficial and deep functional and aesthetic units of the face. A superficial “lip–lid system” is described overlying and sliding on deeper lip elevator structures; the lip–lid system, attached to the ORL is pulling facial soft tissues vertically upward, thus creating the palpebrojugal groove. On the opposite, related to deep facial fat compartments and inserted obliquely on the bones, the lip levator system, is acting laterally, thus responsible of the midcheek furrow.

Anatomic variations of mimic muscles are directly related to the wide interindividual range of facial expressions. Further researches on the physiology of the fat subcompartments will be of great value to better understand their role which does not look like limited to a sliding layer separating muscles of facial expression.


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Die Autoren geben an, dass kein Interessenkonflikt besteht.


Address for correspondence

Yves Saban, MD, PHM
Private Office 31 Avenue Jean Médecin
06000 Nice
France   


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Fig. 1 The SMAS layer. Anatomic dissection of the right hemiface showing the layer number 3: SMAS. The skin and subcutaneous fatty layer have been removed. The layer number 3, the SMAS, is exposed. One can recognize, from cephalic to caudal: frontalis muscle, superficialis temporalis fascia, orbicularis oculi pars orbitalis and pars palpebralis, preparotid fascia, and platysma muscle which most lateral fibers are investing the parotid SMAS, going upward till the zygomatic area. Deeper structures such as the zygomaticus major and minor muscles, the suborbicularis oculi fat are visible by transparency through a very thin aponeurotic almost invisible SMAS layer. SMAS, superficial musculoaponeurotic system.
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Fig. 2 Layer number 4: “spaced” layer and facial ligaments—three-fourth right posterolateral view of the lateral face (“metaface”). Anatomic dissection (different dissection than [Fig. 1]) performed in the spaced layer number 4. This “spaced” layer is located between the SMAS and platysma (layer number 3) that is lifted anteriorly, and the deep facial fascia (layer number 5), which is still covering the parotid–masseteric area; deep to this transparent layer number 5, one can observe from caudal to cephalic the dark colored masseter muscle through which facial nerve buccal branches are running, the light brown colored parotid salivary gland. Please note the anterior extension of the parotid gland on top of the masseter muscle. The frontalis branch of the facial nerve is indicated (black arrow); at the cephalic part, the frontal branch of the temporal artery runs anteriorly, cephalic to the frontal nerve. The dissection cannot go forward anteriorly: facial ligaments that are perpendicular crossing structures are blocking the progression. From top to bottom: zygomatic ligaments; Mac Gregor's patch containing an artery that is the perforating branch of the transverse facial artery arising from below the anterior parotid pole; parotid and masseteric ligaments in front of the masseter; caudally the mandibular notch where the facial neurovascular pedicle is crossing the mandible inferior border. These ligaments form a vertical line that separates the “metaface” dissected here, and the “mesoface” or midface of facial expression located anteriorly. (Image provided courtesy of Saban and Polselli.[14])
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Fig. 3 Zygomaticus superficialis: orbicularis oculi inferior–lateral extension and zygomatic muscles. Anatomic dissection of the right hemiface (different dissection than [Figs. 1] and [2]; lateral view). Subcutaneous dissection exposing the SMAS layer number 3, the skin and subcutaneous fatty layers are elevated anteriorly. Inserted cephalically on the superficialis temporalis fascia, a powerful superficial (layer number 3: SMAS) muscle is running anteriorly and downward, below the caudal border of the orbicularis oculi muscle. Located lateral and caudal to the orbicularis oculi pars orbitalis, superficial to the zygomaticus major located in-depth and caudally, this muscle lies in the same layer as the orbicularis oculi. Its fibers are attaching to the deep aspect of the skin. This inconstant anatomic variation of the orbicularis oculi pars orbitalis may be called “zygomaticus superficialis muscle.” SMAS, superficial musculoaporeurotic system. (Image provided courtesy of Saban and Polselli.[14])
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Fig. 4 Levator genae muscle: orbicularis oculi muscle inferior–medial extension. Anatomic dissection of the right hemiface (different dissection than [Figs. 1] [2] [3]; front view). Subcutaneous dissection has been performed showing an oblique muscle inserted below the medial canthal tendon and running obliquely till the midcheek where it inserts on the deep aspect of the skin. This muscle does not belong to the orbicularis oculi and is different from the LLSAN that is more medial; it is not the levator labii superioris muscle that is inserted more laterally on the orbital rim and running to the upper lip. This is an anatomic variation of the orbicularis oculi pars orbitalis, or a different and inconstant muscle that may be named “levator genae” (cheek elevator). See also [Fig. 5]. LLSAN, levator labii alaeque nasi; SMAS, superficial musculoaponeurotic system.
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Fig. 5 Levator genae muscle: CT scan original picture. One can observe an oblique muscle inserted on the frontal process of the maxillary bone, the direction of which is not a sphincter but is attaching to the cheek. It is a cheek elevator muscle (“levator genae” in Latin). CT, computed tomography.
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Fig. 6 Depressor supercilii muscle; anatomic dissection of the central hemiface (different dissection than [Figs. 1] [2] [3] [4]; front view). The dissection has been performed below the subcutaneous fat of the radix and glabella. A skin–subcutaneous fat flap is pulled laterally on the right side. Procerus muscles are inserted on both sides of the nasal bones, close to the midline. One can observe the depressor supercilii muscles inserted superolaterally to the procerus; deeper and more lateral the medial fibers of the orbicularis oculi muscle are pulled with the skin flap.
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Fig. 7 Orbicularis oculi pars orbitalis inferior anatomic variations: Strong type. The inferior part of the orbicularis oculi is exposed after resection of the skin and subcutaneous fat, while the residual skin is pulled downward showing one of the zygomatic ligaments crossing the muscle fibers and running from the bone to the skin. The orbicularis fibers are strong, without free space and not invested by subcutaneous fat lobules. From these fibers, multiple fasciae creating the tela retinaculum cutis link the muscle to the skin, through the subcutaneous fat, thus generating the midcheek facial three-dimensional segment.
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Fig. 8 Orbicularis oculi par orbitalis inferior anatomic variations: Weak type. Compared with [Fig. 7]; in this case, muscles fibers are weaker and invested by fat lobules. One can also observe the nasolabial fat compartment, still not dissected, lying medial.
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Fig. 9 Strong “lip–lid” midcheek anatomical type. Complete muscular bundles of the “lip–lid system” leads to nice facial appearance, without vertical negative vectors.
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Fig. 10 Weak “lip–lid” midcheek anatomical type. Incomplete muscular bundles do not give good support to the lip–lid system thus resulting in bad facial appearance including vertical negative vectors and subcutaneous fat dissociation in nasolabial and malar fat pads, and deep facial grooves.
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Fig. 11 Superficial fat compartment. So-called cheek, or malar or infraorbital, or medial fat pad, the need of clarifying the nomenclature is obvious. Compare this fig. to [Figs. 9], [10], and [12] (see text).
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Fig. 12 The superficial infraorbital fat compartment (colored in green) has been elevated and pulled downward to show the underlying orbicularis oculi muscle. This infraorbital fat is separated from the superficial nasolabial fat by fascia expansions arising from the deeper muscles such as the division between the lip–lid system from the orbicularis oculi pars orbitalis and the nasolabial from the central levator system (see text).
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Fig. 13 Deep nasolabial fat compartment. Anatomic dissection of the right hemiface (different dissection than previous figures); front view. The superficial fat compartments have been removed. The nasolabial fold is marked by the upper lid skin limit section. The zygomaticus muscles have been resected just below the level of the orbicularis oculi muscle, to free and to show the facial vein that runs straight obliquely, very deeply in the face. Between the nasolabial fold and the facial vein (dyed in blue) is located the deep nasolabial fat compartment. Lateral to the facial vein is the deep infrazygomatic fat compartment.
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Fig. 14 Deep nasolabial fat compartment. Anatomic dissection of the right hemiface (different dissection than previous figures); lateral view. The lip–lid system (L) corresponding to the superficial musculoaponeurotic system (SMAS) (layer number 3) and extending from the orbicularis oculi muscle is lifted anteriorly. Dissection progresses in the spaced layer number 4. One can observe in the center of the picture the zygomaticus major muscle (ZM); the zygomatic branch of the facial nerve runs over it; below is the superior buccal branch emerging from the anterior pole of the parotid gland (P) running forward, following the Stensen's duct (not dissected here) and crosses the deep facial fascia superficially and the deep buccal fat pad (Bichat's fat pad).[2] On the upper part, the flap lifting is blocked on the orbicularis retaining ligament (O). Cephalic to the zygomaticus major bony insertion lies the suborbicularis oculi fat (SOOF),[1] which covers the zygomatic bone and arch. Considering the ZM, it constitutes a remarkable landmark as pointed out by Hamra: cephalic is the SOOF;[1] in-depth is the deep buccal fat pad (Bichat's fat pad);[2] anterior is the infrazygomatic fat;[3] superficial is the deep cheek fat compartment.
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Fig. 15 Deep lip levator muscular system. Dissection of [Figs.1] and [7] continued. Deep to the lip–lid superficial system, the deep lip levator system is formed by fasciae connections relying on the zygomaticus major, zygomaticus minor, and levator labii superioris muscles; the most medial is the levator labii alaeque nasi. Superficial to it is the deep compartment divided by the facial vein into the deep nasolabial fat compartment and deep cheek compartment.
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Fig. 16 Deep nasolabial fat compartment. Fibrous septa and deep fat compartments. Sequence of dissection. Dissection of [Figs. 1], [7], and [15] continued. (A) The dissection of the fibrous septum connections in front of the zygomaticus muscles. (B) The deep nasolabial fat pad is pulled with forceps, showing the deeper levator anguli oris, and the facial nerve branches that are horizontally crossing this area. (C) The infraorbital nerve is exposed, which is located under the levator labii superioris (retracted by the hooks) and superficial to the levator anguli oris in-depth. The nerve is surrounded by the loose fat lobules, pulled by the forceps. (D) The superior buccal branch of the facial nerve crosses the infraorbital nerve superficially within the deep nasolabial fat compartment.
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Fig. 17 The suborbicularis oculi fat (SOOF) and the zygomatic ligaments. Same dissection as [Figs. 1], [7], [15] [16] [17] [18] [19]. Previous stage: the orbicularis oculi pars orbitalis is elevated, at the level of the orbicularis retaining ligament (ORL); caudally, the soft tissues are pulled downward to show the zygomatic ligaments that resist to the traction. The SOOF is located between these ligaments: ORL cranially and zygomatic ligaments caudally.
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Fig. 18 The deep facial fascia and the zygomatic fat pads. Another dissection: Lateral view of the zygomatic area after resection of the three first layers. Below and lateral to the orbit, the suborbicularis oculi fat extends laterally till the auricle and fuses with the suprazygomatic fat pad. Deep temporal pedicles, dyed in blue, are crossing these two structural deep zygomatic fat compartments perpendicularly. The caudal border is the bony insertions of the zygomatic muscles. Where the bone (periosteum) is visible, is the orbicularis retaining ligament that has been resected together with the orbicularis oculi muscle. One can observe the oblique line of the levator muscles of bony insertion. Caudally, the facial nerve has been exposed, together with the transverse facial artery and the Stensen's parotid duct colored in blue by the dye. They form the transverse facial pedicle. (Image provided courtesy of Saban and Polselli.[14])
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Fig. 19 The deep facial fascia: Histologic section. The masseter muscle is covered by its aponeurosis (arrow). The SMAS (S) and the skin are superficial. Following anteriorly (on the right part of the picture), one can note the splitting of the masseter aponeurosis in two layers surrounding the Stensen's duct (D).
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Fig. 20 Deep facial fascia and Bichat's fat pad. Another dissection showing the Stensen's duct crossing the buccal fat pad (Bichat's fat pad); the deep facial fascia has been dissected from the masseter muscle and is pulled anteriorly till the buccinators muscle. This deep facial fascia separates the mimic face from the deep face.
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Fig. 21 Histologic section showing the parotid–masseteric fasciae fusion over the facial nerve. Cross-section through parotid gland, masseter muscle, facial nerve, and facial fasciae. Also, observe the different facial layers and the tela retinaculum cutis. The glandular acini of the salivary gland allow to follow the capsule that covers the facial nerve superficially at its exit point of the gland, just superficial to the masseter (central at the lowest part of the picture), and associated with the transverse facial artery. The facial nerve is lying just below the parotid capsule and superficial to the masseter fascia.
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Fig. 22 Bichat's buccal fat pad topographic anatomy. Different anatomic dissection from other photos. All the facial layers and superficial soft tissues have been resected, along with the layer number 5 deep facial fascia. The buccal fat pad appears between the masseter and the maxilla, while its temporal extension can be seen just above the zygomatic arch.
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Fig. 23 The “buccal star.” Different anatomic dissection: Right side; lateral view. The superficial anatomic structures crossing the buccal space are forming an asterisk: Stensen's salivary canal horizontally, zygomaticus major muscle oblique medially, and the facial vein oblique laterally. In depth, the bottom is formed by the buccinator muscle while the masseter is visible laterally. (Image provided courtesy of Saban and Polselli.[14])
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Fig. 24 Drawing of the Bichat's buccal fat pad. The zygomatic arch (1, 1') has been resected and masseter reflected[2] posteriorly. The extensions of the buccal fat pad are shown and the parotid–masseteric fascia[8] is enveloping the Stensen's parotid salivary canal[5] till it penetrates the buccinators muscle.[4] It has four extensions: buccal,[7] pterygoid, pterygopalatine, and temporal (7'). (Image provided courtesy of Testut L. Traité d'anatomie humaine. Paris, France: Doin; 1931: pp550.)
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Fig. 25 Anatomy of the facial layers in the midface area. Different dissection from the previous ones. Right face is shown from the front view. See also [Fig. 26] for better understanding. The multiple facial layers have been dissected to show their relationships. The nasolabial superficial and deep fat compartments have been resected to show the muscles. One can observe from lower lid to oral commissure, the muscles: orbicularis oculi pars orbitalis; llsan; levator labii superioris; levator anguli oris; zygomaticus major; modiolus; buccinators; platysma; depressor anguli oris. The fat compartments: superficial; suborbicularis oculi fat; deep fat compartment; buccal fat pad (Bichat's fat pad). Note also the Stensen's parotid salivary canal, white color, just caudal to the zygomaticus major muscle.
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Fig. 26 Facial multilayer anatomy summarized. Oblique cross-section of the right face, shown from medial view. The section is performed from the medial canthus to the oral commissure. Mimic muscles and facial fat compartments present an alternate anatomy; from cephalic to caudal: First layers forming the lip–lid system: palpebral skin, the superficial fat compartment (malar fat pad), orbicularis oculi muscle pars orbitalis (superficial cutaneoadipomuscular system). Fourth layer: superficial nasolabial fat compartment. Levator labii superioris muscle. The deep nasolabial fat compartment where the infraorbital and facial nerves run. Levator anguli oris. Buccal fat pad (buccal part). Buccinator muscle. The mucosa of the oral cavity.