Smas and Anatomy Of

ANATOMY OF RHYTIDECTOMY

5 LAYERS OF CRITICAL ANATOMY 1. Skin 2. Subcutaneous fat 3. SMAS 4. thin fascial layer 5. Facial nerve

 These 5 layers are consistent in all areas of the face.  Over the zygomatic arch, the layers become compressed, but the arrangement is maintained.  The SMAS is the layer that is most heterogeneous: it can be fibrous, muscular or fatty depending on its location in the face.  The muscles of facial expression are all part of the SMAS: frontalis, orbicularis oculi, zygomaticus major and minor and platysma.

SMAS  Superficial Musculo Aponeurotic System of the face  Fibromuscular layer blends with frontalis, superficial temporal fascia superiorly and with platysma inferiorly  Described by Mitz and Peyronie (PRS 1976) 2

 Anterior connections (ie, relation to N-L fold) controversial.  SMAS has no bony connections.  SMAS divides the facial subcutaneous fat into 2 layers.  Superficial to the SMAS, the fat lobules are divided by multiple fibrous septae that extend from it to the dermis.  Deep to the SMAS is another layer of yellow fat between it and the investing layer of the parotid gland, the masseter muscle and, anteriorly, the muscles of facial expression.  The SMAS varies in thickness in different parts of the face: i. in the pre-masseteric area, it is a substantial, continuous layer. ii. in the lateral midface and cheek, it is rather discontinuous and contains muscle and fibrous tissue – considered as investing fascia of mimetic muscles  The only nerves superficial to SMAS in the cheek are sensory branches.  The motor nerves (VII) lie deep to it.  Anterior to the parotid gland, the SMAS becomes thin and because the branches of the VII nerve lie immediately below this fragile layer, dissection in this area is hazardous.

Parotideomasseteric fascia

The deep (investing) layer splits into 2 layers to invest the parotid gland. The deeper layer (posterior masseteric fascia) passing deep to the parotid gland is attached superiorly along the base of the skull from the tip of the mastoid process to the lower border of the tympanic plate, as far medially as the carotid foramen. Anteriorly, the fascia may continue deep to the masticatory (buccal) fat pad. The superficial layer over the parotid gland is termed the parotid fascia, and it attaches superiorly to the zygomatic process of the temporal bone. The upward continuation is the deep temporal fascia. With the exception of the temporal branches, the other facial nerve branches lie deep to this layer further anteri- or in the cheek, in the part known as the parotideomasseteric fascia. This thin layer may be separated from the overlying SMAS between the anterior border of the parotid gland and the anterior border of the masseter muscle.

Viscoelastic Properties  a composite tissue comprising collagen, elastic fibers, and fat cells in an extracellular viscous matrix. Both SMAS and facial skin tissues exhibit viscoelastic properties, but SMAS tissue has delayed stress relaxation. As a consequence, SMAS is viewed as a firmer elastic foundation for the more viscous facial skin.  SMAS layer exhibits significantly less stress-relaxation and creep when compared with the subcutaneous skin flap. This property of the SMAS has led the majority of aesthetic surgeons to plicate, excise, or elevate the SMAS to tighten it, with reported benefits on the long-term results  The gradual expansion of the SMAS postoperatively, the slackening effect, might take place in some patients over a period ranging from weeks to months. This differs from the behaviour of facial skin – this has rapid stress relaxation occurring over a period of 20 to 30 minutes. 3

Controversies 1. Deep extent and relation to parotid fascia 2. Anterior extent and relation to N-L fold 3. Superior extent

Relationship to Parotid fascia  Whether the SMAS is continuous with, and part of, the parotid fascia, or whether it exists as a separate layer, is a moot point of much debate. i. Mitz and Peyronie (1976) stated that they are 2 fascial layers separated by fat. ii. Gossain and Yousif (1993) claim that there are 2 fascial layers closely applied with no intervening fat. iii. Jost and Levet (1984) state the 2 are in fact one fascial layer.  Most believe it is 2 layers with no intervening fat. Clinically it does not make a big difference.

Anterior extent and relationship to the N-L crease  The anterior extent is also debated. i. Mitz and Peyronie stated that the SMAS extended to the N-L fold (the laxity above the crease). ii. Owsley and others that it inserted into the crease. iii. Joost and Levet that it excluded the orbicularis oris. iv. According to Yousif, the SMAS is in continuity with the superficial part of the orbicularis oris, ie it extends beyond the N-L fold. He also noted that the SMAS was in anatomical continuity with the pre-orbital part of the orbicularis oculi, the risorus and the depressor anguli oris. Hamra agrees with Yousif that the SMAS extends across the N-L fold.  Importance of this is whether pulling on SMAS here deepens or lessens the fold i. Barton – specific attachments of SMAS to mimetic muscles and skin. They suggest releasing this by breaking thru the investing fascia at the lateral border of zygomaticus major and continuing anteriorly in the subcutaneous plane.

Superior Extent  Mitz and Peyronie state that the SMAS is continuous with the frontalis (and thus the galea).  Yousif sort of agrees (Fig1, 2, 3 and 3a). He states that 1 cm below the zygomatic arch, the SMAS becomes indistinct. The SMAS is continuous with the galea, or rather its inferior extension, the superficial temporal fascia. The frontal br of VII lies on the deep surface or the SMAS-superficial temporal fascia-galea.  According to Abdul Hassan: the TPF = the superficial temporal fascia  Rees: In the temporal region, the SMAS layer is analogous to the superficial temporal fascia. Gosains dissection show that the 2 layers are not in continuity, but they are 4

analogous to each other and were it not for the SMAS petering out just below the arch, the two would be in continuity.

LIGAMENTS OF THE SMAS According to Furnas, 2 ligaments that run between bone and dermis:(extend between the periosteum of the zygoma and mandible and the dermis )

Osseocutaneous ligaments 1. Zygomatic ligament 2. Mandibular ligament

Platysma fascial condensations to dermis 3. Anterior platysma cutaneous ligament 4. Platysma auricular ligament

To these 4, Stuzin added a 5th and a 6th. 5. Masseteric cutaneous ligaments  condensation of superfl and deep fascia 6. Parotid cutaneous ligaments.  condensation of superfl and deep fascia

The ligaments are important for 2 reasons: 1) They restrain the facial skin against gravity (especially the osseo-cutaneous ligs) 2) They need to be divided or repositioned (suture suspension) at the time of facelift. 5

Schematic drawing of the location of the main retaining ligaments of the face. A repres- ents the region of mastication; B is the anterior mimetic mobile region of the face. (1) Bossé and Papillon's zygomatic ligament. (2) The parotid cutaneous (3) Stuzin's masseteric-cutaneous ligaments. (4) The lower orbicularis ligament of Hinderer et al. (5) Fur- nas' platysma-auricular ligament, (6) anterior platysma-cutaneous ligaments, and (7) mandibular ligament delineate the anterior border of the jowl area. (8) orbital ligament (named by Knize)

1. Zygomatic Ligament  Lie at the anterior, inferior border of the arch, 42-45 mm anterior to the crease of the tragus at the inferior border of the zygomatic arch.  Owsley described them as a vertical septum from the masseteric fascia to the SMAS.  They ascend through the SMAS and then arborise in the fascial-fatty layer (malar fat pad) before inserting into the dermis. 6

 Yousif states that these ligaments are in continuity with the dense fibrous attachments below the infra-orbital rim, thus this whole complex holds up the tissues of the midface. Any facial surgery medial to this point necessitates division of these ligaments.  The ligament is, intimately associated with the zygomatic branches of the facial nerve.  With age, these ligaments become lax, leading to inferomedial migration of the malar fat pad and formation of the nasolabial fold.

2. Mandibular Ligament  The osseocutaneous mandibular ligament arises from the parasymphysial mandibular body located 3-4 mm above the mandibular margin and 40-45 mm from the midline of the chin.  inserts into the skin inferior to the insertion of the depressor anguli oris, interdigitating with the platysma, which lies deeper to the depressor  If this ligament is left intact and employed as an anchor to allow the jowl lift to pull against it, the perioral area assumes a much more natural look postoperatively.

3. Platsymal auricular ligament  anchors the dermis of the inferior auricular skin to the platysma

4. Anterior platysma-cutaneous ligaments  aponeurotic condensations that tether the skin of the middle and anterior cheek to the platysma and SMAS.

5. Masseteric cutaneous ligament  pass from the region of the anterior border of the masseter muscle toward the dermis.  may represent the points of fusion between the SMAS and the parotideomasseteric fascia layers.  With age, laxity of the masseteric ligaments allows the inferomedial descent of the tissues and contributes to the formation of the labiomandibular fold or jowl.  The anterior limit of the jowl is the mandibular ligament.  The masseteric ligaments need to be freed to achieve skin advancement during facelifting. The masseteric ligament also approximates the midcheek furrow of aging and the posterior boundary of the mimetic muscles.

McGREGOR’S PATCH (1972) A critical area over the malar eminence. 1. Branches of the VII n are superficial and prone to injury. 2. Usually a perforator in this area which bleeds profusely when cut. 3. Zygomatic ligament

MUSCLES 7

Mimetic Muscles  Muscles are not only important for movement, but also support the soft tissue of the face. SMAS merges with and invests the facial muscles, especially zygomaticus major and orbicularis oris.  The muscles of the face are arranged in 4 layers (Freilinger et al), the facial nerve running between the deepest layer and the one above. The 3 superficial layers therefore protect the nerve. i. Superficial: orbicularis oculi, zygomaticus minor and depressor anguli oris ii. LLSAN, zygomaticus major, risorius, depressor labii inferioris, platysma iii. orbicularis oris, levator labii superioris iv. Deep: buccinator, levator anguli oris, mentalis  When dissecting sub-SMAS (as in a composite rhytidectomy), it is recommended to move to a more superficial plane when zygomaticus major is encountered in order to preserve the nerve. The dissection thus continues superficial to that muscle.

Perioral Muscles

The modiolus is a tendinous thickening at each commissure that serves as an attachment site for several of the upper and lower lip muscles

The perioral musculature can be classified into 3 groups based on insertion. Group I muscles insert into the modiolus, group II muscles insert into the upper lip, and group III muscles insert into the lower lip.

Group I i. Orbicularis oris ii. Buccinator iii. Levator anguli oris iv. Depressor anguli oris v. Zygomaticus major vi. Risorius

Group II i. Levator labii superioris ii. Levator labii superioris alaeque nasi iii. Zygomaticus minor

Group III i. Depressor labii inferioris ii. Mentalis iii. Platysma

Group I muscles

Orbicularis oris  forms a sphincter around the mouth. 8

 purses the lips and presses them against the teeth upon contraction.  Divided into superficial and deep. Deep (intrinsic)  Functions in catching food with a sphincteric action  Consists of pars marginalis (forms the tubercle) and pars peripheralis  Deep orbicularis oris originates from the moidiolus on each side, it is horizontal with continuous fibres passing from one commissure to the other across the midline,  It lies close to the inner mucosal surface  At the commissure, the curled border of the upper lip muscle divides, and the curled border of the lower lip muscle inserts between these slips  When the fibres shorten to close the lips, the margins flatten out and the interdigit- ation provides a scissor-like motion which seals the angles of the mouth Superficial (extrinsics)  Functions in facial expression  Upper (nasal bundles) and lower bundles (nasolabial bundle) in the upper lib  Lower bundle o decussate in the midline and insert into the skin lateral to the opposite philtral groove forming the philtral columns. o philtral dimple centrally is depressed as there are no muscle fibers that directly insert into the dermis in the midline  Upper bundle o common insertion of zygomaticus major and minor, levator labii superioris, nasalis (alar) o inserts into the anterior nasal spine, the septo-premaxillary ligament, and the nostril sill, passing deep to the alar base  Innervated by buccal and marginal mandibular nerves from its deep surface.  Cupids bow is due to lateral upward pull by levator labii superioris (inserting into the vermilion border lateral to the median groove) and the downward pull of orbicularis centrally.

Buccinator 9

 Arises from the posterior alveolar process of the maxilla, the pterygomandibular raphe, and the body of the mandible and inserts into the modiolus.  Functions to press the lips and cheek against the teeth (manipulate food bolus)  Receives motor innervation from the buccal branches that enter the muscle on its superficial surface.  The parotid duct pierces the buccinator after it crosses the anterior edge of the masseter muscle.

Levator anguli oris  Arises from the canine fossa of the maxilla below the infraorbital foramen  Descends vertically to insert into the modiolus.  Action is to superiorly elevate the commissure.  Innervated by buccal and zygomatic branches on its superficial surface.  The facial artery and infraorbital nerve travel in a plane on its superficial surface

Depressor anguli oris  Arises from the oblique line on the anterior mandible below the canine and premolar teeth.  Pass superiorly and twist medially to insert on the modiolus.  Innervated by marginal mandibular branch on its deep surface.  Functions to depress and laterally move the commissure.

Zygomaticus major

 Arises from the zygomatic bone just anterior to the zygomaticotemporal suture line  Passes inferiorly and medially over the buccinator and levator anguli oris to insert on the modiolus.  Superiorly, its fibers are deep to the orbicularis oculi muscle.  Inferiorly, the fibers are superficial to the facial vessels and facial nerve. 10

 Innervated by zygomatic and buccal branches of the facial nerve from its deep surface.  Elevates and laterally moves the commissure.

Risorius  Arises from the parotid fascia and passes medially and anteriorly in a transverse plane to insert on the modiolus.  Buccal branch/deep surface  Draws the commissure laterally and produces the sardonic smile.

Group II muscles

Levator labii superioris  Arises from the inferior orbital rim on the maxilla, deep to the orbicularis oculi, and superior to the infraorbital foramen.  Pass inferiorly to insert into the dermis of the upper lip skin and into the orbicularis oris muscle.  Elevates the upper lip  Buccal branch/deep

Levator labii superioris alaeque nasi  Arises from the frontal process of the maxilla.  Pass inferiorly to insert on the lateral nasal alar cartilage, the dermis of the upper lip, and the orbicularis oris muscle.  The buccal branch of the facial nerve innervates this muscle.  Dilates the nostril and elevates the upper lip.

Zygomaticus minor  Arises from the zygoma deep to the orbicularis oculi and just lateral to the zygo- maticomaxillary suture.  Pass inferiorly to insert on the upper lip.  Buccal branch of the facial nerve innervates this muscle.  Elevates and pulls the commissure laterally. Its contraction contributes to the nasolabial fold.

Group III muscles

Depressor labii inferioris  Arises from the anterolateral mandible and medial to the insertion of the depressor anguli oris.  Lies deep to the depressor anguli oris.  Pass superiorly to insert in a fan shape into the lower lip dermis and orbicularis oris.  The marginal mandibular branch of the facial nerve innervates this muscle.  The depressor labii inferioris acts to depress the lower lip and pull it slightly laterally. 11

Mentalis  A paired central muscle of the lower lip.  Arises from the anterior midline mandible and inserts into the dermis of the chin skin.  Intraorally, its insertion can be observed at the base of the midline gingivolabial sulcus, which deepens laterally to the centrally positioned muscle belly.  Eelevate the lower lip. The insertion site of the mentalis fibers into the dermis can be observed in the pout expression.  The marginal mandibular nerve innervates the mentalis on superficial surface.

Platysma  Paired sheet of muscle in the anterior neck.  Vestigial remnant of the panniculous carnosus  Arises from the fascia overlying the pectoralis major and deltoid muscles  Superiorly, the platysma is continuous with the SMAS - the most anterior fibers decussate the the midline at variable levels below the chin and insert into the mentum. The central fibers insert into the body of the mandible and the more posterior fibers turn anteriorly and blend closely with the fibers of the risorius muscle.  A lip depressor.  Innervated by cervical branch.  The medial borders tend to become redundant and form bands in the neck.  Deep to platysma lies the superficial (investing) layer of the deep cervical fascia. The plane between it and platysma is relatively avascular.

 3 patterns of decussation (de Castro) 1. Type 1 (75%) – decussation occurs 1-2cm below edge of mandible 2. Type 2(15%) – decussates from thyroid cartilage to mandible 3. Type 3(10%) – no decussation  Type 3 predisposes to turkey gobbler neck 12

MOTOR NERVES - FACIAL NERVE  Injury to facial nerve is obviously the most undesirable Cx of facelift.  Occurs in 0.4-2.6%, irrespective of whether subcutaneous or sub-SMAS.  Temporal and MM are the branches most at risk.  Interconnections between the zygomatic and buccal branches are noted in over 70% of cases, whereas interconnections between the temporal or marginal mandibular branches to other facial nerve branches occur in less than 15% of cases  Nerve injury more common with repeat facelift (especially temporal br).  Most recover.  Nerves innervate their respective muscles from the deep surface. 13

1. frontal branch of facial nerve

 By the time the nerve crosses the arch is has divided up into 2 or 3 branches.  The nerve is closely applied to the deep aspect of the superficial temporal fascia, deep to which is loose areolar tissue.  landmarks – 1. runs in a line from 0.5 cm below the tragus to 1.5 cm above the outer upper part of the eyebrow (Pitanguy) 2. 2cm from the bony acoustic meatus (horizontal line) 3. junction of median 1/3 and lateral 1/3 of zygomatic arch 4. about 24 mm from the point where the superior border of the zygomatic arch meets the helix – danger zone is 8 mm in width and begins 19 mm in front of the helical root.  it may go as much as 4 cm above the lateral eyebrow. 14

 The nerve becomes superficial halfway between the anterior hairline and the lateral canthus.  The safe plane of dissection therefore goes deep to the superficial part of the deep temporal fascia above the arch, whereas below the arch, the plane is subcutaneous. A bridge of aponeurotic tissue is maintained between the 2 planes of dissection which contains not only the nerve, but also the zygomatico-orbital artery.  In repeat facelifts, the loose areolar tissue becomes scarred and the safest plane of dissection above the arch is thus subperiosteal .  According to Rees, there is a < 10% chance of recovery if this branch is injured, even if it is repaired.

2. Zygomatic and Buccal branches  Less often injured because on a deeper plane and consequences of injury less severe as 70-90% intercommunication rate.  The nerves lie very close to the surface of the masseter in the parotido-masseteric fascia.  zygomatic branch develops from the upper or anterior border of the parotid gland, 2.7 ± 0.3 cm from the anterior rim of the bony external acoustic meatus. In masseteric fascia, it develops into two to three branches, which can be divided into the upper and lower branches. The upper branch is thin and superficial, running at the lower aspect of the medial third of the zygomatic arch, innervating the lateral orbital orbicularis oculi muscle directly or passing through the upper third surface of the zygomaticus major to innervate the overlying lower eyelid orbicularis oculi muscle. The lower branch has a larger diameter and deeper position than the upper one; it is located 1.0 ± 0.3 cm inferior to it, develops into several thinner branches outside the zygomaticus major, and runs through the superficial and deeper surfaces of the muscle. The upper and lower zygomatic branches may join together at the surface and beneath the zygomaticus major  Medial to the anterior border of the masseter, the nerves lie superficial to the buccal fat pad and in the same plane as Stenson’s duct.  Relationship to ligaments: the zygomatic br passes through the zygomatic ligament; the buccal br passes through the masseteric cutaneous ligaments.  In 75% of cases, buccal branch was inferior to parotid duct and 25% of cases crossed the duct from superior to inferior.

3. Marginal mandibular  exits the anterior-inferior portion of the parotid near the angle of the mandible and re- mains deep to platysma and the investing cervical fascia.  Near the mandibular mid-body, the marginal mandibular nerve swings upward and perforates the deep cervical fascia near the mandibular border to continue within the fibroareolar tissue between the deep fascia and platysma.  crosses the anterior facial artery to innervate the deep surface of the depressor quad- ratus labii inferioris and mentalis muscles. It may anastomose with cervical and buccal branches that supply the depressor anguli oris and the cephalic portion of the platysma.  The vulnerable point for injury of the marginal mandibular nerve is after it exits the deep cervical fascia and courses up over the anterior mandible in the region of the fa- 15

cial artery. Nerve injury can occur during dissection in the superficial subcutaneous layer if the platysma is penetrated in the region of the anterior jowl with scissors or even with a liposuction cannula.  Dingman and Grabb (100 cadaveric dissections) of marginal mandibular nerve: i. posterior to the facial artery: in 81% of cases the nerve lies above the inferior border of the mandible and in the other 19% it lay within 1 cm of the inferior border of the mandible; ii. anterior to the facial artery: the branches of the MM were always above the inferior border of the mandible  Subsequent studies have shown that the MM nerve can loop down up to 4 cm below the mandible.  MM br pass through the mandibular ligament which corresponds to the anterior border of the jowls. If the mandibular ligament is to be released to provide an effective submental lift, care must be taken.

Sentinel vein (De la Plaza)  vein is located about 5 mm lateral to the frontozygomatic suture line and is a tributary of the internal maxillary vein draining the temporal region  consistently found to lie lateral to the lateral orbital rim, passing from the subcutaneous layer through the temporoparietal fascia, then through a perforation or attenu- ation in the deep temporal fascia to the temporalis muscle.  temporal division of the facial nerve is usually found cephalad to the sentinel vein and, at the nearest point, they were a mean distance of 6.4 mm apart (range, 2 to 9 mm) 16

Landmarks to identify the zone of caution. A, the point where the zygomatic arch meets the helix; B, the angle between the zygoma and the lateral orbital rim (superior border); C, point of intersection between the two lines drawn from the anatomical landmarks; D, zone of caution; E, sentinel vein; F, zygomaticotemporal nerve (sensory nerve); G, temporal branch of the facial nerve where it crosses the zygomatic arch (superior border); H, temporal branch of the facial nerve; I, supraorbital notch; L, mental foramen.

SENSIBILITY  Facelift disrupts sensory nerves to the skin and thus facial sensation may be altered.  Usually this is transient and improves over a few mths.  The only major sensory nerve is the greater auricular nerve - The commonest nerve injured in facelift.

GREATER AURICULAR NERVE  Sensory branch from the cervical plexus important in supplying the ear lobe. 17

 Lies deep to the superficial layer of the deep investing fascia on the sternocleido- mastoid muscle as it traverses from posteroinferior to anterosuperior to emerge in the vicinity of the infra-aural region, where the skin is firmly attached to the sternocleido- mastoid muscle.  Ascends up from behind the SCM to the ear lobe which it supplies.  6.5 cm below the EAM, it lies halfway across SCM.  Lies below SMAS and just posterior to EJV.  Mastoid sutures in the SMAS must be placed well back to avoid injury to this nerve - 1.5 cm behind the ear lobe.

INFRAORBITAL NERVE  Deserves attention during subperiosteal lifting in the region of the cheek via an in- traoral approach.  The nerve emerges from the infraorbital foramen 8mm below the rim (line of medial limbus, and in line with the supraorbital nerve and 1st maxillary premolar), sand- wiched between the superficial surface of the levator anguli oris and the deep surface of the levator labii superioris muscles, to provide sensory innervation to the cheek and lip.

SUPRATROCHLEAR NERVE  in danger during dissection of the corrugator muscle in forehead lifting.  Average distance from the nasion to the frontal notch/foramen - 25 mm

SUPRAORBITAL NERVE  must be protected during an endoscopic subperiosteal forehead lift by not extending the blind dissection beyond 2 cm of the supraorbital margin.  Average distance from the nasion to supraorbital notch/foramen 31 mm  2 branches (medial/superficial and lateral/deep)  Deep branch travels about 1cm medial to superior temporal line

MENTAL NERVE  must be protected during subperiosteal maneuvers on the mandible  foramen in between 1st and 2nd premolar, 8-10mm above rim

VESSELS (Fig 11-13)  The usual plexi are seen in the face: subdermal, fascial.  External carotid artery has a number of branches: A. From STA 1. Transverse facial 2. Zygomatico-orbital 3. Terminal branches

B. From the facial artery 1. Submental 18

2. Inferior labial 3. Superior labial ( alar br, columella br) 1. Angular artery  lateral nasal artery (external angular artery)

 Internal carotid artery also supplies the face: 1) Supratrochlear 2) Supraorbital 3) Dorsal nasal artery  Rich anastomotic network exists between the 2 systems.

Arterial Territories of the Face and Scalp (Whetzel and Mathes PRS 1992)

Anterior face  small, densely populated musculocutaneous perforating arteries from facial and infraorbital, infratrochlear vessels  These vessels form the pedicle on which most facelift flaps are based.

Lateral face  The deep plexus associated with the parotido-masseteric fascia is deep and separated from the subdermal plexus by the SMAS.  The SMAS is thus penetrated by a few, large, fasciocutaneous perforators from transverse facial, submental and zygomatico-orbital arteries. These vessels are usually divided when doing a facelift.  transverse facial perforating artery provides the major direct blood supply to the lateral cheek and preauricular area following rhytidectomy if preserved. This perforator occupies a constant anatomic location 3.1 cm lateral and 3.7 cm inferior to the lateral canthus with 95 percent tolerance limits of +/-1.1 cm – near the zygomatic ligament (Whetzel and Mathes PRS 1997)

Forehead and Scalp  small, densely populated fasciocutaneous perforators supply the scalp (occipital, superficial temporal, and posterior auricular arteries)

Effect of facelift on these vessels  The deeper the plane of facelift, the less the effect.  Subperiosteal - No effect on choke zones. Composite - Leaves most vessels intact.  Separate subcutaneous dissection and lifting of SMAS - Interrupts most choke zones.

THE N-L FOLD  As the SMAS passes anteriorly and into the muscles of the upper lip, it becomes atten- uated.  Traction on the SMAS has little effect on the N-L fold and medial cheek skin and can even deepen the fold. 19

 Various methods of dealing with the problem of the N-L fold.  Barton suggests that when doing a sub-SMAS facelift, the plane of dissection should become more superficial when zygomaticus major is encountered and should continue anterior to the muscle in a subcutaneous plane. The SMAS is thin and ectatic at the N- L fold, but is anchored more medially to the muscles of the upper lip. By doing the dissection in this way, traction on the SMAS will elevate the medial cheek skin smoothing the N-L fold.  Other ways of dealing with the N-L fold are to either fill it (autologous tissue or pros- thetic), to suction above it, to excise it, etc.

THE FAT PADS The Malar Fat Pad  Subcutaneously located from malar region to N-L fold.  Located superficial to SMAS and muscles.  Triangular in shape with base at N-L fold and apex at the zygomatic prominence.  Descent leads to deepening of the N-L fold. Ascent is associated with a more youthful appearance (sub periosteal and composite facelift).

The Buccal Fat Pad  Specialised fat resembling orbital fat in colour (distinctly yellow), function and form.  Function 1. protection/cushioning 2. Contributes to cheek and facial contour. 3. muscle gliding  Occupies the masticatory space. Resembles an egg yolk in size, colour and consist- ency.  Lies deep to the deepest layers of facial muscles, superficial to buccinator (below) and temporalis (above) and deep to masseter. Facilitate muscle gliding. Related to zygomatic and buccal brs of VII and to parotid duct (which pierces the fat pad).  Consists of a central body under the zygomatic arch and 3 extensions: i) Deep temporal temporal (superiorly, deep to zygoma under the deep leaf of the deep temporal fascia) ii) pterygoid process(extends backwards, deep to the ramus of the mandible) iii) buccal process/extension (most superficial and lies in the cheek, below the parotid duct and in front of masseter)

 The body and buccal extension contribute to cheek form.  Removal of the central and buccal portions can reduce cheek fullness and enhance the malar eminence. Can be approached through a buccal sulcus incision, through buccinator and with division of surrounding fascia, then teased out. Can also be removed during open or endoscopic facelift from in front of masseter.  Fat can also be used as a free graft or as a pedicled flap  Potential for damage to buccal branch as 30% passes through the buccal extension.  es with age. 20

The Jowl Fat  This lies pre-platysma and can be removed by SAL, endoscopically or open.

Submental Fat  Accumulation of submental fat causes the cervicomandibular angle to increase

 A youthful neck is associated with a cervicomandibular angle close to 118°  Fat may be pre or post-platysma. Most is located pre-platysma  Suction may be done pre or subplastysma (risky). If using UAL, avoid subplastymal

Submandibular gland (PRS Sept 2003)  Submandibular fullness may be improved (SMAS suspension, platysma placation) or worsened (platysma transaction) by facelift surgery  Management is controversial  The facial artery passes behind the posterior digastric muscle and ascends vertically to lie posterior to the submandibular gland or is interposed between the deep and superficial lobes.  The facial vein is found between the deep and superficial lobes at the lateral extent of the capsule.  The hypoglossal nerve is found posterior to the tendinous juncture of the anterior and posterior digastric muscle deep within the visceral layer of the neck  The lingual nerve is located cephalad-medial to the deep lobe; anterior to the submandibular duct which crosses behind the lingual nerve near the mylohyoid border.  marginal mandibular nerve is identified approximately 3.7 cm (range, 3 to 4.2 cm) cephalad to the inferior limit of the submandibular gland

The youthful neck 21

Visual criteria for a youthful neck include (1) distinct inferior mandibular border, (2) sub- hyoid depression, (3) visible thyroid cartilage bulge, and (4) submental line/sternocleido- mastoid border angle of 90 degrees or cervicomental angle between 105 degrees and 120 degrees