The platysma is a broad, thin muscle situated in the subcutaneous plane of the neck that is a key instrument for controlling neck and lower face contour. It originates from the pectoralis and deltoid fascia caudally, with insertions to the mandibular symphysis and superficial musculoaponeurotic system (SMAS) cranially. It receives its main blood supply from the submental artery, which is a branch of the facial artery, and receives a secondary supply from the suprasternal artery. Innervation is from the facial nerve (cervical branch), not the cervical plexus. The platysma is not a continuation of the deep cervical fascia, which, instead, lies beneath it. Three different anatomic patterns related to its decussation were described by de Castro1 in 50 patients (Fig. 113.1). Type I was most common (75%), in which limited decussation of the muscles for 1 to 2 cm below the mandibular symphysis was present. In type II, the decussation was more extensive and passed down to the thyroid cartilage. In type III, no decussation was present. A subsequent anatomic study was undertaken by Kim et al2 in 70 Korean patients; this showed that subtypes I and II were equally common (43% each), and this may reflect racial differences. The benefit of a midline decussation is the provision of a supportive sling without which the free medial edges of the muscle can fall away laterally creating vertical platysmal bands. Mandible Hyoid Type I Type II Type III Fig. 113.1 Three anatomic patterns of the neck. A, Type I is most common and occurs in 75% of individuals. This type demonstrates a limited decussation of the platysma muscles, extending 1 to 2 cm below the mandibular symphysis. B, Type II occurs in 15% and demonstrates decussation of the platysma from the mandibular symphysis to the thyroid cartilage. C, Type III occurs in 10% and demonstrates no decussation or interdigitations.
2. Kim HJ, Hu KS, Kang MK, Hwang K, Chung IH. Decussation patterns of the platysma in Koreans. Br J Plast Surg 2001;54(5):400–402 oral commissure. The marginal mandibular nerve is at risk of damage during neck rejuvenation procedures and neck dissection surgery. The danger zone is usually within a circle of 2-cm radius, located 2-cm posterior and inferior to the oral commissure overlying the lower border of the mandible. This region corresponds to where the facial vessels cross the lower mandibular border and the nerve. The marginal mandibular nerve originates from the lower division of the facial nerve and passes close by the tail of the parotid, from lateral to anteromedial in the subplatysmal plane. It is important to remember this, as any subplatysmal dissection in the region of the lower mandibular border can risk iatrogenic damage. The nerve travels close to the lower border of the mandible and most commonly runs above the lower border throughout its course, although this can change with advancing age. Before the point at which it crosses the facial vessels, it runs above the inferior border in more than 80% of cases. Beyond the facial vessels, all of its branches are above the inferior border. The marginal mandibular nerve innervates the lower lip depressors, 1004 Part VII ■ Aesthetic Surgery the risorius, and part of the orbicularis oris. It does not usually innervate the platysma, as this is innervated by the cervical branches. Injury to it leads to weakness of the lower lip with an inability to evert the lips.1–3
3. Seckel BR. Facial Danger Zones: Avoiding Nerve Injury in Facial Plastic Surgery. 2nd ed. St. Louis, MO: Quality Medical Publishing; 2010: xi, 52p The great auricular nerve is at risk of damage during neck-lift and face-lift surgery. The main danger zone is located within a circle with a 3-cm radius dropped approximately 6.5 cm inferior to the external auditory canal. This corresponds to the midpoint of the sternocleidomastoid (SCM) muscle and the nerve emerges beneath the SCM just below this site, which is also known as McKinney’s point. This nerve supplies sensation to the lobule of the ear via its lobular branch as well as the lower anterior and posterior aspects of the ear. It is the most commonly injured nerve during a face lift because of its superficial location; so, it is important to discuss this possibility with patients preoperatively.1–3
The digastric muscle is so named because it has two heads. Each of these has a different bony origin (anterior belly originates from the mandibular symphysis; posterior belly originates from the mastoid process), but they share a central tendon. The posterior belly is longer than the anterior belly and together they form the lower border of the submandibular triangle. Embryologically they originate from different branchial arches and so have different motor innervation. The anterior digastric develops from the first arch and has trigeminal innervation. The posterior digastric develops from the second arch and has facial nerve innervation. The digastric muscles are sometimes addressed during neck surgery to debulk them if they are overly prominent.1–4
Tethering of the mandibulo-cutaneous ligament produces the appearance of jowls. These can be assessed by inspection and palpation near the lower border of the mandible at the lateral edge of the chin. Assessment of jowl volume with the patient supine helps plan surgical intervention. An excess of soft tissue alone may be treated with liposuction, whereas laxity of the deeper soft tissues will require SMAS-platysma tightening. The masseteric-cutaneous ligament is also relevant to the formation of jowls, as this attenuates with age allowing ptosis of the midfacial tissues. The platysma-auricular ligament is also relevant to neck-lift procedures because it marks the posterior extent of the platysma and also the site where the platysma is often anchored to provide elevation of the neck. Weakening of the zygomatico-cutaneous ligament causes downward migration of the malar soft tissues and creates redundant skin that hangs over the fixed nasolabial fold.1-4
Fat is located in a number of different subunit areas within the lower face and neck. The most inferior facial fat compartment is the jowl area and this is adherent to the depressor anguli oris, which forms the medial boundary of the compartment. The inferior border is formed by a membranous fusion of the platysma muscle.1 Fat within the neck itself may be located above, below, or between the two platysma muscles. Supraplatysmal fat is bordered by the anterior border of mandible superiorly, the sternal notch inferiorly, and the anterior border of SCM laterally. It contains 45% of fat in the neck1, approximately 14 to 15 g in many patients and is the primary target for liposuction.2 The subplatysmal fat is bordered by the anterior border of mandible superiorly, thyroid cartilage inferiorly, and the anterior border of SCM laterally. It contains 31% of fat in the neck,2 approximately 3.7 to 5.5 g and care must be taken if removing this fat, as over-resection here can lead to scarring between the platysma and mylohyoid muscle, causing a contour deformity which is difficult to correct. Furthermore, deeper liposuction between the two platysma muscles risks damage to the anterior jugular veins, which can cause significant bleeding and bruising (Fig. 113.2).3 There are five periauricular fat compartments relevant to the lower face and neck contour; these are the superior, middle, inferior, subauricular, and preauricular areas. The inferior and subauricular compartments are divided by the subauricular membrane, which can be an area of tethering in the lateral neck. The subauricular membrane is associated with the great auricular nerve.4 There is no specific central chin compartment, and this would probably lie over mentalis between the jowl fat areas if it was described. Submandibular gland Subplatysmal fat Digastric muscle Interplatysmal fat Skin Mylohyoid muscle Hyoid bone Subcutaneous fat Platysma muscle Fig. 113.2 Practical anatomy of the neck. 1006 Part VII ■ Aesthetic Surgery
When examining a normal neck, the SCM muscle should be visible at its anterior border. Ellenbogen and Karlin1 classified features of the youthful neck that change with age. Features of a youthful neck involve a visible thyroid cartilage (not the thyroid gland), subhyoid depression (not the hyoid), and the inferior mandibular border. A normal cervicomental angle of between 105 and 120 degrees should also be observed. The submandibular gland and digastric muscle should not be visible. A bulge below the mandibular rim within the submandibular triangle may represent a ptotic or enlarged submandibular gland. Sometimes prominent digastric muscles may be observed bulging below the inferior mandibular border. This may only become apparent following neck rejuvenation.1-3
Patients commonly request treatments to the neck to improve its contour and this may be focusing on the skin, platysma, fat, or other deeper tissues. Traditionally, fat excesses have been treated with liposuction and this still remains a popular approach to the neck. However, there are nonsurgical alternatives that should be considered. Kybella is a preparation of deoxycholic acid that can be injected into the subcutaneous tissues in order to cause adipocytosis (fat dissolving). It should be injected in 0.2-mL aliquots spaced 1 to 1.5 cm apart in the preplatysmal, submental fat using a 30-gauge, 0.5-inch needle. It usually requires multiple treatment sessions (up to 6), spaced 1 month apart. Most patients experience a response within 2 to 4 treatments.1 It should be avoided in patients with preplatysmal bands, skin laxity, prior submental surgery, dysphagia, or facial nerve paralysis. It can cause damage to the marginal branch of the facial nerve leading to lip and chin weakness and this must be discussed with the patient prior to treatment. Ulthera is a technique that uses microfocused ultrasound to tighten skin rather than deal with adipose tissue excess. It can cause thermally induced contracture of tissue in addition to stimulating collagen and elastin remodeling. It affects a very small area of dermis or SMAS but spares the epidermis. It is thought to work best in patients with a BMI < 30, although its use should not be kept exclusively for this patient group. Vobella is a type of hyaluronic acid that is used for superficial injections as a facial filler. It is commonly used for lip enhancement. This would add, not subtract, volume to the area. Botulinum toxin is used in the neck for management of platysmal bands, particularly where there is little or no skin excess. Up to 20 units of neurotoxin is typically injected per band. Potential complications include dysphagia at high doses, edema, ecchymosis, neck discomfort, and weakness. Use of neurotoxins in the neck should generally be reserved for patients with good skin elasticity and minimal submental fat. Otherwise, results may be indiscernible, and benefits outweighed by the risk of dysphagia. Triamcinolone is a glucocorticoid that is injected into the skin to soften scars (particularly hypertrophic or keloid types) or used to help musculoskeletal injuries such as tennis elbow, carpal tunnel, or De Quervain’s. It is not used in the neck as part of a facial rejuvenation procedure unless there are firm areas of scar post–neck surgery, which are resistant to massage therapy.1–4
Selection of an appropriate technique for neck rejuvenation is highly patient specific and needs to be chosen to address the key areas of concern to the individual patient. The patient in this scenario has multiple problems to be dealt with. She has excess submental fat and platysmal banding, so will require an open submental approach to her neck. This entails resection of fat with platysmal midline plication. She will also require a lateral face lift with scars placed around the ear in order to address her skin excess and jowls. The other techniques would be unlikely to provide her with a satisfactory improvement addressing all the issues present.1–3
Selection of appropriate procedure in neck rejuvenation is based on the parameters which need to be addressed. The main approaches are liposuction only, a submental neck lift, an isolated neck lift, a short scar face and neck lift, or a full--scar face and neck lift. These may be performed with additional adjunctive procedures where required. The patient in this scenario has moderate subcutaneous fat without subplatysmal fat excess as evidenced by the skin pinch test. She could therefore be a good candidate for liposuction only but will also need to have her platysmal bands treated, because these are likely to become evident at rest following liposuction. For this reason, she should have liposuction combined with an open submental approach. If her skin pinch test had revealed a diminished pinch size during animation, then this would suggest she had evidence of subplatysmal fat, and an open submental approach to remove this would be indicated too. In patients in whom there is skin excess and facial tissue ptosis, a face and neck lift approach need to be combined, with acceptance of the increased scars this would create.1–3
Neck liposuction carries a risk of over-resection of fat, which will lead to suboptimal results. This is difficult to correct, so it is better to slightly under-resect instead. Even small volumes of aspirate can make a significant 1008 Part VII ■ Aesthetic Surgery difference to aesthetics (e.g., 5–10 cc). When undertaking liposuction of the neck, some key principles should be employed. Wetting solution containing epinephrine should be infiltrated before skin preparation and allowed to take effect for 10 minutes. Three incisions are usually required, especially if there is lateral fat to be harvested (a single submental incision is combined with two postauricular incisions). This approach facilitates feathering which can be useful to minimize irregularities. Small, flat cannulas (2–3 mm) should be used with a single hole facing toward deeper tissues, ensuring that no more than one or two passes are made within a given tunnel. (Multihole cannulas are normally used for infiltration, not harvest, and a 7-mm cannula would be too coarse for the detailed contouring required in the neck.) Liposuction is intended to treat subcutaneous fat excess, not subplatysmal fat, which would risk damage to other subplatysmal structures such as blood vessels and nerves. If there is subplatysmal excess, an open approach is required. A drain is not required, but a compression garment should be worn.1,2
The submental approach to the neck is very useful as it allows manipulation of a number of key areas with minimal visible scarring. The main indications are for patients with platysmal banding that will benefit from plication or other maneuver, and where there is modest or no skin excess and deeper fat manipulation is required. It can address some skin excess if wide undermining is performed, but it may be better to use additional periauricular or lateral incisions to facilitate this instead. It is often used in conjunction with liposuction, as this can recontour the preplatysmal fat and then the inter- and subplatysmal fat layers can be further manipulated with direct excision, if needed. The submental incision should be placed just behind the natural submental crease to prevent scarring that may deepen the crease. It is usually made around 4 cm in length. Other adjunctive procedures can be incorporated with the submental approach such as refining the digastric muscles or releasing the mandibular septum and retaining ligament.1–3
Surgery to the face and neck is on a continuum with an isolated neck lift being toward one end of the spectrum and a full-scar face and neck lift on the other. Each of the procedures will address the neck contour in terms of the jowls and neckline, but only the face lift will do this while also addressing the cheeks at the same time. From a technical perspective, a key difference is the length and placement of the lateral scar around the ear as well as the extent of associated subcutaneous undermining. In an isolated neck lift, the scar typically starts at the level of the tragus and extends posteriorly to the retroauricular sulcus. It can be continued onto the retroauricular hairline if there is a large skin excess to be removed. In contrast, a short scar face and neck lift will involve a hairline incision that starts at the sideburn or temple and extends to the lobule. A full-scar face and neck lift will normally have scar extension both in front of and behind the ear, often into the postauricular hairline. In general, within plastic surgery, required scar length will be related to skin excess and this is seen at other body sites such as breast (reduction/mastopexy), abdomen (abdominoplasty), and limbs (brachioplasty and thigh lift). The primary plane of dissection is subcutaneous for both an isolated neck or face and neck procedure is being performed. Only when a sub-SMAS technique is used in the facelift component, will an additional dissection plane be created. The risk of nerve damage, the need for a submental incision, and the need for adjunctive liposuction will apply to each technique. The indications for an isolated neck lift are patients with skin excess and inelastic skin tone who do not want or need to have a facelift. Incorporating a submental incision is generally recommended with this approach to avoid future problems with platysmal banding. The indications for short-scar facelift in conjunction with neck lift include mild jowling, slight neck skin excess (good-quality skin), and patients who do not want scarring behind the ears. Indications for full-scar face and neck lift include patients with more significant skin laxity and jowling, who are accepting of the longer scars in front of, and behind the ears.1–3
During the deep plane component of neck rejuvenation, a number of factors may be addressed. Interplatysmal and subplatysmal fat may be performed in addition to subcutaneous defatting. Care must be exercise when performing subplatysmal fat, as this can lead to tethering of the platysma to the underlying mylohyoid muscle. The anterior belly of digastric may also be resected, but this is most commonly performed tangentially to debulk it, rather than completely excise it. Intracapsular piecemeal resection of the superficial (not deep) lobe of submandibular gland may be performed if the gland is large or ptotic. It is unwise to perform an extracapsular dissection, because this risks damage to the facial artery and marginal mandibular nerve. The suprahyoid fascia is occasionally released to improve the cervical angle in patients with a high hyoid. During the resection of interplatysmal and subplatysmal fat, there are often one or two lymph nodes taken with the specimen, but no attempt is made to specifically resect nodes.1–3
The platysma muscle sling technique involves dividing the platysma horizontally across the entire width. This creates a wide gap that is potentially visible. Retraction of the platysma superiorly results in a window shading effect which has diminished the popularity of this procedure. Platysmal suspension involves placement of sutures along the inferior mandibular border over the superficial fascia on platysma. Platysmal flap cervical rhytidectomy involves a sectional myotomy of the medial edge of platysma so that lateral rotation and advancement of flap edges can be achieved. Corset platysmaplasty is used to eliminate static paramedian muscle bands and reshape the neck. No muscle resection is performed, but platysma is plicated in the midline (Fig. 113.3).1–5
The appearance described is in keeping with excessive submental liposuction that has left visible prominent digastric muscles (Fig. 113.4). Liposuction should be performed with caution in the neck, as this case illustrates. Only small quantities of aspirate should be harvested, and 3 to 5 mm of subcutaneous fat should be left to provide a natural, soft contour. This is a difficult problem to address and may require fat grafting. As with many other plastic surgical procedures, a “less-is-more” approach is often best. Patients want to look better, and feel and look younger and fresher than they started when undergoing aesthetic surgery. They do not (usually) want to look odd or unnatural. If in doubt when operating, it is preferable to under resect tissues giving an improvement that is too subtle rather than one that is overdone and subsequently difficult to correct.1–3
inferioris. Fig. 113.3 Coaptation of decussated platysmal fibers in the midline creates a corset-type effect. Fig. 113.4 Overaggressive fat removal from the neck and submental area has unmasked platysma bands and prominent digastric muscles. The marginal mandibular branch of the facial nerve is at risk of injury during neck-lift procedures. It is most often a transient problem due to neuropraxia or use of local anesthetic agents. Where there is evidence of a neuropraxia and the patient is distressed by their appearance during a smile, it may be helpful to inject neurotoxin into the contralateral depressor anguli oris and depressor labii inferioris. These muscles are responsible for pulling the lower lip down in a full denture smile and injury to the marginal mandibular branch will cause weakness to them on the affected side leading to asymmetry. Weakening the working muscles on a temporary basis can therefore be helpful to improve symmetry. It is unlikely that exploration of the nerve is warranted unless the surgeon had suspected nerve division and if this were the case, primary repair would have been indicated. Injury to the marginal mandibular branch can be differentiated from a cervical branch injury, although the two can have similarities. A cervical branch injury can be distinguished from the former, because the patient is able to evert the lower lip (mentalis muscle and the other depressors are still functioning). Platysma, which is innervated by the cervical branches of the facial nerve, is another lip depressor, hence the overlap in clinical appearances between these two nerve injures. Marginal mandibular nerve injuries are managed conservatively because the majority are due to neuropraxia from traction in the operating room and are expected to resolve spontaneously within 3 months.1,2