Asian Malar and Mandibular Surgery 

Updated: Oct 26, 2018
Author: Charles S Lee, MD, FACS; Chief Editor: Jorge I de la Torre, MD, FACS 

Overview

Background

Aesthetics of the malar-mandibular area

High cheekbones and a distinct mandibular contour characterize the appearance of East Asian persons, especially those of Korean and Japanese descent. In the West, such features are valued, and these areas are frequently enhanced for optimal aesthetic appearance. However, because of the more delicate topography of the typical Asian face, zygomas and mandibular angles that are overly prominent upset the balance, rendering the face overly flat, wide, and square.

In addition to its undesirable aesthetic appearance, in some East Asian cultures the prominent zygoma and mandibular angle have traditionally been associated with negative personal characteristics. On occasion, this can lead to difficulty finding a spouse or discrimination in the workplace.

For these reasons, Asian patients who might hesitate to have other types of surgery are willing to undergo reductive correction of these areas.

Surgeons must recognize that patients seeking bone-contouring surgery, as in other aesthetic surgeries performed on Asian persons, have a desire to improve their appearance; they are not attempting to achieve an appearance more typically associated with a western European person. Preservation of ethnicity remains the cornerstone of aesthetic surgery performed on Asian persons. A mistaken presumption on the part of the surgeon that the Asian patient is seeking an appearance more typically associated with a white person leads to great disappointment for the patient and, eventually, the surgeon.[1, 2]

History of the Procedure

Malar prominence

Onizuka proposed shaving or burring-down the prominent portions of the zygoma, usually the body, through an intraoral incision.[3] For persons with a wide arch, Watanabe proposed resecting the arch.[4] Yang accomplished an infracture of the zygoma with an intraoral-preauricular approach.

Baek et al considered the apparent prominent zygoma in Asian patients to be predominantly a malposition of the zygoma.[5] They proposed a repositioning operation that involves performing an osteotomy at the arch-body junction, performing a second osteotomy at the posterior arch, and repositioning the segment superiorly.

Mandibular angle prominence

Pacific Asian persons frequently have prominence of the mandibular angle and hypertrophy of the masseter muscle. This condition is frequently referred to as benign masseteric hypertrophy, but the relationship of this medical condition, frequently accompanied by pain, to the desires of a patient seeking an aesthetic appearance is not completely clear. Nevertheless, surgical techniques for benign masseteric hypertrophy remain applicable for correction of the prominent mandibular angle.

Resection of the lateral portion of the bone, contouring the posterior border of the mandible with and without removal of the masseter muscle, has been performed. The trend has been to perform the procedure through an intraoral approach whenever possible.

More recently, the use of botulinum A or B toxin has been reported for the correction of masseteric hypertrophy.

Problem

Malar Reduction Surgery

Classification of deformities

The zygoma consists of the body and the arch, either of which can be prominent. Most frequently, the defect involves the lateral portion of the body at the origin of the arch. Therefore, this is the area most frequently addressed surgically, reducing the bulk by burring the anterolateral portion of the zygomatic bone. This is followed by creating an osteotomy just lateral to the burred area, at the body, and another osteotomy at the origin of the arch. The intervening segment is then medially mobilized (in-fractured).[5]

Prominence of the zygoma occurs ideally in isolation; thus, correction leads to a balanced, narrower face. However, it also occurs in association with a broad skull base, as observed by Watanabe.[4] Improvement in facial contour is less dramatic in these patients because bitemporal width remains unchanged even after the intermalar distance has been narrowed. These patients should receive appropriate preoperative counseling. In addition to the clinical features of the deformity, the patient’s perception of the deformity is also important. The surgeon must understand this perception before commencing surgery. This should be discussed during the initial evaluation.[6]

The posterior mandibular angle should be evaluated because correction of the malar area exaggerates any prominence of the mandibular angle. This situation is analogous to the relationship between the nose and chin complex.

Prominent mandibular angle

The mandibular angle can be prominent on the frontal view, lateral view, or both views. The prominence can involve primarily the bone, the masseter muscle, or both. Analysis of the problem by direct examination and by radiographs reveals the problem. The surgical correction is then directed appropriately.

Epidemiology

Frequency

Requests for correction of malar and mandibular angle prominence are common in metropolitan areas with large East Asian populations.[7] Occasionally, male patients seeking a sex change may request these operations.

Etiology

The etiology of this condition is unknown.

Pathophysiology

Although the etiology of benign masseteric hypertrophy is usually unknown, masseteric hypertrophy is thought to be due to work hypertrophy, such as in habitual jaw clenching or teeth grinding. Interestingly, benign masseteric hypertrophy is frequently found among Korean persons who favor dried squid, a tough and chewy delicacy.

The etiology of prominent malar bones is more obscure. Although it can occur in isolation, it frequently occurs in conjunction with benign masseteric hypertrophy. According to Baek et al, hyperostosis of the malar bone may occur at the attachment of the masseter muscle, in the same manner as hyperostosis of the mandible.[8]

Presentation

Patients requesting zygoma reduction surgery may simply wish to have a more balanced appearance. East Asian cultures value a small face, and wide cheekbones appear to make the face bigger. In other cases, patients may attribute some misfortune in their life to the zygomatic prominence and wish it corrected for this reason.

The patient with a prominent mandibular angle generally seeks aesthetic improvement. A prominent jawline creates a masculine appearance that may be undesirable. Because Asian beauty emphasizes subtlety, a prominent jawline throws off the balance of subtle midfacial features (nose, chin) by overpowering the mid face. Reducing the jawline restores the balance. When it comes to the prominent jawline, patients may have a significant muscle component, bone component, or both.

Indications

Indication for malar reduction is in a patient who is emotionally stable and has realistic expectations of the outcome. The ideal patient for cheekbone reduction has a narrow skull base and maxilla but an isolated prominent malar eminence or overly wide zygomatic arch. In these patients, infracture of the zygoma results in a dramatically reduced facial width and a desirable outcome. Zygomatic infracture does not produce the desired result of a patient with a wide skull base because the face remains wide even after the zygomatic infracture.

The ideal jawline reduction candidate has a prominent mandibular angle extending laterally, away from the neck. The technical details of the surgery make it difficult to reduce the bony structures if the mandibular angle curves inward, toward the neck. Patients with hypertrophic masseter muscles in conjunction with a prominent bony component benefit from removal of the inner half of the masseter muscle along with the bone.

Relevant Anatomy

Zygoma

The anatomy related to correction of zygoma fractures remains relevant, except that no orbital component is involved. Bear in mind that the frontal branch of the facial nerve can, on occasion, sustain traction injury. Careful subperiosteal dissection should preclude actual transection of the nerve. Exercise extreme caution when using burs, if used at all, because of the proximity of the facial nerve. When a bur is required at all, the author prefers a guarded bur.

Mandibular angle prominence

Dense fibers attach the masseter along the posterior angle of the mandible, necessitating sharp dissection in this area. The marginal mandibular nerve and facial artery lie at the anterior border of the masseter and are at risk. Vessels, if lacerated, may retract beneath the mandible, necessitating an incision in the neck for control. Preoperative discussion is advisable to make patients aware of the possible need for a 2-cm neck incision to control possible bleeding or remove bony chips that are otherwise inaccessible from an intraoral approach.

Contraindications

Patient selection is critical in these cases. The patient should have realistic expectations of the outcome of surgery. The ideal patient to undergo zygomatic reduction has an otherwise narrow face, and correction of the isolated prominent zygoma can lead to an excellent aesthetic appearance. However, if the patient has a generally wide face (and skull base), zygomatic reduction may not dramatically improve the patient's appearance.

For mandibular angle surgery, preexisting asymmetries and the probability of some postoperative asymmetry should be discussed with the patient. Patients should accept the possibility of a neck incision as necessary under extreme circumstances.

 

Workup

Laboratory Studies

Order routine preoperative laboratory studies, including a CBC count. Order other studies, such as coagulation profiles and ECGs, as indicated.

Imaging Studies

See the list below:

  • Zygomatic reduction: A cephalogram and facial series is usually obtained to assist in surgical planning.

  • Mandibular angle reduction: Obtain Panorex films (to assess the course of the inferior alveolar nerve), submental vertex views (to assess the angle between the mandibular [intergonial] angle), and a lateral cephalogram (to measure the gonial angle, ideally 105-115°, and the mandibular plane, ideally 30°). The preferred angle and contour of the mandibular border is drawn on a duplicate radiographic film and used as a template for surgery.

 

Treatment

Medical Therapy

No medical therapy is available for zygomatic reduction. For mandibular prominence, botulinum toxin (BOTOX®) has been shown to be effective therapy in patients with a large muscle component.[9] The duration of effect is currently under evaluation. Occlusal splints and other therapies have not met with consistent results.

Several publications now report on the effectiveness of botulinum in reducing the size of the masseter muscle.[9, 10, 11, 7, 12] In higher doses, permanency has been obtained. The earliest studies published from abroad have used Dysport, which is not yet available in the United States. According to a 2009 Cochrane Database review, well-designed, adequately powered, randomized controlled clinical trials are needed to study the effects of BOTOX® injections as treatment for bilateral benign masseter hypertrophy.[13]

Optimal dosage for reducing the size of the masseter muscle is under investigation. Currently, the most common dose in the author's clinic for (BOTOX®) to the masseter muscle is 15-50 IU per side.

Surgical Therapy

Prominent zygoma

The patient is evaluated to locate the area of concern. If only the body is involved, burring the prominent portion through an intraoral incision may suffice. Wide subperiosteal dissection can lead to malar soft tissue ptosis. To prevent this, the soft tissue should be supported by suturing to the periosteum or through a drill hole along the infraorbital rim. If the arch contributes to the problem, as is usually the case, a coronal approach is frequently used. The author currently favors the coronal approach to preclude problems with malar soft tissue ptosis. The coronal approach also affords less risk to the frontal nerve as compared to a limited incision approach to the zygomatic arch.

Prominent mandibular angle

The cause of the bony prominence is determined by evaluation of the patient and radiographs. The lateral flare can be reduced using a sagittal saw or bur through an intraoral incision. The lateral flare can occur in conjunction with a prominent posterior bony angle, which is removed using a Stryker oscillating saw through an intraoral incision. Once the radiographic template of the desired resection has been marked on the bone, make the first cut at the superior (cephalic) border of the template along the posterior border of the ascending ramus. This controlled cut prevents going too high on the ascending ramus, which would risk a subcondylar fracture. After this first cut, the contouring is continued by 3-4 straight-line ostectomies, each cut moving down the mandible toward the symphysis as previously marked, followed by smoothing out of the overlapping cuts.

Frequently, the prominence is not limited to the jaw angle, but involves the entire mandibular body. Alternatively, the angle is difficult to visualize because of the prominence of the body. In such cases, the outer cortex of the mandible is removed, in a manner described as a sagittal split ostectomy.[14]

Preoperative Details

Prominent zygoma

Radiographs are reviewed and asymmetries noted. The relationship of the mandible is also assessed because correction of the zygoma may make the mandibular angle appear more prominent. Counsel the patient appropriately. Examination of the radiograph and the physical examination findings helps determine which components of the zygoma need to be addressed. If prominence is isolated to the body or the anterior portion of the arch, an intraoral approach suffices. If the zygomatic arch is involved, a coronal approach is necessary to adequately address the prominence.

Mandibular angle

A Panorex radiograph helps delineate the course of the inferior alveolar nerve and the amount of bone that can be safely removed. If the mandibular angle is square, a plan can be made to convert it to a more obtuse angle by using a right-angle saw to remove bone from the posterior mandibular border. If the primary problem is width from a frontal view, the lateral cortex of the mandible can be burred.

Intraoperative Details

Prominent zygoma

Full exposure of the arch and body of the zygoma is obtained through a coronal approach. Using a sagittal saw, the first osteotomy is performed at the junction of the body and arch of the zygoma. A second osteotomy is made at the arch, staying anterior to the zygomatic tubercle so that the temporomandibular joint is not violated. The osteotomized segment is repositioned cephalically, usually approximately 2 cm, and secured using wires or miniplates. The arch segments are overlapped, so that the free bone segment lies underneath the fixed segment of the arch. Bone edges at the arch and the body are burred down to prevent a step-off. A drain is placed, and the temporal fascia is sutured. An ellipse of scalp is excised prior to closure with staples, in a vector corresponding to the lateral brow–malar soft tissue junction, to help prevent cheek ptosis. See the image below.

Zygomatic osteotomies are performed at the junctio Zygomatic osteotomies are performed at the junction of the body and arch, just anterior to the zygomatic tubercle. After mobilization, the fragment is in-fractured and/or repositioned cephalically. The mandibular angle is contoured as marked.

Alternatively, a complete transection of the posterior cut followed by a greenstick infracture of the anterior cut can adequately reduce the zygoma without the need for plate or wire fixation. This technique has become the author's preferred technique.

Mandibular contouring

An intraoral incision is made along the anterior edge of the ramus, and a subperiosteal dissection is performed. Sharp dissection using a knife or cautery is used to detach the muscle along the inferior posterior border of the mandible. To improve width, a large bur is used to reduce the protruding bone. Alternatively, a Lindemann spiral bur can be used to score or mark the desired bony excision, and then a chisel can be used to split off the offending bone fragment. A right-angle saw can be used to reduce the posterior border of the mandible to create a more obtuse angle. Of utmost importance is to protect the soft tissue at all times when using power drills or osteotomes in this highly vascular area. Bleeding from the facial artery can be difficult to control. An external incision may be necessary to control vessels that may retract under the mandible. The images below show a patient before and after surgical reduction of the mandibular angle.

Reduction of mandibular angle, AP view image. Reduction of mandibular angle, AP view image.
surgical reduction of the mandibular angle (same p surgical reduction of the mandibular angle (same patient as in media file 6).

If access to the angle is obscured by the body of the mandible or if the patient has a prominent mandibular body, then a sagittal split ostectomy is performed. The outer cortex of the mandible extending from the angle distally to the mental foramen mesially is resected. Bone wax may be needed on occasion. The image below shows the outer cortex of bone that has been removed.

Sagittal split ostectomy bone segment, removing th Sagittal split ostectomy bone segment, removing the outer cortex of the mandible.

Alternatively, a retromandibular approach can be used. An incision is made along the inferior half of the auriculo-mastoid sulcus, ending at the posterior border of the lobule. Subcutaneous dissection is followed by a vertical incision through the superficial musculo-aponeurotic system (SMAS) along the posterior border of the mandible. This is followed by blunt dissection of the posterior border of the parotid gland and retracting it anteriorly. The pterygomasseteric sling is identified and incised along the posterior border of the mandible, extending from the angle of the mandible upward 2 cm. Care is taken to avoid the facial nerve; the retromandibular vein is retracted posteriorly. A subperiosteal dissection covers the area extending from just above the occlusal plane to slightly mesial to the anti-gonial notch.

The dissection continues around the border (knife dissection is required at the angle) and onto the undersurface of the mandible for 2 cm to clear the area for the osteotomy. Under direct vision, the reciprocating saw is used to resect the proposed area of bone. One or several osteotomies are used to create the desired curvature to the angle. The limiting factor on bone resection is the inferior alveolar groove, which is checked by Panorex, taking in to account the 20% magnification at the mandibular angle.[15] The usual dimension of bone resected is 15 mm x 40 mm. A drain is placed (removed 2 d later) and an anatomical closure is afforded, with a watertight SMAS closure to prevent a parotid fistula.

Postoperative Details

Zygoma reduction

Compressive dressings and drains are removed on the first postoperative day. Every other staple is removed on the third day, and the remainder of staples are removed on the seventh day. A soft diet is advanced as tolerated by the patient. Postoperative pain is mild to moderate. Swelling resolves enough for the patient to return to work approximately 10 days after the procedure.

Mandibular contouring

Postoperative trismus is to be expected, and exercises to stretch the masseter muscle should begin after 1 week. Compressive dressings are worn for 1 week. The diet is advanced from a clear diet the first day, to a liquid diet for the first week, and then to a soft diet for another week.

Trismus can be significant if the masseter muscle was partially removed as part of therapy. The patient is instructed in mouth opening exercises for the first 2-3 weeks.

Complications

Malar surgery

The frontal nerve can occasionally be injured during the coronal approach. Traction injuries resolve within 6-12 months. Transection of the nerve requires treatment by denervating the opposite frontal nerve (surgically or with botulinum toxin injection) and/or a hemicoronal lift.

Asymmetry

Preoperative asymmetry should be pointed out to the patient. The advantage of a coronal approach to malar reduction is the maximum control over the bone segment and the opportunity to compare both sides simultaneously. Persistent postoperative asymmetry may necessitate reoperation.

Step-off

A mild degree of step-off can occur. This can be minimized by burring down the contact surfaces of bone.

Mandible

The marginal nerve lies in a plane superficial to the masseter muscle. The nerve is potentially at risk during resection of the masseter muscle or during the use of power instruments without adequate protection.

The facial artery lies at the anterior border of the masseter muscle. The subperiosteal dissection must remain in the proper plane. In addition, when using a power instrument, protection of the soft tissue is critical to the safe execution of the operation.

Subcondylar fracture can result from an unfavorable fracture line extending from the angle of the mandible. A horizontal back-cut along the posterior border at the superior limit can reduce this risk.

Future and Controversies

Malar reduction

The alternative to a coronal approach reposition operation is an intraoral approach to bur down the malar prominence and to create an anterior osteotomy, combined with a preauricular approach to complete the posterior osteotomy. Symmetry may be harder to obtain through this route, and malar soft tissue ptosis may occur.

Mandibular contouring

The masseter muscle may be removed as part of the operation. From a frontal view, the muscle can contribute significantly to mandibular prominence. Some believe that removal of the bone alone changes the dynamics of masseter muscle contraction and leads to thinning of the muscle by disuse atrophy. Others believe that the muscle should be resected to achieve maximal effect.

Botulinum toxin

The use of botulinum toxin to reduce the hypertrophy of the masseter muscle will play an important role in the future.[16] Although the bony prominence remains, the reduction of muscle thickness significantly improves the appearance of the mandibular angle.[17]

The use of botulinum for masseter hypertrophy is quickly becoming the treatment of choice for mild to moderate forms of prominent mandibular angles. Surgery is preferred for more severe situations or for patients who prefer to avoid repeated injections to the masseter.