Rui LEI,Wenjun WANG,Xi CHEN,Rizwan ALI,Mingyuan XU,Yuming WANG,Jinghong XU

Department of Plastic Surgery,The First Affiliated Hospital,Zhejiang University School of Medicine,Hangzhou 310003,Zhejiang Province,China

ABSTRACT Background Asian women usually view the oval face,with a beautiful curve and clear outline,as elegant.The fat and bloated mid-lower face,with an undefined outline,takes away from what they perceive to be a beautiful appearance.Not only a bone but also soft tissue determine the shape of the mid-lower face.In this article,we introduce a modified surgical method of soft tissue for mid-lower facial recontouring,which can improve the fat and undefined outline of the mid-lower face caused by benign masseter muscle hypertrophy and reduce subcutaneous fat accumulation at the same time.The operative technique is simple and effective with few complications.Methods The surgical treatment of 36 patients who met the adaptation criteria was carried out by laser-assisted liposuction combined with masseter muscle dissection.All patients were followed up postoperatively,and the surgical efficacy was evaluated on the basis of:the comparison of facial contours of patients before and after surgery,the change of masseter muscle thickness detected by B-ultrasound imaging,the satisfaction of patients with postoperative facial contour improvement,and the incidence of complications.Results Between March 1,2018,and August 31,2019,36 patients with indications underwent this procedure.The follow-up lasted 6 to 12 months postoperatively and demonstrated that all patients were satisfied with the postoperative results,of which 33 cases (91.7%) were very satisfied,and 3 cases (8.3%) were satisfied with the treatment and had obvious improvement of the appearance of their mid-lower face.Preoperatively,the average mandibular bigonial breadth was 138.6±8.3 mm,and the average thickness of the masseter muscle was 13.9±0.8 mm; the postoperative breadth was 123.3±7.7 mm,and the thickness was 10.1±0.2 mm.The average reduction of the lower face width and masseter thickness were 15.2±2.1 mm and 3.8±0.1 mm,respectively.No complications occurred among the 36 patients.Conclusion The described method makes a great improvement in reshaping the outline of the mid-lower face,improves the fat and unclear outline of the mid-lower face caused by masseter muscle hypertrophy,and reduces subcutaneous fat accumulation.The procedure is easy to perform and is minimally traumatic,allowing for a quick recovery with few complications.These advantages along with the patients' overall satisfaction with the results make it worthy of clinical application.

KEY WORDS

INTRODUCTION

Asian women usually take the oval face with a beautiful curve and clear outline as a beauty[1].The fat and bloated mid-lower face with an unclear outline show a coarse and masculine look instead of a delicate appearance.According to the three major anatomical components that contribute to the mid-lower facial contour:bone,muscle,and fat,the traditional recontouring methods mainly involve mandibular angle osteotomy,partial masseter resection,partial buccal fat pad resection,facial liposuction,and so on.All of these methods can improve facial contour to varying degrees.However,problems like serious surgical trauma and other complications,a long recovery period,and poor clinical outcomes still exist[2-4].With improved living standards and advancements in plastic surgery techniques and technology,the number of beauty seekers who want to modify the outline of their face is increasing,and the recontouring of the mid-lower face has become a main focus.Optimal surgical effect,decreased risk of trauma,shorter recovery time,and fewer complications also influence patients' choice of treatment,but the existing facial recontouring methods cannot meet these requirements at the same time.

Both bone and soft tissue determine the mid-lower facial contour.With increasing age,fat accumulation is more readily found in the buccal,marginal mandibular,and mandibular regions,and masseter hypertrophy occurs,which also significantly affects the appearance of the midlower face.Although,traditional facial liposuction can improve the facial outline and is more easily accepted by patients,it results in massive surgical trauma,less liposuction amount,lower precision,and cannot resolve the bloated lower facial outline caused by masseter factors.Consequently,it has limited clinical benefit in this context.Based on these factors,we introduce a modified surgical method of the soft tissue for mid-lower facial recontouring,which can improve the fat and unclear outline of the mid-lower face caused by benign masseter muscle hypertrophy and reduce the subcutaneous fat accumulation to avoid the shortcomings of the above method.In this article,we describe the detailed design and main features of the new procedure and explain how to avert complications.

MATERIALS AND METHODS

Patients

Thirty-six female patients (age range=19-38 years,average 26.5±5.6 years,generally less than 50 years)underwent surgery in our department between March 1,2018,and August 31,2019.All of the patients met the following surgical conditions:

· The patient had a strong desire to alter her mid-low facial lines.

· Inclusion criteria:

(1) Patients knew the content and purpose of the surgery and signed the informed consent form;

(2) Patients had an accumulation of subcutaneous fat and masseter muscle hypertrophy that they wanted to improve by surgical methods;

(3) There was no occupying lesion of the masseter muscle or tumor;

(4) There was no obvious abnormality in the relevant preoperative examination;

(5) There was no mental illness.

· Exclusion criteria:

(1) Pregnant and lactating women;

(2) Elderly patients with mid-lower skin laxity;

(3) Patients with severe organ diseases and intolerance to surgery;

(4) Those whose outcome expectations were too high or unrealistic;

(5) Those with obvious hypertrophy and valgus of the mandibular angle.

OPERATIVE PROCEDURE

Preoperative management

First,preoperative B-ultrasound examination of the masseter muscle and measurement of its thickness,followed by ultrasound measurement of the thickness of the fat layer in buccal,mandibular,and submental regions.Next,anterior,lateral,and oblique images of the face were taken with the patients sitting in an upright position.Then,the face was marked at the buccal,marginal mandibular,and mandibular regions for laserassisted liposuction and masseter dissection,especially the areas of obvious fat accumulation.Finally,design of the incision at the auriculocephalic sulcus behind the earlobe was made.The main surgical instruments and materials are shown in (Figure 1):1 semiconductor laser emitter,1 needle for injection,1 tripod 3-hole liposuction needle,4 screw injectors,1 detacher,and 1 suitable elastic mandibular mask.

Surgical anesthesia

All patients were anesthetized by local tumescent anesthesia.The tumescent solution contains 20 ml of 2%lidocaine,0.5 mg of 0.5% epinephrine hydrochloride,and 5 ml of 5% sodium bicarbonate with 500 ml of normal 0.9% saline.

Surgical procedure (Figure 2)

Preoperative design (figure 2-A) is illustrated in figure 2-A showing the treatment area including the marginal mandibular,buccal,mandibular,and submental regions,and marked the masseter muscle preoperatively.The treated area was under tumescent anesthesia,with 150-200 ml of tumescent solution injected into each side,prepared with a disinfection and sterile technique.After giving 5-10ml tumescent solution to the deep periosteum of the masseter (figure 2-BC),the tissue was separated subcutaneously and obliquely for 1 cm,and then the masseter dissection tunnel (figure 2-D) was made to penetrate the masseter vertically,straight to the periosteal surface -all through the 5-mm incision at auriculocephalic sulcus.Then,the masseter was dissected along the periosteal surface,the areas among the surrounding of the tunnel,the mandible ramus,the mandibular angle,and the inferior attachment of the masseter (figure 2-E).After that,using the optical fiber in direct contact with the subcutaneous fat through the fiber tunnel,with energy setting at 20 Hz,8-10 W,laser energy was delivered through the probe from distal to proximal at 2-3 cm/s in a fan-shaped pattern to achieve superficial lipolysis.Heated while tightening the fascia layer,the temperature was monitored by the operator's hand.The distance between lipolysis points in each tunnel was about 0.5 cm,where the laser was applied for less than 1s,and each tunnel treated repeatedly three times (figure 2-F).Then,after inserting the blunt head tripod 3-hole liposuction needle(diameter of 2-3 mm) connected to the 20 ml screw syringe,negative pressure was applied in a fan-shape to suction subcutaneous fat,liposoluble particles,and tissue decomposition.The liposuction plane was in the superficial subcutaneous fascia layer of the skin,while the opening of the cannula was toward the deep fatty layer during the operation to avoid localized depression(figure 2-G).According to the subcutaneous fat thickness of different patients,the finger should be pinched at least 5-mm from the thickness of the subcutaneous fat,and generally,15-30 ml fat should be aspirated from each side.Excessive suction should be avoided to prevent nerve injury because the superficial area of the perioral facial nerve is relatively easy to expose.Aspirated fat from each side was collected to ensure that bilateral volumes were equal (Figure 2-H).After the liposuction,the residual tumescent solution was expressed out,then an elastic mandibular wrap was applied after suture placement (6-0 nylon suture) (Figure 2-I),which was worn a week after suture removal.

MEASURES

All patients were followed up after 6 months to 1 year using a questionnaire that was sent to these patients.Postoperative patient satisfaction was assessed by a questionnaire designed by Choi[5]et al.This questionnaire contained 22 questions (Supplemental Digital Content 1 presents the Patient Satisfaction Questionnaire).Five questions solicited the patient's satisfaction with the esthetic outcome,twelve were related to complications,three concerned psychosocial benefits,and two were related to general outcomes after facial bone contouring surgery.Patients were asked to select only one out of the given answer options,but space was provided for the patients to record additional comments if warranted.The thickness of masseter pre-and postoperatively was measured by B-ultrasound.The operation time for each patient was recorded.Complications and corresponding treatment measures were also documented.

RESULTS

Between March 1,2018,and August 31,2019,36 patients with indications had undergone laser-assisted liposuction combined with dissection of the masseter muscle.

The surgical effect revealed that the mid-low facial outline was reshaped and significantly improved.Local subcutaneous fat accumulation and unclear outline of the mid-lower face caused by masseter muscle hypertrophy was reduced,and the skin of the surgical area was smooth and tight.The recontouring of the mandible and cervicomandibular angles,and the positive aesthetic effect were obvious.The outline of the mid-lower face is ovalshaped,with a smooth curve,bilateral symmetry,and is pleasing to the touch (Figure 3-7).All the patients were very satisfied with postoperative outcomes,of which 33 patients (91.7%) were extremely satisfied,and three patients (8.3%) were satisfied with the treatment (Table 1).Preoperatively,the average bigonial breadth was 138.6±8.3 mm,and the average thickness of the masseter muscle was 13.9±0.8 mm.The postoperative breadth was 123.3±7.7 mm (Table 2) with a thickness of 10.1±0.2 mm.The average reduction of lower face width and masseter thickness were 15.2±2.1 mm and 3.8±0.1 mm,respectively (Figure 8).

Among the 36 patients,none had any serious complications such as hematoma,infection,local induration or depression,skin necrosis,pigmentation change,or facial nerve injury.Any local swelling generally subsided about seven days after the operation.One patient (2.8%) suffered from subcutaneous ecchymosis,and 2 patients (5.6%) suffered from slight numbness in the treated area,which resolved within 30 days.30 patients had little change in the masticatory function,while in six patients,it was decreased significantly.At the 6 to 12 month follow up,no complications were observed.The average operative time was 35 minutes (range=30-65 minutes).

DISCUSSION

Asian women usually take the oval face with beautiful curve and clear outline as beauty[1].The fat and bloated mid-lower face,with unclear outline,shows a coarse and masculine look instead of the delicate and dainty appearance.According to the three features that contributeto the shape of the mid-lower facial contour:bone(prominent mandibular angle),muscle (masseter muscle hypertrophy),and fat (subcutaneous fat accumulation),the recontouring methods are numerous and can improve the facial contour to varying degrees.

Table 1 Patients' satisfaction with postoperative results at 6-12 months follow-up and distribution of answers regarding an esthetic outcome

Various types of mandible osteotomy have been used for the prominent contour of the mid-lower face caused by bone structure[2].Although the surgical effect is remarkable,it is a complex surgical procedure with a long recovery time and a high risk for complications to include hemorrhage,bilateral asymmetry,facial nerve injury,and others that are not easily accepted by patients[6,7].

Partial buccal fat pad resection can be implemented to improve the “baby face” appearance[8].Generally,this is performed with multiple intraoral incisions,but the surgical field is narrow,which can lead to cheek depression as well as limited selections[9].

Table 2 Pre-and postoperative soft tissue mandibular angle distance and thickness of the masseter muscle

region often leads to a bloated look in the mid-lower face.Traditional facial liposuction is a method aimed at this,which is more easily accepted by patients and now has been widely used[10].However,as discussed above,it is not a risk free procedure and has been associated with adverse outcomes.

The masseter muscle plays an important role in facial aesthetics.Prominent masseter muscles can be considered cosmetically disfiguring,especially in patients without significant overgrowth or eversion of the mandibular angle.Treatment options for masseter muscle hypertrophy range from invasive surgical reduction like resection to simple pharmacotherapy,like injection with botulinum toxin,type A (BTX-A).The traditional method for treating masseter muscle hypertrophy is the surgical partial excision of the masseter muscle under general anesthesia[3],or combined with an osteotomy.

The surgical method of partial excision reduces the bloating of the lower face but comes with the consequences of a long recovery period,high surgical risk,and potential complications[13]including hematoma formation,facial nerve paralysis,infection,and limited ability to open the mouth.Injection of BTX-A into the masseter muscle was first introduced by Moore and Smyth in 1994[14,15]to treat for benign masseter hypertrophy.BTX-A blocks neurotransmitter transmission by acting on the neuromuscular junction,which leads to muscle atrophy.It takes 4-12 weeks for the masseter to achieve maximum atrophy,after that,a new neuromuscular junction would form,and the thickness of the masseter muscle would recover after 24 weeks.This method is relatively safe,convenient,and less invasive; however,the effect is slow and only lasts for 4-6 months[16].Complications like dizziness,headache,decreased masticatory function,less effect,resistance to treatment,facial drooping,facial expression changes,buccal depression,and others still exist,although,with rare incidence[17-20].More common cons associated with this treatment,like repeated injection,high cost,antibody production,and fat accumulation are still there[21].

The mid-lower face is one of the most important aesthetic features to directly influence one's appearance.Fat accumulation in the buccal region,marginal mandibular,and mandibular regions (double chin) lead to a bloated face especially when the masseter muscle is hypertrophied,which is contrary to the aesthetic pursuit of the V-shape face:therefore,more and more patients ask to treat this.

Compared to the other methods discussed,combined laser-assisted liposuction with the dissection of the masseter muscle makes a great improvement in reshaping the outline of the mid-low face by improving the unclear outline of the mid-lower face caused by benign masseter muscle hypertrophy and reducing the accumulation of subcutaneous fat in this area.The procedure is easy to perform,with a quick recovery,lower trauma,and fewer complications.This operation has been improved in the following three aspects:1.It is minimally invasive,with the dissection of the masseter muscle through a small incision in the auriculocephalic sulcus behind the earlobe instead of resecting the masseter muscle; 2.The laserassisted liposuction of the lower-face is less traumatic,more efficient,and better for skin tightening; 3.A tripod 3-hole liposuction needle is used to further improve efficiency.

The operation has the following advantages:

1.Laser-assisted liposuction not only deals with extra subcutaneous fat but also improves the liposuction volume and efficiency,which is suitable for the precision of local contour and has a better effect than traditional facial liposuction.Laser lipolysis follows the principle of plasma photo thermolysis.Under the adipocyte cell liquefaction caused by the energy,the liquefied fat is naturally metabolized by the human body or suctioned through liposuction needle.The high-energy plasma laser is delivered by fiber optics causing adipocyte cell membrane rupture to make fat suction easy,which improves the liposuction volume and efficiency and reduces localized trauma.This procedure can remove fat from both superficial and deep layers.Combined lipolysis in deep layers with carving in the superficial layers can break fibrous bands in hypodermis and fat in cases of localized unevenness[30].Lipolysis also reduces fat accumulation and tightens the skin,which has had great clinical application in recent years[31].Studies support that the heat generated in the process can stimulate the contraction and proliferation of collagen in the dermis,contract and improve the skin,and play a role in the tightening of skin[23].Leclere[24]applied laserassisted liposuction to the abdomen with satisfactory results.There was obvious new collagen formation in the treated area,which provided a theoretical basis for the application of skin tightening.Therefore,compared with traditional liposuction,laser-assisted liposuction has a is greatly advantageous[25].

2.Masseter muscle dissection can be performed with laser-assisted liposuction through the same small incision in the auriculocephalic sulcus behind the earlobe.The operation is simple and improves the contour associated with masseter hypertrophy.After nearly 6-12 months of follow-up,we found that masseter muscle dissection can effectively improve the facial contour of masseter hypertrophy,and lead to masseter muscle atrophy.The main reasons for the changes are as follows:(1) secondary atrophy from weakened biomechanical strength of the masseter attachment interface,decreased muscle tension,and reduced activity in the early postoperative period[32];(2) blood supply of the masseter muscle may be reduced after dissection,coupled with some microvascular damage,which will also promote the masseter muscle atrophy[26]; (3) the masseter nerve stem and divisions will inevitably be injured during the dissection,which may cause denervated atrophy[33,34].Some animal models show that when the masseter muscle is dissected from the bone,its volume decreases because of atrophy[35].In our study,it was confirmed in 36 patients that obvious atrophy of the masseter muscle occurred a month after the operation(the preoperative average thickness was 13.9±0.8 mm and was 10.1±0.2 mm a month after the operation,the average reduction was 3.8±0.1 mm).The atrophy began to resolve at 6 months after the operation,and the muscle was observed to be smaller one year after the operation compared to right after the treatment.The masticatory function of the masseter muscle had no obvious reduction in 30 patients,while it did in 6 patients.In our follow-ups,there was no unsightly local bulge observed after treatment caused by the contraction of masseter muscle dissection.The reasons are considered as (1) the masseter muscle was not completely dissected,but only separated with the attachment of posterior region of the mandibular ramus,posterior region of the mandibular angle and the inferior region of the mandible,and also part of the masseter at mandible; (2) the 7-day minimum elastic compression wrap prevents postoperative hemorrhage,provides muscle compressive fixation and is important to recontouring and postoperative recovery;(3) it has also been mentioned that masseter muscle atrophy occurred in the case of reattachment,blood loss,and nerve damage,so the atrophic masseter muscle was mostly flat instead.

3.This method makes a great improvement in reshaping the outline of the mid-low face,improves the fat and unclear outline of the mid-lower face caused by masseter hypertrophy,and reduces the accumulation of subcutaneous fat.It is easy to perform,with a quick recovery,lower trauma and fewer complications.All 36 patients had no serious complications; only a few patients had slight localized swelling,subcutaneous congestion,and mild numbness in the surgical area,which could recover spontaneously.Because of the lipolysis and coagulation produced by a laser,laserassisted lower liposuction has the advantages of less intraoperative pain,less hemorrhage,faster recovery,and less postoperative congestion and edema compared with traditional liposuction[27,28].Fat was liquefied through lipolysis,which makes the liposuction more effective and improves overall fat loss[29].In the operation,we used the tripod 3-hole liposuction needle instead of the single-hole one to further improve the liposuction efficiency.It is worth noting that the following points should be paid attention to during the actual procedure of laserassisted liposuction combined with masseter muscle dissection:(1) the indications should be strictly followed.This treatment is more suitable for local fat accumulation and masseter hypertrophy; while it is difficult to achieve a better improvement for the patients with severe cutis laxation,preoperative attention should be paid to the evaluation of the subcutaneous fat thickness and skin laxation of the patients.-Generally,the ideal age is less than 50 years; (2) optical fiber contact to the subcutaneous fat through the probe should be performed distally to superficially through the tunnels in a fan-shape,and the distance between lipolysis points in each tunnel is about 0.5 cm; (3) attention should be paid to temperature control,particularly the epidermal temperature near the optical fiber -do not stay at the same place too long to prevent burning the tissue.Our experience is that the optical fiber should always be in motion,moving at a speed of 2-3 cm/s,and repeated three times each place(an infrared temperature gun could be employed to keep the epidermal temperature below 42℃ to prevent burning.Within this safe temperature,the local increasing temperature produces the contraction of fibers in the subcutaneous fat layer and collagen in the skin,thus achieving the skin tightening; (4) lipolysis depth should not be too superficial; liposuction at the subcutaneous fat layer can prevent the skin damage; the depth of optical fibers 1 cm below the skin is relatively safe.If above that,it may damage the subdermal vascular rete and affect the integument's blood supply,causing irreversible damage;(5) operating power should be controlled at 8-10 W to the mid-lower face to achieve precise control and to reduce unnecessary damage; massage muscle dissection should be effectively performed on the periosteum.The tissue is separated subcutaneously and obliquely for 1 cm,and then the masseter dissection tunnel is made to penetrate the masseter vertically,straight to the periosteal surface all through the 5-mm mini-incision at auriculocephalic sulcus to avoid nerve injury[2].The masseter muscle was dissected along the periosteal surface after the detacher entering into the tunnel,areas include the surrounding of the tunnel,the mandible ramus,the mandibular angle,and the lower attachment of the masseter.The 7-day minimum elastic compression prevents postoperative hemorrhage,provides muscle compressive fixation,and is important to recontouring and postoperative recovery.Precision and bilateral symmetry are strictly required.Fat loss of each side was collected for comparison to ensure that bilateral volume was the same; and,before the end of the operation,the thickness of the subcutaneous fat should be evaluated by pinching the surgical skin for outline and bilateral symmetry,some irregularities should be repaired appropriately.

CONCLUSION

After summarizing the traditional methods of facial recontouring,this paper discusses an innovative and effective modified method of soft tissue contouring in the mid-lower face (laser-assisted liposuction combined with masseter dissection).The method employs masseter dissection and laser-assisted liposuction instead of partial masseter resection and traditional liposuction.The combination of the two improves the unclear outline of the mid-lower face caused by masseter hypertrophy and the accumulation of subcutaneous fat at the same time,therefore,enhancing facial contour.Most of the patients were very satisfied with their surgical results.With the advantages of convenience,quick recovery,less trauma,and fewer complications,it is worthy of more clinical application.