Abstract

Background

The midfacial width is dominated by the lateral protruding degree of the zygomatic arch. The best way of narrowing the midface is to reduce the arch height and the arc length for patients with an overly curved lateral protruding zygomatic arch. The existing techniques for reduction malarplasty cannot change the degree of curvature of the zygomatic arch. We provide a new technique for efficient midfacial width reduction by multiple osteotomies at different sites on the zygomatic complex and bone resection at the most protruding middle part of the zygomatic arch. The amount of bone resection can be calculated with a simplified geometrical solution according to the desired reduction rate of the arch height.

Methods

A digitalized CT image was used to estimate the arch height and the length of bone for removal from the zygomatic arch. A specific piece of bone was removed from the most protruding point of each zygomatic arch. Greenstick fractures were made at the anterior and posterior roots of the zygomatic arch. The open arches were rotated inwardly until both ends met.

Result

The arch heights of 1,020 sides of the zygomatic arch were reduced in a range from 3 to 11 mm. All the reduced zygomatic arches were reunited properly and healed solidly. The overall satisfaction rate was high.

Conclusion

This technique reduces the width of the midface by changing the degree of curvature of the zygomatic arch. The simplified geometrical calculation solutions are helpful in assuring the reunion of the zygomatic arch at a pre-designed lower arc height level after a calculated shortening of the arc length.

Keywords

Reduction malarplasty Zygoma Geometric eva luation Multiple osteotomies Zygomatic arch Midfacial width

Introduction

Reduction malarplasty is a popular surgery among the Oriental population because patients want to make their wide midface narrower in order to achieve a slimmer look. There have been some surgical techniques for reduction malarplasty published such as chiseling and shaving down [1鈥�3], L-shaped or boomerang osteotomy [4鈥�9], tripod osteotomy [10, 11], posterior root osteotomy of the zygomatic arch [12鈥�15], and anterior and posterior root osteotomies with zygomatic arch under tuck techniques [16鈥�19]. The chiseling and shaving technique together with the L-shaped or boomerang technique mainly concentrate on reducing the size of the zygomatic bone or the anterior end of the zygomatic complex. The tripod and anterior or/and posterior root osteotomy techniques aimed to reduce the zygomatic arch but in a limited degree because if the arch is pushed inward too much, for instance, more than the thickness of the arch, the bone ends will not meet. Above all no previous technique has tried to do the reduction malarplasty by making the overly curved zygomatic arch straighter with more than two osteotomy sites on the zygomatic complex.

As a matter of fact the lateral protrusion of the middle part of the zygomatic arch is the dominant cause of a wide midface or a lateral bulging cheek bone. So to reduce the width of the mid-face the overly curved zygomatic arch should be straightened, to do so more than two osteotomy sites along the rigid arch are needed. On the other hand, to lessen the arch height of the zygomatic arch, its arc length needs to be shortened because the chord length of the arch has to be kept the same. We introduced a new surgical technique for multiple osteotomy zygomatic arch reduction with a simplified geometric calculations based on the digitalized zygomatic CT image, precisely controlled the amount of bone removal from the zygomatic arch and assured the proper reunion of the arch.

Geometrical Considerations in Zygomatic Arch Reduction

Concept

The zygomatic arch is a curved bone structure, shaped like an arch bridge. Geometrically, to reduce the height of an arch, the length of the arc must be reduced if the span of the arch remains the same. For patients with a wide face, the middle portion of the arch is augmented laterally too much. To make the face narrower, the degree of the lateral protrusion of the zygomatic arch and the arc length of the zygomatic arch should be reduced. Although the zygomatic arch is an irregular structure, there are still some geometric rules that we can follow in calculating how much arc length should be removed for a certain arch-height reduction.

eva luation of the Protruding Degree of the Zygomatic Arch

A digitalized CT image was used to eva luate the protruding degree of the patient鈥檚 zygomatic arch. The following parameters and marks were set up for measuring and calculation. As in Fig. 1, a line drawn from the anterior root (point A) to the posterior root (point B) of the zygomatic arch in the cross-sectional CT image of the zygomatic arch represents the chord of the arch. The most laterally protruding point (MPP) is marked on the arch (point D), and the distance from this point to the chord (from 鈥淒鈥� to 鈥淐鈥�) is the height of the arch (HOA). The anterior root to the most protruding point distance (ARMPPD) and the posterior root to the most protruding point distance (PRMPPD) are from 鈥淎鈥� to 鈥淒鈥� and 鈥淏鈥� to 鈥淒鈥�.

Fig. 1 Marks and parameters used for the geometrical eva luation of the zygomatic arch prominence. Line 鈥淎鈥揃鈥� represents the chord of the zygomatic arch. Line 鈥淐鈥揇鈥� represents the height of the arch (HOA)

To set up the average level of HOA, 1,200 (600 female and 600 male) digitalized CT images of the zygomatic arch were randomly selected from the data bank of two CT centers located in different hospitals. All the candidates were born and lived in the north part of China, aged between 20 and 40 years. The average levels of HOA in this group of study were 6.1 卤 1 mm for females and 5.2 卤 1 mm for males. These average levels of HOA were used as references for patients originated from the north part of China in our practice.

Geometric Equations Regarding Zygomatic Arch Reduction

Data of patient鈥檚 zygomatic arch CT image with measuring tool software were obtained before surgery. The HOA was measured for each side of the zygomatic arch to eva luate the degree of lateral protrusion. For a patient wanted to lessen his or her HOA to a desired level the corresponding arc length shortening of the zygomatic arch was calculated as follow.

LDSZAAD+BD-A鈥橠鈥�- B鈥橠鈥�

Fig. 2 Illustrated calculation of the arc length of removal from the zygomatic arch with the Pythagorean theorem. The cross-sectional CT image shows an overly curved zygomatic arch (Left). The simulation image of the zygomatic arch reduction for the left image indicates the shortening of the arch height and arc length of the zygomatic arch (Right). HOA鈥� is the desired arch height

Patients and Methods

Patient Information

In the period from 1995 to 2013, a total of 520 patients underwent zygomatic arch reduction using this method. Altogether 1,020 sides of the zygomatic arches have been surgically treated as 20 patients did only unilateral reduction. All the patients were from the north part of China. The age span of the patients was from 18 to 50. The average age was 28 years old and male to female ratio was 125 cases to 395 cases. Ninety-eight patients had previous reduction malarplasty surgery with various techniques such as filing down, anterior or posterior end osteotomy. Indications were HOA >7 mm, healthy, no abnormality of the zygomatic bone and zygomatic arch.

Surgical Incisions

The intraoral incision was used for every patient to expose the zygomatic bone and the front part of the zygomatic arch. An approximately 3.5-cm-long mucosal incision was made 0.5 cm apart from the upper buccal sulcus between the canine tooth and the second molar tooth. Muscle and soft tissues were blunt dissected until the periosteum of the zygomatic bone was shown. Then the periosteum of the zygomatic bone was incised and elevated to expose the bony surface of the zygomatic bone.

The temporal incision was used to expose the rest of the zygomatic arch for most of the patients. If the patient wanted a forehead lift at the same time and there was indication for a lift, then a coronal incision as described by Baek [15] was selected. To avoid frontal nerve injury, the undermining level at the temporal region was between the superficial and deep temporal fascia as stated by Yang [20] and also over retraction should be avoided when using a retractor to expose the zygomatic arch. When the upper edge of the middle portion of the zygomatic arch was exposed, a small part of the periosteum on the lateral side of the arch was elevated to clear off the soft tissue for ostectomy.

Reduction of the Zygomatic Arch

After exposure of the zygomatic arch, a compass was used to mark the most protruding point on the lateral surface of the bony arch based on the CT measurement of PRMPPD. This point was set as the center and the length of desired shortening of the zygomatic arch (LDSZA) as the diameter of a bone fragment of the zygomatic arch was marked to be cut off (Fig. 3).

Fig. 3 The ostectomy and osteotomy sites at the zygomatic arch. 鈥淎鈥� and 鈥淏鈥� mark the greenstick fracture sites at the anterior and posterior roots. 鈥淐鈥� and 鈥淒鈥� mark the bone resection line

A reciprocating saw with a mini blade was employed to cut through the zygomatic arch bone at the marked lines 鈥淐鈥� and 鈥淒鈥�. The bone segment was removed to open the zygomatic arch. Then the lateral cortexes were sawed at the anterior and posterior roots (lines 鈥淎鈥� and 鈥淏鈥�). A gentle inward pushing force was applied on the free ends (鈥淐鈥� and 鈥淒鈥�) of the open arches letting greenstick fracture occur at the roots (鈥淎鈥� and 鈥淏鈥�) and the free ends (鈥淐鈥� and 鈥淒鈥�) meet. The zygomatic arch became a solid and fixed structure again. Mini plates and screws or wires were occasionally used to fix the junction line of the free ends only if the re-bridged zygomatic arch was not stable (Figs. 4, 5).

 Fig. 4 Multiple osteotomy zygomatic arch reduction with temporal incision. The osteotomy sites are marked as 鈥淎, B, C, and D鈥�

Fig. 5 After the removal of a bone fragment between 鈥淐鈥� and 鈥淒,鈥� the zygomatic arch is reduced and reunited

Result

Among the 1,020 sides of zygomatic arch reductions, 880 sides were done through intraoral plus temporal incisions, the other 140 sides through intraoral plus coronal incisions. The arch heights of the zygomatic arch were reduced by 3鈥�11 mm, average 5.85 mm. The pre- and post-surgery HOA values are listed in Table 1. Though the HOAs of the right and the left side were different for each patient, there was no statistical significance between the HOAs of the right and the left side in the overall data.

Table 1

Pre- and post-surgery CT eva luation of HOA (in mm) for patients in different age groups

Age	Female		Male
	Pre	Post	Pre	Post
18鈥�28	11.75 卤 1.81	5.88 卤 0.97	11.01 卤 1.22	5.15 卤 1.55
29鈥�38	11.67 卤 2.02	5.82 卤 1.06	11.06 卤 1.24	5.24 卤 1.48
39鈥�50	12.48 卤 1.97	6.64 卤 1.02	11.04 卤 2.42	5.21 卤 2.35

The follow-up period ranged from 3 to 30 months, average 12.5 months. All the reduced zygomatic arches were stable constructively, and all patient faces were narrowed as desired without any bouncing back. Post-surgery CT scans were taken in the period of 6鈥�12 months after surgery for 119 sides. All the zygomatic arches in these images looked natural and their arch heights were lessened ideally (Fig. 6).

Fig. 6  Cross-sectional CT image at the level of the zygomatic arch shows the changes after multiple osteotomy zygomatic arch reduction malarplasty. Before surgery image (Left).One year after surgery image for the same patient (Right)

Questionnaires containing 10 questions were used to value the satisfaction rate. These questions included satisfaction with the anterolateral malar prominence reduction, satisfaction with the lateral malar prominence reduction, vision and eye movement disturbance, incision scar, mouth opening interference, post-surgery discomfort, local numbness, upper lip movement dysfunction, pressure-induced discomfort on surgical sites, and workday loss. Patients were asked to mark each question on a scale from 0 to 10 corresponding from the least favorable to the most favorable. If the overall marks of a questionnaire was 70 or more, then this patient was considered to be satisfied with the surgery. The satisfaction rate for this group of patients was 80 %. The most common complaint was asymmetry of the midface. Almost 10 % of the patients complained of slight asymmetry, even in the after surgery photos their faces looked more symmetric than before surgery. This might due to the patient鈥檚 increased sensitivity about their appearances after cosmetic surgery or their expectations of surgery might be too high than what is practical. The common complications for this group of patient are listed in Table 2.

Table 2

Complications and their resolving time after surgery

Signs and symptoms	Less than 3 m鈥�	3鈥�6 m鈥�	More than 6 m鈥�	Total	Incidence (%)
Infraorbital numbness	22			22	2.2
Upper lip dysfunction	6	10		16	1.6
Frontalis paralysis	10	41	5	56	5.5
Hematoma	20			20	2.0
Delayed incision healing	12			12	1.2
Total	70	51	5	126	12.4

Long- and short-term frontalis paralysis was considered to be caused by injuries to the temporal branch of the facial nerve. It might due to over stretching of the nerve from forced retraction, similar to the other nerve injury-related complications in this group. No infection was observed. Delayed incision healing happened in patients with prolonged (over 3 days) indwelling drainage tubes. Compared to Wang鈥檚 [9] overall (early and late) complication rate of 15.7 %, this group is only slightly less. In this group, there were more complications caused by the local nerve disturbance. In Wang鈥檚 study, there was more cheek drooping and bone nonunion.

 

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