Fractures of the zygomaticomaxillary complex (ZMC) account for approximately 25% of all facial bone fractures, the second most common after nasal bone fractures, and their surgical treatment has been described extensively [1-3]. In addition, various postoperative complications, including functional (visual impairment, diplopia, malocclusion, and hypoesthesia involving the infraorbital nerve) and esthetic deformities (malar asymmetry, midfacial widening, and enophthalmos) have been introduced for decades by a few studies, and efforts to reduce these have been continued [1-5].

ZMC has a protruded and convex shape. Its projection plays an essential role in determining the contour by affecting the width of the middle face [6-8]. It determines the height, width, and projection of the lateral face and shows racial characteristics. East Asian populations, especially Chinese, Korean, and Japanese, are characterized by high and broad cheekbones. Their overly protruding zygomas and zygomatic arches upset the harmony and make their facial contours appear rough, aggressive, and masculine [6-10]. In this context, ZMC reduction poses a continuing challenge for maxillofacial surgeons because of its significant position in facial esthetics and symmetry, requiring skills and expertise. Numerous studies have demonstrated quantitative and qualitative evaluations of the adequacy of facial symmetry recovery after ZMC fracture reduction surgery [2,11-13]. However, there are few quantitative studies on postoperative symmetry recovery after ZMC reduction in East Asian populations with characteristic zygoma shapes.

In this study, we performed a 3-dimensional analysis of the degree of recovery of malar asymmetry after ZMC reduction surgery in patients with unilateral ZMC fracture compared to patients without any facial bone fracture. The specific aims of our study were to (1) evaluate the adequacy of ZMC fracture reduction through quantitative analysis of postoperative computed tomography (CT) scans and (2) explore detailed directions for outcome improvement.

During the study period, 101 patients with ZMC fractures and 54 non-fracture patients were enrolled. The mean age of the study sample was 43.49 years (range, 17–80 years), and the male-to-female ratio was 66.3:33.7. There were 53 and 48 patients with right and left ZMC fractures, respectively. The mean age of the control sample was 43.35 years (range, 18–79 years), and the male-to-female ratio was 64.8:35.2, which was matched with the study group. In addition, the age distribution was also matched between the two groups (Table 1).

Among the study group patients, six patients (5.94%) received microplate fixation only on the zygomaticomaxillary buttress, six patients (5.94%) received microplate fixation only on the orbital rim, and 89 patients (88.12%) received 2-point fixation by fixing both sites. Before receiving surgical treatment, the I_A and all other variables (D_x, D_y, and D_z) of the study group showed statistically significant differences compared to the control group (p<0.05), suggesting that asymmetry of the ME position was evident in patients with ZMC fracture.

The mean and standard deviations of the bilateral ME position differences in each dimension of the control and study groups after reduction surgery are indicated in Table 2. The results showed that there was malar asymmetry also in the control group in some extent. The mean I_A in control group was 4.10±1.91 mm indicating that the ME position can show a difference normally as much as the corresponding value. The I_A in the study group (4.56±2.26 mm) was not statistically different from that of the control group (p>0.05). In terms of position in each dimension, both D_y and D_z did not differ significantly (p>0.05), but D_x was significantly different between the two groups (p<0.03).

In this study, we evaluated whether cosmetic surgery was appropriately performed by assessing ME symmetry after open reduction of ZMC fractures compared to those of healthy patients without fractures. We hypothesized that ME symmetry would be restored by reduction surgery for ZMC fractures. In addition, we tried to find detailed shortcomings through quantitative analysis of each dimension with a CT scan. We also attempted to find a method to improve the surgical results by this review.

There is no consensus on the ideal reference axis and plane using CT scans in the craniofacial system. Still, Rudderman and Mullen [19] suggested that there should be no translations or rotations of the x, y, and z axes to describe the location of the fracture and the deviation of the bone [13]. Otherwise, due to undetected rotation of the axis, the ZMC displacement may be ignored or inadequately evaluated. In this study, we used three-dimension reconstruction images for positional adjustment with known landmarks (nasion, sella, gnathion and Frankfort horizontal plane) [13]. Three or more landmarks (Anterior border of foramen magnum, superior orbital rims and cephalofacial midsagittal plane) were used to define the relative planes and axes. Results showed the adequacy of ZMC fracture reduction and present detailed suggestion for outcome improvement. After ZMC reduction surgery, the symmetry of the ME position was significantly restored, but there were some bilateral differences. Still, these differences were found to be similar to those found in the control group of patients without fracture. Patients without fracture can also show a different position of ME of about 4.10 mm on average. Patients’ awareness of this fact can reduce their dissatisfaction.

Pau et al. [17] reported that normal subjects showed more malar position asymmetry in the anteroposterior dimension (1.83±1.55 mm) than in mediolateral dimension and in superoinferior dimension through a study of patients admitted to a university hospital in California, USA. However, in our study, which included 54 East Asian (Korean) normal subjects without fracture, the anterior to posterior dimension showed less asymmetry (1.36±1.08 mm) than in other two dimensions. The difference in distance was smaller in D_x than in D_y and D_z, which can be attributed to differences in the shape of cheekbones according to race [6-8].

In the detailed description of malar asymmetry including soft tissue reported by Kim et al. [12], a statistically significant malar depression was observed even after surgery in anteroposterior dimension. Kim et al. [12] reported no significant difference in bilateral position of hard tissue landmarks after open reduction and internal fixation in patients with ZMC fracture, but soft tissue depression was confirmed after surgery. Soft tissue depression around zygoma would be more noticeable if reduction were not accurate and was more noticeable when titanium was used in comparison to biodegradable plates [12]. Considering the results of our study and the occurrence of soft tissue depression after surgery, we carefully suggest an overcorrection surgical technique and follow-up studies about the methods of overcorrection technique are needed.

Comparison of the outcomes of 2-point (at infraorbital margin and zygomaticofrontal buttress region) versus 3-point internal fixation (at frontozygomatic suture, infraorbital margin, and zygomaticomaxillary buttress region) in zygomaticomaxillary reduction remains controversial. We did not perform more than two fixations for reduction surgery. Nasr et al. [20] reported no significant difference between 2-point fixation and 3-point fixation for ME asymmetry, including zygomatic projection and width. In radiological assessment using CT scan 3 months after surgery to evaluate post-reduction displacement, backward displaced zygoma reduction in axial view was significantly better in the 2-point fixation group than in the 3-point fixation group. In addition, the total cost of the plates and screws used was significantly higher with 3-point repair than with 2-point repair. However, several studies have demonstrated that the 3-point rigid fixation of the fractured ZMC provides better stability against masticatory forces and maintains anatomic position with less linear and rotational translation [21,22].

This study had some limitations. It can be pointed out that the study did not include soft tissue, which may be of importance in determining aesthetic facial symmetry and appearance. In addition, the fact that the subjective evaluation and satisfaction of the outcome were not investigated is also a limitation. Gaziri et al. [11] evaluated hard tissue asymmetry in ZMC fracture patients and reported that patients often complained about their soft tissue asymmetry even though the bone fragments were accurately reduced. In postoperative malar asymmetry, the patient’s subjective satisfaction is essential because it is an aesthetic sequela rather than a functional sequela. In this study, we evaluated the adequacy of restoration of the symmetry of hard tissue. We also conducted a study on the restoration of soft tissue symmetry according to the patient’s subjective satisfaction and sought ways to improve the outcome.