A blowout fracture only involves the walls of the orbit, and occurs in the most fragile part of the orbital wall. Blowout fractures can be associated with intracranial, optic nerve, lacrimal system, eyelid, and globe injuries [1,2]. Patients usually sustain facial fractures from a blunt impact to the orbit and are diagnosed with accompanying ocular symptoms. Such ocular symptoms are inspected and examined by careful physical examinations and computed tomography (CT) scans. Surgical intervention is recommended usually within 2 weeks, to replace the fractured bone segments and correct soft tissue distortion. Even after surgical repair, patients may suffer from permanent complications such as persistent diplopia, visual loss, dystopia, enophthalmos, scarring, and sensory disturbances [2].

Many studies have looked into the frequency of persistent ocular symptoms. The majority of patients admitted to the emergency department are those who have sustained an assault, but there is no study on assault patients and related ocular symptoms. In practice, it is difficult to explain to the patients the outcomes and expectation of surgery. Therefore, we evaluated the incidence of residual ocular symptoms in blowout fractures between assaulted and non-assaulted patients, and sought to identify any connection among the degree of enophthalmos, defect size, and assault-related injury.

A retrospective review was performed for any patient who sustained a unilateral blowout fracture between January 2010 to December 2014. Patients were included in the study for having received operative intervention with at least 6 months of follow up. The collected data included information such as age, gender, etiology, and clinical ocular symptoms as examined by an ophthalmologist. Statistical relationship were analyzed among ocular symptoms and injury location, fracture dimension, degree of enophthalmos, etiology, and days to surgery. Ocular symptoms were categorized again into preoperative (acute) symptoms and post-operative (late) complications. Complications were defined as secondary ocular symptoms, which persisted or newly appeared within the 6 months of follow up. All of the patients had been evaluated by both a plastic surgeon and an ophthalmologist in the emergency department. Diagnoses were made using facial 3D CT and clinical examinations. Only pure blowout fracture patients were included, and old fractures or zygomaticomaxillary fractures were excluded. As per the inclusion criteria, all of the patients in the study had undergone corrective surgery under general anesthesia. The blowout fracture was fixed via subciliary, transconjunctival, or transcaruncular approach. Absorbable mesh plates were used to reconstruct the orbital floor and wall, and any herniation of periocular tissue was repositioned prior to placement of the absorbable plate on the orbital floor. All of the patients were followed up for at least 6 months at both the plastic surgery and ophthalmology outpatient clinics. Follow-up visits were made at 2 weeks, 1 month, 3 months, 6 months, and 1 year. Any symptoms either complained by the patient or assessed by a physician were recorded on the medical chart and studied retrospectively.

Patients were divided into subgroup 1 and 2, according the etiology of the injury, assault or non-assault. The definition of ocular signs and symptoms were based on previous publications [3]. The CT examinations had been performed for all patients using the imaging parameters (Toshiba Aquilion One, Tokyo, Japan): 120 kV, 150 mAs, FOV 25 cm, and 3-mm section thickness. Diplopia was measured using the Lees screen test, where the patient fixes one eye at 9 points in an inner square and 17 points in an outer square, and diplopia is measured at a screen placed at a right angle [4]. The amount of motility restriction was measured in vertical, horizontal, and diagonal directions. CT images were used to assess the degree of enophthalmos. To calculate the degree of enophthalmos, we measured the distance from the corneal center to the shortest segment from the lateral orbital rim to the medial orbital margin (Fig. 1). An eye with a difference of more than 2 mm compared to the normal eye on the axial CT image were considered to have enophthalmos.

In this study, we also measured the defect size of the blowout fracture, by measuring the bony defect in the coronal view of the CT scan (Fig. 2). The thickness of the CT sections was 3 mm, and the bony defect length was set as C. Then, we used the sum of the product between C and 3 mm for each slice, ∑n=1NCn*3, to obtain the defect size.

The independent χ²-test and Fisher's exact test were used to compare the difference between the two groups. Linear regression analysis was used to find the relationship between bony defect size and düegree of enophthalmos. Statistical analysis was performed using PASW ver. 18.0 (SPSS Inc., Chicago, IL, USA).

Blowout fractures are one of the most common facial bone fractures and can cause serious ocular complications in patients. Surgeons replace the brittle fractured segments with absorbable biodegradable mesh plates or other implants to minimize complications and restore function to prevent or solve ocular problems, but the reconstruction can also create problems for the patients [5]. Hence, there is no universal guideline regarding the treatment, optimal timing of surgery, or management of surgical outcomes [6]. We felt that it would be meaningful to retrospectively analyze the cause of injury and statistically analyze it to find any correlation. Furthermore, we sought to assess blowout fracture patients presenting with symptoms to find out if there is a meaningful difference between assault patients and patients of a different traumatic etiology.

In previous studies, many authors reported varying degrees of postoperative sequelae. According to Folkestad and Westin [7], postoperative permanent sequelae were found in 83% of the patients. The most common sequelae were sensibility disturbances (55%), vision symptoms (48%), and cosmetic problems (44%). Permanent diplopia was noted in 17% of the patients who underwent surgery. Other authors such as Neovius et al. [8] report that persistent diplopia was present in 3.7% of fractures involving the orbit. In other studies where all fractures involving the orbit were included, permanent diplopia was reported to be 6% to 15% [3,5]. The mean age of the patients in our study was 36.1, which is comparable to that reported in the literature [3,4,5,9]. The patient group is relatively young, and permanent diplopia can be a substantial problem for such patients.

Previous studies have reported delayed repair, volume of fracture, extraocular muscle swelling, fracture site, and patient age as potential risk factors for persistent diplopia after surgery [10,11]. According to Tahiri et al. [9], however, the most important independent and statistically significant predictor of postoperative diplopia is the presence of preoperative diplopia. In our study, assaulted patients experienced preoperative diplopia more frequently than did non-assaulted patients (p<0.5), but postoperatively, there was no statistically significant difference between the groups. Many authors have suggested this observation to be due to EOM swelling since the injury, and preoperative swelling of the EOM on the CT scan has shown to be a significant risk factor [12]. We agree with Jin and preoperative swelling of the EOM should not be dismissed upon initial CT examination.

In our study, preoperative enophthalmos was significantly different between the two groups. Enophthalmos was more pronounced in the assaulted group, with 19 patients having preoperative enophthalmos and diplopia simultaneously. According to Converse and Smith [13], the key mechanism of orbital fracture is increased intraorbital hydraulic pressure. In a blunt force trauma due to a fist blow, the force transcends into the orbit and causes a blowout fracture. A fist blow is considered a low-velocity injury [9], and Fujino et al. [14] have previously demonstrated that the hydraulic mechanism requires 10 times as much force to produce a blowout fracture than by the buckling mechanism. Therefore, the low-velocity fist blow is likely to have caused a transcending force throughout the orbit and created enophthalmos. It seems plausible that these two symptoms are associated with one another in fist blow injuries.

According to Putterman et al. [15], adult patients with isolated blowout fractures will eventually recover from ocular motility limitations over time; however, surgical intervention is necessary for severe blowout fractures with soft tissue entrapment on CT scan [16]. All of the patients included in this study had preoperative CT scans prior to surgery, and soft tissue herniation were observed in all patients to varying degrees. In this study, we hypothesized that assault patients who underwent surgery will have different characteristics before or after surgical intervention. Most of our data was consistent with those from previous studies, but we found that assault injuries increase the likelihood of preoperative diplopia and enophthalmos. According to Tahiri et al. [9], preoperative diplopia is a risk factor for persistent diplopia. Surgeons should take into account such characteristics of assault patients and seek a more objective method of evaluating ocular symptoms. Some ocular findings, such as diplopia, is subjective and difficult to quantify [4]. Hess Aria Ratio is an objective method of examining diplopia according to Fujino et al. [14] and should be utilized by specialists to accurately assess diplopia preoperatively and postoperatively.

Upon analyzing the CT images, we found that there is a significant difference of the degree of enophthalmos in assaulted patients (Table 4). Bone defect size did not show significant difference between the two groups, however. The degree and the presence of enophthalmos are greater in assaulted patients compared to non-assaulted patients. We believe that this phenomenon is due to the transcending force from a fist blow. Additionally, our study finds a positive correlation between bone defect and the degree of enophthalmos. We can utilize the formula mentioned earlier to roughly estimate the bone defect area in mm². The following formula can be used for assaulted patients: E=0.015A+0.538 (E, the degree of enophthalmos; A, the area of the bone defect). On the other hand, the formula E=0.010A+0.401 can be used for the non-assaulted group. Such formulas can be used easily in clinical settings, and our results indicate that there is a stronger positive correlation in assaulted patients.

This retrospective study has some limitations, since patients had been examined by different physicians. Another limitation is that we could not rule out diplopia due to nerve injuries. Symptoms such as diplopia and blurry vision are subjective symptoms, and we had to partly depend on history taking, which might have lowered the reliability of this study. Such symptoms are also likely to be temporary findings, which result as the consequences of soft tissue swelling, contusion, or intramuscular hematoma. Facial CT scans were taken on the day of injury and also after surgery. The main reason for the postoperative CT scan was to rule out any possibility of retrobulbar hematoma, which is a serious complication that can result in blindness. Thus, we were unable to perform follow up CT scans 6 months after the surgery, due to insurance coverage issues, and had to rely on physical examination for long-term data. Despite these limitations, we found that assault patients did show significant difference in the degree of enophthalmos and diplopia, and this phenomenon was associated with relatively larger defect sizes and degree of enophthalmos.

In blowout fracture patients who have sustained a fist blow to the orbit, we suggest facial 3D scans to assess soft tissue herniation and fracture dimensions. Accurate assessment of diplopia and enophthalmos is also necessary in order to predict persistent ocular symptoms and educate the patient of postoperative expectations. Additionally, a thorough understanding of the specific trauma mechanisms and resulting injury patterns is imperative for surgeons. We believe our study will be beneficial to plastic surgeons and many specialists in diagnosing and treating assault related blowout fracture patients.