Intraoperative Use of Ultrasonography in the Reduction of Zygomatico-Maxillary Complex Fractures

Abstract

Study Design: A single blind randomized controlled study. Objective: The aim of this study is to evaluate the use of ultrasonography intraoperatively to assess the reduction of unilateral zygomatic complex fractures with a control group using the conventional blind digit palpation. Methods: The study comprised of a sample size of 24 patients with 21 male and 3 female patients. Patients of all age groups diagnosed with unilateral displaced zygomatic complex fracture with or without mandible fracture were included in the study. The subjects were randomized into study and control groups based on a standard protocol with a total of 24 patients. Imaging was in the form of a preoperative and postoperative 3D computed tomography scan with reconstruction of the maxilla and mandible to interpret the diagnosis for all subjects. The inter-fracture distance of the fractured infraorbital rim were measured in 3 dimensions (antero-posterior, medio-lateral and supero-inferior) and compared pre and postoperatively. Preoperative, intraoperative and postoperative ultrasonographic examination was performed and recorded on all patients at the frontozygomatic region, infraorbital rim and zygomatic buttress to assess the proximity of the fractured margins pre reduction, post reduction and post fixation of the fracture segments. Result: Statistical analytic results were significant in all 3 dimensions when measured postoperatively using computed tomography. Conclusion: Ultrasonography is an effective screening and intraoperative tool in the armamentarium of oral and maxillofacial surgery to assess zygomatic complex fractures, avoiding incisions in aesthetic areas of the maxillofacial region.

Introduction

The zygoma is a tetrapod complex which articulates with 3 sutures of the maxillofacial skeleton namely; frontozygomatic suture, zygomaticotemporal suture and the sphenozygomatic suture with the most stable region being the frontozygomatic suture.[1] The zygomatic bone provides height, width and prominence to the face. The prominence of the zygomatic region predisposes to bear the impact of facial injuries. It is the second most common midfacial bone fractured after nasal bone fractures, and account to 64% of all midfacial fractures.[1] The primary goal in treating a zygomatic complex fracture is to re-establish the anatomy of the zygoma by accurate reduction and to achieve an ideal aesthetic appearance.

Periodically, reductions are checked by direct visualization or blind palpation method to assess the infraorbital rim in zygomatic complex fractures. To achieve a satisfactory results, good exposure and reduction using multiple incisions and adequate fixation by plates are believed to be necessary for satisfactory results.[2,3] However, these conventional surgical approaches require a long surgery time and may lead to unnecessary scarring. The application of intraoperative imaging for maxillofacial surgery has evolved over the years. The use of computed tomography and C-ARM has increased the success rate to assess the reduction of fractures intraoperatively.[4] Keeping in mind the limitations of intraoperative C-arm and computed tomography, real time imaging like ultrasound was favored and has come a long way.

Aim

The aim of this study is to evaluate the use of ultrasound intraoperatively to assess the reduction of unilateral zygomatic complex fractures with a control group using the conventional blind digit palpation.

Materials and Methods

A single blind randomized controlled trial was performed at the department of Oral and Maxillofacial surgery, Faculty of dental sciences at Sri Ramachandra University between March 2014 and October 2016 on patients diagnosed with unilateral zygomatic complex fractures. The study comprised of a sample size of 24 patients with 21 male and 3 female patients. One patient was declared dead postoperatively due to co morbid conditions. Hence, the statistical analysis was evaluated for only 23 patients. The patient age group ranged from 18 to 60 years with a mean age of 29 years. Patients of all age groups diagnosed with unilateral displaced zygomatic complex fracture with or without mandible fracture were included in the study. Patients who had Lefort I/Lefort II fractures, optic injury, associated naso-orbito-ethmoidal complex fractures or undisplaced zygomaticomaxillary complex fractures were excluded from the study. Cases with comminuted midface fractures were excluded from the study as it would interfere with the accuracy of reduction of the fractured site. Moreover, ultrasonographic examinations on comminuted fracture sites would result in higher rates of artifacts and air entrapments which would reduce the efficacy of the study. Therefore, cases with unilateral displaced zygomatic complex fractures were given at most importance to maintain authenticity of the study.

The subjects were randomized into study and control groups based on a standard protocol with a total of 24 patients (control group-12 and study group12).

The protocol for this study included imaging in the form of a preoperative and postoperative 3D computed tomography scan with reconstruction of the maxilla and mandible to interpret the diagnosis for all subjects. A standard CT scanner (GE ADW 4.5 workstation) was used with a 0.60 mm slicing mechanism depicting axial, coronal and sagittal sections [4] (Figure 1 and Figure 2). The inter-fracture distance of the fractured infraorbital rim were measured in 3 dimensions (antero-posterior, medio-lateral and supero-inferior) and compared pre and postoperatively. All subjects of the study group underwent an ultrasonographic examination intraoperatively using a mobile ultrasound machine (SONOSITE S-ICU) with a standard transducer (linear probe—L14-5) in variable frequencies ranging from 6 to 10 MHz. Images were depicted with a 70% gain and 60% depth of focus.

Ultrasonographic examinations were done before reduction, after reduction and after fixation at the frontozygomatic region, infraorbital rim and zygomatic buttress (refer Figure 3, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8 and Figure 11, Figure 12 and Figure 13). The observations were entered on a Microsoft Excel (Microsoft Office Excel 2007 MSO12.04518.1014) spreadsheet with columns and rows (

Table 1. Computed Tomographic Measurements of Control Group of Patients.

AP—antero-posterior, COR—coronal, SI—supero-inferior, ML—medio-lateral.

and

Table 2. Computed Tomographic Measurements of Case Group of Patients.

AP—antero-posterior, COR—coronal, SI—supero-inferior, ML—medio-lateral.

).

Ultrasonographic Protocol

Before proceeding with the study, the primary surgeon underwent a 2 week intensive training with the in house radiologist at our medical center. The surgeon was trained to locate fracture lines in the head and neck region and also read artifacts related to our cases. However, as the ultrasonographic examination was performed by the surgeon in the operation theater, the radiologist was also present intraoperatively during all cases to confirm the examination readings to achieve higher accuracy in reduction and fixation of the fracture site.

Surgical Protocol

All subjects were treated under general anesthesia with nasoendotracheal intubation. Local anesthetic (2% lignocaine with 1:200,000 adrenaline) was administered at the surgical sites. The frontozygomatic fractured site was approached by a Dingman’s lateral eyebrow incision or through the existing laceration. The fractured zygomatic buttress was visualized by Keen’s vestibular approach.[5]

The subjects of the study group underwent an ultrasonographic examination before reduction at the frontozygomatic region, infraorbital rim and zygomatic buttress to assess the discontinuity of the bony fractured margins which were surface marked using a dermi marker at the respective points (Figure 3, Figure 4, Figure 5). These points served as landmarks to assess the reduction of the fracture site post reduction and fixation.

Ultrasonographic examinations were performed post reduction to ensure proper reduction of the fractured segments (Figure 6, Figure 7, Figure 8). A similar surgical technique was adopted in the control group and reduction of the fracture was assessed by using blind digit palpation method.[6]

Two point fixation (titanium/stainless steel mini-plate fixation) was performed at the frontozygomatic and buttress region, using a 4 hole straight/orbital mini-plate at the frontozygomatic region and a 4-hole L mini-plate at the buttress for all subjects[7] (Figure 9 and Figure 10). A final ultrasonographic probing examination was performed post fixation to ensure proper reduction of the fractured segments at the frontozygomatic region, infraorbital rim and zygomatic buttress respectively (Figure 11, Figure 12 and Figure 13). The operated sites were irrigated with betadine and saline. Primary closure was performed in layers using 3-0 round body vicryl and 5-0 ethilon respectively.

Even though a 2 point fixation was performed, the zygomaticosphenoid articulation was achieved. As we did not incorporate any infraorbital incisions, the operating field at the zygomaticosphenoid suture was restricted from ultrasonographic examination. Therefore, it was not included in the study. According to the radiologist, the introduction of the linear transducer at the zygomaticosphenoid suture would result in artifacts due to the adjacent periorbital fat and limited field of vision. A more advanced microscopic linear transducer with higher sensitivity and specificity would aid in examining the zygomaticosphenoid articulation.

Ethical Consent

The study is approved by the ethical committee of the institution and all patients have been informed about the procedure consent was obtained prior to the procedure (Ethics Reference Number – CSP/15/MAR/40/13).

Statistical Analysis

The collected data was analyzed using IBM.SPSS statistics software 23.0 Version. Wilcoxon signed rank test was used to find the significant difference between the bivariate samples in Paired groups (Pre & Post) and Mann-Whitney U test was used for Independent groups (Controls & Cases) similarly.[8] In all the above statistical tools the probability value (<0.05) is considered as statistically significant level.

Discussion

The zygomatic bone or zygoma is a strong buttress of the lateral portion of the midfacial skeleton and is responsible for midface contour and protection of orbital contents.[9] The term “zygoma” comes from the Greek word “zygon” meaning a yoke or crossbar by which two draft animals such as oxen could be hitched to a plough or wagon. The zygomatic bone has 4 bony attachments to the skull through its processes, which if fractured together, is referred to a “tetrapod fracture”, or can occur as an isolated process fracture.[9] Displacement of zygomatic fractures which were disarticulated at the frontozygomatic suture, infraorbital rim and zygomatic buttress region were part of this study.

Among all the intraoperative imaging tools such as C-Arm, computed tomography and ultrasonography, ultrasonography (USG) is preferred as it is easily available and less expensive in comparison to other imaging modalities.[10] The drawbacks of C-Arm and computed tomography are increased radiation exposure to the patient and operating room personnels, use of lead aprons and positioning the patient intraoperatively.[11,12] As there is nil radiation exposure in USG, it is safe to be used in pregnant patients. The main advantage of ultrasonography is it’s “real time” imaging, accuracy, nil radiation exposure and reduced operative time.[13,14] However, the surgeon needs to have good technical skill or guided by a radiologist for accurate scanning and interpretation.

Interestingly, we found that there was overcorrection in 4 cases using the blind digit palpation method to assess reduction. Comparing conventional blind palpation to intraoperative ultrasonography in reduction of zygomatic fractures, ultrasonography did not show any overcorrection and over reduction. However, with the ease of ultrasound, operative time was lesser and results were significant in all 3 dimensions when measured postoperatively using computed tomography (

Table 3. Statistical Analysis of Case Group.

TEST STATISTICS	Z	Asymp.Sig (2-tailed)
POST AXIAL AP- PRE AXIAL AP	−2.825c	.005
POST CORONAL SI-PRE CORONAL SI	−3.061c	.002
POST 3D ML-PRE 3D ML	−3.062c	.002

^aCC = Cases. ^bWilcoxon Signed Ranks Test. ^cBased on positive ranks.

).

The preoperative and postoperative measurements showed a significant P value (0.04) and (0.01) in relation to the axial and 3D measurements for the control group, whereas the coronal measurements showed inaccuracy (P value—0.197). Similarly, the P value (0.05, 0.002, 0.002) showed high significance in all 3 axes in the control group. This explains that conventional blind digit palpation method definitely is the basis to assess good reduction, although reduction in the 3 planes isn’t accurate when compared to the ultrasound guided reduction (

Table 4. Statistical Analysis of Control Group.

TEST STATISTICS	Z	Asymp.Sig (2-tailed)
POST AXIAL AP-PRE AXIAL AP	−2.852c	.004
POST CORONAL SI- PRE CORONAL SI	−1.290c	.197
POST 3D ML-PRE 3D ML	−2.578c	.010

^aCC = Control. ^bWilcoxon Signed Ranks Test. ^cBased on positive ranks.

).

A Systematic review of existing literature has found the sensitivity of USG in accurately measuring the adequacy of reduction to be 98%. In our study, we have attempted to assess adequacy of reduction in a displaced infraorbital rim and cross verified it using a postoperative CT scan. It was found that discrepancies up to 0.09 cm have gone unnoticed on USG assessment.[15,16,17] This could be attributed to soft tissue edema or air pockets which are innate limitations for ultrasound evaluation of structures.[18] We now understand and are of the opinion that such limitations can be overcome only by direct intraoperative visualization compromising on aesthetic outcome of such procedures.

With regard to operating time, there is definitely a reduction in the operating time as an intraoperative ultrasound evaluation makes it easier for the surgeon to manipulate the fracture site. However, it did increase the span of operation time by a few extra minutes due to mobilizing the ultrasound machine and more interaction with the radiologist during surgery. The time factor was not included in this study, but it definitely kept the operating surgeon at ease and resulted in better accuracy with reducing and treating the fracture site.

As an oral and maxillofacial surgeon, it is essential to widen the field of knowledge with regard to radiology, especially with computed tomography, ultrasonography and magnetic resonance imaging. It would definitely aid in the intraoperative procedures and decision making. Nevertheless, it would be a learning curve for all the future maxillofacial surgeons to be more confident in diagnosing and treating zygomatic complex fractures.

Conclusion

Over the years, a standard zygomatic complex fracture reduction was assessed by blind digit palpation method, which resulted in adequate projection and width of the zygoma postoperatively. The use of ultrasonography as an intraoperative tool to assess the reduction of zygomatic complex fractures resulted in near accurate reduction of fractures of the infraorbital rim without direct visualization through a subciliary, infraorbital or transconjunctival incision.[19] Moreover, the projection of the malar process was restored in 3 dimensions with more accuracy. The only limitation with ultrasonography is the reduced intensity to scan the bony outlines in cases of increased soft tissue edema and air pockets which according to literature gave a maximum sensitivity of 98% in reduction of fractures.[20] Therefore, when infraorbital rim reduction is inadequate inspite of ultrasonographic guidance, a direct visualization of the fracture site is recommended, compromising on the aesthetic outcome.

In conclusion, ultrasonography is an effective screening and intraoperative tool in the armamentarium of oral and maxillofacial surgery in the assessment of zygomatic complex fractures thereby avoiding incisions in aesthetic areas of the maxillofacial region.