Review of Oral and Maxillofacial Surgeons’ Imaging Use for Facial Trauma

Study Design

The survey questionnaire consisted of 20 questions that were tailored to OMF surgeons practicing in various States and Territories of Australia. The questionnaire was primarily focused on the participant’s preferred imaging modality, or multiple modalities, between 2D imaging (including panoramic radiographs), MSCT and CBCT, for maxillofacial trauma. There was one open-ended question to elicit the reason for choosing the specific imaging modality.

The survey was designed to be anonymous and included no sensitive questions which could potentially reveal the identity of the participant. A participant information sheet with informed consent was provided before the survey. There was no perceived physical or psychological risk involved in the study.

Participant Recruitment

The total number of registered OMF surgeons in Australia at the time of the survey was 222, according to the 2018 Australian health professional registrant data.[7] The authors approached the Queensland branch of The Australian and New Zealand Association of OMF Surgeons (ANZOAMS) for distribution of the survey questionnaire to the 200 active Australian ANZOAMS members.

Survey Distribution

The survey questionnaire was first distributed in September 2018. An online link for the electronic survey was created using Checkbox survey software (Watertown, MA, USA) and was emailed to ANZOAMS members. The online survey was available for 6 months. In addition, 40 physical copies of the survey questionnaire were provided to the Queensland branch of ANZOAMS.

Data Management

All completed and returned hard-copy surveys were converted to digital documents and disposed of securely. The final digital data were stored on a password protected standalone computer and were accessed by the primary author.

Data Analysis

Only surveys with all questions completed by currently practicing OMF surgeons were included in data analysis (n = 48). Descriptive statistical analysis was performed using the JASP software program and Microsoft Excel (Microsoft, Redmond, WA, USA).

The current study conforms to the Strengthening the Reporting of Observational Studies in Epidemiology guideline for cross-sectional studies.

Ethics approval for this study was granted by The University of Queensland’s Human Research Ethics Committee before commencement.

Preferred Pre-operative and Post-operative Trauma Imaging

The OMF surgeons in this study were provided with four different scenarios of maxillofacial trauma: “Mandibular fractures not involving condyles,” “mandibular fractures involving condyles,” “maxilla only fractures,” and “other midfacial bone fractures.” The surgeons’ preferred pre-operative and post-operative imaging modalities for each scenario are analyzed and summarized in graphs [Figures 1 and 2] and in Table 2. Near equal results were observed in both pre-operative and post-operative imaging preferences.

Figure 1: Stacked column graph demonstrating the surgeons’ preferred pre-operative trauma imaging modalities

Figure 2: Stacked column graph demonstrating the surgeons’ preferred post-operative trauma imaging modalities

Table 2: Surgeons’ preferred pre- and post-operative imaging modalities in different clinical scenarios

2D imaging, including panoramic radiographs, was the most preferred pre-operative and post-operative imaging modality (69% and 98%, respectively) in the “mandibular fractures not involving condyles” scenario. Multi-slice CT was the surgeons’ most preferred pre-operative and post-operative imaging modality in the other three scenarios [Figures 1 and 2]. In the “other midfacial bone fractures” scenario, especially, 77% of the surgeons preferred MSCT both preoperatively and postoperatively. CBCT was the least preferred imaging modality in all scenarios, both preoperatively and postoperatively. “Better details” (44%) and “machine availability” (40%) were popular reasons why the surgeons preferred MSCT over CBCT in this study.

Preoperatively, 2D imaging (chosen by 33 surgeons) was 17 times more preferred than CBCT (chosen by 2 surgeons) in the “mandibular fractures not involving condyles” scenario; multi-slice CT was 8 and 35 times more preferred than CBCT in “mandibular fractures involving condyles” and “maxillary fractures,” respectively [Table 2]. For post-operative assessment, 2D imaging (chosen by 47 surgeons) was 47 times more preferred than CBCT (chosen by one surgeon) in “mandibular fractures not involving condyles;” MSCT was, again, 8 and 35 times more preferred than CBCT in pre-operative “mandibular fractures involving condyles” and “maxillary fractures,” respectively [Table 2]. No surgeons preferred “CBCT only” imaging for pre-operative and post-operative assessment of “other midfacial bone fractures.”

In this survey, the surgeons were also able to select supplemental 2D imaging to any of the selected 3D imaging modalities (MSCT and CBCT); and MSCT combined with 2D imaging, “MSCT and 2D,” was the second most preferred imaging choice in all scenarios except for “mandibular fractures not involving condyles.”

Applications of 2D Imaging in Trauma

Conventionally, multiple views of 2D conventional imaging were acquired to evaluate fractures in maxillofacial trauma.[8] With the introduction of 3D imaging, such as CBCT and MSCT, 2D imaging is less routinely utilized in trauma. However, in zygomatic arch and mandibular fractures, it is still considered highly diagnostic and is favored by many surgeons. The current standard post-operative imaging protocol at the Royal Brisbane Women’s Hospital for zygomaticomaxillary complex or zygomatic arch fracture also primarily involves 2D imaging: A combination of occipito-mental (OM)15, OM30, posteroanterior (PA) face, and submento-vertex; or, alternatively, and CT imaging.[9] Wikner et al.’s study also state that 2D imaging is useful for diagnosing isolated zygomatic arch fractures.[8] For mandibular trauma without condylar fracture, the participating surgeons in this study favored 2D imaging over MSCT or CBCT, both preoperatively and postoperatively [Figures 1 and 2]. Miele and Trinci’s study evaluated 2D imaging use in mandibular trauma and concluded that it was suitable for assessing fractures in the mandible, the dentoalveolar structures, but not in other facial trauma.[10] This is supported by another study by Koshy et al. who stated that panoramic radiographs were “the best” for assessing dentition-related mandibular fractures, although CT performs the best for other fracture sites in the mandible; CT has a 100% sensitivity in detecting mandibular fractures.[11,12]

Aside from assessing the zygomatic arch and mandibular fractures, 2D imaging is not routinely used on its own. It has been reported that 2D imaging is now more often used in conjunction with 3D imaging in various maxillofacial trauma cases.[13,14] This present survey study also supports this statement as “MSCT combined with 2D” imaging was the second-most preferred imaging modality after “MSCT only” imaging by surgeons for assessment of various facial bone fractures, especially in mandibular fractures involving condyles, maxilla, and other midfacial bone fractures [Figures 1 and 2]. The popularity of the “2D and 3D” imaging combination is most likely due to the surgeons’ improved diagnostic capabilities with various available views by adding relatively low-dose 2D imaging to more comprehensive 3D imaging at minimal cost, time, and storage.[13,15]

Gold Standard Imaging in Trauma: Multi-slice CT

Utilization of 3D imaging modalities such as MSCT and CBCT enables detailed assessment of maxillofacial structures in various reconstructed views without superimposition of anatomical structures or image magnification.[16] In maxillofacial trauma, MSCT is the “gold standard” imaging modality and is the most frequently used modality worldwide.[17] The widely accepted New Orleans CT guideline in maxillofacial trauma also states that “head CT scan is the first-line examination and is recommended for any patient without loss of consciousness or post-traumatic amnesia, or if any of the following is present: Neurological deficit, vomiting, severe headache, age over 65 years, suspected skull-base fracture, Glasgow score < 15, coagulopathy, and trauma with dangerous mechanism.”[18] In addition, MSCT is the only imaging modality which is able to scan the entire body in a supine position at an accelerated speed in polytrauma cases.[19] The average scan time of a head CT is less than 1 s with multi-slice CT scanners.[8] Its exceptional speed allows prompt assessment of fractures and swift preparation of emergency surgery. In cases of complex reconstructive surgery requiring autogenous bone grafts from other parts of the body such as calvaria, iliac crests, and tibia, MSCT is the only modality which scans the entire body without restrictions.[20] Furthermore, MSCT imaging has superior soft-tissue contrast as windowing the greyscale image enables the viewing of both bony and soft-tissues. Soft-tissue windowing is a superb ancillary feature, especially when the facial trauma involves the naso-orbito-ethmoid fractures, facial swelling, and other associated soft-tissue injuries.

All participating OMF surgeons in this study have used MSCT as a primary imaging modality in maxillofacial trauma. It was also the surgeons’ most preferred pre-operative and post-operative imaging modality in most facial bone fracture types [Figures 1 and 2]. Aside from the aforementioned advantages of MSCT use for trauma imaging, the motive behind opting for MSCT is also likely associated with the longer history of MSCT use compared to CBCT and accessibility of the imaging modality. Multi-slice CT scanners of early generations (2-slice and 4-slice scanners) were available for general radiology since the 1990’s.[21] In recent years, not only have MSCT scanners become more readily accessible in hospitals and radiology clinics, they have also become far more advanced (64 or more slices at isotropic voxels).[21] According to the Organization for Economic Co-operation and Development (OECD)’s 2017 health data, the total count of CT scanners in Australia was 1583. The total number of CBCT scanners in Australia was approximately 280 (ranging from 232 to 328) in the same year.[22] CBCT imaging was only added to the Australian Medicare Benefits Schedule in July 2011 as codes: 56025 and 56026. If the CT scanner count by the OECD included all MSCT scanners, there were approximately 5.7 times more MSCT scanners than CBCT scanners in Australia in 2017, somewhat justifying the disparity between MSCT and CBCT use.

The main weakness of MSCT is its highly effective radiation dose. The effective dose of the average CT head scan is 1–3 mSv.[23] Although there is no dose limit to medical radiation exposure in Australia, this dosage is still equal to, or greater than, the current allowable annual dose limit for the general public of 1 mSv.[24] Comparatively, the average effective radiation dose of a large field of view CBCT scan (>15 cm in height) ranges from 0.046 mSv to 0.916 mSv, depending on the type of CBCT machine.[25] This is significantly lower than MSCT’s dosage, considering CBCT is also a 3D imaging modality.

Use of CBCT in Post-operative Imaging

In the current study, CBCT was the least preferred pre-operative and post-operative imaging modality by the participants [Figures 1 and 2]. Although CBCT may be less practical in pre-operative assessments of complex facial trauma, mainly due to its relatively lengthy scan time, non-supine patient positioning, sensitivity to movement and poor soft-tissue image contrast; it is a suitable imaging modality for post-operative examination and for assessing mandibular trauma with or without the involvement of condyles.[6] Sirin et al.’s study compared the accuracy of CBCT to MSCT in assessing fracture of a sheep’s mandibular condyles; there was no statistically significant difference between the two imaging modalities.[26] Kaeppler et al. analyzed the accuracy of CBCT in assessing mandibular fractures and stated, “in patients with suspected mandibular fracture, CBCT increases diagnostic certainty to 90.5%.”[27] Ilguy et al. invited three OMF radiologists to assess multiple dentoalveolar fractures using both MSCT and CBCT scans, and the results showed all three radiologists identifying more fractures on the CBCT imaging than on MSCT.[28] There is evidence in the literature that CBCT sensitivity is superior in identifying small fractures in the multi-fragmented midface and mandibular fractures.[17] CBCT has a superior spatial resolution of hard tissues compared to MSCT.[29] In a systematic review by Caruso et al., who analyzed CBCT use in temporomandibular joints, superior demonstration of hard tissue details was observed, as well as CBCT’s ability to measure condylar volume and surface area.[30]

Limitation of the Current Study

The current study is the first to evaluate the use of diagnostic imaging modalities (between 2D, MSCT, and CBCT) in maxillofacial trauma by Australian OMF surgeons. The major limitations of the current study are: Low response rate, limited details in clinical scenarios for the survey, and reduced accessibility of CBCT compared to other imaging modalities. A follow-up, long-term study is warranted to eliminate the mitigating limitations of the current study.