Imaging in traumatic mandibular fractures

Abstract

A fracture of the mandible is a common trauma presentation amongst young males and represents one of the most frequently encountered fractured bones within the viscerocranium. Historically, assault was the dominant contributing factor but now due to the increased number of vehicles used per capita, motor vehicle accidents are the primary cause. Mandibular fractures can be classified anatomically, by dentition, by muscle group and by severity. The fracture may also be closed, open, comminuted, displaced or pathological. It is important that the imaging modality used identifies the classification as this will decide definitive treatment. X-ray projections have typically been used to detect a mandibular fracture, but are limited to an anteroposterior (AP), lateral and oblique view in an unstable trauma patient. These views are inadequate to detail the level of fracture displacement and show poor detail of the condylar region. Computer tomography (CT) is the imaging modality of choice when assessing a traumatic mandibular injury and can demonstrate a 100% sensitivity in detecting a fracture. This is through use of a multidetector-row CT, which reduces motion blur and therefore produces accurate coronal and sagittal reconstructions. Furthermore, reconstructive three-dimensional CT images gained from planar views, allows a better understanding of the spatial relationship of the fracture with other anatomical landmarks. This ensures a better appreciation of the severity and classification of a mandibular fracture, which therefore influences operative planning. Ultrasound is another useful modality in detecting a mandibular fracture when the patient is too unstable to be transferred to a CT scanner. The sensitivity however is less in comparison to a CT series of images and provides limited detail on the fracture pattern. Magnetic resonance imaging demonstrates use in assessing soft tissue injury of the temporomandibular joint but this is unlikely to be of priority when initially assessing a trauma patient.

Keywords: 3D reconstruction; Mandibular fracture; X-ray vs. CT; classification of fractures; trauma; trauma imaging.

Figure 1

Classification of mandibular fractures. (A) Classification by Dingman and Natvig (14); (B) classification according to favourable or unfavourable fractures (15).

Figure 2

Classification of mandibular fractures. (A) Classification according to the F–F4 severity scoring system: F1, a single mobile fragment of the alveolar or basal region; F2, single separation of the mandibular arch continuity; F3, two separations of the mandibular arch continuity; or F4, three or more mandibular arch fragments (18); (B) classification of condylar fractures according to Lindahl (19).

Figure 3

Mandibular X-ray series. (A) Posteroanterior radiographic view of a left condylar fracture (arrow), note the obscured detail of the symphysis and condylar region due to the superimposed c-spine and mastoid process respectively (5); (B) left oblique view demonstrating a left angle fracture (arrow), note the normal appearance of the mandibular groove (5); (C) normal appearance of the mandible on a lateral projection, note how the allocated TMJ can be appreciated in this view, case courtesy of Dr. Craig Hacking, Radiopaedia.org, rID40254.

Figure 4

Additional mandibular X-ray projections. (A) Reverse Towne’s view of a left condylar fracture (arrow), note the angle projection allows for clearer detail of the condyles due to no overlapping of the mastoid bone (5); (B) OPG X-ray demonstrating a left parasymphyseal fracture of the mandible (arrow), case courtesy of Dr. Ian Bickle, Radiopaedia.org, rID: 50325; (C) OPG X-ray demonstrating a left parasymphyseal (right arrow) and right body fracture (left arrow), the segmental displacement can be appreciated in this view (5).

Figure 5

CT Facial bones series. (A) Coronal reconstruction of an undisplaced mandibular fracture of the left body (arrow); (B) Sagittal reconstruction of the same patient demonstrating a displaced fracture of the right mandibular body (arrow), projecting posteriorly under the right ramus.

Figure 6

CT Facial bones series. (A) Axial CT image demonstrating a minimally displaced fracture of the right mandibular body (arrow), case courtesy of Dr. Ali Abougazia, Radiopaedia.org, rID: 22763; (B) axial CT image demonstrating a longitudinal fracture of the left mandibular ramus (arrow), case courtesy of Dr. Ali Abougazia, Radiopaedia.org, rID: 22763.

Figure 7

3D Reconstruction of a CT Facial bones series. (A) 3D Reconstructed view of bilateral mandibular body fractures (arrows) of the patient in Figure 5; (B) 3D reconstructed view of bilateral mandibular body fractures (arrows) of the patient in Figure 5. The spatial representation of the displacement of the right mandibular body fracture can be appreciated in this image.

Figure 8

3D Reconstruction of a CT Facial bones series. (A) 3D reconstructed view of patient in Figure 6A, demonstrating a minimally displaced fracture of the right mandibular body (arrow), case courtesy of Dr. Ali Abougazia, Radiopaedia.org, rID: 22763; (B) 3D reconstructed view of patient in Figure 6B demonstrating a longitudinal fracture of the left mandibular ramus (arrow), case courtesy of Dr. Ali Abougazia, Radiopaedia.org, rID: 22763.