|ECR 2019 / C-1598|
|Craniofacial trauma: Keys for the radiology report|
Facial skeletal fractures are common and frequently associated with other life-threatening conditions, such as traumatic brain injuries.
Although they represent serious injuries, the workup and treatment of facial fractures is often properly delayed until more pressing problems have been addressed, such as the establishment of an adequate airway, hemodynamic stabilization, and the evaluation and treatment of other more serious injuries of the head, chest and skeleton. Once these problems have been managed, it is time to work up facial fractures.
COMMON CAUSES OF FACIAL TRAUMA
The most common mechanism producing facial trauma is auto accidents. About 70% of motor vehicle accidents produce some type of facial injury, although most are limited to soft tissue.
The face seems to be favorite target in fights or assaults (interpersonal violence), which are the next most common mechanism.
FACIAL SKELETAL ANATOMY
The normal skeletal anatomy of the face frequently is classified into upper, middle, and lower thirds (see Fig. 4 ). This system is used by otolaryngologists to describe locations of fractures in the facial skeletal anatomy.
The upper third of the face consists of the frontal bone (including the frontal sinuses) and is delineated from the middle third by the superior orbital rims and walls.
The mandible or jawbone represents the lower third of the face.
Between the 2 is the middle third of the face which extends downward from the superior orbital rims and orbits and includes the nasal cavity and associated sinuses (maxillary, ethmoid and sphenoid). The midface skeleton is bounded posterolaterally by the zygomaticotemporal sutures, which connect the midface to the calvaria, and posteromedially by the pterygoid plates, which connect it to the skull base.
THE FACIAL SKELETAL BUTTRESSES
The 8 paired skeletal buttresses of the face are regions of increased bone thickness that support muscles, eyes, teeth, and the uppermost airways (see Fig. 5 ).
There are 4 paired vertical facial skeletal buttresses and 4 transverse buttresses, creating a cagelike array of thickened facial bones.
- 1. Lateral maxillary (+ lateral orbital walls of orbit and maxillary sinus): yellow
- 2. Medial maxillary (+ medial orbital wall and lateral nasal walls): purple
- 3. Posterior maxillary (+ pterygoid plates): pink
- 4. Posterior vertical: orange
- 1. Upper transverse maxillary (+ orbital floor): blue
- 2. Lower transverse maxillary (+ hard palate): green
- 3. Upper transverse mandibular: magenta
- 4. Lower transverse mandibular: orange
All of the buttresses are linked, directly or indirectly, to the other buttresses, influencing the transmission of external forces throughout the facial skeleton.
THE ROLE OF CT IMAGING IN PATIENT ASSESSMENT
Multidetector computed tomography (CT) imaging has become the standard choice for quick and accurate assessment of head and face trauma.
Three-dimensional image are reconstructions usually are produced and are useful in diagnostic imaging and surgical planning for high-energy facial fractures because they precisely visualize the location and extent of fractures.
But, although CT offers superior visualization of fractures and other trauma associated with high-velocity impact injuries to the face and head, it is not superior to other imaging modalities for assessing minor damage to bones such as minimally displaced nasal bone fractures. In such cases, and particularly for children, CT is not recommended because of its relatively high radiation doses.
THE PLAIN FILM, THE LINES OF DOLAN AND THE ELEPHANTS OF ROGERS
The plain film facial series has taken a back seat to CT in the past few years, and is now used only in certain situations, such as when the facial trauma is very focal (nasal fracture), or when CT is unavailable.
A basic facial series consists of three or four films:
- 1. A Waters view (PA view with cephalad angulation). See Fig. 6 .
- 2. A Caldwell view (PA view). See Fig. 7 .
- 3. A lateral view. See Fig. 7 .
- 4. A submentovertex view (occasionally).
Of these views, the most consistently helpful view in facial trauma is the Waters view.
There are three anatomic contours best seen on the Waters view of the face, and they were first popularized by Dolan et al. (See Fig. 8 ).
The 3 lines of Dolan lead the eye along some facially important structures. Lee Rogers pointed out that the 2nd and 3rd lines together form the profile of an elephant.
If a nasal fracture is suspected, then a lateral view of the nasal bone with special nasal technique may be done. (See Fig. 9 ).
FRONTAL SINUS FRACTURES
Fractures of the upper third of the face typically affect the wall of the frontal sinus because the bone there is thinner than the rest of the frontal bone.
Result from high-velocity blunt trauma and they are frequently accompanied by other craniofacial fractures, and can be fatal.
Fractures may involve only the anterior sinus wall or extend into the posterior wall (creates a communication between the frontal sinus and the anterior cranial fossa → rhinorrhea, brain herniation and intracranial infection).
A fracture along the medial aspect of the frontal sinus may extend into the nasofrontal duct → mucocele.
See Fig. 10 .
The mandible is another commonly fractured bone in the head, and most of these fractures are obvious on clinical exam.
- Facial distortion
- Malocclusion of the teeth
- Abnormal of portions of the mandible or teeth
The mandible is one of those bones covered by the “ring bone rule”, which may be state thusly: if you see a fracture or dislocation in a ring bone or ring bone equivalent, look for another fracture or dislocation.
The mandible is a U-shaped bone that is connected to the calvaria through the temporomandibular joints, creating a ringlike structure.
Because of this ringlike configuration, a traumatic blow to the mandible typically produces at least two discrete fractures.
Fractures of the mandible are characterized according to their location, the degree of comminution, and the presence of displaced fragments.
Fractures involving the mandibular canal, which traverses the mandibular ramus, angle, and body, may result in injury to the inferior alveolar nerve.
Nasal bone fractures are the most common of all facial skeletal injuries because of the superficial location of the nose and the relative thinness of the bone.
Severe bony septal injury commonly occurs with naso-orbito-ethmoidal (NOE) fractures and they are the most difficult midfacial injuries to diagnose and manage. Isolated NOE fractures are uncommon; up to 60% of NOE fractures are associated with ZMC fractures, and 20% are associated with panfacial fractures.
Orbital fractures are not clinically obvious in unconscious patients with facial swelling; and diagnosis, prognostication, and treatment planning rely heavily on the findings at CT.
Fractures of the orbital walls can be localized and simple (those limited to the internal orbit or “pure”); or they can be complex fractures extending beyond the orbits, such as those extending into or through the orbital rims (those with orbital rim involvement or “impure”).
Both simple and complex orbital fractures can affect the position and integrity of the eyes, eye muscles or optic nerves.
More than 80% of pure internal orbital fractures are blow-out fractures involving the medial wall or orbital floor, increase the risk of enophthalmos or the sinking of the eye from its normal anatomic position. See Fig. 16
Lateral wall involvement is a hallmark of ZigomaticoMaxillary Complex (ZMC) fractures.
Roof fractures are impure, are displaced in up to 95% of cases.
The orbit should be evaluated in three orthogonal planes at CT.
Coronal CT images have the greatest overall utility for assessing defect size, the direction of fractures, and changes in orbital shape and volume.
Axial an sagittal CT images help delineate the posterior defect margin.
CT images with soft-tissue windowing depict the relationship of the extraocular muscles and fibrofatty tissue to fractured segments.
The tetrapod-shaped ZMC fragment dissociates from the midface at four major points of failure:
- 1.The zygomatico-maxillary buttress from the inferior margin of the crest to the inferior orbital rim.
- 2.The zygomaticosphenoid suture along the lateral orbital wall
- 3.The frontozygomatic suture of the lateral orbital rim
- 4.The zygomaticotemporal suture of the zygomatic arch.
The zygomatic surface of the orbit contributes to the lateral orbital wall and floor, and rotation of the ZMC fragment in any axis can dramatically change orbital volume.
ZMC fractures produce facial asymmetry and enophthalmos.
Three-dimensional volume-rendered CT images simplify grading of fractures and are used to plan the magnitude and direction of forces needed for disimpactation and reduction of the ZMC. See Fig. 17 .
LE FORT FRACTURES
Le Fort fractures are classified by the site and extent of fractures, using coronal and axial 2D CT images and 3D surface renderings.
Le Fort I: Involve the lateral and medial walls of the maxillary sinus, propagating posteriorly from the piriform aperture.
Le Fort II: Involve the frontonasal suture, the inferior orbital rim and floor, and the maxillary sinuses, forming a pyramidal shape.
Le Fort III: Extends horizontally from the frontonasal suture to the frontozygomatic suture and zygomatic arches.
All three patterns converge through the pterygoid plates, resulting in dissociation of the involved midfacial segment, and that if the pterygoid plates are intact, a Le Fort fracture is excluded. See Fig. 18 , Fig. 19 and Fig. 20 .
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