Maxillofacial trauma is common. Computed tomography is the primary imaging tool for diagnosis. Study interpretation is aided by understanding regional anatomy and clinically relevant features of each subunit. Common injury patterns and the most important factors related to surgical management are discussed.
Key points
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Radiology reports should focus on describing regional injury patterns and discussing factors most pertinent to surgical management.
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LeFort II and III injuries can be thought of as combinations of LeFort 1, zygomaticomaxillary complex, naso-orbito-ethmoidal, internal orbital, and nasoseptal injuries.
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Optimal fixation points for midface injuries coincide with the intersection of fracture pattern lines and regional facial buttresses.
Introduction
Maxillofacial trauma is commonly encountered in emergency departments. Computed tomography (CT) is the primary diagnostic imaging modality. Interpretation is aided by knowledge of the complex three-dimensional (3D) relationships of anatomy. In particular, understanding the relationship of the major facial buttresses to the zygomaticomaxillary complex (ZMC), naso-orbito-ethmoidal (NOE), and LeFort complex injuries allows for more complete understanding of principles of reduction and fixation. Comprehension of injury patterns allows the radiologist and surgeon to focus on the most clinically relevant features of each region. Using a subunit centered approach, the classic higher order complex pattern injuries can be understood in a manner that facilitates optimal treatment.
Epidemiology
The epidemiology of facial fractures varies depending on population and time period studied. An analysis of data from the Global Burden of Disease Study estimated more than 7 million new facial fractures worldwide during the year of 2017. An earlier review of the US National Trauma Data Bank demonstrated more than 400,000 facial fracture-related ER visits in the United States alone during a single calendar year. The most common injury mechanisms include interpersonal violence, motor vehicle collisions, falls, sports injuries, work accidents, and other mechanisms. A male predilection is often observed. The nasal bones and mandible are the most commonly fractured structures.
Nasoseptal Injuries
Nasoseptal injuries are among the most common injuries of the face due to the anterior projection of the nose and its fragility. Knowledge of anatomy aids diagnoses and injury characterization. The bony bridge of the nose consists of paired nasal bones. Lateral to the nasal bones are the frontal processes of the maxilla, interposed between the nasal bones and medial orbital rims. Together these structures form the nasal pyramid, which articulates with the nasal process of the frontal bone at the frontomaxillary and frontonasal sutures ( Fig. 1 A ). At the midline, the vertically oriented bony septum is formed by 2 bones, the perpendicular plate of the ethmoid and the vomer. These anchor the nose to the skull base and lower maxilla, respectively. The cartilaginous portion of the nasal septum is located anteriorly below the nasal bones and interposed between the vomer and perpendicular plate of the ethmoid. The anterior nasal spine protrudes from the inferior midline nasal aperture and anchors the base of the cartilaginous septum ( Fig. 1 A, B). Lateral cartilaginous plates support the lateral soft tissues of the nose and nostrils. ,
Nasoseptal fractures are commonly diagnosed using CT ( Fig. 2 ). Immediate management considerations center around managing epistaxis. The septal nasal cartilage is even more fragile than the bony structures but cartilaginous injuries are usually not detected by CT. As such, any bony injury requires assessment by speculum examination to exclude a septal hematoma. Septal hematomas must be drained acutely because they may result in osteonecrosis, malunion, or abscess. , Restoring esthetics and normal ventilation can usually be accomplished by closed reduction. This can be performed in the early outpatient setting once soft tissue swelling subsides but before fractures begin to set. In some cases, septorhinoplasty may be necessary to restore form and function. CT evaluation should focus on fracture detection and describing details that may aid reduction planning. Nasal pyramid deviation, angulation, and/or impaction can be described. Reduction of bony septal fractures with acute bowing, telescoping, L-shaped angulation, or stair stepping may require forceps.
Orbital Injuries
CT evaluation of the orbits is imperative to diagnosis of traumatic bony and soft tissue injuries. The orbital walls are often injured by transmission of forces through the orbital rim resulting in “blow-out” fractures that increase orbital volume and displace the walls of the orbit outward. Blow-out fractures are most common at the orbital floor and medial orbital wall. Classically, blow-out fractures involve the internal orbital walls only, known as “pure” fractures. Involvement of the orbital rim known as “impure” fractures are usually features of other more complex midface injuries (ZMC, NOE, LeFort II, and so forth). Orbital fractures are often managed conservatively with nose-blowing precautions to prevent air from entering the orbit. Surgical repair may be indicated for large bony fragments, severe fragment displacement, or significant comminution.
The intraorbital fat and extraocular muscles may herniate through fracture defects ( Fig. 3 ) resulting in enophthalmos or muscle entrapment. Large volumes of herniated soft tissue or clinical evidence of entrapment are also surgical indications. Retrobulbar hematomas can occur ( Fig. 4 ) and should be communicated emergently because they may lead to orbital compartment syndrome requiring decompression via lateral canthotomy. , , Multiple types of globe injury may be identifiable by CT including lens dislocations, traumatic cataracts, acute corneal rupture, foreign body retention, retinal detachment, vitreous hemorrhage, and globe rupture ( Figs. 5 and 6 ).
Naso-Orbito-Ethmoidal Injuries
NOE fractures are complex injuries of the midface that involve the nasal pyramid, the medial orbital walls, and the ethmoid air cells. These injuries involve 2 major facial buttresses and separate a portion of the inferior medial orbit from the remainder of the skull. , , The injury pattern includes a fracture across the lateral nasal pyramid from the nasal aperture to the medial orbital rim at the level of frontomaxillary suture, fractures extending between the medial and inferior orbital rims along the medial orbital wall and orbital floor, and a fracture across the anterior maxilla from the inferior orbital rim into the inferior nasal aperture ( Fig. 7 ). Two major facial buttresses are involved. The medial maxillary vertical buttress (nasomaxillary buttress) and the upper transverse maxillary buttress (inferior orbital rim) are each traversed twice. , , The points of intersection of the fractures and buttresses involve thick bone and are thus ideal fixation points for surgical reduction. As such, the most common sites of plate fixation are the frontomaxillary suture, the inferior orbital rim, and nasomaxillary buttress. If there is nasal bone involvement, fixation across the frontonasal suture is sometimes performed (see Fig. 7 ).
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