The Imaging ofMaxil lofacial Traumaand its Pertinence toSurgical Intervention

Nisha Mehta, MDa, Parag Butala, MDb,Mark P. Bernstein, MDa,*

KEYWORDS

� Maxillofacial trauma � Surgery � Imaging

Maxillofacial skeletal injuries account for a largeproportion of emergency department visits andoften result in surgical consultation.1 Althoughmany of the principles of detection and repair arebasic, evolving technology and novel therapeuticstrategies have led to improved patient outcomes.

Thegoalof imagingstudies in the traumasetting isto define the number and location of facial fractures,withparticular attention toward identifying injuries tofunctional portions of the face and those withcosmeticconsequence.Byunderstandingcommonfracture patterns and the implications for clinicalmanagement, radiologists can better construct clin-ically relevant radiology reports and thus facilitateimproved communication with referring clinicians.This article aims to provide a review of the imagingaspects involved in maxillofacial trauma and todelineate its relevance to management.

TECHNOLOGY

Imaging in most emergency departments forsignificant facial trauma begins with CT scanning.Although plain radiographs were once standardimaging, they do not provide sufficient informationto assess injury severity and displacement, twokey aspects essential for emergent managementand surgical planning. In addition, radiographic

The authors have no financial support or interests to disa Department of Radiology, NYU Langone Medical CenAvenue, New York, NY 10016, USAb Institute of Reconstructive Plastic Surgery, NYU LanNew York, NY 10016, USA* Corresponding author.E-mail address: Mark.Bernstein@nyumc.org

Radiol Clin N Am 50 (2012) 43–57doi:10.1016/j.rcl.2011.08.0050033-8389/12/$ – see front matter � 2012 Elsevier Inc. All

positioning is difficult and potentially dangerousfor multitrauma patients, in particular patientsrequiring cervical spine clearance. Modern multi-detector CT (MDCT) scanners have revolutionizedtrauma imaging and provide a fast, safe, cost-effective, and sensitive means for assessingtrauma for bone and soft tissue injuries. Further-more, with the advent of MDCT, facial scanscan now be performed contemporaneously withhead, thoracic, and abdominal scans, facilitatinga rapid assessment for trauma patients withmultiple potential injuries.

MDCT offers excellent spatial resolution, whichin turn enables exquisite multiplanar reformations,and 3-D reconstructions, allowing enhanced diag-nostic accuracy and surgical planning. Thesereconstructions assist in the assessment of frac-ture fragment displacement and rotation as wellas identification of fracture patterns. For thesereasons, MDCT is the imaging technique of choicein maxillofacial trauma.

Although 2-D transaxial and coronal images aremore accurate and sensitive than 3-D reconstruc-tions, 3-D imaging is often preferred by surgeonsbecause it simulates a surgeon’s process of visu-alizing fractures in operative planning. Nonethe-less, it is important to recognize limitations in 3-Dimaging, namely the introduction of artifact during

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Mehta et al44

the reformation process, decreased ability to visu-alize nondisplaced fractures, the lack of adequatesoft tissue evaluation, and difficulty viewing deepfractures on surface views.2

At the Bellevue Hospital and Trauma Centercurrently scans are from the frontal sinusthrough the hyoid bone to include both themandible and the facial bones. Scanning isacquired at submillimeter thickness with overlap(0.625 mm � 0.4 mm) to generate high-qualitymultiplanar reformations and 3-D reconstruc-tions. CT images are reviewed at 2-mm thickreformations oriented parallel and perpendicularto the hard palate to achieve symmetry in boththe transverse and coronal planes. Sagittalimages are also generated for review. All imagesare processed using bone and soft tissue algo-rithms (Fig. 1). Additional oblique or curved

Fig. 1. A 22-year-old man, assaulted, with facial pain. (A) Csinus to the bottom of the hyoid to include the entire faciin bone (B) and soft tissue (C) demonstrate a left lateral oswelling. The globes and lenses are intact. Retrobulbar sofractures of the left zygomaticofrontal suture (short whleft zygomaticomaxillary suture (black arrow). Together,pattern is a ZMC fracture. (E) Oblique sagittal reformatioorbital floor fracture to better advantage giving the surgeof the defect. The optic nerve and superior and inferior re3-D reconstruction in a Water’s projection shows the overaand aids in surgical planning.

reformations and 3-D reconstructions are gener-ated according to the area of interest on a case-by-case basis.MR imaging may occasionally be used to eval-

uate soft tissue injury with the advantage of avoid-ing ionizing radiation while providing excellent softtissue contrast. MR imaging is particularly helpfulin assessing cranial nerve deficits. Although MRimaging also offers multiplanar capabilities, it islimited in its ability to assess cortical bone and isoften not a feasible modality secondary to acces-sibility and availability. In addition, it is usuallyimpractical in the trauma setting due to the needto rule out life-threatening injuries promptly andpatient inability to remain still during the lengthyexamination. Most importantly, metallic fragmentsmust be excluded before imaging with MRimaging.

T scout view shows scan range from top of the frontalal skeleton, including the mandible. Transaxial imagesrbital wall fracture (white arrow) with left periorbitalft tissues are normal. (D) Coronal reformation revealsite arrow), left orbital floor (long white arrow), andwith zygomatic arch fracture (not shown), this injuryn along the plane of the left optic nerve shows theon an improved understanding of the size and depthctus muscles are well displayed on this projection. (F)ll ZMC fracture pattern (arrowheads) in a single image

The Imaging of Maxillofacial Trauma 45

NASAL FRACTURESAnatomy

The nasal region consists of bony and cartilaginousportions. Whereas the anterior nasal septum iscartilaginous, the remainder of the nasal septum,consisting of the posterior perpendicular plate ofthe ethmoid, vomer, nasal crest of the maxilla, andnasal crest of the palatine bone, is bony. The upperthird of the nasal region (consisting of the nasalbones proper, the frontal process of the maxilla,and the nasal process of the frontal bone) is bony,whereas the middle and lower thirds of the nasalregion (composed of the upper lateral and loweralar cartilages, respectively) are cartilaginous.

Injuries

The nose is the most prominent facial projection.Consequently, nasal bone fractures account forapproximately 50% of all facial fractures, with themajority involving the distal third of the nose.3

Because the diagnosis is usually made clinicallyand radiologic evaluation is usually unnecessary,there is limited role for dedicated imaging. Radi-ology reports from head CT scans or imagingdirected at detecting other facial fractures, how-ever, often bring a nasal bone fracture to the atten-tion of the emergency department staff andfacilitate further evaluation, which can prevent clin-ical complications, such as a cosmetic deformity ora septal hematoma resulting in saddle nose defor-mity. In these cases, early reduction prevents bonymalunion, thus avoiding the need for osteotomy toanatomically reduce fracture fragments.

Several classification systems exist for nasaland septal fractures, grouping fractures accordingto whether fractures are unilateral or bilateral,degree of displacement, comminution, midline

Fig. 2. Nasal fractures. (A) Transaxial and (B) coronal CT refbilateral comminuted nasal fractures through the frontal pNasomaxillary sutures lie just anteriorly (small dotted arrow

deviation, and septal and soft tissue injury(Fig. 2). Generally, nasal trauma with septal frac-ture or dislocation causing severe alteration ofthe nasal midline or with severe soft tissue injuryrequires an open repair, whereas most otherscan be treated with closed reduction.4

NASO-ORBITAL-ETHMOID FRACTURESAnatomy

The interorbital space is referred to as the naso-orbital-ethmoid (NOE) region; it represents thebony confluence of the nose, orbit, maxilla, andcranium. The space is defined by the thin medialorbital walls laterally, the sphenoid sinus posteri-orly, the cribriform plate superiorly, and the bonypillar (the frontal process of the maxilla, nasalprocess of the frontal bone, and the thick proximalnasal bones) anteriorly. Several key structures liewithin this region, including the olfactory nerves,the lacrimal sac, the nasolacrimal duct, theethmoid vessels, and the medial canthal tendon.

Injuries

Once an anteriorly directed force is sufficient tofracture the nasal bones, the posterior ethmoidair cells offer little resistance and are easily frac-tured with impaction and resultant telescoping.The fracture pattern then progresses from simplenasal fracture into the NOE type, which addition-ally involves the medial orbit, septum, and naso-frontal junction. This pattern is most often seen inblunt trauma directed at the nasal bridge.

CT is essential to identifying the location of theinjury, pattern type, degree of comminution anddisplacement, and associated fractures and softtissue injury. CT typically demonstrates blood inthe ethmoid air cells and impacted fractures in

ormations of a 25-year-old male victim of assault showsrocesses of the maxillae (arrows), displaced to the right.s). (B) Anterior nasal spine identified by the arrow.

Mehta et al46

the NOE region (Fig. 3). Often, with displaced frac-tures, the nasal septum is buckled on impaction,such that, both clinically and on CT, the noseappears pushed back between the eyes. If leftuntreated, NOE fractures can result in markedfacial deformity with functional and cosmeticimplications, including (but not limited to) telecan-thus, enophthalmos, ptosis, and obstruction of thelacrimal system. These deformities are extremelychallenging to correct secondarily and should beaddressed immediately.5

NOE fractures are commonly associated with LeFort II and III fractures; therefore, the pterygoidplates should be carefully evaluated. One studyshowed that 65% of patients with NOE fractureshad concomitant facial fractures, most commonlya Le Fort maxillary or frontal sinus fracture.6

Disruption of the cribriform plate should be as-sessed because the olfactory nerves can be dis-rupted, and more seriously, this injury can lead tocerebrospinal fluid (CSF) leak, pneumocephalus,or tension pneumocephalus after resuscitationefforts. Also, because NOE fractures are associ-ated with high-impact trauma that involve themedial orbital walls, ocular injuries, such as hyphe-ma, vitreous hemorrhage, lens dislocation, andglobe rupture, should be excluded.7

Radiologically, one of the key segments of theNOE fracture to evaluate is the medial orbital rimwhere the medial canthal tendon inserts. Becausethe medial canthal tendon provides medialsupport to the globe and keeps the eyelid in appo-sition to the globe, recognizing potential injury isimportant to ensure appropriate work-up andtreatment. Identification of a fracture through theinferomedial orbital rim at the lacrimal fossaimplies disruption of the medial canthal tendoninsertion (see Fig. 3B). Injury of the medial canthaltendon is closely associated to injury of thelacrimal drainage system, which can lead toobstruction and epiphora.8

Fig. 3. NOE fracture. A 46-year-old man in a construction athe nasal bones and ethmoid air cells with impaction as thforce. (B) 3-D CT reconstruction shows the multiple interorbthe fracture through the inferomedial orbital rim (arrow)

Many NOE classification types have beenproposed in the literature. The Markowitz systemis among the most common, which categorizesNOE fractures according to the status of themedialcanthal tendon along with the degree of comminu-tion of the fragment of bone to which it remainsattached.9 Practically speaking, it is important forsurgeons to know whether a fracture is unilateralor bilateral and whether it is simple (a large singlesegment) or comminuted. This, in combinationwith identifying associated fractures and assessingthe internal orbit, determines the amount of expo-sure, the type of stabilization, and the numberand type of surgical approaches needed.10 Ingeneral, fractures that demonstrate displacementnecessitate open reduction and stabilization.Marked comminution of the medial orbital wall,particularly in the region of the lacrimal fossa,where the medial canthal ligament attaches andthe nasofrontal ducts are located, can requiretransnasal fixation. If the nasofrontal ducts areinvolved, surgical obliteration is often indicated toprevent the formation of a frontal mucocele. NOEfractures may also extend posteriorly to the opticcanal or superiorly to the frontal sinus and intracra-nial structures, and this should also be noted.

FRONTAL SINUS FRACTURESAnatomy

There is high variability in the frontal sinus, with re-gards to anatomy and volume: 10% of individualshave a unilateral sinus, 5% have a rudimentarysinus, and 4% have no frontal sinus. The anteriorwall is thick and can tolerate as much as 2200 lbof force before fracturing, whereas the posteriorwall is thin and relatively delicate. The dura andfrontal lobes lie just posterior to the posterior table,and the orbital roof and nasofrontal ducts lie justinferior. The only drainage port from the frontalsinus is the nasofrontal duct, located at the

ccident. (A) Transaxial CT image shows comminution ofe nose is pushed back between the eyes from frontalital fractures seen with the NOE fracture pattern. Note, implying medial canthal tendon injury.

The Imaging of Maxillofacial Trauma 47

inferomedial aspect of the frontal sinus, whichempties into the middle meatus.

Injuries

Frontal sinus fractures result from direct anteriorupper facial impact at the frontal bone andcomprise 5% to 12% of all maxillofacial frac-tures.11 They are uncommon, because the nasalprominence usually protects the naso-orbital re-gion. Because of the high G force necessary forfracture to occur, these high-energy injuries resultin 75% of patients presenting with significantinjury, including shock, brain injury, coma, andassociated facial fractures. The force of impactpropels the head and cervical spine into extension,leading to concomitant intracranial injury in 38% ofpatients.12 One-third of injuries are isolated to theanterior table, whereas two-thirds involve bothanterior and posterior tables (Fig. 4).

Prompt and appropriate management is ess-ential, because complications, such as brainabscesses, meningitis, encephalitis, mucoceles,and mucopyoceles, can occur. MDCT should beused as early as possible to exclude injury to thecentral nervous system and determine the locationand extent of injury. Particular attention should bepaid to the anterior and posterior tables and the na-sofrontal duct, because injuries to these threestructures dictate classification and subsequenttreatment.13 Also, if present, pneumocephalus

Fig. 4. Frontal sinus fractures. (A) Transaxial CT image of 1of both the anterior and posterior tables of the frontal sifrontal sinus in a 45-year-old woman after motor vehicleheads). (C) Sagittal CT reformation of a different patientfixation (white arrows). Note absence of the posterior tab

can indicate dural violation, which may promptneurosurgical intervention.

Injury to the nasofrontal outflow tract is present in70%of cases and indicatedby (1) anatomicoutflowtract obstruction, (2) frontal sinus floor fracture, and(3) medial anterior table fracture. Coronal imagesare particularly helpful for evaluating the base ofthe frontal sinus at the site of the ostium of theduct. Fracture fragments within the tract are diag-nostic of nasofrontal outflow tract obstruction.14

Although treatment goals are similar amongsurgeons, controversy regarding exact manage-ment of frontal sinus fractures exists.15 As longas the nasofrontal duct is uninjured and there isno CSF leakage, nondisplaced fractures of theanterior and posterior walls of the frontal sinusdo not usually require surgical treatment. Becauseof the possibility of delayed infection, however,many recommend long-term follow-up with CT.16

Solitary depressed anterior wall fractures canlead to cosmetic deformities and are treated withanterior wall restoration to obtain aestheticallyacceptable contours. Nasofrontal duct injury orposterior wall injury with a dural tear or CSF leakusually requires removal of the sinus mucosa andobliteration of the cavity to prevent mucocele ormucopyocele formation.17 Displaced posteriorwall fractures, particularly when there is morethan one table width of displacement, can requirecranialization to treat ongoing CSF leaks (see

9-year-old man in a motor vehicle crash with fracturesnus. Note pneumocephalus (dotted arrow). (B) Largercrash with only fracture of the anterior table (arrow-after cranialization of the frontal sinus with anteriorle (dotted arrow).

Mehta et al48

Fig. 4C). This involves mucosal stripping, naso-frontal duct obliteration, and removal of posteriortable fragments. In surgical procedures wherethe frontal sinus is preserved, serial CT scans inthe postoperative period are often performed toassess for adequate drainage of the sinus, andfailure of the sinus to clear is an indication ofimpaired drainage that may lead to infection.18 Inthese cases, aggressive medical therapy and/orendoscopic or open surgical drainage are used.

ORBITAL FRACTURESAnatomy

Seven bones make up the bony orbit: the frontalbone, zygoma, maxilla, lacrimal bone, ethmoidbone, sphenoid bone, and palatine bone. Theoptic canal, superior orbital fissure, and inferiororbital fissure are the three openings in the poste-rior orbit. In trauma imaging, fractures of the orbitare usually referenced in relation to the four orbitalwalls: the orbital floor, orbital roof, medial orbitalwall, and lateral orbital wall.

Injuries

Orbital fractures may be isolated or part of a morecomplex fracture pattern. They frequently occur inconjunction with zygomaticomaxillary complex

Fig. 5. Orbital blow-out fractures. A 50-year-old man founbone (A) and soft tissue (B) demonstrate right periorbital smedial orbital wall (white arrows). Irregular appearance to(black arrow). (C) Transaxial image through the upper maindicating a right orbital floor blow-out fracture as wel(dotted arrow) and orbital floor (arrow) blow-out fractur

(ZMC), Le Fort fractures, and NOE fractures. Thereare several typical injury patterns that are seen.The orbital blow-out fracture typically occurs

when an object larger than the bony orbit impactsthe orbit with sufficient force to increase intraorbitalpressure and fracture the thin orbital floor, medialwall, or both (Fig. 5). Blow-out fractures are consid-ered pure when the thick orbital rim remains intact.The free fragment sign on CT demonstrates an iso-lated fragment within the maxillary sinus withdepressed or displaced orbital floor fractures.With an acute injury, hemorrhage into the adjacentsinus should be present. If the sinuses are clear,the injury is likely remote. Fractures through themedial orbital wall that are not blow-out fracturesare rarely isolated and should raise suspicion ofNOE or Le Fort II or III fracture patterns.Common complications include extraocular

muscle herniation and enophthalmos (discussedlater). Orbital emphysema is another complication,in which floor and medial wall fractures allow therelease of adjacent paranasal sinus air into theorbit. Although this is usually a self-limited condi-tion, it warrants comment because it can causemass effect on the adjacent soft tissues and bea rare cause of decreased vision due to eitherocclusion of the central retinal artery or opticneuropathy.19

d unconscious. Transaxial CT through the midorbits inoft tissue swelling with blow-out fracture of the rightthe optic nerve insertion represents optic nerve injuryxillae shows free fragment on the right (arrowhead)l. (D) Coronal reformation shows medial orbital walles.

The Imaging of Maxillofacial Trauma 49

The blow-in fracture usually results from a high-energy impact to the frontal bone and consists offracture and depression of the orbital roof intothe orbit (Fig. 6). Blow-in fractures are often asso-ciated with intracranial injury and loss of orbitalvolume leading to exophthalmos. Associatedocular injuries are reported in 14% to 29% ofcases.20 If the fracture propagates to the orbitalapex, the optic nerve can be injured by direct frac-ture fragment penetration, hemorrhage into thesheath, avulsion from the posterior globe, orischemia resulting from increased intraorbitalpressure. If there is imaging and clinical evidenceof optic nerve impingement, emergent surgicaltreatment is usually indicated because this canbe associated with blindness as well as injury tothe cavernous portion of the carotid artery.

The blow-up fracture involves cranial displace-ment of the orbital roof, which increases orbitalvolume and is strongly indicative of intracranialinjury (Fig. 7). Isolated lateral orbital wall fracturescan occur but are more commonly associated withzygoma fractures with disruption of the zygomati-cofrontal suture.

CT imaging plays a key role not only in diagnosisof these fractures but also in determining manage-ment. Although indications for surgical repair arecontroversial, evidence of mechanical entrapmentor evidence of enophthalmos includes well-established criteria mandating urgent repair.

Particularly with orbital blow-out fractures, theremay be resulting herniation of the intraorbital fatand rectus muscles, which can lead to entrapmentof the muscles on a free edge of the fracture frag-ment causing diplopia. Entrapment is a surgicalemergency and lack of evidence of entrapment on

Fig. 6. Bilateral blow-in fractures. A 52-year-old mansuffered a knee to the head playing softball. CoronalCT reformation shows bilateral orbital blow-in frac-tures (arrows). Note the significant bilateral frontallobe contusions (asterisk).

CT does not exclude the condition, and a carefulphysical examination is critical. CoronalCT ispartic-ularly useful for displaying herniation and cansuggest entrapment based on kinking of a muscleor isolation of the inferior rectus muscle (Fig. 8).The inferior rectus muscle normally appears ovalon coronal images; if it appears round, pathologyshouldbesuspected.Making thediagnosisof herni-ation is particularly challenging in the case of trap-door fractures, most common in pediatric patientssecondary to more pliable bone. In these cases,the orbital floor is fractured and displaced inferiorlybut then snaps back into place; however, the herni-ated inferior rectus muscle remains trapped acrossthe fracture and is at risk of ischemia. CT findingsof this type of herniation are particularly subtle,and the only sign may be the loss of the inferiorrectus muscle shadow in the orbit.21

Another parameter in determining the need forsurgical intervention is the size of the orbital floordefect, because larger defects increase the risk offuture enophthalmos. With this condition, the globesinks posteriorly and inferiorly into the maxillarysinus. Many surgeons opt for repair in any defectgreater than 1 cm2, whereas others use a standardof displacement greater than 50% of the orbitalfloor. Other surgeons judge by the amount of fat orsoft tissue displacement. Some use CT to calculatethe increase in orbital volume compared with theuninjured side and then use this to determine therisk for postinjury enophthalmos22; however, nofirm data exist to support this approach. Becausecriteria vary among surgeons, the size of each frac-ture should be estimated in the radiology report.

Surgical repair can consist of either a bone graftfrom the outer table of the skull or the use of a tita-nium or resorbable implant. If an implant is used,the patient should be monitored for new-onsetdiplopia and, if present, emergent CT scan shouldbe performed to ensure there is no mechanicalimpedance. When evaluating for placement, careshould be taken to ensure that floor implants aredirected superiorly to simulate the superior inclineof the orbital floor (Fig. 9).

Globe Injury

Injury to the globe, retrobulbar hematoma, andoptic nerve injury are considered more emergentthan entrapment or enophthalmos; therefore, thesesoft tissue injuries should be assessed immediatelywhen approaching a facial CT.23

Penetrating ocular injuries can lead to globerupture secondary to pressure gradients favoringextrusion of the vitreous, because normal intraoc-ular pressure is higher than intraorbital pressure.The flat tire sign, seen on CT as posterior flattening

Fig. 7. Orbital blow-up fracture. A 40-year-old man assaulted. Coronal (A) and oblique sagittal (B) reformationsshow cranial displacement of left orbital roof fracture fragment (arrows). Note pneumocephalus (dotted arrows)implying violation of the dura.

Mehta et al50

of the globe, indicates globe rupture (Fig. 10A).Globe hemorrhage can be intravitreous, sub-scleral, or subretinal (see Fig. 10B).Lens dislocation is diagnosed by a dependent

lens lying on the retina (see Fig. 10C). In the caseof partial tear of the zonular fibers, lens subluxationmay be seen on CT as an oblique or verticallyoriented lens, supported anteriorly on one side. Ifone lens appears hypodense relative to the contra-lateral lens, acute lens edema should be suspectedbecause this may lead to a traumatic cataract. Thedifference in attenuation is usually approximately30 Hounsfield units.Often, it is difficult to evaluate optic nerve func-

tion clinically in the emergency room setting.Therefore, CT scan plays an important role in eval-uation of the optic nerve. Transaxial and obliquesagittal images are particularly helpful in deter-mining the presence of an optic nerve hematoma(see Fig. 5B).Size and density are important in determining

the detectability of foreign bodies. Metallic foreign

Fig. 8. A 53-year-old woman pedestrian struck by car.Coronal CT reformation shows left orbital floor frac-ture with herniation of orbital fat. The inferior rectusmuscle appears enlarged, compared with right side,and lies up against the free orbital floor edge (arrow),raising concern for entrapment.

bodies are readily identified; however, dry woodand plastic appear hypodense on CT, similar toair and fat, respectively. Because it can be difficultto differentiate a foreign body and air, it is helpfulto look for a geometric margin. Despite this, attimes, a nonmetallic foreign body is difficult toexclude and MR imaging can be helpful, providedthat a noncontrast head CT has excluded the pres-ence of a metallic foreign body.24

Lastly, a rare condition that requires emergentintervention and must be assessed in the settingof trauma is the presence of a carotid-cavernousfistula. This is done by evaluating the facial CTfor the presence of a dilated superior ophthalmicvein, a nonspecific finding that indicates theneed for confirmation with CT angiography orconventional angiography.25

ZYGOMAAnatomy

The malar eminence defining the anterolateralcheek projection is formed by the zygoma, whichhas four principal attachments–the frontal bone,the maxilla, the arch of the temporal bone, andthe greater wing of the sphenoid. They therefore

Fig. 9. A 21-year-old woman after repair of orbitalfloor blow-out fracture. Oblique sagittal CT reforma-tion shows titanium plate across the large orbitalfloor defect.

Fig. 10. Globe injuries. (A) Transaxial CT reformation of a left globe rupture in a 16-year-old girl after motorvehicle crash. Flattening of the posterior globe is common, referred to as the flat tire sign. (B) Globe hemorrhageon the left seen in a 38-year-old man after penetrating injury. (C) Right lens dislocation (arrow) in a 77-year-oldman after fall.

The Imaging of Maxillofacial Trauma 51

contribute a large proportion of the orbital floorsand lateral orbital walls.

Fig. 11. Depressed zygomatic arch fracture. TransaxialCT image of a 51-year-old man post assault showsa comminuted depressed left zygomatic arch fracture(arrows). Fragments impinge on the coronoid processof the mandible (arrowhead).

Injuries

The prominent position of the zygoma makes itparticularly susceptible to traumatic injury. Al-though the zygoma itself is a strong bone andcontributes to the buttress system of the midface,the surrounding sutures and bones that articulatewith the zygoma are weaker. A common resultingfracture pattern is the ZMC fracture pattern, whichusually results from an anterolateral impact to thecheek and effectively separates the zygoma alongits sutural attachments (see Fig. 1B–D). Thispattern represents a spectrum of fractures varyingin the degree of bone loss and displacement. Clas-sically referred to as a tripod fracture, the term isa misnomer and should be avoided, because itoverlooks the posterior attachments of thezygoma.

Isolated fractures of the zygomatic arch areuncommon, representing only 11% of zygomaticarch injuries.26 These do not require operativereductionunless there is severedepressioncausingacosmeticdeformity or inability to completely closethe jaw due to impingement of the depressed archon the coronoid process of the mandible (Fig. 11).Fractures along the zygomaticomaxillary sutureoften extend across the infraorbital canal and caninjure the infraorbital nerve, resulting in malarparesthesia.

CT is crucial in determining operative manage-ment of fractures, particularly because swellingoften precludes accurate clinical assessment of

deformity. Transverse, coronal, and 3-D imagesare particularly helpful (see Fig. 1D–F). The degreeof comminution and displacement is important,because severe comminution affects the preferredsurgical approach for exposing and subsequentlyaligning the arch.27 Concurrent zygomatic archfractures are not always obvious on CT, and defor-mity of the arch is sufficient to suggest a fracture.Another frequently overlooked ZMC fractureoccurs in the temporal bone portion of the uppertransverse maxillary buttress. This angulationmust be reduced before other fractures are ad-dressed or facial width is increased and underpro-jection of the cheek results.28

Mandible fractures are the most commonlyassociated fracture with fractures of the zygomaticarch, accounting for 21% of coexisting fractures.29

The orbital floor and orbital apex are also

Mehta et al52

commonly injured. As discussed previously withorbital floor fractures, there are multiple criteriafor orbital exploration, and CT findings of degreeof comminution and displacement should be re-ported. Some studies report that approximately30% to 44%of patients with ZMC fractures requirean orbital incision. For orbitozygomatic fractures,the lateral orbital wall, in particular, should be as-sessed on the transaxial images, because this isthe location of the articulation of the zygoma withthe greater wing of the sphenoid. The large widthof this articulation facilitates assessment fordegree of displacement and malposition of thefractured fragments. Nondisplaced orbitozygo-matic fractures can be managed nonoperatively.If, however, displacement of the greater wing ofthe sphenoid is medial and into the orbital apex,there is resulting danger to the internal carotidarteries and multiple cranial nerves of thecavernous sinuses.30 Displaced fractures arealmost always treated with operative reduction

Fig. 12. Facial buttresses. Strong vertical buttresses are shoto lateral these are the nasofrontal buttress, zygomatic bbuttresses are shown as curved, thinner, double arrows.

and fixation and should be performed as soon aspossible, because osteotomies may be necessaryafter 3 to 4 weeks.

MAXILLARY FRACTURESAnatomy

The central midface is occupied by the pairedmaxillae, which form the upper jaw. The maxillaehouse the maxillary teeth by way of the alveolusand attach laterally to the zygomatic bones. Thefacial buttress system highlights lines of inherentstrength across the midface, with the strongestbuttresses vertically oriented and the horizontalbuttresses providing secondary support (Fig. 12).

Injuries

There are three classic fracture patterns of themaxilla, Le Fort I, II, and III, which by definitiondetach the maxilla from the skull base via fracturethrough the pterygoid plates (Fig. 13). Most

wn as curved thick black double arrows. From medialuttress, and pterygomaxillary buttress. The horizontal

Fig. 13. Le Fort fracture patterns. Le Fort I pattern (dashed line) traverses the maxillae and lower nasal septum.Le Fort II pattern (dotted line) runs obliquely across the maxillae to the inferior orbital rims and crosses the nasalbridge. Le Fort III pattern transversely crosses the orbits and nasal bridge and involves the zygomatic arches. All LeFort patterns extend posteriorly to fracture the ptyergoid plates (circle).

The Imaging of Maxillofacial Trauma 53

midface fractures are asymmetric, although LeFort’s initial descriptions outlined symmetric frac-ture patterns. Therefore, patients often have anasymmetric Le Fort fracture pattern.

A Le Fort I fracture pattern is the result of directhorizontal impact to the upper jaw creating maloc-clusion with a free-floating hard palate. This resultsin a transverse fracture through the maxillapassing above the tooth roots, crossing the floorof the maxillary sinus and lower nasal septum,with posterior extension through the pterygoidplates (Fig. 14). It does not involve the infraorbitalrims.

Fig. 14. Bilateral Le Fort I fractures. Transaxial CT imagethrough the maxillae in a 33-year-old woman ejectedfrom motor vehicle shows fractures of the anterior,medial, and posterior maxillary walls bilaterally. Frac-tures through thebilateral pterygoidplates arepresent(arrows), indicative of the Le Fort fracture pattern.

Direct impact to the central midface results ina Le Fort II fracture, which separates the nasalregion from the cranium. It is a pyramidal fracturethat crosses the zygomaticomaxillary suturesbilaterally, fracturing the inferior orbital rims medi-ally, and traverses the nasal bridge. Posteriorly,there is fracture of the pterygoid plates (Fig. 15).

Complete craniofacial disjunction is referred toas Le Fort III fracture. The fracture is suprazygo-matic and transversely extends across the naso-frontal suture and across the medial and lateralorbital walls, separating the zygomaticofrontalsutures and zygomatic arches and terminatingthrough the pterygoid plates (Fig. 16).

Because Le Fort fractures usually result inmarked damage to both the facial buttresses andthe more fragile posterior bones, these fracturescause significant functional and cosmetic defi-ciencies. Often, similar to NOE fractures, there isbackward displacement of the central midface.Additionally, damage to the vertical buttressescan lead of loss of facial height. Given the highincidence of concurrent facial fractures, surgicalrepair after these injuries is usually complex.

Of particular concern are the highly associatedconcomitant fractures of the hard palate, dentoal-veolar units, and/or mandible, which disrupt occlu-sion. Reestablishment of normal occlusion mustoccur before attempting to surgically anchor theupper midface to the maxilla. Similarly, injury to

Fig. 15. Bilateral Le Fort II fractures in a 40-year-old man after motor vehicle crash. (A) Coronal CT image showsfractures through the lateral maxillary walls (long arrows), inferior orbital rims (short arrows), and across themedial orbital walls (arrowheads), creating a pyramidal fracture characteristic of the Le Fort II pattern. (B)Coronal image posteriorly shows comminution of the pterygoid plates (arrows). (C) 3-D reconstruction showsthe Le Fort II fracture pattern in a single projection (arrowheads).

Mehta et al54

the frontal bar from concurrent ZMC, NOE, orfrontal sinus fractures requires correction beforeresuspending the midface from the frontal bar.Degree of comminution is another important

factor, because severe comminution may pre-clude adequate restoration of facial height andprojection, thus necessitating bone grafting.Unfortunately, many Le Fort fractures can tra-

verse the orbital apex. As discussed previously,the orbital apex is associated with injuries to thecarotid canal. Because the surgical repair mecha-nism for Le Fort fractures generally entails the useof significant manual force on the part of a surgeon,it is important for the surgeon to know preopera-tively how close the fracture line extends to theorbital apex and carotid canal so that a moregentle reduction technique can be used.

MANDIBULAR FRACTURESAnatomy

The mandible is a horseshoe-shaped bone con-sisting of a curved anterior horizontal portion, thebody, with two perpendicular posterior verticalstruts, the rami. There is a superior anterior projec-tion from each ramus, the coronoid process, whichserves as the attachment for the temporalismuscle, as well as a superior posterior projectionfrom each ramus, the condyle, which articulateswith the temporal bone at the temporomandibular

joint. The temporomandibular joints are the onlymobile segments of the facial skeleton and arecomplex synovial joints that permit hinge, transla-tion, and rotational movements. The mandibleforms the lower jaw and holds the mandibularteeth in place. It contains the inferior alveolar nervecanal, which houses the inferior alveolar nerve aswell as serving as an attachment for the musclesof mastication.

Injuries

Mandible fractures represent a large proportion offacial fractures and are typically caused byassault. They are classified according to anatomy(symphysis, parasymphysis, body, angle, ramus,coronoid, subcondylar, and condyle), and at least50% are associated with a second fracture. Themost common 2-part fracture is the parasymphy-seal fracture with a contralateral subcondylar frac-ture (Fig. 17). A flail mandible is a symphysealfracture with bilateral subcondylar fractures thatnecessitates surgery to restore preinjury facialwidth and height (Fig. 18).Once a fracture is identified, the primary goal is

to restore preinjury occlusion, with managementranging from nonoperative to mandibulomaxillaryfixation with arch bars and occlusal wiring, toopen reduction and internal fixation or, in thecase of a contaminated wound, external fixation.31

Fig. 16. Bilateral Le Fort I, II, and III fractures in a 30-year-old woman pedestrian struck by truck. Coronal refor-mations from anterior (A) to posterior (C). Le Fort I fractures shown by dashed line in (A) and (B). Le Fort II frac-tures shown by dotted line in (A) and (B). Le Fort III fractures shown by transverse solid line (B) and arrowsthrough the posterior zygomatic arches in (C). (C) Pterygoid plates are comminuted (arrowheads).

The Imaging of Maxillofacial Trauma 55

CT is nearly 100% sensitive in detecting frac-tures of the mandible, which is superior to the86% sensitivity of curved panoramic (Panorex)radiographs. CT is often insufficient, however, to

Fig. 17. Mandible fracture in a 19 year old male postassault. Panoramic curved CT reformation shows sub-condylar fracture on the right (long arrow) and para-symphyseal fracture on the left (short arrow).

evaluate dental structures, and the Panorex radio-graph can better visualize dental root fractures,particularly when the fracture is located at theangle.32 Panoramic radiographs are thus oftenused in conjunction with the CT and particularlyhelps elucidate the relationship of fractures at themandibular angle to the surrounding teeth (mostimportantly, the third molars). Cervical spine clear-ance is necessary before the acquisition of thePanorex radiograph.

Fractures through the tooth socket and alveolusare open fractures. Acute tooth loss is implied bya radiolucent socket and should prompt furtherevaluation for aspirated or ingested tooth frag-ments. Many surgeons consider most mandibularfractures as open fractures, therefore regardingthem as contaminated, an indication for antibioticprophylaxis. Some surgeons recommend toothextraction if the fracture contains a tooth or if thereis evidence of abscess.

Fig. 18. Flail mandible in 32-year-old intoxicated male intoxicated. Transaxial images show (A) bilateral condylarfractures (arrowheads) and (B) symphyseal fracture (arrow).

Mehta et al56

SUMMARY

Maxillofacial fractures are common, and knowl-edge of fracture patterns and their implication formanagement is crucial to facilitating effectiveand efficient communication between the radiolo-gist and the referring physician. When possible,pertinent details should be delineated in radiologyreports.

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