imaging of facial trauma part 2

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Emergency Radiology: Imaging of Facial Trauma Rathachai Kaewlai, MD

Imaging of Facial TraumaPart 2: Pathology

Rathachai Kaewlai, MDSpecialized in Body Imaging and Emergency Radiology

[email protected] January 2007

The author is willing to receive any input, comments and corrections, Please do not hesitate to contact at the email address provided above.

mailto:[email protected]

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Outline

• Facial and mandibular fractures– Nasal fractures– Nasoorbitalethmoidal (NOE) fractures– Frontal sinus fractures– Orbital fractures

• Blowout fractures• Blowin fractures• Floor fracture• Orbital apex fracture

– Zygomatic fractures• Zygomatic complex (ZMC) fractures• Isolated zygomatic arch fracture

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Nasal Fractures

• Most common fracture of the facial bone• Etiology: motor vehicle collisions (MVC) most common, followed

by assaults• Relevant anatomy: Nasal pyramid consists of

– Nasal bones • Inferior part of nasal bones is thinner than superior, more prone to fx

– Frontal processes of maxilla– Nasal septum (superior = perpendicular plate of ethmoid, inferior =

vomer, anterior = quadrangular cartilage) – Lateral cartilages (upper and lower lateral cartilages)

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Nasal Fractures

• Pattern of nasal fractures depend on direction of force– Frontal direction (frontal blow)

• May cause a simple nasal fx• Can be more severe with flattening of nose, septum and more

complicated fx such as nasoorbitalethmoidal fx– Lateral direction (lateral blow)

• May cause depression of ipsilateral nasal bone• May also fracture contralateral nasal bone• Interlocking of nasal bone and cartilage may occur; requiring open

reduction for adequate cosmetic result– Inferior direction (blow from below)

• Usually with septum (quadrilateral cartilage, bony septum) fx and dislocation

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Nasal Fractures

• Diagnosis:– Made based on physical examination findings

• Visible bony deformity in displaced fx• Laceration, ecchymosis, hematoma, mucosal tear and epistaxis in the

inner surface of the nasal cavity strongly suggest fx– Presence of epistaxis and septal hematoma requires prompt

diagnosis and treatment• Epistaxis can be life threatening• Septal hematoma may lead to cartilage necrosis and resultant saddle

nose deformity– Telecanthus is an indication of more severe injury, further

workup including CT scan is required

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Nasal Fractures

• Plain film radiography– Plain film can miss up to nearly half of the patients with nasal

fractures– Nasal bone series:

• Lateral nasal views (soft tissue technique)• Water’s view

• CT– CT better depicts fx, especially frontal process of maxilla.

Depressed fx of frontal process of maxilla can lead to facial deformity if left untreated

– CT should be performed if there is more than a simple nasal fracture on xray

– Presence of telecanthus prompts CT workup

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Nasal Fractures, frontal blow

39yoman (cop vs. robber) was punched from the front

Comminuted bilateral nasal bone fractures (red arrows) with displaced fragments.

N = nasal boneM = Frontal process of maxillaBlack arrow = Intact nasomaxillary suture

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33yoman was punched by a righthanded person

S = Bony nasal septumE = Ethmoid sinusSp = Sphenoid sinus = Orbital emphysema (in this case, from maxillary sinus fracture)

Nasal Septum Fractures

Fractures of the left frontal process of maxilla (red arrow) and right nasal bone (green arrow) are noted. The fractures are displaced to the right, indicating the force of impact from the left. The righthanded person hit the left side of the nose of the victim.

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67yoman involved in a motor vehicle collision

S = Bony nasal septumE = Ethmoid sinusBlue arrows = Frontal process of maxilla = Trapped air in preseptal region (anterior to the globe)

Nasal Septum Fractures

Deformity of the nose pointing toward the left. Angulation of the cartilagenous portion of the nasal septum (red arrows). Blood in the nasal cavity is present as soft tissue density.

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Nasoorbitalethmoidal (NOE) Fractures

• Etiology: – Forceful frontal blow to the central aspect of midface. – Most common from motor vehicle collisions (MVC), followed by

assaults• NOE fractures involve the central upper face, disrupting the

medial orbit, nose and ethmoid sinuses• NOE fractures are distinguished from simple nasal

fractures by– Posterior disruption of medial canthal region, ethmoids and

medial orbital walls

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• Relevant anatomy:– NOE complex consists of nasal, frontal, maxillary,

ethmoid, lacrimal and sphenoid bones– Superior to NOE complex is anterior cranial fossa– Lateral to NOE complex is globe– Deep to NOE complex is optic canal and sphenoid

bone– Center of NOE complex is interorbital space,

consisting of ethmoid sinuses, lacrimal drainage system, nasofrontal ducts

– NOE fractures can injure significant surrounding structure

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• Relevant anatomy– Medial canthal tendon

• A crucial soft tissue component of NOE complex• Medial portion of orbicularis oculi, inserting to the medial orbital wall• Acts as a suspensory sling for the globe and ensure close apposition of

the eyelid• In NOE fractures, medial canthal tendon pulls the fragment laterally, or

(rarely) torn, causing telecanthus

• Helpful clinical signs to detect traumatic telecanthus– Intercanthal distance > interpalpebral distance of the eyes– Intercanthal distance more than onehalf of interpupillary distance– Clinically, the most obvious deformity is loss of nasal

projection in profile and apparent telecanthus

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• Three types of NOE fractures– Type I: Large fragment of medial orbit, medial canthal insertion is

intact– Type II: Comminution of bones, fracture line does not extend into

area of medial canthal insertion– Type III: Comminution of bones, fracture line extends into area of

medial canthal insertion

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• Pertinent radiologic information– Degree of comminution of medial orbital wall, especially in the

lacrimal fossa where medial canthus attaches– Involvement of nasofrontal ducts require surgical obliteration of

frontal sinus to prevent frontal mucocele– Extension

• Posterior extension to the optic canal• Superior extension to the frontal sinus, intracranial structures

• Complications– Persistent telecanthus– Injury to lacrimal system– Nasofrontal duct impingement

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NOE Fractures, bilateral, type II or III

21yoman was assaulted

E = EthmoidM = Maxillary sinusSp = Sphenoid sinus= Orbital emphysema

Frontal blow to the nasion results in a comminuted fracture involving the medial walls of both orbits (green circle), nasal bones (green arrow) and frontal processes of maxillae (red arrows) as shown in image A. Blue arrows indicate the attachment sites for medial canthal tendons. Posterior displacement (depression) of the nasion is noted in image B.

B

A

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DC3D images better depict degree of displacement and depression of the NOE fractures. The fractures also extend to frontal sinuses (F). Comminuted fractures of bilateral nasal bones (N) and frontal processes of maxillae (M). Small images on right lower corners represent normal anatomy in the same projections. From radiological perspective, type II and II NOE fractures may not be differentiated.

Radiologic description should comment on degree of comminution of medial orbital wall especially in the region of lacrimal fossa, where the medial canthus attaches and nasofrontal ducts locate.

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Frontal Sinus Fractures

• Etiology: motor vehicle collision (most common), followed by highimpact sport related injuries

• Clinical– Gross depression or laceration over supraorbital ridge,

glabella or lower forehead (most common finding on clinical exam)

– Ophthalmologic evaluation may be necessary because up to half of patients have orbital trauma

• Classification of fractures– Location: anterior wall, posterior wall, or both– Appearance: linear, comminuted, depressed or nondisplaced

• Isolated anterior wall fracture is most common

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• Relevant anatomy– Frontal sinus first appear 68yrs, fully pneumatized in adolescence.– It can be asymmetric/partial incomplete pneumatized up to

20% of population– Frontal sinus drainage via either nasofrontal duct located

posteriomedially in the sinus (the only drainage pathway of frontal sinus may be absent in general population) or in conjunction with anterior ethmoid air cells. The nasofrontal duct, if present and fractured, can be obstructed leading to chronic drainage complication

– Frontal sinus is closed to dura, frontal lobe, crista galli and cribiform plate

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• Indication for surgery– Fracture potentially injures nasofrontal duct (fx involves base of

frontal sinus, medial to supraorbital notch)– Depressed anterior wall cosmetic deformity– Posterior table fx with gross CSF leak, more than one table width

displacement• Pertinent radiologic information

– Status of nasofrontal duct, posterior wall, frontal lobe injury• Complication

– Early complication: frontal sinusitis (retained FB in sinus) leading to meningitis, osteomyelitis, orbital abscess or brain abscess

– Late complication: mucocele, mucopyocele, delayed CSF leak

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Two examples. Young patients who were assaulted.

Above: Isolated anterior wall fracture (red arrows) with hemosinus. Intact posterior wall (blue arrow). This type of depressed fracture causes cosmetic deformityBelow: Both anterior and posterior table fractures (red and green arrows), which are nondepressed. Pneumocephalus (white arrow)

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Scout CT: Asymmetrical haziness of the left frontal sinus (normal frontal sinus on AP skull radiograph should have same density to the orbit) indicates hemosinus (red arrow).

Axial CT: Fracture of the posterior wall of the left frontal sinus (green arrows) is demonstrated. There is displacement of the fracture fragments into the sinus. Small pneumocephalus is noted deep to the fracture. The patient also has anterior wall fracture (not shown). Isolated posterior wall fracture is rare.

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Orbital Fractures

• Plain film radiography has false negative rate of 730%• CT in axial, and coronal planes are essential to determine

presence of fractures and status of intraocular muscle– Axial: medial, lateral wall fracture, entrapment of medial rectus

muscle– Coronal: floor, roof fracture, entrapment of inferior rectus muscle,

fracture involving nasolacrimal duct– Both are helpful for fx of optic canal, retroorbital hematoma

• Two main types– Blowout fractures– Blowin fractures

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Orbital Fractures

• Blowout fractures– Bone is displaced away from the orbit– May involve the roof, floor, and medial or lateral walls of the orbit

• Most common = floor– If orbital rim is intact = ‘pure’ blowout fracture (classic fx)– Up to 30% have ocular injury– Two proposed mechanism of injury

• Hydraulic mechanism: pressure on eyeball increases intraorbital pressure, then the orbit ruptures at its weakest point (thin floor)

• Buckling mechanism: blow to orbital rim results in fx of orbital wall– Clinical

• Enophthalmos, diplopia and hypoesthesia (infraorbital nerve distribution). This can be obscured due to swelling

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Orbital Fractures

• Blowout fractures– Pertinent radiologic information

• Appearance of inferior rectus muscle on coronal images– Normal = oval shape– Abnormal = round shape

• Location of inferior rectus muscle– Abnormal = located below the expected level of orbital floor

• Abnormal inferior rectus can be – Entrapped: muscle lies completely beneath or within the defect and

appears round on coronal images– Hooked: portion of muscle lies within the defect

– Entrapment of inferior rectus in children can be easily missed, since flexible bone springs back into place like a trap door, looking normal at CT except for entrapped muscle beneath it

• This requires urgent Rx within 2472 hours to minimize motility problem

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Orbital Blowout Fractures

Middle age patient involved in motor vehicle collision

Coronal images (in bone and soft tissue windows) show the defect (red arrow) in the floor of the right orbit with a small hematoma in the right maxillary sinus (green arrow). Light blue arrows point to the inferior rectus muscle, where its inferior portion (blue arrow) is hooked to the defect. Clinically, the patient does not have entrapment

O = Optic nerve= Facial soft tissue edema

Clinical ophthalmologic exam is required to confirm or rule out evidence of intraocular muscle entrapment.

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81yearold woman fell from stairsIntraorbital fat herniation (green arrow) through the defect in the floor of the left orbit. The inferior rectus (blue arrow) is far from the site of fracture. 3D image shows intact orbital rim (red arrows) indicative of ‘pure’ blowout fracture. O = Optic nerve, H = Hemosinus

Orbital Blowout Fractures

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Orbital Fractures

• Blowin fractures– Bone is displaced into the orbit, intraorbital volume is decreased– May involve the roof, floor, and medial or lateral walls of the orbit– If orbital rim is intact = ‘pure’ blowin fractures– Clinical

• Exophthalmos (due to decreased orbital volume)• Decreased visual acuity (eyeball trauma, optic neuropathy, fracture of

optic canal)

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Orbital Blowin Fractures

80yearold man fell onto his face.Fractures of the floor of the left orbit (red arrow) displace superiorly into the orbit. The medial rectus muscle (blue arrows) is pushed upward by the fracture fragment. Intraorbital volume is further decreased by retroorbital hematoma (blue star).H = Hemosinus

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Orbital Fractures

• Orbital floor fractures– Most common portion of orbit to sustain a fracture– Usually associated with other complex midface fractures (ZMC,

LeFort II and LeFort III fractures)– Can be linear, comminuted, or segmental– Herniation of intraorbital contents

• Best seen in coronal projection• What determines chance of herniation, entrapment?

– Size of fragment, degree of depression• Inferior rectus muscle can be free, hooked, or entrapped

– Indications for surgery• Involvement > 50% of the floor, combined floor and medial wall fx with

soft tissue herniation, significant enophthalmos (> 2mm), significant diplopia

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Orbital Fractures

• Medial wall fractures– Usually associated with other complex midface fractures– Risk of medial rectus herniation (either hooked or entrapped)

relatively rare• Orbital roof fractures

– Risk of brain herniation into the orbit (better seen with coronal reformatted CT or MRI)

• Orbital apex fractures– Emergent surgical cases if there is radiologic and clinical

evidence of optic nerve impingement– May be associated with blindness– May be associated with carotid artery injury (cavernous portion)

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Orbital Fractures

• Soft tissue injuries of the orbit– Eyeball rupture

• Usually there is extrusion of vitreous (normal intraocular pressure is higher than intraorbital pressure) leading to ‘flat tire’ sign and ‘deepening’ of anterior chamber sign seen in CT

– Lens injury: subluxation, dislocation, traumatic cataract• Zonular fibers hold lens in place to ciliary muscle. If torn (partial or

complete), subluxation or dislocation occurs• Traumatic cataract (acute lens edema): affected lens has density 30HU

less than normal side– Intraorbital hemorrhage– Intraorbital foreign body

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21yearold man was assaulted.Right globe rupture is evident by flattening of the posterior wall of the globe “flat tire sign” (red arrow) and narrowing of the space between cornea and lens “deepening of anterior chamber” (red line). = Vitreous hemorrhage

Globe Rupture and Vitreous Hemorrhage

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Hemorrhage: Preseptal, Vitreous and Choroidal Preseptal hemorrhage = bleeding in the space anterior to the globe (green arrows, line)Vitreous hemorrhage = bleeding in the posterior chamber of the globe (red star), usually making ‘obtuse’ angle with the surrounding vitreousChoroidal hemorrhage = bleeding in the choroid (white stars) along the wall of the globeBlue arrows represent subcutaneous edema/hemorrhage.

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60yearold man was found down.Traumatic left lens dislocation (red arrow) is noted. Dislocation occurs due to tear of zonular fibers normally surrounding the lens. Blue arrows point to normal lens at the locations of zonular fiber attachment. The patient also has diffuse subarachnoid hemorrhage (red stars) and multiple facial fractures.

Traumatic Lens Dislocation

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Zygomatic Fractures

• Two types of zygomatic fractures– Zygomatic complex fracture– Isolated zygomatic arch fracture

• Relevant anatomy– Malar eminence = surface anatomy of the

body of zygoma– Zygomatic fractures can cause limitation

of mandibular motion, especially when the fractures are depressed

• Masseter muscle arises from zygomatic arch• Coronoid process is located underneath the

zygomatic arch

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Zygomatic Fractures

• Zygomatic complex fractures – AKA ZMC fracture, trimalar fracture, malar eminence fracture– Tripod fracture is a misnomer (zygoma actually has 2 attachments

to cranium and 2 to maxilla)– Principal lines involve 3 components

• Orbital process of zygoma • Inferior rim of orbit• Zygomatic arch

– Main fragment is zygoma, which has become separated from its three areas of attachment

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Zygomatic Fractures

• Zygomatic complex fractures– Fractures almost invariably traverse the infraorbital nerve foramen

(located in the orbital floor), causing impaired sensation of the cheek and a portion of the upper lip. However in majority of cases, the nerve is usually intact

– Pertinent radiologic information• Alignment of zygoma (depressed, rotated)• Lateral orbital wall alignment (posterior relationship of zygoma and

sphenoid bones)– Angulation of the wall results in increased orbital volume and enophthalmos

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Zygomatic Fractures

• Isolated zygomatic arch fracture– Etiology: direct blow by small object – Commonly consists of 3 fractures:

• One at each extremity• Third in the center with depression of fracture fragment

– Limited motion of mandible may occur if the fracture impinges on coronoid process or simply because the masseter muscle arises from zygomatic arch

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Zygomatic Complex Fractures

60yearold man fell onto the left cheek.Axial and coronal reformatted CT images show typical left ZMC fractures: anterior/posterior walls of maxillary sinus including rim (red arrows), zygomatic arch (green arrow), and orbital process of zygoma (blue arrow). Left orbital floor ‘blowout’ fracture with intraorbital fat herniation is seen in coronal image. Orbital floor fracture is commonly associated with ZMC fractures.

H = Hemosinus, = Soft tissue emphysema due to communication with fractured sinus

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Zygomatic Complex Fractures

Same patient as in previous page

3D image shows all components of left ZMC fractures including the inferior orbital rim (red arrows), zygomaticofrontal separation (blue arrow), zygomatic arch (green arrow).

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Isolated Zygomatic Arch Fractures

23yearold man was punched by a lefthanded.Classic zygomatic arch fractures occur in three sites along the arch. The middle fracture causes fracture fragment depression. The depressed fragments impinge on masseter muscle and can limit jaw movement.

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• The information provided in this presentation…– Does not represent the official statements or views of the Thai

Association of Emergency Medicine. – Is intended to be used as educational purposes only. – Is designed to assist emergency practitioners in providing

appropriate radiologic care for patients. – Is flexible and not intended, nor should they be used to establish a

legal standard of care.

imaging of facial trauma part 2

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