imaging of facial trauma part 3 1

Imaging of Facial Trauma Part 3: Pathology

(Nasal, NOE, Frontal, Orbital Fractures) Rathachai Kaewlai, MD

www.RadiologyInThai.com

Created: January 2007

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Outline

Facial and mandibular fractures Nasal fractures Naso-orbital-ethmoidal fractures Frontal sinus fractures Orbital fractures Zygomatic fractures Maxillary fractures Mandibular fractures

Imaging approach

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Next presentation

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 fracture (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 severe with flattening of nose, septum

Can be a part of more complicated fx such as naso-orbital-ethmoidal (NOE) 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 radiography Plain film may miss up to nearly half of the patients with nasal fractures Nasal bone x-ray:

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 x-ray

Presence of telecanthus should prompt CT workup

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Nasal Fractures, frontal blow

39-yo-man was punched from the front

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

N = nasal bone M = Frontal process of maxilla Black arrow = Intact nasomaxillary suture

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33-yo-man was punched by a right-handed person

S = Bony nasal septum E = Ethmoid sinus Sp = Sphenoid sinus = Orbital emphysema (in this case from associated maxillary sinus fractures)

Nasal Septum Fractures

Fractures of the left frontal process of maxilla (red arrow) and the right nasal bone (green arrow) are noted. A long arrow indicates a fracture of the bony nasal septum. The fractures are displaced to the right, indicating the force of impact from the left. The right-handed person hit the left side of the nose of the victim.

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67-yo-man involved in a motor vehicle collision

S = Bony nasal septum E = Ethmoid sinus Blue arrows = Frontal process of maxilla = Orbital emphysema

Nasal Septum Fractures

Deformity of the nose pointing toward the left. There is angulation of the cartilagenous portion of the nasal septum (red arrows) and blood in the nasal cavity. The patient also had orbital floor fractures (not shown) with orbital emphysema (star).

Naso-orbital-ethmoidal (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

Therefore, NOE fractures can be related to many significant surrounding structures

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Relevant anatomy of 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 one-half of interpupillary distance

Clinically, the most obvious deformity is loss of nasal projection in profile and apparent telecanthus

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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

21-yo-man was assaulted

E = Ethmoid M = Maxillary sinus Sp = 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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D C 3D 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) are shown. Small images on right lower corners represent normal anatomy in the same projections. 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 are located.

Frontal Sinus Fractures

Etiology: motor vehicle accidents (most common), followed by high-impact 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 table, posterior table, or both

Appearance: linear, comminuted, depressed or nondisplaced

Isolated anterior table fracture is most common

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Relevant anatomy Frontal sinus first appear 6-8yrs, fully pneumatized in adolescence.

It can be asymmetric and partially pneumatized in up to 20% of population

Frontal sinuses drain via either nasofrontal duct located posteriomedially in the sinus 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 table - cosmetic deformity Posterior table fx with gross CSF leak, more than one table width

displacement

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 table fractures (red arrows) with hemosinus. Intact posterior table (blue arrow). This type of depressed fracture causes cosmetic deformity Below: 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 confirmed. 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.

Orbital Fractures

Plain radiography has a false negative rate of 7-30%

CT in axial, and coronal planes are essential to determine presence of fractures and status of intraocular muscles 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, retro-orbital hematoma

Two main types

Blow-out fractures Blow-in 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’ blow-out fracture (classic fx)

Up to 30% have ocular injury

Two proposed mechanisms 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) can be obscured due to swelling

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Orbital Fractures

Blowout fractures Image interpretation special attention to

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 24-72 hours to minimize motility problem

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Orbital Blowout Fractures

Middle age patient involved in motor vehicle accident

Coronal images (in bone and soft tissue windows) shows 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.

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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81-year-old woman fell from stairs Intraorbital 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’ blow-out fracture.

O = Optic nerve, H = Hemosinus

Orbital Blowout Fractures

Orbital Fractures

Blow-in 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’ blow-in fractures

Clinical

Exophthalmos (due to decreased orbital volume)

Decreased visual acuity (eyeball trauma, optic neuropathy, fracture of optic canal)

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Orbital Blow-in Fractures

80-year-old 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

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 CT signs ‘flat tire’ sign and ‘deepening’ of anterior chamber

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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21-year-old 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 vitreous Choroidal hemorrhage = bleeding in the choroid (white stars) along the wall of the globe Blue arrows represent subcutaneous edema/hemorrhage.

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60-year-old 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 with presumed locations of zonular fiber attachment. The patient also has diffuse subarachnoid hemorrhage (red stars) and multiple facial fractures.

Traumatic Lens Dislocation

The information provided in this presentation… 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.

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imaging of facial trauma part 3 1

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