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Imaging of Facial Trauma Part 2: Introduction and Anatomy

Rathachai Kaewlai, MD

www.RadiologyInThai.com

Created: January 2007

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Outline

  Facial fracture epidemiology

  Initial management

  Imaging: CT versus radiography

  Normal anatomy

  3D

  CT (axial, coronal and sagittal planes)

  Radiography

  Biomechanics

  Types of facial fracture   Nasal bone fracture

  Naso-orbital-ethmoid fracture

  Frontal sinus fracture

  Orbital fracture

  Zygomatic fracture

  Maxillary fracture

  Mandibular fracture

  Imaging approach

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Plain Film Radiography

  Can be obtained to screen for facial injury if CT is not immediately available

  If plain film identify a fracture other than a simple nasal bone fracture, further evaluation by CT is indicated

  Multiple plain film projections are relative to ‘canthomeatal line’; an imaginary line drawn from outer canthus to external auditory meatus

  Proper positioning (of patient’s head), alignment of x-ray beam is critical for evaluation because facial skeletal anatomy is complex

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Plain Film Radiography

  Remember: plain film is a 2D image of a 3D object   Overlapping structures significantly obscure anatomic detail   This problem is solved by standard views (to minimize overlap,

allow visualization of important structures, familiarity for interpretation)

  Rule of symmetry: two sides of the face are quite symmetrical   Symmetry is usual, and asymmetry is suspect

  Multiplicity: fractures of facial bones are frequently multiple. Do not stop looking for others when see one

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Plain Film Radiography

  Facial series   Water’s view (PA view with

cephalad angulation)   Caldwell view (PA view)   Towne’s view   Lateral view   Base view

  Additional view

  Lateral view of the nasal bone (nasal technique)

  Mandible

  Oblique view, Towne’s view

  Orthopanthogram

5 Note: The lecture series are focused on CT scan

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The most comprehensive single projection display Excellent view of -  Maxilla -  Maxillary sinuses -  Zygoma -  Zygomatic arches -  Rims of orbits, esp. floor -  Nasal bones

Water’s View

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Key structures 1 = Frontal sinus 2 = Maxillary sinus 3 = Frontal process of Zygoma 4 = Body of Zygoma (malar eminence) 5 = Temporal process of Zygoma

Dotted line = zygomatico-frontal suture

Dolan’s lines of reference Line A, B, C

Water’s View

Rule: smooth, non-disrupted, same contour on both sides

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Line A -  Begins at inner surface of zygomatico-frontal suture, follows orbital surface of zygoma, maxilla, frontal process of maxilla and arch of nasal bone -  If drawn to both sides, the line is similar to lazy ‘W’ or half frame of reading glasses

Line B - Begins at lateral and inferior margin of maxilla and extends along lateral wall of maxillary sinus and inferior surface of zygomatic arch -  Ends at glenoid fossa

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Line C -  Begins at lateral and inferior margins of maxilla, extends along lateral wall of maxillary sinus and inferior surface of zygomatic arch -  Ends at glenoid fossa

“Friendly Line” -  Medial half of Line C is the anterolateral wall of the maxillary sinus. -  If it is disrupted, the possibilities of fx include 1) Isolated maxillary antrum 2) Zygomatico-maxillary complex (ZMC) 3) LeFort (unilateral or bilateral)

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Excellent view of -  Entire rim of orbit, esp. superomedial rim -  Ethmoid sinus -  Floor of orbit may be well seen in petrous bones are projected below the inferior orbital rim (not in this example)

Caldwell’s View

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Key structures 1 = Ethmoid sinuses 2 = Orbit

Line A, B, C, D = superior, lateral, inferior and medial walls of the orbit, respectively

Line E = midline nasal septum and vomer

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Rule: - Ethmoid sinuses density should be equal, darker than orbit - Smooth non-disrupted orbital walls

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Excellent view of -  Frontal sinus: anterior wall -  Maxillary sinus: anterior and posterior wall -  Sphenoid sinus -  Pterygoid plate -  Floor of anterior cranial fossa, hard palate -  Lateral rim of orbit

Lateral View

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Key structures 1 = Frontal sinus 2 = Maxillary sinus 3 = Sphenoid sinus 4 = Hard palate 5 = Anterior wall of temporal fossa Between green arrows = Pterygoid plate

Line A = Anterior wall of frontal sinus Line B = Anterior cranial fossa Line C = Anterior wall of maxillary sinus Line D = Posterior wall of maxillary sinus

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Line A - Connects anterior surface of frontal sinus and anterior surface of hard palate Line B - Connects anterior wall of temporal fossa and posterior edge of hard palate Line C - Along planum sphenoidale Line D - Along hard palate

Rule: -  Line A & B parallel -  Line C & D parallel

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Excellent view of -  Maxillary sinus: posterolateral wall -  Zygomatic arch

Towne’s View

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Key structures 1 = Zygomatic arch

Line A = Posterolateral wall of maxillary sinus

Rule: -  Smooth, non-disrupted line

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Orthopanthogram or Panorex® Key structures R = Temporomandibular joint 13 = Mandible, condyle 14 = Mandible, ramus 17 = Mandible, body 18 = Mandible, angle 19 = Mandible, coronoid process 20 = Mandible, symphysis

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Counting the teeth on Orthopanthogram or Panorex® American Dental Association (ADA) system preferred this system because you will speak same ‘language’ with dentists. Count from midline and go laterally (some individuals may not have #1, #16, #17, and #32)

Maxillary Arch ADA#1 - 8 (right), #9-16 (left) Mandibular Arch ADA#32-25 (right), #24-17 (left)

8 9

25 24

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Oblique View of Mandible Key structures R = Temporomandibular joint 13 = Mandible, condyle 14 = Mandible, ramus 17 = Mandible, body 18 = Mandible, angle 19 = Mandible, coronoid process 20 = Mandible, symphysis

Biomechanics

  LeFort described areas of relative strength within the facial skeleton   Alveolar process of maxilla

(1)

  Frontal process of maxilla (2)

  Body of zygoma or malar eminence (3)

  Line of fracture tends to avoid these areas

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Checklist for Facial Radiograph/CT

  Facial structures are quite symmetrical

  Do not stop searching when see one abnormality

  If suspect for more than simple nasal fracture, do CT

  Significant (but can be subtle) fractures

  Fracture involves the optic foramen which can cause permanent visual loss if not treated promptly

  Fracture of the posterior wall of frontal sinus requires neurosurgical evaluation and may require antibiotics prophylaxis

  Fracture/dislocation of the TMJ usually missed on initial survey. It can cause significant disability if left untreated

  Look for significant soft tissue injuries

  Globe rupture, hemorrhage 21

  To be continued in Part 2 and 3

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  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.

  Thanks, MGH Radiology, for cases I’ve seen and things I’ve learned.

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R.K.