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Head

Facial Bones

Anatomy

Students should be able to identify the following structures on themselves, the patient or radiographic images:

  • Zygoma / zygomatic arch
  • Maxilla (body, alveolar process, anterior nasal spine)
  • Nasal bones & nasal septum (vomer and perpendicular plate of ethmoid)
  • Orbital margins / floors / rims
  • Inferior orbital rim, orbital floor (important in blow-out fracture)
  • Mandible (body, rami, condyles, symphysis)
  • Pterygomaxillary region, infraorbital foramen

Topographic Lines / Reference Planes Used:

  • Orbitomeatal line (OML) — often used in positioning for Waters/OM projection.
  • Infraorbitomeatal line (IOML) — alternative baseline when OML cannot be aligned.
  • Midsagittal plane (MSP) — must be ⟂ IR to avoid rotation artifacts.
  • Interpupillary line (IPL) — helps ensure no tilt in lateral facial bones views.
  • Acanthiomeatal line (AML) — used in reverse Waters / acanthioparietal trauma views.

Routine Projections (ARRT Required)

Lateral Facial Bones – Right or Left

CR Location & Positioning

  • SID: 40″ (102 cm)
  • Patient position: Erect or recumbent semiprone, lateral side of interest against IR.
  • Adjustments:
    • MSP parallel to IR.
    • IPL perpendicular to IR.
    • IOML perpendicular to front edge of IR.
    • Oblique body slightly for comfort if erect.
  • CR: Perpendicular to zygoma (midway between outer canthus and EAM).
  • Pt. Instructions: Suspend respiration.
  • Exposure:  65–80 kV.

Evaluation Criteria

  • Coverage (what anatomy must be included and how you verify it’s complete): Entire facial bone region from orbital roofs to mandible, including zygoma.
  • Rotation checks (how symmetry or alignment tells you if positioning is correct):
    • No rotation → mandibular rami and greater wings of sphenoid superimposed.
    • No tilt → orbital roofs superimposed.
  • Motion checks (how sharpness confirms patient cooperation/exposure timing): Sharp bony margins.
  • Technique checks (what contrast, density, soft tissue visibility, and artifacts to look for): Adequate contrast/density to visualize maxillary and orbital detail.

Parietoacanthial (Waters Method) Facial Bones

CR Location & Positioning

  • SID: 40″ (102 cm)
  • Patient position: Erect (preferred) or prone. Chin against IR.
  • Adjustments:
    • MML perpendicular to IR → OML forms ~37° angle.
    • MSP perpendicular to IR, no rotation/tilt.
  • CR: Perpendicular to IR, exiting at acanthion.
  • Pt. Instructions: Suspend respiration.
  • Exposure:  70–85 kV.

Evaluation Criteria

  • Coverage: IOMs, maxillae, nasal septum, zygomatic bones, anterior nasal spine.
  • Rotation checks: Equal distance from lateral orbital margins to cranial cortex.
  • Motion checks: Sharp bony margins.
  • Technique checks: Petrous ridges projected just inferior to maxillary sinuses; sufficient density for orbital and maxillary detail.

Clinical Tip:
If patient cannot extend the neck enough to place MML perpendicular, accept a slightly steeper OML angle but confirm that petrous ridges fall just below maxillary sinuses.

PA Axial (Caldwell Method) Facial Bones

CR Location & Positioning

  • SID: 40″ (102 cm)
  • Patient position: Erect (preferred) or prone. Forehead and nose against IR.
  • Adjustments: OML perpendicular to IR; MSP perpendicular.
  • CR: 15° caudad to exit at nasion. (30° caudad if orbital floors are area of interest.)
  • Pt. Instructions: Suspend respiration.
  • Exposure: 70–85 kV.

Evaluation Criteria

  • Coverage: Orbital rim, maxillae, nasal septum, zygomatic bones, anterior nasal spine.
  • Rotation checks: Equal distance midlateral orbital margin to lateral skull cortex; symmetric superior orbital fissures.
  • Motion checks: Sharp bony margins.
  • Technique checks:
    • 15° caudad → petrous ridges in lower 1/3 of orbits.
    • 30° caudad → petrous ridges below IOM, better orbital floor view.

Clinical Tip:
If orbital floors are primary concern, use the 30° caudal angle for optimal orbital visualization.

Modified Parietoacanthial Facial Bones (Modified Waters Method)

CR Location & Positioning

  • SID: 40″ (102 cm)
  • Patient position: Erect (preferred) or prone. Chin and nose against IR.
  • Adjustments: LML perpendicular; OML forms ~55° with IR.
  • CR: Perpendicular, exiting at the acanthion.
  • Pt. Instructions: Suspend respiration.
  • Exposure:  70–85 kV.

Evaluation Criteria

  • Coverage: Orbital floors perpendicular to IR; orbital rims visualized with minimal distortion.
  • Rotation checks: Equal distance midlateral orbital margin to lateral cranial cortex.
  • Motion checks: Sharp bony margins.
  • Technique checks: Petrous ridges in lower half of maxillary sinuses, below IOMs.

Clinical Tip:
This view is particularly useful for “blowout” fractures—orbital floor is demonstrated without superimposition.

Supplemental Projections

Acanthioparietal Projection (Reverse Waters Method)

CR Location & Positioning

  • SID: 40 inches (102 cm)
  • Patient position: Supine, usually immobilized on backboard or table.
  • Adjustments: Do not move head/neck. Align CR cephalad, parallel to MML (mentomeatal line).
  • CR: Directed cephalad to acanthion, parallel to MML. Center IR to projected CR.
  • Pt. Instructions: Remain still; no movement of head/neck.
  • Exposure: Suspend respiration.

Evaluation Criteria

  • Coverage: Maxillae, maxillary sinuses, zygomatic arches, nasal septum, and orbits above petrous ridges.
  • Rotation checks: Equal distance from midlateral orbital margins to cranial cortex.
  • Motion checks: Sharp bony margins; no motion blur.
  • Technique checks: Contrast and brightness sufficient to demonstrate maxillary region and orbital structures.
  • Clinical aim: Demonstrates facial bone structures and maxillary sinuses free of superimposition by petrous ridges.

Modified Acanthioparietal Projection (Modified Reverse Waters Method)

CR Location & Positioning

  • SID: 40 inches (102 cm)
  • Patient position: Supine, immobilized.
  • Adjustments: Do not manipulate head/neck. Align CR cephalad, parallel to LML (lips–meatal line).
  • CR: Directed cephalad to acanthion, parallel to LML. Center IR to projected CR.
  • Pt. Instructions: Remain still.
  • Exposure: Suspend respiration.

Evaluation Criteria

  • Coverage: Orbital floors and rims, maxillae, nasal septum.
  • Rotation checks: Equal distance from lateral orbital margins to cranial cortex.
  • Motion checks: Sharp bony detail throughout.
  • Technique checks: Petrous ridges projected into midmaxillary sinus region, below orbital rims.
  • Clinical aim: Best for demonstrating orbital floor fractures (blowout) and orbital rim integrity.

Trauma Lateral Facial Bones (Horizontal Beam)

CR Location & Positioning

  • SID: 40 inches (102 cm)
  • Patient position: Supine; immobilized on backboard.
  • Adjustments: IR placed vertically at side of head, closest to area of interest.
  • CR: Horizontal beam, perpendicular to IR, centered to zygoma (midway between outer canthus and EAM).
  • Pt. Instructions: Remain still.
  • Exposure: Suspend respiration.

Evaluation Criteria

  • Coverage: Superimposed facial bones, zygomatic arch, mandible, orbital roofs, sphenoid wings.
  • Rotation checks: Superimposition of mandibular rami and orbital roofs.
  • Motion checks: Crisp margins of facial bones.
  • Technique checks: Adequate contrast to show facial structures and soft tissue detail.
  • Clinical aim: Detects fractures, foreign bodies, and air-fluid levels (especially sphenoid sinus, useful for basal skull fracture assessment).

Facial Bones – Quick Reference Table

Projection CR Location & Angle Patient Position Key Evaluation Points
Lateral Perpendicular to zygoma (midway between outer canthus & EAM) Erect or recumbent, side of interest closest to IR; MSP ∥ IR; IPL ⟂ IR; IOML ⟂ front edge of IR • Facial bones superimposed
• Mandibular rami & orbital roofs aligned (no rotation/tilt)
• Sharp margins, zygoma centered
Parietoacanthial (Waters) Perpendicular, exiting at acanthion Erect preferred; chin against IR; MML ⟂ IR (OML ~37° to IR); MSP ⟂ IR • Petrous ridges just below maxillary sinuses
• IOMs, maxillae, zygomas, nasal septum included
• Equal orbital margins (no rotation)
• Sharp bone detail
PA Axial (Caldwell) 15° caudad to exit nasion (30° if orbital floors) Erect preferred; forehead & nose on IR; OML ⟂ IR; MSP ⟂ IR • 15° → petrous ridges in lower 1/3 of orbits
• 30° → petrous ridges below IOMs, orbital floors better seen
• Symmetry of orbits and superior orbital fissures
Modified Waters (Parietoacanthial) Perpendicular, exiting at acanthion Erect preferred; chin & nose on IR; LML ⟂ IR (OML ~55° to IR); MSP ⟂ IR • Orbital floors seen with minimal distortion
• Petrous ridges in lower ½ of maxillary sinuses
• Equal orbital margins (no rotation)
• Best for orbital “blowout” fractures

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Hows & Whys of Facial Bone Radiography

Anatomy

  • How many facial bones are there?
    There are 14.
  • What are the facial bones?
    Two maxillae, two palatines, two zygomatics, two lacrimals, two nasals, two inferior nasal conchae, the vomer, and the mandible.
  • What bones make up the hard palate?
    The palatine processes of the maxillae and the horizontal plates of the palatine bones.
  • What bones form the zygomatic arch?
    The temporal bone and the zygomatic bone.
  • What bones form the nasal septum?
    The vomer and the perpendicular plate of the ethmoid bone.
  • What three bones form the orbital rim (orbital margin)?
    The frontal, zygomatic, and maxillary bones.
  • What is another name for the nasal conchae?
    The turbinates.
  • What is the “antrum of Highmore”?
    The maxillary sinus.
  • What facial bone lies between the frontal and maxillary bones to form the medial border of the orbit?
    The lacrimal bone.
  • The petrous portions are located in what bones?
    The temporal bones.

Positioning

  • What are the routine projections for the facial bones?
    Lateral, Parietoacanthial (Waters), and PA Axial (Caldwell).
  • Which projection best demonstrates the zygomatic arches?
    The Waters projection, with the chin extended, projects the arches clear of the petrous ridges.
  • Which projection best demonstrates the orbital floors?
    The Modified Waters projection — it brings the orbital floors perpendicular to the IR, minimizing distortion.
  • Which projection best demonstrates the nasal septum?
    The Waters projection shows it in profile without superimposition of the petrous ridges.
  • Which projection best demonstrates facial bone detail with minimal distortion?
    The Caldwell projection, which projects the petrous ridges into the lower third of the orbits.
  • When would a Reverse Waters projection be indicated?
    For trauma or when the patient cannot be positioned prone or upright.
  • Why is the erect position preferred for the Modified Waters projection?
    It allows visualization of air-fluid levels in the sinuses, which is important in trauma or sinus pathology.
  • Why is the chin extended for the Waters projection?
    To project the petrous ridges just below the maxillary sinuses, giving an unobstructed view of the midface.
  • Why is the CR angled 15° caudad for the Caldwell projection?
    To place the petrous ridges in the lower third of the orbits, preventing them from obscuring orbital and facial structures.
  • Why do you position the interpupillary line (IPL) perpendicular to the IR in the Lateral projection?
    To prevent tilt, ensuring orbital roofs and mandibular rami are superimposed.
  • Why is the lateral projection important in the facial bone series?
    It provides a baseline view of overall facial symmetry and can show fractures along the zygoma and orbital margins.
  • Why is a horizontal beam lateral essential in trauma cases?
    To detect air-fluid levels in the sphenoid sinus, which may indicate a basal skull fracture.
  • Why must cervical spine injury be ruled out before adjusting the head or neck?
    Manipulating the head or neck before clearing the c-spine risks worsening a spinal injury.
  • Why do you align the midsagittal plane (MSP) parallel to the IR in the Lateral projection?
    To avoid rotation, so mandibular rami and sphenoid wings are superimposed.
  • Why do you position the MSP perpendicular to the IR for the Waters projection?
    To ensure both sides of the orbital margins are symmetrical and free of rotation.
  • Why do you extend the chin for the Waters projection?
    To project the petrous ridges below the maxillary sinuses, opening the midface anatomy.
  • Why must the chin be tucked for the Caldwell projection?
    To prevent the petrous ridges from filling the orbits and obscuring orbital structures.
  • Why do you position the MSP perpendicular to the IR for the Caldwell projection?
    To keep orbital margins equidistant from the cranial cortex, avoiding rotation.
  • Why is the Reverse Waters projection used in trauma?
    It allows visualization of the maxillae and orbits without requiring neck extension.
  • Why do you extend the chin for the Reverse Waters projection?
    To project the maxillae and orbits above the petrous ridges so midface anatomy is unobstructed.
  • Why do you align the CR parallel to the MML for the Modified Reverse Waters projection?
    To project the orbital floors and rims with minimal distortion.
  • Why is the Modified Reverse Waters sometimes preferred over the Reverse Waters?
    It projects the orbital floors and rims with less distortion, which is critical for assessing orbital “blowout” fractures.
  • In trauma cases, why is the CR angled parallel to the MML or LML instead of using patient positioning?
    Because trauma patients often cannot flex or extend their neck, the CR angle substitutes for baseline alignment.
  • Why is the acanthion the centering point for Reverse Waters methods?
    Centering at the acanthion aligns the CR through the midface structures, ensuring coverage of maxillae, orbits, and nasal region.
  • Why do you position the interpupillary line (IPL) perpendicular to the IR in the Lateral projection?
    To prevent tilt, ensuring orbital roofs and mandibular rami are superimposed.

Technique & Image Evaluation

  • How do you know the interpupillary line (IPL) was perpendicular in the Lateral projection?
    The orbital roofs and mandibular rami are superimposed without tilt.
  • How do you confirm there was no rotation on a Lateral facial bones projection?
    The mandibular rami and greater wings of the sphenoid are superimposed.
  • How do you know the MSP was perpendicular to the IR on the Waters projection?
    The orbital margins are symmetrical on both sides.
  • How do you know the chin was extended enough on the Waters projection?
    The petrous ridges are projected just below the maxillary sinuses.
  • How do you know the chin was extended enough on the Reverse Waters projection?
    The petrous ridges are projected below the maxillary sinuses and the orbits are symmetrically demonstrated.
  • How do you know the chin was tucked correctly for the Caldwell projection?
    The petrous ridges are projected into the lower third of the orbits, without obscuring orbital detail.
  • How can you confirm proper CR angulation and head position on the Caldwell projection?
    The petrous ridges are projected into the lower third of the orbits (15° caudad angle).
  • What does it mean if the petrous ridges fill the orbits on a Caldwell projection?
    The chin was not tucked enough, or the CR angle was insufficient.
  • How do you know the head was not rotated on a Caldwell projection?
    The distances from the midlateral orbital margins to the lateral cranial cortex are equal on both sides.
  • How do you confirm correct positioning on a Modified Waters projection?
    The petrous ridges are projected into the lower half of the maxillary sinuses, and the orbital rims are symmetrical.
  • How can you confirm proper CR angulation and head position on the Caldwell projection?
    The petrous ridges are projected into the lower third of the orbits (15° caudad angle).
  • How do you know the interpupillary line (IPL) was perpendicular to the IR on the trauma Lateral projection?
    The orbital roofs and mandibular rami are superimposed without tilt.

Clinical Applications

  • Which projection best demonstrates blowout fractures of the orbit?
    The Modified Waters projection, because it shows the orbital floors without distortion.
  • Which projection is preferred for tripod or Le Fort fractures?
    The Waters projection, as it clearly shows the maxillae, zygomas, and nasal structures together.
  • Which projection is used when a patient cannot be positioned for a standard Waters?
    The Reverse Waters projection — performed supine with a cephalic CR angle to mimic the chin-extended position.

 

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Radiographic Procedures Review Guide Copyright © 2025 by Carla M. Allen and Taylor M. Otto is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, except where otherwise noted.

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