Modified Towne’s View Zygomatic Arches: Radiographic Positioning Notes

The Modified Towne’s View (AP Axial for Zygomatic Arches) is a specialized cranial projection designed to demonstrate both zygomatic arches simultaneously in symmetry.

It serves as the primary non-invasive alternative to the Submentovertex (SMV / “Jug-Handle”) view, especially in trauma patients with cervical spine precautions or severe neck stiffness who cannot hyperextend their neck.

Modified Towne AP Axial Radiograph. Source: mr.suphachai praserdumrongchai / Getty Images

1. Clinical Indications & Contraindications

Detailed Indications:

• Bilateral Zygomatic Arch Fractures: Symmetrical comparison of medial or lateral displacement, greenstick, comminuted, or V-shaped depressed fractures of the zygomatic arches.
• Component of Zygomaticomaxillary Complex (ZMC / Tripod) Fractures: Evaluating displacement of the posterior temporal process of the zygomatic bone.
• Trauma Alternative to SMV: Indicated in polytrauma patients where hyperextension of the cervical spine is strictly contraindicated.
• Coronoid Impingement Evaluation: Assessment of whether a depressed zygomatic arch impinges onto the coronoid process of the mandible, causing trismus (inability to open the mouth).
• Bone Lesions & Post-Reduction Verification: Assessment of fibrous dysplasia, osteomas, or surgical elevation and fixation using titanium plates/wires.

Contraindications & Limitations:

• Isolated Anterior Zygoma Evaluation (Limitation): Distorts and foreshortens the anterior maxillary body and infraorbital rim. A Waters (Parietoacanthial) or Caldwell view must accompany this projection for comprehensive facial bone evaluation.

2. Technical Factors & Exposure Physics

Because the zygomatic arches are thin and superficial, exposure factors are reduced compared to a standard skull base Towne view to prevent burning out the delicate cortical bone.

3. Step-by-Step Patient & Part Positioning

              [ X-ray Tube Angled Caudad ]
                      \
                       \  30° (OML ⟂)  OR  37° (IOML ⟂)
                        ▼
                 (Nasion / Glabella Level)
                   ───────┬───────
                 /        │        \
                │   OML   │         │ ◄── OML strictly Perpendicular to IR
                │ ───────┼──────── │
                 \       │   MSP   /  ◄── Mid-Sagittal Plane Perpendicular to IR
                   ───────┴───────
                   [ Image Receptor ]

• Patient Preparation: Remove all metallic and radiopaque objects (earrings, hairpins, clips, glasses, necklaces, dentures, and hearing aids).
• Base Posture:
  • Supine (Trauma Standard): Patient lies supine on the radiographic table with the posterior skull (occiput) resting against the table surface.
  • Erect (Alternative): Patient seated or standing with the back of the head flat against the vertical Bucky.
• Alignment of Reference Lines & Planes:
  1. Mid-Sagittal Plane (MSP): Align strictly perpendicular to the midline of the grid/table (ensures zero head rotation).
  2. Orbitomeatal Line (OML): Flex the patient’s neck until the OML is perpendicular (90∘) to the image receptor.
  3. Trauma Adaptation (IOML): If the patient is immobilized in a rigid C-collar and cannot tuck the chin, ensure the Infraorbitomeatal Line (IOML) is perpendicular to the IR instead.
  4. Interpupillary Line (IPL): Must be strictly parallel to the IR surface (ensures zero lateral tilt).

4. Central Ray (CR), Tube Angle & Collimation

• CR Tube Angulation:
  • 30∘ Caudad when the OML is perpendicular to the IR.
  • 37∘ Caudad when the IOML is perpendicular to the IR (compensates for the 7∘ difference between OML and IOML).
• CR Centering / Entry Point:
  • Directed through the midline, entering at the Glabella (approximately 2.5 cm or 1 inch superior to the nasion) and passing midway between the zygomatic arches at the level of the mandibular angles.
• Collimation: Four-sided collimation adjusted tightly:
  • Superiorly: Just above the orbits/glabella.
  • Inferiorly: Below the mandibular gonions.
  • Laterally: To the outer skin borders of the zygomatic arches.

5. Positioning Errors & Radiographic Signs

6. Radiographic Anatomy & Quality Evaluation Criteria

+───────────────────────────────────────────────────────────────────────────+
|                               [ Frontal Bone ]                            |
|                                                                           |
|                  /─────────────────────────────────────\                  |
|                 │         (·) Orbits / Ethmoids (·)     │                 |
|   Zygomatic ──► │  \                                 /  │ ◄── Zygomatic   |
|     Arch        │   \                               /   │       Arch      |
|  (Projected     │    \                             /    │    (Projected   |
|   Laterally)    │     [=== Petrous Pyramids ===]   │    │     Laterally)  |
|                 │                                       │                 |
|                 │     (     [ FORAMEN MAGNUM ]     )    │                 |
|                  \     \__________________________/    /                  |
|                   \───────────────────────────────────/                   |
|                                [ Occiput ]                                |
+───────────────────────────────────────────────────────────────────────────+

• Bilateral Arch Projection (Primary Quality Hallmark): Both zygomatic arches are projected symmetrically and laterally beyond the outer margins of the mandibular rami and cranial vault.
• Symmetry:
  • Equal distance from the lateral margins of the skull vault to the outer apex of each zygomatic arch.
  • Symmetrical petrous pyramids and mandibular condyles.
• Cortical Sharpness: Clear cortical boundaries along the entire span of the temporal process of the zygoma and the zygomatic process of the temporal bone without bone burnout.
• Absence of Motion Blur: Crisp trabecular detail across adjacent facial and calvarial bones.