Inferosuperior Zygomatic Arch X-Ray: Positioning & Jug-Handle Notes
The Inferosuperior Projection of the Zygomatic Arches X-Ray (commonly referred to as the “Jug-Handle” View or Tangential Zygomatic Arch Projection) is a specialized, low-exposure axial view designed to project the delicate, slender zygomatic arches free of overlying facial and cranial bone superimposition.
It includes two primary modalities:
- Bilateral Inferosuperior (SMV for Zygomatic Arches): Demonstrates both zygomatic arches simultaneously for side-by-side comparative symmetry.
- Unilateral Tangential (Oblique Inferosuperior): Tailored for depressed/flat zygomatic arches or patients with flat cheekbones who cannot project the arch clear of the skull on a standard SMV.
1. Clinical Indications & Contraindications
Detailed Indications:
- Zygomatic Arch Trauma & Fractures:
- Detection of isolated “V-shaped” or three-point depressed fractures of the zygomatic arch (direct side-impact blows).
- Assessment of medial or lateral bone fragment displacement and impingement onto the temporalis muscle or coronoid process of the mandible.
- Component of ZMC / Tripod Fractures: Evaluation of the posterior horizontal component of a Zygomaticomaxillary Complex (ZMC) fracture.
- Trismus & Mechanical Mandibular Block: Evaluation of severe difficulty in mouth opening caused when a depressed zygomatic arch physically blocks the movement of the mandibular coronoid process.
- Pre- & Post-Operative Verification: Confirmation of arch elevation following Gillies approach or hook reduction procedures.
- Bone Tumors & Fibrous Dysplasia: Identifying osteomas, ossifying fibromas, or expansile cortical lesions of the zygoma.
Contraindications & Limitations:
- Unstable / Unconfirmed Cervical Spine Injury: Absolute contraindication for neck hyperextension. Standard positioning must never be attempted; use an AP Axial (Modified Towne / 30⁰ Caudad) view with the patient strictly supine instead.
- Severe Vertebrobasilar Insufficiency / Elderly Kyphosis: Extreme extension can precipitate severe dizziness, syncope, or neck injury.
2. Technical Factors & Exposure Physics
Because the zygomatic arches are thin, superficial bony bridges surrounded by soft tissue and air, using standard skull/base exposure will completely burn them out. Exposure factors must be substantially reduced compared to a standard skull SMV.
| Parameter | Bilateral SMV Arch Technique | Unilateral Tangential Technique | Radiographic Rationale |
| Patient Posture | Erect (Seated) or Supine | Erect (Seated) or Supine | Erect allows maximal neck extension |
| Image Receptor (IR) | 24 x 30 cm (Landscape/Crosswise) | 18 × 24 cm (Portrait) | Captures bilateral spread vs. isolated arch |
| SID | 100 to 115 cm ( 40 to 44 inches) | 100 to 115 cm ( 40 to 44 inches) | Maintains geometric resolution |
| Grid Usage | Grid (focused 8: 1) or Non-Grid | Grid (focused 8: 1) or Non-Grid | Clean scatter; tabletop used for thin patients |
| Tube Potential (kVp) | 65 – 70 kVp (Low) | 60 – 68 kVp (VeryLow) | High-contrast resolution; avoids over-penetration |
| mAs Range | 8 – 15 mAs (≈ 50%of Skull Base) | 6- 10 mAs(Reduced) | Low exposure prevents burning out thin cortical rims |
| Focal Spot | Small (0.6 mm) | Small (0.6 mm) | Critical for resolving non-displaced hairline fractures |
| Breathing | Suspended respiration | Suspended respiration | Eliminates respiratory and swallowing motion |
3. Step-by-Step Patient & Part Positioning
A. Bilateral Inferosuperior Method (Standard Jug-Handle)
SMV Zygomatic Arches: Patient Positioning
Bilateral Jug-Handle View
[ Vertical Bucky Surface / Vertex on IR ]
Top of cranial vault flat against cassette
Top of cranial vault flat against cassette
▲
Vertex Resting on IR (Neck Hyper-extended)
(Elevates mandibular symphysis clear of arches)
(Elevates mandibular symphysis clear of arches)
IOML // Image Receptor (Parallel)
(Infraorbitomeatal line strictly parallel to IR)
(Infraorbitomeatal line strictly parallel to IR)
Mid-Sagittal Plane (MSP) ⟂ IR (90°)
(Zero rotation ensures bilateral symmetry)
(Zero rotation ensures bilateral symmetry)
▲
Central Ray: ⟂ IOML (Perpendicular)
Enters 1″ (2.5 cm) Inferior to Mandibular Symphysis
Enters 1″ (2.5 cm) Inferior to Mandibular Symphysis
1
IOML Parallel (// IR)
Neck is hyper-extended until the infraorbitomeatal line is parallel to the plane of the image receptor.
2
CR Centering (1″ below Mentum)
Direct the perpendicular beam midway between zygomatic arches, entering 1 inch below the mandibular symphysis.
3
MSP Perpendicular (90°)
Mid-sagittal plane is centered perpendicular to prevent asymmetric overlap of arches on cranial anatomy.
4
Low Exposure Factors
Use lower mAs/kVp technique compared to routine cranial SMV to prevent burnout of thin zygomatic arches.
- Patient Posture: Seat the patient at the vertical Bucky with their back away from the board.
- Head Hyperextension: Extend the patient’s neck backward until the vertex of the skull rests against the center of the IR.
- Reference Line Alignment:
- Infraorbitomeatal Line (IOML): Must be placed strictly parallel to the plane of the image receptor.
- Mid-Sagittal Plane (MSP): Must remain strictly perpendicular to the midline of the IR (zero head rotation/tilt).
- Central Ray (CR):
- Perpendicular to the IOML.
- Directed to enter the midline of the throat/neck, approximately 2.5cm (1 inch) posterior to the mandibular symphysis (mentum), exiting at the vertex midway between the zygomatic arches.
B. Unilateral Tangential Method (Oblique Inferosuperior — For Depressed Arches)
When an arch is flat or depressed into the temporal fossa, a standard SMV will superimpose the parietal bone over the arch. The tangential technique isolates that single arch:
3-Step Tangential Positioning Rule (Unilateral Zygomatic Arch)
- Neck Extension: Hyperextend the patient’s neck until the Infraorbitomeatal Line (IOML) is positioned strictly parallel to the plane of the image receptor (IR).
- Head Rotation: Rotate the head 15⁰ toward the side of interest (affected side).
- Head Tilt: Tilt the top of the head 15⁰ away from the side of interest (unaffected side).
- Central Ray (CR): Direct the Central Ray perpendicular to the IOML and center it directly over the affected zygomatic arch (approximately 2.5 cm or 1 inch posterior to the outer canthus of the eye).
- Clinical Objective: This specific combination isolates a flat or depressed zygomatic arch, projecting it completely clear of superimposition from the parietal bone, cranial vault, and mandibular ramus.
- Central Ray (CR): Directed perpendicular to the IOML and centered directly over the affected zygomatic arch (2.5 cm posterior to the outer canthus).
4. Positioning Errors & Radiographic Signs
| Error Type | Radiographic Sign on Film | Clinical Impact | Correction |
| Under-Extension (Neck not extended enough) | Mandibular symphysis/body superimposes over and obscures the anterior zygomatic arches. | Obscures anterior arch fractures and ZMC joints. | Extend neck further until IOML is strictly parallel to IR. |
| Over-Penetration (Standard skull kVp/mAs used) | The zygomatic arches are completely burned out (radiolucent void). | Fails to detect cortical integrity or fractures. | Reduce mAs by 50% and lower kVp to 65-70 kVp. |
| Head Rotation (in Bilateral view) | One zygomatic arch is projected wide; the other is superimposed over the lateral skull wall. | Creates false asymmetry mimicking arch depression. | Realign the Mid-Sagittal Plane (MSP) perpendicular to the IR. |
| Incorrect Angle in Tangential View | Parietal bone or mandibular ramus overlaps the isolated arch. | Total failure of tangential projection. | Strictly maintain the 15⁰ rotate toward / 15⁰ tilt away rule. |
5. Radiographic Anatomy & Quality Evaluation Criteria
SMV Zygomatic Arches: Anatomical Evaluation
Jug-Handle Profile
Bilateral Zygomatic Arches Free of Superimposition
1
Bilateral Arch Clearance
Both zygomatic arches are projected laterally without superimposition on the parietal bones or mandible.
2
Mandibular Symphysis Projection
Chin and symphysis are hyper-extended anteriorly, preventing overlap across the temporal and zygomatic bones.
3
Zero Cranial Tilt & Rotation
Symmetric distance from arches to lateral cranial cortex confirms precise MSP perpendicularity.
4
Optimal Soft-Tissue Exposure
Low-contrast technical factors prevent burnout of the delicate zygomatic temporal processes.
- Arch Clearance (Primary Hallmark): Both zygomatic arches are projected symmetrically and laterally (“jug handles”), completely free of superimposition from the mandible, parietal bones, or maxilla.
- Cortical & Soft Tissue Balance: The delicate cortical borders of the temporal process of the zygomatic bone and the zygomatic process of the temporal bone are sharply visible without burnout.
- Coronoid Relationship: Clear space demonstrable between the zygomatic arch and the coronoid process of the mandible (ruling out mechanical impingement/trismus).
- Symmetry (Bilateral View): Equal lateral projection distance from the outer calvarial margin to the arch apex on both sides.
