Zygomatic Arch X-Ray Positioning: SMV & Tangential Views
The zygomatic arch is the bony bridge formed by the temporal process of the zygomatic bone and the zygomatic process of the temporal bone at the zygomaticotemporal suture. A depressed isolated arch fracture can restrict mandibular movement if it impinges on the coronoid process.
This guide describes the two established dedicated plain-film approaches: a bilateral submentovertex (SMV) projection and a unilateral oblique inferosuperior tangential projection. These are legacy or problem-solving radiographic views; for acute suspected midface injury, current ACR guidance favors CT maxillofacial without IV contrast.
Accuracy correction
The previous version incorrectly presented modified Towne and “modified Titterington” as dedicated zygomatic-arch views. The AP axial Towne is used for skull and mandible imaging, but the current ARRT radiography outline does not list it as an arch projection. No authoritative positioning source was found for a “modified Titterington” arch method, so that unsupported protocol has been removed.
Anatomy of the Zygomatic Bone
Each zygomatic bone contributes to the lateral orbital wall and orbital floor and articulates with four bones:
| Articulation | Clinical relationship |
|---|---|
| Zygomaticofrontal | At the lateral orbital rim |
| Zygomaticomaxillary | At the inferolateral orbital rim and maxillary buttress |
| Zygomaticotemporal | Forms the zygomatic arch |
| Zygomaticosphenoid | Within the lateral orbit |
The masseter arises in part from the zygomatic arch. An isolated depressed arch segment may mechanically interfere with the mandibular coronoid process and produce trismus. Because the zygoma also forms parts of the orbit, suspected zygomaticomaxillary-complex (ZMC) injury requires assessment for orbital involvement.
Fracture terminology
- Isolated zygomatic-arch fracture: may be depressed after a direct lateral blow and may cause contour deformity or trismus.
- ZMC fracture: may disrupt the zygomaticofrontal, zygomaticomaxillary, zygomaticotemporal and zygomaticosphenoid articulations. “Tetrapod” is therefore more anatomically complete than the traditional “tripod” label.
- Le Fort III: a craniofacial-dissociation pattern that includes fractures through the zygomatic arches and pterygoid plates. Classification is based on the complete fracture pattern on CT, not on one plain-film view.
Do not overcall a pattern
A ZMC injury is not reliably reduced to “three fracture lines,” and the zygoma is not necessarily a free-floating fragment. Describe the sites and displacement demonstrated on cross-sectional imaging.
Which Views Belong in a Dedicated Arch Examination?
When plain radiography is specifically requested under a local protocol, the established dedicated projections are:
- SMV (submentovertex): bilateral comparison of both arches.
- Oblique inferosuperior tangential: unilateral profile of the arch of interest.
Series composition varies by institution. A Waters view can demonstrate the zygomatic bones and other midface structures, but it is not a substitute for CT when a complex acute facial fracture is suspected.
View 1: Submentovertex (SMV) — Bilateral Zygomatic Arches
The SMV demonstrates both arches for side-to-side comparison, provided the patient can safely extend the neck.
Patient and Part Position
- Use an upright or supine setup according to equipment and patient condition.
- Align the MSP perpendicular to the IR without rotation.
- Extend the neck until the IOML is parallel to the IR; the vertex is close to or against the IR.
- Do not force the position. Stop if extension causes pain, neurologic symptoms, dizziness or instability.
⚠️ Trauma safeguard
Do not perform either conventional SMV or tangential inferosuperior positioning before cervical-spine injury has been excluded and neck movement is permitted. The tangential view is not a “minimal neck movement” substitute: it begins from the same extended-neck geometry. Maintain immobilization and use the ordered trauma imaging pathway.
Central Ray and Technique
| Parameter | Dedicated bilateral SMV |
|---|---|
| SID | 100 cm (40 in), unless the validated local protocol specifies otherwise |
| IR | Collimated to include both arches; receptor size and grid use are system/protocol dependent |
| CR direction | Perpendicular to the IOML |
| Center | MSP, midway between the zygomatic arches—approximately 4 cm (1.5 in) inferior to the mandibular symphysis |
| Exposure | Suspend respiration; use the department's technique chart rather than a universal kVp/mAs value |
Image Evaluation
- Both arches are included and demonstrated lateral to the cranial bones.
- The arches are symmetric; asymmetry can reflect rotation or true injury.
- The skull base and mandibular condyles should be symmetric when there is no rotation.
- Collimation, exposure and sharpness permit assessment of cortical continuity and depression.
View 2: Oblique Inferosuperior Tangential (Jug Handle View) — Unilateral
This projection isolates one arch. The colloquial name “jug-handle” is not standardized, so use the geometric projection name in protocols and image labels.
Common Textbook Geometry
- Begin only if the patient can safely assume the extended-neck SMV position, with the IOML approximately parallel to the IR.
- For the arch of interest, rotate the head approximately 15° toward that side.
- Tilt the chin approximately 15° away from the side of interest—not toward it.
- Direct the CR perpendicular to the IOML and center to the arch of interest.
Protocol variation
Named tangential methods and exact combinations of rotation, lateral tilt, beam angle and centering vary among positioning texts and departments. The 15°/15° setup above is one commonly taught approach, not a universal mandate. Follow the department's validated protocol and evaluate the resulting anatomy.
Technique and Evaluation
| Parameter | Oblique inferosuperior tangential |
|---|---|
| SID | 100 cm (40 in), or local protocol |
| Collimation | Tight to the unilateral arch while retaining required landmarks |
| CR | Perpendicular to the IOML, centered to the arch of interest in this commonly taught method |
| Technique | Use the equipment-specific manual technique chart if AEC chamber coverage is unreliable; do not prescribe a universal kVp/mAs |
- The entire arch of interest is included in profile with minimal superimposition.
- Cortical margins and any depression are sharply demonstrated.
- Confirm the correct side with a radiopaque marker; do not infer laterality from image orientation alone.
Why Towne and “Titterington” Were Removed
The AP axial Towne is a legitimate projection for skull anatomy and for the mandible (including condylar processes), but that does not make it a standard dedicated zygomatic-arch projection. The prior arch-specific 30°/37° recipe and claimed glabellar centering were therefore removed rather than repurposed.
No authoritative radiographic positioning reference located during this audit supported a “PA axial modified Titterington” zygomatic-arch method or its claimed 23°–38° caudal range. Technologists should not perform an unsupported named view; use the exact ordered examination and the department's approved protocol.
Positioning Summary Table
| Projection | Position | CR and center | Primary result |
|---|---|---|---|
| Bilateral SMV | Neck extended; IOML parallel and MSP perpendicular to IR | Perpendicular to IOML; MSP midway between arches, about 4 cm inferior to mandibular symphysis | Both arches for comparison |
| Unilateral oblique inferosuperior tangential | From safe SMV position; commonly rotate 15° toward and tilt chin 15° away from side of interest | Perpendicular to IOML and centered to arch in this method | Arch of interest in profile |
ARRT Scope: What the Published Outline Actually Says
The ARRT Radiography Content Specifications in effect through February 28, 2027 allot 18 scored questions to all head, spine and pelvis procedures combined. They list facial-bone projections (lateral, Waters, Caldwell and modified Waters) and mandible projections including AP axial Towne, but do not name a dedicated zygomatic-arch SMV, tangential view, Titterington method or a question count for any of them. It is therefore inaccurate to claim that ARRT “frequently tests” a particular arch view or trauma scenario.
| Keep straight | Accurate statement |
|---|---|
| SMV geometry | IOML parallel to IR; CR perpendicular to IOML; center midway between arches |
| Tangential safety | Also requires neck extension; it is not a cervical-spine-safe substitute |
| Tangential tilt | In the common 15°/15° setup, rotate toward and tilt the chin away from the side of interest |
| ZMC terminology | Four articulations may be involved; “tetrapod” is anatomically more complete than “tripod” |
| Acute midface trauma | ACR: CT maxillofacial without IV contrast is usually appropriate; listed radiography is usually not appropriate |
Common Positioning and Technique Errors
Rotation on the Bilateral SMV
Rotation produces asymmetric arches and an asymmetric skull base. Confirm the MSP is perpendicular to the IR before exposure, but do not reposition through pain or against spinal precautions.
Insufficient or Unsafe Extension
If the IOML is not parallel to the IR, the intended arch profile may be distorted or obscured. Do not force more extension merely to satisfy a landmark. If the patient cannot safely achieve the geometry, stop and consult the radiologist or ordering pathway rather than improvising a hazardous substitute.
Wrong Direction of Tangential Tilt
For the common 15°/15° method described here, rotate toward the side of interest but tilt the chin away from it. The previous version incorrectly said to tilt toward the arch.
Unvalidated Exposure Factors
There is no single correct kVp, mAs, grid or AEC rule for every detector, patient and installation. Use the department's technique chart, collimate closely, review the exposure indicator, and repeat only when the image is nondiagnostic and a repeat is clinically justified.
Indications and Modern Modality Selection
Potential clinical features include focal tenderness or flattening over the arch, trismus, malocclusion, infraorbital sensory change, periorbital findings and a palpable step. These findings require clinical assessment; they do not by themselves determine a plain-film series.
ACR acute-trauma guidance
For pain over the zygoma, zygomatic deformity, facial elongation, malocclusion or infraorbital nerve paresthesia after trauma, the ACR rates CT maxillofacial without IV contrast “Usually Appropriate” as initial imaging. In that same midface-trauma variant, chest and paranasal-sinus radiography are “Usually Not Appropriate.” CT is not contraindicated merely because a patient is pregnant; imaging choice should reflect clinical need and pregnancy policy.
Dedicated radiographs may still be used when explicitly requested for a limited question, postoperative/follow-up assessment, or where CT is unavailable, but they have limited sensitivity for the complex three-dimensional anatomy of ZMC, orbital and Le Fort injuries. Fine-cut noncontrast maxillofacial CT is the standard cross-sectional examination; 3D reconstructions can assist surgical planning but do not replace review of source images and multiplanar reconstructions.
Radiation Protection, Shielding and Pregnancy
- Justification and optimization: verify the order and patient, collimate to the required anatomy, use a validated technique chart, avoid repeats and keep dose as low as reasonably achievable while preserving diagnostic quality.
- Patient shielding: AAPM recommends discontinuing routine gonadal and fetal shielding in X-ray-based diagnostic imaging. Shields provide minimal to no benefit from internal scatter and may obscure anatomy or interfere with AEC, causing a repeat or increased output. Follow current institutional policy and never place shielding in the field.
- Pregnancy: ask and document according to facility policy. ACOG states that, with few exceptions, doses from diagnostic radiography and CT are much lower than those associated with fetal harm and needed imaging should not be withheld solely because of pregnancy. For a head examination the uterus is outside the primary beam; optimize normally and involve the radiologist/medical physicist when a patient-specific dose estimate or counseling is needed.
Sources and Audit Notes
- ACR Appropriateness Criteria®: Imaging of Facial Trauma Following Primary Survey — acute midface-trauma modality ratings.
- StatPearls/NCBI Bookshelf: Zygomatic Arch Fracture — four ZMC articulations, clinical effects and CT technique.
- AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding — routine shielding recommendation and rationale.
- ACOG Committee Opinion 723: Guidelines for Diagnostic Imaging During Pregnancy and Lactation — diagnostic ionizing-radiation risk and clinically indicated imaging.
- ARRT Examination Content Specifications and the linked Radiography specification through February 28, 2027 (PDF) — published procedure scope and question allocation.
- CE4RT: Radiographic Positioning of the Zygomatic Arch — accessible positioning reference confirming the extended-neck SMV, IOML/IR relationship and trauma caution.
Positioning note: Exact tangential geometry varies by source and local protocol. This page deliberately labels the common 15°/15° setup as one method and does not attribute it to Clark's because no exact Clark's edition and page were available for verification.
Related Articles
- Facial Bones X-Ray Positioning Guide — Waters, Caldwell, lateral, and SMV facial bone views with centering points
- Skull X-Ray Positioning Guide — Lateral, PA, Caldwell, Towne, and AP views for cranial radiography
- Mandible X-Ray Positioning Guide — PA, AP axial Towne, axiolateral oblique, and SMV mandibular views
- Trauma Radiography Principles — Modified techniques for non-ambulatory and facial trauma patients
- X-Ray Modality Page — Complete list of radiographic procedures and positioning guides