Nasal Bones

Head

51 Nasal Bones

Nasal bones: Two thin bones forming the bridge of the nose.
Anterior nasal spine: Projection of the maxilla at the midline, below nasal bones.
Frontonasal suture: Junction between nasal bones and frontal bone.
Associated structures visible on images:
- Soft tissue nose
- Acanthion
- Orbits
- Zygomatic arches (malar bones)
- Frontal sinus
- Maxillary sinus
- Mandible

Clinical Indications:

CR Location & Positioning

Evaluation Criteria

Coverage: Nasal bones, anterior nasal spine, frontonasal suture, and nasal soft tissue included
Rotation checks: No rotation — nasal bones symmetric
Motion checks: Sharp bony and soft tissue margins
Technique checks: Soft tissue density sufficient to show nasal cartilage and outline of nose
Clinical aim: Detect displacement and comparison between sides

Clinical Indications:

Facial bone fractures (including nasal and maxillary), foreign bodies, inflammation

CR Location & Positioning

Evaluation Criteria

Coverage: IOMs, maxillae, nasal septum, zygomas, anterior nasal spine
Rotation checks: Equal orbital margins, nasal septum midline
Motion checks: Sharp margins of maxillae and sinuses
Technique checks: Petrous ridges just below maxillary sinuses
Clinical aim: Demonstrates bony nasal septum deviation and midface fractures

Clinical Indications:

CR Location & Positioning

SID: 40 inches
Patient position: Seated erect or prone; chin on IR
Adjustments: IR angled so GAL ⟂ IR; MSP ⟂ IR; extend chin to rest on IR
CR: Parallel to GAL, centered to nasion (skims glabella and anterior upper teeth)
Pt. Instructions: Suspend respiration
Exposure: 60–70 kV digital, nongrid

Evaluation Criteria

Coverage: Mid- and distal nasal bones with soft tissue profile; minimal superimposition of glabella/alveolar ridge
Rotation checks: Symmetry of anterior nasal spine to outer soft tissue borders
Motion checks: Sharp nasal margins
Technique checks: Correct extension/flexion — too much chin = alveolar ridge in view; too little = excess glabella in view
Clinical aim: Assess displacement in the axial plane

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Anatomy / Clinical Aim

What anatomy is best demonstrated on the lateral nasal bones?
The nasal bones, anterior nasal spine, frontonasal suture, and nasal soft tissues.
What anatomy is best demonstrated on the Waters view?
The bony nasal septum, maxillae, zygomas, and anterior nasal spine.
What anatomy is best demonstrated on the superoinferior tangential view?
The mid- and distal nasal bones and the soft tissue nose without significant superimposition.

Positioning

In the lateral projection, why must the interpupillary line (IPL) be perpendicular to the IR?
To prevent tilt, ensuring the orbital roofs and nasal bones are superimposed.
In the lateral projection, why should the infraorbitomeatal line (IOML) be parallel to the transverse axis of the IR?
To keep the head from tipping forward or backward, which would distort nasal bone detail.
Why are both lateral projections taken for nasal bones?
Because each side is positioned closest to the IR in turn, ensuring maximum detail for comparison.
For the Waters projection, why is the OML adjusted to form a 37° angle with the IR?
To bring the mentomeatal line (MML) perpendicular, projecting the petrous ridges below the maxillary sinuses and opening the midface.
Why is a horizontal beam lateral important in trauma cases involving the nasal bones?
It allows evaluation without manipulating the head or neck and demonstrates air–fluid levels if associated sinus fractures are present.
Why must cervical spine injury be ruled out before positioning for nasal bone studies?
Head or neck movement could worsen an undiagnosed spinal injury.
Why are two laterals especially important in trauma cases?
They allow comparison of displacement or depression between the right and left nasal bones.

Technique & Image Evaluation

How do you know the interpupillary line (IPL) was perpendicular on a lateral projection?
The orbital roofs and nasal bones are superimposed without vertical separation.
How do you know the IOML was parallel to the IR on a lateral projection?
The frontal sinuses and orbital roofs appear in proper vertical alignment without slanting.
How do you know the OML was angled correctly for the Waters projection?
The petrous ridges are seen just below the maxillary sinuses, and the nasal septum is clearly visible.
How do you know there was no rotation on a lateral nasal bones projection?
The anterior nasal spine and soft tissue outline are aligned without anterior/posterior separation of bilateral structures.
How do you know there was no rotation on a Waters projection?
The orbital margins and nasal septum are symmetrical side to side.
Why must close collimation be used for nasal bone studies?
To reduce scatter and improve recorded detail of the thin nasal bones and adjacent soft tissue.
How do you know the exposure factors were appropriate for nasal bones?
Bony detail of the nasal bones is visible along with surrounding soft tissues without overexposure.
Which structures should be included on a properly collimated Waters projection for nasal bones?
Nasal bones, orbits, maxillae, and anterior nasal spine.