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Infraorbital margin

The infraorbital margin (infraorbital rim) is the inferior bony boundary of the orbit, forming a prominent facial landmark. It contributes to the structural integrity of the orbital opening and serves as an important reference point in maxillofacial anatomy, trauma assessment, and surgical planning.

It is commonly evaluated in facial fractures, orbital injuries, and cosmetic or reconstructive procedures and must be carefully assessed on imaging.

Synonyms

  • Infraorbital rim

  • Inferior orbital margin

Location

  • Forms the inferior boundary of the orbital aperture

  • Located between the maxilla medially and the zygomatic bone laterally

  • Superior to the maxillary sinus

  • Inferior to the globe and orbital contents

  • Anterior to the orbital floor

  • Lies superficial to the infraorbital canal and foramen

Anatomical components

  • Maxillary contribution:

    • Medial portion of the infraorbital margin

  • Zygomatic contribution:

    • Lateral portion of the infraorbital margin

  • Adjacent landmarks:

    • Infraorbital foramen (inferior and medial to the margin)

    • Zygomaticomaxillary suture (laterally)

  • Overlying soft tissues:

    • Skin

    • Subcutaneous tissue

    • Orbicularis oculi muscle

Relations

Superiorly:

  • Orbital contents (globe, inferior rectus muscle, orbital fat)

Inferiorly:

  • Anterior wall of the maxillary sinus

  • Cheek soft tissues

Medially:

  • Maxilla

  • Nasolacrimal region

Laterally:

  • Zygomatic bone

  • Zygomaticomaxillary suture

Posteriorly:

  • Orbital floor

  • Infraorbital canal

X-ray appearance

Facial bone radiographs (Waters / occipitomental view):

  • Infraorbital margin: Smooth, curvilinear radiopaque line forming the inferior orbital rim

  • Continuity: Symmetric and uninterrupted

  • Comparison: Assessed bilaterally for asymmetry

  • Adjacent sinus: Maxillary sinus seen inferior to the rim

CT appearance

Non-contrast CT:

  • Bone cortex: Well-defined hyperdense bony rim

  • Contour: Smooth and continuous

  • Relationship: Clearly demarcated from orbital floor and maxillary sinus roof

Post-contrast CT:

  • Bone: No enhancement

  • Adjacent soft tissues: Normal enhancement patterns of orbital and facial structures

3D CT VRT appearance

Volume-rendered technique (VRT):

  • Infraorbital margin: Clearly visualized curved inferior orbital rim

  • Symmetry: Bilateral comparison easily performed

  • Surface anatomy: Smooth contour without defects

  • Clinical utility: Excellent for facial bone assessment and surgical planning

MRI appearance

T1-weighted images:

  • Bone cortex: Low signal intensity

  • Marrow (adjacent bones): Intermediate signal

  • Orbital fat: High signal superior to the margin

T2-weighted images:

  • Bone: Low signal

  • Orbital soft tissues: Intermediate-to-high signal

  • Maxillary sinus air: Signal void

CT VRT 3D image

Infraorbital margin

X-Ray image

x ray Infraorbital margin