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Infraorbital canal

The infraorbital canal is a short osseous tunnel within the maxilla, extending anteriorly from the infraorbital groove on the orbital floor to the infraorbital foramen on the anterior surface of the maxilla. It serves as a protected conduit for the infraorbital nerve and vessels as they traverse from the orbit to the face.

The canal lies entirely within the orbital floor, inferior to the globe, and represents a key anatomical landmark in orbital, maxillofacial, and dental imaging. Its thin bony walls and close relationship to the maxillary sinus make it particularly relevant during trauma assessment and surgical planning, although only normal imaging characteristics are described here.

Synonyms

  • Infraorbital nerve canal

  • Maxillary infraorbital canal

  • Infraorbital neurovascular canal

Location and Structure

  • Origin: Posteriorly from the infraorbital groove on the inferior surface of the orbital plate of the maxilla

  • Course: Runs anteriorly and slightly inferiorly within the maxilla

  • Termination: Opens onto the facial surface as the infraorbital foramen

  • Length: Approximately 10–15 mm

  • Wall thickness: Thin cortical bone, especially inferiorly toward the maxillary sinus

Relations

  • Superiorly: Orbital contents and inferior rectus muscle

  • Inferiorly: Maxillary sinus roof

  • Medially: Nasolacrimal canal and nasal cavity structures

  • Laterally: Zygomatic process of maxilla

  • Posteriorly: Infraorbital groove

  • Anteriorly: Infraorbital foramen and facial soft tissues

Contents

  • Infraorbital nerve (continuation of the maxillary division of the trigeminal nerve, V2)

  • Infraorbital artery and vein

  • Accompanying connective tissue and fat

Function

  • Provides a protected bony passage for infraorbital neurovascular structures

  • Maintains structural integrity of the orbital floor

  • Serves as an anatomical landmark for regional anesthesia and surgical approaches

Clinical Relevance

  • Important landmark in orbital floor anatomy

  • Critical for infraorbital nerve blocks

  • Routinely assessed in facial imaging for anatomical orientation

  • Close proximity to maxillary sinus explains potential symptom referral patterns

MRI Appearance

T1-weighted images:

  • Canal walls: Low signal intensity (cortical bone)

  • Canal lumen: Intermediate signal from nerve and vessels

  • Surrounding orbital fat: Bright, clearly outlining the canal

  • Infraorbital nerve: Intermediate signal, linear structure within canal

T2-weighted images:

  • Cortical margins: Low signal

  • Neurovascular bundle: Intermediate signal, slightly brighter than on T1

  • Surrounding orbital fat: Intermediate-to-bright

  • Maxillary sinus air: Very low signal (black)

STIR:

  • Canal walls: Low signal

  • Infraorbital nerve and vessels: Intermediate-to-dark signal

  • Surrounding fat: Suppressed, allowing clear visualization of canal course

  • Sinus air: Dark

T1 Fat-Saturated Post-Contrast:

  • Infraorbital vessels: Uniform enhancement within the canal

  • Infraorbital nerve: Mild linear enhancement

  • Canal walls: No enhancement

  • Adjacent orbital soft tissues: Normal homogeneous enhancement pattern

CT Appearance

Non-Contrast CT:

  • Canal appears as a well-defined tubular bony tunnel within the maxilla

  • Cortical margins: Thin, smooth, and sharply demarcated

  • Lumen: Low attenuation relative to bone

  • Clear visualization of relationship to orbital floor and maxillary sinus

  • Best appreciated on coronal and sagittal reconstructions

Post-Contrast CT (standard):

  • Infraorbital vessels enhance within the canal

  • Canal walls remain non-enhancing

  • Adjacent orbital and facial soft tissues enhance normally

  • Excellent delineation of canal extent and infraorbital foramen

X-Ray Appearance

  • Best visualized on Waters (occipitomental) view

  • Appears as a linear radiolucent channel within the maxilla below the orbital rim

  • Infraorbital foramen seen as a small round or oval lucency on the anterior maxillary surface

  • Cortical margins are thin and smooth

CT images

Infraorbital canal CT anatomy labelled image-img-00000-00000