2026 Poster Presentations
P340: ENDOSCOPIC TRANSCONJUNCTIVAL TRANSORBITAL TRANSMAXILLARY APPROACH TO THE UPPER CERVICAL SPINE: SURGICAL ANATOMY
Alhusain Nagm, MD, MSc, PhD; University of Maryland Baltimore
Objectives: Step-by-step description of the endoscopic transconjunctival transorbital transmaxillary (ETCOX) approach to reach the upper cervical spine (UCS) and emphasizing its surgical nuances.
Background: The transorbital route to the upper cervical spine has not been described before in literature. This novel study could address the limitations of extended endoscopic endonasal approach.
Material and Methods: Seven colored-injected formalin-fixed heads were utilized for the left-sided ETCOX in two phases. In phase 1, endoscopic endonasal aproach (EEA) to UCS, completion of preparatory surgical steps via extended endoscopic approach to the craniocervical junction (harvesting right-sided nasoseptal flap, left reverse flap, posteriornasal septectomy, drilling of the palatine crest, left-sided medial maxillotomy with total-middle and partial-inferior turbinectomies, identifying the infraorbital nerve (ION) exposing the pteygoid fossa, left-side drilling of the sphenoid between the vedian canal and foramen rotundam, releasing the left eustachian tube from the foramen lacerum, downward reflection of a U-shaped nasopharyngeal flap, exposing the foramen magnum and anterior C1 cervical arch), identifying the reference horizontal line, midline. Following drilling of the UCS, the most inferior (Sg1) and lateral drilled targets were identified by navigation, and the surgical freedom was calculated.
Phase 2 emphasizes the benefit of adding ETCOX to reach beyond the limit of phase 1. Conjunctival inferior fornix incision was made, and two windows medial-and-lateral to the ION were created to reach the UCS. Drilling of the UCS continued and the most inferior (Sg2) and lateral drilled targets were identified by navigation, and the surgical freedom was calculated. The dura was opened, and the data were collected and analyzed.
Results: The hard palate is an anatomical obstacle that limits the inferior accessibility to the UCS via pure EEA (Sg1). The ETCOX (Sg2) component overcomes this daunting challenge and allows significant inferior and contralateral accessibility to the UCS in comparison to the pure EEA (P<0.05). Based on reference points, Sg2 is significantly inferior to Sg1. The UCS area of exposure (AoE) via ETCOX is significantly larger than AoE via pure EEA. The superficial (boney) and deep (dural) AoE are significantly larger in ETCOX. The contralateral C1 foramen transversarium line is easily accessible via left ETCOX approach, and inaccessible on the ipsilateral side. Symmetrical Drilling of the whole C3 body and reaching C3-C4 disc space is achievable via ETCOX approach.
The horizontal angle of freedom around the ION via ETCOX is significantly wider than its vertical angle. The globe, lacrimal sac and orbital rim limit the vertical angle of freedom.
Conclusion: Adding ETCOX approaches is promising. It provides additional workspace. Clarifying the surgical targets and structures-at-risk benefits to the realization of limitations and providing prospective feedback for operative theatres.