Comparative Cadaveric Study and Anatomical Limitations of the Nasofrontal Trephination: A Novel Endoscopic Corridor for Enhanced Exposure of the Odontoid and Occipital Condyle Regions

Objective: The endoscopic endonasal approach (EEA) is commonly used as the primary minimally invasive route to the ventral craniovertebral junction (CVJ). However, anatomical constraints limit the caudal reach attainable via EEA. Multiport endoscopic approaches may complement a standard EEA providing additional reach. This anatomical study aims to evaluate the anatomical limitations of the EEA in accessing the CVJ and how these limitations may be overcome by the contralateral nasofrontal trephination (CNT) port.

Methods: EEA and CNT dissections were performed on 32 cadaveric specimens under stereotactic guidance. Key anatomical measurements included the naso-axial line (NAxL) angle, anteroposterior (AP) frontal sinus distance, interorbital distance, and distance of odontoid process from the hard palate line. The area of exposure (AoE) achieved via the EEA and CNT approaches were quantified using a surgical navigation system.

Results: The CNT approach demonstrated significantly larger AoE when targeting the odontoid (1,720.41 vs. 1,086.62 mm², p ≤ 0.001) and occipital condyle (613.32 vs. 446.15 mm², p ≤ 0.001), compared to an EEA. The AP frontal sinus distance positively correlated with the CNT AoE to the odontoid (r = 0.889, p < 0.001) but not to the occipital condyle (r = −0.009, p = 0.966). Interorbital distance showed no significant impact on CNT AoE. The CNT approach showed significantly larger angle of attack compared to EEA (49.8 vs. 16.5°, p ≤ 0.001). A negative correlation was observed between the NAxL angle and the caudal-most level attained at the odontoid process (r = −0.757, p < 0.001). No significant correlation was found between achieved AoE via EEA and NAxL (r = 0.161, p = 0.386).

Conclusion: Incorporating the CNT approach complements the EEA, improving the inferior reach the management of complex CVJ pathologies. While the NAxL may assist in predicting the inferior limit of the EEA, anatomical variability and the lack of correlation between the NAxL angle and the area of exposure impose constraints on its utility as a sole determinant for surgical planning.

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Artikel online veröffentlicht:
07. Februar 2025