Pushing the boundaries of endoscopic surgery: the extended transodontoid approach for craniovertebral junction pathologies. Comprehensive technique description and comparative result.

Introduction: The craniovertebral junction (CVJ) is susceptible to diverse pathologies. While the transoral-transpharyngeal approach has been the primary method for addressing anterior CVJ conditions, it carries significant morbidity. Endoscopic endonasal approach (EEA), has emerged as a Minimally invasive option. However, EEA has potential limitations in providing adequate caudal exposure. This study aims to evaluate the feasibility of enhancing caudal exposure to the endoscopic transodontoid (TO) approach by drilling the posterior part of the central hard palate, thus achieving an extended endoscopic approach to odontoid (ETO) and to compare the accuracy of predictive lines, (Nasopalatine line (NPL), Nasoaxial line (NAxL), and Rhinopalatine line (RPL)) in predicting the caudal limit of the approach.

Methods: Eight cadaveric specimens underwent pre and post-endoscopic dissection measurements. The distance resected (DR), and inferior exposure of C2 posterior wall (PW) were measured and compared between TO and ETO. Furthermore, multivariable logistic regression was utilized to assess the predictive line values for DR.

Results: Implementation of the ETO resulted in a significant increase in mean DR (8.6 mm, 52% improvement, p-value 0.03381), and the inferior exposure of the PW increased by 5.31 mm (p-value 6.063e-05, 37% greater exposure). The linear multivariable regression analysis indicated significant positive associations between NAxL, RPL and DR after TO. However, these associations were not seen for ETO.

Conclusion: The ETO proved superior to the traditional approach, providing improved caudal exposure and distance resected. While NPL and NAxL demonstrated predictive value for the TO, their utility was somewhat limited in the ETO.