A stepwise surgical technique using the medial orbital floor as the key landmark in performing endoscopic sinus surgery

Hypothesis: The medial orbital Boor (MOF) and adjacent bony ridge of the an trostomy, when combined with columellar measurements, are easily identifiab le and consistent anatomic reference points from which critical orbital and skull base structures can be found during endoscopic sinus surgery. Method s: Two examiners, with varying endoscopic sinus surgery experience, perform ed endoscopic and direct measurements from the columnella and medial orbita l floor to critical orbital and skull base structures on II human cadaver h eads (18 sides). The distances to four critical skull base or orbital struc tures and to the anterior and posterior wall of the sphenoid sinus were mea sured,The mean, ranges, and standard deviations for all measurements (endos copic and direct) were calculated and simple regression analysis was perfor med. Results: The mean and range of values for each of the variables correl ated well between examiners, and between endoscopic and direct measurements . There was slightly more variability in measurements when the MOF was used . However, the differences were no more than a few millimeters and did not appear to affect the overall clinical use of these values. Conclusions: The MOF and adjacent bony ridge of the antrostomy, when combined with columell ar measurements, are easily identifiable and consistent anatomic landmarks that are not affected by the presence of significant inflammatory disease o r previous surgery. These reference points provide even the most inexperien ced surgeon with precise anatomic localization within the paranasal sinuses . They also determine the correct anteroposterior trajectory into the sphen oid sinus, whereby inadvertent intracranial or intraorbital complications m ay be avoided.