Draf III Extension in the Endoscopic Endonasal Transethmoidal, Transcribriform Approach Through the Back Wall of the Frontal Sinus: A Cadaveric Study

BackgroundThe Draf III (modified endoscopic Lothrop) procedure has been proposed to extend the endonasal transethmoidal, transfovea ethmoidalis, and transcribriform approach through the back wall of the frontal sinus. The exposure is time-consuming and increases the risk of cerebrospinal fluid leak, and the indications for use are not well described. There are few data quantifying the advantage it conveys over the approach without the Draf III procedure.MethodsAn endoscopic, endonasal transfovea, transcribriform approach was performed in 5 fresh, injected cadaveric heads. Anatomic boundaries and measurements of the exposure were compared before and after addition of a Draf III procedure. Computed tomography scans were performed before and after dissection, and additional radiographic measurements were made to quantify the additional exposure provided by the Draf III procedure. Also, 2 clinical cases are presented in which a Draf III procedure was used.ResultsThe mean anterior to posterior boundary from the frontal sinus to the planum sphenoidale before the Draf III procedure was 3.0 cm and after the Draf III procedure was 3.8 cm with an average change of 0.8 cm. After the Draf III procedure, the mean anterior to posterior boundary from the posterior wall of frontal sinus to the planum sphenoidale increased from 3.0 cm to 4.3 cm. There was an average increase of 1.3 cm with an average increased area of view of 1.79 cm2.ConclusionsThis study quantifies the increased field of view provided by the Draf III procedure during anterior skull base dissection. Recommendations for preoperative examination of radiographic evidence are provided to help identify which individuals would benefit from the additional exposure.