Anatomic Measurements for the Endoscopic Modified Lothrop Procedure

Abstract

The aim of this study was to introduce preoperative radiographic frontal recess and sinus anatomic measurements to assist in the selection of patients considered for the modified Lothrop procedure. Data were collected from sagittally reconstructed computed tomography (CT) scans of seven cadaver heads. Four anatomic parameters for measurement were defined as follows: (1) thickness of the nasal beak (desirable < 10 mm); (2) midsagittal distance from nasal beak to skull base (adding 1 and 2 provides the anterior-posterior (AP) space at the cephalad margin of the frontal recess; desirable, > or = 15 mm); (3) accessible dimension (in a parasagittal plane through the frontal ostium; the distance between two lines drawn parallel to the plane of the anterior skull base and perpendicular to the line of the insertion of the nasal endoscope during surgery; the posterior line is drawn at the skull base and the anterior line is drawn at the posterior margin of the nasal beak; the distance between the lines indicates the space available for instrumentation; desirable, > 5 mm); (4) AP dimension of each frontal sinus. The average and the range of each parameter measured were as follows: (1) nasal beak thickness = 8.0 mm (5.0-10.4 mm); (2) nasal beak-skull base = 7.9 mm (2.5-14.1 mm); (3) accessible dimension, 6.1 mm (0.9-9.6 mm); (4) AP diameter of the frontal sinus, 9.7 mm (5.2-14.1 mm). Four specimens were considered candidates for modified Lothrop and three were not. Preoperative radiographic frontal recess and sinus anatomic measurements may assist in the selection of patients considered for the endoscopic modified Lothrop procedure.