Clinico-anatomic study of the spina nasalis ossis frontalis and its role within the scope of frontal sinus surgical approach

Abstract

During endonasal frontal sinusotomy using the sharp spoon (endonasal frontal sinus surgery type II according to Draf or May and Schaitkin) a solid piece of bone is frequently encountered anterior to the neo-ostium. This bone may be referred to as a "nasal spine". A prominent spine may render a sinusotomy difficult or even impossible. A maximum endonasal frontal sinusotomy was performed on 36 anatomical specimens by means of a sharp spoon producing neo-ostia of 7 x 5 mm on average. The dimensions of the remaining nasal spine were measured subsequently together with the diameter of the inferior frontal sinus, the thickness of the anterior frontal sinus wall, and the distance from the neoostium to the anterior ethmoidal artery. Almost every specimen (97%) showed a relevant nasal spine. The average height of the spine was 10 mm. The anterior-posterior dimension was 6 mm on average. A correlation was found between the nasofrontal angle and the a.-p. dimension of the spine: the more acute the angle, the thicker the spine was. In three out of four specimens the neo-ostium was separated by just one anterior ethmoidal cell from the anterior ethmoidal artery. In the majority of the specimens a sufficient endonasal approach to the frontal sinus could be obtained by enlarging the natural ostium as described by Draf or May and Schaitkin. The anterior ethmoidal artery is a valuable landmark for locating the ostium. The maximum diameter of the frontal sinus approach in frontal direction can be estimated by measuring of the nasofrontal angle.