Experimental evaluation of drills for extended frontal sinusotomy

Endonasal extended frontal sinusotomy is needed in rare cases of therapy-resistant chronic frontal sinusitis. Several types of burs have been invented to ablate strong bone in the frontal sinus access but nevertheless surgical results seem to differ significantly. The benefits and shortcomings of different burs are subjected to a comparative evaluation.

Five cadaver specimens were duplicated by means of dental molding and casting techniques to provide identical microanatomy for comparative studies on frontal sinusotomy. Different burs (conventional straight bur, right-angled bur according to Blokmanis, and curved frontal sinus bur) were applied to create a type IIb frontal sinusotomy according to Draf in microanatomical replicas. The geometry of the frontonasal neoostium was measured and its dimensions were contrasted to the collateral damage. Bone ablation was calculated by repeated weighting and the area of damaged mucosa was quantified using a 3D analyzing system.

A frontal sinus neoostium measuring 9 x 10 mm on average was created by type IIb frontal sinusotomy according to Draf. The complementary use of an angled bur showed some specific improvements that applied best to spacious anatomic specimens. Those specimens subjected to an extensive use of the straight drill revealed significant collateral damage forming a contrast to minor enlargement of the neoostium. The curved frontal sinus bur showed considerable technical insufficiencies.

Judicious use of the straight drill is recommended for those rare cases of therapy-resistant frontal sinusitis treated by an extended type of frontal sinusotomy. New technical refinements of the curved frontal sinus burs should be subjected to repeated evaluation.