“…A narrow frontal recess, type 4 frontal cells, and pathologic abnormality in the lateral or superior aspects of the sinus can often remain out of reach for endoscopic frontal instruments. [10][11][12] In addition, neoosteogenesis of the frontal recess, previous trauma, severe frontal recess stenosis, and frontal bone osteomyelitis may necessitate an external approach. 12 Two open techniques, frontal sinus trephination and the OPF, remain viable adjuncts to endoscopic sinus surgery for the frontal sinus.…”