Optic Nerve Surface Temperature during Intradural Anterior Clinoidectomy: A Comparison Between High-Speed Diamond Burr and Ultrasonic Bone Curette

Background: Ultrasonic bone curettes are increasingly used in cranial base surgery. The heat generated by these devices during anterior clinoidectomy has not been evaluated.

Objective: To compare optic nerve surface temperature during intradural anterior clinoidectomy using the drill and ultrasonic bone curette.

Methods: Ten fresh cadaver heads were used. During intradural clinoidectomy and optic nerve unroofing with either 2mm diamond burr drill or ultrasonic bone curette, temperature was measured along the medial cisternal and proximal intracanalicular segments of the optic nerve. Additional experiments were performed to determine optimal ultrasonic bone curette settings for anterior clinoidectomy.

Results: At the medial cisternal segment, peak and mean temperature were significantly higher with the ultrasonic bone curette (peak 38.8 vs 29.3°C, p = 0.03, mean 29.5 vs 22.6°C, p = 0.003). At the proximal intracanalicular segment, only peak temperature was significantly higher with the ultrasonic bone curette (peak 32.0 vs 23.5°C, p = 0.02, mean 26.9 vs 22.4°C, p = 0.07). Using standard company settings, room temperature irrigation fluid was heated by the oscillating tip to peak temperature 36.1°C without drilling. To maintain emitted irrigation fluid at room temperature, optimal settings were amplitude 70%, cool irrigation (5°C) at 40mL/min. Using these settings, the ultrasonic bone curette generated optic nerve surface temperature measurements similar to the drill.

Conclusion: Using standard company settings, the ultrasonic bone curette generates significantly higher temperatures at the optic nerve surface. Optimal ultrasonic bone curette settings were amplitude 70% with cool irrigation (5°C) at 40mL/min. Further work is necessary to translate these findings into the operating room.