Safety of ultrasonic bone curette in ear surgery by measuring skull bone vibrations.

HYPOTHESIS: Mastoidectomy using an ultrasonic bone curette (UBC) is as safe for the inner ear as a mastoidectomy using a high-speed drill.

BACKGROUND

Transcanal endoscopic ear surgery (TEES) is a minimally invasive, secure, and functional technique, which has been performed using high-speed drills. We have started to use a UBC instead of the high-speed drill because a UBC allows for simultaneous bone cutting, irrigation, and aspiration. These features of the UBC make it an excellent candidate for use in one-handed TEES, but the safety of the UBC still needs to be confirmed. We thus measured skull vibrations caused by the UBC to estimate the effects of UBC on the inner ear.

METHODS

Eight patients with cholesteatoma underwent mastoidectomy using a Sonopet UST-2001 UBC (Stryker, MI, USA) and 2 high-speed drills (drills A and B). Skull vibrations were measured using polyvinylidene difluoride film taped to the forehead as a piezoelectric vibration sensor. The recorded data were transformed to the power spectrum in the frequency domain by fast Fourier transform. The mean and peak values of vibrations were analyzed in four frequency bands: 200 to 500 Hz, 500 to 2,000 Hz, 2,000 to 8,000 Hz, and 8,000 Hz to 20 kHz.

RESULTS

Both the mean values and the peak values of skull vibrations caused by the UBC were significantly smaller than those values obtained for drill B between 500 and 8,000 Hz, (p < 0.05). No significant differences were found among the 3 instruments below 500 Hz or above 8,000 Hz.

CONCLUSION

Skull vibration levels generated by the UBC were found to be comparable or even lower than those levels associated with conventional high-speed drills. These findings indicated that the UBC can be safely applied to TEES without the risk of harmful effects on the inner ear.