Comparing Mechanical Effects and Sound Production of KTP, Thulium, and CO 2 Laser in Stapedotomy *†Digna M. A. Kamalski, ‡Rudolf M. Verdaasdonk, §Tjeerd de Boorder, kRobert Vincent, *†Huib Versnel, and *†Wilko Grolman *Department of Otorhinolaryngology and Head & Neck Surgery, ÞBrain Center Rudolf Magnus, University Medical Center Utrecht; þDepartment of Physics and Medical Technology, VU University Medical Center Amsterdam; §Department of Medical Technology and Clinical Physics, University Medical Center Utrecht, The Netherlands; and k Jean Causse Ear Clinic, Transverse de Be ´ziers, Colombiers, France Hypothesis: The mechanical and acoustic effects that occur during laser-assisted stapedotomy differ among KTP, CO 2 , and thulium lasers. Background: Making a fenestration in stapedotomy with a laser minimizes the risk of a floating footplate caused by mechanical forces. Theoretically, the lasers used in stapedotomy could in- flict mechanical trauma because of absorption in the perilymph, causing vaporization bubbles. These bubbles can generate a shock wave, when imploding. Methods: In an inner ear model, we made a fenestration in a fresh human stapes with KTP, CO 2 , and thulium laser. During the fenestration, we performed high-speed imaging from dif- ferent angles to capture mechanical effects. The sounds pro- duced by the fenestration were recorded simultaneously with a hydrophone; these recordings were compared with acoustics produced by a conventional microburr fenestration. Results: KTP laser fenestration showed little mechanical ef- fects, with minimal sound production. With CO 2 laser, minis- cule bubbles arose in the vestibule; imploding of these bubbles corresponded to the acoustics. Thulium laser fenestration showed large bubbles in the vestibule, with a larger sound production than the other two lasers. Each type of laser generated significantly less noise than the microburr. The microburr maximally reached 95 T 7 dB(A), compared with 49 T 8 dB(A) for KTP, 68 T 4 dB(A) for CO 2 , and 83 T 6 dB(A) for thulium. Conclusion: Mechanical and acoustic effects differ among lasers used for stapedotomy. Based on their relatively small effects, KTP and CO 2 lasers are preferable to thulium laser. Key Words: Mechanical effectsVStapedotomyVThulium laserVVisualization. Otol Neurotol 35:1156Y1162, 2014. Stapedotomy is a procedure to improve hearing in patients with a conductive hearing loss because of oto- sclerosis. It was introduced as early as the end of the 19th century, and many improvements to the technique have been proposed (1). One of the most important steps of the procedure is the perforation of the stapes footplate, traditionally done with a micropick instrument and later with a microburr. Possible risk of these direct-contact methods, because of mechanical forces, is the occur- rence of a floating footplate or inner ear trauma (2). This can result in substantial sensorineural hearing loss and vertigo. Therefore, a noncontact method to perforate the footplate is preferable. The first noncontact technique was described by Perkins in 1980, using an Argon laser to make a precise hole in the footplate (3). However, using lasers to perforate the footplate is not without risks. The classically used lasers, such as argon (488 nm) and KTP (532 nm), bear the risk of damaging inner ear structures, as residual energy is absorbed in pigmented areas in the vestibule (4). CO 2 (10.6 Km) and thulium laser (contin- uous wave 2 Km) are strongly absorbed in water, causing heating of the perilymph (5Y8). It is thought that heating of the inner ear fluids can cause vertigo, tinnitus, and/or hearing loss, either temporary or permanent (9Y11). Re- cent thermal high-speed imaging confirmed heating by CO 2 and thulium laser (8). Besides heating, also, mechani- cal and acoustic effects can occur during laser-assisted stapedotomy. These effects are mainly caused by absorp- tion of laser energy in water. During this fast absorp- tion, especially in pulsed-laser systems in the mid-infrared region, vapor bubbles can arise (12Y15). Fast expansion of the vapor and especially the implosion after cooling Address correspondence and reprint requests to Digna M. A. Kamalski, M.D., Department of Otorhinolaryngology, University Medical Center Utrecht: Heidelberglaan 100, G05.1293584 CX Utrecht, The Netherlands; E-mail: ent-research@umcutrecht.nl Some of the laser equipment used for this study was provided by Omniguide, Cambridge, MA, USA. The authors disclose no conflicts of interest. Supplemental digital content is available in the text. Otology & Neurotology 35:1156Y1162 Ó 2014, Otology & Neurotology, Inc. 1156 Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.