Comparing mechanical effects and sound production of KTP, thulium, and CO₂ laser in stapedotomy

Hypothesis: The mechanical and acoustic effects that occur during laser-assisted stapedotomy differ among KTP, CO₂, 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 inflict 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, CO₂, and thulium laser. During the fenestration, we performed high-speed imaging from different angles to capture mechanical effects. The sounds produced 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 effects, with minimal sound production. With CO₂ laser, miniscule 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 CO₂, 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 CO₂ lasers are preferable to thulium laser.