Advantages and dangers of erbium laser application in stapedotomy

Among different types of lasers, the erbium laser exhibits particularly favourable characteristics for ear surgery. Experiments with application of erbium laser pulses to the isolated stapes connected to an inner ear model confirmed that there was virtually no thermal effect to the inner ear liquid and that the border damage zone on the stapes footplate perforation did not exceed 5-10 microm. Erbium laser pulses, however, produce pressure waves due to the explosive ablation of tissue. Pulses of 10 to 17 J/cm2 producing pressure waves between 140 and 160 dB appear to be a limit for clinical application. With these criteria, an in-house built erbium YAG laser with a fiberoptic delivery device was used in 15 patients for stapedotomy. A special microhandpiece, where a zirconium fluoride fiber was connected to a quartz tip, was developed. In addition, three patients had stapedotomy with a commercially available Zeiss (Opmi TwinER) microscope equipped with a micromanipulator-operated erbium laser beam. One year after surgery, the air-bone gap was closed in all patients to within 20 dB between 0.5 and 3 kHz with only minor permanent bone conduction threshold losses (< 20 dB). However, we observed an immediate postoperative middle and high frequency loss of up to 75 dB on bone conduction threshold measurements 2 h after surgery, suggesting an acoustic traumatization by the erbium laser. This threshold shift recovered close to preoperative values within 6 h. These observations prompted us to discontinue the clinical use of erbium laser for stapedotomy until the problem of temporary acoustic traumatization is resolved.