Objective To further optimize the surgical technique with the CO2 laser in stapes surgery a scanner system was used to obtain a footplate perforation of 0.5 to 0.6 mm with only 1 laser application (“one-shot” stapedotomy). Study design 188 patients with otosclerosis were submitted to a primary CO2 laser stapedotomy with the SurgiTouch™ scanner. This study surveys the surgical technique and clinical results. Results An adequately large perforation diameter could be achieved with a single shot in 68% of the patients treated with the SurgiTouch™ scanner. In 11% of the patients, a second laser application at the same site was necessary. In 21% of the patients, the perforation had to be enlarged by several slightly overlapping laser applications without scanner. The clinical data of this study clearly documents that there is no evidence of laser depending inner ear affections. Conclusion The CO2 laser combined with modern scanner systems is well suited for application in stapes surgery.

CO2 laser stapedotomy with the "one-shot" technique--clinical results.

Since 1992 a small air-cooled opthalmological argon laser (Augus system, 3 W max.) equipped with a fiberoptic microhandpiece has been used for stapedotomy at the Inselspital, Berne. The microhandpiece has been developed especially for otological purposes in our electronic laboratory. In order to measure the effect of argon laser pulses applied through the handpiece to the ear, we performed temperature measurements in a saline-filled inner ear model by using ultrathin (2 μm thick), ultrafast (4 ns) thermosensitive rhodamine-coated polyurethane films. Multiple laser pulses of 1–2.5 W and 0.1 s duration — as used in clinical applications — produced a temperature elevation of about 1 ° C in the liquid of the inner ear model. The local laser effect was then examined histologically on the isolated stapes. The thermal damage zone around the stapedotomy perforation was limited to about 100 μm. In a clinical study we compared the results of argon laser stapedotomy (n = 54) with those of a skeeter microdrill stapedotomy (n = 29). Substantial hearing gains were found in all cases in both groups. In the laser stapedotomy group the mean residual air-bone gap (0.5–2 kHz) was 10 dB or less in all cases but one. Inner ear function remained unchanged except for a 40-dB loss at 4000 Hz in one case. Transient vertigo with nystagmus occurred in one case. Facial nerve dysfunction did not occur in any patient. The most important advantage of the laser found was the absence of mechanical trauma to the stapes. Stapes luxation and a floating footplate were avoided. In contrast, thick footplates were more easily perforated with the skeeter. Use of an argon laser equipped with a fiberoptic microhandpiece and a skeeter microdrill as needed seems particularly advantageous for stapedotomy.

Experimental and clinical results of fiberoptic argon laser stapedotomy

Es wird uber die Haufigkeit und moglichen Ursachen von Arrosionen und Nekrosen des langen Ambosschenkels bei verschiedenen Prothesentypen nach Steigbugeloperationen im Rahmen der Otosklerose berichtet. Zugrunde liegen 1144 Stapesoperationen, davon 117 Revisionen nach vorangegangener Fremd- und 27 Revisionen nach Eigen-Stapesoperation im Zeitraum von 1978 bis 1995. Es werden erstmals Ambosschenkelnekrosen durch Teflon-Platin-Piston anhand von 5 Operationsbeobachtungen beschrieben, bei denen die Platinbandschlinge den Ambosschenkel in mediale Richtung vollstandig durchwandert hat. Mit Hilfe von rasterelektronenmikroskopischen Aufnahmen eines Teflon-Platin-Piston und eines Goldpiston sowie 2 vergleichenden Operationsbeobachtungen, bei denen ein Teflon-Draht-Piston und ein Goldpiston verwendet wurden, wird die Hypothese aufgestellt, das die wendelformigen Rillen in der Oberflache des Teflonkolbens zusammen mit einer gestorten Mittelohrmechanik die Hauptursache fur den in Richtung ovaler Nische entstehenden Narbenzug mit daraus resultierender Ambosschenkelnekrose ist. Als Fazit aus den Operationsbeobachtungen und der aufgestellten Hypothese werden die Anforderungen an eine optimale Steigbugelprothese zusammengefast.

Die Arrosion und Nekrose des langen Amboßschenkels nach Otoskleroseoperation

Animal experiments in mature guinea pigs were devised to determine whether and to what extent inner ear damage can be caused by in vivo use of the erbium laser for stapedotomy. The present study examined the laser effect in connection with perforation of the basal convolution of the cochlea and subsequent application in the opened cochlea. Acoustic evoked potentials as compound action potentials (CAP) were recorded for changes in inner ear function. Findings demonstrated that five applications of the erbium:YSGG (yttrium-scandium-gallium-garnet) laser (energy, 85 mJ/pulse; energy density, 36 J/cm2) were needed to create a footplate perforation of 500–600 μm and did not lead to CAP alteration in any animal (n = 20). An increase of the repetition rate from 1 to 5 Hz likewise caused no CAP alteration (n = 17). Application of high total energies in the open cochlea (n = 5) to determine the safety of the laser system for stapedotomy revealed that a 10-fold increase in the total energy required for adequate perforation led to irreversible CAP alterations and no CAP could be recorded at a 15-fold increase in total energy. In contrast, a 5-fold maximum increase in total energy caused no CAP alterations. These results demonstrate the safety of the Er:YSGG laser comparable to that of the CO2 laser for stapedotomy, supporting its utility as an alternative method for surgery.

Experimental studies on the suitability of the erbium laser for stapedotomy in an animal model.

We evaluate the feasibility of nanosecond-pulsed and femtosecond-pulsed lasers for otologic surgery. The outcome parameters are cutting precision (in micrometers), ablation rate (in micrometers per second), scanning speed (in millimeters per second), and morphological effects on human middle ear ossicles. We examine single-spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG laser (355 nm, beam diameter 10µm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. A similar system (355 nm, beam diameter 20µm, pulse rate 10 kHz, power 160–1500 mW) and a femtosecond-pulsed CrLi:SAF-Laser (850 nm, pulse duration 100 fs, pulse energy 40 µJ, beam diameter 36 µm, pulse rate 1 kHz) are coupled to a scanner to perform bone surface ablation over a defined area. In our setups 1 and 2, marginal carbonization is visible in all single-spot ablations of 1-s exposures and longer: With an exposure time of 0.5 s, precise cutting margins without carbonization are observed. Cooling with saline solution result is in no carbonization at 1500 mW and a scan speed of 500 mm/s. Our third setup shows no carbonization but greater cutting precision, although the ablation volume is lower. Nanosecond- and femtosecond-pulsed laser systems bear the potential to increase cutting precision in otologic surgery.

https://www.spiedigitallibrary.org/journals/Journal-of-Biomedical-Optics/volume-11/issue-01/014004/Morphological-effects-of-nanosecond--and-femtosecond-pulsed-laser-ablation/10.1117/1.2166432.pdf

Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles.

Die Bearbeitung der Steigbügelfussplatte mit verschiedenen Lasersystemen. I: Kontinuierlich strahlende Laser

Die Bearbeitung der Steigbügelfussplatte mit verschiedenen Lasersystemen. II: Gepulste Laser

Tierexperimentelle Untersuchungen zur CO 2 -Laser-Stapedotomie*, **

Laser stapedotomy has now become an established method in the surgical treatment of otosclerosis. Recent experimental studies have demonstrated that, apart from the continuous wave lasers, several pulsed laser systems are also suitable for stapes management. Experiments were performed in guinea pigs to clarify which, if any, of the pulsed lasers used can damage the inner ear on application of the laser parameters required for the stapedotomy. The basal convolution of the guinea-pig cochlea was chosen as the application site. Acoustic evoked potentials (compound action potentials (CAP)) yielded information on inner-ear function. With the Er:YSGG laser (energy:85 J/pulse, energy density:36 J/cm 2 , total energy: 0.425 J), five applications to the cochlea are necessary for a foot plate perforation of 500-600μm. With the Ho:YAG laser, an adequately large perforation can be achieved with at least 10 applications of an energy of 210 mJ per pulse (energy density: 90 J/cm 2 , total energy: 2.1 J). The aim of this study was: (1st) to clarify whether the Er:YSGG and Ho:YAG laser could cause morphological changes in the organ of Corti of the guinea pig on application of the laser parameters required for stapedotomy, and (2nd) to verity our experimental electrophysiological results and correlate them with the morphological changes detected in the organ of Corti in the guinea pig cochlea by scanning-electron-microscopic examination. It shows that the effective laser parameters (5 x 85 mJ) of the Er:YSGG-laser cause no changes of the guinea pig cochlea. Even with the application of 25 pulses with the same energy the guinea pig cochlea shows normal appearance. The effective laser parameters of the Ho:YAG laser (10 x 210 mJ) show changes in the outer hair cells in the form of stereocilie fusion and giant hair cell formation while the inner hair cells and supporting cells are showing normal appearance. Our results clearly demonstrate a high application safety for the Er:YSGG laser, while the Ho:YAG-laser is not well tolerated in the animal experiment and has only a low application safety. Its application in stapedotomy would be unreliable and dangerous for the inner ear. Our results also clearly show that the electrophysiological data correlate well with the scanning-electron-microscopic data.

Effects of pulsed Er:YSGG-and Ho:YAG-laser on the organ of Corti of the guinea pig cochlea : a scanning- electron- microscopic study

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Die Bearbeitung der Steigbügelfussplatte mit verschiedenen Lasersystemen. I: Kontinuierlich strahlende Laser

Die Bearbeitung der Steigbügelfussplatte mit verschiedenen Lasersystemen. II: Gepulste Laser

Tierexperimentelle Untersuchungen zur CO 2 -Laser-Stapedotomie*, **

Effects of pulsed Er:YSGG-and Ho:YAG-laser on the organ of Corti of the guinea pig cochlea : a scanning- electron- microscopic study