M. Kautzky

Fixation of zygomatic fractures with a new biodegradable copolymer osteosynthesis system. Preliminary results.

In a prospective study, a new biodegradable osteosynthesis material for the facial skeleton has been used in 27 patients with zygomatic fractures. In the six-month follow-up period, the first ten patients showed clinically and radiologically uneventful healing of bone. There were no implant-related complications. The main advantages of the new material are its malleability when heated, enabling fast adaptation to the bone surface, and the avoidance of a second operation for implant removal.

Infrared laser stapedotomy

SummaryA pulsed holmium: YAG laser (λ = 1980 nm) was used to perform 0.4 mm stapedotomy fenestrations in human stapes footplates from freshly dissected cadavers under simulated surgical conditions. The energy was coupled into (λ 400 μm core diameter nylon fiber. Thermal gradients were then measured following laser applications and tissue responses examined by light microscopy. The results of this study suggest the feasibility of using (λ surgical holmium: YAG laser in middle ear surgery.

Does choir singing cause noise-induced hearing loss?

Although health problems in musicians have been previously reported; not much is known about noise-induced hearing loss due to choir singing. However, there are data to show that peak levels of more than 110 dB SPL are produced in choir singing, and major parts of sound energy can be found below 1 kHz and even 500 Hz but not below 100 Hz. To find out about possible hearing loss due to professional choir singing, we measured the hearing threshold level of 62 choir singers in a large opera choir. Most publications about noise-induced hearing loss report that the high-frequency region is impaired most. However, in our study the low frequency region was affected most, when compared with normative data (especially ISO 7029). Control groups of women and men with normal auditory function did not show pure-tone hearing thresholds different from ISO 7029. The permanent threshold shifts at 250 Hz and above are most likely noise induced with choir singing as noise source. However, hearing losses at 125 Hz and possibly partial at 250 Hz are caused by some other effect. An (unproven) hypothesis is that singing might lead to increased endolymph pressure, and thus might cause hearing loss especially in the low-frequency region. Whether more choirs show similar hearing impairment and whether singing raises cerebrospinal fluid pressure will be the subject of further investigations.

Holmium:YAG- und erbium :YAG-infrarotlaser-osteotomie

SummaryThe in-vivo bone ablation characteristics of a pulsed solid-state erbium:YAG laser were compared to those of a pulsed solid-state holmium:YAG laser. Partial osteotomies in the maxillary, the mandibulary, and the nasal bones of white rats were performed. The tissue response was examined by light microscopy. Thermal gradients following the laser application were also measured. Over all energy levels tested the erbium:YAG laser produced ablation of bone with minimal thermal damage to the adjacent tissue. The results of this study are promising for future application of the infrared holmium-and erbium:YAG lasers in otorhinolaryngology.ZusammenfassungDie knochenablative Wirksamkeit der gepulsten Festkörperlaser Holmium:YAG (λ = 2120 nm) and Erbium:YAG (λ = 2940 nm) wurde im Tierversuch vergleichend untersucht. Als Modell für eine klinische Anwendung wurden partielle Oberkiefer-, Unterkiefer-und Nasenbeinosteotomien an der Ratte durchgeführt. In einer ersten Versuchsreihe wurden die unmittelbare klinische Wirkung und das histologische Wirkungsprofil dieser Infrarotlaser am Hartgewebe erforscht und die Temperaturgradienten im Knochen während der Laseranwendung gemessen. Die geringe Ausdehnung der Schädigungszone im Randbereich der Laserinzisionen und das für den Erbium:YAG-Laser praktisch atraumatische, athermische Knochenabtragungsvermögen läßt die neuen Infrarotlaser als ideale Schneidegeräte für Osteotomien erscheinen.

Flexible fiberoptic endoscopy and laser surgery in obliterated cochleas: human temporal bone studies.

The use of conventional drilling procedures in cochlear implant surgery of ossified cochleae poses special risks to the facial nerve and the carotid artery. This study evaluated the alternate use of flexible fiberoptic endoscopy and mid‐infrared laser surgery for recanalization of partially and artificially obliterated cochleae in freshly dissected human cadavers.

Traumatizing effects of blind oral intubation using the Augustine Guide.

PURPOSE This study evaluated whether the Augustine Guide, a device enabling blind oral intubation, carries a high risk for laryngopharyngeal trauma in routine airway management. PATIENTS AND METHODS Telescopic laryngoscopic or microlaryngoscopic examinations were performed in 20 patients before and immediately after blind oral intubation, as well as 24 hours postoperatively. RESULTS Intubation using the Augustine Guide was successful in all but one patient. However, 18 of 20 patients showed evidence of considerable trauma to the laryngopharyngeal region. Vallecular edema, epiglottic swelling, mucosal lacerations, and vocal cord hematomas, causing a high percentage of postoperative discomfort, occurred in a very uniform pattern. CONCLUSIONS It was concluded that blind oral intubation using the Augustine Guide should not be used in routine airway management but should only be used in special indications.

Holmium: YAG laser surgery in obliterated cochleas: an experimental study in human cadaver temporal bones.

A pulsed holmium: YAG laser (λ = 2120 nm) was used to reopen the basal turn of artificially obliterated human cochleas in freshly dissected cadavers. This allowed intracochlear insertion of the stimulation electrode of a cochlear implant under simulated surgical conditions. Laser energy was transmitted through a 400-μm nylon fiber via the opened facial recess directly to the round window niche. At an energy level of 500 mJ per 2.5 μs pulse, a repetition rate of 2 Hz, and an exposure time of 20–30 s, the photo-ablative mechanism of laser-bone interaction led to a 8–10 mm recanalization of the basal turn of the cochlea without damaging surrounding structures. The artificial bony occlusion and the recanalized basal turn of the cochlea were visualized by means of computed tomography and studied under light microscopy, using a histologic thin-section technique.

Soft-tissue effects of the holmium:YAG laser: An ultrastructural study on oral mucosa

The specifics of the ablation mechanism of the holmium:YAG laser remain largely unexplored. Following laser exposure to the oral mucosa of rats, the ultrastructural damage profile obtaining to varying degrees in blood vessels, erythrocytes, nerves, and muscle cells was examined. An attempt was made to relate the cytoplasmatic alterations to the tissue ablation modes of midinfrared lasers described in the literature.

Infrared laser soft tissue ablation versus ultraviolet excimer laser: Experimental introduction of the Hol:YAG-laser in oral surgery

The in vivo tissue ablation characteristics of a pulsed infrared laser (Hol:YAG, lambda = 2120 nm) and a pulsed excimer laser (XeCl, lambda = 308 nm) were studied in an animal model. Laser energy was delivered via nylon fibers for the Hol:YAG laser and via quartz fibers for the excimer laser. Laser incisions were made under precise reproducible conditions on the sublingual side of the tongue and the gingiva of white rats. Laser surgery was done at two different energy output settings for the Hol:YAG laser and at one setting for the excimer laser. Histologic studies revealed tissue defects with clean contours for both laser types with small zones of necrosis of the adjacent tissue (Hol:YAG: 180 microns to 640 microns; excimer: 40 microns to 160 microns) and without carbonization. Both laser types function on the principal of photoablation and permit excellent control of tissue ablation. Wound healing was studied over a 10-day period and showed complete wound closure by re-epithelialization. The in vivo tissue ablation characteristics and the surgical reliability of the two lasers are compared and discussed with respect to oral and periodontal surgery.

Effects of the Holmium: YAG and Erbium: YAG Lasers on Endotracheal Tubes

Endotracheal tube (ET) fire is the most frequent complication arising with laser surgery in the upper aerodigestive tract. No data are available about the safety of commonly used ETs when used with recently developed high-energy pulsed lasers, working with only a minimal thermal component but mainly photoablative. A comparative in vitro study was performed with three types of endotracheal tubes to assess their resistance to wall and cuff damage by the laser beams of two pulsed infrared solid-state lasers. ET perforation was attempted with the erbium:YAG (lambda = 2,930 nm) and holmium:YAG (lambda = 2,120 nm) lasers. For all experiments, a repetition rate of 5 Hz was used. The 2.5-microseconds holmium:YAG pulses were coupled into a nylon fibre of 400 microns diameter. The 2.0-microseconds erbium:YAG laser pulses were applied to ETs through a lens system providing a spot size diameter of 200 microns. Polyvinyl chloride and silicon ET segments were exposed to laser pulse energies from 97 to 500 mJ in the presence of different anaesthetic gas mixtures. The time from the onset of exposure to tube perforation was recorded. Thermal gradients following laser application were measured. Laser exposure was continued for up to 90 s, unless tube ignition occurred. At all energy levels tested, the photo-ablative mechanism of laser-tube interaction, with few thermal components, led to laser-induced tube ignition if an FiO2 > 21% for the holmium:YAG and 34% for the erbium:YAG laser was established. With increasing pulse energies, ET segments ignited sooner. MLT tubes performed best in the present safety test.