Experimental investigations of CO2 laser application in middle ear ossicles

Background. During the last few years, several laser systems have been applied for procedures in middle ear surgery. In this study, we determined the technical parameters for the dissection of the middle ear ossicles with the CO2 laser and analyzed the histological findings. Methods. The malleus necks of 16 human temporal bones were dissected under standardized conditions using a CO2 laser with a power output between 35 and 55 kW/cm(2). The specimens were fixed and histological probes of 50-mum thickness were prepared. Results. The laser outputs led to crater diameters from 0.14 to 0.55 mm. As an analogy between laser energy and thermal tissue destruction, three zones of thermal damage were differentiated: a cinder zone,a carbonization zone, and a zone of dehydration. The metrical dimensions of these zones did not show any correlation to the applied laser energy. Conclusions. The data of this study show that commercially available CO2 lasers are sufficient for a safe and effective partial resection of middle ear ossicles using a power output of 35 kW/cm(2).