Background and Objective
A new, flexible-fiber, CO2 laser deliver system has recently been introduced into clinical use. For ear surgery applications, no data has been reported correlating power settings to depth of penetration into otic capsule such as that which covers the cochlea. Our goal in this study was to document such.
Study Design/Materials and Methods
Eight (8) cadaveric temporal bones were procured as per our institution’s protocols. For each specimen, 9 different laser holes were burned into the bone overlying the cochlea using the flexible-fiber CO2 laser. Power settings were varied from 10–20 Watts in 2 Watt increments, and duration of exposure was either 100, 200, 300, 400, or 600 mSec. Each setting (power and duration) were tested on 2 specimens. Following laser exposure, each specimen was scanned in a microCT scanner and the depth of penetration measured from these images.
Results
Of the 72 laser shots, 8 were excluded due to double hits (4) or oblique hits (3) or complete penetration to perilymph (1). After excluding these 8, bone penetration was found to vary from 160 to 670μm based on power and time settings. Spearman analysis on ranked data showed that time had a greater impact on depth than power. The correlation coefficients for time and power were 0.84 (p = 0.013) and 0.40 (p < 0.001), respectively.
Conclusion
The flexible-fiber CO2 laser is useful in ear surgery for ablation of soft tissue and bone. However, higher power setting and longer pulse durations can lead to complete penetration of the otic capsule causing damage of underlying structures such as the facial nerve, horizontal semicircular canal, and cochlea.