Modification of the Thermal Spread by the Blade Shape of an Ultrasonically Activated Device.

ABSTRACT

BACKGROUND: Few studies have focused on the spread of thermal damage from different blade shapes of ultrasonically activated devices (USADs) used during minimally invasive surgery. METHODS: In vivo experiments using pig arteries, nerves, and mesentery were used to compare the thermal spread of two different blade types of USADs, non-tapered and tapered, under the same conditions. The tissue temperatures were monitored using a high-resolution infrared thermographic camera and calculated using an image analysis program. The spread of heat denaturation was measured histologically. RESULTS: The temperature was greater at the sides with greater curvature when non-tapered USADs were activated (artery, 1 s, 2 mm - 0.92 ± 0.5 °C vs. - 0.44 ± 0.5 °C, P = 0.022). This effect was more prominent in the tapered type (artery, 1 s, 0/1/2 mm 9.14 ± 3.7 °C vs. 28.3 ± 16.2 °C/0.5 ± 1.4 °C vs. 9.76 ± 6.2 °C/ - 0.12 ± 0.9 °C vs. 1.44 ± 1.9 °C, P = 0.044/0.016/0.038, respectively). The temperatures in the tapered USAD were significantly higher at some time- and distance-points than those in a non-tapered USAD (artery, 1 s, 0 mm, Less/1 s, 1 mm, Gre 4.2 ± 2.9 °C vs. 9.14 ± 3.7 °C /0.36 ± 0.5 °C vs. 9.76 ± 6.2 °C, P = 0.047/0.027; nerve, 2 s, 0 mm, Gre 6.54 ± 3.9 °C vs. 17.66 ± 6.2 °C, P = 0.012). A three-directional study revealed the thermal spread of the mesentery was greatest at the tip side of the non-tapered type USAD (4.55 ± 2.53 °C vs. 12.43 ± 4.03 °C/12.43 ± 4.03 °C vs. 5.04 ± 1.91 °C, P = 0.003/0.005). CONCLUSIONS: The thermal spread changed according to the blade shape of the USAD. This knowledge can be applied to more meticulous and complicated procedures, reducing surgical morbidity.