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

Few studies have focused on the spread of thermal damage from different blade shapes of ultrasonically activated devices (USADs) used during minimally invasive surgery.

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.

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).

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.