Comparison of linear and torsional mode ultrasonic coagulating shears for the sealing of medium – to large-sized arteries

S.S Ching, Prof M.J. McMahon (2006) Surgical Endoscopy

Abstract

Background: Torsional mode ultrasonic coagulating shears have recently been developed for
endoscopic and conventional surgery. The current investigation was conducted to compare the
effectiveness of this device with the more established linear mode shears for the sealing of
medium- to large-sized arteries.

Methods: Porcine carotid arteries were prepared in vitro. Each vessel was coagulated and cut
by both torsional and longitudinal mode devices at different sites. The burst pressure of each
seal was then measured by placing a catheter secured with a ligature into the open end of the
vessel. The catheter was connected to a pressure transducer and saline was gradually infused
until there was leakage from the sealed end. The acute burst pressure was defined as the peak
pressure recorded. Statistical differences were evaluated by Mann-Whitney U test.

Results: A total of 104 seals were made on 50 vessels, 52 with each device. Median burst
pressures for arteries 3.3–4.2 mm and 4.3–5.2 mm in diameter were 321 and 354 mmHg for
torsional mode shears compared with 479 and 317 mmHg for linear mode shears (p = 0.193
and 0.579, respectively). For larger arteries (5.3–7.4 mm in diameter), the torsional mode
shears achieved significantly higher seal strength than the linear mode shears (median burst
pressure = 378 vs. 203 mmHg, p = 0.027). There was no significant correlation between the
burst pressure and the vessel size for the torsional mode device (r = )0.109, p = 0.441).
However, the burst pressure was adversely affected by increased vessel size for the linear
mode device (r = )0.552, p = 0.000).

Conclusions: Our study demonstrates that both linear and torsional mode ultrasonic
coagulating shears can achieve secure haemostasis of vessels up to 5.2 mm in diameter, with
median acute bursting pressures well above physiologic systolic blood pressure. The Torsional
mode shears have the extended ability to coagulate larger-sized vessels up to 7.4 mm in
diameter with the same degree of confidence. On the other hand, increasing vessel size is
correlated with lower burst pressures for the linear mode device.