Ultrasonically-activated devices for endoscopic surgery

In an ultrasonically-activated device (USAD), the controlled electric curre nt is transformed into mechanical vibration in the transducer. The amplitud e of this vibration is amplified in a conical metal horn, attached to the e nd of the transducer. The shaft of the USAD houses an extension rod, which transmits the amplified vibration to the end effecter. The end effecter in the scissor-type USAD is termed the 'active blade'. The target tissue is cl amped between the active blade and an opposed tissue pad, and effective coa gulation occurs. In the USAD technique, frictional heat generated is mostly lower than boiling point, which allows collagens to denature with water an d form a glue-like material to seal the vessel. Division of the tissue is c aused mainly by 'mechanical wear' from the vibrating blade. Cavitation occu rs at the tip of the active blade. As cavitation can be traumatic and fragm ent the tissue, any contact of the tip of the active blade with important t issue should be avoided. Recent reports on the USAD's ability to achieve ha emostasis are excellent, suggesting that the cut-ends of the vessels withst and the high intraluminal pressure. However, the following four factors are considered pitfalls. the vessel could be divided before it is sufficiently occluded, due to excessive tension; the active blade could cross the vesse l incompletely; adjacent vessels could be injured with the reverse side or the tip of the active blade.