Ligation is a medical procedure whereby the physician ties off or mechanically constricts a piece of body tissue with an encircling ligature such as a suture, clip, or elastic band. The purpose of ligation is to impede or obstruct the flow of blood, fluids, and other bodily materials through the tissue. For example, the physician can remove target tissue by ligating it to obstruct all circulation through the target tissue, thereby causing the tissue to die and slough off.
For ligating tissue inside a body cavity, orifice, or lumen, physicians often use an endoscope to access the target tissue and ligate it. In one such form of endoscopic ligation, the physician uses the endoscope to position a stretched elastic band over the target tissue and then release the band onto the tissue so that the band contracts and catches the tissue. The inward pressure of the elastic band constricts the target tissue.
Ligating instruments have been the subject of a number of patents, including U.S. Pat. No. 5,269,789 to Chin et al.; U.S. Pat. No. 5,356,416 to Chu et al.; U.S. Pat. No. 5,398,844 to Zaslavsky et al.; U.S. Pat. No. 5,857,585 to Tolkoff et al.; U.S. Pat. No. 5,853,416 to Tolkoff; U.S. Pat. No. 5,913,865 to Fortier et al.; U.S. Pat. No. 6,235,040 to Chu et al.; and U.S. Pat. No. RE 36,629 to Zaslavsky et al. The disclosures of these prior U.S. patents are expressly incorporated by reference herein.
A number of previous ligating instruments have relied on deployment of the elastic bands by a trigger wire or string that must be threaded through the lumen of an endoscope. Once the wire or string is threaded through the endoscope lumen, the user must then tie or otherwise connect the free end of the wire or string to an actuator mechanism. The process of threading the wire or string and attaching it to the actuator mechanism adds additional steps in setting-up the instrument for use and can be cumbersome. It can also lead to error and improper calibration of the device.