It is well known that one can treat various types of lesions including hemorrhoids and esophageal varices by ligation. The object of ligation is to position an elastic cord, or ligating band, around the lesion to stop circulation through the tissue and allow the tissue to die whereupon the body sloughs off the dead tissue. One instrument for facilitating the placement of a single ligating band or set of bands includes, at its distal end, a ligating band dispenser comprising two rigid, concentric tubes. The tubes can slide with respect to each other under the control of a trigger mechanism at the proximal end of the instrument. A rigid endoscope having internal passages forming a suction path and a light path interconnect the trigger mechanism and dispenser. The dispenser inner tube can be loaded with a set of one or more elastic rings or ligating bands. A separate stopper bar attaches to the instrument to prevent premature dispensing. When the instrument is located proximate a lesion, a surgeon removes the stopper bar and applies suction to draw tissue into the hollow passage at the distal end of the dispenser. Pulling on the trigger retracts the inner tube. The larger diameter of the outer tube engages the ligating band so the band cannot displace with the inner tube. As the inner tube is withdrawn from the ligating band, it slides off the inner tube and elastically contracts onto the tissue.
Another instrument includes a ligating band dispenser with an inner tube that moves with respect to an outer tube to dispense a ligating band. This dispenser is oriented at right angles to the rigid endoscope and includes a structure for moving the inner tube of the dispenser in this configuration.
A third similar dispenser approach includes an inner tube that moves axially with respect to an outer tube at the distal end of the instrument. The outer tube attaches axially onto the distal end of the endoscope. An operating mechanism in the form of a pull wire with a weighted handle maintains tension on the inner tube so that it does not displace axially outwardly while the instrument is being positioned. For some applications it is suggested that the endoscope structure be inserted through an overtube to prevent premature dispensing. Suction can be applied to draw tissue into the central aperture of the dispenser formed by the inner tube. Then a surgeon pulls the handle and retracts the inner tube axially past the distal end of the outer tube to force the ligating band of the instrument onto the tissue.
Each of the foregoing instruments dispenses a single ligating band or a single set of ligating bands at a single location. None suggests dispensing ligating bands at discrete locations. These instruments apparently would have to rely on a surgeon's sense of touch in order to displace the inner tube by an incremental distance corresponding to the thickness of a stretched ligating band to deposit a plurality of bands at different sites. That would be very difficult to accomplish.
Indeed, when it was desired to deposit ligating bands at different sites, the common practice was to load and dispense one band and to withdraw the entire instrument from the patient and load a new ligating band onto the inner tube each time. Loading ligating bands onto an instrument requires special tools and can be time consuming, particularly if the special tooling must be available to install each ligating band individually while the instrument is withdrawn. Each of these instruments requires some structure, such as special stoppers or overtubes, for preventing the premature dispensing of the ligating band. Consequently, none of these instruments is readily adaptable for dispensing ligating bands at different sites without withdrawing the instrument after each individual site is ligated.
Another device, a multiple ligating band dispenser for ligating instruments includes interfitted inner and outer structures that support a plurality of ligating bands at axially spaced locations. Retraction of the inner structure dispenses one ligating band. Extension of the inner structure advances the remaining ligating bands distally, axially so the next retraction dispenses another ligating band. This ligating band dispenser overcomes some but not all of the undesirable characteristics of single-band dispensers. For example, prior art single-band dispensers can eject a ligating band inadvertently if, during placement, tissue at the distal end of the dispenser, rather than the physician, moves the distal edge of the movable tube. The multiple band dispenser overcomes this problem by using a spring to bias the movable tube to a distal position. However, the use of the spring increases the force that must be used during the dispensing operation. Also, the distal edge of the movable tube is the most distal part of the dispenser. During placement, this edge engages the lesion to form a vacuum seal thereby allowing the lesion to be withdrawn into the lumen of the endoscope. When the movable tube moves proximally during the dispensing operation, the vacuum seal can break thereby enabling the lesion to pull away from the dispenser.
In one attempt at dispensing a plurality of ligating bands individually and sequentially, a support, coaxially attached to the distal end of an endoscope, carries the plurality of ligating bands at axially spaced positions along an exterior surface. There are two concentric tubes with grooves inside the outer tube. The elastic ligating bands are positioned between the tubes and within the grooves so that rotation of the outer tube by means of a screw mechanism advances all the bands. This allows the bands to be sequentially advanced off the end of the dispenser. In another embodiment there are two concentric tubes, the inner being rigid and the outer being a flexible fabric. The bands are arranged on the outer surface of the fabric tube separated by small protrusions forming grooves on which the bands rest. The distal edge of the fabric is folded over the distal edge of the rigid tube so that it may be pulled proximally inside the rigid tube. A cable is provided to pull the fabric tube inward, causing the bands to be sequentially released from the end of the device. Both advance all the ligating bands simultaneously. Due to the strong elastic force applied by the bands on the housing and the friction between the bands and the housing, moving all bands at the same time requires significant pull force. In addition, moving all the bands simultaneously increases the likelihood of inadvertently firing two or more bands simultaneously.
Another attempt for dispensing a plurality of ligating bands individually and sequentially uses a support, coaxially attached to the distal end of an endoscope, and carries the plurality of ligating bands at axially spaced positions along an exterior surface. One or more displacement filaments are looped around each band; each filament then loops over the distal edge of the dispenser where it is secured. The other end of each filament runs beneath the band, over the distal edge of the dispenser and joins with a pull wire which exits the proximal end of the endoscope. When a physician moves the pull wire a certain distance proximally, the filaments sequentially advance each band off the distal edge of the dispenser, releasing the securing means as the band slides off the distal end of the dispenser. Various means are described to enable a single pull wire to sequentially advance multiple sets of filaments.
This approach overcomes some of the drawbacks of earlier devices. In treating lesions of the esophagus or other difficult to approach structures, it is desirable to have a sufficient number of ligating bands to assure completion of the procedure without the necessity of removal and reinsertion of the endoscope. Although this device can deliver multiple bands, it has some drawbacks. Each band has one or a pair of filaments used for advancing the band over the distal edge of the structure and onto the tissue. A complex attachment harness is used to assure that the series of loops of filaments is displaced sequentially to release only one band at a time from the distal end. Additionally, when the number of bands increases, the assembly labor and manufacturing complexity of assembly of the device becomes significant, and increases considerably with increasing numbers of bands. In addition, the displacement filaments all run though the working channel of the endoscope, and the small diameter of this channel limits the number of filaments. Additionally the filaments may limit the suction and obstruct other functions such as delivery of fluid or other devices through the working channel. The large number of filaments significantly obstructs drawing of tissue into the ligating structure and limits visibility through the end of the device.