Generally, an endoscope is a medical device for insertion into a body passageway or cavity that enables an operator, positioned at a remote external location, to view and/or perform certain surgical procedures at a site internal to the patient's body. As is known, endoscopes may be either rigid or flexible, the later type providing either active or passive deflection of at least a portion thereof to facilitate reaching the internal site of interest. In general, a flexible endoscope includes a long flexible tubular member equipped with, for example, a miniature viewing device, an illumination device, and/or one or more working channels. The endoscope has a proximal end that remains external to the patient and a distal end having an endoscope tip for insertion into a body cavity of the patient.
Passive flexible endoscopes simply allow for the tubular member to deflect as it is inserted into various portions of the body (typically following the pathway of an elongated organ or cavity. Active flexible endoscopes on the other hand, allow the user to manipulate controls (typically at the proximal end of the endoscope) to cause at least a portion of the endoscope (typically the distal end) to deflect or flex in one or more directions. It is these active-type flexible endoscopes with which the present invention is most concerned.
A typical flexible endoscope 110 is illustrated in FIG. 8. An illumination device of endoscope 110 typically includes a lens 112 at an endoscope tip 114. Lens 112 is positioned proximate to a viewing device 116. Light emanates from lens 114 to enable viewing device 116 to capture images in the body cavity and electrically or optically transmit the images through a tubular body 118 of endoscope 110 for display at an external monitor. Once viewing the transmitted images, the endoscope operator may insert one or more surgical instruments through one or more working channels 120 to perform an endoscopic procedure at the internal body cavity site. These endoscopic procedures may include, for example, snare resections, injections, or biopsies of particular internal areas of the patient's body. Alternately, endoscope 110 may be used simply for viewing.
If flexible endoscope 110 is of the active type, at least one control wire 122 extending from a deflection control located at the proximal end to a distal end may be embedded within tubular body 118. Control wire 122 may be provided with a guide along at least a portion thereof in order to (1) keep the control wire 122 in place and prevent chaffing thereof by contact with other components within tubular body 118, and (2) provide a compression member inside tubular body 118 which prevents collapse of the shaft when control wire stress is applied.
In certain known devices, the wire guide comprises a coiled stainless steel wire to form a flexible tube around each control wire. A problem exists with these stainless steel coil wire guides in that the coil shape can expand during compression. This can result in a loss of deflection at the active deflection section of the endoscope. Another problem with such stainless steel coil wire guides is that they do not generally add significant stiffness and/or column strength to the endoscope shaft, do not reduce loss of deflection over time, and do not improve endoscope shaft rigidity for facilitated patient introduction.
In other prior art devices, continuous-walled tubes are used as the guides for the control wires. In traditional designs, these continuous-walled tubes are formed from stainless steel. More recent designs, such as those disclosed in U.S. Pat. No. 5,938,588, have formed such continuous-walled tubes from shape memory alloy materials. However, designs incorporating such continuous-walled tubes are only used effectively in applications which have a large bend radius. This is true because continuous-walled tubes can kink very easily, have no resilience (in the case of stainless steel tubes) or limited resilience (in the case of shape memory alloy materials), and can fatigue and permanently deform, thereby shortening the working life of the endoscope.
What is desired, therefore, is a control wire guide for use in a flexible endoscope the use of which does not result in a loss of deflection at the active deflection section of the endoscope, which adds stiffness and/or column strength to the endoscope shaft, which causes a reduction in loss of deflection over time as compared to known designs, which improves endoscope shaft rigidity for facilitated patient introduction, which can be used effectively in applications which have a small bend radius, which does not kink very easily, which has high resilience, and which does not fatigue and permanently deform, thereby shortening the working life of the endoscope.