Flexible endoscopes have become increasingly preferred as the instrument of choice for performing certain types of surgical procedures, performing certain diagnostic procedures, or rendering therapy to internal sites within a patient's body. Since the endoscope can be inserted through a natural body opening or through a relatively small transcutaneous incision and advanced to the site where the medical procedure is to be performed, the use of an endoscope exposes the patient to much less trauma and risk of infection than a conventional surgical technique that would otherwise be required to access the internal site. The use of a flexible endoscope is so minimally invasive that some medical procedures can be done in a clinic with the device, and the patient released within an hour or two after a procedure has been completed.
Depending upon the internal site where a medical procedure will be performed with a flexible endoscope, it may be necessary to remotely bend the distal tip of the endoscope, for example, to facilitate advancing the endoscope through a curving body lumen or to position the distal tip at a desired orientation to implement the medical procedure with the endoscope. Although the term “flexible” endoscope indicates that the endoscope is not rigid, some mechanism must be provided to actually bend the flexible distal portion of the endoscope in a desired direction and by a required amount. The conventional approach for bending the distal tip employs wires that extend coaxially along the flexible endoscope, so that when the proximal end of a wire is pulled relative to the shaft of the flexible endoscope, the distal end bends in the direction of that wire. A wire running down the opposite side of the flexible endoscope is then pulled to straighten the distal tip or bend it in the opposite direction. If four of these coaxial wires extend down the length of the flexible endoscope to enable bending of its distal tip in each direction about orthogonal X and Y axes, the wires add substantially to the diameter of the device. However, there is a significant advantage in using a flexible endoscope having a diameter on the order of 1 mm or less. But such a small diameter flexible endoscope can generally not be achieved if the conventional coaxial bending wire arrangement is used to bend the distal tip. Accordingly, a different approach is required that provides the desired small diameter, yet enables the distal tip to be selectively bent in any of four orthogonally different directions.