[Newly designed needle scope system for arthroscopic surgery by double-channel sheath method].

We have been studying applicational arthroscopic surgery for temporomandibular joint diseases. Reported below is a newly designed system of diagnostic/operating arthroscopy. This prototype has an external diameter of 1.7 mm. The angle of vision is 60 degrees in air and 45 degrees in water. The effective length with the outer cannula set on is either 90 mm or 50 mm. The most important achievement of this device is that it enables the usage of two types of different sized outer cannula in the same arthroscope: a round single-channel sheath (external diameter 2.0 mm) and an oval double-channel sheath (3.8 X 2.0). The single-channel sheath can easily be replaced with the double-channel sheath by using internal and external guiding needles. This device can be used not only for diagnostic arthroscopy but also for arthroscopic surgery. In particular, it has a hole for surgical device insertion which enables parallel insertion of device. This makes it easy to always observe the advancing edge of surgical device and the manipulation can therefore be greatly improved.