A medical device includes a flexible member extending from a handle at a proximal end to a distal end sized and shaped for insertion to a target position in a living body and having a first channel extending longitudinally therethrough in combination with an elongated rotation tube positioned in the first channel and being rotatable relative to the flexible member and a rotation drive device at a distal end of the rotation tube, a proximal end of the rotation drive device being permanently attached to the rotation tube, a distal end of the rotation drive device having a first protrusion extending distally therefrom and a drive element having a substantially cylindrical shape with a groove on an inner wall thereof mating with the first protrusion of the rotation drive device, the drive element configured to transmit rotational movement of the rotation tube to an end effector connected to a distal end thereof to rotate the rotation tube relative to the flexible member.
