A medical instrument that includes an instrument shaft having proximal and distal ends; a tool for performing a medical procedure; a control handle; a distal motion member for coupling the distal end of the instrument shaft to the tool; a proximal motion member for coupling the proximal end of the instrument shaft to the control handle; actuation means extending between the distal and proximal motion members for coupling motion of the proximal motion member to the distal motion member for controlling the positioning of the tool; a control tube through which the instrument shaft and tool extend; the control tube including, along the length thereof, a curved section; the curved section of the control tube, upon rotation thereof, providing an additional degree of freedom by displacing the tool out of a plane defined by the curved section of the control tube.
