Drive mechanism for articulation of a surgical instrument

A surgical instrument includes a housing, an end effector and an elongated shaft extending therebetween. The elongated shaft includes a distal portion that is movable between aligned and articulated configurations. A pair of drive cables extends through the elongated shaft and is coupled to the distal portion such that reciprocal longitudinal motion of the drive cables induces movement of the distal portion between the aligned and articulated configurations. An articulation drive mechanism is operable to induce reciprocal longitudinal motion of the drive cables. The drive mechanism includes an actuator and a pair of torsion members that are rotatable about two distinct axes in response to movement of the actuator. A respective follower is operatively coupled to each torsion member to translate in a respective longitudinal direction in response to rotation of the torsion members, and each follower is coupled to a respective drive cable to impart translational motion thereto.