A surgical instrument is disclosed and comprises a handle； and an elongated shaft assembly extending distally from the handle which includes an articulable portion with an articulation direction. The elongated shaft assembly comprises a first tubular member including a first flexible portion including a first plurality of slots and at least a first spine extending along a length of the first flexible portion, and a second tubular member including a second flexible portion including a second plurality of slots and at least a second spine extending along a length of the second flexible portion. The first tubular member and the second tubular member are axially fixed relative to one another at a position distal from the first flexible portion and the second flexible portion. The instrument also comprises a third tubular member including a third flexible portion with a third plurality of slots, a third spine, and a fourth spine extending along a length of the third flexible portion. The first tubular member, the second tubular member, and the third tubular member are coaxially located, and the third tubular member is rotatable relative to the first tubular member and/or the second tubular member.
