An articulatable surgical instrument comprising: an end effector to treat tissue; a shaft (1000; 1018) extending proximally from the end effector along a longitudinal axis, wherein the shaft (1000; 1018) comprises: a plurality of transverse spacer members; a first rotatable member (1004; 1020) extending through at least a portion of the plurality of transverse spacer members parallel to the longitudinal axis, wherein the first rotatable member (1004; 1020) is biased away from the longitudinal axis, and wherein a direction of the bias of the first rotatable member (1004; 1020) varies with rotation of the first rotatable member (1004; 1020); a second rotatable member (1006; 1022) extending through at least a portion of the plurality of transverse spacer members parallel to the longitudinal axis and offset from the first rotatable member (1004; 1020) along a direction perpendicular to the longitudinal axis, wherein the second rotatable member (1006; 1022) is biased away from the longitudinal shaft (1000; 1018), wherein a direction of the bias of the second rotatable member (1006; 1022) varies with rotation of the second rotatable member (1006; 1022), wherein the shaft (1000; 1018) is substantially straight when the first and second rotatable members (1004, 1006; 1020, 1022) are rotated such that the direction of the bias of the first rotatable member (1004; 1020) and the direction of the bias of the second rotatable member (1006; 1022) oppose one another, and wherein the shaft (1000; 1018) articulates in a first direction away from the longitudinal axis when the first and second rotatable members (1004, 1006; 1020, 1022) are rotated such that the direction of the bias of the first rotatable member (1004; 1020) and the direction of the bias of the second rotatable member (1006; 1022) are aligned with one another in the first direction. an end effector to treat tissue; a shaft (1000; 1018) extending proximally from the end effector along a longitudinal axis, wherein the shaft (1000; 1018) comprises: a plurality of transverse spacer members; a first rotatable member (1004; 1020) extending through at least a portion of the plurality of transverse spacer members parallel to the longitudinal axis, wherein the first rotatable member (1004; 1020) is biased away from the longitudinal axis, and wherein a direction of the bias of the first rotatable member (1004; 1020) varies with rotation of the first rotatable member (1004; 1020); a second rotatable member (1006; 1022) extending through at least a portion of the plurality of transverse spacer members parallel to the longitudinal axis and offset from the first rotatable member (1004; 1020) along a direction perpendicular to the longitudinal axis, wherein the second rotatable member (1006; 1022) is biased away from the longitudinal shaft (1000; 1018), wherein a direction of the bias of the second rotatable member (1006; 1022) varies with rotation of the second rotatable member (1006; 1022), wherein the shaft (1000; 1018) is substantially straight when the first and second rotatable members (1004, 1006; 1020, 1022) are rotated such that the direction of the bias of the first rotatable member (1004; 1020) and the direction of the bias of the second rotatable member (1006; 1022) oppose one another, and wherein the shaft (1000; 1018) articulates in a first direction away from the longitudinal axis when the first and second rotatable members (1004, 1006; 1020, 1022) are rotated such that the direction of the bias of the first rotatable member (1004; 1020) and the direction of the bias of the second rotatable member (1006; 1022) are aligned with one another in the first direction. a plurality of transverse spacer members; a first rotatable member (1004; 1020) extending through at least a portion of the plurality of transverse spacer members parallel to the longitudinal axis, wherein the first rotatable member (1004; 1020) is biased away from the longitudinal axis, and wherein a direction of the bias of the first rotatable member (1004; 1020) varies with rotation of the first rotatable member (1004; 1020); a second rotatable member (1006; 1022) extending through at least a portion of the plurality of transverse spacer members parallel to the longitudinal axis and offset from the first rotatable member (1004; 1020) along a direction perpendicular to the longitudinal axis, wherein the second rotatable member (1006; 1022) is biased away from the longitudinal shaft (1000; 1018), wherein a direction of the bias of the second rotatable member (1006; 1022) varies with rotation of the second rotatable member (1006; 1022), wherein the shaft (1000; 1018) is substantially straight when the first and second rotatable members (1004, 1006; 1020, 1022) are rotated such that the direction of the bias of the first rotatable member (1004; 1020) and the direction of the bias of the second rotatable member (1006; 1022) oppose one another, and wherein the shaft (1000; 1018) articulates in a first direction away from the longitudinal axis when the first and second rotatable members (1004, 1006; 1020, 1022) are rotated such that the direction of the bias of the first rotatable member (1004; 1020) and the direction of the bias of the second rotatable member (1006; 1022) are aligned with one another in the first direction.