The articulatable member includes a distal end, a proximal end, an actuating member, and a restraining member. The actuation member extends from the proximal end to the distal end. The actuating member transmits force to flex the articulatable member from the neutral position. The restraining member extends from the proximal end to the distal end. The restraining member may have opposing ends that are secured to the distal end and the proximal end. In one embodiment, the restraining member follows a helical path along at least a portion of the articulatable member from the proximal end to the distal end. In another embodiment, the actuating member follows a helical path along at least a portion of the articulatable member.関節運動可能部材は、遠位端部と、近位端部と、作動部材と、拘束部材とを含む。作動部材は、近位端部から遠位端部に延びる。作動部材は、関節運動可能部材を中立位置から屈曲させるために力を伝達する。拘束部材は、近位端部から遠位端部に延びる。拘束部材は、遠位端部と近位端部とに固定される互いに対向する端部を有し得る。一実施形態において、拘束部材は、近位端部から遠位端部に関節運動可能部材の少なくとも一部分に沿った螺旋経路を辿る。別の実施形態において、作動部材は、関節運動可能部材の少なくとも一部分に沿った螺旋経路を辿る。
