Surgical instruments with torsion spine drive arrangements

1. A surgical instrument, comprising:

(a) an elongate shaft defining a central axis;

(b) an end effector coupled to the elongate shaft, wherein the end effector comprises:

(i) a first jaw, and

(ii) a second jaw configured to cooperate with the first jaw to clamp and staple tissue with a plurality of staples;

(c) a firing member actuatable longitudinally along the central axis to fire staples into tissue clamped by the end effector, wherein the firing member includes a flexible spine that extends longitudinally and is radially offset from the central axis; and

(d) a rotary driver extending longitudinally along the central axis and configured to rotatably engage the flexible spine to actuate the firing member longitudinally.

2. The surgical instrument of claim 1 , wherein the flexible spine includes a plurality of vertebrae moveably coupled together.

3. The surgical instrument of claim 2 , wherein each vertebra of the plurality of vertebrae includes a vertebra body having a proximal end and a distal end, wherein the proximal end of each vertebra is configured to be moveably coupled with the distal end of another vertebra.

4. The surgical instrument of claim 3 , wherein the vertebrae are movably supported relative to each other by a flexible coupler that is coupled to a portion of the firing member and extends through each the vertebra.

5. The surgical instrument of claim 4 , wherein each vertebra further comprises a hollow passage extending through the vertebra body between the proximal end and the distal end, wherein the hollow passage is configured to permit the flexible coupler to extend therethrough.

6. The surgical instrument of claim 5 , wherein the vertebra body includes a recess and a projection, wherein the recess is positioned on one of the proximal end or the distal end of the vertebra body and the projection is positioned on the other of the proximal end or the distal end.

7. The surgical instrument of claim 6 , wherein the projection includes a convex projection.

8. The surgical instrument of claim 7 , wherein the recess includes a concave recess sized and shaped to matingly engage the concave recess of an adjacent vertebra.

9. The surgical instrument of claim 7 , wherein the vertebra further includes a tooth configured to interface with the rotary driver.

10. The surgical instrument of claim 9 , wherein the rotary driver comprises:

a rotary body; and

a helical driver on an external surface of the rotary body, wherein the helical driver is configured to engage the tooth of the vertebra.

11. The surgical instrument of claim 10 , wherein the tooth includes a helical surface configured to engage the helical driver, wherein the helical surface comprises two different pitches.

12. The surgical instrument of claim 4 , further comprising a vertebra biaser configured to apply a continuous compression force to the plurality of vertebrae thereby keeping each of the vertebrae in movable contact with each other.

13. The surgical instrument of claim 4 , wherein the firing member is actuatable longitudinally through a firing stroke from a starting position to an ending position, wherein the flexible coupler is configured to retract the firing member from a position that is distal to the starting position by applying retraction motions to the flexible coupler.

14. The surgical instrument of claim 13 , further comprising an articulation joint positioned proximal to the end effector and configured to enable the end effector to articulate relative to the elongate shaft, wherein the articulation joint comprises an articulation joint length, wherein the plurality of vertebra define a vertebrae length that is greater than or equal to the articulation joint length plus a distance from the starting position to the ending position of the firing member.

15. The surgical instrument of claim 14 , further comprising:

a sleeve extending from a proximal end of the end effector and spanning the articulation joint, wherein the sleeve is axially movable relative to the end effector and is configured to slidably support a portion of the plurality of vertebrae that spans the articulation joint.

16. A surgical instrument, comprising:

(a) an elongate shaft;

(b) an end effector having first and second jaws configured to cooperate to clamp and staple tissue with a plurality of staples;

(c) an articulation joint that couples the end effector with the elongate shaft and is configured to permit articulation of the end effector relative to the elongate shaft;

(d) a rotary driver rotatably supported within the end effector; and

(e) a firing member actuatable longitudinally through the end effector to fire staples into tissue clamped by the end effector, wherein the firing member includes a longitudinally-segmented spine extending proximally from a distal portion of the firing member, wherein the longitudinally-segmented spine is configured to threadedly engage the rotary driver such that rotation of the rotary driver causes axial drive motion of the firing member, and wherein the longitudinally-segmented spine is flexible to accommodate articulation of the end effector.

17. The surgical instrument of claim 16 , wherein the longitudinally-segmented spine comprises a series of vertebrae, wherein the vertebrae are movably supported relative to each other by a flexible coupler.

18. The surgical instrument of claim 17 , wherein the rotary driver comprises a helical thread comprising at least two different pitches.

19. The surgical instrument of claim 17 , further comprising a biaser configured to apply a continuous compression force to the series of vertebrae thereby keeping each of the vertebrae in movable contact with one another.

20. A surgical instrument, comprising:

(a) an elongate shaft;

(b) an end effector coupled to the elongate shaft by an articulation joint, wherein the articulation joint is configured to facilitate selective articulation of the end effector relative to the elongate shaft, and wherein the surgical end effector comprises:

(i) a first jaw, and

(ii) a second jaw configured to cooperate with the first jaw to clamp and staple tissue with a plurality of staples;

(c) a firing member supported for axial travel within the end effector between a starting position and an ending position, wherein the firing member comprises:

(i) an upper flexible spine, and

(ii) a lower flexible spine; and

(d) a rotary driver, wherein the rotary driver is configured to rotatably engage each of the upper flexible spine and the lower flexible spine and thereby actuate the firing member longitudinally between the starting position and the ending position.