Push-pull surgical instrument end effector actuation using flexible tension member
Surgical tools and related methods articulate an actuation rod assembly via an actuation tension member. A surgical tool includes an end effector, an instrument shaft assembly supporting the end effector, an actuation rod assembly drivingly coupled with the end effector, a guide surface, a flexible tension member connected to the actuation rod assembly, and an actuation portion. The actuation rod assembly is mounted to slide within the instrument shaft assembly. The flexible tension member is connected to the actuation rod assembly at a connection. The flexible tension member includes a first portion that extends distally from the connection to the guide surface, is wrapped around the guide surface, and extends proximally from the guide surface. The actuation portion is drivingly coupled with the flexible tension member and operable to articulate the tension member to articulate the actuation rod assembly to actuate the end effector.
1. A surgical tool comprising:
an actuation portion;
an end effector;
an instrument shaft assembly coupling the actuation portion to the end effector, the instrument shaft assembly being elongated along an instrument shaft axis and defining a lumen, the instrument shaft assembly including a guide surface disposed towards a distal end of the lumen;
an actuation rod assembly drivingly coupled with the end effector, the actuation rod assembly being slideably mounted within the lumen for translation relative to the instrument shaft along the instrument shaft axis; and
a flexible tension member drivingly coupling the actuation portion to the actuation rod assembly; the flexible tension member being connected to the actuation rod assembly at a connection that is longitudinally disposed between the actuation portion and the guide surface; the flexible tension member including a first portion that, from the connection, extends distally towards the guide surface, wraps around the guide surface, and extends proximally towards the actuation portion, the actuation portion being operable to increase tension in the first portion of the flexible tension member to translate the actuation rod assembly in a distal direction.
2. The surgical tool of claim 1 , wherein the flexible tension member includes a second portion extending proximally through the lumen from the connection to the actuation portion, the actuation portion being drivingly coupled with the second portion and operable to increase tension in the second portion to move the actuation rod assembly in a proximal direction.
3. The surgical tool of claim 2 , wherein:
the actuation portion is operable to rotate the instrument shaft assembly around the instrument shaft axis relative to a proximal chassis supporting the instrument shaft assembly;
the actuation rod assembly is constrained to rotate with the instrument shaft assembly around the instrument shaft axis; and
the surgical tool further comprises an isolation tube extending along the instrument shaft axis, the isolation tube being disposed between the connection and the actuation portion, the first and second portions of the flexible tension member passing through the isolation tube, the isolation tube enclosing an inter-twistable length of the first and second portions and isolating the inter-twistable length from a region of the lumen surrounding the isolation tube.
4. The surgical tool of claim 2 , wherein:
the first portion of the flexible tension member comprises a first length of cable;
the second portion of the flexible tension member comprises a second length of cable;
the surgical tool comprises a pulley that includes the guide surface;
the actuation portion is operable to move the actuation rod assembly through a range of movement relative to the pulley; and
the actuation rod assembly comprises a slot configured to accommodate the pulley throughout the range of movement.
5. The surgical tool of claim 4 , wherein the actuation rod assembly comprises a cable guide aperture through which the second length of cable extends.
6. The surgical tool of claim 1 , wherein the instrument shaft assembly comprises a first component and a second component, the first and second components being configured to accommodate insertion of the actuation rod assembly, the guide surface, and the flexible tension member into the lumen when the first and second components are uncoupled, the first and second components being configured to be joined to form the lumen.
7. The surgical tool of claim 6 , wherein:
the actuation portion is operable to move the actuation rod assembly through a range of movement relative to the guide surface;
the actuation rod assembly comprises a first guide feature that protrudes in a first direction and a second guide feature that protrudes in a second direction different than the first direction; and
the first component and the second component form a first slot sized to accommodate the first guide feature and a second slot sized to accommodate the second guide feature throughout the range of movement.
8. The surgical tool of claim 1 , wherein:
the flexible tension member comprises a drive band; and
the drive band comprises a slot through which a portion of the actuation rod assembly between the connection and the end effector extends.
9. The surgical tool of claim 8 , comprising:
a support frame having an aperture through which the portion of the actuation rod assembly between the connection and the end effector extends;
a first bearing mounted to the support frame to rotate around a guide surface axis perpendicular to the instrument shaft axis and interface with the drive band on a first side of the slot; and
a second bearing mounted to the support frame to rotate around the guide surface axis and interface with the drive band on a second side of the slot opposite to the first side of the slot,
wherein the first and second bearings include the guide surface.
10. The surgical tool of claim 8 , wherein the actuation rod assembly comprises a drive band guide aperture through which the drive band extends.
11. A method for actuating an end effector of a surgical tool, the method comprising:
supporting an end effector via an instrument shaft assembly elongated along an instrument shaft axis;
enclosing an actuation rod assembly within a lumen of the instrument shaft assembly;
guiding the actuation rod assembly during movement of the actuation rod assembly along the instrument shaft axis; and
operating an actuation portion to increase tension in a first portion of a flexible tension member drivingly coupled with the actuation rod assembly to move the actuation rod assembly in a distal direction to actuate the end effector, the first portion of the flexible tension member extending distally from the actuation portion to a guide surface, wrapped around the guide surface, and extending from the guide surface to a connection between the first portion of the flexible tension member and the actuation rod assembly.
12. The method of claim 11 , further comprising operating the actuation portion to increase tension in a second portion of the flexible tension member drivingly coupled with the actuation rod assembly to move the actuation rod assembly in a proximal direction.
13. The method of claim 12 , further comprising:
operating the actuation portion to rotate the instrument shaft assembly around the instrument shaft axis relative to a proximal chassis supporting the instrument shaft assembly;
constraining the actuation rod assembly to rotate with the instrument shaft assembly around the instrument shaft axis; and
enclosing an inter-twistable length of the first and second portions of the flexible tension member disposed between the actuation rod assembly and the actuation portion within an isolation tube to isolate the inter-twistable length from a region of the lumen surrounding the isolation tube.
14. The method of claim 12 , wherein:
the first portion of the flexible tension member comprises a first length of cable;
the second portion of the flexible tension member comprises a second length of cable;
the surgical tool comprises a pulley; and
the method further comprises:
operating the actuation portion to move the actuation rod assembly through a range of movement relative to the pulley; and
accommodating the pulley within a slot of the actuation rod assembly throughout the range of movement.
15. The method of claim 14 , further comprising guiding the second length of cable via a cable guide aperture in the actuation rod assembly through which the second length of cable extends.
16. The method of claim 11 , further comprising:
inserting the actuation rod assembly, the guide surface, and the flexible tension member into a first component of the instrument shaft assembly; and
coupling a second component of the instrument shaft assembly to the first component to enclose the actuation rod assembly, the guide surface, and a portion of the flexible tension member within the lumen of the instrument shaft assembly.
17. The method of claim 16 , further comprising:
operating the actuation portion to move the actuation rod assembly through a range of movement relative to the guide surface; and
interfacing protruding guide features of the actuation rod assembly with the instrument shaft assembly to guide movement of the actuation rod assembly relative to the instrument shaft assembly through the range of movement.
18. The method of claim 11 , wherein the flexible tension member comprises a drive band, the method further comprising accommodating a portion of the actuation rod assembly between the connection and the end effector through a slot in the drive band.
19. The method of claim 18 , further comprising:
accommodating a portion of the actuation rod extending between the connection and the end effector in an aperture of a support frame;
supporting a first bearing mounted to the support frame to rotate around a guide surface axis perpendicular to the instrument shaft axis and interface with the drive band on a first side of the slot; and
supporting a second bearing mounted to the support frame to rotate around the guide surface axis and interface with the drive band on a second side of the slot opposite to the first side of the slot,
wherein the first and second bearings include the guide surface.
20. The method of claim 18 , further comprising guiding the drive band via a drive band guide aperture of the actuation rod assembly through which the drive band extends.