Surgical cutting device with gear mechanism

1. A single-use tissue resecting device comprising:

an elongate handle carrying a motor having a drive shaft configured to rotate about a longitudinal axis, the motor drive shaft configured to rotate a ring gear and alternatively engage a first set of pinion gears and a second set of pinion gears;

wherein the ring gear comprises a plurality of inwardly projecting gear teeth that extend less than 180° around the ring gear;

wherein each gear of the first and second sets of pinion gears rotates about an axis aligned parallel with said longitudinal axis;

wherein each of the first and second sets of pinion gears are intermediate the ring gear and a central output gear of an output shaft aligned parallel with the longitudinal axis;

wherein rotation of the ring gear in a single rotational direction causes the first set of pinion gears to rotate the output shaft in a first rotational direction and the second set of pinion gears to rotate the output shaft in a second rotational direction to provide rotational oscillation of the output shaft; and

a cutting member coupled to the output shaft such that rotation of the motor drive shaft in the single rotational direction causes rotational oscillation of the cutting member.

2. The tissue resecting device of claim 1 , wherein the plurality of inwardly projecting gear teeth includes one or more gear teeth extending less inwardly than a remainder of the gear teeth for smooth meshing of the plurality of inwardly projecting gear teeth with the first set of pinion gears and the second set of pinion gears during rotation of the ring gear.

3. The tissue resecting device of claim 1 , wherein a gear mechanism comprises the first and second sets of pinion gears, the ring gear, and the output shaft, wherein the gear mechanism is configured to rotationally oscillate the output shaft and cutting member in a sequence of 1 to 8 revolutions in each of the first rotational direction and the second rotational direction.

4. The tissue resecting device of claim 3 , wherein the motor and the gear mechanism are configured to rotate the output shaft and cutting member in a range of 100 RPM to 5,000 RPM in each of the first rotational direction and the second rotational direction.

5. The tissue resecting device of 26 , wherein the cutting member comprises an inner sleeve having an inner window, the inner sleeve rotatably positioned within an outer sleeve having an outer window, and rotation oscillation of the cutting member comprises rotational oscillation of the inner sleeve within the outer sleeve.

6. The tissue resecting device of claim 5 , further comprising an aspiration lumen extending through the inner sleeve.

7. The tissue resecting device of claim 6 , wherein the aspiration lumen extends to a port that is located distally of the gear mechanism.

8. The tissue resecting device of claim 5 , wherein in a window-open position the inner window aligns with the outer window and in a window-closed position, the inner window is not aligned with the outer window.

9. The tissue resecting device of claim 8 , wherein the inner sleeve comprises an outflow opening located on an opposite circumferential side of the inner window such that the outflow opening permits a fluid path into the inner sleeve during non-alignment of the inner window and the outer window.

10. The tissue resecting device of claim 5 , wherein the gear mechanism is carried in a housing that is coupled to the inner sleeve and the outer sleeve, and the housing comprises a detachable component of the handle.

11. The tissue resecting device of claim 3 , wherein the gear mechanism is carried in a housing that comprises a detachable component of the handle.

12. The tissue resecting device of claim 1 , wherein the motor is a DC motor.

13. A single-use tissue resecting device comprising:

an elongate handle carrying a motor with a drive shaft that rotates around a longitudinal axis;

a gear mechanism coupled to the motor including a partial ring gear adapted to rotate around said longitudinal, a central output gear carried by an output shaft aligned with said longitudinal axis, and at least one pinion gear intermediate the ring gear and the output gear;

wherein the partial ring gear comprises a plurality of inwardly projecting gear teeth that extend less than 180° around the ring gear;

wherein the at least one pinion gear rotates about an axis parallel to the longitudinal axis; and

a cutting member coupled to the output shaft;

wherein rotation of the ring gear in a first rotational direction causes a pinion gear to rotate in a second rotational direction, wherein the gear mechanism causes rotational oscillation of the output shaft and cutting member; and

wherein the at least one pinion gear provides a gear reduction.

14. The tissue resecting device of claim 13 , wherein the at least one pinion gear comprises a first set of pinion gears and a second set of pinion gears.

15. A single-use tissue resecting device comprising:

an elongate handle carrying a motor with a drive shaft that rotates around a longitudinal axis;

a gear mechanism coupled to the motor;

a cutting member coupled to an output shaft such that rotation of the drive shaft in a single rotational direction causes rotational oscillation of the cutting member;

wherein the gear mechanism comprises a partial ring gear adapted to engage a pinion gear assembly intermediate the ring gear and an output gear of the output shaft aligned parallel with said longitudinal axis, wherein the partial ring gear comprises a plurality of inwardly projecting gear teeth that extend less than 180° around the ring gear;

wherein the ring gear, the pinion gear assembly and the output gear are positioned in a plane transverse to said longitudinal axis to provide a compact assembly; and

wherein rotation of the ring gear in the single rotational direction rotates the output shaft in alternating first and second rotational directions to provide rotational oscillation of the output shaft and cutting member.