Tissue resecting systems and methods
A tissue resecting system includes an assembly having first and second tubular members. An electrical motor drive and controller moves the second member to resect tissue received in a window of the first member. A tachometer sends motor drive rotational signals to the controller, and the controller modulates a motor voltage in response to the signals from the tachometer both to drive the second member at a predetermined speed and to calculate resistance to driving the second member at the predetermined speed.
1. A tissue resecting device, comprising:
an assembly of tubular first and second members, the second member having a resecting element at a distal end thereof;
a handle;
a motor drive system carried in the handle and a controller configured for moving the second member across a window of the first member;
the motor drive system including a motor and a motor shaft driving a rotation-to-linear motion conversion mechanism, wherein a distal edge of the second member moves back and forth across the window of the first member from a window open position to a window closed position;
wherein the controller includes an algorithm configured to stop reciprocation of the second member with the distal edge of the second member at a stop position in which the tissue-receiving window is partially open;
wherein the rotation-to-linear motion conversion mechanism includes a rotatable drive collar; and
a microswitch, wherein the microswitch engages an engagement feature of the drive collar once each revolution of the drive collar;
wherein the microswitch sends an electrical signal to the controller for each instance the microswitch engages the engagement feature;
wherein the controller is configured to de-energize the motor at a point Y between a reference point in which the microswitch engages the engagement feature and the stop position.
2. The tissue resecting device of claim 1 , wherein the engagement feature is an indent in the drive collar.
3. The tissue resecting device of claim 1 , wherein the controller is configured to calculate point Y based on a calculated speed of rotation of the drive collar and calculated resistance of driving the second member.
4. The tissue resecting device of claim 3 , wherein the controller incudes an algorithm responsive to the calculated resistance to de-energize the motor at point Y to permit momentum to move the second member to the stop position.
5. The tissue resecting device of claim 4 , wherein the algorithm is configured to compare the calculated resistance to a look-up table of known resistances correlated with a momentum parameter related to stopping movement of the second member.
6. The tissue resecting device of claim 1 , wherein the drive collar is rotatable with the motor shaft.
7. The tissue resecting device of claim 6 , wherein the drive collar includes an arcuate slot engaging a pin secured to the second member.
8. The tissue resecting device of claim 7 , wherein the pin and the second member reciprocate as the drive collar rotates.
9. The tissue resecting device of claim 1 , wherein the controller is configured to stop the distal edge of the second member at the stop position for coagulating tissue.
10. The tissue resecting device of claim 9 , wherein the first and second members include opposing polarity electrodes for selectively resecting and coagulating tissue.
11. A tissue resecting device, comprising:
an assembly including an outer member having a tissue-receiving window and an inner member movably positioned within the outer member, the inner member having a resecting element at a distal end thereof;
a handle;
a motor drive system carried in the handle and a controller configured for moving the resecting element of the inner member across the tissue-receiving window of the outer member to resect tissue;
the motor drive system including a motor and a motor shaft driving a rotation-to-linear motion conversion mechanism to reciprocate the inner member through at least one full distal and proximal reciprocation stroke via 360 degree rotation of the rotation-to-linear motion conversion mechanism in a first rotational direction, wherein a distal edge of the resection element moves back and forth across the window of the outer member from a window open position to a window closed position;
wherein the controller includes an algorithm configured to stop reciprocation of the inner member with the distal edge of the resecting element at a stop position in which the tissue-receiving window is partially open;
wherein the rotation-to-linear motion conversion mechanism includes a rotatable drive collar; and
a microswitch, wherein the microswitch engages an indent in the drive collar once each revolution of the drive collar;
wherein the microswitch sends an electrical signal to the controller for each instance the microswitch engages the indent;
wherein the controller is configured to de-energize the motor at a point Y between a reference point in which the microswitch engages the indent and the stop position.
12. The tissue resecting device of claim 11 , wherein the controller is configured to calculate point Y based on a calculated speed of rotation of the drive collar and calculated resistance of driving the inner member, and wherein the controller incudes an algorithm responsive to the calculated resistance to de-energize the motor at point Y to permit momentum to move the inner member to the stop position.