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Various torque-limiting screwdrivers, systems, and methods are disclosed. The screwdriver can include a body supporting a motor configured to rotate a screw engaged with the screwdriver. The screwdriver can include a controller configured to implement torque-limiting functionality, such as by monito

Various torque-limiting screwdrivers, systems, and methods are disclosed. The screwdriver can include a body supporting a motor configured to rotate a screw engaged with the screwdriver. The screwdriver can include a controller configured to implement torque-limiting functionality, such as by monitoring the amount of torque applied to the screw and reducing or stopping rotation of the screw when certain torque-limiting criteria are met. Some embodiments include a threshold point, after which the torque-limiting functionality can be engaged. Some embodiments include a slowdown point, after which the rotational speed of the screw is reduced.

대표청구항 ▼

1. A surgical torque-limiting screwdriver comprising: a housing;a motor positioned in the housing and configured to receive electrical power from a power source;a drive head positioned at a distal end of the screwdriver, the drive head configured to receive a bit that engages a screw and to be rotat

1. A surgical torque-limiting screwdriver comprising: a housing;a motor positioned in the housing and configured to receive electrical power from a power source;a drive head positioned at a distal end of the screwdriver, the drive head configured to receive a bit that engages a screw and to be rotated by the motor so as to enable the screwdriver to drive the screw into a bone;a current sensor that samples electrical current drawn by the motor during operation of the motor;a controller that, during driving of the screw into the bone: receives signals from the current sensor indicative of the electrical current drawn by the motor;uses the signals to determine a plurality of driving torque values, each of the plurality of driving torque values indicative of an amount of torque that the screwdriver is applying to the screw during a respective time period t;stores at least the three most-recent of the plurality of driving torque values in a memory;compares each of the driving torque values that occur after a deadband with a threshold torque value;prevents engagement of a torque-limiting function until at least one of the driving torque values that occur after the deadband is greater than or equal to the threshold torque value;permits engagement of the torque-limiting function in response to at least one of the driving torque values that occur after the deadband being greater than or equal to the threshold torque value;reduces the rotational speed at which the screwdriver drives the screw in response to at least one of the driving torque values that occur after the deadband being greater than or equal to the threshold torque value; andengages the torque-limiting function in response to determining that: engagement of the torque-limiting function is permitted; andat least three of the driving torque values that occur after the deadband consecutively decrease;wherein the torque-limiting function stops the driving of the screw by the screwdriver. 2. The surgical torque-limiting screwdriver of claim 1, further comprising an override input that sends a signal to the controller, the override input enabling a user to override the torque-limiting function. 3. The surgical torque-limiting screwdriver of claim 2, wherein activation of the override input rotates the screw a certain amount. 4. The surgical torque-limiting screwdriver of claim 3, wherein the certain amount is approximately ¼ turn. 5. The surgical torque-limiting screwdriver of claim 2, wherein activation of the override input disengages the torque-limiting function for a period of time. 6. The surgical torque-limiting screwdriver of claim 5, wherein the period of time is less than 1 minute. 7. The surgical torque-limiting screwdriver of claim 2, wherein the override input comprises a button. 8. The surgical torque-limiting screwdriver of claim 1, wherein the deadband is an amount of time. 9. The surgical torque-limiting screwdriver of claim 8, wherein the deadband is at least 50 ms. 10. The surgical torque-limiting screwdriver of claim 1, wherein the deadband is an amount of rotations of the screw. 11. The surgical torque-limiting screwdriver of claim 9, wherein the deadband is at least 5 rotations. 12. The surgical torque-limiting screwdriver of claim 1, wherein the time period t is approximately 10 ms. 13. The surgical torque-limiting screwdriver of claim 1, wherein the rotational speed is reduced to less than or equal to 900 rpm. 14. The surgical torque-limiting screwdriver of claim 1, wherein the rotational speed is reduced by a factor of approximately 4. 15. The surgical torque-limiting screwdriver of claim 1, wherein the threshold torque value is at least 15 N-cm. 16. The surgical torque-limiting screwdriver of claim 1, further comprising the power source, and wherein the power source comprises a battery in the housing. 17. A torque-limiting screwdriver comprising: a housing;a motor positioned in the housing and configured to receive electrical power from a power source;a drive head positioned at a distal end of the screwdriver and configured to receive a bit that engages a screw;a transfer assembly connecting the motor and the drive head such that the drive head is rotatable by the motor so as to enable the screwdriver to insert the screw into a bone;a sensor that detects electrical current drawn by the motor during operation of the motor;a controller that receives signals from the sensor indicative of the electrical current drawn by the motor and uses such signals to determine a plurality of values of the torque applied to the screw during the insertion of the screw;the screwdriver configured to stop rotation of the screw in response to a torque-limiting condition being satisfied; andthe screwdriver further configured to rotate the screw at a first speed during a first stage of the screw insertion and to rotate the screw at a second speed during a second stage of the screw insertion, the second stage being after the first stage and the second speed being less than half of the speed of the first stage, thereby increasing the insertion time for the screwdriver to insert the screw into the bone and reducing the angular momentum of the screw during the second stage. 18. The torque-limiting screwdriver of claim 17, wherein the torque-limiting condition is satisfied when the controller determines that at least four of the plurality of values consecutively decrease. 19. The torque-limiting screwdriver of claim 17, wherein the torque-limiting condition is satisfied when a deadband has expired and the controller has detected an inflection point in the plurality of values. 20. The torque-limiting screwdriver of claim 17, wherein the first speed is greater than or equal to 3,600 rpm and the second speed is less than or equal to 900 rpm. 21. The torque-limiting screwdriver of claim 17, wherein the screwdriver changes from the first stage to the second stage when at least one of the torque values that occur after a deadband is greater than or equal to a threshold torque value. 22. The torque-limiting screwdriver of claim 17, wherein the screwdriver changes from the first stage to the second stage after a period of time has elapsed, the period of time beginning at the initial insertion of the screw into the bone by the screwdriver. 23. The torque-limiting screwdriver of claim 22, wherein the period of time is at least 150 ms.