Multi-mode torque drivers employing anti-backdrive units for managing pedicle screw attachments with vertebrae, and related systems and methods
Multi-mode torque drivers employing anti-backdrive units for managing pedicle screw attachments with vertebrae, and related systems and methods are disclosed. A spinal column includes vertebrae in an articulating structure protecting a spinal cord. Medical intervention may involve limiting the relative motion between vertebrae by fusing vertebrae together with mechanical assemblies, including pedicle screws attached to the vertebrae. A torque driver may be used to form the pedicle screw attachments with vertebrae. By including an anti-backdrive unit and a motor assembly enclosed within a handle body as part of a multi-mode torque driver, the user may apply sequential combinations of manual and motorized torques to the screws with high levels of tactile feedback as desired. In this manner, pedicle screw attachments may be efficiently achieved with fewer injuries to the patient and surgeon while minimizing screw attachment failures.
1. A torque driver for managing an attachment of a pedicle screw with a vertebra, comprising:
a handle body extending along an output rotational axis from a first end to a second end, the handle body including an inner surface forming an inner space connecting at least one motor control port to an output opening at the second end;
a motor assembly disposed within the inner space and configured to generate a motorized torque at an output interface of the motor assembly; and
an anti-backdrive unit disposed within the inner space and coupled to the motor assembly, the anti-backdrive unit including:
an output element disposed through the output opening,
at least one locking element, and
a housing portion statically coupled to the handle body,
wherein upon the output element of the anti-backdrive unit receiving the motorized torque from the motor assembly, the output element rotates and the output interface of the motor assembly abuts against the at least one locking element to move the at least one locking element along an inner circumferential surface of the housing portion as the at least one locking element, the output element, and the output interface commonly rotate about the output rotational axis, and
wherein upon a manual torque being applied to the first end of the handle body by a single hand of a user while the output element is coupled to a pedicle screw and the output element is free from the motorized torque, then the manual torque moves the handle body relative to the output element until the at least one locking element abuts against both the inner circumferential surface of the housing portion and a non-concentric external surface of the output element to create a mechanical interference which automatically locks the output element relative to the handle body and transmits the manual torque from the handle body to the output element.
2. The torque driver of claim 1 , wherein the motor assembly is configured to generate the motorized torque in a range from two (2) Newton-meters to ten (10) Newton-meters, and the motor assembly is configured to generate a rotational speed in a second range from fifty (50) RPM to two-hundred (200) RPM.
3. The torque driver of claim 1 , wherein the motor assembly includes at least one epicyclic gear train stage having a collective gear ratio in a range from 80:1 to 140:1.
4. The torque driver of claim 1 , further comprising at least one switch disposed at the at least one motor control port and the at least one switch comprising a plurality of non-zero speed positions.
5. The torque driver of claim 4 , wherein the at least one switch includes a rocker switch comprising the plurality of non-zero speed positions configured for the user to respectively select clockwise and counterclockwise directions of the motorized torque.
6. The torque driver of claim 1 , further comprising a battery disposed within the inner space and the battery is configured to power the motor assembly.
7. The torque driver of claim 1 , wherein the output element of the anti-backdrive unit is configured to receive the motorized torque from the output interface of the motor assembly through the at least one locking element.
8. The torque driver of claim 1 , wherein the handle body further includes an axial gripper surface connecting the first and the second ends, the axial gripper surface encloses the output rotational axis, wherein the axial gripper surface is shaped for fingers and a thumb of the single hand to be wrapped at least partially around the axial gripper surface in opposite directions with the output rotational axis disposed within an interdigital space between the thumb and at least one of the fingers of the single hand when the axial gripper surface receives the manual torque from the user.
9. A method for managing an attachment of a pedicle screw with a vertebra, comprising:
transmitting, with an output element of an anti-backdrive unit disposed within an inner space of a handle body of a torque driver, a system torque from the output element to a pedicle screw, wherein the system torque comprises one of a manual torque and a motorized torque, and the handle body extending along an output rotational axis from a first end to a second end, the handle body including an inner surface forming the inner space connecting at least one motor control port to an output opening at the second end;
generating, with a motor assembly disposed within the inner space, the motorized torque at an output interface of the motor assembly, wherein the motor assembly is coupled to the anti-backdrive unit, wherein the anti-backdrive unit includes the output element disposed through the output opening, at least one locking element, and a housing portion statically coupled to the second end of the handle body;
upon receiving the motorized torque with the output element of the anti-backdrive unit from the output interface of the motor assembly as the system torque, the output element rotates and the output interface of the motor assembly abuts against the at least one locking element to move the at least one locking element along an inner circumferential surface of the housing portion, wherein the at least one locking element, the output element, and the output interface commonly rotate about the output rotational axis; and
upon applying the manual torque to the first end of the handle body with a single hand of a user while the output element is coupled to the pedicle screw and the output element is free from the motorized torque, then the manual torque moves the handle body relative to the output element until the at least one locking element abuts against both the inner circumferential surface of the housing portion and a non-concentric external surface of the output element to create a mechanical interference which automatically locks the output element relative to the handle body and transmits the manual torque from the handle body to the output element as the system torque.
10. The method of claim 9 , further comprising transitioning from the manual torque to the motorized torque based on an amount of resistance torque received by the user via the handle body when the manual torque is applied.
11. The method of claim 9 , further comprising monitoring a strength of an attachment of the pedicle screw to the vertebra by transitioning from the motorized torque to the manual torque and evaluating the strength based on an amount of resistance torque received by the user via the handle body during the application of the manual torque.
12. The method of claim 9 , wherein the generating the motorized torque includes producing the motorized torque in a range from two (2) Newton-meters to ten (10) Newton-meters.
13. The method of claim 9 , wherein the generating the motorized torque includes rotating the output element about the output rotational axis at a speed in a range from fifty (50) RPM to two hundred (200) RPM.
14. The method of claim 9 , further comprising selecting a direction of the motorized torque, with at least one switch of the torque driver, wherein the at least one switch comprises a plurality of non-zero speed positions corresponding to the direction of the motorized torque including a clockwise direction and a counterclockwise direction.
15. The method of claim 9 , wherein the receiving the motorized torque with the output element of the anti-backdrive unit from the motor assembly includes the output element receiving the motorized torque from the output interface through the at least one locking element.