Bone anchor insertion instruments and methods

1. An instrument for driving a bone anchor assembly into bone, comprising:

an anchor drive assembly including a first handle and an elongate shaft having a distal tip configured to couple to a bone anchor assembly;

a stylet assembly including a second handle and a stylet extending through the elongate shaft, the second handle having an outer sleeve and an inner sleeve; and

a first locking mechanism that locks the outer sleeve to the inner sleeve in a first position, wherein movement of the stylet to a proximal-most position relative to the elongate shaft disengages the first locking mechanism to decouple the outer sleeve from the inner sleeve such that the inner sleeve can rotate independently of the outer sleeve;

wherein the instrument moves from a disengaged position into an engaged position in response to axial movement of the outer sleeve relative to the inner sleeve; and

wherein rotation of the first handle is effective to drive the bone anchor assembly into bone only when the instrument is in the engaged position, and rotation of the second handle is effective to cause axial translation of the stylet relative to the elongate shaft.

2. The instrument of claim 1 , wherein the first handle is configured to be decoupled from the elongate shaft when the instrument is in the disengaged position such that the first handle is freely rotatable relative to the elongate shaft, and wherein the first handle is configured to be coupled to the elongate shaft when the instrument is in the engaged position such that rotation of the first handle rotates the elongate shaft.

3. The instrument of claim 1 , wherein the stylet is configured to move proximally in response to the bone anchor assembly being driven into bone when the first handle is rotated and the instrument is in the engaged position.

4. The instrument of claim 1 , wherein the stylet is configured to axially translate relative to the elongate shaft in response to rotation of the second handle while the first handle is held stationary and the instrument is in the engaged position.

5. The instrument of claim 1 , further comprising a clutch mechanism having a first position and a second position, wherein the clutch mechanism in the second position is configured to couple the first handle to the elongate shaft such that rotation of the first handle rotates the elongate shaft.

6. The instrument of claim 1 , further comprising a second locking mechanism that locks the outer sleeve to the inner sleeve in a second position when the first locking mechanism is disengaged, wherein distal movement of the stylet from the proximal-most position disengages the second locking mechanism and reengages the first locking mechanism such that the outer sleeve is recoupled to the inner sleeve.

7. The instrument of claim 1 , wherein the stylet assembly includes a ratchet mechanism that is configured to lock the outer sleeve to the inner sleeve such that the outer and inner sleeves rotate simultaneously in one direction to distally move the stylet relative to the elongate shaft.

8. The instrument of claim 1 , wherein the instrument is biased to the disengaged position.

9. The instrument of claim 1 , wherein the stylet assembly includes a carrier coupled to the stylet and disposed within the anchor drive assembly and threadably coupled to the second handle.

10. A bone anchor inserter instrument, comprising:

an elongate shaft having a distal tip configured to couple to a bone anchor assembly;

a stylet extending through the elongate shaft; and

a handle assembly coupled to a proximal end of the elongate shaft, the handle assembly including a first handle, a second handle, and a carrier movably disposed within the handle assembly and coupled to the stylet;

wherein the handle assembly has a first configuration in which the first handle rotates freely relative to the elongate shaft, and a second configuration in which rotation of the first handle relative to the second handle causes corresponding rotation of the elongate shaft, and rotation of the second handle relative to the first handle causes axial translation of the carrier and the stylet coupled thereto; and

wherein the second handle includes an outer sleeve and an inner sleeve, and wherein the inner sleeve rotates freely relative to the outer sleeve when the handle assembly is in the second configuration and the carrier is in a most-proximal position.

11. The bone anchor inserter instrument of claim 10 , wherein the stylet is configured to move proximally in response to rotation of the first handle when the handle assembly is in the second configuration.

12. The bone anchor inserter instrument of claim 10 , wherein the outer sleeve is configured to axially move relative to the inner sleeve to move the handle assembly from the first configuration to the second configuration.

13. The bone anchor inserter instrument of claim 10 , further comprising a clutch mechanism having a first position and a second position, wherein the clutch mechanism in the second position is configured to couple the first handle to the elongate shaft such that rotation of the first handle rotates the elongate shaft.

14. The bone anchor inserter instrument of claim 10 , wherein rotation of the first handle is effective to drive the bone anchor assembly into bone only when the handle assembly is in the second configuration.

15. The bone anchor inserter instrument of claim 10 , wherein, when the handle assembly is in the second configuration, the carrier is non-rotatably translatable through the handle assembly in response to rotation of the second handle while the first handle is held stationary.

16. The bone anchor inserter instrument of claim 15 , wherein, when the handle assembly is in the second configuration, the carrier is rotatably translatable through the handle assembly in response to rotation of the first handle while the second handle is held stationary.