Bone Anchor Driver and Methods

Patent metadata

Field	Value
Publication number	US-2016166304-A1
Application number	US-201414570559-A
Country	US
Kind code	A1
Filing date	Dec 15, 2014
Priority date	Dec 15, 2014
Publication date	Jun 16, 2016
Grant date	—

Abstract

Methods and devices are provided for using a bone anchor driver for driving inner and outer set closure mechanisms or set screws into a bone anchor assembly. In one embodiment, a bone anchor driver is provided that includes an outer shaft configured to engage an outer set screw coupled to a bone anchor assembly, an inner shaft disposed within the outer shaft and configured to engage an inner set screw coupled to the bone anchor assembly, and a torque limiting mechanism configured to automatically switch between a first position in which it is disengaged from the inner shaft and is engaged with the outer shaft, and a second position in which it is disengaged from the outer shaft and is engaged with the inner shaft.

First claim

What is claimed is:

1 . A bone anchor driver for driving inner and outer closure mechanisms onto a bone anchor assembly, the bone anchor driver comprising:
an outer shaft configured to engage an outer closure mechanism coupled to a bone anchor assembly; an inner shaft disposed within the outer shaft and configured to engage an inner closure mechanism coupled to a bone anchor assembly; a torque limiting mechanism configured to automatically switch between a first position in which the torque limiting mechanism is disengaged from the inner shaft and is engaged with the outer shaft, and a second position in which the torque limiting mechanism is disengaged from the outer shaft and is engaged with the inner shaft; and an actuator configured to apply a rotational force to the torque limiting mechanism to selectively drive the inner and outer shafts.

2 . The bone anchor driver of claim 1 , wherein the torque limiting mechanism is configured to switch between the first and second positions when a torque applied to the torque limiting mechanism exceeds a threshold torque.

3 . The bone anchor driver of claim 1 , wherein the torque limiting mechanism is disposed between the inner and outer shafts.

4 . The bone anchor driver of claim 1 , wherein the inner and outer shafts define a longitudinal axis, and wherein the torque limiting mechanism translates axially along the longitudinal axis to move between the first and second positions.

5 . The bone anchor driver of claim 1 , wherein at least one of the inner and outer shafts includes a ramp that causes the torque limiting mechanism to translate axially when the torque limiting mechanism moves between the first and second positions.

6 . The bone anchor driver of claim 1 , wherein the torque limiting mechanism comprises a first engaging member configured to engage with a first complementary engaging member of the outer shaft and a second engaging member configured to engage with a second complementary engaging member of the inner shaft.

7 . The bone anchor driver of claim 6 , wherein the first engaging member is positioned in a first plane and the second engaging member is positioned in a second plane that is spaced a distance apart from the first plane.

8 . The bone anchor driver of claim 6 , wherein the first engaging member and the first complementary engaging member are positioned in the same plane when the torque limiting mechanism is in the first position, and wherein the first engaging member and the first complementary engaging member are positioned in different planes when the torque limiting mechanism is in the second position.

9 . The bone anchor driver of claim 6 , wherein the first engaging member is disposed within a first bore extending through the torque limiting mechanism, and the second engaging member is disposed within a second bore extending through the torque limiting mechanism.

10 . The bone anchor driver of claim 9 , wherein an axis of the first bore extends transverse to an axis of the second bore.

11 . The bone anchor driver of claim 6 , wherein the torque limiting mechanism is in the first position when a torque applied thereto is less than or equal to a threshold torque and the first engaging member is biased into engagement with the first complementary engaging member so that the torque limiting mechanism is disengaged from the inner shaft and is engaged with the outer shaft to drive the outer shaft.

12 . The bone anchor driver of claim 11 , wherein, when the torque exceeds the threshold torque, the first engaging member is configured to disengage from the first complementary engaging member and to switch from the first position to the second position in which the second engaging member is biased into engagement with the second complementary engaging member in the inner shaft so that the torque limiting mechanism is disengaged from the outer shaft and is engaged with the inner shaft to drive the inner shaft.

13 . A bone anchor and driver assembly, comprising:
a bone anchor having
a bone engaging member configured to be implanted in bone,
a receiver member polyaxially coupled to the bone engaging member and configured to receive a spinal fixation element therein,
an outer closure mechanism configured to mate to the receiver member for locking a polyaxial position of the receiver member with respect to the bone engaging member, and
an inner closure mechanism configured to be received within the outer closure mechanism and to lock a spinal fixation element within the receiver member; and
a bone anchor driver having
an outer shaft configured to engage and drive the outer closure mechanism into the receiver member,
an inner shaft configured to engage and drive the inner closure mechanism into the receiver member, and
an actuator movable between a first position in which the actuator applies a driving force to the outer shaft and a second position in which the actuator applies a driving force to the inner shaft, the actuator being configured to automatically move from the first position to the second position in response to a torque applied thereto.

14 . The assembly of claim 13 , wherein the actuator moves from the first position to the second position when a torque applied to the actuator exceeds a threshold torque of a torque limiting mechanism coupled between the actuator and the inner and outer shafts.

15 . The assembly of claim 14 , wherein the threshold torque causes the actuator to move from the first position to the second position when the outer closure mechanism is fully engaged with the receiver member to lock the polyaxial position of the receiver member with respect to the bone engaging member.

16 . A method for operating a bone anchor driver, comprising:
actuating a driver to rotate a first shaft to drive a first closure mechanism onto a bone anchor, wherein, when a torque applied to the driver exceeds a threshold torque, the driver automatically moves from a first position decoupled from the first shaft and into a second position coupled with a second shaft to drive a second closure mechanism into the bone anchor.

17 . The method of claim 16 , wherein driving the first closure mechanism into the bone anchor locks a receiver member of the bone anchor in a fixed angular orientation with respect to a bone engaging member of the bone anchor, and driving the second closure mechanism into the bone anchor locks a spinal fixation element in a fixed position within the receiver member of the bone anchor.

18 . The method of claim 16 , wherein a torque limiter causes the driver to move from the first position to the second position when a torque applied to the driver exceeds the threshold torque.

19 . The method of claim 18 , wherein the torque limiter translates axially along a longitudinal axis of the first and second shafts when the driver moves between the first position and the second position.

20 . The method of claim 16 , wherein actuating the driver comprises activating an external power source to cause the driver to rotate.

Assignees

• Medos Int Sarl

Inventors

• Stad Shawn
• Schmuckli Nils

Classifications

• A61B17/84

  Fasteners therefor {or fasteners being internal fixation devices} · CPC title

• A61B17/8886 Primary

  holding the screw head · CPC title

• A61B17/7091 Primary

  for applying, tightening or removing longitudinal element-to-bone anchor locking elements, e.g. caps, set screws, nuts or wedges · CPC title

• A61B2090/031

  torque limiting · CPC title

• A61B17/8894

  holding the implant into or through which the screw is to be inserted (A61B17/7082, A61B17/7091 take precedence) · CPC title