Patent Description:
Bone anchors can be used in orthopedic surgery to fix bone during healing, fusion, or other processes. In spinal surgery, for example, bone anchors can be used to secure a spinal fixation element to one or more vertebrae to rigidly or dynamically stabilize the spine.

In a conventional procedure for coupling a bone anchor to bone, access to the bone is obtained, for example by forming a skin incision and resecting soft tissue disposed over the bone or by using a minimally-invasive technique. An insertion needle with a stylet disposed therein, sometimes referred to as a Jamshidi needle, is then driven into the bone to establish the trajectory for a bone opening. Next, the stylet is removed and a guidewire is inserted through the needle. The needle is then withdrawn over the guidewire, leaving the guidewire in place. A cannulated tap is then advanced over the guidewire and driven into the bone to enlarge the bone opening into a pilot hole for the bone anchor. Thereafter, the tap is withdrawn over the guidewire, again leaving the guidewire in place within the bone opening. A cannulated bone anchor is then advanced over the guidewire and driven into the bone opening. Finally, the guidewire is removed and one or more fixation elements are coupled to the bone anchor.

The conventional procedure detailed above suffers from a number of disadvantages.

For example, the process involves several steps which can be time-consuming and cumbersome, particularly where a number of bone anchors are being installed. In addition, many of these steps (e.g., advancing the needle, advancing the guidewire, advancing the tap, and advancing the bone anchor) are done with fluoroscopic guidance to confirm the correct trajectory and insertion depth. With each additional step, the radiation exposure to the patient and surgical team increases, potentially causing dangerous complications or negative long-term health effects. The steps of removing the needle and removing the tap can also cause the guidewire to dislodge from the bone opening, requiring the process to be started anew. Further still, advancing the anchor or advancing the tap can inadvertently cause the guidewire to advance within the bone opening, potentially damaging delicate anatomical structures disposed in proximity to the bone. Advancing the anchor or advancing the tap can also cause the guidewire to become kinked, making removal of the guidewire very difficult. Accordingly, a need exists for improved bone anchors and associated instrumentatior.

US Patent Publication No. <CIT> discloses a tool for installing a bone screw in a bone. The tool has a guide wire having an inner end adapted to be seated at the bone at a site where the screw, which is tubular and can fit around and slide along the wire, is to be installed. A tubular tool body is fittable over and around the wire. A stabilizer is axially and rotationally fixable to the wire offset from the tool body so that the screw can be screwed axially into the bone at the site while the wire is prevented from moving axially by the stabilizer. A locking screw is screwed into the stabilizer to fix an axial position of the guidewire relative to the bone screw. A surgeon is required to grip the stabilizer whilst rotating the tool body in order to rotate the screw and drive it into bone. During this operation, the tool body is unscrewed from a threaded inner end of the stabilizer.

Various surgical instruments are disclosed herein for implanting a bone anchor into bone. In one embodiment, a surgical instrument for driving a bone anchor assembly into bone is provided and includes an elongate shaft having a distal tip configured to couple to a bone anchor assembly, a handle assembly coupled to the elongate shaft, the handle assembly including a first handle and a second handle rotatably coupled to one another, a stylet extending through an inner lumen of the first handle and the elongate shaft, and a carrier moveably coupled to the handle assembly, wherein rotation of the first handle while the second handle is held stationary causes the carrier to non-rotatably translate axially relative to the elongate shaft and to cause the stylet to axially translate relative to the elongate shaft, and wherein rotation of the second handle causes the carrier to rotatably translate and causes rotation of the elongate shaft to advance the bone anchor along the stylet.

In some embodiments, the first handle can be positioned distal to the second handle. The surgical instrument can further include a stylet holder coupled to the carrier and releasably engaged to the stylet. The stylet holder can be releasably engaged with the carrier and can allow axial translation of the stylet when the stylet holder is in a first position relative to the carrier, and can prevent axial translation of the stylet when the stylet holder is in a second position relative to the carrier. The surgical instrument can further include a bone anchor assembly matable to the distal tip of the elongate shaft and having threads formed thereon that define an insertion rate of the bone anchor assembly into bone. The carrier can be configured to translate within the handle assembly at a rate that is equal to the insertion rate of the bone anchor assembly.

In some embodiments, a surgical instrument for driving a bone anchor assembly into bone can include an elongate shaft having proximal and distal ends, a mating feature formed on the distal end that is configured to mate to a bone anchor assembly, and an inner lumen extending through the elongate shaft. A stylet can extend through the inner lumen of the elongate shaft. The surgical instrument can also include a proximal handle configured to rotate the elongate shaft to drive a bone anchor assembly coupled to the mating feature on the distal end of the elongate body into bone. In addition, the surgical instrument can include a distal handle rotatable relative to the proximal handle. The surgical instrument can further include a carrier threadably disposed within the handle assembly and configured to move axially relative to the elongate shaft in response to rotation of one of the proximal and distal handles relative to the other one of the proximal and distal handles in order to cause the stylet to translate axially relative to the elongate shaft.

In one embodiment, rotation of the proximal handle while the distal handle is held stationary can cause rotation of the elongate shaft, and rotation and axial translation of the carrier within the handle assembly. Conversely, rotation of the distal handle while the proximal handle is held stationary can cause the carrier to translate axially within the handle assembly without rotating the elongate shaft. In certain embodiments, the proximal handle can be mated to the proximal end of the elongate shaft, and the distal handle can be rotatably disposed about a proximal portion of the elongate shaft at a location distal to the proximal handle. The carrier can be threadably coupled to threads formed within the distal handle and the stylet can be integrally formed on and can extend distally from the carrier. Alternatively or in addition, the stylet can be removably mated to the carrier by a mating element.

In certain embodiments, the surgical instrument can include a stylet holder disposed within the handle assembly that can allow the stylet to extend therethrough. The stylet holder can have a first position, in which the stylet is freely slidable relative to the stylet holder, and a second position in which the stylet holder rigidly engages the stylet to prevent movement of the stylet relative to the stylet holder. The stylet holder can be configured to be advanced into the carrier to cause the stylet holder to move from the first position to the second position. The stylet holder can include a clamping feature that is compressed by the carrier in the second position to cause the clamping feature to rigidly engage the stylet.

The elongate shaft of the surgical instrument can include a proximal portion with one or more slots, with the proximal portion extending through the distal handle and having a proximal end mated to the proximal handle. The carrier can be slidably disposed within the proximal portion, and the carrier can be non-rotatable relative to the proximal portion such that the carrier and the elongate shaft rotate together. The carrier can include one or more threaded features that extend through the one or more slots. The one or more slots can allow translation while preventing rotation of the carrier within the elongate shaft.

The surgical instrument can include other components, such as a protective sleeve removably disposed around the elongate shaft, and/or a positioning handle coupled to a proximal end of the stylet that is configured to adjust a length of stylet that extends from a bone anchor assembly coupled to the distal end of the elongate shaft. The positioning handle can include a tool feature for engaging a stylet holder disposed within the handle assembly and having the stylet extending therethrough. The tool feature can be configured to advance the stylet holder into the carrier to cause the stylet holder to move from a first position to a second position, wherein the second position locks the stylet to the stylet holder. The positioning handle can include an outer housing encompassing at least a part of a positioning feature that secures the proximal end of the stylet to the positioning handle. The positioning feature can include a push button that releasably engages an engagement position along the outer housing. The positioning feature can be configured to move with the stylet relative to the outer housing when the push button is disengaged from the engagement position.

In some embodiments, a surgical instrument for driving a bone anchor assembly into bone can include an elongate shaft having proximal and distal ends, a mating feature formed on the distal end and configured to mate to a bone anchor assembly, an inner lumen extending through the elongate shaft, and a handle assembly coupled to the elongate shaft. The handle assembly can include a distal handle coupled to the proximal end of the elongate shaft and it can be configured to rotate the elongate shaft to drive a bone anchor assembly coupled to the mating feature on the distal end of the elongate body into bone. The handle assembly can further include a proximal handle threadably coupled to the distal handle and coupled to a proximal end of a stylet that extends through the inner lumen of the elongate shaft, with the proximal handle being rotatable relative to the distal handle in order to cause the stylet to axially translate relative to the elongate shaft.

In some background information, not claimed, a method of delivering a bone anchor assembly is provided. The method can include coupling an engagement portion on a shaft of a driver to a corresponding engagement portion on a bone anchor assembly. The method can also include rotating a second handle of the driver while holding a first handle of the driver stationary to cause a carrier disposed within the driver to translate a stylet relative to the bone anchor assembly. The method can further include rotating a first handle of the driver while holding a second handle of the driver stationary to cause the shaft to rotate and advance the bone anchor assembly along the stylet. When the first handle is rotated while the second handle is held stationary, the carrier can be caused to translate axially within the driver to move the stylet axially relative to the elongate shaft.

Devices for inserting bone anchor assemblies into bone are provided herein. Use of these anchors or instruments can eliminate one or more of the steps in a conventional bone anchor installation procedure, improving surgical efficiency and safety. In general, surgical insertion devices are provided that include a proximal handle and a distal handle, with the proximal handle configured to control the movement of an elongate shaft of the device and the distal handle configured to control the movement of a guidewire or stylet extending through the device. Rotation of the distal handle relative to the proximal handle can cause the stylet to axially translate in a proximal or distal direction relative to the elongate shaft. In addition, rotation of the proximal handle relative to the distal handle can cause the elongate shaft to rotate, which can assist with driving a bone anchor assembly coupled to a distal end of the elongate shaft into bone. We note that the terms guidewire and stylet are used interchangeably herein, and any configuration of a guidewire or stylet can be used with the various instruments disclosed herein.

<FIG> illustrate one embodiment a prior art bone anchor assembly <NUM> that includes a bone anchor <NUM>, a receiver member <NUM> for receiving a spinal fixation element, such as a spinal rod <NUM>, to be coupled to the bone anchor <NUM>, and a closure mechanism <NUM> to capture a spinal fixation element within the receiver member <NUM> and fix the spinal fixation element with respect to the receiver member <NUM>. The bone anchor <NUM> includes a proximal head <NUM> and a distal shaft <NUM> configured to engage bone. The receiver member <NUM> has a proximal end <NUM> having a pair of spaced apart arms 28A, 28B defining a recess <NUM> therebetween and a distal end <NUM> having a distal end surface <NUM> defining an opening through which at least a portion of the bone anchor <NUM> extends. The closure mechanism <NUM> can be positionable between and can engage the arms 28A, 28B to capture a spinal fixation element, e.g., a spinal rod <NUM>, within the receiver member <NUM> and fix the spinal fixation element with respect to the receiver member <NUM>.

The proximal head <NUM> of the bone anchor <NUM> is generally in the shape of a truncated sphere having a planar proximal surface <NUM> and an approximately spherically-shaped distal surface <NUM>. The illustrated bone anchor assembly is a polyaxial bone screw designed for posterior implantation in the pedicle or lateral mass of a vertebra. The proximal head <NUM> of the bone anchor <NUM> engages the distal end <NUM> of the receiver member <NUM> in a ball and socket like arrangement in which the proximal head <NUM> and the distal shaft <NUM> can pivot relative to the receiver member <NUM>. The distal surface <NUM> of the proximal head <NUM> of the bone anchor <NUM> and a mating surface within the distal end <NUM> of the receiver member <NUM> can have any shape that facilitates this arrangement, including, for example, spherical (as illustrated), toroidal, conical, frustoconical, and any combinations of these shapes.

The distal shaft <NUM> of the bone anchor <NUM> can be configured to engage bone and, in the illustrated embodiment, includes an external bone engaging thread <NUM>. The thread form for the distal shaft <NUM>, including the number of threads, the pitch, the major and minor diameters, and the thread shape, can be selected to facilitate connection with bone. Exemplary thread forms are disclosed in <CIT>, and in <CIT>. While a threaded distal shaft <NUM> is shown, the distal shaft can have other structures for engaging bone, including a hook. The distal shaft <NUM> of the bone anchor <NUM> can be cannulated, having a central passage or inner lumen <NUM> extending the length of the bone anchor to facilitate delivery of the bone anchor over a guidewire or stylet in, for example, minimally-invasive procedures. Other components of the bone anchor assembly <NUM>, including, for example, the closure mechanism <NUM>, the receiver member <NUM>, and the compression member <NUM> (discussed below), can be cannulated or otherwise have an opening to permit delivery over a guidewire or stylet. The distal shaft <NUM> can also include one or more sidewall openings or fenestrations that communicate with the inner lumen <NUM> to permit bone in-growth or to permit the dispensing of bone cement or other materials through the bone anchor <NUM>. The sidewall openings can extend radially from the inner lumen <NUM> through the sidewall of the distal shaft <NUM>. Exemplary systems for delivering bone cement to the bone anchor assembly <NUM> and alternative bone anchor configurations for facilitating cement delivery are described in <CIT>. The distal shaft <NUM> of the bone anchor <NUM> can also be coated with materials to permit bone growth, such as, for example, hydroxyapatite, and the bone anchor assembly <NUM> can be coated partially or entirely with anti-infective materials, such as, for example, tryclosan.

The receiver member <NUM>, which couples to the bone anchor <NUM>, includes a pair of spaced apart arms 28A, 28B at the proximal end <NUM> defining a U-shaped recess <NUM> therebetween for receiving a spinal fixation element, e.g., a spinal rod <NUM>. Each of the arms 28A, 28B can extend from the distal end <NUM> of the receiver member <NUM> to a free end. The outer surfaces of each of the arms 28A, 28B can include a feature, such as a recess, dimple, notch, projection, or the like, to facilitate connection of the receiver member <NUM> to instruments. For example, the outer surface of each arm 28A, 28B can include an arcuate groove at the respective free end of the arms. Such grooves are described in more detail in <CIT>.

The distal end <NUM> of the receiver member <NUM> includes a distal end surface <NUM> which is generally annular in shape defining a circular opening through which at least a portion of the bone anchor <NUM> extends. For example, the distal shaft <NUM> of the bone anchor <NUM> can extend through the opening.

The bone anchor <NUM> can be selectively fixed relative to the receiver member <NUM>. Prior to fixation, the bone anchor <NUM> is movable relative to the receiver member <NUM> within a cone of angulation generally defined by the geometry of the distal end <NUM> of the receiver member and the proximal head <NUM> of the bone anchor <NUM>. The bone anchor <NUM> can be a favored angle screw, for example as disclosed in <CIT>, and in <CIT>. Alternatively, the bone anchor assembly can be a conventional (non-biased) polyaxial screw in which the bone anchor pivots in the same amount in every direction.

The spinal fixation element, e.g., the spinal rod <NUM>, can either directly contact the proximal head <NUM> of the bone anchor <NUM> or can contact an intermediate element, e.g., a compression member <NUM>. The compression member <NUM> can be positioned within the receiver member <NUM> and interposed between the spinal rod <NUM> and the proximal head <NUM> of the bone anchor <NUM> to compress the distal outer surface <NUM> of the proximal head <NUM> into direct, fixed engagement with the distal inner surface of the receiver member <NUM>. The compression member <NUM> can include a pair of spaced apart arms 62A and 62B defining a U-shaped seat <NUM> for receiving the spinal rod <NUM> and a distal surface <NUM> for engaging the proximal head <NUM> of the bone anchor <NUM>.

The proximal end <NUM> of the receiver member <NUM> can be configured to receive a closure mechanism <NUM> positionable between and engaging the arms 28A, 28B of the receiver member <NUM>. The closure mechanism <NUM> can be configured to capture a spinal fixation element, e.g., a spinal rod <NUM>, within the receiver member <NUM>, to fix the spinal rod <NUM> relative to the receiver member <NUM>, and to fix the bone anchor <NUM> relative to the receiver member <NUM>. The closure mechanism <NUM> can be a single set screw having an outer thread for engaging an inner thread <NUM> provided on the arms 28A, 28B of the receiver member <NUM>. In other embodiments, however, the closure mechanism <NUM> can include an outer set screw operable to act on the compression member <NUM> and an inner set screw operable to act on the rod <NUM>.

The bone anchor assembly <NUM> can be used with a spinal fixation element such as rigid spinal rod <NUM>. Alternatively, the spinal fixation element can be a dynamic stabilization member, such as a flexible or selectively flexible member, that allows controlled mobility between the instrumented vertebrae.

In use, the bone anchor assembly <NUM> can be assembled such that the distal shaft <NUM> extends through the opening in the distal end <NUM> of the receiver member <NUM> and the proximal head <NUM> of the bone anchor <NUM> is received in the distal end <NUM> of the receiver member <NUM>. The compression member <NUM> can be positioned within the receiver member <NUM> such that the arms 62A, 62B of the compression member are aligned with the arms 28A, 28B of the receiver member <NUM> and the lower surface of the compression member <NUM> is in contact with the proximal head <NUM> of the bone anchor <NUM>. A driver tool can extend through the compression member <NUM> and can be fitted with the bone anchor <NUM> to drive the bone anchor <NUM> into bone. A spinal fixation element, e.g., the spinal rod <NUM>, can be located in the recess <NUM> of the receiver member <NUM>. The closure mechanism <NUM> can be engaged with the inner thread <NUM> provided on the arms 28A, 28B of the receiver member <NUM>. A torsional force can be applied to the closure mechanism <NUM> to move it within the recess <NUM> so as to force the spinal rod <NUM> into engagement with the compression member <NUM> and to in turn force the compression member <NUM> onto the proximal head <NUM> of the bone anchor <NUM>, thereby fixing the spinal rod <NUM> relative to the receiver member <NUM> and locking the angular position of the bone anchor <NUM> relative to the receiver member <NUM>.

The surgical instruments disclosed herein can be configured to operate in conjunction with bone anchor assemblies of the type described above or other types known in the art. As indicated above, it will be appreciated that the bone anchor assembly <NUM> can be a monoaxial screw, a polyaxial screw, a uniplanar screw, a bone hook, a favored-angle screw, and/or any of a variety of other bone anchor types known in the art. Further information on favored-angle screws can be found in <CIT>.

In general, various insertion instruments are provided for driving a bone anchor assembly into bone. The insertion instruments generally include a handle assembly and an elongate shaft extending distally therefrom for coupling to a bone anchor assembly. The instruments are configured to receive a stylet therethrough and the handle assembly is configured to control positioning of the stylet. In particular, the handle assembly can be configured to allow for adjustment of an axial position of the stylet relative to a bone anchor assembly coupled to the elongate shaft. The handle assembly can also be configured to move the stylet proximally relative to a bone anchor assembly during insertion of the bone anchor assembly into bone. Such movement of the stylet can occur automatically, in response to rotation of a portion of the handle to drive the bone anchor assembly into bone. Such a configuration is particularly advantageous as it will prevent further insertion of the stylet into bone during advancement of the bone anchor assembly. A person skilled in the art will appreciate that the instruments disclosed herein can have a variety of configurations, and that the various features disclosed in the various embodiments are interchangeable.

<FIG> and <FIG> illustrate an embodiment of a surgical instrument <NUM> for driving a bone anchor assembly into bone. The surgical instrument can include a handle assembly <NUM> having an elongate shaft <NUM> extending distally therefrom, and a stylet <NUM> extending through the handle assembly <NUM> and the elongate shaft <NUM>. The elongate shaft <NUM> can be configured to mate to a bone anchor assembly, and the handle assembly <NUM> can be configured to both drive a bone anchor assembly into bone, and manipulate the stylet both before and during insertion of a bone anchor assembly into bone.

The elongate shaft <NUM> can have a variety of configurations, but generally the shaft <NUM> includes a proximal end <NUM> for coupling to the handle assembly and a distal end <NUM> for mating to a bone anchor assembly. A length of the shaft <NUM> can vary, but the shaft preferably has a length sufficient to allow the handle assembly to be positioned outside of a patient's body while the distal end <NUM> is positioned into a patient's body adjacent to bone. To facilitate mating to a bone anchor assembly, the distal end <NUM> of the elongate shaft <NUM> can include a mating feature <NUM> formed thereon. The mating feature <NUM> can be formed anywhere along the elongate shaft <NUM>, such as the distal end <NUM>, and it can be configured to engage a bone anchor assembly (e.g., bone anchor assemblies of the type described above with respect to <FIG>). The mating feature <NUM> can include a threaded portion <NUM> configured to engage corresponding threads formed in the receiver member of the bone anchor assembly. The mating feature <NUM> can also include a tip <NUM> disposed distally of the threaded portion <NUM> and configured to engage a drive socket or a proximal surface of the bone anchor disposed within the receiver member. The tip <NUM> can have a diameter that is less than the diameter of the threaded portion <NUM>. The mating feature <NUM> can also be configured to engage a bone tap, or a bone tap can be formed integrally with the elongate shaft <NUM>.

One or more bulges <NUM> or areas of increased diameter can be formed along the length of the elongate shaft <NUM> to engage and stabilize extension or protective sleeves that can be coupled to the bone anchor assembly. As shown in <FIG>, the bone anchor assembly can include break-off extensions <NUM>, which can act as a delivery cannula during insertion of the set screw and can be broken off at the end of the procedure.

The elongate shaft <NUM> can include a cannulated proximal portion having a bore extending at least partially therethrough and one or more slots formed therein that define opposed tabs <NUM>. The slot(s) can extend through only a portion of the proximal portion such that the opposed tabs <NUM> are connected at their proximal ends, or the slots extend through the entire length of the proximal portion as shown in the illustrated embodiment. A person skilled in the art will appreciate that the slots can have any length as may be required to allow for translation of the carrier, discussed below. In the illustrated embodiment, the tabs <NUM> can have a generally cylindrical configuration and define a hollow generally cylindrical interior lumen for receiving a carrier. A distal end of each tab <NUM> can be mounted on and can extend from a mounting surface defined by a proximal flange <NUM> formed on the elongate shaft, and a proximal end of each of the opposed tabs <NUM> can mate with a distal end of the proximal handle <NUM> such that rotation of the proximal handle <NUM> is effective to rotate the elongate shaft <NUM>. In particular, the proximal end of each tab <NUM> can be sized to be received within a distal end of the proximal handle <NUM>, as discussed below, and can be fixedly mated thereto, e.g., using an adhesive, welding, threads, or any other mating feature. In an embodiment, threads (not shown) are formed on an outer surface of the proximal end of the opposed tabs <NUM> for mating with corresponding threads formed within the proximal handle <NUM>. Where the tabs are not connected, a support collar <NUM> can optionally be disposed within a proximal portion of the opposed tabs <NUM> to prevent inward radial movement of the opposed tabs and to maintain the threaded connection between the opposed tabs <NUM> and the proximal handle <NUM>, as shown in <FIG>; however, one or more of a variety of features can be used to connect any part of the elongate shaft <NUM>, such as the opposed tabs <NUM>, to the proximal handle <NUM>. In addition, although described herein as opposed tabs <NUM>, the proximal end of the elongate shaft <NUM> can have a variety of configurations including various shapes and sizes. Preferably, the proximal end is in the form of a body having a lumen and at least one slot, with the shape of the body varying as may be determined based on the shape of the handle disposed therearound. Any number of a variety of features and configurations can be included at the proximal end of the elongate shaft <NUM> and are not limited to opposed tabs <NUM>.

As indicated above, the handle assembly <NUM> can be located adjacent the proximal end <NUM> of the elongate shaft <NUM> and can include a proximal handle <NUM> and a distal handle <NUM>. The handle assembly <NUM> can be positioned and sized to allow a user, such as a surgeon, to grasp a part of the handle assembly <NUM> and operate the surgical instrument <NUM>. While the proximal and distal handles <NUM>, <NUM> can each have a variety of configurations, in the illustrated embodiment each handle <NUM>, <NUM> has a generally elongate cylindrical configuration and is cannulated with an inner lumen extending therethrough, as shown in <FIG>. Each handle <NUM>, <NUM> can include gripping features, such as knurling or other surface features, formed thereon to facilitate grasping of the device. The proximal handle <NUM> can be coupled to the proximal end <NUM> of the elongate shaft <NUM> and can be configured to rotate the elongate shaft <NUM>, such as to drive a bone anchor assembly coupled to the mating feature <NUM> into bone. In particular, as described above, threads or other mating features on a proximal end of the opposed tabs <NUM> can mate to threads <NUM> formed within a distal portion of the inner lumen of the proximal handle.

As shown in <FIG>, the inner lumen in the proximal handle <NUM> includes an enlarged diameter region along its distal portion for receiving a proximal-most end or extension <NUM> of the opposed tabs <NUM> at the proximal end of the elongate shaft <NUM>. The distal handle <NUM> can be positioned just distal to the proximal handle <NUM> and can be moveably disposed about a proximal portion of the elongate shaft <NUM>. In particular, as shown in <FIG>, the distal handle <NUM> can be disposed about the opposed tabs <NUM> of the elongate shaft <NUM> and can be configured to freely rotate relative to at least the elongate shaft <NUM>. The proximal flange <NUM> on the elongate shaft <NUM> can assist in preventing translational movement of the distal handle <NUM> relative to the proximal handle <NUM> and elongate shaft <NUM>. In order to facilitate mounting of the distal handle <NUM> about the opposed tabs <NUM>, the inner lumen extending through the distal handle can have a diameter that is slightly larger than an outer diameter of the opposed tabs <NUM>. As further shown in <FIG>, the distal handle <NUM> can include interior threads <NUM> formed therein and extending along at least a portion or an entire length of the inner lumen extending through the distal handle <NUM>. The threads <NUM> can mate with threads on the carrier, as discussed below. In use, each of the proximal and distal handles <NUM>, <NUM> can be rotated relative to one other while the other handle is held stationary. Rotation of the proximal handle <NUM> will rotate the shaft <NUM> to drive a bone anchor assembly into bone, and rotation of the distal handle <NUM> can assist with positioning the stylet <NUM> relative to the elongate shaft <NUM>, such as to allow a length of stylet <NUM> to extend from the distal end <NUM> of the elongate shaft <NUM>, as will be discussed in detail below.

Although described as the proximal handle <NUM> being configured to rotate the elongate shaft <NUM> and the distal handle <NUM> being configured to axially translate the stylet <NUM> relative to the elongate shaft <NUM>, the proximal handle <NUM> can be configured to axially translate the stylet <NUM> relative to the elongate shaft <NUM> and the distal handle <NUM> can be configured to rotate the elongate shaft <NUM>.

Continuing to refer to <FIG> and <FIG>, the surgical instrument <NUM> can further include a carrier <NUM> movably disposed within the handle assembly <NUM>. The carrier <NUM> can be configured to couple to a stylet, as discussed below, and in use the carrier can facilitate positioning of the stylet relative to a bone anchor assembly coupled to the elongate shaft <NUM>.

While the carrier <NUM> can have a variety of configurations, in the illustrated embodiment the carrier <NUM> has a generally cylindrical configuration and is cannulated with an inner lumen extending therethrough. As shown in <FIG>, the carrier <NUM> can be slidably disposed within the opposed tabs <NUM>. The carrier <NUM> can thus have an outer diameter that is less than an inner diameter of the lumen defined by the opposed tabs <NUM> to allow the carrier to be disposed therein. The carrier <NUM> can include one or more threaded features <NUM> formed on an outer surface of the carrier <NUM> that engage the interior threads <NUM> located on an inner surface of the distal handle <NUM>. As shown in <FIG>, the carrier <NUM> includes first and second threaded features formed on opposed sides thereof and not extending fully circumferentially around the carrier, with the opposed threaded features being received within the opposed slots <NUM> in the opposed tabs <NUM>. Thus a portion of the outer surface of the carrier <NUM> can be non-threaded and configured to slide along or adjacent the inner walls of the opposed tabs <NUM>, such as when the carrier <NUM> translates and moves the stylet <NUM> in a proximal or distal direction. The one or more slots <NUM> can allow the one or more threaded features <NUM> formed on opposed sides of the carrier to extend therethrough and to engage the threaded features <NUM> of the distal handle <NUM>. Such a configuration will allow the threaded features <NUM>, and thus the carrier <NUM>, to translate axially along the opposed tabs <NUM>, yet will prevent rotation of the carrier relative to the opposed tabs <NUM>, and thus the elongate shaft <NUM>. As a result, when the proximal handle <NUM> is be held by the user and the distal handle <NUM> is rotated, the threads <NUM> in the distal handle <NUM> will interact with the threaded features <NUM> on the carrier <NUM> to cause the carrier <NUM> to translate axially without rotating along the opposed tabs <NUM> and relative to the elongate shaft <NUM>. In addition, if the distal handle <NUM> is held and the proximal handle <NUM> is rotated, the opposed tabs <NUM>, which rotate in coordination with the proximal handle <NUM>, will force the carrier <NUM> to rotate. The interaction between the threads in the distal handle <NUM> and the threaded features <NUM> on the carrier will thus cause the carrier <NUM> to translate axially along the opposed tabs <NUM> and thus relative to the elongate shaft.

In some implementations, the thread pitch of the carrier <NUM> and distal handle <NUM> can be the same as the thread pitch of the bone screw. The direction of the threads in the carrier <NUM> and distal handle <NUM>, however, are preferably reversed as compared to a direction of the threads on a bone-screw. Such a configuration can allow the bone screw to advance into the bone at approximately the same rate as the stylet is retracted, as discussed below. Reversal of the thread pitch also results in a configuration in which the proximal handle <NUM> can be rotated in a first direction, e.g., clockwise, to drive a bone screw into bone, while rotation of the distal handle in a second opposite direction, e.g. counter-clockwise, is effective to advance the carrier <NUM> and stylet distally through distal handle <NUM>. In other embodiments, the thread pitch of the carrier <NUM> and distal handle <NUM> can differ from the thread pitch of the bone screw so as to result in movement of the stylet at a rate that is greater or less than a rate of insertion of the bone screw. In addition, the slots <NUM> can extend approximately <NUM> millimeters to approximately <NUM> millimeters. Thus, this can allow the carrier <NUM> and stylet <NUM> to translate a distance of approximately <NUM> millimeters to approximately <NUM> millimeters.

However, the slots <NUM> can extend a variety of lengths and are not limited to the examples described herein.

Movement of the carrier <NUM> within the distal handle <NUM>, as described above, can cause corresponding movement of a stylet coupled thereto. <FIG> and <FIG> illustrate a stylet <NUM> having a generally elongate configuration with a pointed distal tip to facilitate insertion into bone. As noted above, the stylet <NUM> or guidewire can have a variety of configurations. As shown in <FIG> and <FIG>, the carrier <NUM> can include an inner lumen <NUM> that extends along the length of the carrier <NUM> and is configured to allow the stylet <NUM> to extend through. The stylet <NUM> can be integrally formed on and can extend distally from the carrier <NUM>, or it can be removably mated to the carrier, such as with the assistance of a mating element (e.g., set screw). For example, the mating element can allow the length of stylet <NUM> extending in a direction from the carrier <NUM> to be altered. In the illustrated embodiment, the carrier <NUM> can include a threaded thru-hole <NUM> extending radially through a sidewall thereof that can accept a set screw <NUM> that can be advanced into the carrier <NUM> in order to engage and secure the stylet <NUM> within the inner lumen <NUM> of the carrier. Additionally, the handle assembly <NUM>, such as the distal handle <NUM>, can include a thru-hole <NUM> that can allow a tool to be inserted through the thru-hole and to access the set screw for adjusting the axial position of the stylet <NUM> relative to the carrier <NUM>. For example, adjusting the position of the stylet <NUM> relative to the carrier <NUM> can affect the length of stylet <NUM> that can extend from the distal end <NUM> of a bone anchor assembly coupled to the elongate shaft <NUM>. For example, distal translation of the stylet <NUM> can allow the length of stylet extending from the distal end <NUM> of the elongate shaft <NUM> to increase and proximal translation of the stylet <NUM> can allow the length of stylet <NUM> extending from the distal end <NUM> of the elongate shaft <NUM> to decrease.

<FIG> illustrates an example of a surgical instrument <NUM> for driving a bone anchor assembly into bone that is identical to that of <FIG> and <FIG>, except that the stylet <NUM> is integrally formed with the carrier <NUM>. As shown in <FIG>, the stylet <NUM> is unitary or monolithic with the carrier <NUM> and extends distally from a distal side of the carrier <NUM>. In this embodiment, the stylet <NUM> can translate relative to the elongate shaft <NUM>, but the stylet <NUM> cannot translate relative to the carrier <NUM>. As such, the maximum length of stylet <NUM> that can extend from the distal end <NUM> of the elongate shaft <NUM> when the carrier <NUM> is in a most distal position relative to the distal handle <NUM> cannot be adjusted (i.e., lengthened or shortened).

<FIG> illustrates another example of a surgical instrument <NUM> for driving a bone anchor assembly into bone. The instrument <NUM> of <FIG> is identical to that of <FIG> and <FIG>, except that the stylet <NUM> is threadably engaged with the carrier <NUM>. For example, the stylet <NUM> can include threads <NUM> along a proximal portion of the stylet <NUM>. In addition, the carrier <NUM> can include a thru-hole <NUM>, with at least a part of the thru-hole including threads that can threadably engage the threads <NUM> along the stylet <NUM>. Furthermore, the thru-hole <NUM> can either have more than one diameter (e.g., a recessed bore) or not be threaded all the way through, such as in order to prevent the stylet <NUM> from advancing too far through the carrier <NUM> or becoming disengaged. As such, the proximal end of the stylet <NUM> can be passed through the thru-hole <NUM> of the carrier <NUM> and the threaded portion <NUM> of the stylet <NUM> can be threadably engaged with the carrier <NUM> until the stylet <NUM> is secured to the carrier <NUM>. Once the stylet <NUM> is secured to the carrier <NUM>, such as during manufacturing of the surgical instrument, the stylet <NUM> can translate relative to the elongate shaft <NUM>, but the stylet <NUM> cannot translate relative to the carrier <NUM>. As such, the maximum length of stylet <NUM> that can extend from the distal end <NUM> of the elongate shaft <NUM> when the carrier <NUM> is in a most distal position relative to the distal handle <NUM> cannot be adjusted (i.e., lengthened or shortened).

<FIG> illustrate yet another embodiment of a surgical instrument <NUM> for driving a bone anchor into bone. The instrument <NUM> of <FIG> is identical to that of <FIG> and <FIG>, except that the surgical instrument <NUM> includes a stylet holder <NUM> that can assist with coupling a stylet <NUM> to a carrier <NUM>. The stylet holder <NUM> can include a thru-hole <NUM> along the length of the stylet holder <NUM> and the stylet <NUM> can extend through the thru-hole <NUM> in order to slidably engage with or secure to a part of the thru-hole <NUM>. The stylet holder <NUM> can be loaded and/or removed from either the distal end or proximal end of the stylet holder. The engagement of the stylet <NUM> with the stylet holder <NUM> can depend on a positioning of the stylet holder <NUM> relative to the carrier <NUM>, as will be described in greater detail below.

The stylet holder <NUM> can have a generally cylindrical configuration, although an outer diameter can vary along external portions thereof. As shown, the stylet holder <NUM> includes a proximal non-threaded cylindrical portion that is sized to be received within the support collar <NUM>, and a distal portion having a threaded member <NUM> and a clamping feature <NUM>. The distal portion is configured to be received within the carrier <NUM> such that the threaded member <NUM> formed along an outer surface of the stylet holder <NUM> is threadably engaged with a threaded bore <NUM> of the carrier <NUM>. The clamping feature <NUM> is in the form of a slotted tapered nose defining opposed arms that are compressible radially inward to engage the stylet. The arms taper radially inward toward the distal-most end.

In use, the stylet holder <NUM> can be movable between a first position (unlocked) and a second position (locked) relative to the carrier <NUM>. In the first position, the stylet holder <NUM> can be, at most, partially threadably engaged with the carrier <NUM>. In addition, when the stylet holder <NUM> is in the first position the clamping feature <NUM> of the stylet holder <NUM> is not engaged with the carrier. When the clamping feature <NUM> of the stylet holder <NUM> is not engaged with the carrier <NUM>, the clamping feature <NUM> does not compress around the stylet <NUM> and allows the stylet <NUM> to be axially slidably moved within the stylet holder <NUM>.

In the second position, the stylet holder <NUM> is fully threaded into the threaded bore <NUM> of the carrier <NUM> such that the clamping feature <NUM> of the stylet holder <NUM> is received within a tapered bore <NUM> formed in the carrier <NUM>. When the clamping feature <NUM> of the stylet holder <NUM> is engaged with the tapered bore <NUM> of the carrier <NUM>, the tapered bore <NUM> causes the arms of the clamping feature <NUM> to compress toward one another and around the stylet <NUM> such that the stylet holder <NUM> rigidly engages the stylet <NUM>, thereby preventing axial translation of the stylet <NUM> independent of the stylet holder <NUM>.

The stylet holder <NUM> can be advanced into the carrier <NUM> by the threaded engagement between the stylet holder <NUM> and the carrier <NUM>. In addition, the stylet holder <NUM> can include a tool-engaging feature <NUM> (e.g., a recessed hex feature) that can allow a tool (e.g., a protruding hex feature) to engage and force the stylet holder <NUM> to rotate, such as relative to the carrier <NUM>. For example, the stylet holder <NUM> can be forced to rotate in a first direction (e.g., clockwise) relative to the carrier <NUM> in order to move the stylet holder <NUM> to the second position. In addition, stylet holder <NUM> can be forced to rotate in a second direction (e.g., counterclockwise) relative to the carrier <NUM> in order to move the stylet holder <NUM> to the first position.

<FIG> further illustrate a ring <NUM> disposed between the proximal and distal handles <NUM>, <NUM>. The ring can be utilized with any of the embodiments disclosed herein, and acts as a holder for a positioning device, such as a three-dimensional sensor array for use in facilitating navigation during a surgical procedure. As show, the ring <NUM> is generally annular in shape and includes a bore <NUM>, e.g., a threaded bore, formed therein for mating with a positioning device.

<FIG> illustrates an embodiment of tool that can be used to adjust a position of the stylet and to move the stylet holder between the first and second positions. A person skilled in the art will appreciate that the illustrated tool can be used with any of the devices described herein. As shown in <FIG>, the tool can include a positioning handle <NUM> that is configured to mate to a proximal end of the stylet <NUM>. The positioning handle <NUM> can allow a user to advance the distal end of the stylet <NUM> through the stylet holder <NUM>, such as when the stylet holder <NUM> is in the first position (i.e., the stylet <NUM> can translate relative to the stylet holder <NUM>). In addition, the distal end of the positioning handle <NUM> can have a tool feature <NUM> (e.g., a protruding hex feature) that can engage the tool-engaging feature <NUM> of the stylet holder <NUM>. As such, after advancing the stylet <NUM> through at least the stylet holder <NUM>, the positioning handle <NUM> can engage the tool-engaging feature <NUM> of the stylet holder <NUM> and force the stylet holder <NUM> to rotate relative to the carrier <NUM> and form the second position with the carrier <NUM> (i.e., the stylet holder <NUM> rigidly engages the stylet <NUM>).

As shown in <FIG>, the positioning handle <NUM> can include an outer body <NUM> encompassing at least a part of a positioning feature <NUM>. The stylet <NUM> can extend from a distal end of the positioning feature <NUM> and out through a distal end of the outer body <NUM>. The positioning feature <NUM> can include a push button <NUM> that can be depressed in order to disengage the positioning feature <NUM> from the outer body <NUM> and allow the positioning feature <NUM> and stylet <NUM> to translate relative to the outer body <NUM>. As such, the positioning feature <NUM> can vary the length that the stylet <NUM> extends from the positioning handle <NUM>, which can also vary the length of stylet <NUM> that can extend distally from the elongate shaft <NUM> (e.g., after the positioning handle <NUM> has coupled the stylet <NUM> to the stylet holder <NUM>). Although described herein as a push button <NUM>, any number of a variety of features for disengaging the positioning feature <NUM> from the outer body <NUM> can be used, such as, for example, a sliding or threaded feature.

In some embodiments, the push button <NUM> can engage the outer body <NUM> of the positioning handle <NUM> in a number of engagement positions <NUM>. In addition, either the engagement positions <NUM> or the positioning feature <NUM> can include markings <NUM> that can inform a user as to the approximate length the stylet <NUM> extends from the elongate shaft <NUM> based on the type (e.g., length) of bone anchor attached (or to be attached) to the elongate shaft <NUM>. For example, the outer body <NUM> can include a window <NUM> that reveals one of a plurality of markings (e.g., numbers) formed on the positioning feature <NUM>. Each marking can correspond to a length of stylet <NUM> extending distally beyond a distal-most end of the elongate shaft <NUM>. In addition, the markings can correspond to various bone anchor length to be used with the instrument to allow a user to select an appropriate bone anchor and adjust the stylet <NUM> relative to the elongate shaft <NUM> based on the selected bone anchor. For example, the user can select a <NUM> millimeter bone anchor to be implanted in a patient. The user can then set the positioning handle <NUM> (e.g., by pushing the push button <NUM> and moving the positioning feature <NUM>) such that a marking (e.g., shown in the window <NUM>) indicates that the stylet <NUM> is appropriately positioned relative to the elongate shaft <NUM> or bone anchor for a <NUM> millimeter bone anchor attached to the surgical instrument <NUM>. In this position, a predetermined length (e.g., approximately <NUM> millimeter to approximately <NUM> millimeters) of the tip of the stylet <NUM> can extend distally beyond a distal-most end of the bone anchor mounted onto the elongate shaft <NUM>.

In addition, after the stylet <NUM> has been initially positioned relative to the elongate shaft <NUM>, the user can continue to observe the positioning of the stylet <NUM> relative to the elongate shaft <NUM> and bone anchor mounted thereon. For example, while not shown, in some embodiments, the stylet holder <NUM> can include a proximal extension that can include markings corresponding to the length of stylet <NUM> extending distally beyond the elongate shaft <NUM> or bone anchor. Additionally, the proximal handle <NUM> can include one or more viewing windows <NUM> that can allow a user to view the markings along the proximal extension of the stylet holder <NUM> in order to determine the length of stylet <NUM> extending from the distal end of the elongate shaft <NUM> or bone anchor. Although described herein as using markings, such as numbers, to indicate the stylet length to the user, any number of indicia, such as colors, pictures, etc., can be used.

In use, when the stylet holder <NUM> is in the first position (unlocked), the user can manipulate the positioning feature <NUM> to cause the stylet <NUM> to translate relative to the stylet holder <NUM> and along the elongate shaft <NUM>, thereby adjusting a length of the stylet extending from a bone anchor assembly coupled to a distal end of the elongate shaft <NUM>. Rotation of the positioning handle <NUM> can thread the stylet holder <NUM> into the carrier <NUM>, thereby moving the stylet holder <NUM> to the second position (locked). The positioning handle <NUM> can be removed and the stylet <NUM> can be released from the positioning handle <NUM>, such as due to a sliding or snap fit between the positioning handle <NUM> and stylet <NUM>.

<FIG> and <FIG> illustrate another example of a surgical instrument <NUM> for driving a bone anchor assembly into bone. The surgical instrument <NUM> can include an elongate shaft <NUM>, a stylet <NUM>, and a handle assembly <NUM>. The elongate shaft <NUM> can have a proximal end <NUM> and a distal end <NUM>, with a mating feature <NUM> formed on the distal end <NUM> and configured to mate to a bone anchor assembly. The elongate shaft <NUM> can be hollow with an inner lumen that can extend through and along the length of the elongate shaft <NUM>. The stylet <NUM> can extend through at least a part of the elongate shaft <NUM>, such as the inner lumen.

The handle assembly <NUM> can be coupled to a proximal end <NUM> of the elongate shaft <NUM> and can include a proximal handle <NUM> and a distal handle <NUM>. The handle assembly <NUM> can be positioned and sized to allow a user, such as a surgeon, to grasp a part of the handle assembly <NUM> and operate the surgical instrument <NUM>. The handles are reversed as compared to prior embodiments. In particular, the proximal handle <NUM> controls a position of the stylet, whereas the distal handle <NUM> is used for driving a bone anchor assembly into bone.

As shown, the distal handle <NUM> is positioned between the proximal handle <NUM> and the proximal end <NUM> of the elongate shaft <NUM>. The distal handle <NUM> has a proximal portion with a reduced diameter region that allows the proximal portion to be received within a bore <NUM> formed in the proximal handle <NUM>. The proximal portion can include threads <NUM> formed on an external surface thereof that engage with corresponding threads <NUM> formed within the bore <NUM> extending proximally into a distal end of the proximal handle <NUM>. The distal portion of the distal handle <NUM> is enlarged to facilitate grasping, and includes a bore <NUM> formed in a distal-most end thereof for receiving a proximal end <NUM> of the elongate shaft <NUM>. As a result, rotation of the distal handle <NUM> relative to the proximal handle <NUM> will rotate the elongate shaft <NUM>. As further shown, the bore <NUM> formed in proximal handle <NUM> includes a reduced diameter region <NUM> at a proximal-most end thereof for mating with a stylet <NUM>. The stylet <NUM> can be threadably mated within the reduced diameter region <NUM>, or otherwise fixedly mated thereto. As such, rotation of the proximal handle <NUM> relative to the distal handle <NUM> can translate the stylet <NUM> in a proximal or distal direction relative to the elongate shaft <NUM>. Furthermore, rotation of the distal handle <NUM> can rotate the elongate shaft <NUM>.

A mating feature <NUM> can be formed at the distal end <NUM> of the elongate shaft <NUM> and can be configured to engage a bone anchor assembly (e.g., bone anchor assemblies of the type described above with respect to <FIG>). The mating feature <NUM> can include a threaded surface configured to engage corresponding threads formed in the receiver membrane of the bone anchor assembly. The mating feature <NUM> can also include a tip <NUM> disposed distally of the threaded surface configured to engage a drive socket or a proximal surface of the bone anchor or a compression cap (not shown) disposed within the receiver member. The tip <NUM> can have a diameter that is less than the diameter of the threaded portion. The mating feature <NUM> can also be configured to engage a bone tap, or a bone tap can be formed integrally with the elongate shaft <NUM>. One or more bulges <NUM> or areas of increase diameter can be formed along the length of the elongate body to engage and stabilize extension or protective sleeves that can be coupled to the bone anchor assembly.

In use, the stylet <NUM> can translate along a length of the inner lumen of the elongate shaft <NUM> and can extend out from the distal end <NUM> of the elongate shaft <NUM>. In addition, translation of the stylet <NUM> along the inner lumen can allow the length of stylet <NUM> that extends from the distal end <NUM> of the elongate shaft <NUM>, and in particular from a distal end of a bone anchor assembly coupled to the elongate shaft, to vary. For example, distal translation of the stylet <NUM> can allow the length of stylet extending from a bone anchor assembly to increase and proximal translation of the stylet <NUM> can allow the length of stylet <NUM> extending from a bone anchor assembly to decrease. When the proximal handle <NUM> is fully threadably engaged, as shown in <FIG>, the stylet is fully extended from the bone anchor assembly and is at its maximum length.

<FIG> illustrates an example of a protective sleeve <NUM> positioned over a part of an elongate shaft of a surgical instrument, such as the elongate shaft <NUM> of surgical instrument <NUM> described above and shown in <FIG> and <FIG>. The protective sleeve <NUM> can assist with neurotransmitting procedures, such as neuromonitoring navigation. The protective sleeve can act as an insulator that can insulate at least the stylet. By way of non-limiting example the protective sleeve can be formed from one or more of a radio-opaque and radiolucent material, and can include radiopaque markers.

<FIG> illustrates another example of a protective sleeve <NUM> positioned over a part of an elongate shaft of a surgical instrument, such as the elongate shaft <NUM> of surgical instrument <NUM> described above and shown in <FIG>. Although the protective sleeve <NUM> is shown and described as being coupled to the surgical instruments <NUM> and <NUM> shown in <FIG> and <FIG>, any number of surgical instruments, including any disclosed herein, can be coupled with the protective sleeve <NUM>.

The various instruments disclosed herein can be used to perform a variety of surgical procedures.

While exemplary methods are discussed below for delivering a bone screw to a vertebra, a person skilled in the art will appreciate that the instruments can be used to deliver a variety of implants in various surgical procedures. By way of non-limiting example, the instruments can be used to deliver screws to soft tissue or bone throughout a patient's body, in minimally invasive, arthroscope, endoscopic, open, or other surgical procedures.

<FIG> schematically illustrate one exemplary background only methods of using a surgical instrument having a stylet to drive a bone anchor assembly into bone <NUM>. The background method detailed below can be used with any of the instruments disclosed above (e.g., the instruments <NUM>, <NUM>, <NUM>, <NUM>), with any necessary modifications being apparent to one skilled in the art having read the above disclosure. By way of example, the background method is described in connection with instrument <NUM> of <FIG>.

To begin with, an incision can be made to access the bone <NUM> (e.g., a vertebra) to which the bone anchor assembly <NUM> (e.g., a pedicle screw) is to be coupled. The bone anchor assembly <NUM> can be coupled to the instrument <NUM> and advanced through the incision to position the bone anchor assembly in proximity to the bone surface. Prior to, during, or after insertion into through the incision, the stylet <NUM> can be indexed to an initial position based on various parameters such as the length of the bone anchor assembly. This can be accomplished, for example, by rotating the distal handle <NUM> while holding the proximal handle <NUM> fixed, to cause the carrier <NUM> and corresponding stylet <NUM> to translate axially. In other embodiments, for example using the instrument of <FIG>, the stylet can be axially slid relative to the stylet holder prior to locking the stylet to the stylet holder. In some embodiments, the stylet <NUM> can be initially positioned such that the stylet <NUM> protrudes from the distal end of the bone anchor assembly <NUM> by a desired amount. This can be achieved, for example, using the positioning handle <NUM> (e.g., by pushing the push button <NUM> and moving the positioning feature <NUM>) such that a marking (e.g., shown in the window <NUM>) indicates that the stylet <NUM> is appropriately positioned relative to the elongate shaft <NUM>. For example, the positioning handle <NUM> can be set to display a marking that corresponds to a length of the selected bone anchor, such that a predetermined portion of the tip of the stylet extending distally beyond a distal end of the bone anchor attached to the surgical instrument <NUM>. The length can be further adjusted by adjusting the stylet relative to the carrier as may be desired. It will be appreciated that the stylet <NUM> can be initially positioned such that the stylet <NUM> does not protrude from the distal end of the bone anchor assembly <NUM>.

As shown in <FIG>, the protruding stylet <NUM> can be docked into the pedicle <NUM> by tapping or urging the instrument distally towards the bone surface. The distal handle <NUM> can be rotated relative to the proximal handle <NUM>, e.g., in a clockwise direction, in order to cause the stylet <NUM> to mechanically advance into the bone, as shown in <FIG>. Alternatively, or in addition, an impact force can be applied to the stylet <NUM> in the distal direction to advance the stylet <NUM> into the bone. The proper trajectory and depth can be confirmed with fluoroscopy. The insertion depth can also be inferred by the surgeon (e.g., based on the number of rotations of the distal handle <NUM>, audible or tactile feedback, visual feedback provided by graduations or markings, such as shown through the viewing window <NUM> of the proximal handle <NUM>, or based on the carrier hitting a stop disposed in or on the surgical instrument).

Once the stylet <NUM> is advanced to the desired depth, the proximal handle <NUM> can be rotated, e.g., in a clockwise direction, relative to the distal handle <NUM> (i.e., the distal handle <NUM> is held fixed) in order to drive the bone anchor assembly <NUM> along the path created by the stylet <NUM>, as shown in <FIG>. Referring back to <FIG> and <FIG>, rotation of the proximal handle <NUM> while holding the distal handle fixed <NUM> will cause corresponding rotation of the opposed tabs <NUM> on the proximal end of the elongate shaft <NUM>. Since the carrier <NUM> is keyed to the tabs <NUM>, the carrier <NUM> will be caused to rotate in coordination with the tabs <NUM>. As a result, the threaded features <NUM> on the carrier will rotate relative to the threads <NUM> formed in the distal handle <NUM>, which is held stationary. The carrier <NUM> will thus be forced to translate along the opposed tabs <NUM>. Since the threads are reversed as compared to the threads on the bone screw, the carrier <NUM> will move proximally within the distal handle <NUM>, thus moving the stylet <NUM> in a proximal direction relative to the bone screw <NUM>. Since the stylet <NUM> is held fixed against the bone, the stylet <NUM> can be maintained at a constant depth within the bone as the bone anchor assembly <NUM> is advanced distally over the stylet <NUM>. The handle assembly will move distally along the stylet <NUM> in coordination with distal advancement of the bone anchor assembly <NUM>. In embodiments in which the threaded features of the carrier <NUM> and distal handle <NUM> have the same pitch as the threaded portion of the bone anchor assembly, retraction of the stylet <NUM> into the bone anchor assembly <NUM> can occur at the same rate as the advancement of the bone anchor assembly <NUM>, such that the stylet <NUM> remains at a substantially fixed depth within the bone. In embodiments in which the threaded features of the carrier <NUM> and distal handle <NUM> have a smaller pitch than the threaded portion of the bone anchor assembly, retraction of the stylet <NUM> into the bone anchor assembly <NUM> can occur at a slight faster rate than advancement of the bone anchor assembly <NUM>, such that the stylet <NUM> is at least partially retracted in a proximal direction relative to the bone as the bone anchor is driven into bone.

When the bone anchor assembly <NUM> is driven to the desired depth, the stylet <NUM> and the elongate body <NUM> can be detached from the bone anchor assembly and removed from the incision. Subsequent steps, such as affixing a spinal rod or other component to a receiver member of the bone anchor assembly can then be performed.

The bone anchor assembly can include various self-tapping features to facilitate insertion into the bone and to prevent the bone from fracturing during anchor insertion. In some instances, patient anatomy or surgeon preferences can require the bone to be tapped before inserting the bone anchor assembly. In such instances, the above background method can be modified to use embodiments of the surgical instrument that include an integral bone tap or which are coupled to a bone tap via the engagement portion.

As discussed above, a tool can be used to adjust the position of a stylet of an instrument with respect to either an elongate shaft of the instrument or a bone anchor assembly coupled to the elongate shaft. As shown in <FIG>, the tool can include a positioning handle <NUM>, which can be used to adjust the position of the stylet <NUM> relative to an elongate shaft, such as the elongate shaft <NUM> of the instrument <NUM> embodiment shown in <FIG>. Although the positioning handle <NUM> is described herein with respect to the instrument <NUM> embodiment shown in <FIG>, the positioning handle <NUM> can be used with any of the instrument embodiments.

<FIG> schematically illustrate another method (which do not form part of the claimed invention) of using a tool or positioning handle <NUM> with the surgical instrument <NUM> having a stylet <NUM> to drive a bone anchor assembly <NUM> into bone <NUM>. To begin with, a distal end of the positioning handle <NUM> can be removably coupled to a proximal end of the stylet <NUM>, as shown in <FIG>. The length of stylet <NUM> extending from the elongate shaft <NUM> of the instrument <NUM> can be adjusted by pressing the push button <NUM> and sliding the positioning feature <NUM> in a distal direction (e.g., to increase the length) or proximal direction (e.g., to decrease the length). Once the stylet <NUM> length has been set (i.e., the push button is released and engages an engagement position <NUM>), the user can engage the tool feature <NUM> at the distal end of the positioning handle <NUM> into the tool-engaging feature <NUM> of the stylet holder <NUM> in order to rotate the stylet holder <NUM>. The stylet holder <NUM> can be rotated relative to the carrier <NUM> until the stylet holder <NUM> forms the second position with the carrier <NUM> where the stylet holder <NUM> rigidly engages the stylet <NUM> and locks the position of the stylet <NUM> relative to at least the stylet holder <NUM>. The user can then remove the positioning handle <NUM> from the stylet <NUM> (e.g., pull the positioning handle <NUM> off the proximal end of the stylet <NUM>).

The distal end of the instrument <NUM> can then be inserted into the incision and the distal end of the stylet <NUM> can be docked against the bone. The user can then apply a distally directed force on the proximal end of the instrument <NUM> in order to force the stylet <NUM> into the bone. Alternatively or in addition, the user can hold the proximal handle <NUM> and rotate the distal handle <NUM> in order to force the stylet <NUM> in the distal direction and into the bone. Once a desired length of stylet <NUM> has engaged the bone, the user can then rotate the proximal handle <NUM> in order to drive the bone anchor assembly <NUM> into the bone.

Alternatively, the bone anchor assembly <NUM> may not have been attached to the distal end of the elongate member <NUM> prior to insertion of the distal end of the instrument into the incision. A tool (e.g., having a protruding hex feature) can be inserted into the tool-engaging feature <NUM> (e.g., having a recessed hex feature) of the stylet holder <NUM> in order to rotate the stylet holder <NUM> relative to the carrier <NUM> and position the stylet holder <NUM> in the first position. As described above, when the stylet holder <NUM> is in the first position, the stylet <NUM> can move relative to the stylet holder <NUM>. Therefore, the stylet <NUM> can remain in place (e.g., inserted into the bone) and the remainder of the surgical instrument <NUM> can be slid off the proximal end of the stylet <NUM>, as shown in <FIG>. Such a configuration allows various other procedures to be performed at the surgical site without interference from the instrument <NUM>, while at the same time maintaining the position of the stylet. Once the site is ready for anchor implantation, a user can attach a bone anchor assembly <NUM> onto the distal end <NUM> of the elongate member <NUM>. Once the bone anchor assembly <NUM> is attached, the user can lead the proximal end of the stylet <NUM> through the distal end of the bone anchor assembly <NUM> and continue to advance the surgical instrument along the stylet <NUM> until the distal end of the bone anchor assembly <NUM> is in contact with the bone, as shown in <FIG> and <FIG>. The stylet holder <NUM> can then be re-positioned into the second position (e.g., using the tool) in order to secure the stylet <NUM> to the stylet holder <NUM>. The user can then proceed with driving the bone anchor assembly <NUM> into the bone over the stylet <NUM> (e.g., rotating the proximal handle <NUM>), as described above.

When the bone anchor assembly is driven to the desired depth, the stylet <NUM> and the elongate body <NUM> can be detached from the bone anchor assembly <NUM> and removed from the incision. Subsequent steps, such as affixing a spinal rod or other component to a receiver member of the bone anchor assembly <NUM> can then be performed.

The stylet of the various embodiments disclosed herein can be rigid or flexible. The stylet can be formed from a radiopaque material to facilitate visualization under fluoroscopy and other imaging techniques. Other components of the devices disclosed herein (e.g., elongate body portions, handle portions, and the like) can be formed from a radiolucent material so as not to interfere with visualization of the guide projection. Exemplary radiolucent materials include carbon fiber and high-strength polymers. The devices disclosed herein can also be compatible with image-guide surgical systems and with stimulation systems (e.g., neuromonitoring systems typically used to monitor for pedicle breach and to confirm screw or instrument placement).

The devices disclosed herein can provide a number of advantages. For example, in some embodiments, the time required to target and place the bone anchor assembly can be reduced, the radiation exposure to the patient and to the surgical staff can be reduced, and procedural steps such as needle placement, guidewire insertion and removal, and tapping can be eliminated. By way of further example, in some embodiments, inadvertent advancement of instrumentation can be eliminated by controlling the guide projection depth throughout the procedure, risk of removing a guidewire during removal of a needle or tap can be eliminated, and bending or kinking of a guidewire can be prevented.

The devices disclosed herein can be used in minimally-invasive surgery and/or open surgery. While the devices disclosed herein are generally described in the context of advancing a bone anchor into a pedicle, it will be appreciated that the devices disclosed herein can be used with any human or animal bone, implant, non-living object, and so forth.

Claim 1:
An instrument [<NUM>; <NUM>] for driving a bone anchor assembly [<NUM>] into bone,
comprising:
an elongate shaft [<NUM>; <NUM>] having a distal tip configured to couple to a bone anchor assembly [<NUM>];
a handle assembly [<NUM>, <NUM>; <NUM>, <NUM>] coupled to the elongate shaft [<NUM>; <NUM>], the handle assembly [<NUM>, <NUM>; <NUM>, <NUM>] including a first handle [<NUM>] and a second handle [<NUM>] rotatably coupled to one another;
a stylet [<NUM>; <NUM>] extending through an inner lumen of the first handle [<NUM>] and the elongate shaft [<NUM>; <NUM>]; and
a carrier [<NUM>; <NUM>] moveably coupled to the handle assembly,
wherein rotation of the first handle [<NUM>] while the second handle [<NUM>] is held stationary causes the carrier [<NUM>; <NUM>] to non-rotatably translate axially relative to the elongate shaft [<NUM>; <NUM>] to cause the stylet [<NUM>; <NUM>] to axially translate relative to the elongate shaft[<NUM>; <NUM>], and wherein rotation of the second handle [<NUM>] causes the carrier [<NUM>; <NUM>] to rotatably translate and causes rotation of the elongate shaft [<NUM>; <NUM>] to advance the bone anchor [<NUM>] along the stylet [<NUM>; <NUM>].