Patent Description:
In surgery of the spine, a known technique involves the use of Jamshidi needles for inserting Kirschner wires (K-wires) which may be used for the placement of bone anchors such as pedicle screws. According to the known method, first, a small incision is made in the skin of the patient. After that, a Jamshidi needle including a tiny awl is advanced through the incision to the bone. A bore is prepared by hammering and turning the Jamshidi needle back and forth and then the awl is removed. Subsequently, a K-wire is placed into the hole and the Jamshidi needle is removed. A thread cutter is guided by the K-wire to the hole, and a thread is cut with the thread cutter. After cutting the thread, the thread cutter is screwed back. Finally, a cannulated bone screw is guided by the K-wire to and screwed into the threaded hole. As a last step, the K-wire is removed. In total, these steps require the use of several instruments and several instrument passes and may be time consuming, especially in cases where many threaded bores have to be prepared.

A bone anchor insertion device for holding and inserting a bone anchor into the bone, in particular for use with a pedicle screw, is known, for example, from <CIT>. The bone anchor insertion device comprises a holding member with a seat for holding the head of the bone anchor, the holding member having two arms that are configured to encompass the head of the bone anchor, and a drive shaft for engaging the head of the bone anchor to screw the bone anchor into bone, and a displacement member acting onto the holding member such that the holding member can assume a first configuration in which the head can enter the seat and a second configuration in which the head is held in the seat and the shank of the bone anchor can be screwed into bone.

<CIT> describes surgical instruments for delivering bone anchor assemblies into bone. Use of these assemblies can eliminate one or more of the steps in a conventional bone anchor installation procedure. The surgical instrument comprises a handle assembly having an elongate shaft extending distally therefrom. The handle assembly can be configured to axially translate a carrier assembly that secures a stylet extending therethrough. Translation of the stylet can be made relative to a distal end of the elongate shaft.

<CIT> discloses an instrument having an anchor drive assembly and a stylet assembly. The anchor drive assembly has a first handle and an elongate shaft having a distal tip configured to couple to a bone anchor assembly. The stylet assembly has a second handle and a stylet extending through the elongate shaft.

It is an object of the invention to provide an improved instrument that allows the number of surgical steps to be reduced and that makes certain surgical steps more efficient.

The object is solved by a surgical instrument according to claim <NUM> and by a surgical instrument according to claim <NUM>. Further developments are given in the dependent claims.

According to a first aspect an instrument for use in surgery in connection with a bone anchor insertion device includes a hollow shaft configured to connect to the drive shaft of a bone anchor insertion device, a needle holder configured to receive a needle (<NUM>) and to be translated with respect to the hollow shaft, an actuator rotatable with respect to the hollow shaft (<NUM>) and a transmission member configured to be coupled to the needle holder and to convert a rotational movement of the actuator to a translational movement of the needle holder to advance and retract the needle. The transmission member comprises a first advancement structure that is configured to engage a second advancement structure provided at the hollow shaft for effecting the translational movement of the needle holder.

The term needle as used herein includes any elongate member that may extend through a cannulated shank of a bone anchor such as, for example, a Jamshidi needle, an awl, a stylet, a needle of a syringe and others.

With the instrument, the needle can remain at a fixed position during insertion of the shank of the bone anchor in bone. A needle of a fixed length may be used together with bone anchors of different length of the shank. The length of the shank of the bone anchor used with the instrument can be set on a first scale and displayed on the instrument. Moreover, the length of the needle portion that protrudes out of the tip of the shank can be adjusted and displayed on a second scale on the instrument. Hence, an adjustment of the needle position can be carried out easily and safely.

The position of the tip of the needle in the axial direction relative to the tip of the bone anchor can be adjusted in a stepless manner or incrementally. The travel path of the needle may be around <NUM> to <NUM>. Once a position of the needle has been adjusted, this position can be maintained and the shank of the bone anchor can be screwed into the bone. Removal and/or exchange of the needle, if necessary, can be carried out in a simple and time efficient manner. It may also be possible to use the instrument with needles of different type and/or with needles of different length.

The instrument is compact as a cavity formed in the handle portion that drives the drive shaft of the shank inserter is used for housing the needle advancement mechanism and defining the path of translation of the needle holder.

The instrument may be coupled to any bone insertion device, also called shank inserter, which includes a drive shaft to engage and rotate a bone anchor with a threaded shank into bone. Such a shank inserter may have a standard coupling at the rear end of the drive shaft, for example a <NUM>/<NUM> inch square connection portion, that can be coupled to the instrument via a standard coupling used for <NUM>/<NUM> inch connection portions. Hence, the instrument can form a part of a modular system and can preferably be selectively coupled to different shank inserters. Moreover, the instrument may be used together with an adapter carrying a navigation instrument for computer aided imaging and/or navigation or robotics.

With the instrument, various techniques for anchoring the bone anchor in bone may be realized. In particular the instrument may be used in minimally invasive surgery (MIS) and preferably using bone anchors with a self cutting thread.

A not claimed method of use comprises at least the steps of connecting the instrument to a drive shaft of an instrument for inserting a bone anchor into bone before or after connecting a cannulated bone anchor to the drive shaft, inserting a needle into the instrument and fixing the needle, translating the needle via the actuator such that a tip of the needle extends out of the tip of the bone anchor to a desired distance, inserting the needle into bone, preferably further translating the needle relative to the bone anchor to a desired depth and inserting the bone anchor along the needle by rotating the handle portion. Afterwards, the needle may be removed from the bone anchor before removing the shank inserter with the instrument or simultaneously therewith. The method may further comprise a step of setting the shank length of the bone anchor used on a first scale and adjusting the length of the needle that protrudes out of the bone anchor on a second scale.

Further features and advantages of the invention will become apparent from the description of embodiments by means of the accompanying drawings.

Referring to <FIG>, an instrument <NUM> is configured to be used with a surgical instrument, such as a shank inserter <NUM>, that is adapted to insert a bone anchor <NUM> into bone. The bone anchor <NUM> usually has a threaded shank <NUM> with a tip <NUM> and may also have a head (not shown) at the end of the shank <NUM> opposite to the tip <NUM>. For example, the bone anchor may be an element of a polyaxi-al bone anchoring device wherein the head of the bone anchor is held in a receiving part 1a. A needle <NUM> may be used to place the bone anchor <NUM> at the desired position on the bone surface and to prepare a tiny hole in the bone that defines the insertion path for the bone anchor <NUM>. For this purpose, the bone anchor <NUM> may be cannulated so that the needle <NUM> can extend through the bone anchor <NUM> from the head to the tip <NUM>. The shank inserter <NUM> may be any of the known bone anchor insertion devices. Such a shank inserter <NUM> is configured to engage the bone anchor <NUM> usually at the head with a front end of a drive shaft (not shown in detail) so that torque can be transmitted via the drive shaft to the shank <NUM> to screw the shank <NUM> into the bone. The drive shaft may have a connection portion, for example with a polygon outer contour or a square end such as a <NUM>/<NUM> inch connection, at its rear end that is shaped and sized to permit quick connection to and release from other instrument parts, such as a T-handle <NUM> or another type of handle or adapters. A gripping portion <NUM>, such as a thickened portion with axial grooves may also be provided at the shank inserter <NUM>. To allow the use of the needle <NUM>, the drive shaft is cannulated. This permits the needle <NUM> to extend completely through the drive shaft and through the bone anchor <NUM>. It shall be noted that the shank inserter may also comprise only a drive shaft without other holding or counter holding features that engage the bone anchor.

Referring further to <FIG>, the instrument <NUM> can be coupled via a coupling portion <NUM> to the shank inserter <NUM>, more specifically to the drive shaft of the shank inserter <NUM>. The coupling portion may optionally be part of the instrument. The instrument <NUM> includes a hollow shaft <NUM> that is configured to be connected via the coupling portion <NUM> to the drive shaft of the shank inserter <NUM> and that is further configured to be connected to a handle portion <NUM>. The handle portion <NUM> can be rotated by a user whereby the torque is transmitted to the hollow shaft <NUM> and as a result to the drive shaft of the shank inserter <NUM>. A fixation member <NUM> may be used to connect the hollow shaft <NUM> with the handle portion <NUM> in a rotationally and translationally fixed manner. Moreover, the hollow shaft <NUM> is housed at least partially in a cavity of the handle portion <NUM>. A needle holder <NUM> is adapted to be arranged in the hollow shaft <NUM>. The needle holder <NUM> can be translated within the hollow shaft <NUM> via an actuating mechanism to permit a tip <NUM> of the needle <NUM> to be advanced and retracted relative to the tip <NUM> of the shank <NUM> of the bone anchor <NUM>.

The actuating mechanism includes an actuator <NUM> and a transmission member <NUM>. The actuator <NUM> is rotatable relative to the hollow shaft <NUM> and therefore also relative to the drive shaft of the shank inserter <NUM>. The transmission member <NUM> is guided by the actuator <NUM> in such a manner that when the actuator <NUM> is rotated, the transmission member <NUM> follows the rotational movement of the actuator and at the same time advances axially relative to the hollow shaft <NUM>. In addition, the transmission member <NUM> is connected to the needle holder <NUM> in such a manner that the needle holder <NUM> follows the axial advancement of the transmission member <NUM>. Thus, the transmission member <NUM> is configured to convert a rotational movement of the actuator <NUM> into a translational movement of the needle holder <NUM>. By means of this, the needle <NUM> can be advanced and retracted relative to the bone anchor <NUM> independently from a position of the bone anchor <NUM>. An axis of rotation R of the instrument <NUM> which is also a central longitudinal axis of the instrument parts is coaxial with the axis of rotation of the shank inserter <NUM> and the screw axis of the bone anchor <NUM>.

In the following, the parts of the instrument <NUM> will be explained in greater detail. Referring additionally to <FIG>, the hollow shaft <NUM> is an elongate, substantially cylindrical part which comprises a front end 20a and a rear end 20b. The front end 20a faces towards the shank inserter <NUM> when the instrument is mounted to the shank inserter. Moreover, the hollow shaft <NUM> comprises a channel extending through the hollow shaft from the front end to the rear end such that the needle <NUM> can extend fully therethrough. The channel has various sections described hereinafter. Adjacent to the front end 20a, there is a connection portion <NUM> for connecting the hollow shaft <NUM> to the coupling portion <NUM>. The connection portion comprises at the front end 20a a hollow cylindrical section 21a with an outer diameter such that the cylindrical section 21a is configured to be received in the coupling portion <NUM> and with an inner diameter sized to receive a portion of the drive shaft. Adjacent to the cylindrical section 21a, there is a section 21b with a greater outer diameter so that a step 21c is formed therebetween. The step 21c may serve as an abutment for a spring of the connection portion <NUM> (<FIG>). Another abutment for an end surface of the coupling portion <NUM> may be formed by a small outwardly extending annular protrusion 21d adjacent to the front end 20a. The section 21b has close to the step 21c several equidistantly distributed circumferential compartments <NUM> for engagement members, such as balls <NUM>, that are configured to engage a groove of the drive shaft and axially hold the drive shaft while allowing rotation of the drive shaft. At the side of the compartments <NUM> facing towards the rear end 20b, a receiving section <NUM> for receiving the connection portion of the drive shaft is formed that has an inner contour matching the outer contour of the connection section so as to provide a form-fit connection between the drive shaft and the hollow shaft <NUM>. Preferably, the receiving section <NUM> has a standard connection contour such as a quarter inch female square contour. At a distance from the step 21c, a circumferential flange or annular projection <NUM> may be provided that is configured to cooperate with a portion of the actuator <NUM>. A plurality of axial grooves 24a are equidistantly formed in the outer surface of the projection <NUM> which are adapted to be engaged by balls of the actuator <NUM>. Adjacent to the receiving section <NUM> towards the rear end 20b, a narrowed section <NUM> of the channel may have a width that is only slightly greater than an outer diameter of the needle <NUM>. This may provide a guidance of the needle <NUM> once the needle extends through the hollow shaft <NUM>.

The channel then widens towards the rear end 20b into a needle holder receiving section <NUM> which serves for receiving the needle holder <NUM> therein. The needle holder receiving section <NUM> has such a length that the needle holder <NUM> can move therein in an axial direction along a defined length. At least one, preferably four, axially elongate slots <NUM> that are closed at both ends are formed in the wall of the hollow shaft <NUM> equidistantly in the circumferential direction. The slots <NUM> permit pins <NUM> to extend therethrough for holding the needle holder <NUM> as described in detail below. When the pins <NUM> abut against or are close to the rear end of the slots <NUM> which face towards the rear end 20b of the hollow shaft <NUM>, respectively, the needle holder <NUM> is in the rearmost position (<FIG>). When the pins <NUM> abut against or are close to the opposite front end of the slots <NUM>, respectively, the needle holder <NUM> is at the foremost position (<FIG>).

Between the annular projection <NUM> and a position at a distance from the rear end 20b, the outer surface of the hollow shaft <NUM> comprises an advancement structure which in this embodiment is a thread <NUM>. The thread <NUM> is configured to cooperate with an advancement structure provided on the transmission member <NUM> to permit an axial advancement of the transmission member <NUM> along the outer surface of the hollow shaft <NUM>. The outer diameter of this threaded section of the hollow shaft <NUM> may be smaller that that of the annular projection <NUM>. The type of thread depends on the application and the desired dependency between the action of the actuator <NUM> and the advancement of the needle holder <NUM>. Thus, the pitch and the threadform and the number of thread entries may be selected accordingly. A multiple thread may be used for obtaining a greater advancement of the needle. In the embodiment, a thread with three entries is used. Howver, a single thread, a double thread or any other multiple thread may also be applied.

Adjacent to the rear end 20b, a reduced outer diameter section <NUM> with an external thread is formed that is configured to cooperate with an internal thread in a bore of the fixation member <NUM> (<FIG> and <FIG>). In addition, a plurality, more specifically four, axial slots <NUM> extend through the end portion with the outer thread. Thereby posts <NUM> are formed that are configured to extend through corresponding recesses in the handle portion <NUM> to provide a form-fit connection between the hollow shaft <NUM> and the handle portion <NUM>. Thereby, rotation of the hollow shaft <NUM> relative to the handle portion <NUM> is prevented when the fixation member <NUM> is screwed onto the posts <NUM> the hollow shaft <NUM>. It shall be noted that other rotation preventing structures between the hollow shaft <NUM> and the handle portion <NUM> may also be envisaged.

In the following the coupling portion <NUM> which couples the hollow shaft <NUM> to the drive shaft will be described in greater detail. The coupling portion <NUM> is exemplary and any outer suitable coupling can also be used. As best seen in <FIG>, the coupling portion <NUM> is a sleeve-like part and is configured to receive a portion of the hollow shaft <NUM> therein. It has a front section <NUM> adjacent a front end 15a and a rear section <NUM> adjacent a rear end 15b. The rear section <NUM> has an inner diameter such that it fits tightly around the lager diameter section 21b of the hollow shaft and an outer diameter that allows the rear section <NUM> to protrude into a portion of the actuator <NUM>. The front section <NUM> extends around the cylindrical section 21a of the hollow shaft <NUM>. Moreover, the front section <NUM> is flexible, for example by means of axial slits 16a, as best seen in <FIG>, that are open to the front end 15a. The slits 16a and an inner annular projection 16b at the front end enable the front section <NUM> of the coupling portion <NUM> to be snapped over the portion 21a of the hollow shaft <NUM> and abut against the annular projection 21d adjacent to the front end 20a of the hollow shaft <NUM>. In the front section <NUM>, a compartment is formed in which a helical spring <NUM> is accommodated. The helical spring <NUM> extends around the portion 21a of the hollow shaft <NUM> and abuts against the step 21c. By means of this, the hollow shaft <NUM> is biased against the annular projection 16b of the coupling portion <NUM>, so that it is firmly connected thereto. At a distance from the front end 15a, the balls <NUM> are placed into the compartments <NUM> of the hollow shaft <NUM> and extend radially inward to some extent to permit rotation of the hollow shaft <NUM>.

Referring to <FIG> the needle <NUM> and the needle holder <NUM> will be described in greater detail. As depicted in <FIG>, the needle <NUM> includes a thin rod portion <NUM> with a tip <NUM> at the front end. The tip <NUM> preferably is a sharp tip that is suitable for picking a hole into bone. At the side opposite to the tip <NUM>, a holding portion is provided that comprises a cylindrical front portion <NUM>, an intermediate thicker portion <NUM> and a head portion <NUM> at the rear end 4a. Preferably, the rod portion <NUM> and the holding portion are separate parts. A rear end 5b (<FIG>) of the rod portion <NUM> may be mounted to the cylindrical front portion <NUM> of the holding portion, for example press-fit into a bore of the cylindrical front portion <NUM>, so that between the rod portion <NUM> and the cylindrical front portion <NUM> a small shoulder 7a is formed. At the outer surface of the intermediate portion <NUM> two projections 8a, preferably cylindrical projections, extend outward in opposite directions. The projections 8a serve for mounting the needle <NUM> to the needle holder <NUM>. The head portion <NUM> comprises an engagement portion 9a for a tool at its free end. With the tool, such as a driver, the needle <NUM> can be pushed and rotated to mount and release it from the needle holder <NUM>. It shall be noted that the needle can be any suitable needle, such as a Jamshidi needle or a needle having a special tip, such as a tip provided with a sensor.

As shown in <FIG> and <FIG>, The needle holder <NUM> is a substantially cylindrical part with a front end 50a and a rear end 50b. It comprises a channel extending completely through the holder from the front end 50a to the rear end 50b such that the needle <NUM> can be inserted from the rear end 50b with the tip <NUM> and can extend with the rod portion <NUM> all through the needle holder <NUM>. Adjacent to the front end 50a, the channel has a front section <NUM> with an inner diameter large enough to guide the rod portion <NUM> of the needle <NUM> therethrough and housing a biasing member for holding the needle in the needle holder. At a distance from the front end 50a, four threaded radially extending through holes <NUM> are formed equidistantly in the circumferential direction in the wall of the needle holder <NUM>. The through holes <NUM> are configured to receive the connection pins <NUM> (<FIG> to and <NUM> to <NUM>) therein to connect the transmission member <NUM> to the needle holder <NUM>. Each connection pin <NUM> has a threaded front portion 73a that is configured to engage a corresponding one of the threaded holes <NUM> in the needle holder <NUM>. Opposite to the front portion 73a, the connection pins <NUM> comprise a rear end 73b with an engagement structure, such as a slit or a polygonal recess, for screwing in the pin. The threaded front portion 73a has a smaller outer diameter than the remaining pin and such a length, that the connection pin <NUM> can be inserted into the needle holder <NUM> only to such a depth that the needle <NUM> inside the holder is not touched. To limit the insertion, a counterbore 52a at the entrance of the threaded through hole <NUM> may be provided against which a portion of the pin <NUM> abuts. Adjacent to the rear end 50b, a rear section <NUM> for the intermediate portion <NUM> of the needle <NUM> is provided. In the front portion <NUM> of the channel, a helical spring <NUM> is housed between a washer <NUM> that is fixed to the front end 50a and configured to permit the rod portion <NUM> of the needle to pass therethrough and a movable washer <NUM> against which the shoulder 7a of the needle <NUM> abuts.

At the rear end 50b, two axially extending recesses <NUM> that are offset by <NUM>° from each other are formed in the wall of the needle holder <NUM> that permit the projections 8a of the intermediate portion <NUM> of the needle <NUM> to be guided therethrough when the needle <NUM> is inserted. At a distance from the rear end 50b, the recesses <NUM> continue into end portions <NUM> which extend in the circumferential direction, thus are transverse to the axial recesses <NUM>. The end portions <NUM> are extending circumferentially in the same direction of revolution so that, when the projections 8a of the needle <NUM> reach the end portions during insertion of the needle, rotation in one direction moves the projections into the end portions <NUM> of the recesses <NUM>, respectively, and rotation in the other direction moves them out.

Referring to <FIG> and <FIG> as well as <FIG>, the actuator <NUM> will be described. The actuator <NUM> includes a sleeve-shaped actuator wheel <NUM> that has a front end 61a and a rear end 61b wherein in the mounted state, the front end 61a faces towards the connection portion <NUM>. At the front end 61a, a coaxial recess <NUM> may be formed that is configured to receive a portion of the rear end <NUM> of the connection portion <NUM>. Following the recess <NUM>, the inner diameter of the sleeve is such, that the annular projection <NUM> of the hollow shaft <NUM> fits therein and abuts in the axial direction against a step 62a. Between the step 62a and the rear end 61b, the inner diameter of the sleeve is such that the threaded portion of the hollow shaft <NUM> can pass extend therethrough. In the free end surface of the rear end 61b, a plurality, in the embodiment four, equidistantly arranged circumferentially extending slits <NUM> are formed that serve for receiving portions of an actuator tube <NUM> therein, for example in a press-fit manner. The slits <NUM> may have enlarged end portions on both ends, respectively, for facilitating mounting of the actuator tube <NUM>. The outer surface of the actuator wheel <NUM> comprises a gripping structure <NUM> that facilitates gripping and rotating the actuator wheel <NUM>, such as axially extending depressions or grooves.

The actuator tube <NUM> comprises a front end 64a and a rear end 64b and a plurality of axially extending slits <NUM>, in the embodiment four slits. The slits <NUM> are open towards the front end 64a and closed towards the rear end 64b, so that four tube sections <NUM> are formed. The tube sections <NUM> are mounted with the front end 64a into the recesses <NUM> of the actuator wheel <NUM>. Thereby, the actuator tube <NUM> protrudes from the rear end 61b of the actuator wheel <NUM> with a smaller diameter compared to that of the actuator wheel. The length of the actuator tube <NUM> is such that in the mounted state, the rear end 64b of the actuator tube extends up to a small distance from the rear wall of the handle portion <NUM>. When the actuator is mounted to the hollow shaft <NUM>, the mounting pins <NUM> that connect the ring <NUM> with the transmission member <NUM> can extend through the slits <NUM>, respectively.

The actuator <NUM> may be mounted to the hollow shaft <NUM> via a spring biased rotatable connection. As shown in particular in <FIG> and <FIG>, at an axial position corresponding to the position of the annular protrusion <NUM> of the hollow shaft <NUM>, the actuator wheel <NUM> comprises a plurality of equidistantly arranged threaded through holes <NUM>, in the embodiment three through holes. Balls <NUM> are arranged in the through holes <NUM> and are pressed via helical springs <NUM> by the action of set screws <NUM> against the surface of the protrusion <NUM> of the hollow shaft <NUM>. The grooves <NUM> a provide resting positions that can be engaged by the balls <NUM> incrementally when rotating the actuator wheel <NUM>. In other words, when rotating the actuator wheel <NUM>, the balls <NUM> can move out of grooves 24a and snap into the circumferentially neighboring grooves 24a. Thus, a haptic feedback may be given to a user when the actuator wheel is rotated. The actuator wheel <NUM> is prevented from axial movement as it is connected via the actuator tube <NUM> to the transmission member <NUM> and the needle holder <NUM>.

The transmission member is shown in greater detail in <FIG>. The transmission member <NUM> is a sleeve-like part with a front end 70a and a rear end 70b. An internal thread <NUM> configured to cooperate with the external thread <NUM> on the hollow shaft <NUM> is formed on the inner wall of the sleeve to allow the transmission member <NUM> to advance on the hollow shaft <NUM> in the axial direction back and forth. The advancement structure in the form of the thread <NUM> on the transmission member <NUM> and the advancement structure in the form of the thread <NUM> on the hollow shaft <NUM> may be configured such that the distance per revolution which the transmission member <NUM> moves axially corresponds to the distance the shank <NUM> is advanced per revolution of the drive shaft.

The transmission member <NUM> is connected to the needle holder <NUM> via the connection pins <NUM> as shown in <FIG>, so that when the transmission member <NUM> moves along the hollow shaft <NUM> in the axial direction, the needle holder <NUM> within the hollow shaft <NUM> moves together with the transmission member <NUM> in the axial direction. The connection pins <NUM>, in the embodiment there are four pins, extend radially through the slots <NUM> of the hollow shaft <NUM>, respectively. Their rear ends 73b extend into a circumferential groove <NUM> formed in the inner wall of the transmission member <NUM>. Thus, when the transmission member <NUM> advances along the threaded hollow shaft <NUM>, the rear ends 73b of the connection pins <NUM> can rotate in the groove <NUM> of the transmission member <NUM>. The pins <NUM> can be inserted through a mounting hole <NUM> that extends through the transmission member into the groove <NUM>.

At an axial position between the rear end 70b and the groove <NUM>, a plurality, in the embodiment four, equidistantly arranged threaded through holes <NUM> are formed that serve for receiving mounting pins <NUM> for mounting a needle position indication device in the form of a ring or sleeve <NUM> to the transmission member <NUM>. The ring <NUM> has substantially the same axial length and an inner diameter that permits to mount it around the tube portion <NUM> of the actuator <NUM>. The inner wall of the ring <NUM> is threadless, so that it can slide along the tube portion <NUM>. At positions corresponding to the threaded through holes <NUM> in the transmission member <NUM>, the ring <NUM> comprises unthreaded holes <NUM> which permit only a threaded front portion 75a of the mounting pins <NUM> to extend therethrough and engage the threaded holes <NUM> of the transmission member <NUM>. It shall be noted that the ring <NUM> is thinner in the radial direction compared to the transmission member <NUM> as it has to fit into the space between the actuator and the handle portion in the radial direction. In the outer surface of the ring <NUM> a circumferential indication mark <NUM> is provided which may be, for example, a groove, that may be provided with a colouring and/or a coloured ring. Hence, when the transmission member <NUM> moves, the ring <NUM> with the indication mark <NUM> moves in the same way. Therefore, the indication mark <NUM> is configured to display the axial position of the needle holder <NUM> and therefore the axial position of the tip <NUM> of the needle relative to the tip <NUM> of the bone anchor <NUM>. For this purpose, there is a window in the handle portion <NUM> as explained in greater detail below.

Turning now in addition to <FIG>, the handle portion <NUM> will be described in greater detail. The handle portion <NUM> may be an elongate, substantially cylindrical part that has a front end 30a and a rear end 30b. An outer surface portion <NUM> that extends from a position close to the rear end 30b to a distance from the front end 30a comprises a gripping structure such as, for example axial grooves. Between the outer surface portion <NUM> with the gripping structure and the front end 30a, the outer diameter of the handle portion may taper in an tapered portion <NUM> so that the outer diameter of the handle portion <NUM> close to the actuator wheel <NUM> is smaller or has the same size as that of the actuator wheel <NUM>. The handle portion <NUM> further comprises an elongate passage in the form of a cylindrical bore <NUM> extending from the front end 30a to a distance from the rear end 30b. The diameter of the bore <NUM> is such that in the radial direction the hollow shaft <NUM>, the actuator tube <NUM>, the transmission member <NUM> and the ring <NUM> can extend therein.

Adjacent to the rear end 30b a cylindrical recess <NUM> with a bottom 34a is formed that is sized to receive a portion of the fixation member <NUM> (<FIG>). A coaxial opening <NUM> with a reduced inner diameter compared to the diameter of the bore <NUM> is provided in the bottom 34a of the recess <NUM>. The opening <NUM> has four rounded side recesses 35a offset from each other by <NUM>° that are configured to receive the posts <NUM> of the hollow shaft <NUM> in order to connect the hollow shaft <NUM> and the handle portion <NUM> rotationally secured against each other. The posts <NUM> can pass through the side recesses 35a, respectively, so that their ends project out therefrom.

In addition, a window <NUM> is provided in the handle portion <NUM> that exposes a portion of the inside. More specifically, the window <NUM> exposes at least a portion of the ring <NUM> with the marking <NUM>. Thus, the marking <NUM> that is indicative of the position of the needle holder <NUM> can be used for adjusting the position of the needle holder <NUM> and thus the position of the needle <NUM>. The window <NUM> may have a rectangular shape with rounded edges with a length that is greater than the difference of the lengths of the longest and the shortest shank of the bone anchor that can be used plus the length that the needle <NUM> is allowed to move. A groove <NUM> is formed in the wall of the handle portion <NUM> for receiving a shank length indication device in the form of a slide <NUM> that is configured to indicate the possible travel path of the needle holder <NUM> and which serves for setting a shank length of the bone anchor actually used. The groove <NUM> has a substantially rectangular contour and a flat bottom 38a. At the tapered portion <NUM> of the handle <NUM>, the height of outer wall of the groove decreases towards the front end 30a such that a portion of the bottom 38a is free which permits the slide <NUM> to enter the groove <NUM> easily. Inside the groove <NUM> there are protrusions 38b along at least a portion of the legth of the window for cooperating with the slide <NUM>. At the outer wall of the handle portion <NUM> around the window <NUM> are markings <NUM> that are configured to indicate the length of the shank of the bone anchor that can be used. In the embodiment, the length is indicated in increments wherein, for example, even numbers are indicated at one side of the window and odd numbers at the opposite site of the window. For example, if the smallest length of the shank is <NUM> and the greatest length of the shank is <NUM>, the even numbers between <NUM> and <NUM> with an increment of <NUM> are indicated on one side of the window <NUM> and the odd numbers between <NUM> and <NUM> are indicated on the opposite side of the window. The markings <NUM> are arranged such that the smallest length is displayed close to the rear end 30b of the handle portion <NUM> and the displayed length decreases towards the front end 30a.

As shown in <FIG>, the slide <NUM> is comprised of a substantially rectangular flat plate that is configured to be slid into the groove <NUM> and can be moved therein in the axial direction, i.e. along the length axis of the plate that is parallel to the longitudinal axis of the handle portion <NUM>. The slide <NUM> has a front end 90a and a rear end 90b wherein the front end faces in the assembled state when the slide <NUM> is in the groove <NUM> towards the actuator wheel <NUM>. A longitudinal slot <NUM> is formed in the middle of the slide in the transverse direction which may extend almost along the whole length of the slide <NUM>. The slot <NUM> allows to display a portion of the actuator tube <NUM> and the ring <NUM> with the marking <NUM> that are visible through the window <NUM> of the handle portion <NUM>. Hence the slide also forms a needle position indication device. A countersink <NUM> around the slot <NUM> may improve the visibility of the ring <NUM> and may carry markings. On the upper side of the slide that faces outward, a plurality of elongate gripping protrusions <NUM> may be formed that may be arranged along both long sides of slot <NUM> to allow gripping of the slide <NUM> and sliding it in the groove <NUM>.

On the surface of the countersink <NUM> markings <NUM> are provided that can be aligned with the markings <NUM> on the handle portion <NUM> when the slide <NUM> is moved. In greater detail, close to the rear end 90b, a first type of marking 94b may be provided that is configured to be aligned with one of the markings <NUM> around the window <NUM> that indicate to possible shank length. The first type of marking can be, for example, two arrows pointing to the center of the slot <NUM> in the circumferential direction of the handle portion <NUM>, such that, when the slide <NUM> is at a position in which the two arrows are aligned with a marking <NUM> on the handle portion <NUM> the marking 94b indicates the length of a shank of an inserted bone anchor <NUM>. This first type of marking 94b may have a colour, for example green. Moreover, a second type of marking 94a may be provided close to the front end 90a of the slide <NUM>. This second type of marking 94a may indicate the maximum admissible projection of of the needle <NUM> out of the shank <NUM>. In other words, the second type of marking indicates the maximum admissible travel path of the needle holder <NUM> to ensure the maximum admissible projection of the needle. The marking 94a may also comprise two arrows that point with their tips towards each other. A colour of the second type of marking may be red, for example, to indicate the limit of the admissible advancement of the needle <NUM>. Inbetween the first and the second type of markings there may be a third type of marking 94c that may comprise equidistantly spaced apart dashes and/ or dots on each side of the slot <NUM> wherein the markings 94c are offset from each other on one side relative to the other side. The markings 94c may indicate the advancement of the needle in increments.

Generally, the markings <NUM> on the handle portion <NUM> provide a first scale indicative of possible lengths of the shank of a bone anchor <NUM> while the markings <NUM> on the slide <NUM> provide a second scale indicative of the possible positions of the tip <NUM> of the needle with respect to the tip of the bone anchor <NUM>. Lastly, the slide <NUM> comprises on each of the long sides at approximately the middle of the long sides recesses, for example two V-shaped recesses <NUM> in the outer edge of the slide. The recesses <NUM> are configured to cooperate with the protrusions 38b inside the groove <NUM>. Thereby, the adjustment of the markings <NUM> on the slide <NUM> relative to the markings <NUM> on the handle portion <NUM> may be facilitated and the slide may be held in position.

As further depicted in <FIG>, the fixation member <NUM> fits at least partially in the recess <NUM> at the rear end 30b of the handle portion <NUM>. It comprises a threaded bore <NUM> that is configured to be screwed onto the posts <NUM> of the hollow shaft <NUM>. On its side opposite to the rear end 30b of the handle portion <NUM>, the fixation member comprises a tool engagement recess <NUM> for screwing the fixation member <NUM> onto the posts <NUM> of the hollow shaft <NUM>. The inner space between the posts <NUM> of the hollow shaft <NUM> is such that the needle holder <NUM> can extend therein and the threaded bore <NUM> has a size such that insertion and/or removal of the needle <NUM> through the fixation member <NUM> is possible. The fixation member <NUM> is configured to abut against the bottom 34a of the recess <NUM> in the handle portion <NUM> (<FIG>).

The parts and portions of the instrument and/or the bone anchor insertion device, the bone anchor and/or the needle may be made of any material, preferably, however, of a bio-compatible material, such as titanium or stainless steel or any other bio-compatible metal or metal alloy, or plastic material. As bio-compatible alloy, a NiTi-alloy, for example Nitinol, may be used. Other materials can be Magnesium or Magnesium alloys, bio-compatible plastic materials for use may be for example, Polyether ether ketone (PEEK) or Poly-L-lactide acid (PLLA). The parts can be made of the same or of different materials from one another. For the instrument a material that is easy to clean may be preferred.

The needle holder <NUM>, the hollow shaft <NUM>, the transmission member <NUM> with the ring <NUM>, the handle portion <NUM> with the slide <NUM> and the actuator <NUM> are usually preassembled such that their respective front ends face in the direction of the connection portion <NUM>. When the needle holder <NUM> is placed into the hollow shaft <NUM>, the transmission member <NUM> is screwed onto the hollow shaft <NUM> from the rear end thereof and the pins <NUM> are inserted through the mounting hole <NUM>, passed through the slots <NUM> of the hollow shaft <NUM> and screwed into the threaded holes <NUM> of the needle holder <NUM>. The actuator <NUM> is placed with the actuator wheel <NUM> around the hollow shaft <NUM> and the set screws <NUM> are tigthened. The ring <NUM> is mounted around the actuator tube <NUM> and fixed with the mounting pins <NUM> to the transmission member <NUM> and the actuator tube <NUM> is mounted to the actuator wheel <NUM>. After that, the hollow shaft <NUM> is fixed to the handle portion <NUM> via the fixation member <NUM> that is screwed onto the threaded posts <NUM> of the hollow shaft <NUM>. Tightening the fixation member <NUM> firmly fixes the hollow shaft <NUM> to the handle <NUM> so that rotation of the handle <NUM> also rotates the hollow shaft <NUM>. The actuator <NUM> remains rotatable with respect to the hollow shaft <NUM> and with respect to the handle portion <NUM>.

To use the instrument <NUM> with a shank inserter <NUM>, the optional coupling portion <NUM> is mounted to the connection portion <NUM> of the hollow shaft <NUM>. The instrument <NUM> preassembled in this manner can be connected to a shank inserter <NUM>. To accomplish this, the connection portion of the drive shaft is inserted into the connection portion <NUM> of the hollow shaft until it is received in the receiving section <NUM> so that the form-fit engagement allows to transmit torque to the drive shaft. The shank inserter may be already connected to a bone anchor <NUM> to be inserted into bone or the bone anchor <NUM> can be fixed to the shank inserter <NUM> when the shank inserter has been connected to the instrument <NUM>.

In operation, when the actuator wheel <NUM> is rotated, the rotational movement of the actuator tube <NUM> forces the transmission member <NUM> to travel in axial direction via the engagement of the thread <NUM> of the transmission member <NUM> and the thread <NUM> of the hollow shaft <NUM>. Since the transmission member <NUM> is connected via the pins <NUM> to the needle holder <NUM>, the needle holder <NUM> will travel together with the transmission member <NUM>.

The needle <NUM> can be inserted and removed by means of a push and turn action as follows. When the projections 8a are received in the end portions <NUM>, the needle <NUM> is secured against inadvertent removal from the needle holder <NUM>. When the shoulder 7a of the holding portion of the needle <NUM> abuts against the washer <NUM>, the spring <NUM> urges the washer against the shoulder 7a so that the needle <NUM> as a whole is biased in the direction towards the rear end 50b of the needle holder <NUM>. Thereby, the projections 8a are held in the transverse end portions <NUM> of the axial recesses <NUM>. Removal of the needle <NUM> is effected by pushing the holding portion of the needle against the washer <NUM> which frees the projections 8a so that they can be moved out of the transverse end portions <NUM> by rotating the needle in the counter direction. For example, in the embodiment, the end portions <NUM> extend in the counterclockwise direction seen from the read end 50b so that pushing the needle and rotating it in the counterclockwise direction locks the needle <NUM> in the holder <NUM> while pushing it and rotating it in the clockwise direction releases the needle <NUM> from the holder <NUM>. This push and turn action allows a quick and simple mounting and removal of the needle. The rod portion <NUM> may be exchanged or the rod portion together with the entire holding portion of the needle <NUM>.

Referring to <FIG>, in the not claimed clinical use, once a bone anchor with a specific shank length has been selected, the slide <NUM> is adjusted to the position in which its first type marking 94b is aligned with the marking <NUM> which corresponds to the shank length of the bone anchor. In the example shown, a bone anchor with a shank length of <NUM> has been selected and the slide <NUM> has been adjusted correspondingly.

Once the needle <NUM> has been inserted and locked in the needle holder <NUM>, the position of the needle is adjusted with the actuator. By rotating the actuator wheel <NUM> in the clockwise direction, the needle <NUM> is advanced and by rotating the actuator wheel in the counterclockwise direction, the needle is retracted. During adjustment of the position of the needle <NUM>, the marking <NUM> on the ring <NUM> displayed through the window <NUM> and the slot <NUM> indicates the position of the tip <NUM> of the needle <NUM> relative to the tip <NUM> of the bone anchor <NUM>.

As shown in <FIG>, the surgical instrument prepared by this is ready to insert the bone anchor <NUM> into bone, in the example in the pedicle of a vertebra <NUM>. Next, as shown in <FIG>, the bone anchor is placed onto the bone surface and the tip <NUM> of the needle <NUM> is hit into the bone until the needle <NUM> has penetrated the cortical bone.

Next, as depicted in <FIG>, the handle portion <NUM> is held stationary and the actuator wheel <NUM> is rotated in the clockwise direction. Thereby, the needle <NUM> penetrates deeper into the bone. The distance of travel of the tip <NUM> of the needle can be seen by the position of the marking <NUM> of the ring <NUM> relative to the first type marking 94b.

As further shown in <FIG>, once the desired depth has been reached, the actuator wheel <NUM> of the actuator <NUM> is held stationary and the handle portion <NUM> is rotated in the clockwise direction to screw the bone anchor <NUM> over the needle <NUM> into the bone. Preferably, the bone anchor <NUM> is a self-tapping bone anchor that is configured to cut the thread into the bone by itself during rotation.

Finally, the shank inserter <NUM> can be decoupled from the bone anchor <NUM> together with the instrument <NUM> still attached to the shank inserter and the needle <NUM> still extending through the entire device. Alternatively, the needle <NUM> is removed first and the shank inserter <NUM> is released from the bone anchor thereafter.

Since the path, the needle can travel covers about a length of the shank of a usual bone anchor or more, the instrument <NUM> and the same needle <NUM> can be used in connection with different bone anchors having different lengths. The needle position can be monitored during use as it is displayed on the slide <NUM>.

Referring to <FIG>, a second embodiment of the surgical instrument is shown. Identical or highly similar parts and portions are indicated with the same reference numerals and the description thereof is non-repeated. The shank inserter <NUM> and the instrument <NUM> are identical to the previous embodiment. However, between the shank inserter <NUM> and the instrument <NUM> an adapter <NUM> is mounted that has a rear end that is coupled to the hollow shaft <NUM> in the same manner as the drive shaft <NUM> of the previous embodiment. The adapter <NUM> has a front connection portion that is connected to the shank inserter <NUM>. The hollow shaft <NUM> of the instrument <NUM> is coupled to an inner shaft (not shown) of the adapter member <NUM> which is also coupled to the drive shaft of the shank inserter <NUM>. Thus, torque can be transmitted from the handle portion <NUM> through the adapter member <NUM> to the drive shaft <NUM> of the shank inserter <NUM>. A secondary instrument <NUM>, such as a navigation array for optical or any other navigation can be mounted on the adapter member <NUM> via a mounting sleeve <NUM>. The mounting sleeve <NUM> may be, for example, rotatable around the shaft of the adapter member <NUM>. By means of this, while the torque is transmitted via the handle <NUM> to the drive shaft, the secondary instrument <NUM> can be kept stationary by gripping it with the other hand. Thereby, the orientation of the secondary instrument <NUM> such as a navigation array is maintained relative to the navigation system. This may be used for surgery under fluoroscopy or with computer-based navigation assisted systems.

It shall be noted that instead of a navigation array, other secondary instruments can also be used via the adapter member <NUM>.

Referring to <FIG> a further embodiment of the needle holder and the needle is explained. Parts and portions that are identical or highly similar to the previous embodiment are indicated with the same reference numerals and the description thereof is not repeated. The needle <NUM>' is connectable to the needle holder <NUM>' via a threaded connection. For this purpose, the holding portion of the needle <NUM>' comprises between a cylindrical front portion <NUM>' in which the rod portion <NUM> is supported and a rearward head portion <NUM>' an intermediate threaded portion <NUM>' with an external thread <NUM>. The outer diameter of the threaded portion <NUM>' may be greater than that of the cylindrical front portion <NUM>' and may be smaller than that of the head portion <NUM>'.

The needle holder <NUM>' is cylindrical as in the previous embodiment and comprises a coaxial channel for passing through the rod portion <NUM> of the needle <NUM>' and for receiving at least a part of the holding portion of the needle. A front portion <NUM>' of the channel is configured to receive the cylindrical front portion <NUM>' of the needle. A rear portion <NUM>' of the channel comprises an internal thread 53a' that is configured to cooperate with the external thread <NUM> of the holding portion of the needle. The rear portion <NUM>' may be located between the holes <NUM> for the pins <NUM> and the rear end 50b. At the transition between the front portion <NUM>' and the rear portion <NUM>' of the channel a step 51a' may be formed that may serve as an abutment to limit the insertion of the needle into the needle holder <NUM>'. Moreover, when the needle <NUM>' is screwed-in into the needle holder <NUM>', it can be tightened against the abutment. This may result in a strong connection that ensures safety. Between the rear end 50b and the rear portion <NUM>' a coaxial bore 53b may be formed and the head portion <NUM>' may abut against the rear end 50b. The needle holder <NUM>' may be used in the instrument instead of the needle holder <NUM>.

In use, when the needle holder <NUM>' is inserted into the hollow shaft <NUM> the needle <NUM>' can be removed and/or exchanged by means of screwing the needle into and out of the needle holder.

Preferably the needle holder <NUM>' is in the rearmost position for mounting or exchanging the needle <NUM>'. The threaded connection simplifies the handling of the needle and allows quick exchange of the needle.

Claim 1:
Instrument for use in surgery in connection with a bone anchor insertion device wherein the bone anchor insertion device (<NUM>) comprises a drive shaft connectable to a shank (<NUM>) of a bone anchor (<NUM>), the drive shaft comprising a channel for receiving a needle (<NUM>, <NUM>') therethrough;
the instrument including
a hollow shaft (<NUM>) configured to connect to the drive shaft;
a needle holder (<NUM>, <NUM>') configured to receive a needle (<NUM>, <NUM>') and to be translated with respect to the hollow shaft (<NUM>);
an actuator (<NUM>) rotatable with respect to the hollow shaft (<NUM>); and
a transmission member (<NUM>) configured to be coupled to the needle holder (<NUM>, <NUM>') and to convert a rotational movement of the actuator (<NUM>) to a translational movement of the needle holder (<NUM>, <NUM>') to advance and/or retract the needle (<NUM>, <NUM>');
wherein the transmission member (<NUM>) comprises a first advancement structure (<NUM>) that is configured to engage a second advancement structure (<NUM>) provided at the hollow shaft (<NUM>) for effecting the translational movement of the needle holder (<NUM>, <NUM>'), wherein the first advancement structure (<NUM>) is provided at an inner surface of the transmission member (<NUM>) and the second advancement structure (<NUM>) is provided at an outer surface of the hollow shaft (<NUM>).