Patent Description:
The present invention relates to orthopedics and more precisely to orthopedic tools and systems including pedicle screws, rods and corresponding set screws. The invention also relates to instruments which are used for manipulating these elements, and methods (not claimed) of using these elements, to apply a torque to a set screw.

In the field of orthopedics and implant tools and systems for orthopedic surgery, more specifically spinal fusion surgery for a spinal column, set screws are used to push down and attach a rod-type or bar-type device to a head of a pedicle screw. The process of pushing down the spinal rod towards and into the head of pedicle screw is also called rod reduction. Before attaching the rod to the head of the pedicle screw, the pedicle screw is attached to a vertebrae with a bone anchor, threaded bone-engaging part or bone screw for fastening the pedicle screw to the vertebrae of a patient or living being. For this purpose, as an example, for several adjacent vertebrae for vertebrae fusion, for each vertebra a pedicle screw is attached thereto, and thereafter, several pedicle screws are mechanically fastened towards each other by the use of the rod that is placed in a groove or U-shaped opening that is formed by the pedicle screw head, forming a row of pedicle screws along the spine. This allows to provide for the mechanical support needed for spinal stabilization for spinal fusion in a patient or living being.

For example, <CIT> describes an orthopedic implant kit that provides for a pedicle screw, a corresponding set screw, a rod, and the tools to operate these, including a screw extender for holding the pedicle screw, and a set screw driver for threadably tightening the set screw relative to screw head of pedicle screw. As another example, <CIT> describes another type of kit orthopedic surgery system for surgical intervention for spinal stabilization, including pedicle screw with a head for receiving a rod, and tools necessary for the surgical intervention. In yet another example, <CIT> provides for a system and method for delivering a spinal connector spinal anchor sites in a spinal column. In one embodiment, a spinal implant and access device is provided that includes a U-shaped receiver member, a bone-engaging member, an extension member, a spinal rod, and a set screw.

Similar orthopedic spinal surgery concepts, tools and devices have been proposed as discussed above, for attaching a rod to a pedicle screw via a set screw, for example <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>. <CIT> relates to a drive train that includes a torque multiplier assembly and a single torque limiter device.

However, the state of the art tools still present specific problems when a surgeon or operator of the spinal surgery tools needs to attach the rod to the pedicle screw by means of the set screw, specifically to find the right amount of torque that needs to be applied to the set screw under different circumstances. Therefore, despite all of the solutions currently proposed in the state of the art related spinal surgery tools, strongly improved methods, systems and devices for spinal surgery are strongly desired.

The present invention concerns a set screw driver according to claim <NUM> and an orthopedic implant kit for tightening a set screw to a head of a pedicle screw according to claim <NUM>, while preferred embodiments are set forth in the dependent claims.

The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description with reference to the attached drawings showing some preferred embodiments of the invention.

The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain features of the invention.

Herein, identical reference numerals are used, where possible, to designate identical elements that are common to the figures. Also, the images are simplified for illustration purposes and may not be depicted to scale.

According to one embodiment, as exemplarily shown in <FIG> and <FIG>, an orthopedic implant kit, instrument kit, tool kit, or system <NUM> is provided, including a handle <NUM>, a first torque limiting or indicating device <NUM>, a set screw driver <NUM> that may include the second torque limiting device <NUM> that can be turned by handle <NUM>, a second counter handle <NUM>, a screw extender <NUM>, the second counter handle <NUM> engaging with set screw driver <NUM>, a set screw <NUM>, a pedicle screw <NUM> with screw head <NUM> and bone anchor or threaded part <NUM>, and a spinal rod <NUM>. In the variant shown, first torque limiting mechanism or device <NUM> that limits an application of a torque to a first torque level T1 is an integral part or is affixed or otherwise operatively connected to a first handle <NUM>, for example a T-handle, that is used to tightening a set screw <NUM> to a head <NUM> of the pedicle screw <NUM> via a set screw driver <NUM>. The first torque level T1 is a torque that is applied to set screw <NUM> relative to a head <NUM> of pedicle screw <NUM>, for example when set screw <NUM> is threadably engaged with a head <NUM> of a pedicle screw <NUM>, and also by abutting or otherwise fastening a spinal rod <NUM> to head <NUM> of pedicle screw <NUM>. First handle <NUM> can have the torque limiting mechanism device <NUM> can be removably attached to the set screw driver <NUM> for tightening the set screw <NUM> can be used as the first torque limiting mechanism, for example a handle <NUM> that attaches to an end of upper shaft <NUM>, proximal end, or another part of set screw driver <NUM>. Such handles with a torque limiting mechanism <NUM> for tightening a screw are described in <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, and <CIT>. A screw extender <NUM> or screw head holder is affixed to screw head <NUM> of pedicle screw <NUM>, and a counter handle <NUM> is in turn attached to screw extender <NUM> for counter torque purposes, when tightening set screw <NUM> relative to screw head <NUM>.

The application of the right amount of torque to a set screw <NUM> that is being tightened against a spinal rod <NUM> held by a head <NUM> of a pedicle screw <NUM> is important and depends on the specific circumstance during the orthopedic surgical operation. Also, an angulation of the tightening of set screw <NUM> is also an important aspect, which can translate into higher amount of torque which then can be transmitted to the surrounding tissues creating risk of screw loosening, implant breakage and/or risk of adjacent segment disease. The present embodiments describe a solution to the fact that a user, operator or surgeon needs to apply different levels of torque during the surgery, and provides for a mechanism that simplifies the task substantially. See for example the publications <NPL>, and <NPL>.

In a variant, as shown in <FIG>, it is possible that a first handle <NUM> is used having a torque indication mechanism <NUM>, instead of a mechanism <NUM> that physically limits the applicable torque to set screw <NUM>, but makes some type of indication that the first torque level T1 has been reached, for example but not limited to a visual, haptic, tactile, vibratory, mechanical, audible noise for example a clicking noise or beep, or combination thereof, or other type of feedback that can be seen, heard, or sensed by the user or operator, or any combination of these features. This can be done with or without any device that actually limits the physical torque applied to set screw <NUM>. For example, a first handle <NUM> can be used that incorporates a torque measurement mechanism that is associated with a torque indicator, scale, or gauge <NUM>. For example, handles <NUM>, wrenches, screwdrivers, drivers, instruments, keys, tools, or sockets that are based on the operational principles as described in <CIT>, <CIT>,<CIT>,<CIT>, <CIT>,<CIT>,<CIT>, <CIT>, and <CIT> and similar mechanisms can be used for the purpose of tightening set screw <NUM> via set screw driver <NUM>, and simultaneously alerting or otherwise indicating the user or operator that a first torque level T1 has been reached.

First torque level T1 can be specifically designed for the application to blockable poly-axial screws, for example poly-axial pedicle screws that can be blocked by a pressure caused by the tightening of the spinal rod <NUM> via set screw <NUM>, as shown exemplarily in <CIT>, <CIT>, and <CIT>. Another variant is the Medtronic™ CD Horizon Solera pedicle screw system that allows for such blocking, having a blocking ring or seat that urges against the spherical head of pedicle screw. In this variant, first torque level between set screw <NUM> and screw head <NUM> is such that rotational motions of spinal rod <NUM> around its own axis are blocked, when tightened to torque level T1 within screw head <NUM> of pedicle screw <NUM>, for example such that a surgeon, user, or operator cannot turn or otherwise rotate rod <NUM> within groove of screw head. However, with torque level T1, the pedicle screw <NUM> still maintains its polyaxiality, as the pressure onto upper or side surfaces of spherical part of bone anchor <NUM> and the blocking ring or seat are not sufficient to block polyaxiality. Preferably, first torque level T1 is approximatively in a range between <NUM> and <NUM>, more preferably about <NUM>.

Next, a second torque limiting mechanism <NUM> that limits an application of a torque to a second torque value or level T2 to the set screw <NUM> relative to the head <NUM> of pedicle screw <NUM> can be integrated in to the set screw driver <NUM>, as shown in <CIT>. For example, as shown in the cross-sectional view of <FIG>, set screw driver <NUM> includes an upper shaft <NUM> which end can engage with a first handle <NUM>, <NUM>, <NUM>, for example by different mechanical connection types, with the lower shaft <NUM> being hollow for accommodating a torque driver <NUM>. An engagement tool <NUM> of torque driver <NUM> can protrude from lower face or distal part of lower shaft <NUM>, to be able to engage with set screw <NUM> for threadable tightening relative to screw head <NUM>, with a screw engagement mechanism <NUM>. Torque driver <NUM> and lower shaft <NUM> are blocked relative to each other by a breakable pin <NUM> that traverses at least a portion of both lower shaft <NUM> and torque driver <NUM>, forming a second torque limiting mechanism <NUM> that mechanically limits the amount of torque that can be applied to set screw <NUM> via handle <NUM> to the second torque level T2, relative to screw head <NUM> of pedicle screw <NUM>. In the variant shown, torque driver <NUM> is formed by an inner bolt, rod, or shaft that is surrounded at a lower section by the lower shaft <NUM>.

The second torque level T2 is the final torque that will be applied to rod <NUM> and screw head <NUM> via set screw <NUM>, and is substantially higher than the first torque level. Because the second torque level is the final level that will be applied to the set screw <NUM>, the torque limiting mechanism can be irreversible or can be such that no higher torque levels can be applied to set screw <NUM>. Preferably, the second torque level T2 is approximatively in a range between <NUM> and <NUM>, more preferably about <NUM>.

Set screw driver <NUM> has an outer threading that can threadably engage with an inner threading of screw extender, having the same thread pitch as the threading of the set screw. This allows the user or operator to place set screw <NUM> onto the front portion of torque driver <NUM> of set screw driver <NUM>, and then threadably engage with inner threading of screw extender <NUM>, to turn or rotate set screw <NUM> together with set screw driver <NUM> down through the screw extender, until set screw <NUM> makes contact and threadably engages with inner threading of head <NUM> of pedicle screw <NUM>. When set screw <NUM> is threadably affixed within the head <NUM> and set screw driver <NUM> is continued to be rotated or turned by a handle <NUM>, <NUM>, once frontal face FF of the set screw <NUM> touches spinal rod <NUM>, the torque increases, up to a point where the pin <NUM> breaks. Pin <NUM> is designed and dimensioned to withhold a torque up to the second torque level T2, and will break upon exceeding the second torque level T2. Once the pin <NUM> is broken, a further rotation of set screw driver <NUM> has therefore no more effect on the rotation and threadable engagement of set screw <NUM> within head <NUM> of pedicle screw <NUM>, as torque driver <NUM> will not be rotated by set screw driver <NUM> anymore. In other words, set screw driver <NUM> can freely rotated without rotating torque driver <NUM>. Therefore, when the second torque limiting mechanism <NUM>, in the variant shown the breakable pin, is activated or in force, i.e. the second torque level T2 has been reached and pin <NUM> is broken, when user or operator rotates set screw driver <NUM> by a holding handle <NUM>, set screw driver <NUM> will threadably be advancing downwards towards the set screw <NUM>, without turning set screw <NUM>. In turn, pedicle screw <NUM> will be progressively pushed away and released from screw extender <NUM>. Second handle <NUM> is removably attached to screw extender <NUM>, so that the user or operator can tighten set screw <NUM> into head <NUM> of pedicle screw <NUM> with one hand, whilst holding head <NUM> of pedicle screw via screw extender <NUM> and second handle <NUM>. This operational principle of second torque limiting mechanism <NUM> that is integrated to set screw driver <NUM> is also shown with Figures 13A-13C, <NUM>, and <NUM> of <CIT>. It is also possible that the second torque limiting mechanism is combined with a torque indicating mechanism, or does not limit the torque to torque level T2, but only indicates it.

The first torque limiting mechanism <NUM> or the first torque indicating mechanism <NUM> are preferably designed such that the first torque level T1 is smaller than the second torque level T2 that is applied by the second torque limiting mechanism <NUM>, for example by a factor that is bigger than five (<NUM>). This means that in case a first torque limiting mechanism <NUM> is used with handle <NUM>, once the first torque level has been reached, the applicable torque to set screw <NUM> cannot be increased anymore by handle <NUM>. Therefore, this requires that a user or operator to remove handle <NUM> from set screw driver <NUM>, and replace handle <NUM> by placing another handle, for example handle <NUM> with a mechanism that limits the torque to a second, higher torque level T2, a handle <NUM> having only a torque indication mechanism <NUM> or another type of handle <NUM> with no torque limitation or indication to set screw driver <NUM>, so that the second, higher level of torque can be applied to set screw <NUM>, until the second torque level T2 is reached. In case handle <NUM> is used, the same handle can be used to apply the first level of torque T1 and the second level of torque T2, for example by having a scale showing the two different torque levels T1 and T2.

As another example, a torque limiting mechanism or device <NUM> can be a separate device that is not integrated to handle <NUM>, <NUM>, but can be placed between the handle <NUM> and set screw driver <NUM>, for example a handle <NUM> that is not equipped with different types of torque limiting or indicating mechanisms, as shown in <FIG>. For example, torque limiting mechanism <NUM> or device can be embodied to be removable connected to upper shaft <NUM> or proximal end of set screw driver <NUM> and handle <NUM>, <NUM>, for example embodied as a mechanical connection element having a ratchet-type or bendable lever or tab that engages with a dented portion, further including two interconnection elements for interconnection between handle <NUM> and set screw driver <NUM>. In this respect, it is possible to use two different torque limiting mechanisms or devices <NUM> in this arrangement, one for torque level T1 and one for torque level T2, and the two mechanisms or devices can be visibly marked as such. As another variant, it is possible that the torque limiting or indicating mechanism <NUM>, <NUM>, <NUM>, is part or integrated to upper shaft <NUM> or proximal end of set screw driver <NUM>, at an area where the handle <NUM> would be connected to the screw extender <NUM>.

In another variant, it is possible to integrate or connect a torque limiting mechanism or torque indicating mechanism measuring or applying torque limitation between handle <NUM> and screw extender <NUM>, or by having one torque limiting or torque indicating mechanism measuring or applying torque limitation between handle <NUM> and screw extender <NUM>, and one torque limiting or torque indicating mechanisms measuring or applying torque limitation between handle <NUM>, <NUM>, <NUM> and set screw driver <NUM>.

In another variant, as shown in <FIG>, a first torque indicator mechanism is integrated into set screw driver <NUM> together with the second torque limiting mechanism <NUM>, being a breakable pin. In this variant, set screw driver <NUM> includes a cylindric hollow area in a lower section <NUM> that accommodates torque driver <NUM> having an engagement tool <NUM> at the distal end for engaging with set screw <NUM>, but also an middle cylindrical shell, tube, or cylinder <NUM> that is located between lower section <NUM> of set screw driver and torque driver <NUM>. The first torque indicator mechanism is arrange to mechanically collaborate between torque driver <NUM> and middle cylindrical shell <NUM>, with a blocking bolt <NUM> that engages with a transversal slot <NUM>, and a first breakable pin <NUM> that traverses both torque driver <NUM> and middle cylindrical shell <NUM>. In a first position, a rotational or turning movement between torque driver <NUM> and middle cylindrical shell <NUM> is blocked by first breakable pin <NUM>, limiting the torque that can be applied to a first torque level T1. For this purposes, first breakable pin <NUM> is dimensioned and designed to break at an application of a torque between torque driver <NUM> and middle cylindrical shell <NUM> at the first torque level. In other words, the breaking of pin <NUM> can be considered the release of a first torque retention mechanism that is embodied by pin <NUM>. In a second position, rotation between torque driver <NUM> and middle cylindrical shell <NUM> is again blocked by wall <NUM> of transversal slot <NUM>.

The first position is represented in <FIG> with different cross-sectional views <NUM>, <NUM>, <NUM> along a center axis of set screw driver <NUM>. Upon application of a low torque below first torque level T1 with set screw driver <NUM>, for example with a handle <NUM>, <NUM>, blocking bolt <NUM> abuts against side wall <NUM> of the traversal slot <NUM>, and first breakable pin <NUM> is not broken yet. Upon exceeding the first torque level T1 between torque driver <NUM> and middle cylindrical shell <NUM>, first breakable pin <NUM> will break, as shown in <FIG> in cross-sectional view <NUM>. This will create a mechanical jolt or jerk to the set screw driver <NUM> that can be felt by the user, and will also create a audible click or snap that can be heard by the user, and can serve as a signal to the user that the first torque has been reached, as a first torque indication mechanism. Next, blocking bolt <NUM> will move from being in contact with side wall <NUM> and will move through traversal slot <NUM> to abut and be again blocked by the other side wall <NUM>, to transition from the first position to the second position, by a rotation of a specific angle defined by a length of traversal slot <NUM> between torque driver <NUM> and middle cylindrical shell <NUM>, as shown with three cross-sectional views <NUM>, <NUM>, <NUM> of <FIG> representing the second position. Blocking bolt <NUM> will then abut against one a side wall <NUM> of the traversal slot <NUM>.

Middle cylindrical shell <NUM> and lower section <NUM> of set screw driver <NUM> are still blocked together with second breakable pin <NUM> that require a higher, second torque level T2 to break. In this respect, pin <NUM> can be considered a second torque retention mechanism that holds the two elements <NUM> and <NUM> together until the second torque level T2 is reached, and will release upon reaching second torque level T2. In this respect, as an example, one or two (<NUM>) or more second breakable pins <NUM> are arranged at <NUM> degrees respect to each other to lock a rotation of set screw driver <NUM> having a lower section <NUM> relative to middle cylindrical shell <NUM>, up to an application of the higher, second torque level T2. In a variant, there can be several breakable pins <NUM>. For controlled breaking, it is preferable that there is only one second breakable pin <NUM>.

Instead of pins <NUM>, <NUM>, other types of breakable, bendable, releasable, retrainable devices can be used that upon application of a specific torque threshold level can release a rotational blockage between middle cylindrical shell <NUM> and set screw driver <NUM> at second torque level T2 to form the second torque retention mechanism, or between torque driver <NUM> and middle cylindrical shell <NUM> at first torque level T1 to form the first torque retention mechanism, for example but not limited to breakable plates, breakable hooks, levers, ratchet-type fastening elements that can release upon application of a threshold torque, dented structures.

In addition to the breaking of first breakable pin <NUM>, and the slipping of bolt within transversal slot <NUM>, which results in torque driver <NUM> turning by a limited angle relative to middle cylindrical shell <NUM>, an additional mechanism can be provided to further alert the user, operator, or surgeon operating the set screw driver <NUM> that the first torque level has been reached. In the variant shown, during the transition from the first position to the second position by blocking bolt <NUM>, in other words the slipping of bolt <NUM> from wall <NUM> to <NUM> of slot <NUM>, protrusions <NUM> to lower side wall or upper side wall of transversal slot <NUM> are made such that the passing of blocking bolt <NUM> over these protrusions <NUM> will create a clicking or ratcheting noise, and also depart a vibration that can be heard and felt by the user, operator, or surgeon. In the variant shown, a plurality of thin longitudinal slots <NUM> are arranged that start from a lower or upper side wall of transversal slot <NUM>, having small protrusions <NUM> on the top, the protrusions designed to let blocking bolt <NUM> transition from the first position to the second position with little additional torque, being a torque that is smaller or substantially smaller than the first torque level T1, and thereby making a vibration or ratcheting noise when blocking bolt <NUM> passes over these protrusions <NUM>.

Other mechanism can be used to create an additional indication to the user, operator or surgeon that the first torque level T1 has been reached, for example as shown in <FIG>, where a lever <NUM> having teeth, dents, or arranged in parallel to lateral extension of transversal slot <NUM> that engages with teeth, dents, cogs, pinions, ratchets <NUM> of blocking bolt <NUM>, that will create a ratcheting noise and a vibration, upon transition from the first position to the second position. Another example is shown in <FIG>, with two levers <NUM> that are symmetrically arranged on both the upper and lower side of transversal slot <NUM>, with bolt <NUM> having a square or rectangular cross-section, with the levers <NUM> having sawtooth shape, to ensure that the transition from the first position to the second position can only happen once and in one direction. The direction of the saw teeth will prevent moving bolt <NUM> back through transversal slot <NUM>. Instead of levers, it is possible that a portion of middle cylindrical shell <NUM> has an edge with saw teeth, waves or triangular teeth, and a portion of the bolt <NUM> has corresponding saw teeth, waves or triangular teeth, respectively that are urged together by a spring mechanism. The biasing force of the spring mechanism that urges the corresponding teeth together can be designed to provide for the first torque level T1.

With the above embodiment, the breaking of first breakable pin <NUM> or the clicking of bolt <NUM> against rough, dented, or jagged structures such as lever <NUM>, or protrusions <NUM>, <NUM>, while bolt <NUM> is transitioning through transversal slot <NUM>, or both of these combined, create an audible, clicking, and vibratory feedback to user, operator, or surgeon that is operating handles <NUM>, <NUM> and handle <NUM> to tighten set screw <NUM> with both of his hands, to reach and exceed first torque level T1, without the need to use different handles or the use of scales with the need of reading a torque level. The breaking of first breakable pin <NUM> will give a small jolt, clicking, or cracking noise, while the dented structures will depart a vibration and a clicking noise, to make sure that the user will be certain that the first torque level on set screw <NUM> has been reached. In addition, the dented structures can also provide for mechanical retention against the rotational movement between torque driver <NUM> and middle cylindrical shell <NUM>, and can serve as torque limiting mechanism for first torque level T1 by themselves.

As of another variant, there is no first breakable pin <NUM> present, but the protrusions <NUM> or the lever <NUM> or a ratchet-like element are designed to block the slipping of blocking bolt <NUM> within transversal slot <NUM> to provide for a mechanical retention, upon application of a torque between torque driver <NUM> and middle cylindrical shell <NUM>, until the first torque level T1 is reached, where bolt <NUM> moves, transitions, or slips to the side wall <NUM> of transversal slot <NUM>. Lever <NUM> and its length and mass, protrusions <NUM>, <NUM>, and longitudinal slots <NUM> can be designed to depart a specific acoustic sound that is hearable audible by user, surgeon, or operator, when bolt <NUM> slips through transversal slot <NUM>. Without the first breakable pin <NUM>, it is possible to turn back torque driver <NUM> relative middle cylindrical shell <NUM>, so that the first position is reached again, to have a reversible mechanism to indicate the first torque level. In this respect, the first torque limiting mechanism and the first torque indicating mechanism could be integrated into a common arrangement, for example by a ratchet-type arrangement with one or more dents engaging with a saw-tooth or waved structure, as described above.

In the context of the present invention, with the first breakable pin <NUM> and the other types of retention mechanisms shown in <FIG> and <FIG> with longitudinal slots <NUM> and protrusions <NUM>, or in <FIG> with levers <NUM> and protrusions <NUM>, <NUM>, <NUM>, different arrangements are described that are herein called a first torque retention mechanism, that can serve as an indicator when the first torque has been surpassed or reached, or as a torque limiter to limit application of the first torque to the first torque level, or both.

According to an example, a method (not claimed) of placing a spinal rod <NUM> into a series of heads <NUM> of pedicle screws <NUM> and the tightening or fastening of set screws <NUM> to these heads is provided, as illustrated in <FIG>. In these figures, showing different stages of the method, by an example showing three pedicle screws <NUM> to <NUM> attached to three vertebrae V1 to V3, but it is also within the scope of this embodiment that a different number of pedicle screws <NUM> to <NUM> and a different number of vertebrae V1 to V3 are used. These figures schematically and exemplarily show three adjacent vertebrae V1 to V3, each having a pedicle screw <NUM>, <NUM>, and <NUM>, respectively, attached thereto, with respective bone anchor <NUM>, <NUM>, and <NUM>. Before what is shown in <FIG>, none of the screw heads <NUM>, <NUM>, and <NUM> of pedicle screws <NUM>, <NUM>, and <NUM> have spinal rod <NUM> inserted therein. As shown in <FIG>, user starts by placing the left side of spinal rod <NUM> into screw head <NUM> by moving spinal rod <NUM> in direction B1 such that rod <NUM> is placed into U-shaped groove of head <NUM>, and then threadably but loosely attaches a set screw <NUM> to screw head <NUM>, to make sure that rod <NUM> does not exit U-shaped groove of screw head <NUM>. Generally, spinal rod <NUM> will have a pre-bent shape that will be desired shape of the spinal column for fusion, so that adjacent vertebrae V1 to V3 will be urged to a desired arrangement next to each other by spinal rod <NUM>.

Next, as illustrated in <FIG>, set screw <NUM> is threaded down into screw head <NUM> to abut against rod <NUM> and is threadably attached to head <NUM> by first torque level T1, by using the instruments or tool kit <NUM> as described above, and at this time, the pre-bent rod <NUM> lies inside the U-shaped grooves of both adjacent heads <NUM> and <NUM>. After this, user threadably but loosely attaches a set screw <NUM> to screw head <NUM>. Next, as illustrated in <FIG>, set screw <NUM> is threaded down into screw head <NUM> to abut against rod <NUM> and is threadably attached to head <NUM> by first torque level T1, again by using the instruments or tool kit <NUM> as described above. After this, user threadably but loosely attaches a set screw <NUM> to screw head <NUM>.

Thereafter, as shown in <FIG>, set screw <NUM> is threaded down into screw head <NUM> to abut against rod <NUM> and is threadably attached to head <NUM> by first torque level T1, again by using the instruments or tool kit <NUM>. At this stage, all the pedicle screws <NUM>, <NUM>, and <NUM> are attached to rod <NUM>, by set screws <NUM> to <NUM> that are tightening by a torque at the first torque level T1. Next, as shown in <FIG>, starting from the left side to the right, each set screw <NUM>, <NUM>, and <NUM> is tightened at the second torque level T2, to finalize the spinal stabilization with spinal rod <NUM>. This is done by using the second torque limiting feature of tool kit <NUM>. For each set screw <NUM>, <NUM>, and <NUM>, a different tool kit <NUM> is used. Generally, as the spinal rod <NUM> has a pre-bent shape, spinal rod <NUM> can be placed into two or more pedicle screw heads at once, and the sets screws <NUM> to <NUM> are thereafter tightening one-by-one in series, from either direction along spinal rod <NUM>. With this method (not claimed), it is possible to reduce the tightening steps into a single instrument kit, even to a single instrument itself as described above, permitting substantial operation time savings and costs.

Claim 1:
An orthopedic implant kit (<NUM>) for tightening a set screw (<NUM>) to a head (<NUM>) of a pedicle screw (<NUM>), the kit comprising:
a screw extender (<NUM>) for holding the head (<NUM>) of the pedicle screw (<NUM>);
a set screw driver (<NUM>) for engaging with the set screw (<NUM>) to threadably tighten the set screw (<NUM>) relative to the head (<NUM>) of the pedicle screw (<NUM>);
a first torque limiting mechanism (<NUM>) for limiting a torque between the set screw driver (<NUM>) and the screw extender (<NUM>) to a first torque value (T1), or a first torque indication mechanism for indicating that the first torque value (T1) has been reached between the set screw driver (<NUM>) and the screw extender (<NUM>);
the kit being characterized in that it further comprises
a second torque limiting mechanism (<NUM>) for limiting a torque between the set screw driver (<NUM>) and the screw extender (<NUM>) to a second torque value (T2), the second torque value being higher than the first torque value.