MODULAR PEDICLE SCREWS, MODULAR PEDICLE SCREW ASSEMBLIES, AND ASSOCIATED METHODS

A pedicle screw and pedicle screw assembly for use in supporting a spinal rod, the pedicle screw including a threaded shank, a screw head, and a screw neck connecting the threaded shank and the screw head. The screw head can include an arcuate upper surface to engage a lower surface of a modular head. A pair of arcuate channels positioned on either side of the screw head can receive a bottom flange portion of the modular head therein so as to secure the modular head to the pedicle screw. An upper surface of the modular head can define a rod recess for receiving the spinal rod. The relative configuration of the screw head and the modular head can be arranged so that once engaged, the modular head is freely slidable along the arcuate upper surface of the screw head, but the screw head and the modular head remain coupled.

TECHNICAL FIELD

The present disclosure relates to surgical spine treatment and methods and, more particularly, modular pedicle screws, modular pedicle screw assemblies, and associated methods used in the field of surgical spine treatment.

BACKGROUND

Surgical techniques for the treatment of spinal injuries or deformities often utilize a process called “spinal fusion,” which joins together two or more vertebrae of the spine. One method of spinal fusion utilizes a fixation system that is anchored to the spine with orthopedic screws that are implanted into pedicles of two or more adjacent vertebrae. The single screws may be connected together with rigid or semi-rigid rods, which rest housed within a transversal channel provided in the screw head. The screws are called pedicle screws, which can be, but are not always, inserted percutaneously (through the skin) into the pedicle of the vertebra. These screws may then be threaded into the bone. After the screws are threaded into place in the pedicle, metal rods are inserted to connect the screws and provide stability to the spine during the fusion process. Typically, the surgeon will use a bone graft to facilitate fusion.

Pedicle screws are generally used in the lumbar (low back) spine, but they can also be used in the thoracic (mid-back), cervical spine (neck) and sacral vertebrae. Typical procedures that use pedicle screws include: transforaminal lumbar interbody fusion (TLIF), posterior lumbar interbody fusion (PLIF), lateral lumbar interbody fusion (LLIF), and anterior lumbar interbody fusion (ALIF).

Due to the irregularity of bone anatomy and various curvatures of the spine, and the difficulties of accurate placement particularly in minimally invasive surgery, it is unlikely that the heads of the screws will be properly aligned for rod insertion after the screws have been implanted into the spine pedicles. Proper screw alignment and orientation allows for placement of the rods so that the stress of the rod is evenly distributed among the screws. If one screw assembly is out of place (misaligned), the rod will unevenly stress the various screw assemblies, which often leads to breakage of the overstressed screw or can also result in the screw loosening (i.e., loss of screw-bone engagement). For example, in some instances the surgeon may have to back the screw out of the pedicle to align the channel or to raise the screw to match the rod level. Both of these maneuvers weaken the bone-screw engagement. In addition, bending the rod too much to match the screw heads may also jeopardize the rod's long-term strength. Instead, in order to facilitate the insertion of the rod and to provide proper alignment of the rod (to alleviate stress on the screws), the screws may often be provided with a head that is freely rotatable with respect to the shank of each screw. This way, after insertion of the screw into the pedicle and before placement of the rod, the surgeon may rotate the various screw heads to achieve the desired alignment to receive the rod.

Currently this screw and rod alignment may be achieved with a poly-axial screw, in which the screw head and shank may be connected via a “ball and socket” mechanism that allows the upper part of the screw to swivel. The upper part of the socket-like cavity may have a locking insert used to clamp the spherical head once the appropriate orientation of the shank has been set. The transversal channel (referred to as a U-shaped channel) for housing the connecting rod may be arranged above the socket-like cavity, and a set-screw may be inserted above the rod in order to clamp the rod into position. Poly-axial screws are an improvement over the uniaxial screws, but the mobility of the head provided by a poly-axial screw requires a reduction in the shank diameter at the shank-head junction. Considering that pedicle screws sustain the largest stress at the shank-head junction, the reduction of the diameter at this region weakens the overall strength of the screw, such that the poly-axial screw introduces further mechanical drawbacks.

SUMMARY

In view of the foregoing, Applicant has recognized that the diameter reduction in the shank can be prevented by increasing the size of the spherical head; however, there is a risk that this construction may lead to a bulky screw design which could impede the usability of the screw during surgery. A smaller shaft also may result in breakage. Accordingly, Applicant also has recognized that a pedicle screw assembly that maintains a larger, consistent diameter along the screw shaft, but also allows rotation at the head and provides the surgeon with the ability to fine tune the alignment of the assembly is desirable. Embodiments according to the present disclosure meet this need, as well as provide additional advantages such as deformity correction and ease of maintenance.

One aspect of the present technology provides a pedicle screw for use in supporting a modular head and a spinal rod connected to the modular head. The pedicle screw can include a threaded shank, a screw head positioned at an upper end portion of the threaded shank, and a screw neck connecting the threaded shank and the screw head. The screw head can include an arcuate upper surface forming a convex slide positioned to engage a pair of rails positioned on a lower surface of the modular head. The screw head can further include a pair of arcuate channels, each of the pair of arcuate channels positioned below the arcuate upper surface on an opposite side of the screw head, each of the pair of arcuate channels positioned to receive a bottom flange portion of the pair of rails of the modular head therein so as to secure the modular head on the pedicle screw. The screw neck can have a circular cross-section and can be positioned to provide a tapered transition between the screw head and the threaded shank.

Another aspect of the present technology provides a pedicle screw assembly for use in supporting a spinal rod. The pedicle screw assembly includes a pedicle screw having a threaded shank, a screw head positioned at an upper end portion of the threaded shank, and a screw neck connecting the threaded shank and the screw head. The screw head can include an arcuate upper surface forming a convex slide positioned to engage a pair of rails positioned on a lower surface of a modular head, and a pair of arcuate channels, each of the pair of arcuate channels positioned below the arcuate upper surface on an opposite side of the screw head, each of the pair of arcuate channels positioned to receive a bottom flange portion of the pair of rails of the modular head therein so as to secure the modular head on the pedicle screw. The screw neck connecting the threaded shank and the screw head can have a circular cross-section and positioned to provide a tapered transition between the screw head and the threaded shank. The pedicle screw assembly can also include a modular head having a rod recess positioned on an upper surface of the modular head so as to receive the spinal rod, and the lower surface of the modular head being positioned to define the bottom flange portion for engagement with the screw head. In addition, the relative configuration of the screw head and the modular head can be arranged so that once engaged, the modular head is freely slidable along the arcuate upper surface of the screw head, but the screw head and the modular head remain coupled to one another.

Yet another aspect of the present technology provides a method of placing a spinal rod. The method can include the steps of threading a pedicle screw shaft into a vertebrae, the pedicle screw shaft having a screw head positioned at an upper end portion thereof, the screw head having an arcuate upper surface forming a convex slide positioned to engage a pair of rails positioned on a lower surface of a modular head. The method can further include attaching the modular head to the head of the pedicle screw so that the modular head is freely slidable along the arcuate upper surface of the screw head in a direction determined by the curvature of the pair of rails engaged with the convex slide. The method further includes the steps of orienting the modular head so that a rod receiver recess positioned on an upper surface of the modular head is positioned to support the spinal rod, and inserting the spinal rod into the rod receiver recess.

In some embodiments, the step of threading a pedicle screw shaft into a vertebrae can include threading a plurality of pedicle screw shafts into a vertebrae, and the step of attaching the modular head to the head of the pedicle screw can include attaching a modular head to a pedicle screw shaft associated with each of the plurality of pedicle screw shafts. In addition, the step of orienting the head so that a rod receiver recess is positioned to support a spinal rod can include orienting each head so that the rod receiver recess is aligned with the rod receiver recess of an adjacent head.

In some embodiments, the method can also include the step of placing the spinal rod into the rod receiver recesses of a plurality of modular heads. In addition, the method can include installing a set screw in the head to fix the spinal rod relative to the head.

An additional embodiment of the present disclosure is directed to a modular pedicle screw assembly kit for stabilizing vertebrae of a spine. The kit can include a container; a pedicle screw positioned in the container; a modular head positioned the container; and a spinal rod positioned in the container. The pedicle screw can have a threaded shank, a screw head positioned at an upper end of the threaded shank, and a screw neck connecting the threaded shank and the screw head. The screw head can include an arcuate upper surface forming a convex slide positioned to engage a pair of rails positioned on a lower surface of a modular head, and a pair of arcuate channels. Each of the pair of arcuate channels can be positioned below the arcuate upper surface on an opposite side of the screw head, and each of the pair of arcuate channels can be positioned to receive a bottom flange portion of the pair of rails of the modular head therein so as to secure the modular head on the pedicle screw. The screw neck can have a circular cross-section and can be positioned to provide a tapered transition between the screw head and the threaded shank. The modular head can have a rod recess positioned on an upper surface of the modular head so as to receive the spinal rod, and the lower surface of the modular head can be positioned so as to define the bottom flange portion for engagement with the screw head.

DETAILED DESCRIPTION

Embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the disclosure are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Like numbers refer to like elements throughout. In describing the different embodiments of the invention illustrated in the appended drawings, specific terminology will be used for the sake of clarity. The technology, however, is not intended to be limited to the specific terms used, and it is to be understood that each specific term includes equivalents that operate in a similar manner to accomplish a similar purpose. Each of the separate descriptions of the parts of the modular pedicle screw assemblies may be used interchangeably with the other described parts.

As shown inFIGS. 1-11, an embodiment according to the present disclosure provides a modular pedicle screw assembly10that can be comprised of a shank100and modular head400. The modular head400can be comprised of a base200and a tulip head300, as illustrated in one embodiment shown inFIG. 2. As will be discussed below with more detail, the base200can include a bottom portion adapted to receive a head of the shank100, and a top portion having a slide201. The tulip head300can include rails304adapted to move along the slide201of the base200.

FIG. 1shows a plurality of modular pedicle screw assemblies inserted into the vertebrae3of a spine according to an embodiment. The shanks100are not visible in the figure as they have been inserted into the pedicles of the vertebrae3. The base200is illustrated coupled to the tulip head300for each modular pedicle screw assembly10, and each series of linearly aligned modular pedicle screw assemblies10is shown being connected by a rod1in order to stabilize the spine. In addition, set screw2is shown inserted into the tulip head300to arrest movement of the rod1after initial alignment adjustments are made. Generally, rods1currently utilized in spinal surgery are made of titanium and are generally about 5-6 mm thick; however the materials and diameter can vary as necessary as long as the tulip head300is sized proportionally to accommodate the rod1.

Referring to an embodiment illustrated inFIG. 2, the shank100can be inserted into the pedicle of the spine according to customary surgical procedures. The shank is often referred to as a screw or pedicle screw, and can be formed of any material and design suitable for insertion into the pedicle of the vertebral arch, which is the segment between the transverse process and the vertebral body. Typically, the shank can include a shaft102having threads101and a screw head103. The screw head103can include a tool engagement profile, such as, for example, a straight slot for receiving a straight screw driver, a T-slot for receiving a Phillips head screw driver, a hex slot for receiving and Allen wrench, or any other appropriate profile for receiving an insertion tool. The length106of the shank, diameter105of the shank, and spacing of the screw threads101can vary as necessary. For example, the shank geometry can be cylindrical (constant diameter) or can be conical (increasing diameter). Generally in the surgery setting, the surgical tray can have a number of different screws that provide a selection of a variety of shank lengths and diameter combinations for use by the surgeon as necessary. The screw head103can be sized to fit inside the base200of the modular head400.

Still referring toFIG. 2, the modular head400can be formed of a base200and a tulip head300. The tulip head300can be configured to interlock with a top portion of the base200. In an embodiment illustrated inFIG. 2, the top of base200can be curved and configured to couple with the complementarily curved underside and grooves of tulip head300. This curvature can allow tulip head300to rotate in an arcuate motion across the top of base200.

In an embodiment, tulip head300can be coupled with base200prior to coupling the base200to the implanted pedicle screw shank100. For example, the pedicle screw shank100can be implanted in the patient to achieve desired placement. The tulip head300coupled to the base200can then be coupled to the implanted pedicle screw shank100to achieve a desired orientation and directionality, before receiving the rod1. The tulip head300can have rails304formed from a side portion306and a bottom flange portion307thereof, such that the rails304are configured to move along the slide201of the base200as illustrated in an embodiment shown inFIG. 4. The rails can define recesses308configured to receive the slide201of the base200.

In order to achieve coupling between the tulip head300and the base200, the slide201can be inserted into the recesses308. Once coupled, the tulip head300can be slid in an arcuate motion across the slide201of the base in either direction in order to achieve a desired orientation of the tulip head300for purposes of receiving a rod1.

In another embodiment, the tulip head300can be coupled to the base200by snapping the tulip head300onto the base200, rather than coupling the two pieces by sliding the tulip head300onto the base200, as discussed above. For example, the bottom flange portion307of the tulip head300can be formed of a material, such as plastic or another suitable composite or material, which is sufficiently bendable to enable the rails304to expand outward as the bottom flange portion307is pressed down onto the top slide201of the base200. Once the rails304have been pushed beyond the outer edges of the slide201, the rails304can snap back into place, securely coupling the rails304to an underside of the slide201. To facilitate the joining of the tulip head300and the base200in this embodiment, corners of the slide201and the rails304can be beveled or rounded. The rails304can then be slid in an arcuate motion in either direction across the slide201of the base in order to achieve a desired orientation of the tulip head300for purposes of receiving a rod1.

In another embodiment, tulip head300can be coupled with base200after base200has been coupled to the implanted pedicle screw shank100. For example, the pedicle screw shank100can be implanted in the patient, either with the base200coupled to the screw head103before implantation, or with the base200being coupled to the screw head103after implantation. In either example, the base200can be snapped onto the screw head103by pressing the shank receiver203of base200down onto and over the top of screw head103. As the shank receiver203is pressed against the top of screw head103, notches204in the perimeter of the shank receiver203can permit the shank receiver203to expand to accommodate the diameter of the screw head103, before snapping back into place once the perimeter of the shank receiver203has cleared the edge of screw head103. In some embodiments, relative movement between the base200and the screw head103can be reduced or eliminated by the provision of a locking feature. Such a locking feature can take the form of the shim310, described above as locking motion between the tulip head and the base, or can take any other appropriate form. In one embodiment, a piece can be inserted through the base200substantially along the axis ASR, and into contact with the screw head. This piece can be aligned with the shim so that when the shim is pushed toward the base by the rod, the shim in turn pushes the piece into contact with the screw head103. Friction between the piece and the screw head can thereby arrest movement between the base200and the screw head103.

After the base200has been coupled to the implanted pedicle screw head103, the tulip head300can be coupled to the base200, according to an embodiment. For example, tulip head300can be coupled to base200by sliding the bottom flange portion307of tulip head300over the slide201of base200at either end of the slide201, as described in more detail above. In either instance, once tulip head300has been coupled to base200, rails304of tulip head300can then be slid in an arcuate motion in either direction across the slide201of the base in order to achieve a desired orientation of the tulip head300for purposes of receiving a rod1. Alternatively, in some embodiments, the tulip head300can be joined to the base200before the base200is coupled to the screw head103. Such pre-assembly of the tulip head300and base200may be more efficient, depending on the circumstances of a particular operation and the positioning of the pedicle screw assemblies10in the spine of a patient.

In an embodiment, one or more portions of the pedicle screw assembly—including the shank100, base200, and tulip head300—can be manufactured in a coupled configuration. For example, base200can be fabricated being coupled to screw head103of pedicle screw shank100, such that a surgeon can implant the coupled screw shank100and base200, without the need for coupling the two pieces either before or after implantation. In order to achieve the desired orientation of the pedicle screw shank100and coupled base200, the surgeon can rotate base200up to 360 degrees around the screw head103until the desired orientation is achieved. After such desired orientation is achieved, the surgeon can couple the tulip head300to the base200and shank100, as described in more detail above.

In another embodiment, base200can be fabricated being coupled to tulip head300, such that a surgeon can couple the base200and tulip head300to the pedicle screw shank100, either before or after implantation. In this configuration, the coupled base200and tulip head300can be coupled to the screw head103of pedicle screw shank100, as described above, and can be rotated on the screw head103up to 360 degrees to achieve the desired orientation. Although pre-coupled to the base200in this embodiment, tulip head300can still be further slid in an arcuate motion across the slide201of base200such that additional adjustments can be made to achieve the desired orientation.

In another embodiment, each of the pedicle screw shank100, base200, and tulip head300can be fabricated being coupled together. In this example, a surgeon can implant the pedicle screw assembly in the patient, and make adjustments to the orientation after implantation. For example, the surgeon can rotate the base200on the screw head103of pedicle screw shank100, up to 360 degrees, and can rotate the tulip head300in an arcuate motion across the slide201of base200until the desired orientation is achieved.

FIGS. 3A-3Cillustrate a configuration of base200according to an embodiment of the present technology. As shown, the base200can be formed of three portions: the slide201, the slide support202, and the shank receiver203, which can be oriented around a shank receiver axis ASR (shown inFIGS. 3A and 3C). The shank receiver203can be the portion of base200that fits over the screw head103of the shank100and mates with the screw head103. The interior dimension206of the shank receiver203can be sized appropriately to receive the screw head103of the shank. Specifically, the shank receiver may include shank receiver sidewalls205and shank receiver ends207. The shank receiver ends can extend radially inward toward the shank receiver axis ASR so as to define a shank receiver recess208(shown inFIG. 3B). The shank receiver recess208is configured to accept the screw head103and, in use, to prevent axial movement of the screw head103relative to the base200.

The base200can provide one axis of rotation, allowing rotation up to 360 degrees about the shank100. The base200can be configured to allow mating to the shank100via the screw head103. The base200can be mated before or after the shank100is inserted into the pedicle of the vertebra3. In some embodiments, the base200can be mated after the shank100is inserted so that the surgeon can use the appropriate tools for inserting the shank100.

For example, after the shank100is inserted into the pedicle, the surgeon can mate the base200with the shank100by snapping the base200on the head103of the shank100of the pedicle screw. The base200can be rotated about the screw head103to provide proper alignment and positioning, providing the first axis of rotation. After the surgeon inserts the shank100into the pedicle, the surgeon can then attach the base200onto the screw head103. The surgeon can then check the orientation of the shank and coupled base against other positioned shank and coupled bases to ensure that all of the respective slides201on the bases are properly orientated with respect to each other. For example, the slides201can be orientated in the same direction (such as parallel to other slides201coupled to a shank inserted into vertebra either superior or inferior to the vertebra where the instant shank and coupled base are installed), as is illustrated in an embodiment inFIG. 1. If the slides are not all properly orientated, the surgeon can rotate the bases about the screw head to achieve proper orientation of the slides. This capability for post-insertion rotation and orienting can provide an advantage over uniaxial screws, which may require the surgeon to back out the shank/screws from the bone in order to achieve alignment with other shanks.

In an embodiment, there can be a locking mechanism that can be installed to lock the base200down onto the screw head103of the shank100once the appropriate position is set. It is preferred, however, that all of the locking connections occur in one step to save on surgery time.

The shank receiver203also can include notches204, as illustrated inFIGS. 3B and 3C. These notches204can be provided for stress relief and expansion of the shank receiver203. When the base200is coupled to the screw head103, the notches204can help the base200expand around the perimeter of the shank receiver203to receive the screw head103of shaft100. Although two notches204are particularly shown in the drawings, more than two notches can be used if desired such as to accommodate bases200formed of different materials having different flexibilities or elasticity.

The slide support202of the base200can be disposed between the slide201and the shank receiver203. The slide201can provide a second axis of movement. In an embodiment, the slide201can be the portion upon which the rails304of the tulip head300move across the slide201of the base, which provides the surgeon the ability to position the tulip head in alignment with other inserted modular pedicle screw assemblies. This way, if the pedicle screws were not positioned precisely in line with other pedicle screws in the pedicles inferior or superior to the instant pedicle during insertion, the surgeon can move the tulip heads300along the slide201in an arcuate motion so that all of the modular pedicle screw assemblies are in alignment to receive the rod. This configuration alleviates the problem of the rod exerting excessive force on any one of the misaligned assemblies, and accordingly reduces instances of breakage of such assemblies or undue stresses on the vertebrae of the patient.

The slide201optionally has “stops” (not shown), which can include either protrusions or recesses to arrest the movement of the rails of the tulip head along the slide201. In addition, after the tulip head300is properly positioned along the slide201, the tulip head300can be locked down by a stop or locking mechanism to arrest relative movement between the tulip head300and the slide201.

Referring now toFIGS. 4A-4D, the tulip head300can have rails304formed from a side portion306and a bottom flange portion307that define recesses308configured to receive the slide201of the base200. This configuration can provide the ability of the tulip head300to move along the slide201and be locked into any position along the slide201. This configuration can also provide a second axis of movement in the modular pedicle screw assembly.

The tulip head300also can have a through-hole305. This through-hole305can be any shape (such as, but not limited to, elongate, oval, round, etc.) and any dimension necessary. A shim310(shown inFIGS. 5A and 5B) can be located within the through-hole305. The shim310can be sized to be taller than the depth of the through-hole305so that the uppermost portion of the shim310extends into the U-shaped channel301of tulip head300. In an embodiment, when the rod1is placed into the U-shaped channel301of the tulip head300, the rod1can contact the shim310first and then contact the bottom surface of the U shaped channel301of the tulip head300. As the rod1is tightened down with a set screw2, the rod1can push the shim310down and apply a significant friction on the slide201, thereby locking the tulip head300in a single orientation in place on the base200. Although the shim310is shown to be cylindrical in shape, it can be any appropriate shape. In addition, the shim310can be coupled with the tulip head300so that it will not fall off or become disengaged from the tulip head300during assembly or when the tulip head300is handled separately by a surgeon. In one example embodiment, the through-hole305can be threaded to receive threads of a threaded locking mechanism.

The tulip head300can be configured to include hips303, which can provide support and structure around the U-shaped channel301. Although shown in certain figures to be conical in shape, the tulip head300can be any appropriate shape, including, for example, cylindrical. The U-shaped channel301can be configured to receive a rod1, which can be a stabilizing member used in spinal surgery to stabilize the spine. The width302of the U-shaped channel301can be sized to receive a rod1that is customarily used in the spinal stabilization surgery. Typically the rod can be about 5-6 mm in diameter and is can be composed of titanium or any other appropriate material.

The tulip head300can be configured to include rails304that are able to move along the slide201of the base200. This configuration can provide flexible and accurate placement and orientation so that when the surgeon installs the rod1in the U-shaped channel301after inserting the shank100into the pedicle, the tulip head300can be moved along the slide201to allow for proper alignment of the rod1. In addition, as noted earlier, the base200can be rotated to be in appropriate orientation and alignment so that the surgeon does not need to back out the shank from the pedicle for proper positioning.

The dimensions of the overall tulip head300and its various components (i.e., the width302of the U-shaped channel301, the width312and height309of the tulip head300) can be sized appropriately for use in standard medical protocols using pedicle screws. The side of the rails306and the bottom flange307of the rails can be sized to allow movement along the slide201of the base200. In addition, the rails306and bottom flange307can be sized to have sufficient strength to function without breaking during an expected life once implanted within a patient. In the drawings, principally for the sake of clarity, all side walls intersecting orthogonally are shown to have 90 degree corners (e.g. the inner walls of the rails308). During the manufacturing process, however, such intersections may have a slight rounding due to the limitations of the machines producing the devices.

As illustrated inFIGS. 5A and 5B, in some embodiments the tulip head300can have threads315within the U-shaped channel301to mate with threads of a set screw2(seeFIG. 1), which is inserted on top of the rod1to hold the rod1in place once inserted into the U-shaped channel301. The tulip head300can optionally have recesses316for grabbing the tulip head300with a tool during surgery.

According to some embodiments of the present technology, tulip heads300can be configured such that the U-shaped channel301runs parallel with the rails304, as shown in an embodiment illustrated inFIG. 6A, or the U-shaped channel311can be configured to run perpendicular to the rails304, as shown in an embodiment illustrated inFIG. 6B. A surgeon may utilize both of these orientated tulip heads300selectively as needed to allow placement of the rod in order to reduce the amount of stress on the rod and the modular pedicle screw assembly.

Some embodiments may also include a dual U-channel tulip head330, as illustrated in an embodiment shown inFIGS. 7A-7D. In such embodiments, there can be two U-shaped channels301and311. One U-shaped channel301can be configured to run parallel with the rails304, while the other U-shaped channel311can be configured to run perpendicular to the rails304.FIG. 7Calso shows a top view of the dual U-shaped channel tulip head with the four prongs, andFIG. 7Dshows a perspective view of the dual U-shaped channel tulip head. In this embodiment, instead of using a set screw2that is placed and threaded inside the tulip head300to fix the rod1, a ring313can be placed on the tulip head300to encompass the four prongs332. The ring313can engage threads331positioned on the outside surface of the prongs332. The ring can be threaded outside the circumference of the tulip head300on the perimeter threads331to provide strength and stability to the tulip head300and to prevent the tulip head300from spreading open under excessive loading.FIGS. 8A-8Dprovide four depictions of a dual U-channel tulip head300rotated to accommodate different orientations to receive the rod, according to an embodiment of the present technology.

FIGS. 9A-9Eshow a two-part, rotatable tulip head340having an upper section350including the U-shaped channel301, and a lower section375including the rails304, according to an embodiment. This embodiment allows the upper section350to rotate about the lower section375, where the upper section capable of rotating up to 360 degrees independently of the lower section375. Upper section350and lower375can be mated together, for example, by screwing the upper section350into a threaded portion of the lower section375, or by any other appropriate means.FIGS. 9C-9Eshow the lower section375(i.e., the female end) configured to receive the upper section350(i.e., the male end351). In another embodiment, the upper section350can be configured to receive the lower section375(i.e. the lower section375can be configured to have the male connector and the upper section350can be configured to be the female receiver).

FIGS. 9A and 9Bshow a side perspective view of three modular pedicle screw assemblies, where one of the assemblies includes a two-part, rotatable tulip head340, according to an embodiment of the present technology.FIG. 9Ashows that the two part, rotatable tulip head340can be positioned along the base200.FIG. 9Bshows the two-part, rotatable tulip head340rotated about the lower section375. The multiple axes of movement provide improved flexibility to the surgeon for aligning the U-shaped channel301to any desired orientation and alignment.

FIGS. 10 and 11are flowcharts illustrating a method of achieving alignment of the U-shaped channels in the modular pedicle screw assemblies discussed above to allow placement of the rods within the aligned an oriented U-shaped channels. This ensures that the rod does not exert undesired pressure upon any of the assemblies, which would occur if they were not in the desired alignment or orientation.

As shown inFIG. 10, a surgeon can insert a pedicle screw shank into a pedicle of a patient's vertebrae. After the surgeon inserts the shank into the pedicle, the surgeon can attach the base onto the screw head. The surgeon can then check the alignment and orientation of the shank and coupled base against other implanted and positioned shank and base assemblies to ensure that all of the slides on the bases are properly orientated or positioned and aligned as desired, (as shown inFIG. 1). If the slides are not all properly oriented or positioned, the surgeon can reposition the bases by rotating the bases about the screw head to achieve proper orientation of the slides. The surgeon can then optionally install a locking mechanism to ensure the base does not move after alignment.

Pedicle screws are often not aligned perfectly on a single plane and are usually tilted and offset with respect to each other, as illustrated, for example, in the embodiments shown inFIGS. 12A-12CandFIGS. 13A-13B. For example, the surgeon may need to rotate one of the modular pedicle screw assemblies relative to a neighboring modular pedicle screw assembly.FIG. 13Bshows an embodiment in which one modular pedicle screw assembly is rotated so the base can be about 90 degrees offset from the other modular pedicle screw assembly. Also, because of the curvature of the spine, the screws can be positioned in such a manner that causes them not to be aligned on a single plane, as illustrated inFIGS. 12A, 12B, and 13A. Such deviation in the orientation of presently available pedicle screw assemblies is problematic, since the titanium rods may only be bent and curved so much to accommodate the necessary deviation. The present disclosure provides solutions to this problem.

For instance, the surgeon can utilize a mixture of two different tulip heads: one with a parallel orientated U-shaped channel320and the other with a perpendicular orientated U-shaped channel350, as illustrated in an embodiment described above and shown inFIGS. 6A and 6B.

In another embodiment, the surgeon can utilize a dual U-shaped channel tulip head330. As described above, this dual U-shaped channel tulip head330can have dual U-shaped channels301,311—one perpendicular and one parallel to the rails—as described above and shown inFIGS. 7A-8D.FIGS. 8A-8Dprovide four depictions of a dual U-shaped channel tulip head330rotated to accommodate different orientations that could be required to receive the rod. When using a dual U-shaped channel tulip head330, preferably a ring313can be placed (via threading or otherwise) around the perimeter of the tulip head to ensure that the walls of the tulip head do not spread open under excessive loading. It is also possible to use a set screw2that is threaded inside the tulip head (such as that shown inFIG. 1) to fix the rod in place.

In another embodiment, the surgeon can employ the use of a two-part, rotatable tulip head340, such as that described above and shown inFIGS. 9A-9E, which can be configured to rotate up to 360 degrees on the base to provide ultimate flexibility to the surgeon for aligning the U-shaped channel to any desired orientation.

A surgeon could then use any of the tulip heads described herein together (for example, use a dual U-shaped channel tulip head330with the two-part, rotatable tulip head340) to provide flexibility in positioning the pedicle screw assemblies to accommodate the rod and to provide many positions and orientations without requiring bending and curving of the rod.

Referring again to the method illustrated inFIG. 10, after the shank and base are installed, the surgeon can install the tulip head onto the base200. The surgeon can then check that the U-shaped channels in the tulip heads are in a desired alignment and orientation relative to one another. If the tulip heads are not in the desired orientation, they may be repositioned to achieve the desired orientation. For example, the entire tulip head may be rotated in an arcuate motion across the slide of the base, for example as illustrated by the arrows inFIG. 5A, or a top portion of the tulip head may be circularly rotated around a bottom portion of the tulip head in another embodiment, or a combination thereof.

Once the desired alignment and orientation is achieved, the surgeon then can employ a locking mechanism to arrest movement of the tulip head along the slide of the base. The surgeon can also install the rod into the U-shaped channels of the tulip heads. If desired, the surgeon can recheck the position of the rod and make any necessary adjustments of the tulip head and/or base to ensure proper alignment and orientation. The rod can also be bent as necessary. Once satisfied with the position of the rod, the surgeon can then insert and tighten down a set screw on the rod to hold the rod in place within the U-shaped channel of the tulip head.

As shown inFIGS. 13-20, and in particular inFIG. 14, in another embodiment, the modular pedicle screw assembly20can include a pedicle screw500having an arched head600and a tulip head300. The tulip head300can be any of the tulip heads as described above, including parallel U-shaped channel tulip heads320, perpendicular U-shaped channel tulip heads325, dual U-shaped tulip heads330, and two-part, rotatable tulip heads340. In the illustrated embodiment, the pedicle screw500can have an arched head600integrally formed thereon, instead of having a typical, flat-topped screw head configured to couple to a separate arched base. The arched head600provides the slide601upon which the rails304of the tulip head300can slide, for example as illustrated by the arrows inFIG. 16, to allow the surgeon to fine tune the positioning and alignment for proper positioning for receiving the rod1into the U-shaped channel301of the tulip head300. The arched head has the slide portion601and the slide support602.

The arched configuration seen in the arched head600, as well as in the base200, can provide the ability to achieve a desired orientation, given the natural curvatures of the spine and the different sizes of vertebrae. When pedicle screws are placed in pedicles, they may be orientated at slightly different angles, such that the rods connecting these screws may be slightly bent or curved before placement.

Referring back toFIG. 11, there is shown another method for achieving a desired alignment and orientation of the U-shaped channels using embodiments of modular pedicle screw assemblies discussed above with regard toFIGS. 13-21. The method ofFIG. 11allows placement of the rods within the aligned U-shaped channels to ensure that the rod does not exert undue or unwanted pressure upon any of the assemblies, which would occur if they were not in the desired alignment and orientation.

As illustrated inFIG. 11, the surgeon can insert the shank into the pedicle and position the shank so that the slides are in the desired orientation and alignment relative to other positioned shanks. This ensures that all of the slides are orientated as desired, as illustrated in the embodiment shown inFIG. 13. The surgeon can then install the desired tulip head onto the arched head. The surgeon can next check that the U-shaped channels in the tulip heads are in the desired alignment and orientation with other U-shaped channels. Once the desired alignment and orientation is achieved, the surgeon can, if desired, employ a locking mechanism to arrest movement of the tulip head along the slide of the arched head. The surgeon can then install the rod into the U-shaped channels of the tulip heads. If desired, the surgeon can check the position of the rod and make any necessary adjustments to the tulip head (as well as bend the rod if necessary) to ensure the desired position (alignment and orientation) of the rod. Once satisfied with the position of the rod, the surgeon can then insert and tighten down a set screw over the rod to hold the rod in place within the U-shaped channel of the tulip head.

InFIG. 21there is shown yet another embodiment of the present technology, including a shank700having a screw head703(shown inFIGS. 24 and 25). As in the above-described embodiments, the screw head703is configured to engage a base800. The screw head703can include a tool engagement profile, such as, for example, a straight slot for receiving a straight screw driver, a T-slot for receiving a Phillips head screw driver, a hex slot for receiving and Allen wrench, or any other appropriate profile for receiving an insertion tool. The base800can include a slide801for sliding connection with a tulip head, as described above, and a shank receiver803. The shank receiver803can be substantially symmetrical about the shank receiver axis ASR of the base800(shown inFIG. 22). In some embodiments, relative movement between the base800and the screw head703can be reduced or eliminated by the provision of a locking feature. Such a locking feature can take the form of the shim310, described above as locking motion between the tulip head and the base, or can take any other appropriate form. In one embodiment, a piece can be inserted through the base800substantially along the axis ASR, and into contact with the screw head703. This piece can be aligned with the shim so that when the shim is pushed toward the base by the rod, the shim in turn pushes the piece into contact with the screw head703. Friction between the piece and the screw head can thereby arrest movement between the base800and the screw head703.

As shown inFIG. 22, the shank receiver803can include shank receiver sidewalls805, oriented substantially parallel to the shank receiver axis ASR, and shank receiver ends807, attached to ends of the shank receiver sidewalls, and oriented substantially perpendicular to the shank receiver axis ASR. The shank receiver ends807may extend radially inward toward the shank receiver axis, thereby defining a shank receiver recess808. The shank receiver recess808includes a recess shoulder816in a corner thereof adjacent a first end817of the shank receiver recess808. In some embodiments, the shank receiver ends807are designed to circumscribe the screw head703, and have an inner circumference809large enough to allow passage of the screw head703into the shank receiver803such that the shank receiver803substantially circumscribes the screw head703.

Referring now toFIGS. 22 and 23, there is shown a ring810configured for positioning in the shank receiver recess808. The ring810is substantially circular, and has an outer surface811and an inner contoured surface812. The inner contoured surface tapers gradually from a first end813of the ring810, and abruptly from a second end814of the ring810. The abrupt nature of the taper at the second end814of the ring801forms a step815in the ring810. The ring810can also include a ring notch804, which allows the ring810to flex, so that the circumference of the ring can expand and contract. The ring can be composed of a material with sufficient elasticity that the ring returns to a rest circumference after expansion once the force is removed. In some embodiments, the ring may be composed of titanium, steel, or any other suitable material. The ring could similarly include varied geometry, such as a design that allows for increased flexibility of the ring.

FIG. 24shows a screw head703according to an embodiment of the present technology. The screw head703includes an external contour with first and second flat portions713,714, and a depressed curved section715. The depressed curved section715of the screw head703tapers gradually from the second flat surface714, and abruptly from the first flat surface713. The abrupt nature of the taper near the first flat surface713forms a shoulder716in the screw head703. The depressed curved section715of the screw head703is configured to substantially align with the inner contoured surface812of the ring810, so that when the depressed curved section715of the screw head703is positioned adjacent the inner contoured surface812of the ring810, the surfaces mate.

FIG. 25shows a shank700, screw head703, base800, and ring810in a made up assembly. During assembly, which may be accomplished during surgery, such as when the shank700is inserted in to the spine of a patient, or pre-surgery, before the shank700is inserted, the screw head703is inserted into the shank receiver803of the base800. Because the inner circumference of the shank receiver ends807is slightly larger than the diameter of the screw head703, the screw head703is able to pass the shank receiver ends807without resistance from the shank receiver ends807themselves.

During assembly, the ring810is positioned within the shank receiver recess808, and is configured so that the inner contoured surface812of the ring810extends radially inward from the circumference of the shank receiver ends807toward the shank receiver axis ASR. As the screw head703passes into the shank receiver803, it contacts the ring810and exerts an upward and a radial force on the ring810. The upward force pushes the ring away from the first end817of the shank receiver recess808and out of contact with the recess shoulder816. The radial force simultaneously expands the ring to allow passage of the first flat portion713of the screw head703through the ring204. Once the first flat portion713of the screw head703passes the ring810, the depressed curved section715of the screw head703aligns with the inner contoured surface812of the ring810. Upon alignment of these features, the elasticity of the ring810causes the ring810to contract so that the inner contoured surface812engages the depressed curved section715of the screw head703. Simultaneously, the shoulder716of the screw head703engages the step815of the ring810, thereby locking the screw head703in place within the shank receiver803.

FIGS. 26-32illustrate another embodiment of a pedicle screw and a modular pedicle screw assembly. As shown, the modular pedicle screw assembly20can include a pedicle screw500having an arched head900and a tulip head300. The tulip head300can be any of the tulip heads as described above, including parallel U-shaped channel tulip heads320, perpendicular U-shaped channel tulip heads325, dual U-shaped tulip heads330, and two-part, rotatable tulip heads340. In the illustrated embodiment, the pedicle screw500can have an arched head900integrally formed thereon, instead of having a typical, flat-topped screw head configured to couple to a separate arched base. The arched head900provides the slide901upon which the rails304of the tulip head300can slide to allow the surgeon to fine tune the positioning and alignment for proper positioning for receiving the rod1into the U-shaped channel301of the tulip head300. In particular, the curvature of the arched head900can allow the tulip head300to rotate in an arcuate motion across the top of the arched head900of the pedicle screw, as illustrated with the arrows shown inFIG. 27, for example, for purposes of receiving the rod1. The arched head has the slide portion901and the slide support902, where the slide support902can also be referred to as the screw neck.

In some embodiments, for example as illustrated inFIGS. 26-31, the threaded screw shank502may be tapered, with a greater diameter adjacent the arched head900and a lesser diameter adjacent a lower end portion of the threaded screw shank502. In other embodiments, for example as illustrated inFIG. 32, the threaded screw shank502may be formed having a consistent diameter along the length of the shank502. A consistent diameter may be easier to manufacture using standard lathe and milling operations, as will be understood by one of ordinary skill in the art.

In some embodiments, the threaded screw shank502may include one or more cutting flutes501positioned at a lower end portion of the shank502. These one or more cutting flutes501may facilitate screw entry into the bone during implantation. AlthoughFIG. 32illustrates a cutting flute501positioned on a threaded screw shank502having a consistent diameter, in other embodiments threaded screw shanks502having tapered diameters, for example as illustrated inFIG. 26-31, may include one or more cutting flutes501positioned thereon.

The arched configuration seen in the arched head900can provide the ability to achieve a desired orientation, given the natural curvatures of the spine and the different sizes of vertebrae. When pedicle screws are placed in pedicles, they may be orientated at slightly different angles, such that the rods connecting these screws may be slightly bent or curved before placement.

As illustrated in the embodiments shown inFIGS. 26-32, the arcuate slide901can be positioned on an upper surface of the arched head900so as to engage with the bottom flange portions307of the rails304positioned on a lower surface of the tulip head300. In addition to the arcuate slide901, the arched head900of the pedicle screw may also include a pair of channels903positioned below the slide901on opposite sides of the arched head900. These channels903may also have an arcuate shape, and may be shaped and positioned so as to receive and engage the bottom flange portions307of the rails304positioned on the lower surface of the tulip head300. The arrangement of the channels903below the slide901and above the rail supports904may allow the bottom flange portions307of the rails304of the tulip head to securely engage the tulip head300with the arched head900of the pedicle screw. During implantation, the surgeon may need to manipulate the modular pedicle screw assembly in a relatively rough manner in order to achieve proper alignment and to secure the one or more rods. This manipulation may otherwise compromise the connection between the tulip head300and the arched head900of the pedicle screw. The inclusion of channels903and rail supports904strengthens this connection to allow for such manipulation without risking disconnection of the tulip head300from the arched head900of the pedicle screw. The channels903may additionally help to minimize the size of the arched screw head900.

The present disclosure is also directed to a modular pedicle screw assembly kit, for example as illustrated inFIG. 33. In an embodiment, the kit may include a container1000housing each of the components of a modular pedicle screw assembly20needed to stabilize vertebrae of a spine, including a pedicle screw500, a modular head300, and a spinal rod1. Although illustrated as a simplified, open-faced, molded rectangular container inFIG. 33, in various embodiments the container1000may take any shape, form, or size as is useful in the storage and presentation of a modular pedicle screw assembly, as will be readily understood by one of ordinary skill in the art.

The modular head300may be any tulip head or modular head as described herein, for example as illustrated inFIGS. 2, 4A-4D, 6A-6B, 9A-9E, 15-20, and 26-31, and as described in detail above. The pedicle screw500may include any base200or screw head600,900as illustrated and described herein. In some embodiments, the container1000may include one or more of each of the pedicle screw500, modular head300, and spinal rod1, in any number or combination as needed for a particular vertebral stabilization procedure. The container1000may be formed in any shape or size, and in any material, appropriate and effective for the sterile storage of the modular pedicle screw assembly components, as will be readily understood by one of ordinary skill in the art.

The present application is a Continuation in Part of and claims priority to International Application No. PCT/US2018/025300, filed Mar. 29, 2018, titled “MODULAR PEDICLE SCREW ASSEMBLIES AND ASSOCIATED METHODS,” which claims priority to, and the benefit of, U.S. Provisional Patent Application No. 62/479,285, filed Mar. 30, 2017, titled “MODULAR PEDICLE SCREW ASSEMBLIES AND ASSOCIATED METHODS,” each of which is incorporated herein by reference in its entirety.