Compression-distraction spinal fixation system and kit

Compression-distraction spinal fixation systems, and methods of performing compression-distraction spinal fixation, are provided that include screw-rod constructs having a ratcheting mechanism. Bone screws of the screw-rod constructs can have a pawl that engages ratchet teeth on the rod of the screw-rod construct. The bone screw can be unidirectionally ratcheted along the length of the rod to apply compressive or distractive forces. Tools for manipulation of the screw-rod constructs are also provided, which tools include distal tips configured to engage the bone screws.

BACKGROUND

1. Field of Invention

The present technology relates to an implant for surgical treatment of the spine, and methods for stabilizing a spine using the implants. More particularly, the present technology provides compression-distraction spinal fixation systems that include screw-rod constructs.

2. Discussion of Related Art

Anterior, posterior and lateral spinal fixation is commonly used for the treatment of degenerative disease, trauma, deformity, and oncological processes. The current state of the art includes the placement of rigid bone screws into the posterior arch, pedicles or vertebral bodies of adjacent spinal segments. These bone screws are then connected to each other by rigid metal rods in order to stabilize the spine and enable progressive bony fusion. Such bone screw-rod constructs have gained prominence due to their superior biomechanical stability relative to alternate fixation techniques, such as wiring, etc., as well as the benefits provided by three column fixation of the spine. Such systems have been made more versatile in recent years with the advent of polyaxial screw head technology, which allows more complex construct placement and screw connections. While current screw-rod systems are ideal for fixating motion segments in the spine in neutral position, certain situations call for the application of compressive or distractive forces in order to improve spinal balance and to aid in spinal fusion.

Current screw based spinal fixation systems use smooth, cylindrical metal or ceramic rods to connect screws that are anchored in bony portions of each vertebral level, such as the pedicle, lateral mass, lamina, and/or vertebral body. One example of a currently known screw based spinal fixation system is illustrated inFIG. 1. As shown inFIG. 1, a bone screw10connected to a rod12. Rod12is cylindrical, and has a smooth outer surface. Bone screw10has a screw head14, which can have a variable angle head, as shown, or it could be a fixed angle screw. Bone screw10includes a threaded shaft16attached to the screw head14. Bone screw10also includes a set screw18that is attached to the screw head14. Bone screw10can be connected to the rod12by attaching the bone screw to the desired bony spinal portion, sliding the rod12onto the bone screw, and then tightening the set screw18to secure the bone screw10at a desired location on the rod12.

After placing this instrumentation, spine surgeons typically apply compressive forces manually between adjacent screws in order to increase lordosis for improved sagittal balance, or to compress upon an interbody graft in order to improve fusion. Alternatively, surgeons may wish to apply distractive forces between adjacent screws in order to improve access to the disc space for discectomy or interbody graft placement, or to affect deformity correction. Due to the smooth, cylindrical rod design, current spinal fixation systems do not provide or allow for the maintenance of compressive or distractive forces. Instead, one surgeon must provide manual compression between two screws while a second surgeon attempts to tighten the rod in place at each fixation point. This technique is both cumbersome and technically challenging.

SUMMARY

The present technology relates to compression-distraction spinal fixation systems that include screw-rod constructs that include a ratcheting mechanism. Tools for manipulation of the screw-rod constructs are also provided.

According to an embodiment, a compression-distraction spinal fixation system is provided that includes at least one bone screw and a toothed rod. The bone screw can include a threaded shaft, a screw head, a set screw, and a pawl. The toothed rod can have a plurality of ratchet teeth that receive the pawl of the bone screw, whereby the bone screw is releasably coupled to and selectively moveable unidirectionally along the toothed rod.

According to another embodiment, a compression tool for use with a spinal fixation system is provided. The compression tool may include first and second handle portions pivotably coupled to one another about a common fulcrum, and first and second extension portions connected, respectively, to the first and second handle portions. The first and second extension portions may include distal tips configured to engage a portion of adjacent bone screws of the spinal fixation system to allow manual manipulation of the bone screws unidirectionally toward one another along a toothed rod of the spinal fixation system.

According to another embodiment, a distraction tool for use with a spinal fixation system is provided. The distraction tool may include first and second handle portions pivotably coupled to one another at a pivot point, and first and second extension portions connected, respectively, to the first and second handle portions. The first and second extension portions may include distal tips configured to engage a portion of adjacent bone screws of the spinal fixation system to allow manual manipulation of the bone screws unidirectionally away from one another along a toothed rod of the spinal fixation system.

According to another embodiment, a spinal fixation kit is provided. The kit may include a bone screw, a toothed rod, and a compression and/or distraction tool. The bone screw may include a pawl. The toothed rod has a plurality of ratchet teeth. The bone screw is configured to be releasably coupled to and selectively moveable along the toothed rod. The pawl of the bone screw is configured to engage the ratchet teeth of the toothed rod to allow unidirectional movement of the bone screw along the toothed rod. The compression tool may include distal tips configured to engage a portion of the bone screw and move the same unidirectionally along the toothed rod. The compression tool may include handle portions pivotably coupled to one another about a common fulcrum, and respective extension portions connected to the handle portions. The distractor tool may include distal tips configured to engage a portion of the bone screw and move the same unidirectionally along the toothed rod. The distraction tool may include handle portions pivotably coupled to one another at a pivot point, and respective extension portions connected to the handle portions.

Further features and advantages, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings.

DETAILED DESCRIPTION

The present technology relates to compression-distraction spinal fixation systems and kits that include screw-rod constructs and tools for manipulation of such screw-rod constructs. More particularly, the present technology provides a rod and screws that incorporate a ratchet and pawl mechanism for imposition of compression and distraction forces on the spinal column. Preferably, compression-distraction spinal fixation systems described herein can allow a single surgeon the ability to apply compressive or distractive forces as desired between adjacent spinal levels in a seamless and efficient manner. By employing the unique ratcheting mechanism provided in compression-distraction spinal fixation systems of the present technology, which in at least some examples can integrate into existing bone-screw rod technology, regional forces can be maintained segmentally or across the entirety of a given spinal construct, avoiding the cumbersome technique of compression/distraction that is inherent to traditional screw-rod systems. Combining improvements in maintenance of regional forces with ease of application and use, the compression-distraction spinal fixation systems of the present, technology can add to a spine surgeon's armamentarium in the treatment of complex spinal disease.

Compression-distraction spinal fixation systems of the present technology are more particularly described in the following examples with reference to the accompanying drawings, and are intended as illustrative only. Referring to the drawings, like numbers indicate like parts throughout the views. Compression-distraction spinal fixation systems of the present technology include a toothed rod and at least one bone screw of the present technology. In some examples, compression-distraction spinal fixation systems of the present technology include a toothed rod, at least one bone screw of the present technology, and at least one conventional bone screw. In other examples, compression-distraction spinal fixation systems of the present technology include a toothed rod, a first bone screw of the present technology, and a second bone screw of the present technology.

As used in the description herein, and throughout the claims that follow, the meaning of “ratcheting the bone screw along the length of the toothed rod” means that the position of the bone screw is changed with respect to its original position along the length of the toothed rod due to movement of the bone screw, movement of the rod, or movement of both the bone screw and the rod. As used in the description herein, and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

The rods of compression-distraction spinal fixation systems of the present technology include ratchet teeth, which are preferably evenly spaced along a portion of the length of the rod, preferably along the entire length or substantially the entire length of the rod. Placing evenly spaced ratchet teeth along the length of the rod can allow the rod to be cut and contoured as desired in the operating room. In some examples, precut and precontoured rods can be provided, such as for example, for short segment constructs typically spanning 2, 3, and 4 vertebral levels. The ratchet teeth can cover at least a portion of the outer surface, or circumference, of the rod, including but not limited to, the entire circumference of the rod, half the circumference of the rod, one third of the circumference of the rod, one quarter of the circumference of the rod, or any other suitable portion of the circumference of the rod. The ratchet teeth can be formed as depressions in a toothed rod, or as protrusions that extend from the toothed rod. Toothed rods of the present technology can be made from any suitable material, including but not limited to a biocompatible metal, such as titanium, titanium alloy, stainless steel or cobalt chromium; a biocompatible polymer, such as PEEK; a composite material such as carbon fiber; or a biocompatible metal coated with another biocompatible metal or biocompatible polymer. In at least some examples, the inner diameter of the toothed rods, which is the diameter of the rod not including the height of the ratchet teeth, can be the same as the diameters that are currently used with known smooth rods, which can provide the same mechanical strength as currently known rods.

Bone screws of the present technology can also be made from any suitable material, including but not limited to a biocompatible metal, such as titanium, titanium alloy, stainless steel or cobalt chrome; a biocompatible polymer, such as PEEK; a composite material such as carbon fiber; or a combination of these. Bone screws of the present technology include a pawl that can engage the teeth on the toothed rod to provide a ratcheting mechanism. The pawl engages at least one ratchet tooth at a location on the toothed rod, and can allow unidirectional ratcheting of the bone screw on the rod to maintain either a compressive or distractive force as desired. In some examples, pawls are flexible, while in others they are rigid. Some of the examples described herein include reversible pawls, meaning that the pawl can be adjusted to allow ratcheting in either direction along the length of the toothed rod, depending on the orientation of the pawl. In other examples, however, pawls that are not reversible, and that provide ratcheting in only a single direction, are also provided. Bone screws of the present technology can also include a shaft, such as a threaded shaft, that can be used to attach the bone screw to a desired bony portion of the spine. Bone screws of the present technology can further include a screw head, and a set screw.

FIGS. 2 through 6illustrate one example of a screw-rod construct100of the present technology that includes a toothed rod102having ratchet teeth104, a first bone screw106of the present technology and a second bone screw108of the present technology. In an alternative example, either bone screw106or bone screw108could be replaced with a conventional bone screw, such as bone screw10illustrated inFIG. 1. In the illustrated example ofFIG. 2, each bone screw includes a threaded shaft110, a screw head112, a set screw114, and a pawl116. The set screw114of each bone screw includes a retaining ring118, which retains the pawl116on the set screw114. The pawl116is preferably flexible, and includes a bend120and a blade122.

When the toothed rod102is slidably connected to the first bone screw106and the second bone screw108, the blade122of each pawl116of each bone screw106,108engages at least one tooth of the ratchet teeth104on toothed rod102. The first bone screw106can be ratcheted along the toothed rod102in the direction indicated by arrow A, but the engagement of the blade122of the first bone screw106with the ratchet teeth104of the toothed rod102can prevent movement of the first bone screw106in the opposite direction. Likewise, the second bone screw108can be ratcheted along the toothed rod102in the direction indicated by arrow B, but the engagement of the blade122of the second bone screw108with the ratchet teeth104of the toothed rod102can prevent movement of the second bone screw108in the opposite direction.

FIG. 3shows an exploded view of the first bone screw106, which further illustrates the attachment of the pawl116to the set screw114. As illustrated, the retaining ring118is a circular, flexible piece of material with a cut portion124to allow expansion of the diameter of the retaining ring118. The set screw114has a circular boss128that includes a retaining ring groove130, and a threaded portion132. The pawl116has a circular bore126that communicates with the circular boss128on the set screw114. The pawl116slides over the circular boss128and the retaining ring118is captured in a retaining ring groove130to attach the pawl116to the set screw114without restraining the rotation of the pawl116.

In use, first bone screw106can be inserted into a bony portion of a patient's spine, such as the posterior arch, pedicle, or vertebral body of a vertebra. Then, toothed rod102can be placed into a recess134in screw head112. The set screw114can be threaded into the screw head112until there is significant engagement of the pawl116with the ratchet teeth104of the toothed rod102. Distracting or compressing forces, depending on the orientation of the pawl116, can then be used to slide the first bone screw106, and therefore the vertebra to which it is attached, relative to toothed rod102.

FIG. 4illustrates that rotation of the pawl116in the direction of the arrow C can reverse the direction of travel of first bone screw106by changing to the orientation shown inFIG. 5. The pawl116is rotatable from a first position, as shown inFIG. 4, to a second position, as shown inFIG. 5, that is about 180° from the first position. The pawl116can include a locking boss136, which can prevent inadvertent rotation of the pawl116. The locking boss136can allow rotation of the pawl116when the set screw114is loosened an amount sufficient for the locking boss136to clear the screw head112. After the first bone screw106has been moved along toothed rod102to a desired location, the set screw114can be tightened to rigidly secure the screw head112to the toothed rod102.FIG. 6shows a sectioned view of the first bone screw106with an enlargement to further illustrate the elements of the first bone screw106as described above.

FIGS. 7 and 8illustrate a second example of a screw-rod construct of the present technology. Screw-rod construct200as shown inFIGS. 7 and 8includes a toothed rod202having ratchet teeth204, and a bone screw206. The bone screw206has a threaded shaft208, a screw head210, a set screw212, and a pawl214. The pawl214can be rotatably mounted to a side of the screw head210by a fastener216, such as a pin. The pawl214includes a bend218and a blade220. The blade220of the pawl214engages the ratchet teeth204of the toothed rod202. Rotation of the pawl214from a first position, as shown inFIG. 7, to a second position, as shown inFIG. 8, that is about 180° from the first position, can reverse the direction of travel of the bone screw206along the length of the toothed rod202.

FIGS. 9 through 11illustrate a third example of a screw-rod construct of the present technology, withFIG. 11showing an exploded view. Screw-rod construct300as shown inFIGS. 9 through 11includes a toothed rod302having ratchet teeth304, and a bone screw306. The bone screw306has a threaded shaft308, a screw head310having a pawl receiving groove318, a set screw312, and a pawl314. The pawl314is a clip-on pawl that can be connected to the screw head310by being received by the pawl receiving groove318of the screw head310. Pawl314can include a cut316that allows expansion of the diameter of the pawl314to facilitate installation of the pawl314onto the pawl receiving groove318of the screw head310. The pawl314can include a spring portion320and a blade322. The blade322engages the ratchet teeth304of the toothed rod302. The spring portion320can provide flexibility to the pawl314to allow the blade322to slide over the ratchet teeth304of the toothed rod302when the bone screw306is ratcheted along the length of the toothed rod302. Rotation of the pawl314from a first position, as shown inFIG. 9, to a second position, as shown inFIG. 10, that is about 180° from the first position, can reverse the direction of travel of the bone screw306along the length of the toothed rod302.

FIGS. 12 and 13illustrate a fourth example of a screw-rod construct of the present technology. Screw-rod construct400as shown includes a toothed rod402having ratchet teeth404, and a bone screw406. The bone screw406has a threaded shaft408, a screw head410, a set screw412, and a sliding pawl414. The sliding pawl414can be slidably attached to the screw head410with a fastener416, such as a pin. The pawl414can also include a fastener groove420, and the fastener416can extend through the fastener groove420to slidably attach the pawl414to the screw head410. The screw head410can include a pawl receiving groove418on a side of the screw head410, and sliding pawl414can be slidably received in the pawl receiving groove418. The pawl414can further include a first blade422at one first end, and a second blade422(not shown) at the opposite end. The first blade422can engage the ratchet teeth404of the toothed rod402when the slidable pawl414is in a first position, as shown inFIG. 12, allowing the bone screw406to ratchet along the length of the toothed rod402in one direction. The second blade422, which can be a mirror image of the first blade422, can engage the ratchet teeth404of the toothed rod402when the slidable pawl414is in a second position, as shown inFIG. 13, allowing the bone screw406to ratchet along the length of the toothed rod402in the opposite direction.

FIGS. 14 through 16illustrate a fifth example of a screw-rod construct of the present technology, withFIG. 15being an exploded view andFIG. 16being a cross-sectional view. Screw-rod construct500includes a toothed rod502having ratchet teeth504, and a bone screw506. The bone screw506has a threaded shaft508, a screw head510, a set screw512, and a pawl514. The pawl514can be a raised boss on the bottom surface of the set screw512that engages the ratchet teeth504of the toothed rod502. A leaf spring516can be positioned under the rod receiving groove518of the screw head510, and can provide an upward force on the toothed rod502to ensure engagement of the ratchet teeth504and the pawl514. When horizontal force is exerted in the direction of arrow D, the leaf spring516can deflect out of the way and allow ratcheting of the bone screw506along the length of the toothed rod502.

FIGS. 17 and 18illustrate a sixth example of a screw-rod construct of the present technology, withFIG. 18being an exploded view. Screw-rod construct600includes a toothed rod602having ratchet teeth604, and a bone screw606. The bone screw606has a threaded shaft608, a screw head610, a set screw612, and a pawl614. The pawl614is attached to a frame616that has a recess618. The recess618attaches to the screw head610, and can be lowered over the screw head610into alignment with the toothed rod602so that the pawl614engages the ratchet teeth604of the toothed rod602. The pawl614can be attached to the frame616with a fastener620, such as a pin, that extends through a bore624in the frame616and can be rigidly attached to the pawl614due to press fit of the fastener620into a pawl hole626in the pawl614. As illustrated, the fastener620can have a hexagonal head622. A spring628can be attached to the frame616by a spring fastener630, and can exert an inward force on the pawl614to maintain engagement of the pawl614with the ratchet teeth604. To disengage the pawl614from the ratchet teeth604, an operator can rotate the hexagonal head622of the fastener620clockwise.

FIGS. 19 through 24illustrate examples of ratchet teeth that can be formed on a toothed rod700of the present technology. The ratchet teeth can be formed on the toothed rod700in any suitable manner, such as by being cut, pressed, rolled, forged, molded or otherwise formed. In one example, toothed rod700having ratchet teeth can be fabricated in a molding operation such as MIM (Metal Injection Molding). In other examples, ratchet teeth can be formed by waterjet cutting, EDM (Electrical Discharge Machining), etching, or ECM (Electrochemical Machining).FIG. 19shows toothed rod700having triangular teeth702.FIG. 20shows toothed rod700having saw teeth704.FIG. 21shows toothed rod700having triangular teeth706in a staggered pattern, wherein the ratchet teeth706are separated by an offset R.FIG. 22shows toothed rod700having squared teeth708.FIG. 23shows toothed rod700having ratchet teeth formed by a helical piece of material710that is wrapped around and secured to the toothed rod700. The helical piece of material710can be secured to the toothed rod in any suitable manner, including, for example, being sintered, welded, soldered, or bonded.FIG. 24shows toothed rod700having ratchet teeth formed by helical threads712. Helical threads712can be formed in any suitable manner, including being cut into toothed rod700, or being formed by a thread rolling operation which could increase the fatigue life of toothed rod700.

FIGS. 25 and 26illustrate toothed rod700having triangular teeth714formed straight, meaning on a linear path, across an outer surface of the toothed rod700.FIGS. 27 and 28illustrate toothed rod700having triangular teeth716formed radially, meaning on a non-linear, arcuate path, across an outer surface of the toothed rod700.

FIGS. 29 and 30illustrate a seventh example of a screw-rod construct of the present technology, withFIG. 30being sectioned view. Screw-rod construct800includes a toothed rod802having ratchet teeth804, and a bone screw806. The bone screw806has a threaded shaft808, a screw head810, a set screw812, and a pawl814. The pawl814is a toggle pawl located in a side of the screw head810. The toggle pawl814is housed within a recess816in the side of the screw head810. The toggle pawl814is attached to the screw head810, preferably at the center of the toggle pawl814, by a fastener818, such as a pin. The toggle pawl814can rotate about the fastener, from a first position, as shown inFIG. 30, to a second position that has an orientation opposite that of the first position, thus allowing the bone screw806to be ratcheted along the length of the toothed rod802in a first or second direction, respectively. The toggle pawl814can be spring-loaded, or can have sufficient friction to allow it to be rotated from the first position to the second position by manual force exerted by an operator.

Previously described are pawls which flex or rotate, however it should be understood that a pawl may also translate linearly away from toothed rod and return to contact with toothed rod under the action of a spring such as a helical spring, a leaf spring, a machined spring, or any elastic resilient material.FIGS. 31 through 33illustrate one example of a screw-rod construct of the present technology having such a linearly translating pawl, withFIG. 32being an exploded view, andFIG. 33being a sectioned view. Screw-rod construct900includes a toothed rod902having ratchet teeth904, and a bone screw906. The bone screw906has a threaded shaft908, a screw head910, a set screw912, and a pawl914. The pawl914is attached to a side of the screw head910, and can be located in a screw head bore922that has a keyway924. The pawl914is a plunger pawl, having teeth916, a blind hole926, a helical cut918, and an anti-rotation boss920. Helical cut918allows plunger pawl914to compress like a helical spring. In lieu of helical cut918, plunger pawl914could incorporate a wire wound helical spring, a leaf spring or other resilient material. The anti-rotation boss920of the plunger pawl914can align with the keyway924of the screw head910to maintain alignment of plunger pawl914with the ratchet teeth904of the toothed rod902. As the bone screw906is ratcheted along the length of the toothed rod902, the helical spring918can compress and extend to so that plunger pawl914maintains contact with toothed rod902and allows motion in one direction only.

Screw-rod constructs including at least one bone screw of the present technology and at least one rod of the present technology can allow compressive or distractive forces to be applied sequentially across each level of a given construct as desired.

In at least one example, the application of compressive or distractive forces can be accomplished by first attaching at least one bone screw of the present technology to at least one desired bony portion of a patient's spine. In one example a first bone screw can be attached to a first bony portion of a patient's spine, and a second bone screw can be attached to a second bony portion of a patient's spine. At least one of the bone screws, or both, can have a pawl. The toothed rod of the present technology can be optionally shaped by an operator, such as a surgeon, and can be attached to each bone screw. In some examples, the toothed rod can be attached to each bone screw by placing the toothed rod in the screw head of the first bone screw and in the screw head of the second bone screw, and then placing a first set screw on the screw head of the first screw and a second set screw on the screw head of the second screw to maintain the toothed rod in the screw head of each bone screw. The pawl of the at least one bone screw having a pawl can be oriented to engage the ratchet teeth of the toothed rod. In some examples, the pawl can be oriented to engage the ratchet teeth of the toothed rod in a first position or a second position, for the application of either distractive or compressive forces as desired. The bone screw having a pawl, or at least one of the bone screws having a pawl, can then be ratcheted along the length of the toothed rod to apply the desired amount of distractive or compressive force. Once the desired amount of distractive or compressive force is achieved, each set screw can be tightened to maintain each bone screw in a fixed position relative to the toothed rod. The distractive or compressive force can be maintained temporarily or permanently.

The distractive or compressive force can be used to alter the distance between bony portions of a patient's spine. For example, the distance between spinal vertebrae of a patient can be altered by attaching a first bone screw to a first spinal vertebra and attaching a second bone screw to a second spinal vertebra, wherein at least the first bone screw has a pawl. A toothed rod can then be attached to the first and second bone screws, and the pawl of the first bone screw can be oriented to engage the ratchet teeth of the toothed rod. The method can then include altering the distance between the first vertebra and the second vertebra. The distance between the first vertebra and the second vertebra can be altered by ratcheting the first bone screw a desired amount along the length of the toothed rod to apply an amount of distractive or compressive force sufficient to obtain the desired altered distance between the first vertebra and the second vertebra. The altered distance can then be maintained, temporarily or permanently, by the pawl engaging the ratchet teeth of the toothed rod.

FIGS. 34 and 35illustrate a ninth example of a screw-rod construct1000according to an embodiment of the present technology. As shown, the screw-rod construct1000includes a toothed rod1002having ratchet teeth1004, and first and second bone screws1006,1008, respectively. In the illustrated example ofFIG. 34, each bone screw1006,1008includes a threaded shaft1010, a screw head1012, a set screw1014, and a pawl1016. A retaining ring1018is arranged to be received on each set screw1014to retain the pawl1016on the set screw1014. The pawl1016may be flexible, and includes a bend1020and a blade1022. The portion of the pawl1014disposed about the set screw1012is shown in the depicted embodiment as being substantially perpendicular to the blade1022.

When the toothed rod1002is coupled to the first bone screw1006and the second bone screw1008, the blade1022of each pawl1016of each bone screw1006,1008engages at least one tooth of the ratchet teeth1004on toothed rod1002. As depicted inFIGS. 34 and 35, the first bone screw1006can be ratcheted along the toothed rod1002in a first direction (to the right inFIGS. 34 and 35), but the engagement of the blade1022of the first bone screw1006with the ratchet teeth1004of the toothed rod1002can prevent movement of the first bone screw1006in the opposite direction. Likewise, the second bone screw1008can be ratcheted along the toothed rod1002in a second direction (to the left inFIG. 34), but the engagement of the blade1022of the second bone screw1008with the ratchet teeth1004of the toothed rod1002can prevent movement of the second bone screw1008in the opposite direction. Alternatively, by rotating the pawls1016of each bone screw1006,1008180°, the allowed directions of movement of each bone screw1006,1008can be reversed.

FIG. 35shows a sectional view of the first bone screw1006with an enlargement to further illustrate the elements of the first bone screw1006as described above. As illustrated, the retaining ring1018is a circular, flexible piece of material with a cut portion to allow expansion of the diameter of the retaining ring1018. The set screw1014has a circular boss that includes a retaining ring groove1030, and a threaded portion1032. The pawl1016has a circular bore1026that communicates with the circular boss on the set screw1014. The pawl1016slides over the circular boss and the retaining ring1018is captured in the retaining ring groove1030to attach the pawl1016to the set screw1014without restraining the rotation of the pawl1016. The pawl1016is rotatable from a first position, as shown inFIGS. 34 and 35, to a second position (not shown) that is about 180° from the first position. The pawl1016can include a locking boss or extension1036, which can prevent inadvertent rotation of the pawl1016. The locking boss1036can allow rotation of the pawl1016when the set screw1014is loosened an amount sufficient for the locking boss1036to clear the screw head1012. After the first bone screw1006has been moved along toothed rod1002to a desired location, the set screw1014can be tightened to rigidly secure the screw head1012to the toothed rod1002.

FIGS. 36,36a, and36billustrate a tenth example of a screw-rod construct1100according to an embodiment of the present technology. The screw-rod construct1100includes a toothed rod1102having ratchet teeth1104, and a bone screw1106. In the illustrated example ofFIG. 36, the bone screw1106includes a threaded shaft1108, a screw head1110, a set screw1112, and a pawl1114. The set screw1112of the bone screw1106includes a retaining ring1118, which retains the pawl1114on the set screw1112. The screw head1110includes a chamfered top portion1116and the pawl1114also includes an angled annular portion1115about the periphery thereof (seeFIG. 36b) for engaging the chamfered top portion1116of the screw head1110. The pawl1114includes a blade1122for engaging the ratchet teeth1104on the toothed rod1102. The pawl1114is rotatable from a first position, as shown inFIG. 36, to a second position, as shown inFIG. 36a, that is about 180° from the first position. The pawl1114can include a detent1120on a side of the pawl opposite the blade1122, which can be received in a rod receiving recess1134to prevent inadvertent rotation of the pawl1114. The detent1120can allow rotation of the pawl1114when the set screw1112is loosened an amount sufficient for the detents to clear the screw head1110. After the bone screw1106has been moved along toothed rod1102to a desired location, the set screw1112can be tightened to rigidly secure the screw head1110to the toothed rod1102. As shown inFIG. 37, a slightly modified pawl1114′ includes a plurality of detents1120′ spaced from one another on a side of the pawl1114′ opposite the blade1122′. The detents1120′ can be received in a rod receiving recess1134′ of screw head1110′ to prevent inadvertent rotation of the pawl1114′ about set screw1112′.

FIG. 38illustrates an exploded perspective view of an eleventh example of a screw-rod construct1200according to an embodiment of the present technology.FIG. 39illustrates a sectional assembled view of the screw-rod construct1200illustrated inFIG. 38. The screw-rod construct1200includes a toothed rod1202having ratchet teeth1204, and a bone screw1206including a threaded shaft1208, a screw head1210, a set screw1212, and a pawl1214. The set screw1212of the bone screw1206includes a retaining ring1218, which retains the pawl1214on the set screw1212. The pawl1214may be flexible, and includes a bend1220and a blade1222.

When the toothed rod1202is received in rod receiving recess1234of the bone screw1206, the blade1222of the pawl1214extends underneath the set screw1212and engages at least one tooth of the ratchet teeth1204on toothed rod1202. The bone screw1206can be ratcheted along the toothed rod1202in a first direction (to the left inFIG. 34), but the engagement of the blade1222of the bone screw1206with the ratchet teeth1204of the toothed rod1202can prevent movement of the bone screw1206in the opposite direction. Further tightening of the set screw1212rigidly engages the blade1222of the pawl1214into the ratchet teeth1204such that further movement of the bone screw1206in any direction is prevented and a rigid connection is established.

FIG. 40illustrates a twelfth example of a screw-rod construct1300according to an embodiment of the present technology. The screw-rod construct1300includes a toothed rod1302having ratchet teeth1304, and a bone screw1306of the present technology including a threaded shaft1308, a screw head1310, a set screw1312, and a pawl1314. The set screw1312includes a retaining ring1318, which retains the pawl1314on the set screw1312. The pawl1314may be flexible, and includes a bend1320and a blade1322. As shown in the embodiment depicted inFIG. 40, an interior angle between the portion of the pawl1314disposed about the set screw1312and the blade1322may be less than 90 degrees.

FIG. 41illustrates a perspective view of a thirteenth example of a screw-rod construct1400according to an embodiment of the present technology.FIG. 42illustrates an exploded perspective view of the screw-rod construct1400illustrated inFIG. 41.FIG. 43illustrates a sectional view of the screw-rod construct1400illustrated inFIG. 41. The screw-rod construct1400includes a toothed rod1402having ratchet teeth1404, and a bone screw1406of the present technology including a threaded shaft1408, a screw head1410, a set screw1412, and a pawl1414. The set screw1412includes a retaining ring1418, which retains the pawl1414on the set screw1412. The pawl1414may be flexible, and includes a bend1420and a blade1422configured to engage the ratchet teeth1404. As shown in the embodiment depicted inFIGS. 41-43, the portion of the pawl1414disposed about the set screw1412is substantially perpendicular to the blade1422. An edge1423of the blade1422, which edge is arranged to be received in and engage the ratchet teeth1404, may be substantially linear as shown inFIGS. 41-43. In fact, the tooth-engaging edge of the pawl blade of any of the embodiments described herein may be substantially linear when, for example, the toothed rod is cut as shown inFIGS. 25-26. Alternatively, the tooth-engaging edge of the pawl blade of any of the embodiments described herein may be substantially curvilinear when, for example, the toothed rod is cut as shown inFIGS. 27-28. For example, as shown inFIG. 44, a tooth-engaging edge1423′ of blade1422′ of pawl1414′ is shown as being curvilinear in order to conform to a non-linear, arcuate path cut across an outer surface of a toothed rod.

FIGS. 45 through 48illustrate a fourteenth example of a screw-rod construct1500according to an embodiment of the present technology. The screw-rod construct1500is substantially similar to the screw-rod construct1400described above and shown inFIGS. 41-43, but also includes a torque-off, or frangible, set screw configuration.FIG. 45illustrates a perspective view of the screw-rod construct1500during assembly.FIG. 46illustrates a perspective view of the screw-rod construct1500when assembled.FIG. 47illustrates a perspective view of the screw-rod construct1500after assembly and removal of the pawl1514.FIG. 48illustrates an enlarged and exploded detail view of the torque-off set screw1512of the screw-rod construct1500. Referring toFIGS. 45-47, the screw-rod construct1500includes a toothed rod1502having ratchet teeth1504, and a bone screw1506. The bone screw1506includes a threaded shaft1508, a screw head1510, a set screw1512, and a pawl1514. The set screw1512, as shown inFIG. 48, includes a threaded portion1517and an extended, frangible hex portion1519having two retaining grooves1521a,1521bspaced axially from one another along the outer periphery thereof. The retaining grooves1521a,1521bare configured to receive respective first and second retaining rings1518a,1518b, which axially retain the pawl1514on the hex portion1519of the set screw1512while allowing rotation of the pawl1514. The pawl1514may be flexible, and includes a bend1520and a blade1522configured to engage the ratchet teeth1504. The portion of the pawl1514disposed about the set screw1512is shown as being substantially perpendicular to the blade1522although other angles are possible as shown and disclosed in other embodiments provided herein. The frangible hex portion1519of the set screw1512may be configured to be broken off from the lower threaded portion of the set screw1512, for example, upon tightening of the set screw1512with a predetermined torque. The predetermined torque may be set according to an amount sufficient to rigidly secure the bone screw1506to the toothed rod1502. Upon such breaking of the frangible hex portion1519from the remainder of the set screw1512, the hex portion1519and pawl1514may be moved away in direction Y.

The following description of how the compression-distraction spinal fixation system may be used is applicable to any of the foregoing example screw-rod constructs. In use, each bone screw is secured to respective bony portions of a patient's spine. The toothed rod may be shaped by the surgeon and then placed in the screw head of each bone screw in standard fashion. The set screw is then positioned for threaded attachment to the screw head with the pawl oriented in either a compressive (0°) or distractive (180°) direction. The unidirectional pawl is then received in the ratchet teeth of the toothed rod. By manually compressing or distracting adjacent bone screws, the pawl ratchets along the toothed rod, resting within the ratchet teeth and maintaining the desired compressive or distractive force. Once the desired force and position are reached, the set screw is then tightened into the threaded portion of the screw head. In the case of the embodiment depicted inFIGS. 38 and 39, for example, the independently rotatable, ratcheting pawl may gradually retract into a hollow center of the set screw, causing rigid fixation with the underlying rod. In order to bring the pawl into contact with the ratchet teeth of the toothed rod while allowing ratcheted movement of the bone screws along the toothed rod, the set screw may be loosely (“provisionally”) threaded to the screw head or may be, for example, received in an initial non-threaded portion (not shown) of the screw head spaced away from the toothed rod sufficiently to allow the pawl to ratchet. The non-threaded portion may include a lip (not shown) on the top of the screw head so that once the set screw is manually pushed across the lip, it is held within the non-threaded portion (between the lip and the threaded portion) during ratcheting.

FIG. 49illustrates a perspective view of a compressor tool1600according to an embodiment. Although compressor tool1600is shown engaging and manipulating two adjacent bone screws106,108as shown in the embodiment depicted inFIGS. 2-6, compressor tool1600may be used with any of the above-described ratcheting screw-rod constructs. The compressor tool1600may include first and second handle portions1602,1604which may be ergonomically formed for gripping by a surgeon. In the manner of a pair of pliers, the first and second handle portions1602,1604may be pivotably coupled to one another at a common fulcrum or pivot pin1606. The first handle portion1602may be connected to a first angled extension portion1610and the second handle portion1604may be connected to a second angled extension portion1608. The first and second angled extension portions1610,1608may extend at an angle relative to a plane defined by the first and second handle portions1602,1604such as, for example, in a direction substantially parallel to an axis of the pivot pin1606as shown inFIG. 49.FIG. 51illustrates a perspective view of a modified compressor tool1700according to another embodiment of in which first and second angled extension portions1710,1708may extend at about a 45° angle relative to a plane defined by first and second handle portions1702,1704such as, for example, in a direction substantially 45° relative to an axis of a pivot pin1706.

FIG. 50illustrates a detailed sectional view of the compressor tool1600shown inFIG. 49engaging the two adjacent bone screws106,108of a screw-rod construct. The screw-rod construct shown includes toothed rod102with ratchet teeth104, and first and second bone screws106,108attached thereto. InFIG. 50, as in the illustrated example ofFIG. 2, each bone screw106,108includes a threaded shaft110, a screw head112, a set screw114, and a pawl116. The first and second angled extension portions1610,1608may include respective distal ball tips1614,1612which are configured to be received in set screws114for manipulation of the bone screws106,108along the toothed rod102. By using the compressor tool1600(or1700), a surgeon can ratchet adjacent bone screws106,108(and, hence, respective vertebrae) toward each other along the toothed rod102until a desired position and/or force is reached, at which point the surgeon can tighten the set screws114to rigidly secure the bone screws106,108to the toothed rod102. Likewise, the modified compressor tool1700shown inFIG. 51can include tips1712,1714and can be similarly utilized.

FIG. 52illustrates a perspective view of a compressor tool1800according to yet another embodiment, which is configured to engage and compress adjacent bone screws in a substantially linear fashion, and which may be utilized with any of the above-described ratcheting screw-rod constructs. The compressor tool1800may include first and second handle portions1802,1804which may be ergonomically formed for gripping by a surgeon. In the manner of a pair of pliers, the first and second handle portions1802,1804may be pivotably coupled to one another at a common fulcrum or pivot pin1806. The first handle portion1802may be connected to a first extension portion1807and the second handle portion1804may be connected to a second extension portion1809. The first and second extension portions1807,1809may each be pivotably coupled at an end thereof to respective further first and second extension portions1824,1822by pivot pins1810,1808, respectively. The further first and second extension portions1824,1822, are additionally coupled to one another via a secondary scissor mechanism1815. Secondary scissor mechanism1815includes first and second crossing levers1816,1818pivotably coupled to each other at a central fulcrum1820. A first end of first crossing lever1816is pivotably coupled to the second extension portion1822by a pivot pin1812at a position proximate the pivot pin1808. A first end of second crossing lever1818is pivotably coupled to the first extension portion1824by a pivot pin1814at a position proximate the pivot pin1810. A second end of the first crossing lever1816includes a journal1828slidably and pivotably received within a longitudinally extending slot1832in the further first extension portion1824. Likewise, a second end of the second crossing lever1818includes a journal1826slidably and pivotably received within a longitudinally extending slot1830in the further second extension portion1822. The further first and second extension portions1824,1822also include tip extensions1836,1834, respectively, which in turn include respective ball tips1840,1838configured to engage the set screws of adjacent bone screws to be manipulated. As noted above, the foregoing structure of compressor tool1800allows a surgeon gripping the device to squeeze handles1802,1804and thereby move ball tips1840,1838substantially linearly toward (or away from) one another while maintaining tip extensions1836,1834substantially parallel to one another. The parallel compressor tool1800may fit down two parallel tubes for minimally invasive spine (MIS) techniques.

FIGS. 53 through 55depict example embodiments of some distractor (retractor) tools according to several embodiments of the invention, each of which are configured to engage and separate adjacent bone screws, and which may be utilized with any of the above-described ratcheting screw-rod constructs.FIG. 53, for example, illustrates a perspective view of a distractor tool1900configured to engage and manipulate two adjacent bone screws (not shown inFIG. 53) according to an embodiment. The distractor tool1900may include first and second handle portions1902,1904which may be ergonomically formed for gripping by a surgeon. The first and second handle portions1902,1904may be pivotably coupled to one another a pivot point1906. Unlike the compressor tools described above, however, the handle portions1902,1904do not cross over one another at such pivot point1906. Rather, here the first handle portion1902may be connected to a first angled extension portion1908and the second handle portion1904may be connected to a second angled extension portion1910. The first and second angled extension portions1908,1910may extend at an angle relative to a plane defined by the first and second handle portions1902,1904such as, for example, in a direction substantially parallel to an axis of the pivot point1906, although other angles (not shown) are also possible. The first and second angled extension portions1908,1910may include respective ball tips1912,1914which are configured to be received in set screws for manipulation of adjacent bone screws along a toothed rod. By using the distractor tool1900, a surgeon can ratchet adjacent bone screws (and, hence, respective vertebrae) away from each other along the toothed rod until a desired position and/or force is reached, at which point the surgeon can tighten the set screws to rigidly secure the bone screws to the toothed rod.

FIG. 54illustrates a perspective view of a distractor tool2000according to another embodiment. The distractor tool2000is shown engaging and manipulating two adjacent bone screws2106,2108moveably coupled to a toothed rod2102having ratchet teeth2104.FIG. 55illustrates a sectional view of the distractor tool2000shown inFIG. 54engaging the two adjacent bone screws2106,2108. The distractor tool2000may include first and second handle portions2002,2004which may be ergonomically formed for gripping by a surgeon. The first and second handle portions2002,2004may be pivotably coupled to one another a pivot point2006. Unlike the compressor tools described above, however, the handle portions2002,2004do not cross over one another at such pivot point2006. Rather, here the first handle portion2002may be connected to a first extension portion2008and the second handle portion2004may be connected to a second extension portion2010. The first and second extension portions2008,2010are shown extending in the same plane as the handle portions2002,2004, but may extend at an angle relative to a plane defined by the first and second handle portions2002,2004such as, for example, in a direction substantially parallel to an axis of the pivot point2006, although other angles (not shown) are also possible. The first and second extension portions2008,2010may include respective distal tips each of which may include an open U-shaped recess2012,2014configured to receive the toothed rod2102and contact a side of the respective screw heads2112of the bone screws2106,2108for ratcheted manipulation of the bone screws2106,2108away from one another along the toothed rod2102. The extension portions2008,2010may also include multiple protrusions2016,2018, respectively, for positively engaging the sides of the bone screws2106,2108. That is, by using the distractor tool2000, a surgeon can ratchet the adjacent bone screws2106,2108(and, hence, respective vertebrae) away from each other along the toothed rod2102until a desired position and/or force is reached, at which point the surgeon can tighten the set screws to rigidly secure the bone screws2106,2108to the toothed rod2102. A compressor tool (not shown) with similarly structured distal tips may also be provided which is constructed to engage outer sides of the adjacent bone screws2106,2108and ratchet the same toward each other along the toothed rod2102.

EXAMPLE

A screw-rod construct of the present technology was made in accordance with the example illustrated inFIGS. 2-6. The toothed rod had triangular ratchet teeth formed by cutting grooves having a 90° angle along the length of the toothed rod. The grooves were cut about 0.75 mm apart, and were cut radially in an arc that was about 60°. The toothed rod had an inner diameter of about 5.5 mm, and was made from Grade 23 Titanium alloy (Ti6Al4V-ELI). The pawl was also made of Grade 23 Titanium alloy (Ti6Al4V-ELI), and was about 0.016 inches (0.4 mm) thick. The blade of the pawl was about 5 mm wide.

From the foregoing, it will be appreciated that although specific examples have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit or scope of this disclosure. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to particularly point out and distinctly claim the claimed subject matter.