Dual rod cross connectors and inserter tools

An implantable spinal cross connector is provided for connecting one or more spinal fixation devices, and more preferably for connecting two spinal fixation rods that are implanted within a patient's spinal system. In general, an exemplary cross connector in accordance with the present invention includes an elongate body with at least one rod-receiving recess formed therein, and a locking mechanism that is adapted to couple to the elongate body and that is effective to lock a spinal fixation rod within the rod-receiving recess(es). The present invention also provides an inserter tool to facilitate implanting a spinal implant or device, such as a spinal cross connector.

FIELD OF THE INVENTION

The present invention relates to spinal fixation devices, and in particular to a cross connector for connecting spinal fixation elements, such as spinal fixation rods, implanted in a patient's spinal system, and to tools for implanting the same.

BACKGROUND OF THE INVENTION

Spinal fixation devices are used in orthopedic surgery to align and/or fix a desired relationship between adjacent vertebral bodies. Such devices typically include a spinal fixation element, such as a relatively rigid fixation rod, that is coupled to adjacent vertebrae by attaching the element to various anchoring devices, such as hooks, bolts, wires, or screws. Alternatively, two rods can be disposed on the lateral or anterior surface of the vertebral body in a substantially parallel relationship. The fixation rods can have a predetermined contour that has been designed according to the properties of the target implantation site, and once installed, the rods hold the vertebrae in a desired spatial relationship, either until desired healing or spinal fusion has taken place, or for some longer period of time.

Spinal cross connectors are often used in conjunction with spinal fixation devices to provide additional stability to the devices. For example, it has been found that when a pair of spinal rods are fastened in parallel on either side of the spinous process, the assembly can be significantly strengthened by using a cross connector to bridge the pair of spinal rods. The connectors are typically in the form of a rod having a clamp formed on each end thereof for mating with a spinal rod.

While current spinal cross connectors have proven effective, difficulties have been encountered in mounting the cross connectors, and maintaining them in a desired position and orientation with respect to the spinal rod, or other spinal fixation device to which they are attached. In particular, the clamp assemblies often consist of several parts which make surgical application tedious, and which can also increase the manufacturing costs. Since the cross connector is often applied as the last step in a lengthy surgical procedure, ease of application is paramount. Fixation of the cross connector to spinal rods can also be difficult where the rods are not parallel to one another, or they are diverging/converging with respect to one another.

Accordingly, there presently exists a need for an improved spinal cross connector that can be easily installed and that securely mates to and connects spinal fixation devices.

SUMMARY OF THE INVENTION

The present invention provides an implantable spinal cross connector for connecting spinal fixation devices, and more preferably for connecting two spinal fixation rods to one another. In one embodiment, an exemplary implantable spinal cross connector is provided having an elongate body with a central portion and opposed first and second ends. At least one rod-receiving recess is formed adjacent to at least one of the first and second opposed ends of the elongate body. The device also includes at least one rod-engaging member and a locking mechanism that is adapted to apply a force to the rod-engaging member(s) to cause it to move linearly to lock a spinal fixation rod within the at least one rod-receiving recess.

The configuration of the locking mechanism can vary, but in one exemplary embodiment, the central portion of the elongate body includes a central bore formed therein that is adapted to receive the locking mechanism. The locking mechanism can include a proximal portion that is adapted to engage a proximal portion of the central bore in the elongate body, and a distal shaft extending distally from the proximal portion. Preferably, the distal shaft is adapted to extend into the central bore to apply a force to the rod-engaging member(s) disposed within the elongate body to cause at least a portion of the rod-engaging member(s) to extend into the at least one rod-receiving recess to lock a spinal fixation rod therein. The distal shaft can optionally taper in a distal direction, and the rod-engaging member(s) can optionally include an internal surface that faces the central bore and that is substantially concave to seat the tapered shaft of the locking mechanism. In a further embodiment, the central bore can include threads formed therein for mating with corresponding threads formed on the proximal portion of the locking mechanism. The threads in the central bore and the threads on the proximal portion of the locking mechanism can optionally be sized to allow minor motion of the locking mechanism within the central bore.

The rod-engaging member(s) can also have a variety of configurations, but in an exemplary embodiment they are adapted to at least partially extend into the at least one rod-receiving recess to lock a spinal fixation element therein. More preferably, the rod-engaging member(s) is disposed within a rod-engaging member receiving cavity which extends between a central bore that is formed in the elongate body for receiving the locking mechanism, and the rod-receiving recess(es) in the elongate body. In an exemplary embodiment, the rod-engaging member(s) is slidably movable within the at least one receiving cavity. By way of non-limiting example, a pin member extending through the elongate body and into a groove formed within the rod-engaging member can be provided for slidably retaining each rod-engaging member within the receiving cavity. Each pin member is preferably effective to allow slidable movement of the rod-engaging members between a first retracted position in which the rod-engaging members are substantially positioned toward the central bore, and a second extended position in which the rod-engaging members are substantially positioned toward the rod-receiving recess.

In another exemplary embodiment of the present invention, an implantable spinal cross connector is provided and it includes an elongate body having a central portion and first and second rod-receiving recesses formed substantially adjacent to opposed terminal ends of the connector member. The elongate body can also include a first rod-engaging member extending between the central opening and the first rod-receiving recess, and a second rod-engaging member extending between the central opening and the second rod-receiving recess. The first and second rod-engaging members are preferably disposed within first and second cavities formed within the elongate body and extending between the central opening and the first and second rod-receiving recesses. The device also preferably includes a single locking mechanism that is matable to the central portion of the connector member and that is effective to lock first and second spinal fixation elements within the first and second rod-receiving recesses formed in the connector member. A central opening can be provided in the elongate body for receiving the locking mechanism.

In use, the rod-engaging members can be slidable between a first retracted position in which the rod-engaging members are substantially disposed within the first and second cavities in the elongate body, and a second extended position in which at least a portion of the rod-engaging members extend into the rod-receiving recesses formed within the elongate body. The locking mechanism is preferably effective to apply a force to the first and second rod-engaging members when the locking mechanism is disposed within the central opening to lock first and second spinal fixation elements within the first and second rod-receiving recesses.

In yet another embodiment of the present invention, an implantable spinal cross connector is provided having an elongate body with first and second rod-receiving recesses formed substantially adjacent to opposed first and second terminal ends therein, a first rod-engaging member that is adapted to extend into the first rod-receiving recess, a second rod-engaging member that is adapted to extend into the second rod-receiving recess. A locking mechanism is receivable within the elongate body and it is effective to apply a force to the first and second rod-engaging members to cause the first and second rod-engaging members to move linearly to lock a spinal fixation element within the first and second rod-receiving recesses.

The present invention also provides a method for connecting first and second spinal fixation rods that includes the steps of coupling first and second spinal fixation rods to one or more vertebrae in a patient's spinal column, positioning a spinal cross connector relative to the first and second spinal fixation rods such that the first spinal fixation rod is seated within a first rod-receiving recess in the spinal cross connector and the second spinal fixation rod is seated within a second rod-receiving recess in the spinal cross connector, and applying a single locking mechanism to the spinal cross connector to cause first and second rod-engaging members to move linearly to lock each of the first and second spinal fixation rods within the first and second rod-receiving recesses.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a spinal cross connector for connecting one or more spinal fixation elements, and more preferably for connecting two spinal fixation rods, that are implanted within a patient's spinal system. In general, an exemplary cross connector in accordance with the present invention includes an elongate body with at least one rod-receiving recess formed therein, and a locking mechanism that is adapted to couple to the elongate body and that is effective to lock a spinal fixation rod within the rod-receiving recess(es).

A person skilled in the art will appreciate that while the cross connector10is described herein as being adapted to engage a spinal fixation element, and in particular a spinal fixation rod, that a cross connector of the present invention can be configured to engage a variety of spinal fixation elements, such as anchors, cables, fixation plates, etc. Moreover, the cross connector can include only one rod-receiving recess for engaging a spinal fixation element, and the opposed terminal end of the cross connector can be adapted for other uses. For example, the opposed terminal end of the cross connector can be configured to be fixedly attached to a vertebra or vertebral body replacement device or graft. The cross connectors of the present invention can also include any combination of features described and/or illustrated herein or known in the art, and the cross connector is not limited to the illustrated embodiments.

FIGS. 1A-1Dillustrate one exemplary embodiment of a cross connector10in accordance with the present invention. As shown, the cross connector10has a generally elongate body12. The configuration, shape, and size of the elongate body12can vary depending on the intended use, but preferably the elongate body12has a shape, size, and configuration that allows it to connect to and span two spinal fixation elements, such as spinal rods, that are implanted within a patient's spinal column. In an exemplary embodiment, the elongate body12includes a central portion14with opposed first and second terminal ends16,18. The length Lbof the elongate body12extending between the opposed terminal ends14,16will vary depending on the intended use. For example, the elongate body12can have a length Lbthat is in the range of about 10 mm to 30 mm for use in an anterior surgical approach. In an exemplary embodiment, the cross connector10is provided as part of a kit that includes multiple cross connectors having varying lengths Lb. The length Lbof each cross connector10in the kit preferably differs in increments of about 1 mm.

As indicated above, the cross connector10is preferably adapted to connect to and span two spinal fixation elements, such as spinal rods, implanted within a patient's spinal column. Accordingly, the cross connector10can include one or more rod-receiving recesses formed therein.FIGS. 1A-1Dillustrate first and second rod-receiving recesses20,22formed therein and adapted to seat a spinal fixation rod. The location of the recesses20,22can vary, but preferably the first and second rod-receiving recesses20,22are formed substantially adjacent to the first and second terminals ends16,18of the elongate body12. As a result, when the cross connector10is connected to two spinal rods, the central portion14will extend between the rods. The rod-receiving recesses20,22are also preferably formed in a bottom surface12bof the elongate body12such that they are on an opposite side of the body12from a central opening24that is formed in the top surface12aof the body12and which will be discussed in more detail below.

The rod-receiving recesses20,22can vary in shape and size depending on the type of spinal fixation element being engaged. As previously noted, the cross connector10is preferably adapted to connect to two spinal fixation rods. Accordingly, each recess20,22can have a shape that is configured to accommodate a substantially cylindrical spinal rod. In other words, each recess20,22can be substantially concave such that it defines a partially cylindrical cavity. The size of the recesses20,22can also vary depending on the size of the spinal fixation element. In an exemplary embodiment, each recess20,22has a depth drthat is greater than a radius of the spinal fixation rod disposed therein. The depth drcan also be greater than a diameter of the spinal fixation rod, or is can be less than or substantially equal to a diameter of the spinal fixation rod. The recesses20,22do, however, preferably seat a substantial portion of the spinal fixation rod to allow the rod to be firmly locked therein, as will be discussed in more detail below.

The cross connector10can also include one or more rod-engaging members, hereinafter referred to as shoes, that are configured to engage a spinal fixation element disposed within the recesses20,22. As shown inFIGS. 1A-1D, the cross connector10includes first and second shoes28,30that are slidably disposed within the elongate body12adjacent to the first and second rod-receiving recesses20,22. The shoes28,30can have a variety of configurations and they can be mated to or disposed within the elongate body12using a variety of techniques, but they are preferably effective to move linearly in response to a force applied thereto by the locking mechanism26to lock a spinal fixation rod within each rod-receiving recess20,22. In an exemplary embodiment, the elongate body12includes first and second receiving cavities32,34formed therein for slidably seating the shoes28,30. The first and second cavities32,34preferably extend between the central opening24formed in the central portion14of the elongate body12, and the first and second rod-receiving recesses20,22in the body12. The cavities32,34are also preferably spaced a distance apart from the bottom surface12bof the elongate body12to allow the shoes28,30to be retained within the body12.

Each cavity32,34can vary in shape and size, but they should allow slidable movement of the shoes20,22therein. More preferably, each cavity32,34has a shape that is substantially similar to a shape of the shoes20,22. In the illustrated embodiment, each cavity32,34has a substantially elongate rectangular shape that is configured to match the contour of each shoe28,30, as will be discussed below. The cavities32,34can also extend at a downward angle from the central bore24toward the rod-receiving recesses20,22such that each shoe28,30, when moved from within the cavity32,34toward the rod-receiving recess20,22, extends in a downward direction. Such a configuration facilitates engagement of the rods disposed within the rod-receiving recesses20,22.

The shoes28,30are shown in more detail inFIGS. 1B and 1C, and as shown each shoe28,30can have a generally rectangular or square cross-sectional shape taken along a plane that extends between an internal surface28a,30aand an external surface28b,30bthereof. The internal surface28a,30afaces the central opening24when the shoe28,30is disposed within the cavity32,34, and the opposed external surface28b,30bfaces the rod-receiving recess20,22. While the cross-section of the shoes28,30can be substantially square or rectangular, the internal and external surfaces28a,30a,38b,30bcan vary in shape. In particular, the internal surface28a,30aof each shoe28,30can have a shape that conforms to the shape of the locking mechanism26, which will be discussed in more detail below. In an exemplary embodiment, the internal surface28a,30aof each shoe28,30includes a concave recess formed therein, as shown. The concave shape of the internal surface28a,30ais effective to seat a portion of the locking mechanism26. As is further shown inFIG. 1C, the external surface28b,30bof each shoe28,30can have a substantially planar configuration, but each surface28b,30bcan extend at an angle such that a width w1at a top portion of each shoe28,30is less than a width w2at a bottom portion of each shoe28,30. In other words, the width of each shoe28,30decreases from the top to the bottom. This configuration allows only a mid-portion or the bottom portion of each shoe28,30to come into contact with a spinal fixation rod disposed within the rod-receiving recess20,22in the elongate body12when the shoes28,30are in a locked configuration as a result of the locking mechanism26. The external surface28b,30bof each shoe28,30can also be optimizing to facilitate engagement of a spinal fixation rod. By way of non-limiting example, the surfaces28b,30b, or at least a portion thereof, can include gripping features, such as ridges, grooves, a surface coating, etc., formed or disposed thereon to engage the rod.

In use, the first and second shoes28,30are preferably slidably movable between a first retracted position (not shown) in which the shoes28,30are at least partially or fully disposed within the first and second cavities32,34in the elongate body12, and a second extended position, as shown inFIGS. 1A and 1B, in which at least a portion of the shoes28,30extend into the recesses20,22formed within the elongate body12. In the first retracted position, at least a portion of the shoes28,30can extend into the central opening24in the elongate body12. The shoes28,30can be moved into the second extended position by inserting the locking mechanism26into the opening24such that the locking mechanism26applies a force to the first and second movable shoes28,30to cause the shoes28,30to move linearly and lock first and second spinal fixation rods within the first and second rod-receiving recesses20,22.

In order to prevent the shoes28,30from falling out of the cavities during movement, the device10can include a mechanism to slidably retain each shoe28,30within each cavity32,34. While various techniques can be used, in one exemplary embodiment, as shown, the cross connector10includes first and second pin members40,42that extend through the bottom surface12bof the body12and into a groove44,46formed within a bottom surface of each shoe28,30. The groove44,46preferably extends between the internal and external faces28a,30a,38b,30bof the shoes28,30to allow the shoes28,30to slide between the retracted and extended positions. The pin members40,42can be retained within the elongate body12using various techniques, but preferably the pin members40,42are fixedly mated to the elongate body12using a press fit or using other techniques known in the art.

Other embodiments of techniques for retaining the shoes within the connector body are shown inFIGS. 4A-5.FIG. 4Aillustrates a connector200that is similar to connector10and that includes connector body212with shoes228and230disposed therein. In this embodiment, each shoe228,230includes a tab that extends toward the central opening224of the connector body212, and that includes a protrusion formed thereon that is adapted to extend into a bore or groove formed in the connector body212. The tabs on the shoes228,230are preferably formed on opposite sides of the connector body212, thusFIG. 4Aonly illustrates tab229formed on shoe228. The protrusion229aon tab229is shown in detail inFIG. 4B. In use, the protrusion229aon the tab229extends into a bore213formed in a sidewall of the connector body212. The tab229is preferably deflectable to allow the shoe228to be snapped into the connector body212. Once the protrusion229aon the tab229is in engagement with the bore213, the protrusion229ais free to move within the bore213, thus allowing the shoe228to slidably move relative to the connector body212.

In the embodiment shown inFIG. 5, the shoes328,330are retained within the body312of the connector300by a hook-type engagement. In particular, each shoe328,330preferably includes a hook member that extends toward the central opening324in the body312. The hook members on the shoes328,330are preferably formed on opposite sides of the connector body312, thusFIG. 5only illustrates hook member329formed on shoe328. Thus, referring to shoe328, the hook member329is configured to engage a pin313that protrudes into the central opening324formed in the connector body312such that the hook member329extends around the pin313. In use, the length of the hook member329allows the shoe328to slidably move relative to the connector body312while the pin313prevents the hook member329, and thus the shoe328, from falling out of the connector body312. A person skilled in the art will appreciate that a variety of other techniques can be used to retain the shoes within the connector body.

As noted above, the device10further includes a locking mechanism26that is adapted to apply a force to the shoes28,30to linearly move the shoes28,30from the first retracted position to the second extended position. The locking mechanism26can have a variety of configurations and it can be receivable within the elongate body12at a variety of locations. In one exemplary embodiment, as shown inFIGS. 1A-1D, the elongate body12includes a central opening24formed in a top surface12athereof for receiving the locking mechanism26. The central opening24can extend completely through the elongate body12, but it preferably terminates at a location that is a distance apart from the bottom surface12bof the body12. The locking mechanism26, which is receivable within the opening24, can include a proximal portion26athat is adapted to mate to a proximal portion of the central opening24, and a distal portion26bthat is adapted to apply a force to the shoes28,30to move the shoes28,30into the second extended position. While various techniques can be used to mate the locking mechanism26to the central opening24, in the illustrated embodiment the proximal portion26aof the locking mechanism26includes threads26dformed thereon for mating with corresponding threads25formed within at least a proximal portion of the central opening24. The distal portion26bof the locking mechanism26can also vary in shape and size, but in one exemplary embodiment the distal portion26bof the locking mechanism26is in the form of a shaft or pin-type member. At least a portion of the shaft26bpreferably tapers toward the distal end to facilitate the application of force against the shoes28,30. In particular, as previously indicated, the internal surface28a,30aof each shoe28,30can have a concave recess formed therein for seating the tapered shaft26b. Thus, when the locking mechanism26is threaded into the central opening24, the tapered shaft26bcontacts the concave internal surface28a,30aof each shoe28,30to force the shoes28,30into the second extended position. The shaft26bcan also have a variety of other shapes such as, for example, a spherical shape or cone shape. A person skilled in the art will appreciate that the shape of the distal portion26bof the locking mechanism26can vary depending on the shape of the shoes28,30.

In use, the cross connector10can be coupled to one or more, and preferably two, spinal fixation elements, such as spinal rods, that are implanted within a patient's spine, as shown inFIG. 1D. This can be achieved by positioning the cross connector10such that a spinal rod70,80is seated within each rod-receiving recess20,22. In this position, the shoes28,30are in the first retracted position, as the locking mechanism26is not yet inserted into the central opening24, or it is only loosely threaded in the central opening24. The spinal rods70,80may also force the shoes28,30into the retracted position. Once the cross connector10is properly disposed over the spinal rods70,80, the locking mechanism26can then be threaded into the central opening24. As the locking mechanism26is rotated, the distal shaft26bwill contact the internal surface28a,30aof the shoes28,30to push the shoes28,30toward the rod-receiving recesses20,22, thereby pushing the shoes28,30against the spinal rods70,80disposed therein. The locking mechanism26is threaded until the shoes28,30lock the rods70,80into the recesses20,22, as shown inFIG. 1D. The threads26don the locking mechanism26and the threads25in the central opening24can optionally be designed such that, when the locking mechanism26is fully threaded into the central opening24, the shoes28,30are in a locked position. The threads26d,25can also be designed to allow some minor movement between the locking mechanism26and the elongate body12to allow for any imbalance between the position of the shoes28,30. Imbalances can occur as a result of the position of the spinal rods implanted in the patient's spine, e.g., when the rods are not parallel to one another. In an exemplary embodiment, a minor gap can be provided between the threads25in the central opening such that the locking mechanism26can slightly move side-to-side when disposed therein. A person skilled in the art will appreciate that a variety of other techniques can be used to facilitate the equal distribution of force by the locking mechanism26onto the shoes28,30such that the shoes28,30.

The locking mechanism26can have a variety of other configurations, and a variety of other techniques can be used to move the shoes28,30between the first retracted position and the second extended position, and to lock the shoes in a fixed position to engage spinal fixation elements disposed within the recesses20,22. By way of non-limiting example,FIG. 2illustrates another embodiment of a locking mechanism26′ that includes two separate components: a ball-type member26b′ and a threaded member26a′. The ball-type member26b′ sits within the central opening24′ in the elongate body12′, and the threaded member26a′ can be threaded into the opening24′ to push the ball-type member26b′ downward, thereby moving the shoes28′,30′ into the extended position.

The present invention also provides an inserter tool100that can be used to position a spinal implant or device with respect to one or more spinal fixation elements, such as two spinal rods. While the tool100is described for use with cross connector10, the tool can be used with a variety of spinal implants and devices. Referring toFIGS. 3A-3B, one exemplary embodiment of an inserter tool100is shown in accordance with the present invention. In general, the tool100includes an elongate shaft102having a proximal handle end102aand a distal end102b. The elongate shaft102is preferably hollow to allow other tools, such as a driver for rotating the locking mechanism26, to be inserted therethrough. The proximal handle end102acan have a variety of configurations, shapes, and sizes, but it is preferably adapted to allow a user to easily grasp the tool100. As shown inFIG. 3A, the handle102aincludes ridges103formed thereon to facilitate grasping of the device100. The distal end102bof the elongate shaft102is configured to grasp the cross connector10to position the cross connector10in relation to one or more spinal fixation elements implanted in a patient's spine.

The distal end102bof the elongate shaft102of the inserter tool100is shown in more detail inFIG. 3B, and as shown the distal end102bincludes first and second arms106,108which are effective to engage the central portion14of the cross connector10. The arms106,108preferably define a cavity104therebetween that has a shape that generally corresponds to the contour of the central portion14of the cross connector10. In particular, the cavity104can be substantially square or rectangular in shape to receive the central portion14. The distal end102bof the inserter tool100can also have a substantially square or rectangular shape to define the shape of the cavity104as well as the position of the arms106,108relative to one another.

Each arm106,108of the inserter tool100can also be flexible, or include a flexible portion, to create a friction fit between the arms106,108and the central portion14of the cross connector, thereby allowing the cross connector10to be removably mated to the inserter tool100. As shown inFIG. 3B, arm106has a flexible tab106aformed at a substantial mid-portion thereof. While only partially shown, arm108can also include a flexible tab108aformed thereon. The flexible tabs106a,108acan have any shape and size, but they preferably define a distance da(FIG. 3A) therebetween that is equal to or slightly less than a width wc(FIG. 1C) of the central portion14of the cross connector10.

The arms106,108of the inserter tool100can also include one or more features formed thereon for aligning the tool100with the cross connector10. By way of non-limiting example, an inner surface of each arm106,108can include a protrusion (not shown) formed thereon for fitting within a corresponding detent or groove formed on the central portion14of the cross connector. In an exemplary embodiment, the protrusions are formed on diagonally opposed ends of the opposed arms106,108, and the grooves15a,15bare formed on diagonally opposed sides of the central portion14of the cross connector10, as shown inFIG. 1A. This allows the inserter tool100to be properly aligned with the cross connector10, and in particular such a feature is effective to align the lumen extending through the inserter tool100with the central opening24formed in the cross connector10.

The inserter tool100can also optionally include one or more cut-out portions or windows formed therein to facilitate viewing of the central opening24in the cross connector10when the cross connector10is coupled to the tool100. By way of non-limiting example,FIG. 3Billustrates window110formed in the shaft102of the inserter tool100just proximal to the distal end102b. While not shown, a second window can be formed opposed to the first window110.

The present invention also provides a method for coupling to spinal fixation elements, such as spinal rods, implanted within a patient's spinal column. In general, as previously described with respect toFIG. 1C, after the spinal fixation rods70,80are implanted using techniques know in the art, the rods70,80can be rigidly coupled to one another by positioning the cross connector10over the rods70,80such that the rods70,80sit within the recesses20,22in the cross connector10. The inserter tool100can be used to facilitate such positioning of the cross connector10. In particular, the cross connector10can be positioned between and engaged by the opposed arms106,108of the inserter tool100. The tool100can then be manipulated to position the cross connector10over the rods70,80. A driver mechanism (not shown) can then be inserted through the hollow elongate shaft102of the inserter tool100to rotate the locking mechanism26, which is preferably loosely pre-threaded into the central opening24, thereby moving the shoes28,30to lock the spinal rods70,80relative to the cross connector10.