Spinal implants, spinal rod approximators for seating a stabilizing rod in a rod-receiving portion of a spinal implant, and methods for using the same are provided. In one embodiment, a spinal rod approximator is provided including an elongate member having a grasping member formed on a distal end thereof, and a rod pusher member slidably mated to or mounted on the elongate member. The grasping member is effective to grasp a portion of a spinal implant, and the pusher member is effective to grasp and engage a stabilizing rod and push the rod into a rod-receiving portion of the spinal implant being grasped by the grasping member.

FIELD OF THE INVENTION

The present invention relates to spinal fixation systems, and in particular to a spinal rod approximator, a spinal implant, and methods for using 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. 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 instrument holds 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 fixation devices can be anchored to specific portions of the vertebra. Since each vertebra varies in shape and size, a variety of anchoring devices have been developed to facilitate engagement of a particular portion of the bone. Pedicle screw assemblies, for example, have a shape and size that is configured to engage pedicle bone. Such screws typically include a threaded shank that is adapted to be threaded into a vertebra, and a head portion having a rod-receiving element, usually in the form of a U-shaped slot formed in the head. A set-screw, plug, or similar type of fastening mechanism, is used to lock the fixation rod into the rod-receiving portion of the pedicle screw. In use, the shank portion of each screw is then threaded into a vertebra, and once properly positioned, a fixation rod is seated through the rod-receiving portion of each screw and the rod is locked in place by tightening a cap or similar type of locking mechanism to securely interconnect each screw and the fixation rod.

While current spinal fixation systems have proven effective, difficulties have been encountered in mounting rods into the rod-receiving portion of various fixation devices. In particular, it can be difficult to align and seat the rod into the rod receiving portion of adjacent fixation devices due to the positioning and rigidity of the vertebra into which the fixation device is mounted. Thus, the use of a spinal rod approximator, also referred to as a spinal rod reducer, is often required in order to grasp the head of the fixation device, and reduce the rod into the rod-receiving portion of the fixation device.

While several rod approximators are known in the art, some tend to be difficult and very time-consuming to use. Accordingly, there is a need for an improved rod approximator, implants for use with rod approximators, and methods for seating a spinal rod in a rod-receiving portion of one or more spinal implants.

SUMMARY OF THE INVENTION

The present invention provides medical devices and methods for seating a stabilizing rod in a rod-receiving portion of a spinal implant, and spinal implants for use with a rod approximator. In one embodiment, a rod approximator device is provided including an elongate member having a proximal end and a distal end defining an axis extending therebetween, and a grasping member extending from the distal end of the elongate member in a direction substantially transverse to the axis. The grasping member is effective to engage a spinal implant, and can optionally define opposed arms adapted to slide into and engage corresponding slots formed in a spinal implant. The device further includes a rod pusher member slidably mated to the elongate member and movable along the axis between a first position in which the rod pusher member is positioned a distance apart from the grasping member and is effective to grasp a stabilizing rod, and a second position in which the rod pusher member is positioned adjacent to the grasping member and is effective to position the grasped stabilizing rod in a rod-receiving portion of a spinal implant being engaged by the grasping member.

The rod approximator device of the present invention can also include an actuating member that can be coupled to the proximal end of the elongate member and the rod pusher member. The actuating member is effective to move the rod pusher member with respect to the grasping member. The actuating member can have a variety of configurations and in one embodiment it comprises opposed first and second members. A force applied to bring the first and second members toward one another is effective to move the rod pusher member from the first position to the second position. The actuating member can extend in a direction substantially transverse to the axis of the elongate member, and can optionally extend in a direction opposed to the grasping member. In an exemplary embodiment, the actuating member is in the form of a handle or grip and it comprises a first, stationary member mated to the proximal end of the shaft, and a second, opposed movable member linked to the proximal end of the elongate member. A force applied to bring the second, movable member toward the first, stationary member is effective to move the rod-engaging member from the first position to the second position. The actuating member can optionally include a ratchet mechanism effective to move the rod pusher member from the first position to the second position in predetermined increments. A release mechanism can be coupled to the ratchet mechanism to release the ratchet mechanism to enable the rod pusher member to return to the first position. The device can also optionally include a locking mechanism effective to lock the actuating member in one of the first or second positions, or optionally in an intermediate position between the first and second positions.

The rod pusher member of the approximator device can also have a variety of configurations. In one embodiment, the rod pusher member can include a shaft having proximal and distal ends, and can be slidably mounted on the elongate member along the axis. The rod pusher member can also include a rod-engaging member mated to the distal end of the shaft and preferably offset a distance apart from the shaft in a direction substantially transverse to the axis. The rod-engaging member can have a substantially semi-cylindrical shape and can include at least one rod-engaging recess formed on a distal facing portion thereof. In an exemplary embodiment, the grasping member defines opposed arms adapted to slide into and engage corresponding slots formed in a spinal implant, and at least one rod-engaging recess is formed in the rod-engaging member and is axially aligned with the opposed arms of the grasping member.

In another embodiment of the present invention, a system for seating a stabilizing rod in a rod-receiving portion of a spinal implant is provided. The system includes a spinal implant having a distal, bone engaging portion, and a proximal head including a base portion mated to the distal, bone engaging portion. A rod-receiving recess is formed in the proximal head for seating a stabilizing rod. The system further includes a rod reduction device having an elongate member with a distal grasping member formed thereon and offset from a longitudinal axis of the elongate member. The grasping member is adapted to engage and grasp the base portion of the head of the spinal implant. The rod reduction device also includes a rod pusher member slidably mounted on the elongate member and effective to grasp a stabilizing rod and, upon actuating, to push the rod into the rod-receiving recess formed in the spinal implant.

In an exemplary embodiment, the distal grasping member is substantially U-shaped, and the base portion of the head of the implant includes opposed slots formed therein. Preferably, the grasping member is adapted to slide into the slots on the implant to grip the implant. The opposed slots formed in the base portion of the head of the spinal implant can have a variety of configurations. In one embodiment, the slots each include an upper and lower shoulder. The lower shoulder is preferably substantially planar, and the upper shoulder is preferably substantially planar and includes opposed ends that are curved in a direction away from the lower shoulder. In other aspects of the invention, the head of the spinal implant can have a substantially hollow, cylindrical shape and can include opposed cut-out portions that form the rod-receiving recess for seating a stabilizing rod. The opposed slots formed in the base portion of the head of the spinal implant are preferably positioned distally adjacent to the opposed cut-out portions formed in the head of the spinal implant.

In yet another embodiment, the rod pusher member comprises an elongate shaft having proximal and distal ends that extend along the longitudinal axis, and a rod-engaging member mated to the distal end of the shaft and offset a distance apart from the axis of the shaft. An actuating member can be mated to the elongate member and the rod pusher member, and is effective to selectively move the rod pusher member between a first position in which the rod-engaging member is offset a distance apart from the grasping member, and a second position in which the rod-engaging member is positioned adjacent to the grasping member and is effective to position a stabilizing rod in the rod-receiving recess formed in the head of the spinal implant that is being engaged by the grasping member. In a preferred embodiment, the actuating member extends in a direction substantially transverse to the axis, and more preferably, the actuating member extends in a direction opposed to the grasping member.

In yet another embodiment of the present invention, a spinal implant is provided having a substantially hollow, cylindrical shaped head member including an open, proximal end and a closed, distal end. A bone-engaging member extends from the closed, distal end of the head member and is effective to engage bone. The head member includes a rod-receiving recess formed from opposed cut-out portions extending from the open, proximal end and terminating proximal to the closed, distal end. The head further includes opposed slots formed in a base of the head proximal to the closed, distal end and distal to the cut-out portions. The opposed slots are effective to receive opposed arms of a rod reduction device to enable the rod reduction device to engage the head of the spinal implant and to engage a stabilizing rod to push the rod into the rod-receiving recess formed in the head of the spinal implant.

The opposed slots formed in the base portion of the head of the spinal implant can each include an upper and lower shoulder. The lower shoulder is preferably substantially planar, and the upper shoulder is preferably substantially planar and includes opposed ends that are curved in a direction away from the lower shoulder.

Methods for reducing a stabilizing rod into a rod-receiving portion of a spinal implant are also provided.

DETAILED DESCRIPTION OF THE INVENTION

In general, the present invention provides spinal fixation systems, and in particular a spinal implant, a spinal rod approximator for seating a stabilizing rod in a rod-receiving portion of a spinal implant, and methods for using the same. The spinal implants and spinal rod approximators of the present invention are particularly effective in that they are easy to use, they do not require significant force to operate, and they are efficient, thereby reducing the time and expense necessary to perform spinal surgery.

FIG. 1illustrates one embodiment of a spinal rod approximator10that is effective to engage and seat a stabilizing rod in a rod-receiving portion of a spinal implant. As shown, the tool10generally includes an elongate member12having a grasping member14formed on a distal end thereof, and a rod pusher member16slidably mated to or mounted on the elongate member12. The grasping member14is effective to grasp a portion of a spinal implant, and the pusher member16is effective to grasp and engage a stabilizing rod and push the rod into a rod-receiving portion of the spinal implant being grasped by the grasping member14.

A person having ordinary skill in the art will appreciate that while the tools and devices illustrated herein are described for use with spinal surgery, the tools can be adapted for use with a variety of medical procedures.

The elongate member12of the rod approximator10is shown in more detail inFIG. 2. The elongate member12can have a variety of shapes and sizes, but is preferably a generally elongate, solid rigid member having a proximal end12aand a distal end12b. The cross-sectional shape and size of the elongate member12, as well as the length leof the elongate member12, can vary depending on the intended use. The elongate member12should, however, be substantially rigid to prevent bending thereof, and should have a length lesufficient to enable the distal end12bof the elongate member12to be placed adjacent to a surgical site while the proximal end12aof the elongate member12remains outside a patient's body. By varying the size and shape, the elongate member12can also be adapted for use in minimally invasive procedures. By way of non-limiting example, the elongate member12can be configured to be disposed through an access tube or similar device.

The distal end12bof the elongate member12includes a mating element14that is effective to grasp a spinal implant. The mating element14can have a variety of configurations, but is preferably a U-shaped grasping member14that is effective to grasp and engage a spinal implant. The grasping member14can be mated to the distal end12aof the elongate member12using a variety of mating techniques, or it can be integrally formed thereon. Preferably, the grasping member14is integrally formed with the elongate member12, and extends in a direction substantially transverse to an axis A of the elongate member12. The grasping member14can also be positioned at a distance offset from the axis A of the elongate member12to facilitate use of the device. The offset position is particularly advantageous in that the implant can be grasped by the device while avoiding contact with adjacent bone structures. The offset position can be formed by providing a bend15in the distal end12bof the elongate member12, as shown inFIGS. 2-3B. While the angle α of the bent portion with respect to the axis A of the elongate member12can vary, the angle α is preferably in the range of about 15° to 60°, and more preferably is about 45° with respect to the axis A.

Still referring toFIGS. 3A and 3B, the grasping member14is adapted to mate with corresponding mating elements formed on the head portion of a spinal implant, as will be discussed in more detail with respect toFIGS. 11A-11C. While the grasping member14can have a variety of configurations,FIG. 3Aillustrates one embodiment of a grasping member14having opposed arms22a,22bthat extend outward from a semi-cylindrical wall31in a direction substantially perpendicular to the axis A of the elongate member12. The semi-cylindrical wall contoured to the head of an implant being engaged, and it is adapted to fit around and seat the head of the implant. Further, the arms22a,22bare configured to fit within corresponding recesses or slots formed in the head of the implant.

Each arm22a,22can have virtually any shape and size, and the arms can include several different mating features to facilitate grasping of the implant. As shown, the opposed arms22a,22bhave a generally elongate, rectangular shape and include opposed proximal and distal surfaces24a,24b,26a,26b, and opposed inner24c,26cand outer24d,26dside surfaces, respectively. The proximal and distal surfaces24a,24b,26a,26b, and opposed inner24c,26cand outer24d,26dside surfaces are each preferably substantially planar. The distal most end28a,28bof each arm22a,22bcan be rounded to facilitate insertion of the arms22a,22binto the corresponding slots formed in the head of the implant, and to prevent any potential damage to tissue surrounding the treatment site. Each arm of the grasping member can also optionally include a curved and/or narrowed distal tip28a,28b. Preferably, the proximal surface24a,26aof each arm22a,22bis ramped such that the distal tip28a,28bof each arm has a width less than a width of the proximal portion of the arm22a,22b. The narrowed tip allows the arms to be inserted into corresponding slots formed in a spinal implant at a variety of angles, thereby facilitating use of the device.

FIG. 3Billustrates another embodiment of a grasping member14′ that includes an inner recess32formed thereon that is adapted to receive a corresponding ridge formed around a base portion of the spinal implant. As shown, the recess32is formed around the distal most portion of the inner surface of the grasping member14′, and extends around the inside of both arms22a′,22b′ and optionally can extend around the semi-cylindrical wall31′. The inner wall34is preferably slightly concave so as to be contoured to the rounded shape of the head of the implant. In use, an annular ridge formed around the head of the spinal implant slides into the recess32and the inner wall34fits securely around the base portion of the implant to allow the grasping member14′ to engage the implant.

FIGS. 3C-3Dillustrate yet another embodiment of a grasping member90having a pin and bore connection. As shown, the distal end93of the elongate member92includes a pin94disposed thereon that extends in a direction transverse to the axis a. The pin94preferably extends toward the proximal end91of the elongate member92at an angle α′ with respect to the axis a, and has a shape and size adapted to fit within a corresponding bore96formed in the head98of the implant. The pin94and the bore96can have virtually any shape and size, but the pin94should be configured to securely grasp the head98of the implant when inserted in the bore96. The angle α′ of the pin94facilitates a secure engagement of the head98as the angle α′ prevents the pin94from falling out of the bore96when a proximally-directed force is applied to the elongate member92.

A person having ordinary skill in the art will appreciate that the grasping members14,14′,90shown inFIGS. 3A-3Care not intended to limit the scope of the invention. The grasping member can significantly vary in shape and size, and can be, for example, square or oval. The term “U-shaped” is intended to include any grasping member that is effective to grasp and engage an implant, and is not limited to grasping members having a U-shape. The grasping member and/or the head of the spinal implant can also include a variety of mating elements, including tongue-and-groove connections, dovetail connections, etc. Alternatively, the grasping member can be formed from, for example, opposed pin-type members that are adapted to fit within corresponding bores formed in the head of an implant. The arms can also optionally be slightly flexible to allow the arms to snap-around a portion of the head of a spinal implant.

FIG. 4illustrates the rod pusher member16which is slidably mounted on and/or mated to the elongate member12, and is effective to engage and push a spinal rod toward the grasping member14to seat the rod in a rod-receiving portion of an implant being engaged by the grasping member14. The rod pusher member16can also have a variety of configurations, but is preferably a generally elongate rigid member having a proximal end16aand a distal end16b. The size and cross-sectional shape of the rod-pusher member16can vary, but preferably the rod-pusher member16has a generally cross-sectional shape and includes a substantially planar mounting surface36adapted to rest on the elongate member12. The length lrof the rod pusher member16can also vary, but preferably the rod pusher member16has a length lrless than the length leof the elongate member12.

The rod pusher member16can be mated to the elongate member12using a variety of mating techniques. By way of non-limiting example, the rod pusher member16can include a channel or groove (not shown) formed therein, and the elongate member12can include a corresponding tongue (not shown) formed thereon and adapted to be slidably disposed within the groove. A person having ordinary skill in the art will appreciate that virtually any mating technique can be used to slidably mate the rod pusher member16to the elongate member12.

The distal end16bof the rod pusher member16is adapted to engage a spinal fixation rod, and thus can include a rod-engaging member18formed thereon. The rod-engaging member18can have a variety of configurations, and can be positioned adjacent to the grasping member14, or can be offset from the grasping member14. The rod-engaging member18can be integrally formed on the distal end16bof the rod pusher member16, or alternatively it can be removably mated to the rod pusher member16. The rod-engaging member18can also optionally be adjustably mounted onto the rod pusher member16to allow the length1rof the rod pusher member16to be adapted based on the intended use of the device.

FIG. 5illustrates one embodiment of a rod-engaging member18having opposed arms38a,38bthat are adapted to engage and push a rod toward the grasping member14. The arms38a,38bare preferably mated to a T-shaped member44formed on the distal end16bof the rod pusher member16, and each arm38a,38bis preferably positioned a distance d apart from one another to allow the arms38a,38bto be positioned around the head of an implant, and to allow access to a rod-receiving portion formed in the head of the spinal implant being engaged by the grasping member14. The arms38a,38bare each also preferably aligned with the arms22a,22bof the grasping member14, and they preferably extend in a direction substantially perpendicular to the T-shaped member44. The arms38a,38band the T-shaped member44can have a substantially semi-cylindrical shape, or can have a variety of other shapes.

Each arm38a,38bitself can also vary in shape and size, but preferably each arm is substantially planar and has a generally ramp-like shape such that width w of each arm38a,38b, extending in a direction transverse to the axis A, increases from the proximal end40a,40bto the distal, rod-engaging end42a,42b. The ramp-like shape of the arms38a,38bfacilitates access to the rod-receiving portion of the spinal implant.

The distal, rod-engaging end42a,42bof each arm38a,38bcan include a recess46a,46bformed therein for seating a stabilizing rod. The recesses46a,46bcan have virtually any shape, such as square or semi-cylindrical. The recesses46a,46bcan also be generally elongated to facilitate grasping of the stabilizing rod.

A person having ordinary skill in the art will appreciate that the rod pusher member can have a variety of configurations, but should be adapted to grasp and push a spinal fixation rod into a rod-receiving portion of a spinal implant.

In use, the rod pusher member16is movable between a first proximal position, shown inFIG. 6A, in which the distal end16bof the rod pusher member16is positioned proximal to and a distance apart from the grasping member14formed on the distal end12bof the elongate member12, and a second position, shown inFIG. 6B, in which the distal end16bof the rod pusher member16is positioned adjacent to, or is in contact with, the grasping member14. In the first position, the rod pusher member16is effective to grasp a spinal fixation rod R. The rod pusher member16can then be moved to the second position to push the rod R into a rod receiving portion48of a spinal implant I being engaged by the grasping member14.

In order to move the rod pusher member16between the first and second positions, the proximal end12aof the elongate member12and the proximal end16aof the rod pusher member16can be mated to an actuating member50. The actuating member50can extend along the axis A of the device10, but it preferably extends in a direction substantially transverse to the axis A. More preferably, the actuating member50can be a handle or grip-like element that extends in a direction opposed to the grasping member14and the rod engaging member18. This configuration provides better visual access to the surgical site.

While virtually any actuating member can be used with the present invention,FIGS. 1 and 7illustrate a preferred embodiment of an actuating member50having first and second opposed handle members52,54. The first handle member52is mated to or formed integrally with the proximal end12aof the elongate member12, and the second handle member54is linked to the proximal end16aof the rod pusher member16. Both of the handle members52,54can be movably mated to one another, but preferably the first handle member52is stationary and fixedly attached to the elongate member12, and the second handle member54is pivotally mated to the first handle member52and to the rod pusher member16. As shown, the handle members52,54are mated to one another at pivot point P. The second handle member54is adapted to rotate at pivot point P, and is mated to the rod pusher member16to move the rod pusher member16between the first and second positions. As shown, the second handle member54includes a distal end62that extends into a slot64formed in the rod pusher member16. Movement of the handle54from the non-actuated position, shown inFIG. 1, to the actuated position, shown inFIG. 7, causes the distal end62of the handle54to engage the slot64and move the rod pusher member16in a distal direction. A person having ordinary skill in the art will appreciate that a variety of techniques can be used to effect movement of the rod pusher member16.

The actuating member50can also optionally include a biasing element56disposed between the handle members52,54. The biasing element56is preferably effective to bias the first and second handle members52,54to an open position, as shown inFIG. 1, wherein the rod-engaging member18is positioned a distance apart from the grasping member14. A force can be applied to the first and second handle members52,54to overcome the biasing force of the biasing element56, and thereby move the rod pusher member16from the first, proximal position to the second, distal position. A variety of biasing elements56can be used with the actuating member50including, for example, spring mechanisms. As shown inFIGS. 1 and 7, the biasing element56is formed from opposed flexible members that force the first and second members into the open position.

A person having ordinary skill in the art will appreciate that virtually any actuating member can be used to move the rod-pusher member16and/or the elongate member12between the open and closed positions. By way of non-limiting example, the device10can include a ratchet-type mechanism having a trigger that, upon actuating, is effective to move the rod pusher member16in a distal direction in predetermined increments with respect to the elongate member12. The device10can also optionally include a locking mechanism effective to lock the device10in the second, actuated position. A person having ordinary skill in the art will appreciate that the device can include a variety of other features to facilitate use of the device.

FIGS. 8-10illustrate another embodiment of a spinal rod approximator210in which the rod reducer member218is substantially parallel to the axis a, rather than offset from the axis, as shown inFIG. 1of rod reducer10. Except as otherwise discussed herein, rod approximator210is substantially the same as rod approximator10, and the elements of rod reducer210that are the same as the elements of rod reducer10are similarly designated but have a prefix “2” added to the reference numeral used for that element in the description of rod reducer210. As shown inFIG. 8, rod reducer210includes an elongate member212having a grasping member214formed on a distal end thereof, and a rod pusher member216slidably mated to or mounted on the elongate member212. The grasping member214is effective to grasp a portion of a spinal implant, and the pusher member216is effective to grasp and engage a stabilizing rod and push the rod into a rod-receiving portion of the spinal implant being grasped by the grasping member214.

The grasping member214is shown in more detail inFIG. 9and includes a first, upright portion221that extends along the longitudinal axis A of the device210, and a second portion227having opposed arms222a,222bthat extend in a direction substantially perpendicular to the upright portion221. The upright portion221can have virtually any shape and size, but should include a rod-seating recess225formed therein that extends from a position distal to the proximal end221aof the upright portion through the second portion227to define the opposed arms222a,222b. The recess225is adapted to receive a rod that extends between the arms222a,222bin a direction substantially parallel to the direction of the arms222a,222b.

The arms222a,222bare similar to arms22a,22bshown inFIG. 1. Each arm222a,222bincludes a semi-cylindrical wall223a,223bformed on proximal end thereof for contouring the head of an implant being engaged. The arms222a,222bare configured to fit within corresponding recesses or slots formed in the head of the implant. The slots in the implant (not shown should be positioned in a distal portion of each leg of a U-shaped head of an implant. This configuration allows the rod to be aligned with the rod-receiving portion in the head of the implant.

The rod-engaging member218is shown in more detailFIG. 10, and is effective to push a spinal rod toward an implant being grasped by the grasping member214. The rod-engaging member218can have a variety of configurations, but as shown has a generally rectangular shape and includes opposed proximal and distal ends240,242. The proximal end240is mated to or integrally formed on the distal end of the rod-pusher member216, and the distal end242is adapted to receive a spinal rod. The distal end242preferably includes a recess244formed therein for seating the spinal rod to facilitate reduction of the rod toward the implant being engaged by the grasping member214. The recess244should extend in the same direction as the arms222a,222bof the grasping member214to allow a rod to be positioned between the arms222a,222band seated in the recess244.

In use, the device210is operated in the same manner as device10, except that the implant is grasped in a different direction. In particular, device10grasps the implant beneath the rod-receiving recess formed in the U-shaped head of an implant, while device210grasps the implant along each leg of the U-shaped head. A person having ordinary skill in the art will appreciate that modifications can be made to the rod approximator to allow an implant to be grasped at different locations and in different directions with respect to the U-shaped head.

FIGS. 11A-11Cillustrate one embodiment of a spinal implant100for use with a rod approximator according to the present invention. As shown, the implant100includes a threaded shank102and a generally U-shaped head104having an open proximal end104a, and a closed distal end104battached to the shank102. Preferably, the shank102is rotatably mated to the distal end104bof the head104to allow rotation of the head104. A variety of techniques can be used to allow rotation of the head with respect to the shank102. By way of non-limiting example, the shank102can include an enlarged proximal portion (not shown) and can be disposed through a bore formed in the distal end104bof the head104. The enlarged proximal portion will prevent the shank102from extending completely through the bore. Once a spinal rod is disposed within the U-shaped head and secured by a closure mechanism, the rod will prevent rotation of the head104with respect to the shank102.

The U-shaped head104includes opposed side walls114a,114bthat define a rod-receiving portion108for seating a spinal fixation rod, and that are substantially parallel to one another. The inner surface of the head104includes threads112formed thereon for mating with a closure mechanism effective to secure the rod in the rod-receiving portion108of the head104, and the outer surface of the head104includes opposed recesses106a,106bformed therein for receiving the arms22a,22bof the grasping member14. The recesses106a,106bextend in a direction transverse to the direction of the side walls114a,114b, and are preferably positioned just proximal to the distal end104bof the head104. Thus, the recesses106a,106bare positioned distally adjacent to the cut out portions115a,115bthat form the rod-receiving portion108of the head104of the implant100: The recesses106a,106bcan, however, be disposed in the distal portion of each side wall114a,114bto allow the implant to be grasped in an opposed direction. The position of the recesses106a,106bis particularly advantageous in that it facilitates engagement of the implant100by a rod approximator since the grasping member14does not need to grasp the implant100underneath the head104. The position of the recesses106a,106balso avoids potential contact with adjacent bone structures.

Each recess106a,106bcan have a variety of shapes and sizes, but preferably the recesses106a,106bare elongated slots which form upper and lower shoulders108a,108b. The upper and lower shoulders108a,108bcan each be substantially planar, but preferably the lower shoulder108bis substantially planar and the upper shoulder108ais substantially planar but includes opposed ends109a,109bthat are curved such that they extend away from the lower shoulder108b. The curved shape of the upper shoulder108aallows the arms22a,22bof the grasping member14to be inserted into the recesses106a,106bat an angle.

A person having ordinary skill in the art will appreciate that the implant100can have a variety of configurations, and that the features illustrates can be used on a variety of implants, includes hooks and other fastener devices.

In use, one or more spinal implants100are screwed into vertebral bone structures. Typically, where two spinal implants100are fastened into adjacent vertebra, a spinal rod is inserted into the rod-receiving portion108of each implant. However, due to the alignment of the implants100, it can be difficult to position the rod within each rod-receiving recess108. Thus, a rod approximator device is necessary. The rod approximator device10is used by inserting the arms22a,22bof the grasping member14into the corresponding recesses106a,106bof the head104of the implant100. With the rod pusher member16in the first, proximal position, the device can be manipulated to place the spinal rod between the rod engaging member18and the head104of the implant100. The first and second handle members52,54can then be grasped and squeezed together to cause the rod pusher member16to move to the second, distal position, thereby causing the rod engaging member18to grasp and push the stabilizing rod into the rod-receiving recess108formed in the head104of the spinal implant100. While maintaining the device10in the second, actuated position, a closure mechanism can be threaded into the head104of the spinal implant100to secure the stabilizing rod in the rod-receiving recess108.