Spinal fixation system

A spinal fixation system includes a pedicle screw having a passage extending along a longitudinal axis of the screw. The passage has a proximal opening at a proximal end of the screw and a distal opening at a distal end of the screw. A drill extends through the passage, a first end of the drill extending out the distal opening of the passage.

FIELD OF THE INVENTION

The present invention relates to instrumentation and methods used in the performance of spinal fusion procedures. In particular, the present invention relates to a spinal fixation system and related surgical methods.

BACKGROUND OF THE INVENTION

The spinal column is comprised of twenty-six interlocking vertebrae. These vertebrae are separated by disks. The spine provides load-bearing support for one-half of the body's mass and it protects the nerves of the spinal column. The disks provide shock absorption and facilitate the bending of the spine.

The combination of the vertebrae and disks at each vertebral segment allows for motion of the spine, in particular, flexing, rotation, and extension. The motion and support functions of the spine, in combination with the many interlocking parts and nerve roots associated with the spinal column can result in back pain due to various reasons. Such back pain may result from the degeneration of disks due to age, disease, or injury. Further, vertebral bodies may be compromised due to disease or defect, such as a tumor, or injury, such as fracture.

Spinal fusion or fixation surgery is one way to treat back pain. Further, spinal fusion or fixation may be used to correct an abnormal curvature of the spine or stabilize the spine due to injury or disease affecting one or more disks or vertebrae. In a spinal fusion procedure, two or more adjacent vertebrae in the spine are fused together. The fusion is typically accomplished by the utilization of spinal instrumentation including pedicle screws and associated rods or plates used to mechanically fix the vertebrae together. Pedicle screws are typically used in spinal fusion surgery because the pedicle serves as a strong mechanical attachment point to the spine. Bone graft material may be utilized to aid in the creation of bone structure between the fused vertebrae to create a single bone.

Spinal fixation components vary depending on the system being utilized but typically include pedicle screws that are inserted through the pedicle and into the vertebral body. The pedicle screws are attached to one another by a linking device, such as a rod or plate, that extends vertically along the row of pedicle screws that are inserted. Several coupling systems are known in the art that are used for coupling the pedicle screws to the linking device, which is oriented parallel to the spinal column. Typically two columns of pedicle screws and linking devices are used, one on each side of the spinal column. After installation, the two linking devices may be attached to one another to provide additional stabilization of that portion of the spine. As an alternative or in addition to pedicle screws, spinal hooks may be used, each spinal hook being coupled to a vertebra via a portion of the vertebral arch.

Because of anatomical variations, the pedicle screws that are fixed to one another in a spinal fusion procedure may not be in longitudinal alignment with one another. Accordingly, spinal fixation systems, whether utilizing a rod or a plate, strive to allow some variability in the placement of the pedicle screws while still accomplishing the goal of fixation with a single rod or plate along the pedicle screws.

One challenge associated with the design of a spinal fixation system is the connection between the pedicle screws and the linking device. Ideally, the number of components involved should be minimized, especially the number of components that must be threaded together (such as nuts and rods) in order to ease the assembly process and minimize the overall time of the surgical procedure.

There is also a need for a spinal fixation system that may be utilized with a minimally invasive surgical approach, such as one that utilizes smaller access apertures or ports rather than a large incision along the entire portion of the spine being treated. A spinal fixation system that addresses the needs for a minimally invasive approach may also address the desire to utilize bone graft material along the fixation site to enhance bony in-growth.

Further, there is a need for a spinal fixation system that not only utilizes fewer components but that requires fewer steps for assembly onto the spine, thus shortening the overall time of the surgical procedure.

It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features or addresses one or more of the above-identified needs. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-identified needs.

SUMMARY OF THE INVENTION

The invention relates to a spinal fixation system having a pedicle screw with a longitudinal axis and a passage in the pedicle screw extending along the longitudinal axis, the passage having a proximal opening at a proximal end of the screw and a distal opening at a distal end of the screw. A drill extends through the passage, a first end of the drill extending out the distal opening.

The invention further relates to a spinal fixation system having a pedicle screw and a linking device configured to connect the pedicle screw to at least one additional pedicle screw. A coupling mechanism is configured to be received on the pedicle screw, the coupling mechanism having a collet and a fastening device, the fastening device connecting both the linking device and the collet to the pedicle screw.

The invention further relates to a spinal fixation system having a pedicle screw with a shaft portion and a threaded portion configured to be screwed into a bone. A linking device is configured to connect the pedicle screw to additional pedicle screws. A coupling mechanism is configured to connect the pedicle screw to the linking device. A bone graft implant has a reservoir configured to contain a bone graft material, and an aperture in the reservoir sized to receive the shaft portion to couple the bone graft implant to the pedicle screw.

The invention further relates to a mechanism for coupling a pedicle screw to a fixation rod in a spinal fixation system. A first plate has a first aperture adapted to receive a pedicle screw and a second plate is hinged to the first plate, the second plate having a second aperture adapted to receive the pedicle screw. A hook extends from the first plate and is configured to receive a fixation rod. An engagement arm extends from the second plate, the engagement arm configured to press against the fixation rod to lock the fixation rod into the hook.

The invention further relates to a spinal instrumentation kit having a pedicle screw with a passage extending along a longitudinal axis, the passage having a proximal opening at a proximal end of the screw and a distal opening at a distal end of the screw. The kit further contains a drill adapted to extend through the passage.

The invention further relates to a method for connecting a pedicle screw to a bone. The method includes the steps of opening an aperture in a patient to permit access to a bone, providing a pedicle screw having a passage extending along a longitudinal axis of the screw, the passage having a keyed portion, a proximal opening at a proximal end of the screw, and a distal opening at a distal end of the screw. The method further includes the steps of providing a drill having a shaft, a cutting tip, and a keyed segment configured to interlock with the keyed portion, inserting the drill into the passage such that the cutting tip protrudes from the distal opening and the keyed segment interlocks with the keyed portion, and rotating the drill and screw to simultaneously drill a pilot hole and screw the pedicle screw into the bone. The method further includes the step of removing the drill from the pedicle screw without also removing the pedicle screw from the bone.

The invention further relates to a method for attaching a pedicle screw to a bone and coupling a linking device to the pedicle screw. The method includes the steps of opening an aperture in a patient to permit access to a bone, providing a pedicle screw having a passage extending along a longitudinal axis of the screw, the passage having a proximal opening at a proximal end of the screw and a distal opening at a distal end of the screw, providing a drill having a shaft and a cutting tip, and inserting the drill into the passage such that the cutting tip protrudes from the distal opening and the shaft protrudes from the proximal opening. The method further includes the steps of providing a linking device and a coupling mechanism configured to connect the linking device to the pedicle screw, the coupling mechanism having at least one component having an aperture configured to receive the pedicle screw, placing the component over the shaft of the drill, sliding the component onto the pedicle screw, and coupling the linking device to the pedicle screw.

The invention is capable of other embodiments and of being practiced or being carried out in various ways. Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring toFIG. 1, in an exemplary embodiment of the invention, a spinal fixation system includes a bone anchoring element or bone screw, shown as pedicle screw10. The pedicle screw10is coupled to a fixation element or linking device, shown as fixation plate12, via a coupling mechanism14. In use, the pedicle screw10may be inserted through a pedicle and into a vertebra and linked to other pedicle screws by the fixation plate12. The length of the fixation plate12is chosen to accommodate the total distance between the pedicle screws that are linked together.

Referring toFIG. 2, the pedicle screw10includes a threaded portion16and a non-threaded upper portion, shown as post18. A tip20may be configured to be self-drilling and a shoulder or flange22may extend from the screw10between the post18and threaded portion16. At the top of the post18, an engagement mechanism for a screwdriver or drill, shown as recess24, may be utilized. A receiver26includes a pair of wall portions28that together form a U-shaped receiver sized to receive fixation plate12. The internal side of wall portions28may be threaded to engage with other instrumentation. The wall portions28extend upwardly from base30.

Further referring toFIG. 2, collar32has a threaded interior portion and a shoulder34that is sized to rest upon base30. A collet36includes a number of compressible arms38intended to engage with pedicle screw10upon assembly. A lower set screw40has a head42that may be configured to be grasped by a tool, such as the hex-head configuration shown inFIG. 2. A threaded portion44is configured to engage with the internal threads of the collar32during assembly. A pair of retaining rings46,48engage either side of fixation plate12, the lower retaining ring46resting upon collar32and the upper retaining ring48compressed between the fixation plate12and an upper set screw50. The upper set screw50has a threaded portion52intended to engage with the threaded interior side of wall portions28of the receiver26upon assembly. The upper set screw50may have a head configuration designed to be engaged by a wrench or other tightening tool.

Referring toFIG. 3, while an upper portion of the interior of collar32is threaded to engage with lower set screw40, the lower portion is not threaded but has a tapered interior portion having a more narrow diameter at the bottom of the collar32. During assembly of the fixation system, the collar32is dropped into the receiver26, the shoulder34resting upon the base30. Note that each of the components forming the coupling mechanism has an interior channel or aperture configured to allow the components to be placed upon and encircle the post18. The collet36is placed into collar32, the outer diameter of the collet36being greater along a portion of the longitudinal axis of collet36than the interior diameter of collar32, as shown inFIG. 3. The lower set screw40may then be threaded into collar32, thus engaging collet36and pushing collet36downward through the collar32until the compressible arms38are forced to grip and be secured to post18. Engagement of the post18by the collet36locks the collet36and the other components of the coupling mechanism into place relative to the pedicle screw10for fixation to the fixation plate12.

Note that the collet36may be locked onto post18at any position along the longitudinal axis of post18, affording flexibility in the placement of the coupling mechanism components. In other pedicle screw embodiments, the collet may engage with the threaded portion of the pedicle screw. The flexibility in placement of the collet is important due to the variability in placement of the pedicle screw10depending on the anatomy of the patient's spine. Once the receiver26, collar32, and collet36are locked into place onto pedicle screw10, the fixation plate12may be linked to the pedicle screw10by placing retainer rings46,48over the post18on either side of the fixation plate12and locking the fixation plate12into place by threading upper set screw50into receiver26to complete the assembly.

Further referring toFIG. 3, the recess24extends into the pedicle screw10to create a keyed portion of a passage54that extends the length of the pedicle screw10. The keyed portion may serve as an engagement point for a driver as discussed above.

Referring toFIG. 4, the embodiment of the spinal fixation system shown inFIGS. 1-3is shown installed into a patient's spine. In practice, the pedicle screws10may be individually installed prior to the installation of the fixation plate12across the multiple pedicle screws10. Note that the fixation plate12is centered upon the line of pedicle screws10as opposed to the offset configuration seen with other fixation system embodiments.

Referring toFIG. 5, a fixation system in accordance with another embodiment of the invention is shown and includes a bone coupling element or bone screw, shown as pedicle screw100, a linking device, shown as fixation rod102, and a coupling mechanism (generally shown as coupling mechanism104) used to connect the pedicle screw100and fixation rod102together. The fixation rod102provides similar functionality to the fixation plate12.

Referring toFIG. 6, pedicle screw100includes a threaded portion106and a non-threaded post108. A recess110is provided at the top of pedicle screw100in order to provide an engagement point for a drill or screwdriver. In this embodiment as with other embodiments described herein, the triangle-shaped recess is exemplary only and may take various forms such as a slot or a hexagonal recess depending on the type of tool utilized for turning the pedicle screw. A receiver112includes a pair of wall portions114extending upwardly from base116. A collar118is integrally formed as part of the receiver112. The U-shaped configuration of the upwardly extending wall portions114and base116is suited to receive and be attached to fixation rod102. A collet120is sized to fit into the collar118and be pressed downward by a set screw122, the set screw122having a threaded portion124such that it may be screwed into the collar118. A nut126is sized to be connected to a threaded portion128of the receiver112.

Referring toFIG. 7, the fixation rod102is attached to the pedicle screw100by the various components of the coupling mechanism. In particular, the receiver112is first placed upon the post108, followed by insertion of the collet120and the set screw122into the receiver112and collar118. Tightening the set screw122forces the collet120downward through the narrowing passageway of the collar118such that the compressible arms of the collet120are forced inward to grip and fasten to the post108at the desired point on the post108. Once the collet120is secured onto the post108, the receiver112is also fixed into place and ready for placement of the fixation rod102into the U-shaped channel of the receiver112, followed by the addition of the nut126to secure the fixation rod102into place, completing the installation of the fixation hardware for a particular vertebra.

Further referring toFIG. 7, prior to adding the coupling mechanism and fixation rod, the pedicle screw100is first installed into the vertebra by screwing the pedicle screw100into place, with the use of the self-drilling configuration of pedicle screw100or other installation methods known in the art. Recess110may be used as the engagement point for the pedicle screw100for drilling the pedicle screw into the chosen vertebra. The pedicle screw100may be cannulated as shown by the passage130extending the length of the pedicle screw100with an opening at both the proximal end and the distal end of the pedicle screw100.

Referring toFIG. 8, the spinal fixation system depicted inFIGS. 5-7is shown installed into a patient's spine. Note that different pedicle screws100may protrude from the spine at different heights depending on anatomical variations that may affect how deep the pedicle screw100is drilled into particular vertebra. Accordingly, the use of the collet120that may engage the pedicle screw100at various heights is useful to permit the fixation rod102to be utilized in connecting the various pedicle screws100together.

Referring toFIGS. 9-12, a spinal fixation system according to another embodiment of the invention is shown and includes a bone coupling element, shown as pedicle screw200, a linking device, shown as fixation plate202, and a coupling mechanism, the components generally shown as coupling mechanism204.

Referring toFIG. 10, the pedicle screw200is similar to the pedicle screws described with respect to other embodiments of the invention, and includes a threaded portion206and a non-threaded portion, shown as post208. A recess210provides an interface for a tool or drill used to drill the pedicle screw200through a pedicle and into a vertebral body. A collet214has an elongated design with an inner aperture designed to be fitted over post208, a set of compressible arms216designed to engage the pedicle screw200, and a threaded portion218. A collar212is designed to interface with the compressible arms216. A pair of retaining rings220,222provide an engagement point for the coupling mechanism with the fixation plate202. A fastening device, shown as nut224, has threads configured to engage with the threaded portion218of the collet214.

Referring toFIG. 11, in order to utilize the coupling mechanism to install the friction plate202to the pedicle screw200, the collet214, collar212, and retaining ring220are placed over the post208after installation of the pedicle screw200into the chosen vertebra. The post208upon which the various components of the coupling mechanism are placed provides a guide and retaining function during assembly of the coupling mechanism to ease the attachment of the fixation plate202.

After placement of the fixation plate202over the post208, the retaining ring222and nut224are placed into position over the fixation plate202. Tightening of the nut224performs two functions. First, the nut224engages the threads of the collet214and pulls the compressible arms216up into the collar212in order to depress the compressible arms216into the post208, thereby locking the collet214onto the pedicle screw200. Further, the nut224locks the fixation plate202relative to the pedicle screw200by compressing the fixation plate202between the retaining rings220,222. A passage, shown as passage226extends the length of the pedicle screw200generally extending from the recess210.

The embodiment of the invention shown inFIGS. 9-12requires only one component to be screwed into place, the nut224, which connects both the fixation plate202and the collet214to the pedicle screw200. The rest of the components of the coupling mechanism204slide into place over the post208. Reducing the number of components that must be screwed together in the assembly of the spinal fixation system is advantageous as cross-threading of components that are screwed together is a problem encountered in surgery and reducing the number of components that must be screwed together addresses that issue. Further, only requiring one pair of components to be screwed together per pedicle screw may reduce the time necessary to assemble the spinal fixation system, thereby reducing the overall time required for the operation.

Referring toFIG. 12, the invention shown inFIGS. 9-11is shown as installed into a spine, with two pedicle screws200shown for exemplary purposes although a greater number of pedicle screws200may be utilized, depending on the number of vertebrae to be fixed to one another. The fixation plate202may be of various lengths depending on the number of pedicle screws200used. Because the collet214may engage the pedicle screw200at various points, variations in the heights of the installed pedicle screws200may be addressed in order to result in a continuous height of the fixation plate202by simply varying the points of engagement of the coupling mechanism204on different pedicle screws200.

Referring toFIGS. 13-16, a spinal fixation system according to another embodiment of the invention includes a bone-coupling element, shown as pedicle screw300, a fixation element or linking device, shown as fixation rod302, and a coupling mechanism, generally shown as coupling mechanism304.

Referring toFIG. 14, the pedicle screw100includes a threaded portion306and a non-threaded portion shown as post308. The threaded portion306is bounded by a distal tip310and a flange312. A recess314extends into the post308for engagement by a tool or drill. A collet318has an interior channel sized to fit over the post308. The collet318includes a threaded portion322and a number of compressible arms320. A collar316is sized to fit over the collet318. A receiver for the fixation rod302includes a pair of plates, shown as lower portion328and upper portion330. The plates are hinged so that the upper portion330is pivotally attached to the lower portion328. The lower portion328includes a hook334for engagement with the fixation rod302and the upper portion330includes an engagement arm332that is used to lock the fixation rod302into place. A pair of retaining rings324,326are disposed on either side of the receiver and a fastening device, shown as nut336, is configured to secure the entire coupling mechanism together by threading onto collet318.

Referring toFIG. 15, the coupling mechanism is secured to the pedicle screw300in a similar fashion to that described with respect to the embodiment depicted inFIGS. 9-12via the tightening of nut336onto collet318, thereby pulling the compressible arms320up into the collar316, thereby fixing the collet318into place at the selected height upon pedicle screw300. Engagement with the fixation rod302however is handled differently by using the components of the receiver to attach the coupling mechanism to the fixation rod302with the fixation rod302offset from the longitudinal axis of the pedicle screw300. Further referring toFIG. 15, tightening the nut336onto the collet318not only secures the collet318into place on the pedicle screw300but also drives the upper portion330downward toward the lower portion328until the engagement arm332engages the fixation rod302to fix the fixation rod302into place relative to the coupling mechanism and the pedicle screw300. Accordingly, the fastening device or nut336performs two coupling functions that require at least two fastening components in other designs. During assembly, the various components of the coupling mechanism are stacked onto the pedicle screw300using the post308as a guide after installing the pedicle screw300into the bone. The components of the receiver are configured to be installed on the post308along a range of positions offset from the longitudinal axis of the pedicle screw300to allow for some variability in the angle of the pedicle screw300after installation into the chosen vertebra. Further, like the earlier described embodiments, the coupling mechanism may be adjusted along the longitudinal axis of the pedicle screw300to account for variability in the height of the installed pedicle screw300.

Referring toFIG. 16, the spinal fixation system shown inFIGS. 13-15may be installed in the spine with the fixation rod302oriented on either side of the pedicle screws300by changing the position of the receiver lower portion328and upper portion330. Although two pedicle screws300are shown as fixed by fixation rod302, additional pedicle screws300may be installed in a line with a fixation rod302having the appropriate length to connect the pedicle screws300.

Referring toFIGS. 17-22, in an exemplary embodiment of the invention, a pedicle screw400may be used in conjunction with a driver, shown as drill414, and holding device430. As in earlier described embodiments, the pedicle screw400includes a threaded portion402, a non-threaded post404, a tip406, a flange or ridge410, and a recess412. The drill414includes a shaft416sized to fit within a passage408(seeFIG. 19), a portion having cutting edges418, and a drill tip420. Referring toFIGS. 3,7,11, and15, the pedicle screws shown in various embodiments of the invention are cannulated to include passages54,130,226, and338to accommodate drills such as drill414. Accordingly, the drill414may function as a drill and as a driver for turning the screw. The term “driver” is intended to generically refer to a drill or turning tool or a tool having both functions. A keyed segment422of the drill is shaped to lock into recess412so that when the drill414is rotated, the pedicle screw400is also rotated. An expanded segment424is sized to rest upon the top of post404, and has an outer diameter that is the same as that of post404in a preferred embodiment. An upper keyed segment426provides an interface for a drill or other turning tool used to turn the drill414and the pedicle screw400.

Further referring toFIG. 17, a holding device430is shown as having a cylindrical shape and an attachment mechanism, shown as a number of prongs432, extending from the bottom of the holding device430and intended to snap over the ridge410to connect the holding device430to the pedicle screw400. Referring toFIG. 19, the top of the holding device430may be shaped to engage expanded segment424to lock the drill414into place in the pedicle screw400.

Referring toFIG. 18, once assembled together, the pedicle screw400, drill414, and holding device430create an efficient tool for drilling the pedicle screw into a selected vertebra. The drill tip420extends from the distal opening of the passage in the pedicle screw at the pedicle screw tip406to aid in the insertion of the pedicle screw400. The smaller diameter cutting edges418and sharp cutting tip420may be desired by a surgeon when inserting the pedicle screw400to provide a more accurate placement and initial drilling point for the pedicle screw400, eliminating the necessity of first drilling a pilot hole and utilizing a guide wire to guide the pedicle screw. Inserting a separate guide wire with a separate drill bit requires additional steps in the surgery and additional components, complicating and perhaps lengthening the overall surgery. The holding device430aids in the manipulation of the pedicle screw400and drill414by preventing the drill414from disengaging from the pedicle screw400during the insertion process.

Referring toFIG. 19, the drill414and holding device430may be assembled together with the pedicle screw400prior to connecting the pedicle screw400to the spine and may be assembled by sliding the components together and snapping the holding device430onto the pedicle screw400without having to screw various components together.

Referring toFIG. 20, the assembled device depicted inFIG. 18may be utilized to drill the pedicle screw400into a chosen location in the spine utilizing the drill414in combination with the pedicle screw400. The drill tip420aids in selecting a precise location for drilling the hole for the pedicle screw400.

Referring toFIG. 21, once the pedicle screw400has been screwed into the vertebra, the holding device430may be removed from the pedicle screw400by disengaging the prongs432, which in a preferred embodiment may be disengaged by pulling the holding device430away from the pedicle screw400. Referring toFIG. 22, once the holding device430has been removed from the pedicle screw400, the drill414remains. In a preferred embodiment, the drill may be removed from the pedicle screw400by pulling the keyed segment422out of the recess412. However, the user may elect to leave the drill414in place (or replace the drill414with another driver configured to be inserted into the passage408) during assembly of the coupling mechanism as described below.

Referring toFIG. 23, the drill414may be utilized in conjunction with a pedicle screw after installation of the pedicle screw to aid in the installation of various coupling components. In the embodiment depicted inFIG. 23, the components of the coupling mechanism304shown inFIGS. 13-16are shown for exemplary purposes only. A similar approach may be utilized with the other coupling mechanisms and components shown with respect to the spinal fixation systems described in other embodiments of the invention. The drill414, including upper keyed segment426and expanded segment424, is sized to provide a guide for the coupling components utilized to attach the pedicle screw300to the fixation rod302. Accordingly, after installation of the pedicle screw300, a surgeon may elect to leave the drill414in place and utilize the drill414to serve as a guide for installation of the collet318, collar316, retaining ring324, receiver lower portion328, and upper portion330, retaining ring326, and nut336. Alternatively, the surgeon may remove the drill414and insert a similarly configured driver into the screw to function as the guide.

In a minimally invasive surgical approach, use of the drill414as a guide for the coupling components may be especially useful because a small percutaneous aperture may be made for each installed pedicle screw, and the drill414may extend out of the patient's body to aid in placement of the coupling components. Without the aid of the drill414as a guide in minimally invasive surgical approaches, placement of the components directly onto the post308may be difficult due to the small size of the percutaneous aperture and obstructed visual access.

Referring toFIG. 24, expanding on the concept presented inFIG. 23, the drill414may be left in place in multiple pedicle screws300after the installation of each pedicle screw300. Such an approach requires the use of multiple drills414so that during a surgical operation, each pedicle screw300may be installed with a separate drill414, the drill414left into place for installation of coupling components for each pedicle screw300.FIG. 24depicts two pedicle screws300requiring coupling components for exemplary purposes but the concept may be utilized with any number of pedicle screws.

Referring toFIG. 25, after the coupling components have been put into place and attached to the fixation rod302, the individual drills414may be removed by pulling the drills out of the pedicle screws, leaving the installed components (including the pedicle screws300) in place. One reason for the utilization of a separate drill414which is removable from the installed fixation system is that the surgeon may not wish to utilize components of a fixation system that include a permanently installed sharp cutting tip.

Referring toFIGS. 26 and 27, in accordance with one embodiment of the invention, the spinal fixation system includes a mechanism for inserting bone graft material as part of a spinal fusion procedure, shown as bone graft implant500. The bone graft implant500includes a reservoir, shown as a nylon or fiber mesh bag502, having a pair of end caps504. A number of apertures, shown as grommets506, may be placed in the bag502on both sides of the bag502to permit installation of the bag502over a number of pedicle screws. The bag502may be filled with a bone graft material and utilized to enhance spinal fusion.

Referring toFIG. 27, in one embodiment, the bone graft implant500may be placed over a number of pedicle screws508prior to installation of a linking device, shown as fixation plate510, and the associated coupling mechanism. In the embodiment depicted inFIG. 27, the pedicle screws, fixation plate, and coupling mechanism are similar to the components shown in the spinal fixation system embodiment described above with respect toFIGS. 9-12. In a surgical procedure, the pedicle screws508may be installed into the selected vertebrae, followed by installation of the bone graft implant500, which has already been filled with bone graft material, over the posts of the pedicle screws508. The grommets506provide a mechanism for maintaining the placement of the bone graft implant500in the proper location and also provides an effective guide mechanism where visual access is impaired because the grommets506may be placed over the free posts of the pedicle screws508and glided into position along the pedicle screws. When a minimally invasive approach is used with a small access port for each individual pedicle screw, the bone graft implant500may be inserted into the patients body through one aperture, with the placement of a grommet506over the post of the pedicle screw, and then threaded under the patient's skin up to the next pedicle screw for placement of the next grommet, and so forth for the number of pedicle screws that are being utilized. A string may be threaded between the adjacent pedicle screws to aid in the pulling of the bone graft implant500between the access ports.

The various spinal fixation or instrumentation systems described herein as exemplary embodiments of the invention may be utilized in the performance of spinal fusion procedures using a streamlined method that is intended to simplify and shorten conventional spinal fusion procedures. Prior to operating, imaging of the patient may be utilized to determine the number of pedicle screws that will be linked together as part of the spinal fusion procedure. Further, an image guidance system may be utilized as part of the procedure to aid in the placement of the various components. In the case of an open procedure, an entry site is created in the patient along the portion of the spine into which the pedicle screws will be inserted. In the case of a minimally invasive procedure, individual entry ports may be utilized for implantation of individual pedicle screws. The various embodiments of the invention described herein are particularly suited to a minimally invasive approach because the coupling components are placed upon the screw from the top, allowing insertion and connection of the components via the small percutaneous aperture created for the screw itself in contrast to other designs requiring the use of coupling components that are not in line with the longitudinal axis of the screw, which may require an open procedure.

After creating the entry site and determining the point of insertion of a pedicle screw, the pedicle screws described herein that are self drilling may be drilled directly through the pedicles and into the vertebra. Alternatively, if the drill system described herein is utilized, the drill may be inserted into the pedicle screw, using the holding device to hold the drill in place, and utilized to drill into the pedicle simultaneously with the pedicle screw. Alternatively, conventional procedures may be utilized, including the pre-drilling and tapping of a hole in the pedicle, utilizing a Kirschner wire or guide wire as appropriate. The cannulated pedicle screws described herein are useful for incorporating the drill or for the use of a guide wire as desired by the surgeon.

After installation of the desired number of pedicle screws, the coupling mechanism is then utilized to connect the pedicle screws to a linking device, such as a fixation rod or plate as shown and described herein with respect to several exemplary embodiments. In the case of a minimally invasive procedure, multiple drills may be utilized to aid in the installation of the coupling components and the linking device may be threaded beneath the patient's skin between the various pedicle screws that are being linked to each other.

After the pedicle screws have been placed into the vertebrae, the transverse processes are decorticated prior to placing a bone graft material to aid in the fusion of the adjacent vertebrae. Implantation of the bone graft material is typically done prior to the insertion of the fixation rod or plate to attach the pedicle screws together. The bone graft implant shown in one embodiment inFIGS. 26 and 27may be utilized to insert the bone graft material. If a drill, such as drill414, is utilized during the process of attaching the pedicle screws to the spine, the coupling components may be placed on to the shaft of the drill to aid in the attachment of the fixation rod or plate. The drills that are utilized may then be removed from the pedicle screws. The installation of all the components may be aided by a guidance system such as a fluoronavigation system, especially in the case of minimally invasive procedures requiring image guidance where visual access is obscured.

While the detailed drawings and specific examples given herein describe various exemplary embodiments, they serve the purpose of illustration only. It is to be understood that the invention is not limited in its application to the details of construction and arrangements of components set forth in the preceding description or illustrated in the drawings. It should be noted that the components and/or assemblies of the spinal fixation systems may be constructed from various materials known in the art. Further, while several examples show the invention in the context of pedicle screw embodiments, the invention is also applicable to other surgical procedures involving a bone anchoring element or bone screw. Further, the order of performance of the method steps described with respect to spinal fixation procedures utilizing the various embodiments of the present invention may vary. Furthermore, other substitutions, modifications, changes and omissions may be made in the design, operating conditions, and arrangements of the exemplary embodiments without departing from the scope of the invention as expressed in the appended claims.