US20060085010A1 - Minimally invasive method and apparatus for placing facet screws and fusing adjacent vertebrae - Google Patents

Abstract

The present invention provides a minimally invasive apparatus for placing screws across a facet joint between adjacent first and second vertebrae. The apparatus includes a first K-wire for inserting into the spinous process of the first vertebrae and a first fixation block removably connected to the first K-wire. The apparatus further includes a second K-wire for inserting into a transverse process of the second vertebrae and a second fixation block removably connected to the second K-wire. A rod member is removably connected to both of the first and second fixation blocks. A swivel block assembly includes relatively movable first and second block members. The rod member is removably connected to the first block member. A cannula extends from the second block member. The screws are insertable through the cannula for implantation across the facet joint. Methods for using the apparatus to place facet screws and fuse adjacent vertebrae are also provided.

Description

TECHNICAL FIELD
• The present invention relates to a minimally invasive method and apparatus for placing facet screws and fusing adjacent vertebrae.
BACKGROUND OF THE INVENTION
• Over 200,000 spinal fixation and spinal fusion procedures are performed annually to correct various congenital and degenerative spinal disorders in humans. Many of these corrective surgical procedures are performed in the lumbar and lumbosacral regions of the spine where traumatic and age-related disc degeneration is common. One such procedure involves the implantation of spinal fixation instrumentation, including plates and rods, using pedaled screws. Another procedure involves the implantation of one or more anterior fusion cages into the intervertebral disc space following a discectomy. These and other known spinal fixation and/or fusion procedures can be quite invasive, traumatic, and time consuming. Further, problems with post-operative stability and pseudoarthrosis are often associated with many of these procedures.
• It is well known that the two facet joints, which are formed between each pair of adjacent vertebrae, share and support the axial load on the spine with a respective intervertebral disc. Accordingly, it has been suggested to place screws either directly across the facet joints of adjacent vertebrae or indirectly across the facet joints through the lamina (i.e. translaminar) as both a primary means for spinal fixation and as a secondary means for fixation to augment anterior fusion or pedicle screw fixation instrumentation. Indeed, this suggestion has been accepted by many surgeons as facet screws (direct and translaminar) are now being implanted on a regular basis. In order to further improve upon the use of such facet screws, a minimally invasive method and apparatus for accurately and repeatably placing the facet screws for implantation across the facet joints is needed.
SUMMARY OF THE INVENTION
• The present invention is a minimally invasive apparatus for placing screws across a facet joint between adjacent first and second vertebrae. The apparatus comprises a first K-wire for inserting into the spinous process of the first vertebrae and a first fixation block removably connected to the first K-wire. The apparatus further comprises a second K-wire for inserting into a transverse process of the second vertebrae and a second fixation block removably connected to the second K-wire. A rod member is removably connected to both of the first and second fixation blocks. A swivel block assembly comprises relatively movable first and second block members. The rod member is removably connected to the first block member. A cannula extends from the second block member. The screws are insertable through the cannula for implantation across the facet joint.
• In accordance with one aspect of the invention, each of the first and second K-wires includes means for measuring axial length along the K-wires.
• In accordance with another aspect of the invention, the rod member includes means for measuring axial length along the rod member.
• In accordance with another aspect of the invention, the swivel block assembly includes positioning means for controllably adjusting the angular position of the first and second block members relative to each other.
• The present invention further includes an apparatus for placing translaminar screws across a facet joint between adjacent first and second vertebrae in a minimally invasive surgical procedure. The apparatus comprises a first K-wire for inserting into the spinous process of the first vertebrae and a second K-wire for inserting into a transverse process of the second vertebrae. The apparatus further includes first and second fixation blocks having perpendicularly extending first and second passages. The first K-wire extends into the first passage in the first fixation block and the second K-wire extending into the first passage in the second fixation block. A rod member extends through the second passage in the first fixation block and through the second passage in the second fixation block. A swivel block assembly comprises relatively movable first and second block members. The swivel block assembly includes a third passage extending through the first block member and a fourth passage extending through the second block member. The rod member extends into the third passage. A cannula extends into the fourth passage in the second block member. The translaminar screws are insertable through the cannula for implantation across a facet joint between the first and second vertebrae.
• In accordance with one aspect of the invention, the first and second passages in the first fixation block are offset from each other by a predetermined amount. In accordance with another aspect of the invention, the first and second passages in the second fixation block are offset from each other by the predetermined amount.
• The present invention further provides a minimally invasive surgical method for fusing adjacent upper and lower vertebrae. The method utilizes an apparatus comprising first and second K-wires, first and second fixation blocks, a swivel block having relatively movable first and second block members, a rod member extending between the fixation blocks and the first block member, and a cannula extending from the second block member. The first K-wire is inserted into the center of the spinous process of the upper vertebrae. The second K-wire is inserted into a transverse process on a first side of the lower vertebrae. The first fixation block is secured to the first K-wire and the second fixation block is secured to the second K-wire with the rod member extending across the K-wires. The second block member of the swivel block assembly is secured relative to the first block member to achieve a desired angle for a first axis along which a first screw will be implanted into the facet joint on the first side. The swivel block assembly is secured at a desired axial position on the rod member. Percutaneous access to the second side of the upper vertebrae along the first axis is then obtained via the cannula. A first screw is inserted through the cannula along the first axis and implanted across the facet joint on the first side to attach the upper and lower vertebrae.
• In accordance with additional aspects of the inventive method, the cannula is moved to aim the cannula toward the facet joint on the second side of the vertebrae along a second axis. Percutaneous access along the second axis is then obtained to the facet joint on the second side via the cannula and a bone graft material is placed into the facet joint on the second side through the cannula to assist with fusion of the upper and lower vertebrae.
• In accordance with a further aspect of the inventive method, a burring bit is inserted into the cannula and used to burr the articular surfaces of the facet joint on the second side to widen the facet joint for accepting the bone graft material.
• In accordance with still other aspects of the inventive method, the cannula is removed from percutaneous insertion and the second K-wire is removed from the transverse process on the first side of the lower vertebrae. The second K-wire is then inserted into the transverse process on the second side of the lower vertebrae. The second fixation block is then secured to the second K-wire. Next, the first fixation block is released from the first K-wire and is rotated with the rod member extending across the K-wires. The first fixation block is secured to the first K-wire. The second block member of the swivel block assembly is then secured relative to the first block member to achieve a desired angle for a third axis along which a second screw will be implanted into the facet joint on the second side. The swivel block assembly is secured at a desired axial position along the rod member. Percutaneous access to the first side of the upper vertebrae is obtained via the cannula. A second screw is inserted through the cannula and implanted along the third axis across the facet joint on the second side to attach the upper and lower vertebrae.
• In accordance with additional aspects of the inventive method, the cannula is moved to aim the cannula along a fourth axis toward the facet joint on the first side previously secured with the first screw. Percutaneous access to the facet joint on the first side is obtained via the cannula and a bone graft material is placed through the cannula into the facet joint around the previously implanted first screw to assist with fusion of the upper and lower vertebrae.
• The present invention also provides a minimally invasive surgical method for placing screws through the lamina and across the facet joints between adjacent upper and lower vertebrae. The inventive method utilizes an apparatus comprising first and second K-wires, first and second fixation blocks, a swivel block having relatively movable first and second block members, a rod member extending between the fixation blocks and the first block member, and a cannula extending from the second block member. The first K-wire is inserted into the center of the spinous process of the upper vertebrae. The second K-wire is inserted into a transverse process on a first side of the lower vertebrae so that the second K-wire is parallel to the first K-wire in both the sagittal and coronal planes. The first fixation block is secured to the first K-wire and the second fixation block to the second K-wire with the rod member extending across the K-wires. A desired axial position is calculated for the swivel block assembly along the rod member. A desired angle for the centerline of the cannula is calculated to extend from a second side of the vertebrae toward the facet joint on the first side along a first axis. The second block member of the swivel block assembly is secured relative to the first block member to achieve the desired angle for the first axis. The swivel block assembly is secured at the desired axial position along the rod member. Percutaneous access to the junction of the lumina and the spinous process on the second side of the upper vertebrae is then obtained via the cannula. A first screw is inserted through the cannula. The first screw is implanted along the first axis across the facet joint on the first side to attach the upper and lower vertebrae.
• In accordance with additional aspects of the inventive method, the cannula is removed from percutaneous insertion on the second side and the second K-wire is removed from the transverse process on first side of the lower vertebrae. The second K-wire is then re-inserted into the transverse process on the second side of the lower vertebrae so that the second K-wire is again parallel to the first K-wire in both the sagittal and coronal planes. The second fixation block is secured to the second K-wire. The first fixation block is released from the first K-wire and is rotated with the rod member extending across the K-wires. The first fixation block is then secured to the first K-wire. A desired axial position is calculated for the swivel block assembly along the rod member and the swivel block assembly is secured at the desired axial position. A desired angle is calculated for the centerline of the cannula to extend from the first side of the vertebrae toward the facet joint on the second side along a third axis. The second block member of the swivel block assembly is then secured relative to the first block member to achieve the desired angle. Percutaneous access to the junction of the lamina and the spinous process on the first side of the upper vertebrae is obtained via the cannula and a second screw is inserted into the cannula. The second screw is implanted along the third axis across the facet joint on the second side to attach the upper and lower vertebrae.
• In accordance with further aspects of the inventive method, the cannula is moved from its position over the lamina on the first side of the upper vertebrae and the first and second block members are released to allow relative movement. The second block member is swiveled to aim the centerline of the cannula along a fourth axis toward the facet joint on the first side previously secured with the first screw. Percutaneous access to the facet joint on the first side is obtained via the cannula and a bone graft material is placed through the cannula into the facet joint on the first side around the previously implanted first screw to assist with fusion of the upper and lower vertebrae.
BRIEF DESCRIPTION OF THE DRAWINGS
• The foregoing and other features of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which:
• FIG. 1 is a perspective view of an apparatus for placing facet screws in accordance with the present invention;
• FIG. 2 is a perspective view of a component of the apparatus ofFIG. 1;
• FIG. 2A is a perspective view of a component of the apparatus ofFIG. 1;
• FIG. 3 is a perspective view of another component of the apparatus ofFIG. 1;
• FIG. 4 is a perspective view of another component of the apparatus ofFIG. 1;
• FIG. 4A is a perspective view of another component of the apparatus ofFIG. 1;
• FIG. 5 is an exploded perspective view of another component of the apparatus ofFIG. 1;
• FIG. 6 is a perspective view of a screw to be implanted in accordance with the present invention;
• FIG. 7 is a schematic view of adjacent lumbar vertebrae in the transverse plane and illustrating components of the apparatus ofFIG. 1 at an early stage of the inventive method for placing a facet screw across a facet joint;
• FIG. 8 is a schematic posterior view of the apparatus at a subsequent stage to that ofFIG. 7;
• FIG. 9 is a schematic side view ofFIG. 8;
• FIGS. 10-12 are views similar toFIG. 7 illustrating various steps according to the inventive method;
• FIG. 13 is a schematic posterior view of the apparatus;
• FIGS. 14 and 15 are views similar toFIG. 12 illustrating additional steps according to the inventive method;
• FIG. 16 is a view similar toFIG. 15 illustrating components of the apparatus ofFIG. 1 in different positions for placing a facet screw across a facet joint on the opposite side;
• FIG. 17 is a schematic posterior view of the apparatus at a subsequent stage to that ofFIG. 16;
• FIG. 18 is a schematic side view of the opposite side shown inFIG. 17;
• FIGS. 19-21 are views similar toFIG. 16 illustrating various steps according to the inventive method;
• FIG. 22 is a schematic posterior view of the apparatus;
• FIGS. 23 and 24 are views similar toFIG. 21 illustrating additional steps; and
• FIG. 25 is a view similar toFIG. 24 illustrating the facet screws implanted across the facet joints in the adjacent vertebrae.
DESCRIPTION OF EMBODIMENTS
• The present invention relates to a minimally invasive method and apparatus for placing facet screws and fusing adjacent vertebrae. As representative of the present invention,FIG. 1 illustrates anapparatus10 comprising first andsecond Kirschner wires12 and14 (commonly referred to as “K-wires”), first and second fixation blocks16 and18, arod member20, aswivel block assembly22 comprising first andsecond block members24 and26, and acannula28.
• As may be seen inFIG. 3, therod member20 is a cylindrical component that may be hollow or solid and is made from any suitable metal or plastic. Therod member20 has oppositely disposed first and second ends30 and32 and an outer diameter of 4 to 7 mm. Therod member20 includes anouter surface34 with graduations for measuring axial distances along its length. It is contemplated that other means for measuring axial length along therod member20 could also be used.
• The first and second K-wires12 and14 (FIG. 2) are identical parts, although it should be understood that the K-wires could have different sizes or shapes. Each of the first and second K-wires12 and14 is an elongate rod made of a biocompatible metal or other suitable material with an outer diameter of 2 to 4 mm. As shown inFIGS. 2 and 2A, each K-wire12 and14 has oppositely disposed distal and proximal ends40 and42 and a cylindricalouter surface44 extending between the ends. Thedistal end40 of each of the K-wires12 and14 includes self-tappingthreads46. The cylindricalouter surface44 of each of the K-wires12 and14 includes graduations for measuring axial lengths along each K-wire. It is contemplated that other means for measuring axial length along the K-wires12 and14 could also be used.
• The first and second fixation blocks16 and18 (FIGS. 4 and 4A) are also identical components, although it should be understood that certain aspects of the fixation blocks need not be identical. Each of the first and second fixation blocks16 and18 is a generally rectangular part made of any suitable metal or plastic. The first fixation block16 (FIG. 4) includes perpendicularly extending first andsecond passages50 and52. As shown inFIG. 3, the first andsecond passages50 and52 are offset from each other by a predetermined amount and thus do not intersect. In the assembled condition ofFIG. 1, the first K-wire12 extends into thefirst passage50 in thefirst fixation block16 and therod member20 extends into thesecond passage52.
• Thefirst fixation block16 further includes threaded fasteners in the form ofthumbscrews54 that extend into the first andsecond passages50 and52 for securing the first K-wire12 and therod member20 in the first and second passages, respectively. It should be understood, however, that other suitable means for securing the first K-wire12 and therod member20 to thefirst fixation block16, such as clamps, latches, ratchet mechanisms, etc., could also be used, and that the securing means could be positioned on the exterior of the first fixation block.
• In an identical fashion to thefirst fixation block16, thesecond fixation block18 includes perpendicularly extending first andsecond passages56 and58 that are offset from each other by a predetermined amount and thus do not intersect. The predetermined amount of offset between the first andsecond passages56 and58 in thesecond fixation block18 is the same as the predetermined amount of offset between the first andsecond passages50 and52 in thefirst fixation block16. In the assembled condition ofFIG. 1, the second K-wire14 extends into thefirst passage56 in thesecond fixation block18 and therod member20 extends into thesecond passage58.
• Thesecond fixation block18 further includes threaded fasteners in the form ofthumbscrews54 that extend into the first andsecond passages56 and58 for securing the second K-wire14 and therod member20 in the first andsecond passages56 and58, respectively. It should be understood, however, that other suitable means for securing the second K-wire14 and therod member20 to thesecond fixation block18, such as clamps, latches, ratchet mechanisms, etc., could also be used, and that the securing means could be positioned on the exterior of the second fixation block.
• As shown inFIG. 4, the first andsecond block members24 and26 of theswivel block assembly22 are movable relative to each other about anaxis60. Each of the first andsecond block members24 and26 is a generally rectangular part made of any suitable metal or plastic. Thefirst block member24 includes apassage62 for receiving therod member20. A threaded fastener in the form of athumbscrew54 extends into thepassage62 for securing therod member20 in the passage. Thesecond block member26 further includes apassage64 for receiving thecannula28. A threaded fastener in the form of athumbscrew54 extends into thepassage64 for securing thecannula28 in the passage. It should be understood, however, that other suitable means for securing therod member20 and thecannula28 to theswivel block assembly22, such as clamps, latches, ratchet mechanisms, etc., could also be used, and that these securing means could be positioned on the exterior of the swivel block assembly.
• The first andsecond block members24 and26 further include abuttingsurfaces66 and68, respectively, with means for controllably adjusting the angular position of the block members relative to each other. In accordance with the illustrated embodiment of the invention, this is accomplished via a first ring of radially extendingserrations70 on thesurface66 of thefirst block member24 that is centered on theaxis60 and engaged with a second ring of radially extendingserrations72 on thesurface68 of thesecond block member26 that is also centered on theaxis60. A threaded fastener in the form of athumbscrew74 extends through thefirst block member24 and into a threadedopening76 in thesecond block member26 along theaxis60 for securing the block members in a desired relative angular position. It should be understood, however, that other suitable means for securing theblock members24 and26 in a desired angular position could be used, and that the securing means could be located elsewhere on the block members. Further, it should also be understood that other suitable means for controllably adjusting the relative angular position of the first andsecond block members24 and26 could be employed.
• The cannula28 (FIG. 1) is a thin-walled hollow cylinder made of a biocompatible metal or other suitable material and has oppositely disposed distal and proximal ends80 and82. In accordance with one embodiment of the present invention, thecannula28 has an outer diameter of about 4.5 mm and an inner diameter of about 4.3 mm, although it should be understood that these dimensions may be varied between 4 and 6 mm for the outer diameter and 3.5 to 5 mm for the inner diameter.
• FIG. 6 illustrates ascrew84 to be implanted in accordance with the present invention. Thescrew84 is a self-tapping facet screw made of a biocompatible material, such as titanium. As illustrated inFIG. 6, thescrew84 has ahead86 with a triangular-shapedreceptacle88. In accordance with one embodiment, the screw has a major diameter of 4.3 mm and a minor diameter of 3.8 mm, but it should be understood that these dimensions can be varied based on the pathology and surgical needs. The length L of thescrew84 is determined during surgery as discussed below.
• To use theapparatus10 to place thefacet screw84 across a first facet joint100 between adjacent vertebrae, such as the L4 and L5 vertebrae shown inFIGS. 7-9, in a minimally invasive procedure, the patient is placed in the prone position and X-ray imaging equipment is set-up to provide views in both the antero-posterior (AP) plane and the lateral plane so that the procedure can be performed under fluoroscopic guidance. It should be understood to those skilled in the art that other known navigation assistance devices and equipment could alternatively be used. A stab incision is then made through the skin and the first K-wire12 is inserted through the incision and into the center of the spinous process of the L4 vertebrae. As may be seen inFIGS. 7 and 9, thedistal end40 of the first K-wire12 is screwed into the spinous process until the distal tip reaches a point along afirst axis102 on which afirst screw84 is to be inserted.
• Next, through another percutaneous stab incision, the second K-wire14 is inserted into the transverse process on a first side104 (the left side as viewed inFIG. 7) of the L5 vertebrae and extends in parallel with the first K-wire12 in both the sagittal and coronal planes as shown inFIGS. 7-9. Thedistal end40 of the second K-wire12 is screwed into the transverse process just lateral to the facet joint100 on thefirst side104 of the vertebrae up to the junction of the transverse process and the pedicle on the first side.
• Thefirst fixation block16 is then slid onto the first K-wire12 with the first K-wire extending into thefirst passage50 in the first fixation block. Similarly, thesecond fixation block18 is slid onto the second K-wire14 with the second K-wire extending into thefirst passage56 in the second fixation block. Thefirst end30 of therod member20 is slid then into thesecond passages52 and58 in the first and second fixation blocks16 and18, respectively, so that it extends across the first and second K-wires12 and14. Thethumbscrews54 that extend into thesecond passages52 and58 are tightened to secure therod member20 to the fixation blocks16 and18.
• According to the inventive method, the next steps involve calculations to determine the following three parameters: (1) the length L₁of thescrew84 to be implanted; (2) the desired angle A₁for thecannula28 to extend from theswivel block assembly22, which provides the trajectory for the implantation of afirst screw84 across the facet joint100 on thefirst side104; and (3) the desired axial position D₁for theswivel block assembly22 along therod member20. As will be seen in the calculations set forth below, theapparatus10 according to the present invention utilizes the position and relationship of the first and second K-wires12 and14 to determine the entry point and trajectory upon which thescrew84 is implanted into the L4 and L5 vertebrae.
• The screw length L₁is determined by measuring the axial difference X₁between the two identical K-wires12 and14 and measuring the horizontal difference Y₁between the two K-wires. The graduations on the K-wires12 and14 and/or another suitable means can assist in taking these measurements. The screw length L₁is calculated with the following equation: L₁=√(X₁²+Y₁²). Use of this equation to determine the desired screw length L₁helps to ensure that thescrew84, when implanted across the facet joint100, will not extend beyond the cortex of the superior articular process where nerve damage could become an issue.
• The desired angle A₁for thecannula28 to extend from theswivel block assembly22, which provides the trajectory for the implantation of thefirst screw84 across the facet joint100 on thefirst side104, is calculated based on the measured X and Y values and the angle between these distances using the following equation: A₁=tan⁻¹(Y₁/X₁). As shown inFIG. 5, the calculated angle A₁between the proximal ends42 of the K-wires12 and14 also defines the angle (A₁) between the centerline of therod member20 and thecenterline108 of thesecond passage64 through thesecond block member26. Thecenterline106 of thepassage64 is also the centerline of thecannula28 and is co-linear with thescrew trajectory axis102, as may be seen inFIG. 7. Thesecond block member26 is then rotated about theaxis60 relative to thefirst block member24 to set the desired angle A₁for thecenterline106 of thecannula28, which extends from the second block member. At the desired angle A₁, the first and second rings ofserrations70 and72 on the first andsecond block members24 and26, respectively, are brought into engagement and secured by thethumbscrew74 to ensure that the relative angular position of the block members is fixed. It should be understood by those skilled in the art that other means, such as an angle measuring device, for determining the desired angle A₁could also be used in conjunction with the distances X₁and Y₁, between the K-wires12 and14.
• The axial position, or distance, D₁for theswivel block assembly22 on therod member20 is calculated by first measuring the distance Z₁of penetration of the first K-wire12 (i.e., the distance Z₁extends between the distal tip of the first K-wire and the skin108) using the graduations on the first K-wire. The distance D₁, is then calculated with the following equation: D₁=(X₁/Y₁) Z₁. The distance D₁, for theswivel block assembly22 along therod member20 is measured from the centerline of the first K-wire12 to theaxis60 of the swivel block assembly. The graduations on therod member20 or another suitable means can be used for setting theswivel block assembly22 at the desired axial position.
• Next, theswivel block assembly22 is slid onto thesecond end32 of therod member20, which is projecting out over a second side110 (or right side as viewed inFIG. 7) of the L4 and L5 vertebrae, with therod member20 extending through thepassage62 in thefirst block member24. Thethumbscrew54 is used to secure theswivel block assembly22 at the calculated desired axial position D₁on therod member20.
• Therod member20 and theswivel block assembly22 are then lowered to a height above theskin108 that provides sufficient clearance for the swivel block assembly as shown inFIG. 7. Finally, the first and second fixation blocks16 and18 are secured to the first and the second K-wires12 and14, respectively, with thethumbscrews54. Theapparatus10 is now in position for thefirst screw84 to be placed across the facet joint100 on thefirst side104 of the L4 and L5 vertebrae.
• A scalpel (not shown) is used to incise theskin108 on thesecond side110 of the vertebrae to accept thecannula28. With thecannula28 temporarily removed, the incision is made using thepassage64 through thesecond block member24 of theswivel block assembly22 to orient the incision along theproper axes102 and106. Under fluoroscopic guidance, aguidewire120 is passed through the incision along theaxes102 and106 to the starting point for thescrew84 which is located adjacent the junction of the spinous process and the lamina as shown inFIG. 7. It is contemplated that a Jamshidi needle or other suitable instrument could be used in place of theguidewire120.
• Next, ablunt obturator122 is passed over theguidewire120 to create subcutaneous space for thecannula28 along theaxis102. Thecannula28, which is guided for movement along theaxes102 and106 by virtue of thepassage64 through thesecond block member26, is then passed over theobturator122 and theguidewire120. Thecannula28 is moved along theaxes102 and106 until the distal end of the cannula docks against the lamina on thesecond side110 of the L4 vertebrae as shown inFIGS. 8 and 9. Theguidewire120 and theobturator122 are then removed from thecannula28. At this point in the procedure, a small (e.g., 2 mm) diameter scope may be passed down thecannula28 to inspect the anatomy and the condition of the vertebrae.
• After ensuring that all of thethumbscrews54 and74 are secure and that the alignment of theaxis102 is correct, a drill bit130 (FIG. 10) is inserted into thecannula28. Thedrill bit130 is rotated by a drill (not shown) to drill apilot hole132 along theaxis102 through the lamina on thesecond side110 of the L4 vertebrae, through the inferior articular process on thefirst side104 of the L4 vertebrae, across the facet joint100 on the first side, and into the superior articular process of the L5 vertebrae. It is contemplated that a drill guide (not shown) could be used to center thedrill bit130 in thecannula28 and ensure that thepilot hole132 extends along theaxis102.
• As shown inFIG. 11, the self-tappingscrew84 is then inserted into thecannula28 and screwed into thepilot hole132 using adriver134. In the illustrated embodiment, thehead86 of thescrew84 has a maximum outer diameter that matches the inner diameter of asecond cannula136 that is inserted into thecannula28 to aid in keeping the screw aligned on theaxis102 during implantation. Further, the illustrateddriver134 has a triangular tip for receipt in thereceptacle88 of thescrew84, although it should be understood that the receptacle and the corresponding driver tip could utilize a different geometry. Thescrew84 is advanced until thehead86 seats against the lamina on thesecond side110 of the L4 vertebrae. Fluoroscopic guidance coupled with the aforementioned calculation to select the length L₁of thescrew84 ensures that the distal tip of the screw does not penetrate beyond the cortex of the L5 vertebrae. As implanted, thescrew84 extends across the facet joint100 to connect the inferior articular process of the L4 vertebrae to the superior articular process of the L5 vertebrae.
• With thefirst screw84 implanted, thecannula28 is removed from theskin108 and thethumbscrew74 is released to allow relative movement of the first andsecond block members24 and26. Thesecond block member26 is then swiveled to aim thecenterline106 of thecannula28 along a second axis140 (FIG. 13) that extends toward a facet joint142 (FIG. 12) on thesecond side110 of the vertebrae. In order to aim thecannula28 toward the facet joint142, theother thumbscrews54 may also be released to allow additional movement of theswivel block assembly22. Releasing theother thumbscrews22 may allow thecannula28 to be positioned over the existing incision through theskin108 while being aimed toward the facet joint142 along theaxis140 so that the same incision can be utilized again.
• After tightening all of thethumbscrews54 and74 to secure the components of theapparatus10 in the positions shown inFIG. 12, the guidewire120 (or Jamshidi needle, etc.) is passed through the incision along theaxis140 to the surface of the facet joint142 on thesecond side110 of the L4 and L5 vertebrae under fluoroscopic guidance. Next, theblunt obturator122 is passed over theguidewire120 to create subcutaneous space for thecannula28 along theaxis140. Thecannula28, which is guided for movement along theaxes140 and106 by virtue of thepassage64 through thesecond block member26, is then passed over theobturator122 and theguidewire120. Thecannula28 is moved along theaxes140 and106 until the distal end of thecannula28 docks against the surface of the facet joint142 as shown inFIGS. 13 and 14. Theguidewire120 and theobturator122 are then removed from thecannula28.
• After ensuring that all of thethumbscrews54 and74 are secure and that the alignment of theaxis140 is correct, a burring bit150 (FIG. 14) is inserted into the cannula. The burringbit150 is rotated by a drill (not shown) to burr the opposingsurfaces152 and154 of the inferior articular process and the superior articular process on thesecond side110 of the L4 and L5 vertebrae, respectively. Burring thesesurfaces152 and154 widens the facet joint so that a bone graft material is more easily placed into the facet joint142. It is contemplated that thecannula28 may be moved slightly along the facet joint142 during the burring process in order to access a larger area of the facet joint with the burringbit150.
• After thearticular surfaces152 and154 of the facet joint142 on thesecond side110 of the L4 and L5 vertebrae have been burred out, a bone graft (or bone substitute) material160 (FIG. 15) for helping to fuse the L4 and L5 vertebrae is placed into the facet joint142 through thecannula28. Thebone graft material160 may be fed into the facet joint142 using any known suitable instrument(s). Thecannula28 is then removed from the incision on thesecond side110 of the vertebrae.
• The next steps in the process are to loosen all of thethumbscrews54 and74, remove the fixation blocks16 and18 from the K-wires12 and14, and disassemble theswivel block assembly22 from therod member20. The second K-wire14 is then removed from the transverse process on thefirst side104 of the L5 vertebrae. Next, through another percutaneous stab incision, the second K-wire14 is inserted into the transverse process on thesecond side110 of the L5 vertebrae so that it again extends in parallel with the first K-wire12 in both the sagittal and coronal planes as shown inFIGS. 16-18. Thedistal end40 of the second K-wire14 is screwed into the transverse process just lateral to the facet joint142 on thesecond side110 of the vertebrae up to the junction of the transverse process and the pedicle.
• Thefirst fixation block16 is then slid onto the first K-wire12 with the first K-wire extending into thefirst passage50 in the first fixation block. Similarly, thesecond fixation block18 is slid onto the second K-wire14 with the second K-wire extending into thefirst passage56 in the second fixation block. Thefirst end30 of therod member20 is slid then into thesecond passages52 and58 in the first and second fixation blocks16 and18, respectively, so that it extends across the first and second K-wires12 and14. Thethumbscrews54 that extend into thesecond passages52 and58 are tightened to secure therod member20 to the fixation blocks16 and18.
• Once again, the next steps in the process involve calculations to determine the following three parameters: (1) the length L₂of asecond screw84 to be implanted; (2) the desired angle A₂for thecannula28 to extend from the swivel block assembly, which provides atrajectory axis162 for the implantation of thesecond screw84 across the facet joint142 on thesecond side110; and (3) the desired axial position D₂for theswivel block assembly22 along therod member20. As mentioned above, theapparatus10 according to the present invention utilizes the position and relationship of the first and second K-wires12 and14 to determine the entry point and trajectory upon which thesecond screw84 is implanted into the L4 and L5 vertebrae.
• The screw length L₂is determined by measuring the axial difference X₂between the two identical K-wires12 and14 and measuring the horizontal difference Y₂between the two K-wires. The graduations on the K-wires12 and14 or another suitable means can assist in taking these measurements. The screw length L₂is then calculated with the following equation: L₂=√(X₂²+Y₂²). Use of this equation to determine the desired screw length L₂helps to ensure that thesecond screw84, when implanted across the facet joint142, will not extend beyond the cortex of the superior articular process where nerve damage could become an issue. It should be noted that in many cases, the lengths for the first andsecond screws84 will likely be the same.
• The desired angle A₂for thecannula28 to extend from theswivel block assembly22, which provides the trajectory for the implantation of thesecond screw84 across the facet joint142 on thesecond side110, is calculated with the following equation: A₂=tan⁻¹(Y₂/X₂). As shown inFIG. 16, the calculated desired angle A₂between the proximal ends42 of the K-wires12 and14 also defines the angle (A₂) between the centerline of therod member20 and thecenterline106 of thesecond passage64 through thesecond block member26. The centerline of thepassage64 is also the centerline of thecannula162, as may be seen inFIG. 16. Thesecond block member26 is then rotated about theaxis60 relative to thefirst block member24 to set the desired angle A₂for thecenterline106 of thecannula28, which extends from the second block member. At the desired angle A₂, the first and second rings ofserrations70 and72 on the first andsecond block members24 and26, respectively are brought into engagement and secured by thethumbscrew74 to ensure that the relative angular position of the block members is fixed. It should be understood by those skilled in the art that other means, such as an angle measuring device, for determining the desired angle A₂could also be used in conjunction with the distances X₂and Y₂between the K-wires12 and14.
• The axial position, or distance, D₂for theswivel block assembly22 on therod member20 is calculated by first measuring the distance Z₂of penetration of the first K-wire12 (i.e., the distance Z₂extends between the distal tip of the first K-wire and the skin108) using the graduations on the first K-wire. The distance D₂is then calculated with the following equation: D₂=(X₂/Y₂) Z₂. The distance D₂for theswivel block assembly22 along therod member20 is measured from the centerline of the first K-wire12 to theaxis60 of theswivel block assembly22. The graduations on therod member20 or another suitable means can be used for setting theswivel block assembly22 at the desired axial position.
• Next, theswivel block assembly22 is then slid onto thesecond end32 of therod member20, which is projecting out over thefirst side104 of the vertebrae, with the rod member extending through thepassage62 in thefirst block member24. Thethumbscrew54 is used to secure theswivel block assembly22 at the calculated desired axial position D₂on therod member20.
• Therod member20 and theswivel block assembly22 are then lowered to a height above theskin108 that provides sufficient clearance for the swivel block assembly as shown inFIG. 16. Finally, the first and second fixation blocks16 and18 are secured to the first and second K-wires12 and14, respectively, with the thumbscrews. Theapparatus10 is now in position for thesecond screw84 to be placed across the facet joint142 on thesecond side110 of the vertebrae. It is important to note at this point that the predetermined offset between the first andsecond passages50 and52 in the first fixation blocks16 and the first andsecond passages56 and58 in thesecond fixation block18 positions therod member20 and theswivel block assembly22 so that theaxis162 for implantation of thesecond screw84 is offset from theaxis102 on which thefirst screw84 was implanted. This offset ensures that thesecond screw84 does not intersect with thefirst screw84 as it extends through the spinous process of the L4 vertebrae.
• The scalpel (not shown) is used to incise theskin108 on thefirst side104 of the vertebrae to accept thecannula28. With thecannula28 temporarily removed, the incision is made using thepassage64 through thesecond block member24 of theswivel block assembly22 to orient the incision on theaxes106 and162. Under fluoroscopic guidance, theguidewire120 is passed through the incision along theaxes106 and162 to the starting point for thescrew84 which is located adjacent the junction of the spinous process and the lamina as shown inFIG. 16. As discussed above, it is contemplated that a Jamshidi needle or other suitable instrument could be used in place of theguidewire120.
• Next, theblunt obturator122 is passed over theguidewire120 to create subcutaneous space for thecannula28 along theaxis162. Thecannula28, which is guided for movement along theaxes106 and162 by virtue of thepassage64 through thesecond block member26, is then passed over theobturator122 and theguidewire120. Thecannula28 is moved along theaxes106 and162 until the distal end of the cannula docks against the lamina on thefirst side104 of the L4 vertebrae as shown inFIGS. 17 and 18. Theguidewire120 and theobturator122 are then removed from thecannula28. At this point in the procedure, the small diameter scope may again be passed down thecannula28 to inspect the anatomy and the condition of the vertebrae.
• After ensuring that all of thethumbscrews54 and74 are secure and that the alignment of theaxis162 is correct, the drill bit (FIG. 19) is inserted into thecannula28. Thedrill bit130 is rotated by a drill (not shown) to drill apilot hole132 along theaxis162 through the lamina on thefirst side104 of the L4 vertebrae, through the inferior articular process on thesecond side110 of the L4 vertebrae, across the facet joint142 and thebone graft material160 therein, and into the superior articular process of the L5 vertebrae. It is contemplated that a drill guide (not shown) could be used to center thedrill bit130 in thecannula28 and ensure that thepilot hole132 extends along theaxis162.
• As shown inFIG. 20, the self-tappingsecond screw84 is then inserted into thecannula28 and screwed into thepilot hole132 using thedriver134. In the illustrated embodiment, thehead86 of thescrew84 has a maximum outer diameter that matches the inner diameter of thesecond cannula136 to aid in keeping the screw aligned on theaxis162 during implantation. Further, the illustratedscrew head86 has a triangular receptacle for receiving the triangular tip on thedriver134, although it should be understood that the receptacle and the corresponding driver tip could utilize a different geometry. Thescrew84 is advanced until thehead86 seats against the lamina on thefirst side104 of the L4 vertebrae. Fluoroscopic guidance coupled with the aforementioned calculation to select the length L₂of the screw ensures that the distal tip of the screw does not penetrate beyond the cortex of the L5 vertebrae. As implanted, thesecond screw84 extends across the facet joint142 and thebone graft material160 in the facet joint connect the inferior articular process of the L4 vertebrae to the superior articular process of the L5 vertebrae.
• With thesecond screw84 implanted, thecannula28 is removed from theskin108 and thethumbscrew74 is released to allow relative movement of the first andsecond block members24 and26. Thesecond block member26 is then swiveled to aim thecenterline106 of thecannula28 along a fourth axis170 (FIG. 22) that extends toward the facet joint100 on thefirst side104 of the vertebrae. In order to aim thecannula28 toward the facet joint100, theother thumbscrews54 may also be released to allow additional movement of theswivel block assembly22. Releasing theother thumbscrews54 may allow the cannula to be positioned over the existing incision while being aimed toward the facet joint100 along theaxis170 so that the same incision can be utilized again.
• After tightening all of thethumbscrews54 and74 to secure the components of theapparatus10 in the positions shown inFIG. 21, the guidewire120 (or Jamshidi needle, etc.) is passed through the incision along theaxis170 to the surface of the facet joint100 on thefirst side104 of the vertebrae under fluoroscopic guidance. Next, theblunt obturator122 is passed over theguidewire120 to create subcutaneous space for thecannula28 along theaxis170. Thecannula28, which is guided for movement along theaxes106 and170 by virtue of thepassage64 through thesecond block member26, is then passed over theobturator122 and theguidewire120. Thecannula28 is moved along theaxes106 and170 until the distal end of the cannula docks against the surface of the facet joint100 as shown inFIGS. 22 and 23. Theguidewire120 and theobturator122 are then removed from thecannula28.
• After ensuring that all of thethumbscrews54 and74 are secure and that the alignment of theaxis170 is correct, the burring bit150 (FIG. 23) is inserted into thecannula28. The burringbit150 is rotated by a drill (not shown) to burr the opposingsurfaces172 and174 of the inferior articular process and the superior articular process on thefirst side104 of the L4 and L5 vertebrae, respectively. Burring thesesurfaces172 and174 widens the facet joint100 so that a bone graft material is more easily placed into the facet joint. It is contemplated that thecannula28 may be moved slightly along the facet joint100 during the burring process in order to access a larger area of the facet joint with the burringbit150. It should be noted that care must be taken to burr around, but not contact, thefirst screw84 that was previously implanted across the facet joint100 on thefirst side104 of the vertebrae.
• After thearticular surfaces172 and174 of the facet joint100 on thefirst side104 of the vertebrae have been burred out around thefirst screw84, bone graft (or bone substitute) material160 (FIG. 24) for helping to fuse the L4 and L5 vertebrae is placed into the facet joint100 through thecannula28. Thebone graft material160 may be fed into the facet joint using any known suitable instrument(s). Thecannula28 is then removed from the incision on thefirst side104 of the vertebrae and the first and second K-wires12 and14 are removed from the L5 and L4 vertebrae, respectively. The incisions are then closed. As shown in the completed view ofFIG. 24, with the twoscrews84 implanted across the facet joints100 and142 and thebone graft material160 placed into both of the facet joints, fusion of the L4 and L5 vertebrae will take place over the next few months.
• It should be understood to those skilled in the art that theapparatus10 could be used to implant screws for a variety using a transarticular (rather than translaminar) approach directly across the facet joints. Such an application could be accomplished by simply varying the placement of the K-wires12 and14 to achieve the necessary screw trajectories. It is contemplated that the implantation of transarticular screws may be best accomplished by inserting the first K-wire12 into the lamina a few millimeters lateral of the spinous process rather than into the spinous process itself. It should be noted that theswivel block assembly22 could be positioned between the fixation blocks16 and18 along therod member20 to aid with placement of direct (or transarticular) facet screws.
• The present invention described herein thus provides an apparatus and a minimally invasive method for placing screws either directly across the facet joints of adjacent vertebrae or indirectly across the facet joints through the lamina (i.e. translaminar) as both a primary means for spinal fixation and as a secondary means for fixation to augment anterior fusion or pedicle screw fixation instrumentation. It is contemplated that the apparatus could also be used to guide implantation for a variety of other orthopedic screws in the spine as well as other bones. Significantly, the present invention provides for the accurate and repeatable placement of facet screws and for fusing adjacent vertebrae in a minimally invasive procedure that saves time during surgery and is less traumatic to the patient.
• From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.

Claims (33)

1. An apparatus for placing translaminar screws across a facet joint between adjacent first and second vertebrae in a minimally invasive surgical procedure, said apparatus comprising:

a first K-wire for inserting into the spinous process of the first vertebrae;

a second K-wire for inserting into a transverse process of the second vertebrae;

first and second fixation blocks having perpendicularly extending first and second passages, said first K-wire extending into said first passage in said first fixation block and said second K-wire extending into said first passage in said second fixation block;

a rod member extending through said second passage in said first fixation block and said second passage in said second fixation block;

a swivel block assembly comprising relatively movable first and second block members, said swivel block assembly including a third passage extending through said first block member and a fourth passage extending through said second block member, said rod member extending into said third passage; and

a cannula which extends into said fourth passage in said second block member and through which the translaminar screws are insertable for implantation across a facet joint between the first and second vertebrae.

2. The apparatus ofclaim 1 wherein said first and second K-wires include graduations for measuring axial length along said K-wires.

3. The apparatus ofclaim 1 wherein said rod member includes graduations for measuring axial length along said rod member.

4. The apparatus ofclaim 1 wherein said first fixation block includes a first securing means for securing said first K-wire to said first fixation block and a second securing means for securing said rod member to said first fixation block.

5. The apparatus ofclaim 4 wherein said second fixation block includes a first securing means for securing said second K-wire to said second fixation block and a second securing means for securing said second fixation block to said rod member.

6. The apparatus ofclaim 5 wherein said first and second securing means on said first fixation block and said first and second securing means on said second fixation block comprise threaded fasteners.

7. The apparatus ofclaim 1 wherein said second fixation block includes a first securing means for securing said second K-wire to said second fixation block and a second securing means for securing said second fixation block to said rod member.

8. The apparatus ofclaim 1 wherein said first block member includes securing means for securing said rod member to said first block member.

9. The apparatus ofclaim 8 wherein said second block member includes securing means for securing said cannula to said second block member.

10. The apparatus ofclaim 9 wherein said swivel block assembly includes securing means for securing said first and second block members in a desired angular position relative to each other.

11. The apparatus ofclaim 1 wherein said swivel block assembly includes securing means for securing said first and second block members in a desired angular position relative to each other.

12. The apparatus ofclaim 11 wherein said securing means on said first and second block members and said swivel block assembly comprises threaded fasteners.

13. The apparatus ofclaim 1 wherein said swivel block assembly includes positioning means for controllably adjusting the angular position of the first and second block members relative to each other.

14. The apparatus ofclaim 1 wherein said first and second passages in said first fixation block are offset from each other by a predetermined amount.

15. The apparatus ofclaim 14 wherein said first and second passages in said second fixation block are offset from each other by said predetermined amount.

16. A minimally invasive apparatus for placing screws across a facet joint between adjacent first and second vertebrae, said apparatus comprising:

a first K-wire for inserting into the spinous process of the first vertebrae;

a first fixation block removably connected to said first K-wire;

a second K-wire for inserting into a transverse process of the second vertebrae;

a second fixation block removably connected to said second K-wire;

a rod member removably connected to both of said first and second fixation blocks;

a swivel block assembly comprising relatively movable first and second block members, said rod member being removably connected to said first block member; and

a cannula extending from said second block member and through which the screws are insertable for implantation across the facet joint.

17. The apparatus ofclaim 16 wherein each of said first and second K-wires includes means for measuring axial length along said K-wires.

18. The apparatus ofclaim 16 wherein said rod member includes means for measuring axial length along said rod member.

19. The apparatus ofclaim 16 wherein said swivel block assembly includes positioning means for controllably adjusting the angular position of the first and second block members relative to each other.

20. A minimally invasive surgical method for placing screws through the lamina and across the facet joints between adjacent upper and lower vertebrae, said method comprising the steps of:

providing an apparatus comprising first and second K-wires, first and second fixation blocks, a swivel block having relatively movable first and second block members, a rod member extending between the fixation blocks and the first block member, and a cannula extending from the second block member;

inserting the first K-wire into the center of the spinous process of the upper vertebrae;

inserting the second K-wire into a transverse process on a first side of the lower vertebrae so that the second K-wire is parallel to the first K-wire in both the sagittal and coronal planes;

securing the first fixation block to the first K-wire arid the second fixation block to the second K-wire with the rod member extending across the K-wires;

calculating a desired axial position for the swivel block assembly along the rod member;

calculating a desired angle for the centerline of the cannula to extend from a second side of the vertebrae toward the facet joint on the first side along a first axis;

securing the second block member of the swivel block assembly relative to the first block member to achieve the desired angle for the first axis;

securing the swivel block assembly at the desired axial position along the rod member;

obtaining percutaneous access to the junction of the lamina and the spinous process on the second side of the upper vertebrae via the cannula;

inserting a first screw through the cannula; and

implanting the first screw along the first axis across the facet joint on the first side to attach the upper and lower vertebrae.

21. The method ofclaim 20 further comprising the steps of:

inserting a drill bit into the cannula prior to said step of inserting the first screw; and

drilling a pilot hole for the first screw through the lamina and the facet joint on the first side with the drill bit to a predetermined depth along the first axis.

22. The method ofclaim 20 further comprising the steps of:

removing the cannula from its position over the lamina on the second side of the upper vertebrae;

releasing the first and second block members to allow relative movement;

swiveling the second block member to aim the centerline of the cannula along a second axis toward the facet joint on the second side;

obtaining percutaneous access to the facet joint on the second side via the cannula; and

placing a bone graft material into the facet joint on the second side through the cannula to assist with fusion of the upper and lower vertebrae.

23. The method ofclaim 22 further comprising the steps of:

inserting a burring bit into the cannula prior to said step of placing a bone graft material; and

burring the articular surfaces of the facet joint on the second side to widen said facet joint for accepting the bone graft material.

24. The method ofclaim 20 further comprising the steps of:

removing the cannula from percutaneous insertion on the second side;

removing the second K-wire from the transverse process on the first side of the lower vertebrae;

inserting the second K-wire into the transverse process on the second side of the lower vertebrae so that the second K-wire is parallel to the first K-wire in both the sagittal and coronal planes;

securing the second fixation block to the second K-wire;

releasing the first fixation block from the first K-wire;

rotating the first fixation block with the rod member extending across the K-wires;

securing the first fixation block to the first K-wire;

calculating a desired axial position for the swivel block assembly along the rod member;

calculating a desired angle for the centerline of the cannula to extend from the first side of the vertebrae toward the facet joint on the second side along a third axis;

securing the second block member of the swivel block assembly relative to the first block member to achieve the desired angle;

securing the swivel block assembly at the desired axial position along the rod member;

obtaining percutaneous access to the junction of the lamina and the spinous process on the first side of the upper vertebrae via the cannula;

inserting a second screw through the cannula; and

implanting the second screw along the third axis across the facet joint on the second side to attach the upper and lower vertebrae.

25. The method ofclaim 24 further comprising the steps of:

inserting a drill bit into the cannula prior to said step of inserting the second screw; and

drilling a pilot hole for the second screw through the lamina and the facet joint on the second side with the drill bit to a predetermined depth along the third axis.

26. The method ofclaim 24 further comprising the steps of:

removing the cannula from its position over the lamina on the first side of the upper vertebrae;

releasing the first and second block members to allow relative movement;

swiveling the second block member to aim the centerline of the cannula along a fourth axis toward the facet joint on the first side previously secured with the first screw;

obtaining percutaneous access to the facet joint on the first side via the cannula; and

placing a bone graft material through the cannula into the facet joint on the first side around the previously implanted first screw to assist with fusion of the upper and lower vertebrae.

27. The method ofclaim 26 further comprising the steps of:

inserting a burring bit into the cannula prior to said step of placing a bone graft material; and

burring the articular surfaces of the facet joint on the first side to widen said facet joint around the first screw for accepting the bone graft material.

28. A minimally invasive surgical method for fusing adjacent upper and lower vertebrae, said method comprising the steps of:

providing an apparatus comprising first and second K-wires, first and second fixation blocks, a swivel block having relatively movable first and second block members, a rod member extending between the fixation blocks and the first block member, and a cannula extending from the second block member;

inserting the first K-wire into the center of the spinous process of the upper vertebrae;

inserting the second K-wire into the transverse process on a first side of the lower vertebrae;

securing the first fixation block to the first K-wire and the second fixation block to the second K-wire with the rod member extending across the K-wires;

securing the second block member of the swivel block assembly relative to the first block member to achieve a desired angle for a first axis along which a first screw will be implanted into the facet joint on the first side;

securing the swivel block assembly at a desired axial position on the rod member;

obtaining percutaneous access along the first axis to a second side of the upper vertebrae via the cannula;

inserting the first screw through the cannula; and

implanting the first screw along the first axis across the facet joint on the first side to attach the upper and lower vertebrae.

29. The method ofclaim 28 further comprising the steps of:

moving the cannula to aim the cannula toward the facet joint on the second side of the vertebrae along a second axis;

obtaining percutaneous access along the second axis to the facet joint on the second side via the cannula; and

placing a bone graft material into the facet joint on the second side through the cannula to assist with fusion of the upper and lower vertebrae.

30. The method ofclaim 28 further comprising the steps of:

inserting a burring bit into the cannula; and

burring the articular surfaces of the facet joint on the second side to widen the said facet joint for accepting a bone graft material.

31. The method ofclaim 28 further comprising the steps of:

removing the cannula from percutaneous insertion on the second side;

removing the second K-wire from the transverse process on the first side of the lower vertebrae;

inserting the second K-wire into the transverse process on the second side of the lower vertebrae;

securing the second fixation block to the second K-wire;

releasing the first fixation block from the first K-wire and rotating the first fixation block with the rod member extending across the K-wires;

securing the first fixation block to the first K-wire;

securing the second block member of the swivel block assembly relative to the first block member to achieve a desired angle for a third axis on which a second screw will be implanted into the facet joint on the second side;

securing the swivel block assembly at a desired axial position along the rod member;

obtaining percutaneous access to the first side of the upper vertebrae via the cannula;

inserting a second screw through the cannula; and

implanting the second screw along the third axis across the facet joint on the second side to attach the upper and lower vertebrae.

32. The method ofclaim 31 further comprising the steps of:

moving the cannula to aim the cannula along a fourth axis toward the facet joint on the first side previously secured with the first screw;

obtaining percutaneous access to the facet joint on the first side via the cannula; and

placing a bone graft material through the cannula and into the facet joint on the first side around the previously implanted first screw to assist with fusion of the upper and lower vertebrae.

33. The method ofclaim 31 further comprising the steps of:

inserting a burring bit into the cannula; and

burring the articular surfaces of the facet joint on the first side to widen said facet joint around the first screw for accepting a bone graft material.

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