WO2006038959A1

WO2006038959A1 - Minimally invasive method and apparatus for placing facet screws and fusing adjacent vertebrae

Info

Publication number: WO2006038959A1
Application number: PCT/US2005/026623
Authority: WO
Inventors: Isador H. Lieberman
Original assignee: The Cleveland Clinic Foundation
Priority date: 2004-09-29
Filing date: 2005-07-27
Publication date: 2006-04-13
Also published as: US7740635B2; US20060079908A1; EP1809185A1; US20060085010A1

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 (12) 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 (14) for inserting into a transverse process of the second vertebrae and a second fixation block (18) removably connected to the second K-wire. A rod member (20) is removably connected to both of the first and second fixation blocks. A swivel block assembly (22) includes relatively movable first and second block members. The rod member is removably connected to the first block member. A cannula (28) 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

MINIMALLY INVASIVE METHOD AND APPARATUS FOR PLACING FACET SCREWS AND FUSING ADJACENT VERTEBRAE

Related Application

This application claims priority from U.S. patent application Serial No. 10/952,650, filed on September 29, 2004. The subject matter of the above-listed patent application is incorporated herein by reference.

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 pedicle 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 repeatab Iy 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, hi 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. -A-

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 trie 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 trie 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 of Fig. 1; Fig. 2A is a perspective view of a component of the apparatus of Fig. 1;

Fig. 3 is a perspective view of another component of the apparatus of Fig. 1;

Fig. 4 is a perspective view of another component of the apparatus of Fig. 1; Fig. 4A is a perspective view of another component of the apparatus of

Fig. 1; Fig. 5 is an exploded perspective view of another component of the apparatus of Fig. 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 of Fig. 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 of Fig. 7; Fig. 9 is a schematic side view of Fig. 8;

Figs. 10-12 are views similar to Fig. 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 to Fig. 12 illustrating additional steps according to the inventive method;

Fig. 16 is a view similar to Fig. 15 illustrating components of the apparatus of Fig. 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 of Fig. 16;

Fig. 18 is a schematic side view of the opposite side shown in Fig. 17;

Figs. 19-21 are views similar to Fig. 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 to Fig. 21 illustrating additional steps; and

Fig. 25 is a view similar to Fig. 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 an apparatus 10 comprising first and second Kirschner wires 12 and 14 (commonly referred to as "K- wires"), first and second fixation blocks 16 and 18, a rod member 20, a swivel block assembly Z2 comprising first and second block members 24 and 26, and a cannula Z 8.

As may be seen in Fig. 3, the rod member 20 is a cylindrical component that may be hollow or solid and is made from any suitable metal or plastic. The rod member 20 has oppositely disposed first and second ends 30 and 32 and an outer diameter of 4 to 7 mm. The rod member 20 includes an outer surface 34 with graduations for measuring axial distances along its length. It is contemplated that other means for measuring axial length along the rod member 20 could also be used.

The first and second K- wires 12 and 14 (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- wires 12 and 14 is an elongate rod made of a biocompatible metal or other suitable material with an outer diameter of 2 to 4 mm. As shown in Figs. 2 and 2A, each K-wire 12 and 14 has oppositely disposed distal and proximal ends 40 and 42 and a cylindrical outer surface 44 extending between the ends. The distal end 40 of each of the K-wires 12 and 14 includes self-tapping threads 46. The cylindrical outer surface 44 of each of the K-wires 12 and 14 includes graduations for measuring axial lengths along each K-wire. It is contemplated that other means for measuring axial length along the K-Λvires 12 and 14 could also be used.

The first and second fixation blocks 16 and 18 (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 blocks 16 and 18 is a generally rectangular part made of any suitable metal or plastic. The first fixation block 16 (Fig. 4) includes perpendicularly extending first and second passages 50 and 52. As shown in Fig. 3, the first and second passages 50 and 52 are offset from each other by a predetermined amount and thus do not intersect. In the assembled condition of Fig. 1, the first K-wire 12 extends into the first passage 50 in the first fixation block 16 and the rod member 20 extends into the second passage 52. The first fixation block 16 further includes threaded fasteners in the form of thumbscrews 54 that extend into the first and second passages 50 and 52 for securing the first K-wire 12 and the rod member 20 in the first and second passages, respectively. It should be understood, however, that other suitable means for securing the first K-wire 12 and the rod member 20 to the first fixation block 16, 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 the first fixation block 16, the second fixation block 18 includes perpendicularly extending first and second passages 56 and 58 that are offset from each other by a predetermined amount and thus do not intersect. The predetermined amount of offset between the first and second passages 56 and 58 in the second fixation block 18 is the same as the predetermined amount of offset between the first and second passages 50 and 52 in the first fixation block 16. In the assembled condition of Fig. 1, the second

K-wire 14 extends into the first passage 56 in the second fixation block 18 and the rod member 20 extends into the second passage 58.

The second fixation block 18 further includes threaded fasteners in the form of thumbscrews 54 that extend into the first and second passages 56 and 58 for securing the second K-wire 14 and the rod member 20 in the first and second passages 56 and 58, respectively. It should be understood, however, that other suitable means for securing the second K-wire 14 and the rod member 20 to the second fixation block 18, 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 in Fig. 4, the first and second block members 24 and 26 of the swivel block assembly 22 are movable relative to each other about an axis 60. Each of the first and second block members 24 and 26 is a generally rectangular part made of any suitable metal or plastic. The first block member 24 includes a passage 62 for receiving the rod member 20. A threaded fastener in the form of a thumbscrew 54 extends into the passage 62 for securing the rod member 20 in the passage. The second block member 26 further includes a passage 64 for receiving the cannula 28. A threaded fastener in the form of a thumbscrew 54 extends into the passage 64 for securing the cannula 28 in the passage. It should be understood, however, that other suitable means for securing the rod member 20 and the cannula 28 to the swivel block assembly 22, 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 and second block members 24 and 26 further include abutting surfaces 66 and 68, respectively, with means for controllably adjusting the angular position of the block members relative to each other, hi accordance with the illustrated embodiment of the invention, this is accomplished via a first ring of radially extending serrations 70 on the surface 66 of the first block member 24 that is centered on the axis 60 and engaged with a second ring of radially extending serrations 72 on the surface 68 of the second block member 26 that is also centered on the axis 60. A threaded fastener in the form of a thumbscrew 74 extends through the first block member 24 and into a threaded opening 76 in the second block member 26 along the axis 60 for securing the block members in a desired relative angular position. It should be understood, however, that other suitable means for securing the block members 24 and 26 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 and second block members 24 and 26 could be employed.

The cannula 28 (Fig. 1) is a thin-walled hollow cylinder made of a biocompatible metal or other suitable material and has oppositely disposed distal and proximal ends 80 and 82. In accordance with one embodiment of the present invention, the cannula 28 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 a screw 84 to be implanted in accordance with the present invention. The screw 84 is a self-tapping facet screw made of a biocompatible material, such as titanium. As illustrated in Fig. 6, the screw 84 has a head 86 with a triangular-shaped receptacle 88. 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 the screw 84 is determined during surgery as discussed below.

To use the apparatus 10 to place the facet screw 84 across a first facet joint 100 between adjacent vertebrae, such as the L4 and L5 vertebrae shown in Figs. 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- wire 12 is inserted through the incision and into the center of the spinous process of the L4 vertebrae. As may be seen in Figs. 7 and 9, the distal end 40 of the first K- wire 12 is screwed into the spinous process until the distal tip reaches a point along a first axis 102 on which a first screw 84 is to be inserted.

Next, through another percutaneous stab incision, the second K- wire 14 is inserted into the transverse process on a first side 104 (the left side as viewed in Fig. 7) of the L5 vertebrae and extends in parallel with the first K- wire 12 in both the sagittal and coronal planes as shown in Figs. 7-9. The distal end 40 of the second K- wire 12 is screwed into the transverse process just lateral to the facet joint 100 on the first side 104 of the vertebrae up to the junction of the transverse process and the pedicle on the first side. The first fixation block 16 is then slid onto the first K- wire 12 with the first

K-wire extending into the first passage 50 in the first fixation block. Similarly, the second fixation block 18 is slid onto the second K-wire 14 with the second K-wire extending into the first passage 56 in the second fixation block. The first end 30 of the rod member 20 is slid then into the second passages 52 and 58 in the first and second fixation blocks 16 and 18, respectively, so that it extends across the first and second K-wires 12 and 14. The thumbscrews 54 that extend into the second passages 52 and 58 are tightened to secure the rod member 20 to the fixation blocks 16 and 18.

According to the inventive method, the next steps involve calculations to determine the following three parameters: (1) the length L₁ of the screw 84 to be implanted; (2) the desired angle Ai for the cannula 28 to extend from the swivel block assembly 22, which provides the trajectory for the implantation of a first screw 84 across the facet joint 100 on the first side 104; and (3) the desired axial position D₁ for the swivel block assembly 22 along the rod member 20. As will be seen in the calculations set forth below, the apparatus 10 according to the present invention utilizes the position and relationship of the first and second K- wires 12 and 14 to determine the entry point and trajectory upon which the screw 84 is implanted into the L4 and L5 vertebrae.

The screw length Li is determined by measuring the axial difference Xi between the two identical K- wires 12 and 14 and measuring the horizontal difference Yi between the two K-wires. The graduations on the K-wires 12 and 14 and/or another suitable means can assist in taking these measurements. The screw length Li is calculated with the following equation: L₁ = V (X₁ ² + Y₁ ²). Use of this equation to determine the desired screw length L₁ helps to ensure that the screw 84, when implanted across the facet joint 100, will not extend beyond the cortex of the superior articular process where nerve damage could become an issue.

The desired angle Ai for the cannula 28 to extend from the swivel block assembly 22, which provides the trajectory for the implantation of the first screw 84 across the facet joint 100 on the first side 104, is calculated based on the measured X and Y values and the angle between these distances using the following equation: Ai = tan^"1 (Yi/Xi). As shown in Fig. 5, the calculated angle Ai between the proximal ends 42 of the K-wires 12 and 14 also defines the angle (Ai) between the centerline of the rod member 20 and the centerline 108 of the second passage 64 through the second block member 26. The centerline 106 of the passage 64 is also the centerline of the cannula 28 and is co-linear with the screw trajectory axis 102, as may be seen in Fig. 7. The second block member 26 is then rotated about the axis 60 relative to the first block member 24 to set the desired angle Ai for the centerline 106 of the cannula 28, which extends from the second block member. At the desired angle A₁, the first and second rings of serrations 70 and 72 on the first and second block members 24 and 26, respectively, are brought into engagement and secured by the thumbscrew 74 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 A₁ could also be used in conjunction with the distances X₁ and Y₁ between the K- wires 12 and 14.

The axial position, or distance, D₁ for the swivel block assembly 22 on the rod member 20 is calculated by first measuring the distance Zi of penetration of the first K-wire 12 (i.e., the distance Zi extends between the distal tip of the first

K- wire and the skin 108) using the graduations on the first K-wire. The distance Di is then calculated with the following equation: Di = (X₁ATi) Zi. The distance D₁ for the swivel block assembly 22 along the rod member 20 is measured from the centerline of the first K-wire 12 to the axis 60 of the swivel block assembly. The graduations on the rod member 20 or another suitable means can be used for setting the swivel block assembly 22 at the desired axial position.

Next, the swivel block assembly 22 is slid onto the second end 32 of the rod member 20, which is projecting out over a second side 110 (or right side as viewed in Fig. 7) of the L4 and L5 vertebrae, with the rod member 20 extending through the passage 62 in the first block member 24. The thumbscrew 54 is used to secure the swivel block assembly 22 at the calculated desired axial position Di on the rod member 20.

The rod member 20 and the swivel block assembly 22 are then lowered to a height above the skin 108 that provides sufficient clearance for the swivel block assembly as shown in Fig. 7. Finally, the first and second fixation blocks 16 and 18 are secured to the first and the second K- wires 12 and 14, respectively, with the thumbscrews 54. The apparatus 10 is now in position for the first screw 84 to be placed across the facet joint 100 on the first side 104 of the L4 and L5 vertebrae. A scalpel (not shown) is used to incise the skin 108 on the second side 110 of the vertebrae to accept the cannula 28. With the cannula 28 temporarily removed, the incision is made using the passage 64 through the second block member 24 of the swivel block assembly 22 to orient the incision along the proper axes 102 and 106. Under fluoroscopic guidance, a guidewire 120 is passed through the incision along the axes 102 and 106 to the starting point for the screw 84 which is located adjacent the junction of the spinous process and the lamina as shown in Fig. 7. It is contemplated that a Jamshidi needle or other suitable instrument could be used in place of the guidewire 120.

Next, a blunt obturator 122 is passed over the guidewire 120 to create subcutaneous space for the cannula 28 along the axis 102. The cannula 28, which is guided for movement along the axes 102 and 106 by virtue of the passage 64 through the second block member 26, is then passed over the obturator 122 and the guidewire 120. The cannula 28 is moved along the axes 102 and 106 until the distal end of the cannula docks against the lamina on the second side 110 of the L4 vertebrae as shown in Figs. 8 and 9. The guidewire 120 and the obturator 122 are then removed from the cannula 28. At this point in the procedure, a small (e.g., 2 mm) diameter scope may be passed down the cannula 28 to inspect the anatomy and the condition of the vertebrae.

After ensuring that all of the thumbscrews 54 and 74 are secure and that the alignment of the axis 102 is correct, a drill bit 130 (Fig. 10) is inserted into the cannula 28. The drill bit 130 is rotated by a drill (not shown) to drill a pilot hole 132 along the axis 102 through the lamina on the second side 110 of the L4 vertebrae, through the inferior articular process on the first side 104 of the L4 vertebrae, across the facet joint 100 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 the drill bit 130 in the cannula 28 and ensure that the pilot hole 132 extends along the axis 102.

As shown in Fig. 11, the self-tapping screw 84 is then inserted into the cannula 28 and screwed into the pilot hole 132 using a driver 134. In the illustrated embodiment, the head 86 of the screw 84 has a maximum outer diameter that matches the inner diameter of a second cannula 136 that is inserted into the cannula 28 to aid in keeping the screw aligned on the axis 102 during implantation.

Further, the illustrated driver 134 has a triangular tip for receipt in the receptacle 88 of the screw 84, although it should be understood that the receptacle and the corresponding driver tip could utilize a different geometry. The screw 84 is advanced until the head 86 seats against the lamina on the second side 110 of the L4 vertebrae. Fluoroscopic guidance coupled with the aforementioned calculation to select the length L₁ of the screw 84 ensures that the distal tip of the screw does not penetrate beyond the cortex of the L5 vertebrae. As implanted, the screw 84 extends across the facet joint 100 to connect the inferior articular process of trie L4 vertebrae to the superior articular process of the L5 vertebrae.

With the first screw 84 implanted, the cannula 28 is removed from the skin 108 and the thumbscrew 74 is released to allow relative movement of the first and second block members 24 and 26. The second block member 26 is then swiveled to aim the centerline 106 of the cannula 28 along a second axis 140 (Fig. 13) that extends toward a facet joint 142 (Fig. 12) on the second side 110 of the vertebrae. In order to aim the cannula 28 toward the facet joint 142, the other thumbscrews 54 may also be released to allow additional movement of the swivel block assembly 22. Releasing the other thumbscrews 22 may allow the cannula 28 to be positioned over the existing incision through the skin 108 while being aimed toward the facet joint 142 along the axis 140 so that the same incision can be utilized again.

After tightening all of the thumbscrews 54 and 74 to secure the components of th.e apparatus 10 in the positions shown in Fig. 12, the guidewire 120 (or

Jamshidi needle, etc.) is passed through the incision along the axis 140 to the surface of the facet joint 142 on the second side 110 of the L4 and L5 vertebrae under fluoroscopic guidance. Next, the blunt obturator 122 is passed over the guidewire 120 to create subcutaneous space for the cannula 28 along the axis 140. The cannula 28, which is guided for movement along the axes 140 and 106 by virtue of the passage 64 through the second block member 26, is then passed over the obturator 122 and the guidewire 120. The cannula 28 is moved along the axes 140 and 106 until the distal end of the cannula 28 docks against the surface of the facet joint 142 as shown in Figs. 13 and 14. The guidewire 120 and the obturator 122 are then removed from the cannula 28.

After ensuring that all of the thumbscrews 54 and 74 are secure and that the alignment of the axis 140 is correct, a burring bit 150 (Fig. 14) is inserted into the cannula. The burring bit 150 is rotated by a drill (not shown) to burr the opposing surfaces 152 and 154 of the inferior articular process and the superior articular process on the second side 110 of the L4 and L5 vertebrae, respectively. Burring these surfaces 152 and 154 widens the facet joint so that a bone graft material is more easily placed into the facet joint 142. It is contemplated that the cannula 28 may be moved slightly along the facet joint 142 during the burring process in order to access a larger area of the facet joint with the burring bit 150.

After the articular surfaces 152 and 154 of the facet joint 142 on the second side 110 of the L4 and L5 vertebrae have been burred out, a bone graft (or bone substitute) material 160 (Fig. 15) for helping to fuse the L4 and L5 vertebrae is placed into the facet joint 142 through the cannula 28. The bone graft material 160 may be fed into the facet joint 142 using any known suitable instrument(s). The cannula 28 is then removed from the incision on the second side 110 of the vertebrae. The next steps in the process are to loosen all of the thumbscrews 54 and 74, remove the fixation blocks 16 and 18 from the K- wires 12 and 14, and disassemble the swivel block assembly 22 from the rod member 20. The second K- wire 14 is then removed from the transverse process on the first side 104 of the L5 vertebrae. Next, through another percutaneous stab incision, the second K- wire 14 is inserted into the transverse process on the second side 110 of the L5 vertebrae so that it again extends in parallel with the first K- wire 12 in both the sagittal and coronal planes as shown in Figs. 16-18. The distal end 40 of the second K- wire 14 is screwed into the transverse process just lateral to the facet joint 142 on the second side 110 of the vertebrae up to the junction of the transverse process and the pedicle.

The first fixation block 16 is then slid onto the first K- wire 12 with the first K-wire extending into the first passage 50 in the first fixation block. Similarly, the second fixation block 18 is slid onto the second K-wire 14 with the second K-wire extending into the first passage 56 in the second fixation block. The first end 30 of the rod member 20 is slid then into the second passages 52 and 58 in the first and second fixation blocks 16 and 18, respectively, so that it extends across the first and second K- wires 12 and 14. The thumbscrews 54 that extend into the second passages 52 and 58 are tightened to secure the rod member 20 to the fixation blocks 16 and 18.

Once again, the next steps in the process involve calculations to determine the following three parameters: (1) the length L₂ of a second screw 84 to be implanted; (2) the desired angle A₂ for the cannula 28 to extend from the swivel block assembly, which provides a traj ectory axis 162 for the implantation of the second screw 84 across the facet joint 142 on the second side 110; and (3) the desired axial position D₂ for the swivel block assembly 22 along the rod member 20. As mentioned above, the apparatus 10 according to the present invention utilizes the position and relationship of the first and second K- wires 12 and 14 to determine the entry point and trajectory upon which the second screw 84 is implanted into the L4 and L5 vertebrae.

The screw length L₂ is determined by measuring the axial difference X₂ between the two identical K- wires 12 and 14 and measuring the horizontal difference Y₂ between the two K-wires. The graduations on the K-wires 12 and 14 or another suitable means can assist in taking these measurements. The screw length L₂ is then calculated with the following equation: L₂ = V (X₂ ² + Y₂ ²). Use of this equation to determine the desired screw length L₂ helps to ensure that the second screw 84, when implanted across the facet joint 142, 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 and second screws 84 will likely be the same.

The desired angle A₂ for the cannula 28 to extend from the swivel block assembly 22, which provides the trajectory for the implantation of the second screw 84 across the facet joint 142 on the second side 110, is calculated with the following equation: A₂ = tan^'1 (Y₂/X₂). As shown in Fig. 16, the calculated desired angle A₂ between the proximal ends 42 of the K-wires 12 and 14 also defines the angle (A₂) between the centerline of the rod member 20 and the centerline 106 of the second passage 64 through the second block member 26. The centerline of the passage 64 is also the centerline of the cannula 162, as may be seen in Fig. 16. The second block member 26 is then rotated about the axis 60 relative to the first block member 24 to set the desired angle A₂ for the centerline 106 of the cannula 28, which extends from the second block member. At the desired angle A₂, the first and second rings of serrations 70 and 72 on the first and second block members 24 and 26, respectively are brought into engagement and secured by the thumbscrew 74 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 A₂ could also be used in conjunction with the distances X₂ and Y₂ between the K-wires 12 and 14.

The axial position, or distance, D₂ for the swivel block assembly 22 on the rod member 20 is calculated by first measuring the distance Z₂ of penetration of the first K-wire 12 (i.e., the distance Z₂ extends between the distal tip of the first

K- wire and the skin 108) using the graduations on the first K-wire. The distance D₂ is then calculated with the following equation: D₂ = (X₂/ Y₂) Z₂. The distance D₂ for the swivel block assembly 22 along the rod member 20 is measured from the centerline of the first K-wire 12 to the axis 60 of the swivel block assembly 22. The graduations on the rod member 20 or another suitable means can be used for setting the swivel block assembly 22 at the desired axial position.

Next, the swivel block assembly 22 is then slid onto the second end 32 of the rod member 20, which is projecting out over the first side 104 of the vertebrae, with the rod member extending through the passage 62 in the first block member 24. The thumbscrew 54 is used to secure the SΛvivel block assembly 22 at the calculated desired axial position D₂ on the rod member 20.

The rod member 20 and the swivel block assembly 22 are then lowered to a height above the skin 108 that provides sufficient clearance for the swivel block assembly as shown in Fig. 16. Finally, the first and second fixation blocks 16 and 18 are secured to the first and second K-wires 12 and 14, respectively, with the thumbscrews. The apparatus 10 is now in position for the second screw 84 to be placed across the facet joint 142 on the second side 110 of the vertebrae. It is important to note at this point that the predetermined ofϊfset between the first and second passages 50 and 52 in the first fixation blocks 16 and the first and second passages 56 and 58 in the second fixation block 18 positions the rod member 20 and the swivel block assembly 22 so that the axis 162 for implantation of the second screw 84 is offset from the axis 102 on which trie first screw 84 was implanted. This offset ensures that the second screw 84 does not intersect with the first screw 84 as it extends through the spinous process of the L4 vertebrae.

The scalpel (not shown) is used to incise the skin 108 on the first side 104 of the vertebrae to accept the cannula 28. With the cannula 28 temporarily removed, the incision is made using the passage 64 through the second block member 24 of the swivel block assembly 22 to orient the incision on the axes 106 and 162. Under fluoroscopic guidance, the guidewire 120 is passed through the incision along the axes 106 and 162 to the starting point for the screw 84 which is located adjacent the junction of the spinous process and the lamina as shown in Fig. 16. As discussed above, it is contemplated that a Jamshidi needle or other suitable instrument could be used in place of the guidewire 120.

Next, the blunt obturator 122 is passed over the guidewire 120 to create subcutaneous space for the cannula 28 along the axis 162. The cannula Z8, which is guided for movement along the axes 106 and 162 by virtue of the passage 64 through the second block member 26, is then passed over the obturator 122 and the guidewire 120. The cannula 28 is moved along the axes 106 and 162 until the distal end of the cannula docks against the lamina on the first side 104 of^" the L4 vertebrae as shown in Figs. 17 and 18. The guidewire 120 and the obturator 122 are then removed from the cannula 28. At this point in the procedure, the small diameter scope may again be passed down the cannula 28 to inspect the anatomy and the condition of the vertebrae.

After ensuring that all of the thumbscrews 54 and 74 are secure and that the alignment of the axis 162 is correct, the drill bit (Fig. 19) is inserted into the cannula 28. The drill bit 130 is rotated by a drill (not shown) to drill a pilot hole 132 along the axis 162 through the lamina on the first side 104 of tke L4 vertebrae, through the inferior articular process on the second side 110 of the L4 vertebrae, across the facet joint 142 and the bone graft material 160 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 the drill bit 130 in the cannula 28 and ensure that the pilot hole 132 extends along the axis 162.

As shown in Fig. 20, the self-tapping second screw 84 is then inserted into the cannula 28 and screwed into the pilot hole 132 using the driver 134. In the illustrated embodiment, the head 86 of the screw 84 has a maximum outer diameter that matches the inner diameter of the second cannula 136 to aid in keeping the screw aligned on the axis 162 during implantation. Further, the illustrated screw head 86 has a triangular receptacle for receiving the triangular tip on the driver 134, although it should be understood that the receptacle and the corresponding driver tip could utilize a different geometry. The screw 84 is advanced until the head 86 seats against the lamina on the first side 104 of the L4 vertebrae. Fluoroscopic guidance coupled with the aforementioned calculation to select the length L₂ of the screw ensures that the distal tip of the screw does not penetrate beyond the cortex of the L5 vertebrae. As implanted, the second screw 84 extends across the facet joint 142 and the bone graft material 160 in the facet joint connect the inferior articular process of the L4 vertebrae to the superior articular process of the L5 vertebrae.

With the second screw 84 implanted, the cannula 28 is removed from the skin 108 and the thumbscrew 74 is released to allow relative movement of the first and second block members 24 and 26. The second block member 26 is then swiveled to aim the centerline 106 of the cannula 28 along a fourth axis 170 (Fig. 22) that extends toward the facet joint 100 on the first side 104 of the vertebrae. In order to aim the cannula 28 toward the facet joint 100, the other thumbscrews 54 may also be released to allow additional movement of the swivel block assembly 22. Releasing the other thumbscrews 54 may allow the cannula to be positioned over the existing incision while being aimed toward the facet joint 100 along the axis 170 so that the same incision can be utilized again.

After tightening all of the thumbscrews 54 and 74 to secure the components of the apparatus 10 in the positions shown in Fig. 21, the guidewire 120 (or

Jamshidi needle, etc.) is passed through the incision along the axis 170 to the surface of the facet joint 100 on the first side 104 of the vertebrae under fluoroscopic guidance. Next, the blunt obturator 122 is passed over the guidewire 120 to create subcutaneous space for the cannula 28 along the axis 170. The cannula 28, which is guided for movement along the axes 106 and 170 by virtue of the passage 64 through the second block member 26, is then passed over the obturator 122 and the guidewire 120. The cannula 28 is moved along the axes 106 and 170 until the distal end of the cannula docks against the surface of the facet joint 100 as shown in Figs. 22 and 23. The guidewire 120 and the obturator 122 are then removed from the cannula 28.

After ensuring that all of the thumbscrews 54 and 74 are secure and that the alignment of the axis 170 is correct, the burring bit 150 (Fig. 23) is inserted into the cannula 28. The burring bit 150 is rotated by a drill (not shown) to burr the opposing surfaces 172 and 174 of the inferior articular process and the superior articular process on the first side 104 of the L4 and L5 vertebrae, respectively. Burring these surfaces 172 and 174 widens the facet joint 100 so that a bone graft material is more easily placed into the facet joint. It is contemplated that the cannula 28 may be moved slightly along the facet joint 100 during the burring process in order to access a larger area of the facet joint with the burring bit 150. It should be noted that care must be taken to burr around, but not contact, the first screw 84 that was previously implanted across the facet joint 100 on the first side 104 of the vertebrae.

After the articular surfaces 172 and 174 of the facet joint 100 on the first side 104 of the vertebrae have been burred out around the first screw 84, bone graft (or bone substitute) material 160 (Fig. 24) for helping to fuse the L4 and L5 vertebrae is placed into the facet joint 100 through the cannula 28. The bone graft material 160 may be fed into the facet joint using any known suitable instrument(s). The cannula 28 is then removed from the incision on the first side 104 of the vertebrae and the first and second K- wires 12 and 14 are removed from the L5 and L4 vertebrae, respectively. The incisions are then closed. As shown in the completed view of Fig. 24, with the two screws 84 implanted across the facet joints 100 and 142 and the bone graft material 160 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 the apparatus 10 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- wires 12 and 14 to achieve the necessary screw trajectories. It is contemplated that the implantation of transarticular screws may be best accomplished by inserting the first K-wire 12 into the lamina a few millimeters lateral of the spinous process rather than into the spinous process itself. It should be noted that the swivel block assembly 22 could be positioned between the fixation blocks 16 and 18 along the rod member 20 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

Having described the invention, I claim:

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 of claim 1 wherein said first and second K-wires include graduations for measuring axial length along said K-wires.

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

4. The apparatus of claim 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 of claim 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 of claim 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 of claim 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 of claim 1 wherein said first block member includes securing means for securing said rod member to said first block member.

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

10. The apparatus of claim 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 of claim 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 of claim 11 wherein said securing means on said first and second block members and said swivel block assembly comprises threaded fasteners.

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

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

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

19. The apparatus of claim 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 and 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 of claim 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 of claim 20 further comprising the steps of: removing trie 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 trie 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 of claim 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 of claim 20 further comprising the steps of: removing trie 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-Λvire 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 of claim 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 of claim 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 of claim 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 expending 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 of claim 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 of claim 28 further comprising the steps of: inserting a burring bit into ttαe 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 of claim 28 furtlier 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 thie 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 tlie 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 of claim 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 throxigh 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 of claim 31 further comprising the steps of: inserting a burring bit into the cannula; and burring the articular surfaces of tne facet joint on the first side to widen said facet joint around the first screw for accepting a bone graft material.