Method and apparatus for providing posterior or anterior trans-sacral access to spinal vertebrae

• US 20030229353A1
• Filed: 06/10/2003
• Published: 12/11/2003
• Est. Priority Date: 02/16/2000
• Status: Active Grant

• Current Assignee: Mis Ip Holdings LLC
• Original Assignee: TranS1 Incorporated (Baxano Surgical, Inc.)
• Inventors: Cragg, Andrew H.
• Granted Patent: US 7,087,058 B2
• Time in Patent Office: Days
• US Class Current: 606/86
• CPC Class Codes: A61B 17/1671 for the spine
• CPC Class Codes: A61B 17/1757 for the spine
• CPC Class Codes: A61B 17/32002 with continuously rotating, oscillating or reciprocating cutting instruments
• CPC Class Codes: A61B 17/320725 with radially expandable cutting or abrading elements A61B17/32075 takes precedence
• CPC Class Codes: A61B 17/3421 Cannulas
• CPC Class Codes: A61B 17/3472 for bones, e.g. intraosseus injections
• CPC Class Codes: A61B 17/66 Alignment, compression or distraction mechanisms
• CPC Class Codes: A61B 17/70 Spinal positioners or stabilisers ; Bone stabilisers comprising fluid filler in an implant
• CPC Class Codes: A61B 17/7055 connected to sacrum, pelvis or skull
• CPC Class Codes: A61B 17/8805 for introducing fluid filler into bone or extracting it A61B17/7097, A61B17/8833 take precedence
• CPC Class Codes: A61B 2017/00261 Discectomy
• CPC Class Codes: A61B 2017/00734 battery operated
• CPC Class Codes: A61B 2017/00867 shape memory effect for prostheses A61F2210/0014
• CPC Class Codes: A61B 2017/2905 flexible
• CPC Class Codes: A61B 2017/320048 Balloon dissectors
• CPC Class Codes: A61B 2017/320064 with tissue or sample retaining means
• CPC Class Codes: A61B 2017/320733 with a flexible cutting or scraping element, e.g. with a whip-like distal filament member
• CPC Class Codes: A61B 2017/349 Trocar with thread on outside
• CPC Class Codes: A61F 2/441 made of inflatable pockets or chambers filled with fluid, e.g. with hydrogel
• CPC Class Codes: A61F 2/442 Intervertebral or spinal discs, e.g. resilient non-disc-shaped intervertebral inflatable pockets A61F2/441; non-disc-shaped intervertebral fusion implants A61F2/4455
• CPC Class Codes: A61F 2/4455 : for the fusion of spinal bodies, e.g. intervertebral fusion of adjacent spinal bodies, e.g. fusion cages intervertebral discs A61F2/442
• CPC Class Codes: A61F 2/4465 : having a circular or kidney shaped cross-section substantially perpendicular to the axis of the spine
• CPC Class Codes: A61F 2/4601 : for introducing bone substitute, for implanting bone graft implants or for compacting them in the bone cavity
• CPC Class Codes: A61F 2/4611 : of spinal prostheses
• CPC Class Codes: A61F 2002/2821 : Bone stimulation by electromagnetic fields or electric current for enhancing ossification
• CPC Class Codes: A61F 2002/2835 : Bone graft implants for filling a bony defect or an endoprosthesis cavity, e.g. by synthetic material or biological material
• CPC Class Codes: A61F 2002/30092 : using shape memory or superelastic materials, e.g. nitinol
• CPC Class Codes: A61F 2002/30291 : spirally-coiled, i.e. having a 2D spiral cross-section
• CPC Class Codes: A61F 2002/3055 : for adjusting length
• CPC Class Codes: A61F 2002/30563 : having elastic means or damping means, different from springs, e.g. including an elastomeric core or shock absorbers
• CPC Class Codes: A61F 2002/30566 : Helical springs
• CPC Class Codes: A61F 2002/30593 : hollow
• CPC Class Codes: A61F 2002/30677 : Means for introducing or releasing pharmaceutical products, e.g. antibiotics, into the body
• CPC Class Codes: A61F 2002/30774 : internally-threaded
• CPC Class Codes: A61F 2002/30841 : Sharp anchoring protrusions for impaction into the bone, e.g. sharp pins, spikes
• CPC Class Codes: A61F 2002/3085 : with a threaded, e.g. self-tapping, bone-engaging surface, e.g. external surface
• CPC Class Codes: A61F 2002/30879 : Ribs
• CPC Class Codes: A61F 2002/30884 : Fins or wings, e.g. longitudinal wings for preventing rotation within the bone cavity
• CPC Class Codes: A61F 2002/30892 : parallel
• CPC Class Codes: A61F 2002/30925 : etched
• CPC Class Codes: A61F 2002/3097 : using laser
• CPC Class Codes: A61F 2002/448 : comprising multiple adjacent spinal implants within the same intervertebral space or within the same vertebra, e.g. comprising two adjacent spinal implants
• CPC Class Codes: A61F 2002/4627 : with linear motion along or rotating motion about the instrument axis or the implantation direction, e.g. telescopic, along a guiding rod, screwing inside the instrument
• CPC Class Codes: A61F 2210/0014 : using shape memory or superelastic materials, e.g. nitinol
• CPC Class Codes: A61F 2230/0091 : helically-coiled or spirally-coiled, i.e. having a 2-D spiral cross-section
• CPC Class Codes: A61F 2310/00353 : Bone cement, e.g. polymethylmethacrylate or PMMA
• CPC Class Codes: A61N 5/1027 : Interstitial radiation therapy
• CPC Class Codes: Y10S 606/90 : Lumbar stabilizer
• CPC Class Codes: Y10S 606/914 : Toolkit for installing or removing spinal positioner or stabilizer

Abstract

Methods and apparatus for providing percutaneous access to vertebrae in alignment with a visualized, trans-sacral axial instrumentation/fusion (TASIF) line in a minimally invasive, low trauma, manner are disclosed. A number of related TASIF methods and surgical tool sets are provided by the present invention that are employed to form a percutaneous pathway from an anterior or posterior skin incision to a respective anterior or posterior target point of a sacral surface. The percutaneous pathway is generally axially aligned with an anterior or posterior axial instrumentation/fusion line extending from the respective anterior or posterior target point through at least one sacral vertebral body and one or more lumbar vertebral bodies in the cephalad direction. The provision of the percutaneous pathway described herein allows for the formation of the anterior or posterior TASIF bore(s) and/or the introduction of spinal implants and instruments.

Claims

1. A method of providing access for introduction of instruments to a series of adjacent vertebrae located within a human lumbar and sacral spine having an anterior aspect, a posterior aspect and an axial aspect, the vertebrae separated by intact or damaged spinal discs, the method comprising:

from a skin incision, accessing an anterior or posterior sacral position of a sacral vertebra that is aligned with a visualized, trans-sacral axial fusion/instrumentation line extending in said axial aspect through the series of adjacent vertebral bodies;

forming a percutaneous tract extending from the skin incision to an anterior or posterior sacral position of a sacral vertebra having a tract axis aligned with said visualized, trans-sacral axial instrumentation/fusion line providing axial guidance for said instruments introduced over or through said percutaneous tract to said anterior or posterior sacral position; and

positioning an instrumentation guide in the tract, to guide the instruments to the sacral position.

2. The method of claim 1, wherein said instruments comprise a boring tool, and further comprising:

from said accessed sacral position, boring a trans-sacral axial instrumentation/fusion bore through the sacrum and into at least one vertebrae and any intervertebral disc in alignment with said visualized, trans-sacral axial instrumentation/fusion line employing said boring tool advanced over or through said percutaneous tract to said anterior or posterior sacral position.

3. The method of claim 1, wherein the step of forming a percutaneous tract further comprises forming a posterior percutaneous tract to access the posterior presacral position of a sacral vertebra in alignment with a visualized, curved, posterior axial instrumentation/fusion line extending in said axial aspect initially laterally through the sacral vertebra and then following the curvature of the spine through a series of adjacent cephalad vertebral bodies.

4. The method of claim 3, wherein the step of forming a posterior percutaneous tract comprises:

providing a posterior tract sheath having a tract sheath axis and tract sheath lumen extending between tract sheath proximal and distal ends, the tract sheath distal end formed with a bone attachment mechanism;

advancing the tract sheath distal end to said posterior presacral position with said tract sheath axis aligned with a sacral end of said visualized, curved, posterior axial instrumentation/fusion line; and

attaching the bone attachment mechanism at the tract sheath distal end to sacral bone to align the tract sheath axis with the sacral end of said visualized, curved, posterior axial instrumentation/fusion line, whereby the posterior tract sheath extends through the skin incision and to the posterior presacral position.

5. The method of claim 3, wherein the accessing step further comprises:

drilling a pilot hole of a first diameter from a presacral penetration position along said axial instrumentation/fusion line within and axially through said series of vertebral bodies and intervening spinal discs to a cephalad pilot hole end within a vertebral body;

providing a guidewire having a guidewire proximal end and a guidewire distal end; and

extending the guidewire through said presacral space and through said pilot hole to locate the distal end of said guidewire at the cephalad pilot hole end.

6. The method of claim 5, wherein the guidewire distal end is fitted with a distal fixation mechanism, and the extending step further comprises:

attaching the distal fixation mechanism of the guidewire distal end to the vertebral body at the cephalad pilot hole end.

7. The method of claim 3, wherein the step of forming a posterior percutaneous tract comprises:

providing a guidewire having a guidewire proximal end and a guidewire distal end fitted with a distal fixation mechanism;

attaching the distal fixation mechanism of the guidewire distal end to the sacral bone at the sacral position; and

axially aligning the guidewire with the axial instrumentation/fusion line.

8. A method of providing access to a series of adjacent vertebrae located within a human lumbar and sacral spine having an anterior aspect, a posterior aspect and an axial aspect, the vertebrae separated by intact or damaged spinal discs, the method comprising:

from a skin incision, accessing an anterior or posterior sacral position of a sacral vertebra that is aligned with a visualized, trans-sacral axial fusion/instrumentation line extending in said axial aspect through the series of adjacent vertebral bodies;

forming an anterior, presacral, percutaneous tract through the patient'"'"'s presacral space to access an anterior presacral position of a sacral vertebra in alignment with a visualized, anterior axial instrumentation/fusion line extending in said axial aspect through the series of adjacent vertebral bodies; and

positioning a tubular sleeve in the tract.

9. The method of claim 8, wherein the accessing step further comprises:

making an incision through the patient'"'"'s skin adjacent to the coccyx aligned with the visualized anterior axial instrumentation/fusion line; and

forming a percutaneous pathway through presacral tissues in presacral space between the skin incision and an anterior target point of the anterior sacrum aligned with the visualized anterior axial instrumentation/fusion line; and

the step of forming a percutaneous tract further comprises expanding the percutaneous pathway to form the anterior, presacral, percutaneous tract through the patient'"'"'s skin and presacral space aligned with the visualized anterior axial instrumentation/fusion line to provide working space and exposure of the anterior sacrum.

10. The method of claim 8, wherein the accessing step further comprises:

providing a blunted tip tubular member having a tubular member body and blunt tubular member tip; and

inserting the blunted tip tubular member through the incision and advancing the blunt tubular member tip along the anterior surface of the sacrum under visualization until the tubular member tip is at an anterior target point of a selected sacral vertebrae and the tubular member body is aligned with the visualized anterior axial instrumentation/fusion line and extends percutaneously.

11. The method of claim 8, wherein the accessing step further comprises:

providing a blunted tip tubular member having a tubular member lumen within a tubular member body extending from a proximal tubular member end to a distal tubular member end and a blunt tipped occluder fitted into the tubular member to extend distally from the distal tubular member end; and

inserting the blunted tip tubular member through the incision and advancing the blunt tubular member tip along the anterior surface of the sacrum under visualization until the tubular member tip is at an anterior target point of a selected sacral vertebrae and the tubular member body is aligned with the visualized anterior axial instrumentation/fusion line and extends percutaneously; and

the step of forming the anterior, presacral, percutaneous tract further comprises;

removing the blunt tipped occluder from the tubular member lumen;

providing a guidewire having a guidewire body extending between a guidewire proximal end and a guidewire distal end and a guidewire fixation mechanism for penetrating and affixing to bone at the guidewire distal end;

extending the guidewire through said tubular member lumen to locate the guidewire distal end at the anterior target point;

affixing the guidewire fixation mechanism to bone at the anterior target point; and

removing the tubular member body, whereby the guidewire provides a percutaneous tract over or through the tubular member from the incision site to the anterior target point and aligned axially with said visualized anterior axial instrumentation/fusion line.

12. The method of claim 11, further comprising:

dilating the tissue surrounding the guidewire body;

providing an enlarged diameter anterior tract sheath having a tract sheath lumen extending between proximal and distal anterior tract sheath ends; and

inserting said anterior tract sheath through said enlarged anterior tissue tract over said guidewire to position said enlarged diameter anterior tract sheath distal end against the anterior sacrum with the anterior tract sheath lumen aligned axially with the visualized anterior axial instrumentation/fusion line.

13. The method of claim 11, further comprising:

providing a dilatation balloon catheter;

providing an enlarged diameter anterior tract sheath having a tract sheath lumen extending between proximal and distal anterior tract sheath ends;

with the guidewire aligned with the anterior axial instrumentation/fusion line, advancing the dilatation balloon catheter over the guidewire to locate a deflated balloon of the dilatation balloon catheter extending through presacral space;

expanding the deflated balloon to an expanded balloon diameter to dilate the presacral tissue between the anterior sacral surface and the skin incision;

advancing the enlarged diameter anterior tract sheath lumen over the expanded balloon to position the anterior tract sheath between the anterior target point and the skin incision and in alignment with the anterior axial instrumentation/fusion line; and

deflating the balloon and withdrawing the balloon catheter from the anterior tract sheath lumen, whereby the anterior tract sheath lumen provides the anterior, presacral, percutaneous tract through the patient'"'"'s presacral space.

14. The method of claim 11, further comprising:

providing a tissue dilator having a dilator body of a dilation diameter and a dilator lumen having a dilator lumen diameter sized to receive the guidewire and extending between proximal and distal dilator body ends;

passing the dilator over the guidewire toward the anterior target point to dilate the tissue surrounding the guidewire body; and

withdrawing the tissue dilator from the guidewire body upon completion of dilation.

15. The method of claim 14, further comprising:

providing an enlarged diameter anterior tract sheath having a tract sheath lumen extending between proximal and distal anterior tract sheath ends; and

inserting said anterior tract sheath through said enlarged anterior tissue tract to position said enlarged diameter anterior tract sheath distal end against the anterior sacrum with the anterior tract sheath lumen aligned axially with the visualized anterior axial instrumentation/fusion line.

16. The method of claim 11, further comprising:

providing a first tissue dilator having a dilator body of a dilation diameter and a dilator lumen having a dilator lumen diameter sized to receive the guidewire and extending between proximal and distal first tissue dilator body ends;

providing a second tissue dilator having a dilator body of a dilation diameter and a dilator lumen having a dilator lumen diameter sized to receive the first tissue dilator body and extending between proximal and distal second tissue dilator body ends;

passing the first tissue dilator over the guidewire toward the anterior target point to dilate the tissue surrounding the guidewire body;

passing the second tissue dilator over first tissue dilator and the guidewire toward the anterior target point to further dilate the tissue surrounding the guidewire body; and

withdrawing the first and second tissue dilators from the guidewire body upon completion of dilation.

17. The method of claim 16, further comprising:

providing an enlarged diameter anterior tract sheath having a tract sheath lumen extending between proximal and distal anterior tract sheath ends; and

inserting said anterior tract sheath through said enlarged anterior tissue tract to position said enlarged diameter anterior tract sheath distal end against the anterior sacrum with the anterior tract sheath lumen aligned axially with the visualized anterior axial instrumentation/fusion line.

18. The method of claim 11, further comprising:

providing an enlarged diameter tubular anterior tract sheath having a tract sheath lumen extending between proximal and distal anterior tract sheath ends and an anterior tract sheath distal fixation mechanism adapted to attach said enlarged diameter anterior tract sheath to sacral bone;

inserting said enlarged diameter anterior tract sheath through said enlarged anterior tissue tract over said guidewire to position said enlarged diameter anterior tract sheath distal end against the anterior sacrum with the anterior tract sheath lumen aligned axially with the visualized anterior axial instrumentation/fusion line; and

operating said anterior tract sheath distal fixation mechanism to attach said anterior tract sheath to sacral bone with the anterior tract sheath lumen aligned axially with the visualized anterior axial instrumentation/fusion line

19. The method of claim 18, wherein the anterior tract sheath fixation mechanism comprises distal screw threads encircling the distal anterior tract sheath end adapted to be screwed into bone, and the step of affixing the anterior tract sheath distal fixation mechanism to bone at the anterior target point comprises rotating the anterior tract sheath body in a proximal section extending from the skin incision to screw the distal screw threads into sacral bone.

20. A surgical operating system for forming a percutaneous pathway from a skin incision generally axially aligned with a series of adjacent vertebrae located within a human lumbar and sacral spine having an anterior aspect, a posterior aspect and an axial aspect, the vertebrae separated by intact or damaged spinal discs, the system comprising:

guide means operable from a skin incision for accessing an anterior or posterior sacral position of a sacral vertebra that is aligned with a visualized, trans-sacral axial instrumentation/fusion line extending in said axial aspect through the series of adjacent vertebral bodies; and

tract means defining a percutaneous tract having a tract axis aligned with said visualized, trans-sacral axial instrumentation/fusion line and extending from the skin incision to the accessed sacral position to facilitate surgical procedures aligned with said visualized, trans-sacral axial instrumentation/fusion line.

21. A surgical operating system for forming a percutaneous pathway from a skin incision generally axially aligned with a series of adjacent vertebrae located within a human lumbar and sacral spine having an anterior aspect, a posterior aspect and an axial aspect, the vertebrae separated by intact or damaged spinal discs, the system comprising:

an elongated guide assembly extendible from a skin incision for accessing an anterior or posterior sacral position of a sacral vertebra that is aligned with a visualized, trans-sacral axial instrumentation/fusion line extending in said axial aspect through the series of adjacent vertebral bodies; and

a dilator adapted to dilate tissue surrounding the elongated guide assembly to form an enlarged percutaneous tract that is aligned with a visualized, trans-sacral axial instrumentation/fusion line.

22. The system of claim 21, wherein said elongated guide assembly further comprises:

an elongated tubular member enclosing a tubular member lumen extending between a tubular member proximal end and a tubular member distal end; and

an occluder extending between an occluder proximal end and an occluder distal end adapted to be extended through said tubular member lumen.

23. The system of claim 21, further comprising a tract sheath adapted to be fitted over said elongated guide assembly following dilation of tissue, the tract sheath having a tract sheath lumen forming the percutaneous tract having a tract axis aligned with said visualized, trans-sacral axial instrumentation/fusion line extending from the skin incision to the accessed sacral position.

24. Apparatus for obtaining access to and through a series of adjacent vertebrae located within a human lumbar and sacral spine having an anterior aspect, a posterior aspect and an axial aspect, the vertebrae separated by intact or damaged spinal discs, the apparatus comprising:

means for exposing a sacral position of a sacral vertebra in alignment with a visualized, trans-sacral axial instrumentation/fusion line extending in said axial aspect through the series of adjacent vertebral bodies;

means operable from the exposed sacral position for boring a trans-sacral pilot hole extending along said axial instrumentation/fusion line cephalad and axially through the vertebral bodies of said series of adjacent vertebrae and any intervening spinal discs to a pilot hole cephalad end;

a guidewire having a guidewire body extending between a guidewire proximal end and a guidewire distal end having a guidewire fixation mechanism at the guidewire distal end adapted to be advanced into the pilot hole and affixed to vertebral bone at the cephalad end of the pilot hole.

25. A surgical operating system for forming a percutaneous pathway from a skin incision generally axially aligned with a series of adjacent vertebrae located within a human lumbar and sacral spine having an anterior aspect, a posterior aspect and an axial aspect, the vertebrae separated by intact or damaged spinal discs, the system comprising:

guide means operable from a skin incision through a patient'"'"'s skin and exposing a posterior, presacral position of a sacral vertebra in alignment with a visualized, curved, posterior axial instrumentation/fusion line extending in said axial aspect initially laterally through the sacral vertebra and then following the curvature of the spine through a series of adjacent cephalad vertebral bodies for accessing a posterior sacral position of a sacral vertebra that is aligned with the visualized, trans-sacral axial instrumentation/fusion line extending in said axial aspect through the series of adjacent vertebral bodies; and

tract means defining a percutaneous tract having a tract axis aligned with said visualized, trans-sacral axial instrumentation/fusion line and extending from the skin incision to the accessed sacral position to facilitate surgical procedures aligned with said visualized, trans-sacral axial instrumentation/fusion line.

26. The system of claim 25, wherein the tract means comprises a tubular posterior tract sheath forming a posterior percutaneous tract through the patient'"'"'s, presacral space to access the posterior presacral position of a sacral vertebra in alignment with the visualized, anterior axial instrumentation/fusion line extending in said axial aspect through the series of adjacent vertebral bodies to enable boring a curved posterior axial bore extending along said posterior axial instrumentation/fusion line cephalad through the vertebral bodies of said series of adjacent vertebrae and any intervening spinal discs.

27. The system of claim 26, wherein the tubular posterior tract sheath has a tract sheath lumen extending between proximal and distal posterior tract sheath ends and a posterior tract sheath distal fixation mechanism adapted to attach said posterior tract sheath distal end to sacral bone with the posterior tract sheath lumen aligned axially with the visualized posterior axial instrumentation/fusion line.

28. A method of providing access to a series of adjacent vertebrae located within a lumbar and sacral spine having an anterior aspect, a posterior aspect and an axial aspect, the vertebrae separated by intact or damaged spinal discs, the method comprising:

making an incision through the patient'"'"'s dermal entry site aligned with a visualized curved, posterior axial instrumentation/fusion line extending in said axial aspect through the series of adjacent vertebral bodies;

providing a guide assembly having a guide assembly body extending between guide assembly proximal and distal ends, said guide assembly comprising a guide tubular member having a tubular member lumen within a tubular member body extending between proximal and distal tubular member ends;

advancing the guide assembly through the incision to locate the guide assembly distal end against the posterior surface of the sacrum;

further advancing the guide assembly distal end under visualization until the guide assembly distal end is at a posterior target point of a selected sacral vertebrae and the guide assembly body is aligned with the visualized curved, posterior axial instrumentation/fusion line and extends percutaneously to the guide assembly proximal end; and

advancing the tubular member distal end against the posterior target point, whereby the tubular member provides a percutanous tract over or through the tubular member from the dermal entry site to the posterior target point.

29. The method of claim 28, further comprising the step of determining the dermal entry site by mapping the curved, posterior axial instrumentation/fusion line.

30. The method of claim 29, wherein the step of mapping the curved, posterior axial instrumentation/fusion line comprises performing a CT scan.

31. The method of claim 29, wherein the step of mapping the curved, posterior axial instrumentation/fusion line comprises performing a MRI study.

32. The method of claim 28, further comprising the step of performing a laminectomy at the posterior surface of the sacrum.

33. The method of claim 32, further comprising the step of retracting the thecal sac and nerve roots exposed by the laminectomy.

34. The method of claim 28, wherein the step of providing a guide assembly further comprises providing a beveled tip tubular member having a tubular member lumen within a tubular member body extending from a proximal tubular member end to a distal tubular member end as said tubular member.

35. The method of claim 28, wherein the step of providing a guide assembly further comprises providing a blunt tip tubular member having a tubular member lumen within a tubular member body extending from a proximal tubular member end to a distal tubular member end as said tubular member.

36. The method of claim 28, wherein the step of providing a guide assembly further comprises providing a trocar having a trocar lumen within a trocar body extending from a proximal trocar end to a distal trocar end as said tubular member.

37. The method of claim 28, wherein the step of providing a guide assembly further comprises providing a guide sheath having a guide sheath lumen within a guide sheath body extending from a proximal guide sheath end to a distal guide sheath end as said tubular member.

38. A method of providing access to a series of adjacent vertebrae located within a lumbar and sacral spine having an anterior aspect, a posterior aspect and an axial aspect, the vertebrae separated by intact or damaged spinal discs, the method comprising:

making an incision through the patient'"'"'s dermal entry site aligned with a visualized curved, posterior axial instrumentation/fusion line extending in said axial aspect through the series of adjacent vertebral bodies;

providing a guide assembly having a guide assembly body extending between guide assembly proximal and distal ends, said guide assembly comprising;

a guide tubular member having a tubular member lumen within a tubular member body extending between proximal and distal tubular member ends; and

a guidewire having a guidewire body extending between a guidewire proximal end and a guidewire distal end having a guidewire fixation mechanism for penetrating and affixing to bone at the guidewire distal end;

inserting the guidewire through said tubular member lumen to locate the guidewire distal end retracted within said tubular member lumen and said guidewire proximal end extending proximally from said tubular member proximal end;

advancing the guide assembly through the incision to located the guide assembly distal end against the posterior surface of the sacrum;

further advancing the guide assembly distal end under visualization until the guide assembly distal end is at a posterior target point of a selected sacral vertebrae and the guide assembly body is aligned with the visualized curved, posterior axial instrumentation/fusion line and extends percutaneously to the guide assembly proximal end;

extending the guidewire through said tubular member lumen into contact with the sacrum;

affixing the guidewire fixation mechanism to sacral bone at the posterior target point; and

removing the tubular member, whereby the attached guidewire provides a percutaneous tract for over the wire passage extending from the dermal entry site to the posterior target point.

39. The method of claim 38, further comprising the step of determining the dermal entry site by mapping the curved, posterior axial instrumentation/fusion line.

40. The method of claim 39, wherein the step of mapping the curved, posterior axial instrumentation/fusion line comprises performing a CT scan.

41. The method of claim 39, wherein the step of mapping the curved, posterior axial instrumentation/fusion line comprises performing a MRI study.

42. The method of claim 38, wherein the step of providing a guide assembly further comprises providing a blunt tip tubular member having a tubular member lumen within a tubular member body extending from a proximal tubular member end to a distal tubular member as said tubular member.

43. The method of claim 38, wherein the step of providing a guide assembly further comprises providing a trocar having a trocar lumen within a trocar body extending from a proximal trocar end to a distal trocar end as said tubular member.

44. The method of claim 38, wherein the step of providing a guide assembly further comprises providing a guide sheath having a guide sheath lumen within a guide sheath body extending from a proximal guide sheath end to a distal guide sheath end as said tubular member.

45. The method of claim 38, wherein the guidewire fixation mechanism comprises a distal screw-in tip adapted to be screwed into sacral bone.

46. The method of claim 38, wherein the guidewire fixation mechanism comprises a distal sharpened tip adapted to be pushed into sacral bone.

47. The method of claim 38, further comprising:

dilating the tissue surrounding the guidewire body;

providing an enlarged diameter posterior tract sheath having a tract sheath lumen extending between proximal and distal posterior tract sheath ends; and

inserting said posterior tract sheath through said enlarged posterior tissue tract over said guidewire to position said enlarged diameter posterior tract sheath distal end against the posterior sacrum.

48. The method of claim 47, wherein the step of dilating the tissue further comprises:

providing a dilation balloon cathteter having a balloon in the deflated state; and

expanding the deflated balloon to an expanded state to dilate the presacral tissue between the posterior sacral surface and the dermal entry site.