US 20090292287 A1
One or more tools for use in shaped axially oriented bores extending from an accessed posterior or anterior target point are formed in the cephalad direction through vertebral bodies and intervening discs, if present, in general alignment with a visualized, trans-sacral axial instrumentation/fusion (TASIF) line in a minimally invasive, low trauma, manner. An anterior axial instrumentation/fusion line (AAIFL) or a posterior axial instrumentation/fusion line (PAIFL) that extends from the anterior or posterior target point, respectively, in the cephalad direction following the spinal curvature through one or more vertebral body is visualized by radiographic or fluoroscopic equipment. In one embodiment, curved anterior or posterior TASIF axial bores are formed in axial or parallel or diverging alignment with the visualized AAIFL or PAIFL, respectively, employing bore forming tools that can be manipulated from proximal portions thereof that are located outside the patient's body to adjust the curvature of the anterior or posterior TASIF axial bores as they are formed in the cephalad direction. Further bore enlarging tools are employed to enlarge one or more selected section of the anterior or posterior TASIF axial bore(s), e.g., the cephalad bore end or a disc space, so as to provide a recess therein that can be employed for various purposes, e.g., to provide anchoring surfaces for spinal implants inserted into the anterior or posterior TASIF axial bore(s).
1. An apparatus configured for insertion in to a series of adjacent vertebrae located within a spine having an anterior aspect, a posterior aspect and an axial aspect from an anterior or posterior sacral target point of a sacral vertebra extending in the axial aspect through the series of adjacent vertebrae, wherein the axial aspect is curved in the posterior-anterior plane due to curvature of the spinal column, the vertebrae separated by intact or damaged spinal discs, the apparatus comprising:
a sheath extending between a sheath proximal end and a sheath distal end, the sheath having a sheath lumen at least partially extending through a trans-sacral axial bore from the accessed sacral target point cephalad and axially through one or more vertebral bodies of the series of adjacent vertebrae and any intervertebral spinal discs; and
a tool sized to fit within the axial bore, the tool adapted to be inserted from the accessed sacral target point to a selected location along the axial bore, the tool operable from within a section of the axial bore, the tool comprising deployment/retraction means for deploying the tool between a retracted locked position and a deployed locked position.
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a cutting blade extending from the sheath distal end;
a mechanism controlled from the sheath proximal end, the mechanism enabling movement of the cutting blade between an axially aligned position and a radially pivoted position.
This is a continuation application of U.S. patent application Ser. No. 10/853,476, filed on May 25, 2004, which is a continuation of U.S. patent application Ser. No. 09/710,369, filed on Nov. 10, 2000 and issued as U.S. Pat. No. 6,740,090 on May 25, 2004, which claims priority and benefits from Provisional Patent Application No. 60/182,748, filed Feb. 16, 2000, titled METHOD AND APPARATUS FOR TRANS-SACRAL SPINAL FUSION, all of which are incorporated by reference in their entirety.
The present invention relates generally to spinal surgery, particularly methods and apparatus for forming one or more shaped axial bore through vertebral bodies in general alignment with a visualized, trans-sacral axial instrumentation/fusion (TASIF) line in a minimally invasive, low trauma, manner.
It has been estimated that 70% of adults have had a significant episode of back pain or chronic back pain emanating from a region of the spinal column or backbone. Many people suffering chronic back pain or an injury requiring immediate intervention resort to surgical intervention to alleviate their pain.
The spinal column or back bone encloses the spinal cord and consists of 33 vertebrae superimposed upon one another in a series which provides a flexible supporting column for the trunk and head. The vertebrae cephalad (i.e., toward the head or superior) to the sacral vertebrae are separated by fibrocartilaginous intervertebral discs and are united by articular capsules and by ligaments. The uppermost seven vertebrae are referred to as the cervical vertebrae, and the next lower twelve vertebrae are referred to as the thoracic, or dorsal, vertebrae. The next lower succeeding five vertebrae below the thoracic vertebrae are referred to as the lumbar vertebrae and are designated L1-L5 in descending order. The next lower succeeding five vertebrae below the lumbar vertebrae are referred to as the sacral vertebrae and are numbered S1-S5 in descending order. The final four vertebrae below the sacral vertebrae are referred to as the coccygeal vertebrae. In adults, the five sacral vertebrae fuse to form a single bone referred to as the sacrum, and the four rudimentary coccyx vertebrae fuse to form another bone called the coccyx or commonly the “tail bone”. The number of vertebrae is sometimes increased by an additional vertebra in one region, and sometimes one may be absent in another region.
Typical lumbar, thoracic and cervical vertebrae consist of a ventral or vertebral body and a dorsal or neural arch. In the thoracic region, the ventral body bears two costal pits for reception of the head of a rib on each side. The arch which encloses the vertebral foramen is formed of two pedicles and two lamina. A pedicle is the bony process which projects backward or anteriorly from the body of a vertebra connecting with the lamina on each side. The pedicle forms the root of the vertebral arch. The vertebral arch bears seven processes: a dorsal spinous process, two lateral transverse processes, and four articular processes (two superior and two inferior). A deep concavity, inferior vertebral notch, on the inferior border of the arch provides a passageway or spinal canal for the delicate spinal cord and nerves. The successive vertebral foramina surround the spinal cord. Articulating processes of the vertebrae extend posteriorly of the spinal canal.
The bodies of successive lumbar, thoracic and cervical vertebrae articulate with one another and are separated by intervertebral discs formed of fibrous cartilage enclosing a central mass, the nucleus pulposus that provides for cushioning and dampening of compressive forces to the spinal column. The intervertebral discs are anterior to the vertebral canal. The inferior articular processes articulate with the superior articular processes of the next succeeding vertebra in the caudal (i.e., toward the feet or inferior) direction. Several ligaments (supraspinous, interspinous, anterior and posterior longitudinal, and the ligamenta flava) hold the vertebrae in position yet permit a limited degree of movement.
The relatively large vertebral bodies located in the anterior portion of the spine and the intervertebral discs provide the majority of the weight bearing support of the vertebral column. Each vertebral body has relatively strong bone comprising the outside surface of the body and weak bone comprising the center of the vertebral body.
Various types of spinal column disorders are known and include scoliosis (abnormal lateral curvature of the spine), kyphosis (abnormal forward curvature of the spine, usually in the thoracic spine), excess lordosis (abnormal backward curvature of the spine, usually in the lumbar spine), spondylolisthesis (forward displacement of one vertebra over another, usually in the lumbar or cervical spine) and other disorders, such as ruptured or slipped discs, degenerative disc disease, fractured vertebra, and the like. Patients who suffer from such conditions usually experience extreme and debilitating pain and often neurologic deficit in nerve function.
Approximately 95% of spinal surgery involves the lower lumbar vertebrae designated as the fourth lumbar vertebra (“L4”), the fifth lumbar vertebra (“L5”), and the first sacral vertebra (“S1”). Persistent low back pain is attributed primarily to degeneration of the disc connecting L5 and S1. Surgical procedures have been developed and used to remove the disc and fuse the vertebral bodies together and/or to stabilize the intervertebral structures. Although damaged discs and vertebral bodies can be identified with sophisticated
diagnostic imaging, the surgical procedures are so extensive that clinical outcomes are not consistently satisfactory. Furthermore, patients undergoing presently available fusion surgery experience significant complications and uncomfortable, prolonged convalescence.
A number of devices and techniques involving implantation of spinal implants to reinforce or replace removed discs and/or anterior portions of vertebral bodies and which mechanically immobilize areas of the spine assisting in the eventual fusion of the treated adjacent vertebrae have also been employed or proposed over the years In order to overcome the disadvantages of purely surgical techniques. Such techniques have been used effectively to treat the above described conditions and to relieve pain suffered by the patient. However, there are still disadvantages to the present fixation implants and surgical implantation techniques. The historical development of such implants is set forth in U.S. Pat. Nos. 5,505,732, 5,514,180, and 5,888,223, for example.
One technique for spinal fixation includes the immobilization of the spine by the use of spine rods of many different configurations that run generally parallel to the spine. Typically, the posterior surface of the spine is isolated and bone screws are first fastened to the pedicles of the appropriate vertebrae or to the sacrum and act as anchor points for the spine rods. The bone screws are generally placed two per vertebra, one at each pedicle on either side of the spinous process. Clamp assemblies join the spine rods to the screws. The spine rods are generally bent to achieve the desired curvature of the spinal column. Wires may also be employed to stabilize rods to vertebrae. These techniques are described further in U.S. Pat. No. 5,415,661, for example.
These types of rod systems can be effective, but require a posterior approach and implanting screws into or clamps to each vertebra over the area to be treated. To stabilize the implanted system sufficiently, one vertebra above and one vertebra below the area to be treated are often used for implanting pedicle screws. Since the pedicles of vertebrae above the second lumbar vertebra (L2) are very small, only small bone screws can be used which sometimes do not give the needed support to stabilize the spine. These rods and screws and clamps or wires are surgically fixed to the spine from a posterior approach, and the procedure is difficult. A large bending moment is applied to such rod assemblies, and because the rods are located outside the spinal column, they depend on the holding power of the associated components which can pull out of or away from the vertebral bone.
In a variation of this technique disclosed in U.S. Pat. Nos. 4,553,273 and 4,636,217, both described in U.S. Pat. No. 5,735,899, two of three vertebrae are joined by surgically obtaining access to the interior of the upper and lower vertebral bodies through excision of the middle vertebral body. In the '899 patent, these approaches are referred to as “intraosseous” approaches, although they are more properly referred to as “interosseous” approaches by virtue of the removal of the middle vertebral body. The removal is necessary to enable a lateral insertion of the implant into the space it occupied so that the opposite ends of the implant can be driven upward and downward into the upper and lower vertebral bodies. These approaches are criticized as failing to provide adequate medial-lateral and rotational support in the '899 patent. In the '899 patent, an anterior approach is made, slots are created in the upper and lower vertebrae, and rod ends are fitted into the slots and attached to the remaining vertebral bodies of the upper and lower vertebrae by laterally extending screws.
A number of disc shaped replacements or artificial disc implants and methods of insertion have been proposed as disclosed, for example, in U.S. Pat. Nos. 5,514,180 and 5,888,223, for example. A further type of disc reinforcement or augmentation implant that has been clinically employed for spinal fusion comprises a hollow cylindrical titanium cage that is externally threaded and is screwed laterally into place in a bore formed in the disc between two adjacent vertebrae. Bone grafts from cadavers or the pelvis or substances that promote bone growth are then packed into the hollow center of the cage to encourage bone growth (or ingrowth) through the cage pores to achieve fusion of the two adjacent vertebrae. Two such cage implants and the surgical tools employed to place them are disclosed in U.S. Pat. Nos. 5,505,732 and 5,700,291, for example. The cage implants and the associated surgical tools and approaches require precise drilling of a relatively large hole for each such cage laterally between two adjacent vertebral bodies and then threading a cage into each prepared hole. The large hole or holes can compromise the integrity of the vertebral bodies, and if drilled too posteriorly, can injure the spinal cord. The end plates of the vertebral bodies, which comprise very hard bone and help to give the vertebral bodies needed strength, are usually destroyed during the drilling. The cylindrical cage or cages are now harder than the remaining bone of the vertebral bodies, and the vertebral bodies tend to collapse or “telescope,” together. The telescoping causes the length of the vertebral column to shorten and can cause damage to the spinal cord and nerves that pass between the two adjacent vertebrae.
Methods and apparatus for accessing the discs and vertebrae by lateral surgical approaches are described in U.S. Pat. No. 5,976,146. The intervening muscle groups or other tissues are spread apart by a cavity forming and securing tool set disclosed in the '146 patent to enable endoscope aided, lateral access to damaged vertebrae and discs and to perform corrective surgical procedures.
A compilation of the above described surgical techniques and spinal implants and others that have been used clinically is set forth in certain chapters of the book entitled Lumbosacral and Spinopelvic Fixation, edited by Joseph Y. Margolies et al. (Lippincott-Raven Publishers, Philadelphia, 1996). Attention is directed particularly to Chapters 1, 2, 17, 18, 38, 42 and 44. In “Lumbopelvic Fusion” (Chapter 38, by Prof. Rene P. Louis, MD) techniques for repairing a spondylolisthesis, in this case, a severe displacement of L5 with respect to S1 and the intervening disc, are described and depicted. An anterior lateral exposure of L5 and S1 is made, a discectomy is performed, and the orientation of L5 to S1 is mechanically corrected using a reduction tool, if the displacement is severe. A fibula graft or metal Judet screw is inserted as a dowel through a bore formed extending caudally through L5 and into S1. When the screw is used, bone growth material, e.g., bone harvested from the patient, is inserted into the bore alongside the screw, and the disc space is filled with bone sutured to the screw to keep it in place between the vertebral surfaces to act as a spacer implant occupying the extracted disc between L5 and S1. External bridge plates or rods are also optionally installed. The posterolateral or anterior lateral approach is necessitated to correct the severe spondylolisthesis displacement using the reduction tool and results in tissue injury. Because of this approach and need, the caudal bore and inserted the Judet screw can only traverse L5 and S1.
A similar anterior approach for treating spondylolisthesis is disclosed in U.S. Pat. No. 6,056,749. In this approach, a bore hole is formed in a cephalad vertebral body and extends through the intervening disc into a caudal vertebral body, the disc is removed, a disk cage is inserted laterally into the disc space, and an elongated, hollow threaded shaft is inserted into the bore and through a hole in the disc cage. The disk cage takes the place of the harvested bone disc inserts and its interlocking intersection with the shaft takes the place of the sutures employed to tie the harvested bone disc inserts to the screw in the technique described in the above-referenced Chapter 38 publication.
The above-described spinal implant approaches involve highly invasive surgery that laterally exposes the anterior or posterior portions of the vertebrae to be supported or fused. Extensive muscular stripping and bone preparation can be necessary. As a result, the spinal column can be further weakened and/or result in surgery induced pain syndromes. Thus, presently used or proposed surgical fixation and fusion techniques involving the lower lumbar vertebrae suffer from numerous disadvantages. It is preferable to avoid the lateral exposure to correct less severe spondylolisthesis and other spinal injuries or defects affecting the lumbar and sacral vertebrae and discs.
A less intrusive posterior approach for treating spondylolisthesis is disclosed in U.S. Pat. No. 6,086,589, wherein a straight bore is formed through the sacrum from the exposed posterior sacral surface and in a slightly cephalad direction into the L5 vertebral body, preferably after realigning the vertebrae. A straight, hollow, threaded shaft with side wall holes restricted to the end portions thereof and bone growth material are inserted into the bore. A discectomy of the disc between L5 and S1 is preferably performed and bone ingrowth material is also preferably inserted into the space between the cephalad and caudal vertebral bodies. Only a limited access to and alignment of S1 and L5 can be achieved by this approach because the distal ends of the straight bore and shaft approach and threaten to perforate the anterior surface of the L5 vertebral body.
A wide variety of orthopedic implants have also been proposed or clinically employed to stabilize broken bones or secure artificial hip, knee and finger joints. Frequently, rods or joint supports are placed longitudinally within longitudinal bores made in elongated bones, e.g., the femur. A surgical method is disclosed in U.S. Pat. No. 5,514,137 for stabilizing a broken femur or other long bones using an elongated rod and resorbable cement. To accomplish a placement of a rod into any single bone, an end of a bone is exposed and a channel is drilled from the exposed end to the other end. Thereafter, a hollow rod is inserted, and resorbable cement is injected through the hollow rod, so as to provide fixation between the distal end of the rod and the cancellous tissue that surrounds the rod. A cement introducer device can also be used for the injection of cement. A brief reference is made in the '137 patent to the possibility of placing rods in or adjacent to the spine in the same manner, but no particular approach or devices are described.
Drilling tools are employed in many of the above described surgical procedures to bore straight holes into the vertebral bones. The boring of curved bores in other bones is described in U.S. Pat. Nos. 4,265,231, 4,541,423, and 5,002,546, for example. The '231 patent describes an elongated drill drive shaft enclosed within a pre-curved outer sheath that is employed to drill curved suture holding open ended bores into bones so that the suture passes through both open ends of the bore. The '423 patent describes an elongated flexible drill drive shaft enclosed within a malleable outer sheath that can be manually shaped into a curve before the bore is formed. The '546 patent describes a complex curve drilling tool employing a pivotal rocker arm and curved guide for a drill bit for drilling a fixed curve path through bone. All of these approaches dictate that the curved bore that is formed follow the predetermined and fixed curvature of the outer sheath or guide. The sheath or guide is advanced through the bore as the bore is made, making it not possible for the user to adjust the curvature of the bore to track physiologic features of the bone that it traverses.
The preferred embodiments of the invention involve methods and apparatus for forming one or more axial bore through spinal vertebral bodies for performing surgical procedures for receiving spinal implants, or for other medical reasons wherein the axial bore is shaped with one or more recess adapted to anchor spinal implants or receive material dispensed therein or for other purposes.
The preferred embodiments of the present invention involve methods and apparatus including surgical tool sets for first forming an anterior or posterior TASIF axial bore(s) extending from a respective anterior or posterior target point of an anterior or posterior sacral surface through at least one sacral vertebral body and one or more lumbar vertebral body in the cephalad direction. Then, further bore enlarging tools are employed to enlarge one or more selected section of the anterior or posterior TASIF axial bore(s), e.g., the cephalad bore end or a disc space along the bore, so as to provide a recess therein. The recess can be employed for various purposes, e.g., to provide anchoring surfaces for spinal implants inserted into the anterior or posterior TASIF axial bore(s), or to received materials placed into the recess formed in a disc space or vertebral body.
To form an axial bore, the anterior target point on the anterior sacral surface is accessed using a percutaneous tract extending from a skin incision through presacral space. The posterior target point on the posterior sacral surface is accessed using a surgical exposure of the posterior sacral surface. An anterior axial instrumentation/fusion line (AAIFL) or a posterior axial instrumentation/fusion line (PAIFL) that extends from the anterior or posterior target point, respectively, in the cephalad direction following the spinal curvature through one or more vertebral body is visualized by radiographic or fluoroscopic equipment. Preferably, curved anterior or posterior TASIF axial bores are formed in axial or parallel alignment with the visualized AAIFL or PAIFL, respectively, although the invention is not confined to curved axial bores.
When a single anterior or posterior TASIF axial bore is formed, it can be formed in axial or parallel alignment with the visualized axial AAIFL and PAIFL. Similarly, multiple anterior or posterior TASIF axial bores can be formed all in parallel alignment with the visualized axial AAIFL and PAIFL or with at least one such TASIF axial bore formed in axial alignment with the visualized axial AAIFL and PAIFL.
Moreover, multiple anterior or posterior TASIF axial bores can be formed all commencing at the anterior or posterior target point and extending in the cephalad direction with each TASIF axial bore diverging apart from the other and away from the visualized axial AAIFL and PAIFL. The diverging TASIF axial bores terminate as spaced apart locations in a cephalad vertebral body or in separate cephalad vertebral bodies.
In certain embodiments, small diameter anterior and posterior TASIF axial bore forming tools can be employed in the same manner to form pilot holes extending in the cephalad direction through one or more sacral and lumbar vertebral bodies in alignment with the visualized AAIFL and PAIFL. The pilot holes can be used as part of anterior and posterior percutaneous tracts that are subsequently enlarged to form the anterior and posterior TASIF axial bores.
This summary of the invention and the objects, advantages and features thereof have been presented here simply to point out some of the ways that the invention overcomes difficulties presented in the prior art and to distinguish the invention from the prior art and is not intended to operate in any manner as a limitation on the interpretation of claims that are presented initially in the patent application and that are ultimately granted.
These and other advantages and features of the present invention will be more readily understood from the following detailed description of the preferred embodiments thereof, when considered in conjunction with the drawings, in which like reference numerals indicate identical structures throughout the several views, and wherein:
The methods and surgical instrumentation and spinal implants disclosed in the above-referenced provisional application No. 60/182,748 and in co-pending, commonly assigned, patent application Ser. No. 09/640,222 filed Aug. 16, 2000, for METHOD AND APPARATUS FOR PROVIDING POSTERIOR OR ANTERIOR TRANS-SACRAL ACCESS TO SPINAL VERTEBRAE can be employed in the practice of the present invention. The '222 application discloses a number of related TASIF methods and surgical tool sets for providing posterior and anterior trans-sacral 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. Certain of the tools are selectively employed to form a percutaneous (i.e., through the skin) pathway from an anterior or posterior skin incision to a respective anterior or posterior position, e.g., a target point of a sacral surface or the cephalad end of a pilot hole bored through the sacrum and one or more lumbar vertebrae. The percutaneous pathway is generally axially aligned with the AAIFL or the PAIFL extending from the respective anterior or posterior target point through at least one sacral vertebral body and one or more lumbar vertebral body in the cephalad direction as visualized by radiographic or fluoroscopic equipment. The AAIFL and PAIFL follow the curvature of the vertebral bodies that they extend through in the cephalad direction.
Attention is first directed to the following description of
The lower regions of the spinal column comprising the coccyx, fused sacral vertebrae S1-S5 forming the sacrum, and the lumbar vertebrae L1-L5 described above are depicted in a lateral view in
The method and apparatus for forming an anterior or posterior TASIF axial bore initially involves accessing an anterior sacral position, e.g. an anterior target point at the junction of S1 and S2 depicted in
It should be noted that the formation of the anterior tract 26 through presacral space under visualization described above is clinically feasible as evidenced by clinical techniques described by J. J. Trambert, MD, in “Percutaneous Interventions in the Presacral Space: CT-guided Precoccygeal Approach—Early Experience (Radiology 1999; 213:901-904).
Step S100 preferably involves creation an anterior or posterior percutaneous pathway that enables introduction of further tools and instruments for forming an anterior or posterior percutaneous tract extending from the skin incision to the respective anterior or posterior target point of the sacral surface or, in some embodiments, the cephalad end of a pilot hole over which or through which further instruments are introduced as described in the above-referenced '222 application. An “anterior, presacral, percutaneous tract” extends through the “presacral space” anterior to the sacrum. The posterior percutaneous tract or the anterior, presacral, percutaneous tract is preferably used to bore one or more respective posterior or anterior TASIF bore in the cephalad direction through one or more lumbar vertebral bodies and intervening discs, if present. A single anterior or posterior TASIF bore is preferably aligned axially with the respective visualized AAIFL or PAIFL, and plural anterior or posterior TASIF bores are preferably aligned in parallel with the respective visualized AAIFL or PAIFL. Introduction of spinal implants and instruments for performing discectomies and/or disc and/or vertebral body augmentation is enabled by the provision of the percutaneous pathway and formation of the anterior or posterior TASIF bore(s).
It should be noted that performing step S100 in the anterior and/or posterior TASIF procedures may involve drilling a pilot hole, smaller in diameter than the TASIF axial bore, that tracks the AAIFL and/or PAIFL in order to complete the formation of the anterior and/or posterior percutaneous tracts. Step S300 may optionally be completed through the AAIFL/PAIFL pilot hole following step S100, rather than following the enlargement of the pilot hole to form the TASIF axial bore in step S200.
The preferred embodiments of the present invention involve methods and apparatus including surgical tool sets for forming pilot holes or curved, posterior and anterior, TASIF axial bores 22 or 152 or 22 1 . . . 22 n, or 152 1 . . . 152 n shown in
The elongated drill shaft assembly 12 further comprises a pre-curved inner sheath 34 having an inner sheath lumen 36 receiving and enclosing the drive shaft 26, an outer sheath 40 having an outer sheath lumen 42 enclosing the inner sheath 34, and a housing 16 that is attached to the proximal end of the inner sheath 34. The outer sheath 40 can be retracted proximally over the inner sheath 34 so that a distal segment of the inner sheath 34 is exposed or extended distally over the inner sheath 34 so that the distal segment thereof is enclosed within the outer sheath lumen 42.
The drive shaft 26 is flexible and bendable and can formed of a single filament or multi-filar straight or coiled wire and is preferably radiopaque so that it can be observed using conventional imaging equipment. The distal end of the drive shaft 26 is attached to the drill bit 20 by in any manner, e.g., by welding to a proximal surface thereof or by being crimped inside a crimp tube lumen of a proximally extending crimp tube 44 of the drill bit 20 as shown in
The outer diameters of the housing 16 and the drill bit 20 exceed the outer diameter of the straight outer sheath 40. The straight outer sheath 40 can be moved back and forth over the pre-curved inner sheath 34 between a proximal position depicted in
The straight outer sheath 40 is preferably formed of a stiff metal or plastic tube that is relatively stiffer and shorter in length than the more flexible, pre-curved inner sheath 34. The more flexible, pre-curved inner sheath 34 can be formed of a plastic or metal thin walled tubing and is pre-curved in a single plane to a suitable angle, e.g., about a 90° angle, in the distal segment thereof as shown in
It will be understood that the illustrated diameter of the posterior TASIF axial bore hole 22 relative to sizes of the vertebral bodies is merely exemplary, and that it is contemplated that the pilot holes and bore hole diameters can range from range from about 1-10 mm and 3-30 mm, respectively. Moreover, it will be understood that a plurality of such posterior TASIF axial bores 22 1 . . . 22 n can be formed in side by side relation generally aligned with the PAIFL.
The elongated drill shaft assembly 12 is axially aligned with the PAIFL at the posterior target point so that the initial penetration of the sacrum is substantially at right angles to the exposed sacral surface. A drill guide for receiving the drill drive shaft assembly for drilling or boring a TASIF axial bore from S2 along the visualized PAIFL 20 may optionally be attached to S2 and extended posteriorly through the exposed spinal canal and skin incision. In this starting position, the straight outer sheath 40 is fully distally extended to straighten the inner sheath 34, and the drill bit 20 is rotated to commence boring a posterior TASIF axial bore 22. The elongated drill shaft assembly 12 thus advances anteriorly to form a straight segment or section of the posterior TASIF axial bore 22.
The progress of the drill bit 20 is observed using conventional imaging equipment. As the elongated drill shaft assembly 12 is extended anteriorly, it is necessary to retract the straight outer sheath 34 proximally to allow the inner sheath to curve in the cephalad direction to introduce a curvature in the cephalad segment of the posterior TASIF axial bore 22 as shown in
In this starting position, the straight outer sheath 40 is either fully distally extended to straighten the inner sheath 34 or retracted slightly depending on the patient's anatomy to provide an optimal orientation to the AAIFL. The drill bit 20 is rotated to commence boring an anterior TASIF axial bore 152, and the elongated drill shaft assembly 12 advances anteriorly to form a relatively straight or slightly curved segment of the posterior TASIF axial bore 22.
Again, the progress of the drill bit 20 is observed using conventional imaging equipment. As the elongated drill shaft assembly 12 is extended in the cephalad direction through S1, D5 (if present) and L5, it becomes necessary to retract the straight outer sheath 34 proximally to allow the inner sheath to curve in the cephalad direction to introduce a greater degree of curvature in the cephalad segment of the anterior TASIF axial bore 152 as shown in
Slight but abrupt angular changes in the overall curvature of the anterior TASIF axial bore 152 are made within the vertebral bodies of L5 and L4 as shown in
The tip deflection wire 104 extends through the wire lumen extending along one side of the drive shaft sheath 134 between an attachment point at the distal end 124 and an attachment within housing 138 with distal segment curvature control ring 106 mounted on housing 138. The distal segment of drive shaft sheath 134 distal to junction 136 is more flexible than the proximal segment of drive shaft sheath 134 proximal to junction 136. The distal segment curvature control ring 106 is located over the cylindrical surface of housing 138, and an inwardly extending member extends into an elongated groove 108 in the housing 138 where it is attached to the proximal end of the tip deflection wire 104. The retraction of tip deflection wire 104 to form the curves in the drive shaft distal segment depicted in
The boring tool 110 can be employed to form the posterior and anterior TASIF axial bores 22 and 152 or a plurality of the same in the same manner as described above with respect to
The drive shaft 226 is flexible and bendable enough to be either be straight when extended distally or curved in use as described below and can formed of a single filament or multi-filar straight or coiled wire that is preferably radiopaque so that it can be observed using conventional imaging equipment. The distal end of the drive shaft 226 is attached to the spherical drill bit 220 by in any manner, e.g., by welding to a proximal surface thereof or by being crimped inside a crimp tube lumen of a proximally extending crimp tube 244 of the drill bit 220 as shown in
The flexible outer sheath 240 is generally circular in cross-section and extends between a push-pull proximal handle 250 and a distal end thereof. The outer sheath lumen 242 is radially offset from the axis of the flexible outer sheath 240 so that the drill shaft 226 and optional inner sheath 234 extend through the outer sheath lumen to locate the drill bit 220 offset from the axis of the flexible outer sheath 240 as shown in
A curvature in the distal segment of the outer and inner sheaths 240 and 234 toward the radial offset direction D (
The boring tool 210 can be employed to form the posterior and anterior TASIF axial bores 22 and 152 or a plurality of the same in the same manner as described above with respect to
It will be understood that the above-described embodiments of TASIF axial bore or pilot hole boring tools can be modified in many ways. For example, the elongated drive shaft assemblies can be modified to provide fluid lumens for pumping flushing fluids into the TASIF axial bores at the distal ends thereof and for conveying flushing fluid and bone fragments proximally to the exterior of the patient's body. Also, the elongated drive shaft assemblies can be modified to provide a guide wire lumen extending from the proximal to the distal ends thereof for advancement over a guidewire. Suitable drive motors for rotating a drive shaft over a guidewire and drive shaft assemblies having flushing capabilities are disclosed in U.S. Pat. No. 6,066,152, for example.
When a single posterior or anterior TASIF axial bore 22 or 152 is formed, it can be formed in axial or parallel alignment with the visualized axial AAIFL and PAIFL as described. Similarly, multiple posterior or anterior TASIF axial bores can be formed all in parallel alignment with the visualized axial AAIFL and PAIFL or with at least one such TASIF axial bore formed in axial alignment with the visualized axial AAIFL and PAIFL.
Moreover, multiple anterior or posterior TASIF axial bores can be formed all commencing at an anterior or posterior target point of
Thus, the above-described tool sets can be employed to bore a curved trans-sacral axial bore or pilot hole in alignment with said axial fusion line cephalad and axially through the vertebral bodies of said series of adjacent vertebrae and any intervertebral spinal discs. The alignment can be axial alignment as shown in
The recesses preferably extend outward into the vertebral bone or into the intervertebral discs so that anchoring surfaces are formed that are generally normal or at an angle to the axis of the anterior or posterior TASIF axial bore(s) 22 or 152 traversing the recesses. The anchoring surfaces accommodate outwardly extending anchor portions or structures of the elongated spinal implants to maintain them in position within the anterior or posterior TASIF axial bore(s) 22 or 152.
Moreover, it is anticipated that one or more recess can be formed extending into the intervertebral disc space, e.g. at disc D5 or D4 or D3 depicted in
A wide variety of tools having bore enlarging cutting heads can be employed to counterbore the recess 154, 154′, as long as they can be delivered and operated through the anterior TASIF axial bore(s) or posterior TASIF axial bore(s) 22. It is necessary that the cutting head be delivered to the cephalad end or other site of the axial bore by way of an elongated flexible counterbore drive shaft that can conform to the curvature of the axial bore. The flexible tool drive shaft would be driven, typically rotated, within the confines of the axial bore to cause the cutting tool to counterbore the recess 154, 154′ at the selected site. The elongated flexible counterbore drive shaft and distal cutting tool can be delivered directly through the axial bore and guided thereby to the selected location for forming a recess. Or, they can be delivered through a flexible protective outer sheath and/or over a guidewire previously placed and attached to vertebral bone at the cephalad end of the axial bore. Then, the cutting tool is deployed at the selected site, preferably by rotation through the flexible tool drive shaft or through manipulation of a deployment wire or the like, to extend outward of the axial bore. The flexible tool drive shaft is then rotated by a drive motor attached to its proximal end outside the patient's body to rotate the cutting tool to cut or abrade away the cancellous bone or disc body thereby enlarging the bore diameter to counterbore the recess. After the recess is formed, the cutting tool is retracted by manipulation of a deployment wire or automatically when the drive motor is turned off. For simplicity, the following descriptions of preferred counterbore tools describe forming recess 154 within a vertebral body, but apply as well to forming a disc recess 154′.
The cutting head 420 is formed of a thin flexible metal tube that is slit lengthwise into a number N cutting tool bands 424 1 to 424 n. The N cutting tool bands 424 1 to 424 n are spring-like and normally are straight as depicted in
Then, pull wire 414 is pulled proximally from proximal manipulator 416 and fixed at a first retracted position to commence counter boring the recess within the soft spongy cancellous bone of the vertebral body. The pull wire 414 pulls the cutting tool distal end 422 proximally causing the N cutting tool bands 424 1 to 424 n to bow outward as shown in
The rotation of the cutting tool bands 424 1 to 424 n is halted when a desired size of the recess is achieved. The pull wire 414 is then released to restore the cutting head 420 to the straight shape depicted in
The cutting tool 400 can be varied in many respects, e.g., by changing the shape, length, number and materials used for the cutting tool bands 424 1 to 424 n. Moreover, it would be possible to employ a push wire to push the cutting tool bands 424 1 to 424 n from the configuration of
In addition, the proximal manipulator 416 can be replaced by a material feed length metering tool that automatically pulls the pull wire 414 (or pushes in the case of a push wire) until resistance is met when the drive motor 402 is de-energized to increase the outward expansion of the cutting tool bands 424 1 to 424 n.
A further cutting tool 500 is depicted in
The cutting head 520 is formed of a thin flexible metal tube that is slit lengthwise to form a gap 532, and a cutting tool wire or band 524 extends the length of the gap 532. The distal end of the cutting tool wire or band is fixed to the interior of the cutting head 520 at or near the distal end 522. The distal end of the push wire 514 is attached to the proximal end of the cutting tool wire or band 524 within the drive shaft lumen 512. The cutting tool wire or band 524 is spring-like and normally is straight when push wire manipulator 516 is pulled proximally as depicted in
Then, push wire 514 is pushed distally from proximal manipulator 516 and fixed at an extended position to commence counter boring the recess within the soft spongy cancellous bone of the vertebral body. The push wire 514 pushes the cutting wire or band 524 out of the gap 532 as shown in
The rotation of the cutting tool or band 524 is halted when a desired size of the recess is achieved. The push wire 514 is then released to restore the cutting head 520 to the straight shape depicted in
A further cutting tool 600 is depicted in
The cutting head 620 is formed of a one or a plurality N of abrading cables 624 1-624 n that are attached to or crimped into a lumen of the drive shaft distal end 618 and are of relatively short length. The abrading cables 624 1-624 n are formed of a woven or braided metal or fabric that are preferably coated or otherwise formed with an abrasive compound and tend to spring outward when unrestrained.
The cutting head 620 is advanced to the site for forming the recess 154 while retracted within the outer sheath lumen 606 as shown in
The abrading cables 624 1-624 n are depicted as extending distally from the drive shaft distal end 618, so that they tend to spread apart to flail at the surrounding bone when the drive shaft 612 is rotated by drive motor 602. However, it will be understood that the abrading cables 624 1-624 n can be attached to the drive shaft 612 to extend at right angles to the drive shaft 612 such that they are wound about it when retracted within lumen 606. Then when the abrading cables 624 1-624 n are released, they tend to extend outward laterally to the axis of the drive shaft 612 when it is rotated.
More rigid boring or cutting elements can be employed than flexible cables including knives, routing bits and saw teeth that are retracted when passed through the TASIF axial bore and then either passively or actively extended outward to bore out a recess in the axial bore wall.
The schematically depicted drive motor 702 is coupled to the proximal end of a drive shaft 704 that is enclosed within the lumen 706 of an elongated flexible sheath 710 that is movable from an advanced position of
The cutting blades 724 1 and 724 2 are normally located within the bore 740 as the recess forming tool 400 is inserted through the posterior or anterior TASIF axial bore 22 or 152 to a selected site, e.g., the cephalad end within the most cephalad lumbar vertebral body, in the configuration depicted in
Then, twist wire 714 is twisted from proximal manipulator 716 and fixed at an extended position to commence counter boring the recess within the soft spongy cancellous bone of the vertebral body. The sharp edges of the cutting blades 724 1 and 724 2 cut away the surrounding vertebral bone. The twist wire 714 can be twisted further so that the cutting blades 724 1 and 724 2 extend further outward as the boring progresses If further enlargement of the recess is desired. An automatic twist mechanism can be substituted for the proximal manipulator 716 to cause it to automatically twist the twist wire 714 as the recess is enlarged.
The rotation of the cutting head 720 is halted when a desired size of the recess is achieved. The twist wire 714 is then twisted in the opposite direction to retract the cutting blades 724 1 and 724 2 to the retracted position of
There are other possible ways of restraining and extending the cutting blades 724 1 and 724 2 within and from the bore 740. In one alternative embodiment, the cutting blades 724 1 and 724 2 can be loosely restrained or hinged within the bore 740 such that centrifugal force causes the cutting blades 724 1 and 724 2 to extend outward as the drive shaft 704 is rotated by motor 702 and the soft cancellous bone of the vertebral body is cut away. In a further approach, the centrifugal force can be augmented by trapped springs within the bore 740.
The schematically depicted drive motor 802 is coupled to the proximal end of a drive shaft 804 that is enclosed within the lumen 806 of an elongated flexible sheath 810 that is movable from an advanced position of
The drive shaft 804 is formed with a drive shaft lumen 812 extending from the drive motor 802 to the junction 818 with the cutting head 820 that extends to the drive shaft distal end 822. The drive shaft lumen 812 encloses a tip deflection wire 814 that extends proximally from the drive shaft connection with the drive motor 802 through the drive motor 802 to a proximal tip deflection wire manipulator 816. The distal end of the tip deflection wire 814 is attached to proximal extension 834 of blade 824 via a rotatable connection.
A pin and slot hinge 830 is formed between the blade 824 and in the drive shaft end 822. A flange having an elongated slot is formed inside the drive shaft lumen 812, and a hole is formed through the blade 824. The proximal end of a hinge pin is trapped within the elongated slot, and the distal end of the hinge pin is trapped within the circular hole formed through the blade 824. There are many possible equivalent ways of hinging and extending the cutting blade 824 to angle the cutting edge 832 to the cancellous bone.
In use, the cutting tool 820 is introduced to the site within the TASIF axial bore 22 or 152 where the recess is to be formed with the cutting blade 824 in the retracted position of
The rotation of the cutting head 820 is halted when a desired size and shape of the recess is achieved. The tip deflection wire 814 is pulled proximally, causing the proximal end of the hinge pin to slide along the slot to its proximal end and the distal end of the hinge pin to rotate within the circular hole. The cutting blade 824 then pivots from the extended position of
It will be understood that features of the above described cutting heads can be substituted for one another or combined together. For example, abrading materials or abrasive coated surfaces may substituted for sharpened cutting blade edges or added to such edges or to cutting wire surfaces.
The curved, posterior and anterior TASIF axial bores 22 and 152 that are formed in step S200 of
It will be understood that various types of axial spinal implants can be inserted into the above-described curved, posterior and anterior TASIF axial bores 22 and 152. When a counterbore recess is formed as described above, it receives anchor members of the axial spinal implant to maintain it in place. Such axial spinal implants can be combined with laterally installed disc replacements or spacers.
The preferred embodiments of the present invention for forming recesses within axial bores have been described above in relation specifically to curved axial bores. However, it will be understood that the methods and apparatus for forming such recesses can advantageously be practiced within straight or relatively straight axial bores. Moreover, it will be understood that such recesses may be formed at the caudal end of the axial bores or at one or more location intermediate the cephalad and caudal ends of straight, curved, and diverging axial bores.