Devices and methods for the treatment of spinal disorders

[0002] The present application claims priority to U.S. patent application Ser. No. 09/542,972, filed Apr. 4, 2000, entitled DEVICES AND METHODS FOR THE TREATMENT OF SPINAL DISORDERS, the entire disclosure of which is hereby incorporated by reference.

[0003] The present invention generally relates to spinal implants. Specifically, the present invention relates to implantable devices and methods for the treatment of spinal disorders associated with the intervertebral disc.

[0004] Back pain is one of the most common and often debilitating conditions affecting millions of people in all walks of life. Today, it is estimated that over ten million people in the United States alone suffer from persistent back pain. Approximately half of those suffering from persistent back pain are afflicted with chronic disabling pain, which seriously compromises a person's quality of life and is the second most common cause of worker absenteeism. Further, the cost of treating chronic back pain is very high, even though the majority of sufferers do not receive treatment due to health risks, limited treatment options and inadequate therapeutic results. Thus, chronic back pain has a significantly adverse effect on a person's quality of life, on industrial productivity, and on heath care expenditures.

[0005] Some forms of back pain are muscular in nature and may be simply treated by rest, posture adjustments and painkillers. For example, some forms of lower back pain (LBP) are very common and may be caused by unusual exertion or injury. Unusual exertion such has heavy lifting or strenuous exercise may result in back strain such as a pulled muscle, sprained muscle, sprained ligament, muscle spasm, or a combination thereof. An injury caused by falling down or a blow to the back may cause bruising. These forms of back pain are typically non-chronic and may be self-treated and cured in a few days or weeks.

[0006] Other types of non-chronic back pain may be treated by improvements in physical condition, posture and/or work conditions. For example, being pregnant, obese or otherwise significantly overweight may cause LBP. A mattress that does not provide adequate support may cause back pain in the morning. Working in an environment lacking good ergonomic design may also cause back pain. In these instances, the back pain may be cured by eliminating the culprit cause. Whether it is excess body weight, a bad mattress, or a bad office chair, these forms of back pain are readily treated.

[0007] However, some forms of back pain are the result of disorders directly related to the spinal column, which are not readily treated. While some pain-causing spinal disorders may be due to facet joint degradation or degradation of individual vertebral masses, disorders associated with the intervertebral discs are predominantly affiliated with chronic back pain (referred to as disc related pain). The exact origin of disc related pain is often uncertain, and although some episodes of disc related pain may be eased with conservative treatments such as bed-rest and physical therapy, future episodes of disc related pain are likely to occur periodically.

[0008] There are a number of suspected causes of disc related pain, and in any given patient, one or more of these causes may be present. However, the ability to accurately diagnose a specific cause or locus of pain is currently difficult. Because of this uncertainty, many of the causes of disc related pain are often lumped together and referred to as degenerative disc disease (DDD).

[0009] A commonly suspected source of disc related pain is physical impingement of the nerve roots emanating from the spinal cord. Such nerve root impingement may have a number of different underlying causes, but nerve root impingement generally results from either a disc protrusion or a narrowing of the intervertebral foramina (which surround the nerve roots).

[0010] As a person ages, their intervertebral discs become progressively dehydrated and malnourished. Together with continued stressing, the disc begins to degenerate. With continued degeneration, or an excessive stressing event, the annulus fibrosus of the disc may tear, forming one or more fissures (also referred to as fractures). Such fissures may progress to larger tears which allow the gelatinous material of the nucleus pulposus to flow out of the nucleus and into the outer aspects of the annulus. The flow of the nucleus pulposus to the outer aspects of the annulus may cause a localized bulge.

[0011] When bulging of the annulus occurs in the posterior portions of the disc, the nerve roots may be directly and physically impinged by the bulge. In more extreme or progressed instances of annular tears, the nuclear material may escape, additionally causing chemical irritation of the nerve roots. Depending on the cause and nature of the disc protrusion, the condition may be referred to as a disc stenosis, a disc bulge, a herniated disc, a prolapsed disc, a ruptured disc, or, if the protrusion separates from the disc, a sequestered disc.

[0012] Dehydration and progressive degeneration of the disc also leads to thinning of the disc. As the height of the disc reduces, the intervertebral foraminae become narrow. Because the nerve roots pass through the intervertebral foraminae, such narrowing may mechanically entrap the nerve roots. This entrapment can cause direct mechanical compression, or may tether the roots, allowing them to be excessively tensioned during body movements.

[0013] Nerve root impingement most often occurs in the lumbar region of the spinal column since the lumbar discs bear significant vertical loads relative to discs in other regions of the spine. In addition, disc protrusions in the lumbar region typically occur posteriorly because the annulus fibrosus is radially thinner on the posterior side than on the anterior side and because normal posture places more compression on the posterior side. Posterior protrusions are particularly problematic since the nerve roots are posteriorly positioned relative to the intervertebral discs. Lower back pain due to nerve root irritation not only results in strong pain in the region of the back adjacent the disc, but may also cause sciatica, or pain radiating down one or both legs. Such pain may also be aggravated by such subtle movements as coughing, bending over, or remaining in a sitting position for an extended period of time.

[0014] Another suspected source of disc related back pain is damage and irritation to the small nerve endings which lie in close proximity to or just within the outer aspects of the annulus of the discs. Again, as the disc degenerates and is subjected to stressing events, the annulus fibrosus may be damaged forming fissures. While these fissures can lead to pain via the mechanisms described above, they may also lead to pain emanating from the small nerve endings in or near the annulus, due to mechanical or chemical irritation at the sites of the fissures. The fissures may continue to irritate the small nerve endings, as their presence cause the disc to become structurally weaker, allowing for more localized straining around the fissures. This results in more relative motion of edges of the fissures, increasing mechanical irritation. Because it is believed that these fissures have only limited healing ability once formed, such irritation may only become progressively worse.

[0015] A common treatment for a disc protrusion is discectomy, a procedure wherein the protruding portion of the disc is surgically removed. However, discectomy procedures have an inherent risk since the portion of the disc to be removed is immediately adjacent the nerve root and any damage to the nerve root is clearly undesirable. Furthermore, discectomy procedures are not always successful long term because scar tissue may form and/or additional disc material may subsequently protrude from the disc space as the disc deteriorates further. The recurrence of a disc protrusion may necessitate a repeat discectomy procedure, along with its inherent clinical risks and less than perfect long term success rate. Thus, a discectomy procedure, at least as a stand-alone procedure, is clearly not an optimal solution.

[0016] Discectomy is also not a viable solution for DDD when no disc protrusion is involved. As mentioned above, DDD causes the entire disc to degenerate, narrowing of the intervertebral space, and shifting of the load to the facet joints. If the facet joints carry a substantial load, the joints may degrade over time and be a different cause of back pain. Furthermore, the narrowed disc space can result in the intervertebral foramina surrounding the nerve roots to directly impinge on one or more nerve roots. Such nerve impingement is very painful and cannot be corrected by a discectomy procedure. Still furthermore, discectomy does not address pain caused by the fissures which may cause direct mechanical irritation to the small nerve endings near or just within the outer aspect of the annulus of a damaged disc.

[0017] As a result, spinal fusion, particularly with the assistance of interbody fusion cages, has become a preferred secondary procedure, and in some instances, a preferred primary procedure. Spinal fusion involves permanently fusing or fixing adjacent vertebrae. Hardware in the form of bars, plates, screws and cages may be utilized in combination with bone graft material to fuse adjacent vertebrae. Spinal fusion may be performed as a stand-alone procedure or may be performed in combination with a discectomy procedure. By placing the adjacent vertebrae in their nominal position and fixing them in place, relative movement therebetween may be significantly reduced and the disc space may be restored to its normal condition. Thus, theoretically, aggravation caused by relative movement between adjacent vertebrae may be reduced if not eliminated.

[0018] However, the success rate of spinal fusion procedures is certainly less than perfect for a number of different reasons, none of which are well understood. In addition, even if spinal fusion procedures are initially successful, they may cause accelerated degeneration of adjacent discs since the adjacent discs must accommodate a greater degree of motion. The degeneration of adjacent discs simply leads to the same problem at a different anatomical location, which is clearly not an optimal solution. Furthermore, spinal fusion procedures are invasive to the disc, risk nerve damage and, depending on the procedural approach, either technically complicated (endoscopic anterior approach), invasive to the bowel (surgical anterior approach), or invasive to the musculature of the back (surgical posterior approach).

[0019] Another procedure that has been less than clinically successful is total disc replacement with a prosthetic disc. This procedure is also very invasive to the disc and, depending on the procedural approach, either invasive to the bowel (surgical anterior approach) or invasive to the musculature of the back (surgical posterior approach). In addition, the procedure may actually complicate matters by creating instability in the spine, and the long term mechanical reliability of prosthetic discs has yet to be demonstrated.

[0020] Many other medical procedures have been proposed to solve the problems associated with disc protrusions. However, many of the proposed procedures have not been clinically proven and some of the allegedly beneficial procedures have controversial clinical data. From the foregoing, it should be apparent that there is a substantial need for improvements in the treatment of spinal disorders, particularly in the treatment of disc related pain associated with a damaged or otherwise unhealthy disc.

[0021] The present invention addresses this need by providing improved devices and methods for the treatment of spinal disorders. The improved devices and methods of the present invention specifically address disc related pain, particularly in the lumbar region, but may have other significant applications not specifically mentioned herein. For purposes of illustration only, and without limitation, the present invention is discussed in detail with reference to the treatment of damaged discs in the lumbar region of the adult human spinal column.

[0022] As will become apparent from the following detailed description, the improved devices and methods of the present invention reduce if not eliminate back pain while maintaining near normal anatomical motion. Specifically, the present invention provides disc reinforcement devices to reinforce a damaged disc, while permitting relative movement of the vertebrae adjacent the damaged disc. The devices of the present invention are particularly well suited for minimally invasive methods of implantation.

[0023] The reinforcement devices of the present invention provide three distinct functions. Firstly, the reinforcement devices mechanically stabilize and strengthen the disc to minimize if not eliminate chronic irritation of nerve roots and nerves around the periphery of the disc annulus. Secondly, the reinforcement devices radially and/or circumferentially compress the disc to close fissures, fractures and tears, thereby preventing the ingress of nerves and potentially facilitating healing. Thirdly, the reinforcement devices may be used to stabilize the posterior disc after a discectomy procedure in order to reduce the need for re-operation.

[0024] In an exemplary embodiment, the present invention provides disc reinforcement therapy (DRT) in which a reinforcement member is implanted in the annulus of an intervertebral disc. The implantation method may be performed by a percutaneous procedure or by a minimally invasive surgical procedure. The present invention provides a number or tools to facilitate percutaneous implantation. One or more reinforcement members may be implanted, for example, posteriorly, anteriorly, and/or laterally, and may be oriented circumferentially or radially. As such, the reinforcement members may be used to stabilize the annulus and/or compresses a portion of the annulus so as to reduce a bulge and/or close a fissure.

[0025] The reinforcement member may be sized to pass through a trocar and may have a tubular cross-section to facilitate advancement over a stylet. The reinforcement member preferably includes a body portion sized to fit in the annulus and an anchor for engaging the annulus and limiting relative movement therebetween. The anchor may be disposed only at the end portions of the body, or may extend over the entire length of the body. The anchor may comprise threads which may have a variable pitch to facilitate compression of the annulus during implantation. The reinforcement member may incorporate chemical and/or biological agents. The reinforcement member may comprise a biocompatible metal such as stainless steel or a super elastic (nickel titanium) alloy. Alternatively, the reinforcement member may comprise a polymer or a reinforced polymeric structure. As a further alternative, the reinforcement member may comprise a bioabsorbable material.

[0026] FIGS. 1A and 1B illustrate left lateral and posterior views, respectively, of a portion of the adult human vertebral (spinal) column;

[0027] FIGS. 2A and 2B illustrate superior (top) views of a healthy disc and a degenerated disc, respectively, and an adjacent vertebral body;

[0028] FIGS. 3A-3D schematically illustrate superior (top) views of reinforcement members disposed in degenerated discs;

[0029] FIGS. 4A-4G schematically illustrate various features that may be incorporated into a straight or curved reinforcement member in accordance with an embodiment of the present invention;

[0030] FIGS. 5A-5C schematically illustrate a circumferential reinforcement member in accordance with an embodiment of the present invention;

[0031] FIGS. 6A-6H schematically illustrate components of a reinforcement member in accordance with an embodiment of the present invention;

[0032] FIGS. 7A-7F illustrate tools of the present invention for implanting the reinforcement members shown in FIGS. 3A and 3B in accordance with the method illustrated in FIGS. 8A-8L;

[0033] FIGS. 8A-8L illustrate a method for implanting the reinforcement members shown in FIGS. 3A and 3B in accordance with an embodiment of the present invention;

[0034] FIGS. 9A-9C illustrate tools of the present invention for implanting the reinforcement member shown in FIG. 3C in accordance with the method illustrated in FIGS. 10A-10H;

[0035] FIGS. 10A-10H illustrate a method for implanting the reinforcement member shown in FIG. 3C in accordance with an embodiment of the present invention;

[0036] FIGS. 11A-11H illustrate a method for implanting the reinforcement member shown in FIG. 3D in accordance with an embodiment of the present invention;

[0037] FIGS. 12A-12J illustrate steps for implanting a self-expanding reinforcement member;

[0038] FIGS. 12K-12L illustrate steps for implanting an inflatable reinforcement member; and

[0039] FIGS. 12M-12R illustrate steps for implanting a reinforcement bar.

[0040] The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.

[0041] With reference to FIGS. 1A and 1B, the lower portion of an adult human vertebral column 10 is illustrated in left lateral and posterior views, respectively. The upper portion of the vertebral column 10 includes the thoracic region and the cervical region, which are not shown for purposes of simplified illustration only. The lower portion of the vertebral column 10 includes the lumbar region 12, the sacrum 14 and the coccyx 16. The sacrum 14 and the coccyx 16 are sometimes collectively referred to as the pelvic curvature.

[0042] The vertebral column 10 includes an axis of curvature 60 which generally forms a double-S shape when viewed laterally. The vertebral column 10 also includes a median plane 70 which is a sagittal plane bisecting the vertebral column 10 into symmetrical left lateral and right lateral portions. In posterior views, the median plane 70 appears as a line.

[0043] The lumbar region 12 of the vertebral column 10 includes five (5) vertebrae 20 (labeled L1, L2, L3, L4 and L5) separated by intervertebral discs 50. The sacrum 14, which includes five (5) fused vertebrae 30 (superior vertebra 30 labeled S1), is separated by a single disc 50 from the coccyx 16, which includes four (4) fused vertebrae 40. Although not labeled, the intervertebral discs 50 may be referenced by their respective adjacent vertebrae. For example, the disc 50 between the L4 and L5 lumbar vertebrae 20 may be referred to as the L4L5 disc. Similarly, the disc 50 between the L5 lumbar vertebra 20 and the S1 sacral vertebra 30 may be referred to as the L5S1 disc.

[0044] Although each vertebra 20/30/40 is a unique and irregular bone structure, the vertebrae 20 of the lumbar region 12 (in addition to the thoracic and cervical regions) have common structures. Each vertebra 20 of the lumbar region 12 generally includes a body portion 21 and a vertebral arch portion 22/23 which encloses the vertebral foramen (not visible) in which the spinal cord is disposed. The vertebral arch 22/23 includes two pedicles 22 and two laminae 23. A spinous process 24 extends posteriorly from the juncture of the two laminae 23, and two transverse processes 25 extend laterally from each lamina 23. Four articular processes 26/27 extend inferiorly 26 and superiorly 27 from the laminae 23. The inferior articular process 26 rests in the superior articular process 27 of the adjacent vertebra to form a facet joint 28.

[0045] The five (5) vertebrae 30 of the sacrum 14 are fused together to form a single rigid structure. The sacrum 14 includes a median sacral crest 31 which roughly corresponds to the spinous processes of the vertebrae 30, and two intermediate sacral crests 32 which roughly correspond to the articular processes of the vertebrae 30. The sacral laminae 33 are disposed between the median 31 and intermediate 32 sacral crests. Two lateral sacral crests 34 are disposed on either side of the sacral foraminae 35. The sacrum 14 also includes a pair of sacral wings 36 which define auricular surfaces 39. The superior (S1) sacral vertebra 30 includes two superior articular processes 37 which engage the inferior articular processes 26 of the L5 lumber vertebra 20 to form a facet joint, and the base 38 of the superior sacral vertebra S1 is joined to the L5S1 disc 50.

[0046] With reference to FIG. 2A, each intervertebral disc 50 includes an annulus fibrosus 52 surrounding a nucleus pulposus 54. The posterior annulus 52 is generally thinner than the anterior annulus 52, which may account for the higher incidence of posterior disc protrusions. The annulus fibrosus 52 comprises about 60% of the total disc 50 cross-sectional area, and the nucleus pulposus 54 only comprises about 40% of the total disc 50 cross-sectional area. The annulus fibrosus 52 comprises 40-60% organized collagen in the form of a laminated structure. The nucleus pulposus 54 comprises 18-30% collagen in the form of a relatively homogenous gel.

[0047] A common theory is that each intervertebral disc 50 forms one support point and the facet joints 28 form two support points of what may be characterized as a three point support structure between adjacent vertebrae 20. However, in the lumbar region 12, the facet joints 28 are substantially vertical, leaving the disc 50 to carry the vast majority of the load. As between the annulus fibrosus 52 and the nucleus pulposus 54 of the disc 50, it is commonly believed that the nucleus 54 bears the majority of the load. This belief is based on the theory that the disc 50 behaves much like a balloon or tire, wherein the annulus 52 merely serves to contain the pressurized nucleus 54, and the nucleus 54 bears all the load. However, this theory is questionable since the annulus fibrosus 52 comprises 60% of the total disc 50 cross-sectional area and is made of 40-60% organized collagen in the form of a laminated structure. By contrast, the nucleus pulposus 54 only comprises 40% of the total disc 50 cross-section and is made of 18-30% collagen in the form of a relatively homogenous gel. Thus, a more plausible theory is that the annulus fibrosus 52 is the primary load bearing portion of the disc 50.

[0048] With reference to FIG. 2B, the intervertebral discs 50 become progressively dehydrated and malnourished with age. When combined with continued stressing, the disc begins to degenerate. With continued degeneration, or an excessive stressing event, the annulus fibrosus of the disc may tear, forming one or more radial fissures 56 or circumferential fissures 58, which may progress to larger tears. Larger tears may allow the gelatinous material of the nucleus pulposus 54 to flow out of the nucleus and into the outer aspects of the annulus 52. The flow of the nucleus pulposus 54 to the outer aspects of the annulus 52 may cause a localized bulge 60. A posterior bulge 60 may result in direct impingement of a nerve root (not shown). Nuclear material that escapes through an advanced tear may cause further mechanical irritation and additionally cause chemical irritation of a nerve root. A nerve root may also be compressed or tethered by a narrowing of the intervertebral foraminae, resulting from a loss in disc height caused by sustained degeneration of the disc 50. Small nerve endings (not shown) in or near the perimeter of the annulus 52 may also be mechanically or chemically irritated at the sites of the fissures 56/58. In all cases, degeneration of the disc eventually leads to disc related pain of some origin.

[0049] FIGS. 3A-3D schematically illustrate reinforcement members 100/200/300 implanted in a degenerated disc 50. In all instances, the reinforcement members 100/200/300 mechanically stabilize and strengthen the disc 50 to minimize if not eliminate chronic irritation of nerve roots and nerves around the periphery of the disc annulus 52. As can be seen in FIGS. 3A-3D, the reinforcement members 100/200/300 also radially and/or circumferentially compress the disc 50 to close fissures 56/58, thereby preventing the ingress of nerves and potentially facilitating healing. The reinforcement members 100/200/300 may further be used to stabilize the posterior portion of the disc 50 after a discectomy procedure in order to reduce the need for re-operation.

[0050] FIGS. 3A-3D show examples of where the reinforcement members 100/200/300 may be implanted in the annulus 52. However, the reinforcement members 100/200/300 may be implanted in any portion of the annulus 52 including, without limitation, the posterior, anterior or lateral portions thereof. Because most disc related pain is associated with damage to the posterior portion of the disc 50, the reinforcement members 100/200/300 preferably provide support to the posterior portion of the annulus 52 and establish anchor points in the lateral and anterior portions of the annulus 52. The reinforcement members 100/200/300 may be used individually as shown in FIGS. 3A, 3C and 3D; or in combination as shown in FIG. 3B. Although not shown, any combination of the different types of reinforcement members 100/200/300 may be utilized.

[0051] The reinforcement members 100/200/300 may be oriented generally parallel to the periphery of the annulus 52 (e.g., reinforcement members 100A, 100C, 200, 300), generally radial to the annulus 52 (e.g., reinforcement member 100B), or any other orientation suitable for stabilizing and/or compressing the desired portion(s) of the annulus 52. Generally, the closer the reinforcement members 100/200/300 are to the periphery of the annulus 52, the greater the amount of support and stabilization provided to the disc 50. As such, the reinforcement members 100/200/300 preferably have a curvature conforming to the periphery of the annulus 52 such that they may be implanted as close to the periphery of the annulus 52 as possible. The reinforcement members 100/200/300 may have such a curvature in the relaxed (zero stress) state, or the curvature may be imparted by the insertion path or defined by the insertion tools used.

[0052] The reinforcement members 100/200/300 may extend across and close fissures 56/58 as shown, or any other portion of the annulus 52 to provide compression and stabilization of the disc 50. Although not shown, the reinforcement members 100/200/300 may extend across or into the nucleus 54. In such a case, it is preferred that the reinforcement members 100/200/300 do not extend outside the periphery of the annulus 52 in order to reduce the probability of nuclear material escaping from the outer aspects of the annulus 52.

[0053] The reinforcement members 100/200/300 are sized to fit within the annulus 52 of a human disc 50. Thus, the collective diameter and length of the reinforcement members 100/200/300 implanted preferably does not exceed the height and circumference/diameter, respectively, of the annulus 52, depending on the number and orientation of the reinforcement members 100/200/300 implanted. The reinforcement members 100/200/300 may be made of a biocompatible material or coated with a biocompatible material. Suitable structural materials for the reinforcement members 100/200/300 include stainless steel and super elastic alloys such as nickel titanium. All or a portion of the reinforcement members 100/200/300 may be made of biodegradable or bioabsorbable material such as resorbable collagen, LPLA (poly(1-lactide)), DLPLA (poly(dl-lactide)), LPLA-DLPLA, PGA (polyglycolide), PGA-LPLA or PGA-DLPLA. Other metals, alloys, polymers, and composites having suitable tensile, compression and fatigue strength and elasticity may also be used. The reinforcement members 100/200/300 may further include growth factors to facilitate healing, agents which render nuclear matter inert or otherwise reduce chemical irritation thereof, and/or anesthetic agents to reduce nerve signal transmission (i.e., pain).

[0054] In all embodiments, various visualization techniques may be used to facilitate implantation of the reinforcement members 100/200/300. For example, real time CT scanning, real time MR imaging, or a combination of preoperative CT or MR images superimposed onto a real time device tracking images such as the system commercially available under the trade name STEALTH™ available from Sofamor Danek.

[0055] FIGS. 4A-4G illustrate various embodiments of the reinforcement member 100 in accordance with the present invention. The embodiments of FIGS. 4A-4G illustrate various features which may be combined in any way to provide the desired reinforcement member 100. Reinforcement member 100 may be sized and oriented as shown and discussed with reference to FIGS. 3A and 3B. Reinforcement member 100 includes a body portion 110 and an anchor 120. The anchor 120 serves to immobilize or limit movement of the reinforcement member 100 relative to the annulus 52.

[0056] In FIGS. 4A, 4D and 4F, the anchor is in the form of threads 122 disposed about the periphery of the body portion 110, which behave like threads on a screw and engage the annulus 52 upon rotation therein. When threads 122 are used, the proximal end of the body 110 may include slots 116 as shown in FIG. 4C, which is an end view taken along line 4C—4C in FIG. 4A. The slots 116, or any other suitable mating geometry, facilitate rotation with a driver having a mating distal end. In FIG. 4E, the anchor 120 is in the form of sloped rings 124 spaced along the length of the body portion 110, which behave like rings on a ring-shank nail to engage the annulus 52 upon pushing therein. Those skilled in the art will recognize that other anchor 120 mechanisms such as barbs, expandable anchors, etc. may also be used.

[0057] The anchor 120 may extend the full length of the body portion 110 as shown in FIGS. 4A and 4F, or may be disposed only on proximal and distal portions of the body as shown in FIGS. 4D and 4E. The body portion 110 may be tubular defining a lumen 112 extending therethrough as shown in FIG. 4B, which is a cross-sectional view taken along line 4B—4B in FIG. 4A. The lumen 112 facilitates advancement of the reinforcement member 100 over a stylet to facilitate insertion into the annulus 52, as will be discussed in greater detail hereinafter. Alternatively, the body portion 110 may have a solid cross-section as shown in FIG. 4G, which is a cross-sectional view taken along line 4G—4G in FIG. 4F. In this alternative embodiment, the solid cross-section body portion 110 may include a sharpened distal tip 114 as shown in FIG. 4F to facilitate insertion into the annulus 52.

[0058] Preferably, the threads 122 have a variable pitch such that the annulus is compressed as the reinforcement member 100 is rotated and advanced into the annulus 52. Variable pitch threads 122, as shown in FIGS. 4A, 4D and 4F, generally have a larger pitch at the distal end of the body 110 and a smaller pitch at the proximal end of the body 110. The larger pitch distal threads 122 pull the annular tissue 52 a greater distance per revolution than the smaller pitch proximal threads 122. Thus, as the reinforcement member 100 is rotated and advanced into the annulus 52, the distal threads pull the annular tissue together and the proximal threads hold the tissue in place thereby compressing the annulus 52. By compressing the annulus 52, the disc 50 is mechanically stabilized and the fissures 56/58 are closed to facilitated healing.

[0059] Although compression of the annulus 52 is preferred, it is not necessary to have compression in order to provide some degree of mechanical stabilization. To the extent that compression is desired, the variable pitch threads 122 mentioned above are currently preferred. However, other compression techniques are equally useful. For example, standard constant pitch threads 122 and tapered rings 124 may achieve compression by utilizing a step-wise advancement and tension technique as will be described in more detail hereinafter.

[0060] FIGS. 5A-5C schematically illustrate a circumferential reinforcement member 200, which is generally the same as reinforcement member 100 except as described herein. FIG. 5B is a cross-sectional view taken along line 5B—5B in FIG. 5A, and FIG. 5C is an end view taken along line 5C—5C in FIG. 5A. The circumferential reinforcement member 200 includes a tubular body 210 defining a lumen 212 to facilitate advancement over a stylet. The circumferential reinforcement member 200 also includes an anchor 220, preferably in the form of variable pitch threads 222. The proximal end of the body 210 the may include slots 216 or other suitable mating geometry to facilitate rotation by a driver having a mating distal end. Any of the variants of reinforcement member 100 discussed with reference to FIGS. 4A-4G may be applied to circumferential reinforcement member 200.

[0061] The circumferential reinforcement member 200 may have a geometry (e.g., circle, ellipse, oval, etc.) corresponding to the geometry of the outer aspects of a healthy annulus 52, or the member 200 may be naturally straight, taking on a curved shape during implantation. Because the circumferential reinforcement member 200 is implanted in the annulus 52 around the entire periphery thereof, the reinforcement member maximizes anchoring strength and provides superior stabilization around the entire disc 50. Thus, it is preferable that the reinforcement member 200 define a closed geometry once implanted, or even have overlapping ends, but an open geometry (e.g., semi-ellipse or semi-circle) may also be employed. The size and shape of the reinforcement member 200 may be pre-selected to accommodate anatomical variations of the annulus 52 between patients. The reinforcement member may have a relaxed size that is smaller than the implanted size such that additional radial and circumferential compression is achieved.

[0062] FIGS. 6A-6H schematically illustrate reinforcement member 300, including a pair of tubular pins 310, two screws 320 and two connecting rings 330 which may be assembled as shown in FIG. 6F. With reference to FIG. 6A, each of the tubular pins 310 includes a shaft portion 312, a head portion 314 and a connection mechanism 318. The shaft 312 is sized to fit within a hole of the connection ring 330 and the head 314 is sized larger than the same hole. The connection mechanism 318 may comprises a threaded shaft insertable into a threaded hole as shown, or any other known mechanical releasable connection that maintains the profile of the shaft portion 312. As seen in FIG. 6B, which is a cross-sectional view taken along line 6B—6B in FIG. 6A, the shaft portion 312 includes a lumen 313 to facilitate advancement over a stylet. The heads 314 may each include a slot 316 as seen in FIG. 6C, which is an end view taken along line 6C—6C in FIG. 6A, or other suitable geometry to mate with a distal end of a driver to facilitate rotation of the pins 310 to screw the releasable connection together.

[0063] The screws 320 include a shaft 322, a head 324, threads 328 and a sharpened tip 323 as seen in FIG. 6D. The screws 320 may comprise a wide variety of orthopedic screw designs, particularly those suitable for implantation into cartilage and other collagen-based tissues. The shaft 322 and threads 326 are sized to fit within a hole of the connection ring 330 and the head 324 is sized larger than the same hole. The head 324 includes slots 326 as seen in FIG. 6E, which is an end view taken along line 6E—6E in FIG. 6D, or other suitable mating geometry to facilitate rotation by a driver having a mating distal end.

[0064] The connection rings 330 each have first and second rings 331/333 defining first and second holes 332/334 as shown in FIG. 6F. The first hole 332 is sized to provide a sliding fit about the shaft 312 of the pins 310 and the second hole is sized to provide a sliding fit about the shaft 322 and threads 326 of the screws 320. As seen in the side view shown in FIG. 6G, each of the connection rings 330 also define an angle 336 between the rings 331/333 to accommodate the implanted arrangement as shown in FIG. 6H.

[0065] Referring now to FIGS. 7A-7F, various tools 410, 420, 430 and 440 are shown individually and assembled. The tools 410, 420, 430 and 440 may be used to implant the reinforcement members 100 discussed above. The tools include a rigid, sharpened, hollow trocar 410 as shown in FIG. 7A, a semi-rigid, sharpened, hollow curved needle 420 as shown in FIG. 7B, a sharpened curved stylet 430 as shown in FIG. 7C, and a hollow driver 440 as shown in FIG. 7D. As seen in FIG. 7E, the sharpened stylet 430 fits into the semi-rigid needle 420 which fits into the rigid trocar 410. As seen in FIG. 7F, the sharpened stylet 430 fits into the hollow driver 440 which fits into the rigid trocar 410.

[0066] With specific reference to FIG. 7A, the rigid hollow trocar 410 includes a hollow shaft 412 and a grip or handle 414. The shaft 412 includes a sharpened tip 413 to facilitate passage through the skin and back muscles, and insertion into the annulus 52. The shaft 412 is preferably made of a rigid metal such as a stainless steel hypodermic tube. The grip 414 may comprise a polymer and may be formed by insert injection molding with the shaft 412 inserted into the mold.

[0067] With specific reference to FIG. 7B, the semi-rigid curved needle 420 includes a hollow shaft 422 a hub 424. The shaft 422, which includes a sharpened tip 423, is longer than the rigid trocar 410 and has an outside diameter sufficiently small to fit into the rigid trocar 410. The shaft 422 is preferably made of a semi-rigid polymer or composite. The shaft 422 includes a curved distal portion 426 that may be straightened (shown in phantom) upon insertion of the semi-rigid needle 420 into the lumen of the rigid trocar 410. The hub 424 may include a fitting 425 to facilitate connection to a fluid source or a pressure source (e.g., a syringe).

[0068] With specific reference to FIG. 7C, the sharpened curved stylet 430 includes a flexible shaft 432 and a sharpened distal end 433. The distal tip 433 may optionally include an anchor 435 such as threads, tapered rings or barbs to facilitate the step-wise advancement and tension technique as will be described in detail hereinafter. If threads are used for the anchor 435, the curvature 434 of the distal portion of the shaft 432 may be eliminated to facilitate efficient torque transfer. The shaft 432 includes a curve 434 which approximates the curvature and diameter of the outer aspects of the annulus where the reinforcement member 100 is to be implanted. The shaft 432 is longer than the both the rigid trocar 410 and the semi-rigid needle 420, and may have a length on the order of 10 to 60 cm. The shaft 432 also has an outside diameter sufficiently small to fit into the semi-rigid needle 420. The shaft 422 preferably has a flexible but pushable construction incorporating a rigid metal such as stainless steel, or super-elastic nickel-titanium alloy. The sharpened stylet 430 is preferably highly elastic, to resist permanent set upon insertion into the curved portion 426 of the semi-rigid needle 420.

[0069] With specific reference to FIG. 7D, the hollow driver 440 includes a hollow shaft 442 and a grip or handle 444. The distal end of the hollow shaft 442 includes a tip 446 defining a geometry which mates with an end of the reinforcement member 100 to facilitate rotation thereof during implantation. The shaft 442 is preferably made of a torsionally rigid metal such as a stainless tool steel. The grip 444 may comprise a polymer and may be formed by insert injection molding with the shaft 442 inserted into the mold.

[0070] With general reference to FIGS. 8A-8L, the steps for implanting reinforcement member 100 are illustrated. It should be understood that the procedure for implanting a single member 100 in the posterior portion of the annulus 52 is shown for purposes of illustration, not limitation. All of the variables with regard to quantity, location, orientation, etc. discussed previously may be implemented by varying the generic procedure described hereinafter.

[0071] The method illustrated in FIGS. 8A-8L is a percutaneous procedure in which access to the disc 50 is achieved utilizing a number of small diameter tools which may be inserted through a patient's back (skin and back muscles), between adjacent vertebrae, and into the patient's disc 50. This percutaneous method minimizes the invasiveness of the procedure thereby reducing procedure time, procedure cost, postoperative pain and recovery time.

[0072] Initially, as shown in FIG. 8A, the rigid trocar 410 is positioned for insertion into the disc 50 as in a conventional discogram procedure. The rigid trocar 410 is advanced until the distal tip 413 of the trocar 410 is proximate the outer periphery of the posterior portion of the annulus 52 as seen in FIG. 8B.

[0073] The curved portion 426 of the semi-rigid needle 420 is straightened for insertion into the trocar 410 as shown in FIG. 8C. The semi-rigid needle 420 (alone or with stylet 430) is advanced relative to the rigid trocar 410 until the curved portion 426 of the semi-rigid needle exits the distal tip 413 of the rigid trocar 410 and the desired amount of curvature is established, as seen in FIG. 8D. The curved portion 426 may be advanced until the tip 423 is roughly parallel to the posterior curvature of the annulus 52.

[0074] The sharpened stylet 430 is then positioned for insertion into the semi-rigid needle 420 as shown in FIG. 8E. The sharpened stylet 430 is advanced relative to the semi-rigid needle 420 until the distal tip 433 of the stylet 430 extends across radial fissures 56, as shown in FIG. 8F.

[0075] The semi-rigid curved needle 420 is removed from the stylet 430 and trocar 410, and the reinforcement member 100 is positioned for advancement over the stylet 430 as shown in FIG. 8G. The reinforcement member 100 is advanced over the stylet 430 and into the trocar 410, and the driver 440 is positioned for advancement over the stylet 430 as shown in FIG. 8H. The driver 440 is then rotated and advanced over the stylet 430 in order to rotate and push the reinforcement member 100 into the annulus and across the radial fissures 56 as seen in FIG. 8I. If the reinforcement member 100 utilizes an anchor other than threads, the driver 440 may be used to simply push or otherwise advance the reinforcement member 100 through the trocar 410 and into the annulus 52.

[0076] If a solid cross-section reinforcement member 100 is utilized, it is not necessary to utilize the stylet 430. In this situation, the curved semi-rigid needle 420 is left in place as shown in FIG. 8E and the solid cross-section reinforcement member 100 is advanced therethrough. The driver 440 is then rotated and advanced through the curved semi-rigid needle 420 in order to rotate and push the reinforcement member 100 into the annulus 52 and across the radial fissures 56. In this alternative method, it may be necessary to resize the curved semi-rigid needle 420 to accommodate the driver 440 and reinforcement member 100.

[0077] The variable pitch threads on the reinforcement member 100 compress the disc 50 and cause the fissures 56 to close as discussed previously. If variable pitch threads are not utilized on the reinforcement member 100, other techniques may be used to compress the disc 50 and close the radial fissures 56. An example of an alternative disc 50 compression technique is a step-wise advancement and tension method. In this alternative method, the distal tip 433 of the stylet 430 is incorporated with an anchor 435 such as threads. After the distal tip 433 of the stylet 430 has been advanced by rotation to extend across the fissures 56, and before the reinforcement member 100 has been advanced into the annulus 52, the stylet is pulled in the proximal direction to apply tension thereto. Because the threaded anchor at the distal end 433 of the stylet 430 grips the annulus 52, tension applied to the stylet 430 compresses a portion of the disc 50 and closes the fissures 56. Once compression of the disc 50 and closure of the fissures 56 are established, the reinforcement member 100 may be advanced into the annulus 52 to maintain disc 50 compression and hold the fissures 56 closed. This method of step-wise advancement and tension may be repeated until the reinforcement member 100 is fully implanted in the desired position within the annulus 52.

[0078] After the reinforcement member 100 is positioned across the radial fissures 56 as shown in FIG. 8I, the stylet is advanced until the distal tip extends across the circumferential fissure 58 as shown in FIG. 8J. Note that the curvature 434 of the stylet 430 defines the insertion path of the reinforcement member 100. It has been observed that the preset curvature 434 of the stylet 430 will correspond to the insertion path if the tip 433 is very sharp. With the stylet 430 advanced such that the tip extends across fissure 58, the driver 440 is then used to rotate and advance the reinforcement member 100 across the fissure 58 as shown in FIG. 8K. The variable pitch threads on the reinforcement member 100 compress the disc 50 and cause the fissure 58 to close as discussed previously. Once the reinforcement member 100 is completely deployed within the annulus 52 as shown in FIG. 8L, the tools 410/430/440 may be removed from the patient and the procedure is essentially complete.

[0079] With general reference to FIGS. 9A-9C, schematic illustrations of additional tools 450/460 for use in the method of implanting reinforcement member 200 are shown. The additional tools include a variable curvature stylet 450 as shown in FIG. 9A and a stiffening mandrel 460 as shown in FIG. 9B. The variable curvature stylet 450 is hollow which permits insertion of the stiffening mandrel 460 as shown in FIG. 9C.

[0080] The variable curvature stylet 450 includes a tubular shaft 452, a curved distal portion 454 and a closed distal end 453 which is sharpened. The variable curvature stylet 450 is substantially the same as the curved stylet 430 described previously, except for the provision of a lumen into which the stiffening mandrel 460 is insertable. The stiffening mandrel 460 includes an elongate shaft 462 and a blunt tip 463. The shaft 462 and tip 463 of the stiffening mandrel 460 are sized to be inserted into the hollow shaft 452 of the stylet 450. The hollow stylet 450 and the stiffening mandrel 460 may be made of stainless steel, nickel titanium alloy or the like.

[0081] Upon insertion of the stiffening mandrel 460 into the hollow stylet 450, the curvature increases as can be seen from a comparison of FIGS. 9A and 9C. Preferably the stiffening mandrel 460 is inserted fully into the hollow stylet 450 to increase the radius of curvature of the distal portion of the curvature 454, since the distal portion of the curvature 454 dictates the path that the stylet 450 will follow. The relative stiffness of the stylet 450 and stiffening mandrel 460 may be selected to vary the amount of change in the curvature 454. The variable curvature 454 may be used to navigate around the changing curvature of the annulus 52 as described hereinafter. At any point during advancement of the stylet 450, the curvature 454 may be adjusted by insertion of an appropriately stiff mandrel 460. The path defined by the stylet 450 may thus be customized to any particular disc 50 anatomy.

[0082] With general reference to FIGS. 10A-10H, the steps for implanting circumferential reinforcement member 200 are illustrated. All of the variables with regard to quantity, location, orientation, etc. discussed previously may be implemented by varying the generic procedure described hereinafter. The method illustrated in FIGS. 10A-10H is a percutaneous procedure in which access to the disc 50 is achieved utilizing a number of small diameter tools which may be inserted through a patient's back (skin and back muscles), between adjacent vertebrae, and into the patient's disc 50.

[0083] Initially, as shown in FIG. 10A, the rigid trocar 410 is advanced into the annulus 52 of the disc 50. The trocar 410 is advanced until the distal tip 413 thereof is disposed in the lateral portion of the annulus 52 roughly half way between the posterior and anterior portions of the annulus 52 as seen in FIG. 10B. The hollow curved stylet 450 with the stiffening mandrel 460 inserted therein is then advanced into the trocar 410. Note that an appropriate stiff mandrel 460 has been fully inserted into the hollow stylet 450 a sufficient distance to define a curvature 454 that approximates the curvature of the anterior portion of the annulus 52. Continued advancement of the hollow stylet 450 and stiffening mandrel 460 as a unit cause the stylet 450 to traverse the anterior portion of the annulus 52 as shown in FIG. 10C.

[0084] After the distal tip 453 of the stylet 450 is positioned roughly half way between the posterior and anterior portions of the annulus 52 as seen in FIG. 10C, the stiffening mandrel 460 is retracted or removed from the stylet 450 to define a smaller curvature 454 that approximates the curvature of the posterior lateral portion of the annulus 52. The stylet 450 is then advanced until the distal tip 453 thereof enters the posterior portion of the annulus 52 as shown in FIG. 10D.

[0085] An appropriately stiff mandrel 460 is then advanced or inserted into the hollow stylet 450 to define a curvature 454 that approximates the curvature of the posterior portion of the annulus 52. The stylet is then advanced across the posterior portion of the annulus 52. The stiffening mandrel 460 is then retracted or removed from the stylet 450 to define a smaller curvature 454 that approximates the curvature of the posterior lateral portion of the annulus 52. The stylet 450 is then advanced until the distal tip 453 thereof is positioned adjacent the distal tip 413 of the trocar 410 as shown in FIG. 10E.

[0086] The trocar 410 is then removed from the patient leaving the stylet 450 in the annulus 52 to define the insertion path for the reinforcement member 200 as shown in FIG. 10F. The circumferential reinforcement member 200 and driver 440 are then advanced over the stylet 450 as shown in FIG. 10G. Using the driver 440 to push and rotate the circumferential reinforcement member 200, the member 200 is advanced into the annulus 52 along the path defined by the stylet 450 until the distal end of the reinforcement member 200 is adjacent the proximal end of the reinforcement member 200. Note that the variable pitch threads 222 compress the disc 50 and cause the fissure 56/58 to close. If the reinforcement member 200 includes an anchor 220 other than threads (e.g., sloped rings, barbs, etc.) the driver 440 may be used to simply push the reinforcement member 200 into the annulus 52. Once the reinforcement member 200 is in the desired position, the driver 440 and stylet 450 may be removed from the patient to complete the procedure.

[0087] With general reference to FIGS. 11A-11H, the steps for implanting reinforcement member 300 are illustrated. All of the variables with regard to quantity, location, orientation, etc. discussed previously may be implemented by varying the generic procedure described hereinafter. The method illustrated in FIGS. 11A-11H is a percutaneous procedure in which access to the disc 50 is achieved utilizing a number of small diameter tools which may be inserted through a patient's back (skin and back muscles), between adjacent vertebrae, and into the patient's disc 50.

[0088] Initially, as shown in FIG. 11A, two trocars 410 are positioned for insertion into the disc 50. The trocars 410 are advanced until the distal tip 413 of each trocar 410 is proximate the outer periphery of the posterior portion of the annulus 52 as seen in FIG. 11B. The curved stylet 430 is then advanced into one of the trocars 410 and advanced into the annulus 52 as shown in FIG. 11C. The curved stylet 430 is then advanced across the posterior annulus 52, into the distal tip 413 of the other trocar 410, and out the proximal end of the other trocar 410 as shown in FIG. 11D. The curvature 434 of the stylet 430 is selected such that the tip 433 of the stylet 430 traverses the posterior portion of the annulus 52 and automatically enters into the other trocar 410. To facilitate automatic insertion of the stylet into the other trocar 410, the inside diameter of the trocar 410 may be tapered to increase the inside diameter closer to the tip 413. As mentioned previously, the stylet 430 will follow a path in the annulus 52 corresponding to the curvature 434 of the stylet 430 if the tip 433 is very sharp.

[0089] The trocars 410 are then removed from the patient leaving the stylet 430 in place as shown in FIG. 11E. Also as shown in FIG. 11E, the screws 320 are placed in the holes 334 of the connection rings 330, and the connection rings 330 are slid onto the stylet 430 through holes 332. The screws 320 are then screwed into the annulus 52 as shown in FIG. 11F using a conventional driver (not shown). Placing the screws 320 in the lateral portions of the annulus 52 takes advantage of the generally greater integrity (usually thicker and healthier) of the lateral portions of the annulus 52 to establish firm anchor points.

[0090] Also as shown in FIG. 11F, the tubular pins 310 are positioned on the stylet 430. The tubular pins 310 are then advanced over the stylet 430, across the posterior portion of the annulus 52, and screwed together as shown in FIG. 11G using driver 440 (not shown). The pins 310 have an assembled length which is shorter than the length of the stylet traversing the annulus 52 such that connection of the pins 310 causes compression of the disc 50 and closure of the fissures 56/58. After removal of the stylet 430, the screws 320 may be tightened further into the annulus 52 in order to further compress the disc 50 and close the fissures 56/58 as shown in FIG. 11H.

[0091] With general reference to FIGS. 12A-12R, alternative embodiments of reinforcement members and methods of implantation are disclosed. The reinforcement members 510/520/530 may be used to reinforce the disc, restore disc height and/or bear some or all of the load normally carried by the annulus. The reinforcement members 510/520/530 are relatively rigid and thus serve to reinforce the disc 50, and particularly the annulus 52, where inserted. In addition, the reinforcement members 510/520/530 may have a relatively large profile when implanted and thus increase disc height.

[0092] The reinforcing members 510/520/530 may be used singularly or in groups, depending on the increase in disc 50 height desired and/or the amount of reinforcement of the annulus 52 desired. For example, the reinforcing members 510/520/530 may be stacked or inserted side-by-side. In addition, the reinforcing members 510/520/530 may be located in virtually any portion of the annulus 52. Preferably, the reinforcing members 510/520/530 are substantially symmetrically disposed about the median plane 70 to avoid causing curvature of the spine 10. Although the reinforcing members 510/520/530 may be inserted, in part or in whole, into the nucleus 54, it is preferable to insert them into the annulus 52 for purposes of stability and load carrying. Specifically, to provide stability, it is desirable to symmetrically locate the reinforcing members 510/520/530 as far as reasonably possible from the median plane 70, or to span as great a distance as possible across the median plane 70. In addition, because the annulus 52 of the disc 50 is believed to carry the majority of the load, particularly in the lumbar region 12, the reinforcing members 510/520/530 are preferably placed in the annulus 52 to assume the load normally carried thereby, and reinforce the load bearing capacity of the annulus 52, without hindering the normal mobility function of the disc 50.

[0093] The reinforcing members 510/520/530 may comprise expandable members such as self-expanding members 510 or inflatable members 520. Alternatively, the reinforcing members 510/520/530 may comprise unexpandable members such as reinforcement bars 530. When implanting each type of reinforcement member 510/520/530, it is preferable to maintain the integrity of the annulus 52. Accordingly, space in the annulus 52 for the reinforcing members 510/520/530 is preferably established by dilation or the like, although some amount of tissue removal may be used.

[0094] The expandable reinforcement members 510/520 are useful because they may be delivered in a low profile, unexpanded condition making it easier to traverse the very tough and fibrous collagen tissue of the annulus 52. For similar reasons, the reinforcement bars 530 are useful because they may have a small diameter and a sharpened tip. Although it is possible to insert the expandable reinforcing members 510/520 into the annulus 52 in their final expanded state, it is desirable to deliver the expandable reinforcing members 510/520 into the annulus 52 in an unexpanded state and subsequently expand them in order to minimize invasiveness and resistance to insertion.

[0095] The self-expanding reinforcing member 510 may comprise a solid or semi-solid member that self-expands (e.g., by hydration) after insertion into the annulus. Examples of suitable materials for such solid or semi-solid members include solid fibrous collagen or other suitable hard hydrophilic biocompatible material. If the selected material is degradable, the material may induce the formation of fibrous scar tissue which is favorable. If non-degradable material is selected, the material must be rigid and bio-inert. The self-expanding reinforcing member 510 preferably has an initial diameter that is minimized, but may be in the range of 25% to 75% of the final expanded diameter, which may be in the range of 0.3 to 0.75 cm, or 10% to 75% of the nominal disc height. The length of the self-expanding member 510 may be in the range of 1.0 to 6.0 cm, and preferably in the range of 2.0 to 4.0 cm.

[0096] The inflatable reinforcing member 520 may comprise an expandable hollow membrane capable of inflation after insertion into the annulus. An example of a suitable inflatable structure is detachable balloon membrane filled with a curable material. The membrane may consist of a biocompatible and bio-inert polymer material, such as polyurethane, silicone, or polycarbonate-polyurethane (e.g., Corethane). The curable filler material may consist of a curable silicone or polyurethane. The filler material may be curable by chemical reaction (e.g., moisture), photo-activation (e.g., UV light) or the like. The cure time is preferably sufficiently long to enable activation just prior to insertion (i.e., outside the body) and permit sufficient time for navigation and positioning of the member 520 in the disc. However, activation may also take place inside the body after implantation. The inflatable reinforcing member 520 preferably has an initial deflated diameter that is minimized, but may be in the range of 25% to 75% of the final inflated diameter, which may be in the range of 0.3 to 0.75 cm, or 10% to 75% of the nominal disc height. The length of the inflatable member 520 may be in the range of 1.0 to 6.0 cm, and preferably in the range of 2.0 to 4.0 cm.

[0097] The reinforcement bars 530 may comprise a rigid, solid or hollow bar having a sharpened tip. The reinforcement bars 530 may comprises stainless steel mandrels, for example, having a diameter in the range of 0.005 to 0.100 inches, preferably in the range of 0.010 to 0.050 inches, and most preferably in the range of 0.020 to 0.040 inches, and a length in the range of 1.0 to 6.0 cm, and preferably in the range of 2.0 to 4.0 cm. The reinforcement bars 530 may be straight for linear insertion, or curved to gently wrap with the curvature of the annulus during insertion. In addition, the outer surface of the reinforcement bars 530 may have circular ridges or the like that the permit easy insertion into the annulus 52 but resist withdrawal and motion in the annulus following implantation. Other suitable materials for reinforcement bars 530 include titanium alloy 6-4, MP35N alloy, or super-elastic nickel-titanium alloy.

[0098] With general reference to FIGS. 12A-12J, the steps for implanting a self-expanding reinforcement member 510 are illustrated. It should be understood that the procedure for implanting a single member 510 in the anterior annulus 52 is shown for purposes of illustration, not limitation. All of the variables with regard to quantity, location, orientation, etc. discussed previously may be implemented by varying the generic procedure described hereinafter.

[0099] Initially, the sharpened stylet 430, semi-rigid needle 420 and rigid trocar 410 are assembled. As shown in FIG. 12A, the distal portion of the assembly 410/420/430 is inserted into the disc 50 as in a conventional discogram procedure. The assembly 410/420/430 is advanced until the distal tip 413 of the rigid needle is proximate the anterior curvature of the annulus 52, near the anterior side of the nucleus 54, as seen in FIG. 12B. The semi-rigid needle 420 (alone or with stylet 430) is advanced relative to the rigid trocar 410 until the curved portion 426 of the semi-rigid needle exits the distal tip 413 of the rigid trocar 410 and the desired amount of curvature is established, as seen in FIG. 12C. The curved portion 426 may be advanced until the tip 423 is substantially parallel to the tangent of the anterior annulus 52 curvature. The sharpened stylet 430 is advanced relative to the semi-rigid needle 420 to the desired position within the anterior annulus 52, as shown in FIG. 12D. The semi-rigid needle 420 and the rigid trocar 410 are completely withdrawn from the stylet 430, leaving the stylet in position as shown in FIG. 12E.

[0100] A flexible dilator 470 is advanced over the stylet 430 to dilate the annulus 52, as seen in FIG. 12F. The flexible dilator 470 is similar to semi-rigid needle 420 except that the dilator includes a blunt distal tip and is relatively more flexible, and has larger inner and outer diameters. Note that one or more dilators 470 may be advanced coaxially about the stylet 430 until the annulus is sufficiently dilated to accept the self-expandable member 510. The stylet 430 is then withdrawn from the flexible dilator 470 and the self-expandable member 510 is introduced into the lumen of the flexible dilator 470 using a push bar 480, as shown in FIG. 12G. Alternatively, the dilator 470 may be removed in favor of a flexible hollow catheter with a large inner diameter to facilitate delivery of member 510. The push bar 480 is similar to stylet 430 except that the distal tip of the push bar 480 is blunt. Alternatively, the push bar 480 may simply comprise the stylet 430 turned around, thus using the proximal blunt end of the stylet 430 as the push bar 480. The push bar 480 is advanced until the member 510 is in the desired position, as seen in FIG. 12H. To facilitate positioning the member 510, radiographic visualization may be used to visualize the distal end of the push bar 480, which is formed of radiopaque material and may include radiopaque markers. In addition, the member may be loaded with a radiopaque material to facilitate radiographic visualization thereof.

[0101] After the member 510 is in the desired position, the flexible dilator 470 is retracted from the push bar 480 while maintaining position of the member 510 with the push bar. The push bar 480 is then removed leaving the member 510 in place. If necessary, the procedure may be repeated for additional member implants 510. The member 510 is then allowed to expand over time, perhaps augmented by placing the spine 10 in traction. Alternatively, the spine 10 may be placed in traction prior to beginning the procedure.

[0102] With reference to FIGS. 12K-12L, the steps for implanting an inflatable reinforcement member 520 are illustrated. In this procedure, the steps outlined with reference to FIGS. 12A-12F are followed. Specifically, the same steps are followed up to and including the step of advancing the flexible dilator 470 over the stylet 430 to dilate the annulus 52, and thereafter removing the stylet 430 from the flexible dilator 470. Using a catheter 490, the inflatable member 520 is introduced into the dilator 470 and advanced until the member 520 is in the desired position, as shown in FIG. 12K. The inflatable member 520 is connected to the distal end of the catheter 490, which includes a flexible but pushable shaft 492 and an inflation port 494. The flexible dilator 470 is retracted from the catheter 490 while maintaining position of the member 520.

[0103] With the member 520 in the desired position, which may be confirmed using radiographic visualization as described above, the proximal inflation port 494 is connected to a syringe (not shown) or other suitable inflation apparatus for injection of the curable filler material. The filler material is then activated and the desired volume is injected into the catheter 490 via the inflation port 494, as seen if FIG. 12L. The filler material is allowed to cure and the catheter 490 is gently torqued to break the catheter 490 from the solid member 520. This break-away step may be facilitated by an area of weakness at the juncture between the distal end of the catheter 490 and the proximal end of the member 520. The catheter 490 is then removed leaving the member 520 in place. If necessary, the procedure may be repeated for additional member implants 520.

[0104] With reference to FIGS. 12M-12R, the steps for implanting a reinforcement bar 530 are illustrated. As seen in FIG. 12M, the disc 50 includes a protrusion or bulge 60, which is preferably, but not necessarily, reduced or eliminated before insertion of the reinforcement bar 530. This may be done by separating the adjacent vertebrae 20. In order to establish separation of the vertebrae 20, the spine 10 may be placed in traction or conventional intervertebral separation tools may be used. After the bulge 60 is reduced or eliminated, similar steps are followed as outlined with reference to FIGS. 12A-12C.

[0105] Delivery of a single reinforcement bar 530 into the posterior annulus 52 is illustrated. Specifically, the,distal portion of the assembly 410/420/480 is inserted into the disc 50 as in a conventional discogram procedure. The assembly 410/420/480 is advanced until the distal tip 413 of the rigid trocar 410 just penetrates the posterior side of the annulus 52, as seen in. FIG. 12N. The semi-rigid needle 420 (alone or with bar 530) is advanced relative to the rigid trocar 410 until the curved portion 426 of the semi-rigid needle 420 exits the distal tip 413 of the rigid trocar 410 and the desired amount of curvature is established, as shown in FIG. 12N. The curved portion 426 may be advanced until the tip 423 is substantially parallel to the posterior annulus 52.

[0106] Using the push bar 480, the reinforcement bar 530 with its sharpened tip is pushed into the annulus 52 as seen in FIG. 12O. The reinforcement bar 530 is advanced into the annulus 52 with the push bar 480 until the bar 530 is in the desired position, as seen in FIG. 12P, which may be confirmed using radiographic visualization as described above. The push bar 480 is then retracted, leaving the reinforcement bar 530 in place, as shown in FIG. 12P. The semi-rigid needle 420 and the rigid trocar 410 are then removed, as shown in FIG. 12Q, or, if necessary, the procedure may be repeated for additional reinforcement bar implants 530, as shown in FIG. 12R. Presence of the reinforcement bars 530 serves to keep the disc 50, and particularly the bulge 60, in a more normal condition, and to protect against continued bulging, thus easing nerve impingement.

[0107] From the foregoing, those skilled in the art will appreciate that the present invention provides reinforcement devices 100, 200, 300, 510, 520, and 530, which may be used to reinforce a damaged disc, while permitting relative movement of the adjacent vertebrae. The present invention also provides minimally invasive methods of implanting such devices as described above.

[0108] Those skilled in the art will recognize that the present invention may be manifested in a variety of forms other than the specific embodiments described and contemplated herein. Accordingly, departures in form and detail may be made without departing from the scope and spirit of the present invention as described in the appended claims.