Minimally invasive apparatus to manipulate and revitalize spinal column disc

[0001] This invention pertains to spinal column discs.

[0002] More particularly, this invention pertains to an apparatus and method for manipulating and revitalizing a disc in a spinal column.

[0003] In a further respect, the invention pertains to a method to surgically revitalize a damaged disc in a spinal column without requiring that the vertebrae bounding the disc be spread apart or resected.

[0004] In another respect, the invention pertains to a method for revitalizing a disc by retaining substantially all of the existing disc structure and by manipulating the shape and dimension of the disc.

[0005] Intervertebral discs connect the vertebra in a spinal column. Each healthy disc consists of two parts, an outer annulus fibrosis (hereinafter “the annulus”) and an inner nucleus pulposes (hereinafter “the nucleus”). The annulus completely circumscribes and encloses the nucleus. The annulus is connected to its adjacent associated pair of vertebrae by collagen fibers.

[0006] Typically, when a disc is damaged, the annulus ruptures and the nucleus herniates. Discetomy surgery removes the extruded nucleus, leaving behind the ruptured annulus. The ruptured annulus is, by itself, ineffective in controlling motion and supporting the loads applied by the adjacent pair of vertebrae. With time, the disc flattens and bulges, compressing nerves and producing pain. Uncontrolled loads are transmitted to each vertebra. Each vertebra tends to grow in an attempt to distribute and compensate for higher loads. When a vertebra grows, bone spurs form. The bone spurs further compress nerves, producing pain.

[0007] A variety of expandable intervertebral devices are disclosed in the art to control motion and support loads. Such devices are implanted intermediate an adjacent pair of vertebra, and function to assist the vertebra. These devices do not assist the intervertebral disc. In fact, in many cases the disc is removed.

[0008] Prior art intervertebral devices are either static or dynamic.

[0009] A static intervertebral device eliminates motion. Static devices are generally square, rectangular, trapezoidal, or box shapes that are immobile. Static devices replace the a disc to facilitate bone fusion. The insertion of a static device requires near total removal of the disc. An adjacent pair of vertebrae ordinarily are contoured to the static device and a bone graft. A static device temporarily maintains vertebrae immobilized until the bone graft heals. Static devices may, on insertion, initially expand, but their final state is immobile. Core elements with the threads on one portion reversed or oppositely wound from threads on another portion have been frequently utilized to expand immobilization (fusion) devices.

[0010] Following are examples of static immobilization devices.

[0011] European Patent Application 0260044 provides “A spinal implant comprising an elongate body divided longitudinally into two portions and being insertable in the joint space between two adjacent vertebra, engageable contact surfaces between the body portions, and expansion means movable between the contact surfaces of the body portions for spacing body portions apart and adjusting the joint spacing between adjacent vertebrae.” The purpose of the spinal implant is “to provide a permanent implant to substitute a full bone graft in establishing distraction inter body fusion.” The intervertebral disc is eliminated and replaced by the implant. Motion is limited to one axis. “Preferably the cam means comprises two sleeves each locatable within its own enlarged cavity within the body and being screw-threadedly mounted on the rod. Rotation of the rod in one direction moves the cam means outwardly towards the ends of the body, whilst rotation in the opposite direction moves the cam means towards each other until the cam means meet centrally of the body. In the latter case the body will rock at its extreme ends thus ensuring subtleness between injured or diseased vertebrae.” Included is a cylinder with at least one flat end limiting the insertion angle or direction. The device lacks an element or method to prevent disassembly upon traction or extension. “The exterior surface (of the implant) is of a porous material, smooth and coated with a bioactive material to chemically bond the bone and cartilage tissue of the vertebra to the implant.”

[0012] U.S. Pat. No. 5,658,335 to Allen provides “. . . a spinal fixator with a convex housing which fits within the contours of the concave vertebral bodies, and is cupped by the bony edges of the bodies, enabling secure placement without the necessity for additional screws or plates.” The intervertebral disc is removed to insert the spinal fixator. When the fixator is being inserted, “. . . teeth enter the vertebral body at an angle away from midline to prevent displacement of the fixator during spinal/flexure and/or extension.” In order to function properly, the fixator is highly dependent upon divergent teeth. One potential problem with the Allen fixator is that it can disengage from vertebrae when the spine is subjected to traction or tension. The Allen fixator can include external threads on the core member that are separated into two, oppositely wound portions, and can include a core member that defines an aperture for insertion of a tool to rotate the core member.

[0013] U.S. Patent Application 2004/017234A1 describes apparatus that engages apophyseal rings of an opposing pair of vertebrae when lateral members in the apparatus are in an extended configuration. The apparatus includes an expansion mechanism having a shaft. The shaft has threaded portions on opposite edges that threadly engage the lateral members. The threaded portions are oppositely threaded and have equal thread pitch.

[0014] U.S. Pat. No. 6,176,882 to Biederman et al. discloses a fusion device that is immobile after it is expanded. The shape of each of the side walls of the device is substantially trapezoidal to provide a truncated wedge-shaped body. The device includes a threaded spindle having two ends and two portions with opposite thread pitch. The adjusting element of the device comprises two wedge members. The teeth on the device are inwardly and outwardly adjustable so they can be individually adjusted to the prevailing anatomic shape of the end plates of each vertebra. Each portion of the spindle has a different thread pitch.

[0015] U.S. Pat. No. 5,514,180 to Heggeness, et al. discloses prosthetic devices that conform to the vertebral bone after removing the intervertebral disc or resecting the vertebra to conform to the device. The device is not expandable.

[0016] U.S. Patent Application No. 2005/0065610 discloses apparatus that engages and contacts each adjacent vertebra to stabilize the vertebra without the disc. The apparatus has sharp hard edges and is inserted into the disc space.

[0017] Dynamic devices move. Inserting a dynamic device like a total disc prosthesis requires a near total removal of disc tissue. A dynamic device ordinarily is inserted to contour to the vertebral bones without a bone graft. Sometimes the vertebral bones are contoured to the dynamic device. Round, curved, or circular shaped devices inserted after removing disc tissue or vertebral bone tend to migrate in the intervertebral disc space or subside within the vertebral bone. Dynamic devices are permanent devices that replace a disc, connect vertebral bones together, and control movement. Dynamic devices initially may expand. Their final state is mobile.

[0018] Other dynamic devices require a partial removal of disc tissue. The devices are inserted within the interior (nucleus) of an intervertebral disc and contour to the vertebral bones. Nucleus devices are generally smaller than devices used as a total disc prosthesis. Nucleus devices often are single parts lacking mechanisms. Fixation generally is not used and the device typically migrates within the disc space or subsides in vertebral bones. Other dynamic devices do not have solid bearing surface but comprise liquid or gas.

[0019] An example of a dynamic disc devices is described in U.S. Pat. No. 6,419,704 to Ferree. The Ferree patent discloses an expandable disc replacement composed of a fiber reinforced sealed body.

[0020] Other devices and methods function to patch or seal a disc without substantially supporting the vertebra. U.S. Pat. No. 6,805,695 to Keith et al, provides, “. . . positioning the implant around annular tissue.” The device must be directly attached to the annulus for it to function. The device is not expandable and requires the use of thermal energy to heat and denature the annulus changing the material properties of the disc.

[0021] The existing intervertebral support devices focus on substantially replacing a damaged intervertebral disc.

[0022] Inserting the existing intervertebral support devices require enlarging the pre-existing spaced apart configuration of the pair of vertebra.

[0023] None of the existing intervertebral support devices focus on manipulating to preserve a damaged intervertebral disc.

[0024] Accordingly, it would be highly desirable to provide an improved method and apparatus to revitalize a damaged intervertebral disc.

[0025] Therefore, it is a principal object of the invention to provide an improved method and apparatus to facilitate the recovery and proper functioning of a damaged intervertebral disc.

[0026] A further object of the invention is to provide an improved method for inserting an intervertebral device in a disc without requiring surgical separation of adjacent vertebra and with minimal damage to the disc and vertebra.

[0027] These and other, further and more specific objects and advantages of the invention will be apparent from the following detailed description of the invention, taken in conjunction with the drawings, in which:

[0028] FIG. 1 is a perspective view illustrating an intervertebral device constructed in accordance with the principles of the invention;

[0029] FIG. 1A is a perspective view of a tool that can be utilized in the practice of the invention;

[0030] FIG. 2 is a perspective-partial section view of the device of FIG. 1 illustrating additional construction details thereof;

[0031] FIG. 3 is an exploded view of certain components of the device of FIG. 1:

[0032] FIG. 4 is a perspective view further illustrating the device of FIG. 1;

[0033] FIG. 5 is a perspective view of the device of FIG. 1 illustrating certain components in ghost outline;

[0034] FIG. 6 is a top view illustrating the insertion of the device of FIG. 1 in an intervertebral disc adjacent the spinal column;

[0035] FIG. 7 is a side elevation view further illustrating the insertion of the device of FIG. 1 in the spinal column;

[0036] FIG. 8 is a top view illustrating a damaged intervertebral disc with a portion thereof bulging and pressing against the spinal column;

[0037] FIG. 9 is a top view illustrating the disc of FIG. 8 manipulated with a device constructed in accordance with the invention to alter the shape and dimension of the disc to revitalize the disc and take pressure off the spinal column;

[0038] FIG. 10 is a top view illustrating the disc of FIG. 8 manipulated with an alternate device constructed in accordance with the invention to alter the shape and dimension of the disc to revitalize the disc and take pressure off the spinal column;

[0039] FIG. 11 is a top view illustrating the disc of FIG. 8 manipulated in accordance with the invention to alter the shape of the disc from a normal “C-shape” to an oval shape;

[0040] FIG. 12 is a side elevation view illustrating a bulging disc intermediate a pair of vertebrae;

[0041] FIG. 13 is a side elevation view illustrating the disc and vertebrae of FIG. 12 after internal traction;

[0042] FIG. 14 is a side elevation view illustrating a rubber band or string that has a bulge similar to the bulge formed in a intervertebral disc; and,

[0043] FIG. 15 is a side elevation view illustrating the rubber band of FIG. 14 after it has been tensioned to remove the bulge.

[0044] Briefly, in accordance with our invention, we provide an improved method to manipulate a damaged intervertebral disc to improve the functioning of the disc. The disc includes an annulus. The method comprises the steps of providing a device to alter, when inserted in the disc, the shape and dimension of the disc; and, inserting the device in the disc to alter said shape and dimension of the disc. The disc is intermediate a first and a second vertebra. The first vertebra has a bottom adjacent the disc and the second vertebra has a top adjacent the disc. The device alters the shape and dimension of the disc by internal traction to increase the height (H) of the disc along an axis (G) generally normal to the bottom of the first vertebra and the top of the second vertebra. The device can also alter the shape and dimension of the disc by internal traction to decrease the width (W) of the disc. The device can further alter the shape and dimension of the disc by internal traction changing the pressure in the disc.

[0045] In another embodiment of our invention, we provide an improved method for inserting a device to improve in an individual's body the functioning of a damaged intervertebral disc, including an annulus, between a pair of vertebra, the body having a front, a first side, a second side, and a back. The disc includes a front portion facing the front of the body, side portions each facing a side of the body, and a back portion facing the back of the body. The vertebrae are in a pre-existing spaced apart configuration with respect to each other. The improved method comprises the steps of forming an opening in the disc between the pair of vertebrae, and in one of a group consisting of the side portions of the disc, the front portion of the disc, and the back portion of the disc; providing a support device shaped and dimensioned to fit through the opening in the disc; and, inserting the support device through the opening in the disc without enlarging the pre-existing spaced apart configuration of the pair of vertebrae.

[0046] In a further embodiment of the invention, we provide an improved method inserting a device to improve in an individual's body the functioning of a damaged intervertebral disc, including an annulus, between a pair of vertebrae. The individual's body has a front, a first side, a second side, and a back. The disc includes a front portion facing the front of the body, side portions each facing a side of the body, a back portion facing the back of the body, and a pre-existing rupture. The vertebrae are in a pre-existing spaced apart configuration with respect to each other. The method comprises the steps of providing a support device shaped and dimensioned to fit through the pre-existing rupture in the disc; and, inserting the support device through the pre-existing rupture in the disc without enlarging the pre-existing spaced apart configuration of the pair of vertebrae.

[0047] In a still further embodiment of our invention, we provide an improved method to manipulate a damaged intervertebral disc to improve the functioning of the disc. The disc includes an annulus. The improved method comprises the step of inserting a device in the disc, the device operable to apply a force to the disc. The method also comprises the step of operating the device to apply a force to the disc.

[0048] In still another embodiment of the invention, we provide an improved method to improve the functioning of a damaged intervertebral disc positioned between, contacting, and separating a pair of vertebrae. The disc includes an annulus. The method comprises the steps of providing a device shaped and dimensioned when inserted in the disc to contact each of the vertebrae, and operable in response to movement of the vertebrae to permit simultaneous polyaxial movement of the vertebrae and said device; and, inserting the device in the disc to contact each of the vertebrae.

[0049] Turning now to the drawings, which depict the presently preferred embodiments of the invention for the purpose of illustrating the practice thereof and not by way of limitation of the scope of the invention, and in which like reference characters refer to corresponding elements throughout the several views, FIGS. 1 to 5 illustrate a disc revitalization device constructed in accordance with the principles of the invention and generally indicated by reference character 100.

[0050] Disc revitalization device 100 includes a housing having an upper generally semi-oval member 42 and a lower generally semi-oval member 41. Shaft 59 is mounted on and inside the housing. The head 30 of shaft 59 includes an hex opening or indent 31A shaped to contour to and receive slidably the hexagonally shaped end of an elongate tool used to turn the head 30 of shaft 59. Unitary master cam 10 is fixedly secured to the center of shaft 59, along with externally threaded member 57 and externally threaded member 58. Member 57 is received by an internally threaded aperture in member 42A. Member 58 is received by an internally threaded aperture in member 43A. Conical members 42A and 43A each have a truncated conical exterior shape and have inner cylindrical openings that can slide along shaft 59 in the directions indicated by arrows B and C, respectively, when members 57, 58 rotate and displace members 42A, 43A along shaft 59. Members 57 and 58 are oppositely threaded such that when shaft 59 is turned in the direction of arrow A, member 57 turns inside conical member 42A and slidably displaces member 42A along shaft 59 in the direction of arrow B, and, member 58 turns inside conical member 43A and slidably displaces members 43A along shaft 59 in the direction of arrow C.

[0051] When members 42A and 43A are slidably displaced along shaft 59 in the direction of arrows B and C, respectively, the outer conical surfaces of members 42A and 43A slide over the arcuate inner surface 11B and 11C of arcuate shells 11 and 11A, respectively, and displace shell 11 upwardly away from shaft 59 in the direction of arrows D and E and shell 11A downwardly away from shaft 59 in directions X and Y opposite the directions indicated by arrows D and E.

[0052] Teeth or pins 12 depend outwardly from base 12A (FIG. 2) and are shown in the retracted position in FIGS. 2 and 4. Base 12A is mounted inside shell 11 beneath and within the head 56 of shell 11. Wave spring 13 contacts an undersurface of head 56 and downwardly displaces base 12A away from the head 56. Spring 13 therefore functions to maintain teeth 12 housed and retracted in openings 12B. Openings 12B extend through head 56. When teeth 12 are in the retracted position illustrated in FIG. 2, edge 88 of master cam 10 is in the position illustrated in FIG. 2 such that rib 53 engages slot 80 on the bottom of base 12A and prevents base 12A (and shell 11) from moving laterally in the directions indicated by arrows J and K in FIG. 2. When, however, a hex tool is used to rotate head 30 and shaft 59 in the direction of arrow A, master cam 10 rotates simultaneously with shaft 59 in the direction of arrow M (FIG. 1) until rib 53 turns completely out of slot 80 and smooth cam surface 54 engages and slidably contours to the arcuate bottom 12C of base 12A. When surface 54 engages bottom 12C, surface 54 is flush with adjacent portions of the conical outer surfaces of members 42A and 43A such that bottom 12C of base 12A and bottom 11B of shell 11 are free to slide laterally in the directions of arrows B and C over surface 54 and the outer conical surfaces of members 42A and 43A, and such that bottom 12C of base 12A and bottom 11 B of shell 11 are free to rotate or slide in the direction of arrow M (FIG. 1) and in a direction opposite that of arrow M over surface 54 and the outer conical surfaces of members 42A and 43A. This ability of shell 11 and base 12A to move bidirectionally or multidirectionally (i.e., to move polyaxially) by sliding laterally (in the direction of arrows J and K), by sliding forwardly or rotationally (in the direction of arrow M), and by sliding in direction intermediate said lateral and forward directions facilitates the ability of device 100 to adapt to movement of a vertebra. In addition, as rib 53 is turned out of and exits slot 80, cam surfaces 81 and 82 contact and slidably displace base 12A upwardly in the direction of arrow O (FIG. 2) to compress and flatten wave spring 13 and to displace teeth 12 outwardly through openings 12B such that teeth 12 are in the deployed position illustrated in FIG. 1.

[0053] As can be seen in FIG. 3, the construction of shell 11A and the base, head 56A, and teeth in shell 11A is equivalent to that of shell 11, base 12A, and teeth 12.

[0054] In FIG. 3, the end of shaft 59 is slidably received by aperture 52A formed in member 42A and interlocks with another portion of shaft 59 (not visible) inside member 42A. Members 57 and 58 are not, for sake of clarity, illustrated on shaft 59 in FIG. 3.

[0055] FIG. 6 illustrates the insertion of device 100 in a disc 50. An opening 51 is formed through the annulus 50A and device 100 is inserted inside the annulus. In FIG. 6, the size of the opening 51 is greater than normal and is exaggerated for purposes of illustration. When device 100 is inserted in disc 50, teeth 12 are retracted (FIG. 4). After device 100 is inserted, the hex end of a tool (FIG. 1A) is inserted in and engages opening or indent 31A and the tool is used to turn shaft in the direction of arrow A to outwardly displace shells 11 and 11A and to deploy teeth 12 (FIG. 1).

[0056] Another particular advantage of the invention is that in many cases it is not necessary to make an opening in disc 50 in order to insert device 100. Device 100 preferably has a shape and dimension that permit insertion through a pre-existing rupture in the annulus of a disc 50. The device can be inserted through the rupture “as is” (i.e., as the rupture exists), or the rupture can, if necessary, be widened sufficiently to permit insertion of device 100 through the rupture and annulus into the nucleus area circumscribed by the annulus. When a device 100 is inserted through a pre-existing rupture-either by inserting device 100 through the rupture as is or by widening and increasing the size of the rupture—it is not necessary to form another opening in the disc annulus.

[0057] FIG. 7 illustrates a surgical instrument 61 being utilized to insert disc revitalization device 100 in an intervertebral disc 50 that is adjacent and intermediate an upper vertebra 77B and a lower vertebra 78B in the spinal column of an individual 60. As would be appreciated by those of skill in the art, individual 60 is normally in a prone position when a device 100 is inserted in a disc 50.

[0058] One particular advantage of the invention is that in many cases it is not necessary to force apart the vertebra 77B and 78B bounding a disc 50 in order to insert device 100. Device 100 preferably has a shape and dimension that permits an incision to be made in disc 50 (preferably without cutting out a portion of disc 50) and the incision to be widened sufficiently to insert device 100 inside the disc 50. Any desired method can be utilized to insert device 100 in disc 50.

[0059] One method for inserting device 100 in the interior of disc 50 is utilized to insert device 100 in the front, back, or one of the side of a disc 50 without separating the pair of vertebra between which disc 50 is sandwiched. This method may include the step of using a needle to palpate and penetrate the annulus to the center of the disc. The stylette is removed from the needle and a guide wire is inserted until the tip of the wire is in the disc. The needle is removed from the guide wire. A dilator is placed on the guide wire and is used to enlarge the opening in the annulus. The wire is removed. A tube is inserted over the dilator. The dilator is removed. The device 100 is inserted through the tube into disc 50. The tube is removed. Before the tube is removed, an appropriately shaped and dimensioned tool 101 (FIG. 1A) can be inserted through the tube to engage and turn head 30 to outwardly displace shells 11 and 11A and deploy teeth 12.

[0060] FIG. 8 illustrates a damaged disk 70 that has developed a convex bulge in portion 74 of the annulus 72. The bulge generates pressure against the inner portion 75 of the spinal column 71. The pressure compresses nerves in the spinal column 71, causing pain. Similar pressure against nerve roots 77 and 78 can be generated when the annulus ruptures and material from the nucleus 73 herniates through the rupture and produces pressure against spinal column 71 or nerve roots 77 and 78.

[0061] FIG. 9 illustrates one procedure to relieve the pressure caused by bulge 74. A disc revitalization device 76 is inserted inside the annulus 72 and generates pressure against the annulus 72 in the direction of arrows S and T that causes the annulus to lengthen in those directions. When the annulus lengthens, the middle portions of the annulus tend to be drawn in the direction of arrows R and Z, narrowing the annulus and displacing the convex bulge away from the portion 75 of the spinal column 71. The shape and dimension of device 76 can be varied as desired to alter the shape of annulus 72, nucleus 73, and disc 70 in any desired manner when device 76 is inserted in disc 70. While portions of the nucleus 73 and annulus 72 can be removed to insert device 76, it is preferred that little, if any, of the nucleus 73 and annulus 72 be removed during installation of device 76. The principal object of the invention is, as much as possible, to revitalize a disc 70 so that the functioning of disc 70 resembles as closely as possible the functioning of a normal healthy disc, or resembles as closely as possible the functioning of disc 70 before it was compressed, herniated, ruptured, or otherwise damaged. To achieve this object, it normally is desirable to leave in place as much as possible of the original disc material.

[0062] In FIG. 9, portion 74 has taken on a concave orientation. The disc 70 in FIG. 9 has a so-called “C-shape” generally associated with a normal healthy disc. The C-shape of disc 70 is produced in part because of the concave orientation of portion 74, which represents the center portion of the C-shape. One drawback of the C-shape of disc 70 is that portions 72A and 72B of disc 70 are, as can be seen in FIG. 9, adjacent nerve roots 78 and 77, respectively, which makes it more likely that portions 72A and 72B can, by bulging, by herniation of the nucleus through a rupture, or otherwise, exert undesirable pressure on nerve roots 78 and 77. The embodiment of the invention illustrated in FIG. 11 minimizes the likelihood of such an occurrence.

[0063] In FIG. 11, the disk revitalization device 76 is shaped and dimensioned such that when device 76 is inserted in disc 70, the inner wall 73A of annulus 72 contacts and conforms to device 76 such that disc 70 no longer has a C-shape, but has an oval shape. The outer arcuate wall 73D of disc 70 becomes convex along its entire length. The oval shape of disc 70 spaces portions 72A and 72B further away from nerve roots 78 and 77 and reduces the likelihood that a bulge or hernia will contact and produce undue pressure on roots 78 and 77. In the practice of the various embodiments of the invention described herein, it is not required that disc 70 be manipulated by a device 76 or other means to take on an oval shape, and it is not required that the normal C-shape of a disc 70 be dispensed with. It is, however, preferred that disc revitalization device 76 manipulate a disc 70 such that the shape of disc 70 tends to change from the normal C-shape and become more oval, or that at least the section of disc 70 that is adjacent spinal column 71 and nerve roots 78 and 77 and that is comprised of portions 72A, 74, and 72B tend to become more convex and adopt a curvature more comparable to a portion of an oval.

[0064] It is not believed necessary for a disc revitalization device to contact the inner wall 73A of the annulus 72 of a disc 70 in order for the device to cause the shape of a disc to change. For example, FIG. 10 illustrates a disc revitalization device 77A that is inserted in the nucleus 73 of a disc 70 and that does not contact the inner wall 73A of the annulus 72. Device 77A is shaped such that it tends to force material comprising the nucleus 73 to gather and be compressed in areas 73F and 73G. Such a compression of nuclear material can generate forces that act in the direction of arrows U and V and that tend to cause disc 70 to elongate in the directions of arrows U and V. Regardless of whether a device 76, 77A, 100 contacts the inner wall 73A of the annulus 72 of a disc 70, it is preferred that all, or substantially all, of the outer surface of the portion of the housing 41, 42 that will contact the nucleus 73 or the annulus 72 have a smooth, preferably arcuate, shape about at least one axis. By way of example, and not limitation, the surface of a cylindrical is arcuate about one axis. The surfaces of a sphere or egg are each arcuate about more than one axis.

[0065] Use of a disc revitalization device 100 is further described with reference to FIGS. 12 and 13. In FIG. 12, damaged disc 95 has been compressed between vertebra 90 and 91 and is bulging outwardly through and from the bottom 92 of disc 90 and the top 93 of disc 91. The disc 95 has ruptured at two locations and herniated material 96, 97 from the nucleus extends outwardly through the ruptures. In FIG. 12, the bulging of disc 95 outside of vertebra 90 and 91 is, for sake of simplicity, pictured as being uniform around the perimeter of the vertebrae. This is not normally the case. The amount that the disc 95 bulges typically varies with the location on the periphery of the bottom 92 of vertebra 90 and top 93 of vertebra 91. Similarly, the herniation of nucleus material 96, 97 is, for sake of simplicity, pictured in a generally uniform spherical shape. This is not normally the case. The shape of a herniation of nucleus material need not be uniform or have the shape and dimension of any recognizable symmetric geometric figure.

[0066] After device 100 is inserted internally into the nucleus of disc 95, a tool with a hex end is inserted in opening 31A and the tool is utilized to turn head 30 in the direction of arrow A (FIG. 1) to displace and expand shell 11 outwardly in the direction of arrows D and E, to displace and expand shell 11A outwardly in the direction of arrows X and Y and away from shell 11, to deploy teeth 12 to engage a portion of the bottom 92 of vertebra 90, to deploy teeth associated with shell 11A to engage a portion of the top 93 of vertebra 91, and to subject disc 95 to internal traction by displacing vertebra 90 and/or 91 vertically along axis G in a direction generally normal to the bottom 92 of vertebra 90 and to the top 93 of vertebra 91 to increase the separation distance between vertebra 90 and 91, to increase the height H of disc 95, and to decrease the width W of disc 95. Since a spine is generally curved along its length, vertebra in the spine are not stacked one directly on top of the other along a straight vertical axis. One vertebra usually is slightly canted with respect to its adjacent vertebra. Nonetheless, the axis G can be said to be generally normal (with plus or minus 45 degrees) to the bottom 92 of one vertebra and to the top 93 of an adjacent vertebra.

[0067] When disc 95 is subjected to internal traction, the disc 95 often tends to undergo a transformation from the short, squat, bulged configuration of FIG. 12 to the tall, retracted configuration illustrated in FIG. 13. The bulged part of the disc 95 retracts inwardly to a position between vertebrae 90 and 91 in the same general manner that the bulge 105 in rubber band or string 102 (FIG. 14) retracts inwardly when the ends of the string 102 are pulled in the directions indicated by arrows 103, 104 to produce the “taller” (i.e., longer) string 102 illustrated in FIG. 15. When bulge 105 retracts inwardly, the width W of the disc 95 is reduced.

[0068] Further, when disc 95 takes on the tall retracted configuration of FIG. 13, the volume of the space inside and circumscribed by the inner edge 73A (FIG. 10) of the annulus (i.e., the space in which material comprising the nucleus 73 is found) increases because the increase in the height of the space concomitant with the increase in the height of disk 95 usually offsets and is greater than the decrease in the diameter or width of the space concomitant with the retraction of the disk 95. The increase in the volume of the space in which the nucleus is found generates negative pressure or generates forces that tend to pull or permit the herniated nucleus material 96, 97—that prior to internal traction extended outwardly through ruptures in the annulus 94 in the manner illustrated in FIG. 12—to move through the associated disc ruptures and back into the inner annular space in which nucleus material is ordinarily found. Increasing the height of and retracting disc 95 also tends to close or partially close ruptures 98 formed in the annulus 94 so that the ruptures often will heal completely closed of their own accord. Similarly, if an opening has been made through the annulus 94 to facilitate insertion of a disc revitalization device 100, the internal traction of disc 95 tends to close the opening to facilitate healing of the opening. Such an incision normally, but not necessarily, would be vertically oriented in the same manner that annulus rupture 98 is vertically oriented in FIG. 13.

[0069] The device 100 can be oversized and shaped such that during internal traction the device 100 prevents the internal opening (which opening would be bounded by the internal wall 73A of the annulus) in the annulus of disc 95 from completely retracting or reducing in size to a particular width when a disc moves from the bulging configuration of FIG. 12 to the retracted, taller configuration of FIG. 13. When device 100 prevents the internal opening in the annulus from fully inwardly retracting or constricting along axes that lie in a horizontally oriented plane that is generally normal to axis G in FIG. 13, the annulus and/or nucleus generate and maintain for at least a while compressive forces against the device 100. This “tensioning” of the annulus and/or nucleus tends to anchor the device 100 in position in disc 95, to prevent migration of device 100, and therefore to produce a unitary, stronger structure comprised of the disc 95 and the “captured” or a “squeezed” device 100.

[0070] The shape and dimension and constructions of the disc revitalization device 100 can vary as desired provided that device 100, when inserted in a disc 95, can be utilized to separate a pair of adjacent vertebrae 90, 91 the distance necessary during internal traction to obtain the desired retraction and height increase of a disc 95 intermediate the pair of vertebrae, provided that the device 100 functions to contact the nucleus and/or annulus of the disc 95 to produce the desired shape of disc 95, and/or provided that the device 100 functions to contact the nucleus and/or annulus of the disc 95 to produce tension in the annulus and/or nucleus because the device 100 prevents disc 95 from fully retracting and causes the nucleus and/or annulus to squeeze or compress device 100.

[0071] In FIG. 11, one acceptable contour of the portion of a disc 70 that is closest to nerves 77, 78 and spinal column 71 is the oval convex shape indicated by dashed line 200. A more preferred contour (than the contour indicated by dashed line 200) is the relatively flat contour depicted by the flat line representing portion 74 of disc 70. The most preferred contour is the concave contour represented by dashed line 201. The contour represented by dashed line 201 is most preferred because it is less likely that any bulge or herniation of disc 70 will press against nerves 77, 78 or against spinal column 71. It is, of course, preferred that each of the contours 200, 74, 201 of disc 70 be spaced apart from nerves 77, 78 and spinal column 71 to minimize the likelihood that a portion of disc 70 will contact nerves 77, 78 and spinal column 71. As used herein in connection with the invention and the claims, a disc includes at least fifty percent (50%) of its original annulus and may or may not include all or a portion of its original nucleus.

[0072] Having described our invention in such terms as to enable those of skill in the art to make and practice it, and having described the presently preferred embodiments thereof,