Abstract:
A segmented intervertebral body fusion support includes a plurality of segments, the segments including an initial segment, a final segment and at least one intermediate segment. The intermediate segment has a generally trapezoidal configuration and the initial and final segments include tapered side walls providing triangular gaps between adjacent segments. A draw wire is fixed to the first segment and passes through the remaining segments. By pulling the draw wire relative to the segments, the segments are drawn together in a generally arcuate configuration. The draw wire includes an enlargement that passes through the final segment and engages a plurality of fingers on the final segment, which prevents the draw wire from retracting, maintaining the arcuate configuration. The segmented device can be inserted through a laparoscopic device into the intervertebral space and can be subsequently drawn into the arcuate configuration to establish the desired intervertebral spacing.

Description:
BACKGROUND OF THE INVENTION 
     Intervertebral discs serve several functions. A primary function of the intervertebral disc is to facilitate mobility of the spine. In addition, the disc provides load bearing, load transferring, and shock absorption between vertebral discs. The disc itself is formed of two major components, a gelatinous nucleus pulposus which is surrounded by an annulus fibrosis. 
     The intervertebral disc can be damaged in many ways. Mechanical damage can be caused by herniation in which a portion of the nucleus projects through an opening or tear in the annulus. Progressive degeneration can be caused by either genetic or biochemical problems. In such situations, there may be a decrease in the internal nucleus volume resulting in a decrease in disc height preventing the disc from performing its designed functions. 
     One way to relieve the symptoms of a ruptured or deteriorated disc is by surgical removal of a portion or all of the intervertebral disc. Removal of the disc decreases disc height, which can cause a number of severe problems. Therefore, subsequent to removal of the disc, steps must be taken to restore the disc height, or separation, between the adjacent vertebrae. Many attempts have been made to insert either mechanical devices or various polymeric materials that provide solid support between the vertebrae. These devices have had varying degrees of success. 
     One device that has been utilized to restore disc height is shown in U.S. Pat. No. 6,387,130. The implant includes a C-shaped curve and is placed anterior within the disc space. This implant has several limitations including the use of a plurality of implants to form the curved implant, lack of a mechanism to keep the plurality of implants in plane during placement in the disc space, and lack of an instrument to effectively deliver the implant. Additionally, a number of other implants are available that due to their predetermined C-shaped profile require a significant degree of manipulation during implantation into the disc space. This manipulation may require a larger surgical access opening in the patient as well as an increased opening in the annulus of the disc. 
     SUMMARY OF THE INVENTION 
     The present invention is premised on the realization that an insert formed from a plurality of generally trapezoidal segments can be inserted between adjacent vertebrae to maintain a desired disc space. More particularly, the present invention utilizes a plurality of interconnected trapezoidal segments, which, upon insertion into a disc space, can be drawn into a generally arcuate shape within the disc space to maintain disc height. The trapezoidal segments are preferably hinged to each other. In one embodiment, a continuous strip connects the segments and provides a plurality of interconnected hinges that organize the relationship between the trapezoidal segments allowing the segments to be drawn together and to not move out of plane when creating the finalized implant shape. 
     The segments have a flexible wire that runs from the first or leading segment to the final trailing segment, which can be pulled or moved relative to the trapezoidal segments to draw the segments together into a generally arcuate shape. A locking mechanism is provided to prevent the trapezoidal segments from separating from each other, maintaining the generally arcuate shape. 
     The flexible wire preferably includes a breakaway section. Force on the wire will first act to bend the insert into an arcuate shape and lock it into position. Additional force will cause the upstream portion of the wire to break away, allowing it to be removed. 
     The objects and advantages of the present invention will be further appreciated in light of the following detailed description and drawings in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a perspective view of the present invention; 
         FIG. 2  is a cross sectional depiction of the implant shown in  FIG. 1  prior to deployment; 
         FIG. 3  is a cross sectional view of the implant shown in  FIG. 1  in a deployed position; 
         FIG. 4  is a perspective view partially broken away of an apparatus used to apply the insert shown in  FIG. 1 ; 
         FIG. 5  is a cross sectional view taken at lines  5 - 5  of  FIG. 4 ; 
         FIG. 6  is a cross sectional diagrammatic view showing the implantation of the device shown in  FIG. 1 ; 
         FIG. 7  is a diagrammatic cross sectional view of the device shown in  FIG. 1  in an implanted state. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is an intervertebral support  10  that is designed to be implanted within the intervertebral space between adjacent vertebrae. The support  10  includes a leading segment  14 , a terminal segment  16  and a plurality of intermediate segments  18 . In one embodiment, four intermediate segments are included. In other embodiments, more or less intermediate segments can be utilized depending on factors such as patient anatomy or implant positioning. The segments  14 ,  16  and  18  are connected together by a continuous connective portion  20  along the base of the segments  14 ,  16  and  18  that following implantation forms an anterior wall  21  of the implant ( FIG. 7 ). 
     The leading segment  14  includes a rounded leading end  22 , radially inner side  24 , radially outer side  26 , and mirror image top  28  and bottom  30  sides. The leading segment  14  can optionally be configured to have a tapered or wedge shaped leading end  22  to facilitate implantation. The terms “radially inward”, “radially outward”, “top” and “bottom” reference the implanted support  10 . Segment  14  further includes an internal side  34 , which is tapered inwardly and includes a notch  32 . Segment  14  is connected at a hinge  35  to the next intermediate segment  18 . 
     Each of the intermediate segments  18  are identical. As shown, the intermediate segments  18  include a radially inner side  36 , a radially outer side  38 , a top surface  40  and a bottom surface  42 , and inner walls  44  and  46 . Wall  46  connects to the next adjacent intermediate segment by a hinge  48 . The inner walls  44  and  46  narrow as they extend from the outer side  38  towards the inner side  36  forming a generally trapezoidal cross section. The inner wall  44  further includes a key  50 , which is adapted to reside within the notch  32  of the leading segment  14 . Inner wall  46  includes a notch  52 , which is adapted to receive the key  50  of the next adjacent intermediate segment. 
     The trailing segment  16 , is connected to intermediate segment  18  by a hinge  53 , and includes a trailing end  54 , a radially inner side  56  and a radially outer side  58 , as well as a top surface  60  and a bottom surface  62 . The inner wall  64  of segment  16  is tapered inwardly from the outer side  58  towards the inner side  56 . This inner wall  64  further includes a key  66  adapted to fit within a notch  52  of intermediate segment  18 . 
     All of the segments include a central channel  70  that extends from leading end  22  to trailing end  54 . A plurality of inwardly biased fingers  72  surround the terminal end  73  of channel  70 . 
     Draw wire  74  extends through channel  70  and includes a distal knob  76 , having a lock ring  80  positioned within a channel in knob  76 . This prevents the knob  76  from moving through channel  70 . Draw wire  74  extends to a proximal bead  82  and is swedged into a narrow end  84 . Bead  82  further includes a larger end  86 . A tensioning line  88  is swedged to this larger end  86 . 
     Bead  82  includes a shoulder  89  between its narrow end  84  and larger diameter end  86 . This shoulder  89  is designed to engage the proximal ends of fingers  72  and prevent the draw wire  74  from retracting into channel  70 . 
     In order to enable the tensioning line to separate from bead  82 , the draw wire  74  is swedged more tightly to bead  82  than is tensioning line  88 . Preferably, the draw wire  74  will be swedged on bead  82  with 90 pounds of force, whereas the tensioning line  88  will be swedged onto end  84  with only about 20-30 pounds of force. Thus, increasing force applied to tensioning line  88  will eventually cause it to separate from bead  82 , leaving draw wire  74  in position within device  10 . 
     The support  10  is preferably made from any material that has been approved by the Food and Drug Administration for use in spinal applications. One preferred material is a polymeric material, such as polyether ether ketone (PEEK). Any material that has adequate strength and flexibility as well as compatibility for this intended application may be used. 
     As shown more particularly in  FIGS. 5 ,  6  and  7 , the support  10  is inserted into the intervertebral space through an opening created in the annulus of the intervertebral disk using an applicator  100 . Applicator  100  includes a rectangular barrel  102  fixed to a handle member  104 . Applicator  100  further includes a rod  106  having a plunger  108  at one end and a knob  110  at the opposite end. Rod  106  can be advanced down the barrel  102  by pressing trigger  111  of handle  112 . The tensioning line  88  extends through the barrel  102 , around a tensioning spool  114  to maintain the desired tension on draw wire  74 . A sufficient length of line  88  is on spool  114  to allow the support  10  to be inserted into the intervertebral space. The end of line  88  (not shown) is fixed to the spool  114 . Tensioning spool  114  either has a preset resistance to inhibit rotation, or a screw type mechanism  122  to tighten spool  114 . A tensioning spring can also be employed. 
     As shown in  FIG. 5 , the barrel  102  further includes inner ridges  116 . The upper and lower walls of the segments  14 ,  16  and  18  include channels  118  and  120 , which are adapted to ride on ridges  116  in barrel  102  maintaining the support in a linear position while in barrel  102 . 
     To insert the support  10  of the present invention, the intervertebral space in the cervical, thoracic, or lumbar region of the spine is accessed by way of an incision through the patient&#39;s tissue that leads to the vertebral column. Preferably, the vertebral column is accessed from a transforaminal approach. Alternatively, the vertebral column can be accessed through a lateral, anterior, anterior-lateral, posterior or posterior-lateral approach. The vertebral space is surgically prepared as desired, removing all or some of the nucleus or annulus fibrosis to provide any necessary spacing for the support  10 . Proper incisions are performed to allow the support to pass to and through the annulus fibrosis to the intervertebral space. 
     Support  10  is then placed into the disc space. It can be advanced using the handle  111  to move tab  128 , rod  106  and plunger  108  through barrel  104 . This moves support  10  out barrel  104  into the intervertebral space. Alternately, rear knob  110  can be struck with a hammer or similar instrument to provide the necessary force to move the support  10  into the disc space. Spring biased tab  124  prevents the rod  106  from moving in the opposite direction. 
     As the support  10  is inserted into the space, tension is applied in the direction of arrow  120 , which causes the support  10  to rotate into a generally arcuate or arched position. The radial continuity of the arch, as well as the degree of curvature can vary as desired. Generally, the support  10  will assume a general curved shape. The support  10  can be predisposed to have the general curved shape prior to loading into the applicator  100 . Alternatively, the support  10  can be linear prior to loading into the application  100  and the generally curved shape can be achieved through actuation of the applicator  100 . 
     Once the support  10  is properly inserted, tensioning line  88  is fixed and increased force is applied by plunger  108  against the rear surface  54  of the support  10 . The applied force will exceed the force holding the tensioning line  88  to the rear portion of bead  82 , separating the tensioning wire  88  from bead  82  and allowing the tensioning line  88  to be withdrawn. 
     More particularly, as the support  10  is inserted into the disc space, the tension on line  88  will cause the adjacent segments to rotate about the hinges and close the gap  113  between the adjacent segments. In one embodiment, the gap  113  has a generally triangular shape. Alternatively, the gap can be of any shape to accommodate movement of the segments in a manner that creates a desired implantation shape of the implantation shape of the implant, such as an arcuate shaped implant (C-shaped or V-shaped). This will continue until the support transforms from a linear shape and assumes the configuration shown in  FIG. 3 . As the support  10  changes to this final shape, the enlarged portion of bead  82  will pass through channel  70  and through the fingers  72 . The fingers  72  expand as the enlarged portion  86  of bead  82  passes through. The fingers  72  then retract, engaging the shoulder  89  between the narrow inner portion  84  of bead  82  and the larger end  86  (see  FIG. 3 ). This will prevent the wire  74  from moving in a direction opposite arrow  120  and permanently lock the support  10  in a generally arcuate position. 
     The implanted support  10  provides needed support between adjacent vertebrae. The interlocking notch and key configuration of the different segments prevents the adjacent segments from rotating relative to each other providing vertical stability. 
     The present invention can be modified in a number of ways, as desired. In particular, the connection portion  20  can be removed, and the individual segments connected by a hinge pin mechanism so that the individual segments are formed separately but attached together prior to implantation. Additionally, surfaces of the implant can be modified to have projections or teeth that provide friction between the implant and patient anatomy. Further, the support can be formed from any material that is suitable for implantation and possesses the required strength. 
     This support structure of the present invention provides many different advantages. It enables a support to be located into the intervertebral area utilizing a minimally invasive surgical procedure. This is particularly beneficial because of the limited space available in such a surgical procedure. Further, forcing the device into the intervertebral space as tension is applied causes the structure to bend as it passes into the intervertebral space, again allowing a longer support device to be inserted into the space. Further, the draw wire with the locking bead mechanism maintains this in a permanently arcuate condition. Finally, the interlocking notch and key structure of the adjacent segments prevent relative rotation of the segments about their central axis. 
     This has been a description of the present invention along with the preferred method of practicing the present invention. However, the invention itself should only be defined by the appended claims