Patent Publication Number: US-2012029644-A1

Title: Compliant Interbody Fusion Device with Deployable Bone Anchors

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. patent application Ser. No. 12/326,079 filed on Dec. 1, 2008, the contents of which, in its entirety, is herein incorporated by reference. 
    
    
     BACKGROUND  
     1. Technical Field 
     The embodiments herein generally relate to spinal stabilization devices, and more particularly to a compliant interbody fusion device with deployable bone anchors. 
     2. Description of the Related Art 
     Conventional spinal fusion implants typically having projections that can be deployed after the implant has been inserted into the disc space and are used to stabilize the human spine. A problem with the conventional spinal fusion implants is that they are static in size. This poses various problems with their use and/or implantation. As a result, nerves may become pinched, causing pain that radiates into other parts of the body and instability in the vertebrae. 
     To overcome this, spinal decompression and fusion procedures can be augmented with bone or implants being inserted between the vertebral bodies and held in place with pedicle screws. This disrupts the normal biomechanics of the spine while correcting the instability. Fusion, while correcting the instability, can also cause adjacent disc disease. Also, generally the conventional interbody designs are non-complaint or do not have deployable bone anchors that can be opened after insertion to aid ease of implantation. 
     These standard devices are also more prone to subsidence and may contribute to adjacent disc disease. Moreover, these devices generally do not help in restoring the normal biomechanics of the thoraco-lumbar spine. In conjunction with a dynamic rod/screw system or stand-alone, the device may not reduce the chances of adjacent disk disease. 
     SUMMARY 
     In view of the foregoing, an embodiment herein provides an interbody fusion implant with deployable bone anchors including a support member having a first end and a second end, the second end including two flanges, the flanges are configured to dig into an endplate of a vertebral body. The interbody fusion implant further includes a monolithic body that accommodates the support member, and a longitudinal hole along a vertical length of the support member. The longitudinal hole sustains loads imported on the interbody fusion implant and allows the interbody fusion implant to flex freely. 
     The support member includes at least one of a clip shaped support member and an I-shaped support member. The flanges of the support member may provide a location fixation on an implantation of the interbody fusion implant into the vertebral body. The I-shaped support member allows rigidity and a support in flexion-extension through a living-hinge positioned in a middle of the I-shaped support member. The I-shaped support member is cut in a front and a side plane to enable two degrees of freedom and to bend in at least one of a sagital and a transverse plane. 
     The interbody fusion implant may be inserted in at least one of anteriorly, posteriorly, or transforaminal in the vertebral body. A cephalad and a caudal surface of the interbody fusion implant is molded with surface finishes to provide an additional fixation with the endplate of the vertebral body and the surface finishes includes at least one of teeth, geometry, and serrations. The geometry may provide an ease of attachment and flexibility in the vertebral body. 
     Another embodiment provides an apparatus to stabilize a human spine. The apparatus includes a compliant monolithic interbody fusion implant including at least one support member having at least one rod that is rotated with a driving instrument, a plurality of spikes attached to the rod, a monolithic complaint body that accommodates the rod and the spikes, at least one window molded in the monolithic complaint body, and an inserter tool that inserts the compliant monolithic interbody fusion implant into the human spine. 
     The window rotates the rod from a horizontal to a vertical configuration. The plurality of spikes penetrate endplates of vertebral bodies in the human spine to fix the monolithic compliant body in place in a vertical configuration. The plurality of spikes are preferably symmetric and perpendicular to a main axis of the rod. The apparatus may further include a plurality of rods. Each rod including at least two spikes. The spikes are positioned perpendicular to the main axis of the rod and the rod rotates from a vertical to a horizontal configuration. 
     The plurality of rods are positioned within the monolithic compliant body to form a cephalad and caudal set. The plurality of rods may include at least one gear at a proximal end of each rod to drive and rotate the rod from a horizontal to vertical position. 
     The plurality of rods and the gear are positioned and timed to each other with a corresponding female beveled gear to deploy the plurality of rods and the gear with a one turn motion. The inserter tool includes a protrusion that accommodates the gear. 
     Yet another embodiment provides an interbody fusion assembly for attachment to endplates of vertebral bodies. The interbody fusion assembly includes a tube including at least one hole, the tube including a camshaft, a plurality of cams coupled to the camshaft, and a plurality of free moving spikes coupled to the cams along a perpendicular axis to the camshaft, and a complaint monolithic body that accommodates the tube. The free moving spikes are positioned in a vertical orientation and set within the tube. The plurality of cams force the free moving spikes upward into the endplates of the vertebral bodies upon rotation of the camshaft. The free moving spikes may cut at least partially through the complaint monolithic body. 
     The free moving spikes penetrate the endplates to fix the complaint monolithic interbody fusion assembly in place upon rotation of the camshaft. A plurality of holes may be molded into the complaint monolithic body to allow passage of the free moving spikes. A cephalad and a caudal surface of the complaint monolithic body is molded with surface finishes to provide fixation with the endplates. The surface finishes include at least one of teeth, geometry, and serrations. 
     These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which: 
         FIGS. 1A and 1B  illustrate perspective views of a compliant monolithic spinal fusion implant according to a first embodiment herein; 
         FIGS. 2A and 2B  illustrate perspective views of a compliant monolithic spinal fusion implant according to a second embodiment herein; 
         FIGS. 3A and 3B  illustrate perspective views of a compliant monolithic spinal fusion implant according to a third embodiment herein; 
         FIGS. 4A and 4B  illustrate perspective views of a compliant monolithic spinal fusion implant and an inserter tool according to a fourth embodiment herein; 
         FIGS. 5A and 5B  illustrate perspective views of a compliant monolithic spinal fusion implant according to a fifth embodiment herein; and 
         FIG. 5C  illustrates a sectional view of a compliant monolithic spinal fusion implant according to a fifth embodiment herein. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein. 
     The embodiments herein provide a compliant material monolithic spinal fusion device for spinal stabilization. The embodiments herein provide an I-shaped support member of a spinal fusion implant that allows more rigidity and support through the middle of the device and act as a living-hinge in flexion-extension, enables two degrees of freedom, acting as a joint that can bend in both the sagital and transverse planes. 
     The compliant material monolithic spinal fusion device aids in restoring the normal biomechanics of the thoraco-lumbar spine. In conjunction with a dynamic rod/screw system or stand-alone, the device reduces the chances of adjacent disk disease. Referring now to the drawings and more particularly to  FIGS. 1A through 5C  where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments. 
       FIGS. 1A and 1B  illustrate a perspective view of a compliant monolithic spinal fusion implant  100  according to a first embodiment herein. With reference to  FIGS. 1A and 1B , the compliant monolithic spinal fusion implant  100  includes a compliant monolithic body  102 , a support member  104 , a longitudinal hole  106  along the vertical length of the support member  104 , and flanges  108  located near the opening of the hole  106 . The compliant monolithic spinal fusion implant  100  may be inserted anteriorly, posteriorly, or transforaminal in between vertebral bodies of the spine. 
     The longitudinal hole  106  along the vertical length of the clip shaped support member  104  enables the support member  104  to sustain a heavy load and flex freely. A cephalad and a caudal surface of the compliant monolithic spinal fusion implant  100  may be molded with a surface finish (e.g., teeth, geometry, or serrations) to provide an additional fixation with endplates (not shown). In one embodiment, the support member  104  is embodied as a clip shaped support member. In another embodiment, the geometry of the support member  104  provides flexibility and can be squeezed shut for a minimal profile during an insertion and ease of attachment to an insertion tool (not shown). 
     When the insertion tool (not shown) is removed, the support member  104  may spring open to support the vertebral bodies. The flanges  108  on the end of the support member  104  may dig into the endplates to provide a location fixation. The compliant monolithic spinal fusion implant  100  may be inserted or impacted by means of the inserter tool (not shown). 
     In a preferred mode, the inserter tool (not shown) includes a shaft of an adequate length. One end of the inserter tool (not shown) may include a protrusion attached to the compliant monolithic spinal fusion implant  100  via a snap fitting around the flanges  108  of the support member  104 . The opposite end of the inserter tool (not shown) may include a handle with an impact surface. When the compliant monolithic spinal fusion implant  100  is loaded, the inserter tool (not shown) is lightly impacted, the compliant monolithic spinal fusion implant  100  may get wedged between the vertebral bodies, slightly decompress them and provide support surfaces for proper biomechanical movement of the spine. 
       FIGS. 2A and 2B  illustrate a perspective view of a compliant monolithic spinal fusion implant  200  according to a second embodiment herein. The compliant monolithic spinal fusion implant  200  includes a compliant monolithic body  202 , a support member  204 , a longitudinal hole  206  along the vertical length of the I-shaped support member  204 , and flanges  208 . The support member  204  may allow more rigidity and support through the middle of the support member  204  which acts as a living-hinge in flexion-extension. 
     In one embodiment, the support member  204  is an I-shaped support member. The support member  204  may also be cut in both the front and side planes to allow two degrees of freedom, acting as a joint that can bend in both the sagital and transverse planes. The longitudinal hole  206  along the vertical length of the support member  204  may enable the support member  204  to sustain a heavy load and flex freely. The flanges  208  on the end of the support member  204  may dig into endplates (not shown) to provide a location fixation. 
       FIGS. 3A and 3B  illustrate a perspective view of a compliant monolithic spinal fusion implant  300  according to a third embodiment herein. The compliant monolithic spinal fusion implant  300  includes a compliant monolithic body  302 , a rod  304  longitude to the compliant monolithic body  302  with a plurality of symmetric spikes  306 , and windows  308 . The rod  304  is insert-molded in the compliant monolithic body  302 . The spikes  306  are attached to the rod  304  perpendicular to the main axis of the rod  304 . 
     The windows  308  are molded in the compliant monolithic body  302  to enable the rod  304  to rotate from a horizontal to a vertical configuration. In the vertical configuration, the spikes  306  penetrate the end plates (not shown) to fix the compliant monolithic body  302  in place. The rod  304  may be rotated with an appropriate driving instrument (not shown). 
       FIGS. 4A and 4B  illustrate a perspective view of a compliant monolithic spinal fusion implant  400  and an inserter tool  412  according to a fourth embodiment herein. The compliant monolithic spinal fusion implant  400  includes a compliant monolithic body  402  and a plurality (e.g., four) separate rods  404 . Each of the rods  404  includes one set of spikes  406  and gears  408 . The rods  404  are insert-molded into the compliant monolithic body  402  and have the ability to rotate from a horizontal to a vertical configuration. 
     The rods  404  are positioned within the compliant monolithic body  402  so as to have a cephalad and a caudal set. The spikes  406  are attached to the rod  404  perpendicular to the main axis of the rods  404 . The gears  408  are positioned along the main, longitudinal axis of the rods  404 . The gears  408  at the proximal end of the rods  404  enables the ability to drive and rotate the rods  404  from a horizontal to a vertical position. In one embodiment, the rods  404  are positioned and the gears  408  timed to each other so that a single driving instrument  412  with female beveled gears  410  may deploy them simultaneously with one turn motion. The inserter tool  412  is used to insert the compliant monolithic spinal fusion implant  400  into the vertebral bodies of the spine. 
     One end of the inserter tool  412  has a protrusion  410  to receive the gears  408  of the rods  404  attached to the compliant monolithic body  402 . The opposite end of the inserter tool  412  has a handle with an impact surface. When the compliant monolithic spinal fusion implant  400  is loaded in the inserter tool  412  and inserted, the compliant monolithic spinal fusion implant  400  gets wedged between the vertebral bodies, slightly decompress them and provide support surfaces for proper biomechanical movement of the spine. 
       FIGS. 5A and 5B  illustrate a perspective view of a compliant monolithic spinal fusion implant  500  according to a fifth embodiment herein.  FIG. 5C  illustrates a sectional view of a compliant monolithic spinal fusion implant  500  according to a fifth embodiment herein. The compliant monolithic spinal fusion implant  500  includes a compliant monolithic body  502 , a tube  504 , a camshaft  506 , cams  508 , and a plurality of free moving spikes  510 . The cams  508  are attached to the camshaft  506 . 
     The camshaft  506  and the spikes  510  are insert molded into the compliant monolithic body  502  and positioned in a vertical orientation and set within the tube  504  with holes. The tube  504  acts as housing for the camshaft  506 . In one embodiment, when the camshaft  506  is rotated, the cams  508  force the spikes  510  upward into the endplates (not shown) of the vertebral bodies, fixing the compliant monolithic spinal fusion implant  500  in place. In another embodiment, the spikes  510  may have to cut their way through the compliant monolithic body  502  or there may be holes molded into the compliant monolithic body  502  to allow easier passage. 
     The embodiments herein provide a compliant material monolithic spinal fusion implant that may be inserted anteriorly, posteriorly, or transforaminal in between vertebral bodies of the spine. The design provides an optimal surface coverage while acting as a compliant interbody or disc. It is held in place by various embodiments of deployable bone anchors. The I-shaped support member  204  of  FIG. 2  allows additional rigidity and support through the middle of the device and acts as a living-hinge in flexion-extension. The I-shaped support member  204  may also be cut in both the front and side planes to allow two degrees of freedom, acting as a joint that can bend in both the sagital and transverse planes. 
     The compliant material monolithic spinal fusion devices  100 ,  200 ,  300 ,  400 ,  500  are used in surgery to stabilize the human spine. They aid in restoring the normal biomechanics of the thoraco-lumbar spine. In conjunction with a dynamic rod/screw system or stand-alone, the devices  100 ,  200 ,  300 ,  400 ,  500  reduce the chances of adjacent disk disease. These devices  100 ,  200 ,  300 ,  400 ,  500  are an improvement over existing devices in terms of fixation to the endplates. The devices  100 ,  200 ,  300 ,  400 ,  500  are designed to work with any appropriate compliant implantable material and may utilize all the standard surgical tools that accompany such devices  100 ,  200 ,  300 ,  400 ,  500 . 
     The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.