Patent Publication Number: US-2018036136-A1

Title: Intervertebral fusion implant

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of U.S. patent application Ser. No. 14/526,936, filed Oct. 29, 2014, which is a continuation application of U.S. patent application Ser. No. 13/363,539, filed on Feb. 1, 2012, now issued as U.S. Pat. No. 9,358,127, which is a continuation of U.S. patent application Ser. No. 12/202,690 filed on Sep. 2, 2008, now issued as U.S. Pat. No. 8,328,872, which are each incorporated by reference in their entirety herein. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure generally relates to a fixation device for positioning and immobilizing at least two adjacent vertebra. In particular, the present invention relates to a stand alone interbody fusion device for implementation in the spine. 
     BACKGROUND OF THE INVENTION 
     The vertebral spine is the axis of the skeleton on which all of the body parts “hang”. In humans, the normal spine has seven cervical, twelve thoracic and five lumbar segments. The lumbar spine sits upon the sacrum, which then attaches to the pelvis, and in turn is supported by the hip and leg bones. The bony vertebral bodies of the spine are separated by intervertebral discs, which act as joints but allow known degrees of flexion, extension, lateral bending, and axial rotation and translation. 
     The typical vertebra has a thick anterior bone mass called the vertebral body, with a neural (vertebral) arch that arises from the posterior surface of the vertebral body. The central of adjacent vertebrae are supported by intervertebral discs. The spinal disc and/or vertebral bodies may be displaced or damaged due to trauma, disease, degenerative defects, or wear over an extended period of time. One result of this displacement or damage to a spinal disc or vertebral body may be chronic back pain. In many cases, to alleviate back pain from degenerated of herniated discs, the disc is removed along with all or part of at least one neighboring vertebrae and is replaced by an implant that promotes fusion of the remaining bony anatomy. 
     However, the success or failure of spinal fusion may depend upon several factors. For instance the spacer or implant or cage used to fill the space left by the removed disc and bony anatomy must be sufficiently strong to support the spine under a wide range of loading conditions. The spacer should also be configured so that it likely to remain in place once it has been positioned in the spine by the surgeon. Additionally the material used for the spacer should be biocompatible material and should have a configured that promotes bony ingrowth. 
     In combination with spacers or cages, a plating system is used to further stabilize the spine during the fusion process. These devices, commonly referred to as bone fixation plating systems, typically include one or more plates and screws for aligning and holding vertebrae in a fixed position with respect to one another. Plating systems independent of the spacers provide additional complications such as loosening and failure of the hardware. Two common failures are the breakage of the plates, and the backing out of screws into soft tissues of the patient&#39;s body. The backing out of the screws is typically a result of the screws failure to achieve a sufficient purchase in the bone, although the stripping of the screws has also been known to cause this problem. Another common problems is that plating systems require “carpentry” work to match fit aspects of the vertebral bodies. 
     There is a need for a spine stabilization system that in promotes fusion of adjacent vertebrae while at the same time provides stabilization of the spinal area where fusion occurs. There is a need for a system that incorporates both the fusion element and the plating element in one system to reduce the possible complications that may occur. There is also a need to provide a system that reduces the complications that may occur in the fusion element and the plating element and a need for this system to be configured so that positioning this system is efficient and easy. 
     SUMMARY OF THE INVENTION 
     The present invention provides an intervertebral implant for implantation in a treated area of an intervertebral space between vertebral bodies of a spine. The implant includes a spacer portion having an inferior and superior surface, wherein the inferior and superior surfaces each have a contact area capable of engaging with anatomy in the treated area, and the inferior and superior surfaces define a through-hole extending through the spacer body. The present invention further provides screw holes extending from a side portion to the inferior and superior surfaces of the spacer portion and a plate portion rigidly coupled to the spacer portion through a coupling means, wherein the plate portion contains screws holes for receiving screws. A screw back out prevention mechanism is adapted on the plate portion and prevents the back out of screws from the screw holes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of an intervertebral implant according to the present invention; 
         FIG. 2  is another perspective view of the embodiment of the implant shown in  FIG. 1 ; 
         FIG. 3  is a side view of the intervertebral implant of  FIG. 1 ; 
         FIG. 4  is a top view of the intervertebral implant of  FIG. 1 ; 
         FIG. 5  is an exploded view of the intervertebral implant of  FIG. 1 ; 
         FIGS. 6 and 7  is a perspective view of the intervertebral implant of  FIG. 1  which include illustrations of bone fasteners; 
         FIG. 8  is another side view of the intervertebral implant of  FIG. 1  incorporating bone fasteners; 
         FIG. 9  is a perspective view of another embodiment of the intervertebral implant; 
         FIG. 10  is a front view of the intervertebral implant with bone screws locked of  FIG. 9 ; 
         FIG. 11  is a front view of the intervertebral implant illustrated in  FIG. 9 ; 
         FIG. 12  is an exploded view of the intervertebral implant with bone fasteners unlocked of  FIG. 9 ; 
         FIG. 13  is yet another embodiment of the intervertebral implant; 
         FIG. 14-16  are different views of the intervertebral implant of  FIG. 13 ; and 
         FIG. 17  is an exploded view of the intervertebral implant of  FIG. 14  according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     Embodiments of the disclosure are generally directed to flexible stabilization systems for use with the anterior, antero-lateral, lateral, and/or posterior portions of at least one motion segment unit of the spine. The systems of the invention are designed to be conformable to the spinal anatomy, so as to be generally less intrusive to surrounding tissue and vasculature than existing rigid stabilization systems. 
     Certain embodiments may be used on the cervical, thoracic, lumbar, and/or sacral segments of the spine. For example, the size and mass increase of the vertebrae in the spine from the cervical to the lumbar portions is directly related to an increased capacity for supporting larger loads. This increase in load bearing capacity, however, is paralleled by a decrease in flexibility and an increase in susceptibility to strain. When rigid immobilization systems are used in the lumbar segment, the flexibility is decreased even further beyond the natural motion restriction of that segment. Replacing the conventional rigid immobilization systems with certain embodiments disclosed herein may generally restore a more natural movement and provide added support to the strain-susceptible area. 
       FIGS. 1-8  illustrate the different views of one particular embodiment of the present invention. The intervertebral fusion implant as shown in  FIGS. 1-8  is a stand-alone anterior lumbar interbody fusion device used to provide structural stability in skeletally mature individuals following discectomies. These implants are available in various heights and geometric options to fit the anatomically needs of a wide variety of patients. Specifically,  FIGS. 1-4  illustrate one embodiment of an intervertebral fusion implant  10  according to the present invention. Implant  10  is generally positioned in the intervertebral space between two adjacent vertebrae. As shown in the figures, implant  10  primarily incorporates a spacer portion  12  and a plate portion  14 . In this particular embodiment, the spacer portion  12  includes a graft window  16  for the placement of bone graft to enhance fusion between two adjacent vertebrae. The plate portion  14  includes at least one screw hole  18 , however, in the preferred embodiment of the present invention, three screw holes  18  are provided. Also, in the plate portion  14  of the implant  10 , a screw back out prevention mechanism  20  is provided. There is also provided a coupling means  26  which connect the spacer portion  12  and the plate portion  14  rigidly to each other. The coupling means  26  will be discussed in greater detail with reference to  FIGS. 5-8 . 
     The spacer portion  12  can be comprised of any material that is conducive to the enhancement of fusion between the two adjacent vertebrae. In one particular embodiment, the spacer portion  12  is made of PEEK material which is physiologically compatible. It should be noted that any other material that are physiologically compatible may also be used. The spacer portion  12  contains tantalum pins that enable radiographic visualization. The spacer portion  12  further comprises superior and inferior portions that are provided with a plurality of pyramidal protrusions  13 . The superior and inferior portions of the spacer portion are bi-convex for greater contact with the vertebral endplates of the adjacent vertebrae. The protrusions  13  can be configured to be any size or shape for further anchoring the spacer portion  12  to each of the adjacent vertebrae. Protrusions  13  on the superior and inferior surfaces of each implant grip the endplates of the adjacent vertebrae to aid in expulsion resistance. 
     The plate portion  14  can also be comprised of any physiologically compatible material. In the preferred embodiment, the plate portion of the implant  10  is composed of titanium. The plate portion  14  as illustrated in  FIG. 1 , are provided with three screw holes. However, it should be noted that implant  10  may be comprised of only one screw hole. The screw holes  18  are situated both in the spacer portion  12  and the plate portion  14  for receiving bone screws which are attached to the adjacent vertebral bodies at different angles. 
       FIG. 5  illustrates an exploded view of the intervertebral stand along fusion device  10 . In this exploded view, clearer view of the combination of the plate portion  14  and the spacer portion  12  is illustrated. The spacer portion  12  and the plate portion  14  are coupled to each other view connection points  24  and through the use of connection pins  26  and  28 . 
       FIGS. 6-8  illustrate the fusion device  10  in various views associated with the screws  30  provided in screw holes  18 . The screw holes  18  are configured to receive screws  30  at various angles. The screws  30  enter the screw holes  18  at specified angles to enter the adjacent vertebral bodies at the optimal locations. The screws  30  are configured and adapted to provide optimal purchase with the adjacent vertebral bodies. 
     Now, turning to the method of positioning the implant, it should be noted that the intervertebral implant  10  is positioned in the spine after the disc portion between two vertebral bodies is exposed and removed using rongeurs and other suitable instruments. The posterior and lateral walls of the annulus are generally preserved to provide peripheral support for the implant and graft materials. A trial device attached to a trial holder is then inserted into the disc space to determine size of the implant. This procedure is generally conducted using fluoroscopy and tactile feel. After the appropriate sized implant is selected and attached to an implant holder and drill guide, the implant may be inserted into the disc space. Once the implant is positioned with the disc space, supplemental graft material can used to enhance fusion. Once the implant is positioned inside the disc, an awl or any similar type of instrument can be used to drill through the screw hole and break the cortex of the adjacent vertebral body. The surgeon performing this procedure may then use a depth gauge to determine the screw length. Once the appropriate screw length is determined, screws are inserted using a self-retaining screwdriver. After the screws are finally inserted and secured thereby providing solid purchase with the adjacent vertebral bodies, the screw anti-back out mechanism is engaged and secured. In this particular embodiment, the anti-back out mechanism is two set screws that retain the three screws with the implant. It should be noted that the implant may be implanted in the vertebral space using an anterior, posterior and/or lateral approach. 
       FIG. 9  illustrates a perspective view of the zero-profile intervertebral implant  32  for positioning in the cervical region of the spine. The present invention relates to an implant having a peek spacer portion  33  that is coupled to a titanium plate portion  34  through the use of titanium dowel pins  39 . However, it should be noted that the titanium plate portion  34  and the peek spacer portion  33  maybe coupled through any other feasible means such as hooks, screws, and any other type of fastening means. The implant  32  also allows for at least two titanium screws  36  and  37  to be inserted at a compound angle for maximum screw purchase into the superior and inferior vertebral bodies. A locking mechanism  38  is provided on the plate portion  34  to capture the sides of both of the at least two screws  36  and  37  with a 90 degree turn preventing the titanium screws  36  and  37  from backing out. It should be noted that the present application is not limited to being of a PEEK spacer and a titanium plate. Other materials that are physiologically compatible which are similar and which may be unique to spacers and plates may be utilized in various combinations. 
       FIGS. 10 and 11  illustrate the front view of the plate portion of the implant. Specifically,  FIGS. 10 and 11  illustrate a closed and an open position respectively with reference to the anti-back out mechanism  38 . Also, it should be noted that the titanium plate  34  is provided with knife like edges  35  which are designed to engage the vertebral body and provides additional torsional stability to that of the bone screws. The plate  35  is also provided with “eye brow” like structure which fully captures the bone screws  36  and  37  while still allowing for the screws to reside about the tooth root plane and remaining lower than the tooth (protrusions on the spacer portion  33 ). The plate  35  geometry allows for the minimum reduction of peek volume. The plate  35  height remains level to the peek tooth root so that compressive loads are always subjected to the peek body where the graft is contained. Compound holes are drilled to accept bone screws  36  and  37  and to allow for fixed or variable angle screws. The anti-back out mechanism is engaged so that the screws  26  and  37  do not back out of the implant  32 . 
       FIG. 12  illustrates an exploded view of the intervertebral implant. The plate portion  34  and spacer portion  33  have at least 2 male and female ledges which are capable of interfacing with each other. The connection of the male and female ledges are offset at different heights to minimize cross-sectional area loss. Also illustrated in  FIG. 12  is the dowel pins used to connect the spacer portion to the plate portion as one means of coupling of the spacer portion  33  and the plate portion  34 . It should be noted that various means such as hooks, staples and screws can be used to attach the spacer portion to the plate portion of the present invention. 
     The spacer portion  33  of the implant provides a leading edge chamfer which enables self distraction of the vertebral bodies while inserting. The spacer portion  33  also provides teeth like structures in the superior and inferior aspects of the spacer body to help prevent migration of the implant. The root of the teeth or protrusions on the base of the implant serves as the defining plane for the superior and inferior vertebral bodies. Finally, the spacer portion  33  provides an axial shaped hole which enables a maximum amount of graft for packing within the implant. However, it should be noted that the graft hole can be designed to be multiple holes or any in other geometrical shape to enhance fusion through the insertion of graft material. 
       FIGS. 13-16  illustrate an intervertebral implant for positioning in the intervertebral space using a lateral approach. The intervertebral implant  40  consists of a spacer portion  42  and a plate potion  44 . The spacer portion and the plate portion are configured to be able to receive screws  46  and  48  for attachment to adjacent vertebral bodies. The spacer portion  42  and the plate portion  44  are rigidly coupled together through a coupling means  52 . The plate portion  44  is provided with an anti-back out mechanism  50  so that the screws  46  and  48  are fixedly retained within the fusion device  40 . 
       FIG. 17  illustrates another embodiment of an intervertebral implant  60  that is positioned into the disc space laterally. In this embodiment, which is similar to the embodiment disclosed in  FIGS. 13-16 , the spacer portion  62  is provided with a plurality of protrusions in the superior and inferior portions. These protrusions grip the endplates of the adjacent vertebrae to aid in expulsion resistance. The spacer portion  62  also contains a plate receiving area  63  for receiving the plate portion  64 . The plate receiving area  63  is configured to receive a plate protrusion  66  for coupling the spacer portion  62  and the plate portion  64  together through the use of pins or any other similar type of coupling means. The spacer portion  62  and the plate portion  64  are rigidly coupled together through the use of the coupling means. 
     The plate portion  64  is configured with at least two screw holes for receiving screws  68 . The screws  68  are positioned at angles to insert through the spacer and the adjacent vertebral body to gain maximum purchase and stability. The screws  68  are retained with the implant  60  through the use of an anti-screw back out mechanism  70 . When this mechanism is engaged by turning at least 90 degrees through the use an instrument such as a screwdriver, the screws  68  are maintained within the implant and the boney structure of the adjacent vertebral bodies. 
     While it is apparent that the invention disclosed herein is well calculated to fulfill the objects stated above, it will be appreciated that numerous modifications and embodiments may be devised by those skilled in the art.