Abstract:
A system, device, and method are disclosed for anterior intervertebral fusion with fixation. An intervertebral fusion with fixation device includes a spacer configured to fit into a disc space between plural vertebrae, the spacer including through holes between and through plural sidewalls. A first fixating element is rigidly preloaded in a first portion of the spacer along a first linear trajectory. A second fixating element is rigidly preloaded in a second portion of the spacer along a second linear trajectory. An integrated drill and screwdriver instrument is adapted to extend through a cannula of the first fixating element and second fixating element and penetrate the vertebra. The instrument is further adapted to drive the head of the first fixating element and second fixating element into the vertebra and lock the first fixating element and second fixating element with respect to the spacer to prevent extrusion from the spacer.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. Non-Provisional Application No. 13/371,242 filed Feb. 10, 2012, which claims the benefit of U.S. Provisional Application No. 61/463,239, filed on Feb. 15, 2011, and U.S. Provisional Application No. 61/517,717, filed on Apr. 25, 2011, the entire contents of which is hereby incorporated by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to spinal implants and associated instrumentation. Various embodiments are directed to an anterior intervertebral fusion with fixation system, device and method. 
       BACKGROUND 
       [0003]    A healthy spinal disc (intervertebral disc) is a fibroelastic structure with a non-compressible viscous center that articulates adjacent vertebrae. Due to its deformable geometry, the disc not only supports normal functional loads of the human body, but also evenly distributes the stresses applied during body movement and positioning. The disc interfaces with associated superior and inferior vertebrae via large surface areas known as vertebral endplates. Normally, vertebral endplates are thin regions of dense bone (e.g. 1 mm-3 mm) that support high stresses at articulating junctions. 
         [0004]    Intervertebral discs and adjacent articulations progressively deteriorate with age. This natural degenerative process results in various degrees of pathological changes, mostly affecting the geometry and elasticity of a vertebral disc. In severe cases, reduced disc volume results in foraminal compression that mechanically irritates nerve roots and causes neurocompressive syndrome. This often causes severe chronic pain that can only be resolved surgically. 
         [0005]    Historically, surgical treatment of degenerative spinal disc disease required fusion, which immobilizes two adjacent vertebral bodies (vertebrae) to prevent motion-sensitive pain and inflammation. This is accomplished by distracting the vertebrae to a healthy disc height, inserting a disc implant and allowing bone to grow between and through the disc implant until the vertebrae fuse into a solid bony structure. To facilitate proper healing under normal conditions of motion, the disc implant is used to maintain temporary positioning until the bone achieves fusion. The implant is secured to the vertebrae using fixation elements. 
         [0006]    The effectiveness of the disc implant can be evaluated with the following criteria: (i) its ability to restore and maintain normal disc height and curvature; (ii) its ease of delivery and fixation to the disc space; (iii) its ability to facilitate fusion of associated vertebrae; and (iv) its ability to restrict movement of associated vertebrae. 
         [0007]    Disc implants share the same fundamental characteristics to meet the effectiveness criteria. Implants aim to restore disc height through the use of variable geometries. Lordotic curvature is preserved through the use ergonomic designs that conform to spinal curvature and height between the vertebrae. Also, the disc implants are sufficiently porous or hollow to promote the growth of vertebral bone into and through the implant. However, independently, these implants can only restrict spinal flexion and intervertebral compression. Any excessive lateral, sliding, or extension motion may cause device failure and/or extrusion. To avoid this risk, it is customary to provide additional fixation of the disc implant to the vertebrae. 
         [0008]    Devices and systems may integrate fixating members directly into the disc implant. These implants have garnered the nickname “standalone” due to their ability to self-fixate without the use of secondary fixation elements. In the foregoing standalone implants, obtrusive fixation elements are delivered directly through implant pilot openings into the vertebra, which fixate the implant to the vertebrae and prevent implant failure under remaining ranges of motion (e.g., lateral, sliding, extension). Nevertheless, during these motions, connectivity between fixation elements and vertebrae may become weakened causing the fixation elements to slip or extrude out of the implant. To prevent unwanted fixation element slipping or extrusion, it is customary to include a locking mechanism for the implant. 
       SUMMARY 
       [0009]    In an embodiment, an intervertebral fusion with fixation device is disclosed. The device includes a spacer with an insertion wall, a trailing wall opposite to the insertion wall, a first lateral wall, a second lateral wall opposite to the first lateral wall, a top surface, and a bottom surface opposite to the top surface. The intervertebral fusion with fixation device further includes a first fixating element rigidly preloaded in a first portion of the spacer along a first linear trajectory, the first fixating element configured to penetrate and secure to a first vertebra by advancing along the first linear trajectory. The device also includes a second fixating element rigidly preloaded in a second portion of the spacer along a second linear trajectory that is different from the first linear trajectory, the second fixating element configured to penetrate and secure to a second vertebra by advancing along the second trajectory. Further, the intervertebral fusion with fixation device includes a through opening having an entrance proximate the top surface and an exit proximate the bottom surface to facilitate contact and in-growth of bone fusion material with the first vertebra and second vertebra. 
         [0010]    In another embodiment, an integrated drill and screwdriver instrument is disclosed. The integrated drill and screwdriver includes a handle, a driving element configured to engage a head of a bone screw and rotate the bone screw into a vertebra, and a drilling element extending from the from the driving element. The drilling element is configured to extend through a cannula of the bone screw and to penetrate the vertebra. The driving element is configured to engage the head of the bone screw as the drilling element penetrates through a vertebral endplate. 
         [0011]    In a further embodiment, an intervertebral fusion with fixation system is disclosed. The system includes an intervertebral fusion with fixation device configured to be implanted between plural vertebrae. The device includes a spacer with an insertion wall, a trailing wall opposite to the insertion wall, a first lateral wall, a second lateral wall opposite to the first lateral wall, a top surface, and a bottom surface opposite to the top surface. The device further includes a first fixating element rigidly preloaded in a first portion of the spacer along a first linear trajectory, the first fixating element configured to penetrate and secure to a first vertebra by advancing along the first linear trajectory. Additionally, the device also includes a second fixating element rigidly preloaded in a second portion of the spacer along a second linear trajectory that is different from the first linear trajectory, the second fixating element configured to penetrate and secure to a second vertebra by advancing along the second trajectory. The system also includes an integrated drill and screwdriver instrument. The integrated instrument includes a handle, a driving element configured to engage a head of a bone screw and rotate the bone screw into a vertebra, and a drilling element extending from the from the driving element. The drilling element is configured to extend through a cannula of the bone screw and to penetrate the vertebra. The driving element is configured to engage the head of the bone screw as the drilling element penetrates through a vertebral endplate. 
         [0012]    In yet another embodiment, a method to secure plural vertebrae is disclosed. The method includes implanting an intervertebral fusion with fixation device between plural vertebrae. The fusion with fixation device includes a spacer, a first fixating element rigidly preloaded in a first portion of the spacer along a first linear trajectory, and a second fixating element rigidly preloaded in a second portion of the spacer along a second linear trajectory that is different from the first linear trajectory. The method further includes driving the first fixating element along the first linear trajectory to penetrate the first vertebra and to secure the spacer to a first vertebra, and driving the second fixating element along the second linear trajectory to penetrate the second vertebra and to secure the spacer to a second vertebra. The method also includes extending an integrated drill and screwdriver instrument through a cannula of the first fixating element and a cannula of the second fixating element, drilling the plural vertebrae with a drilling element, engaging the first fixating element and second fixating element with a driving element as the drilling element penetrates through a vertebral endplate of the plural vertebrae, and rotating the first fixating element and second fixating element via the driving element to penetrate the plural vertebrae and to secure the spacer to the plural vertebrae. The method further includes locking the first fixation element and second fixation element with respect to the spacer to prevent the first fixation element and second fixation element from extruding from the plural vertebrae and from the spacer. 
         [0013]    In a further embodiment, a method to assemble an intervertebral fusion with fixation device is disclosed. The method includes rigidly preloading a first fixating element in a first portion of a spacer along a first linear trajectory and a second fixating element in a second portion of the spacer along a second linear trajectory, the first linear trajectory being different from the second linear trajectory. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a perspective view of an example spacer of an intervertebral fusion with fixation device; 
           [0015]      FIG. 2  is a front view of the example spacer shown in  FIG. 1 ; 
           [0016]      FIG. 3  is a side view of the example spacer shown in  FIG. 1 ; 
           [0017]      FIG. 4  is a perspective view of an example fixation element of the intervertebral fusion with fixation device; 
           [0018]      FIG. 5  is a cross-sectional side view of the example fixation element show in  FIG. 4 ; 
           [0019]      FIG. 6  is a side view of an example integrated drill and screwdriver driving instrument; 
           [0020]      FIG. 7  is a perspective exploded view of a tip of the example integrated drill and screwdriver drilling tip shown in  FIG. 6 ; 
           [0021]      FIG. 8  is a perspective view of an example intervertebral fusion with fixation device with the example fixation elements shown in  FIG. 4  preloaded in the example spacer shown in  FIG. 1 ; 
           [0022]      FIG. 9  is a perspective view of the example intervertebral fusion with fixation device of  FIG. 8  with the example integrated drill and screwdriver of  FIG. 6  actuating a fixation element shown in  FIG. 4 . 
           [0023]      FIG. 10  is a translucent perspective view of an example intervertebral fusion with fixation device with the example fixation element of  FIG. 4  in a locked position within a vertebra. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIG. 1  is a perspective view of an example spacer  100  of an intervertebral fusion with fixation device. The intervertebral fusion with fixation device is illustrated in  FIG. 8 . The spacer  100  is made of a weight-bearing material, such as a polymer, metal, ceramic, biological material, or composite thereof, that is capable of withstanding the normal stresses of bodily movement and positioning, while also allowing sufficient elasticity. The material can have a flexural modulus and tensile strength comparable to bone. For example, the spacer  100  can be made of polyetheretherketone (PEEK), a thermoplastic with a flexural modulus of 4.2 GPa and a tensile strength of 95 MPa. Another benefit of PEEK is its high level of biocompatibility in a dynamic and immunoreactive environment. Other materials and combinations of materials are possible. 
         [0025]    The spacer  100  includes an insertion wall  110 , trailing wall  112 , lateral walls  106 ,  108 , top surface  102 , bottom surface  104 , and through opening  114  extending between and through the top surface  102  and bottom surface  104  for bone graft insert. 
         [0026]    In various embodiments, the dimensions of the spacer  100  are approximately the following: the length of the spacer  100  between an insertion wall  110  and trailing wall  112  is between about 10 mm and 80 mm; the width of the spacer  100  between a first lateral wall  106  and second lateral wall  108  is between about 10 mm and 80 mm; and the height of the spacer  100  between a top surface  102  and bottom surface  104  is between about 4 mm and 30 mm. The foregoing dimensions are non-limiting and are intended to be adjusted depending on the specific spinal anatomy of the patient. 
         [0027]    The opening  114  can have a volume approximately between 0 cm3 and 8 cm3. Other volumes can be provided. While the insertion wall  110 , trailing wall  112 , and lateral walls  106 ,  108  are generally flat surfaces, the top surface  102  and bottom surface  104  may be tapered or curved with respect to one another to conform to intervertebral lordosis or curvature. The lateral walls  106 ,  108  can also have a tapered geometry to conform to intervertebral space. In some embodiments, the angle between the lateral surfaces  106 ,  108  can be from about 0 degrees to about 16 degrees. 
         [0028]    The trailing wall  112  includes a plurality of through holes  202  (shown in  FIG. 2 ) extending from the central opening  114  to the exterior of the spacer  100  to receive, secure, and guide plural fixation elements  400  (shown in  FIG. 4 ). Each of the foregoing holes  202  is oriented to provide a trajectory for a fixation element (shown in  FIG. 4 ). The trajectories of the holes  202  can be oriented in directions lateral, medial, superior, inferior, or any combination thereof to the spacer to provide multi-axial fixation to the vertebrae. In some embodiments, the holes  202  can direct the fixation elements  400  in divergent trajectories to counterbalance one another from any opposing torques or shear stresses initiated by vertebral motion. The dimensions of the holes  202  are approximately the following: the medial and/or lateral angle in respect to lateral walls  106 ,  108  is between about 0 degrees and 25 degrees, and the superior and/or inferior angle in respect to surfaces  102 ,  104  is between about 30 degrees and 50 degrees. The diameters of the foregoing holes  202  are approximately between 0.5 mm and 10 mm. 
         [0029]      FIG. 2  is a front view of the example spacer  100  shown in  FIG. 1 . Now with reference to  FIGS. 1 and 2 , the spacer  100  includes ridges  116  on surfaces  102 ,  104  proximate the holes  202  to reinforce the spacer  100  during advancement of the fixation elements  400 . For example, ridges  116  can be provided about the exits to the outside of the spacer  100  and can be of various dimensions and tapers along the surfaces  102 ,  104 . In some embodiments, the ridges  116  can be omitted. The spacer  100  further includes ridges  118  along the surfaces  102 ,  104  that penetrate surrounding vertebrae during implantation and provide stability to the spacer  100  through micro-scale contact with the vertebral plates. 
         [0030]    The spacer  100  can include plural radiopaque markers  120  to enhance radiographic visualization of the spacer  100 . The markers  120  can be made of a biocompatible radiopacic material, such as tantalum, platinum alloys, gold alloys, or palladium alloys. Other applicable materials may also be employed. Plural markers  120  can be provided near the walls  106 ,  108 ,  110 ,  112  and surfaces  102 ,  104  to provide additional visual references of the spacer  100  for clinicians during radiographic imaging. Furthermore, the markers  120  can assume various geometries and volumes within the spacer  100  depending on visualization requirements. In various embodiments, the markers  120  can be omitted. 
         [0031]      FIG. 3  is a side view of an example spacer  100  of an intervertebral fusion with fixation device of  FIG. 8 . In a particular embodiment, the trailing height  302  gradually decreases to the insertion height  304  at a taper to approximate natural lordosis. Additionally, the ridges  116  can be also tapered to minimize friction during insertion and facilitate smooth entry of the spacer  100  into the intervertebral space. 
         [0032]      FIG. 4  is a perspective view of an example fixation element  400 . In a particular embodiment, the fixation element  400  can be made of a biocompatible metal, such as a titanium alloy. Other applicable materials may also be employed. The fixation element  400  includes a tip  405  that locks into and interfaces with the holes  202  during assembly to maintain a preloaded position, and penetrates bone during engagement with vertebral endplates. The fixation element  400  has a minor diameter  402  that is between about 1 mm and 10 mm. The fixation element  400  also includes a major diameter  404  of threading that is between 2 mm and 15 mm to provide cutting during engagement. 
         [0033]    Additionally, the tip  405  includes flutes  406  to facilitate penetration into the vertebra during initial engagement. The fixation element  400  further includes a head  407  with a conically shaped body  408  to pressure-fit into the holes  202  after advancement via an instrument receiver  410 . The instrument receiver  410  can interface with a driving instrument (shown in  FIG. 6 ). In a particular embodiment, the head  407  includes a hook protrusion  412  with a sharp edge that can cut into the hole  202  after the fixation element  400  is advanced (e.g., fully) into the vertebra and the head  407  is in contact with the spacer  100 . The contact between the sharp edge of the hook protrusion  412  and the hole  202  functions as a locking mechanism to prevent extrusion of the fixation element  400 . 
         [0034]      FIG. 5  is a cross-sectional side view of an example fixation element  400  of  FIG. 4 . As illustrated, the fixation element  400  includes a cannula  502  that allows a drilling tip of the driving instrument (shown in  FIG. 6 ) to pass into and through the fixation element  400  to facilitate vertebral endplate pre-drilling and preparation for advancement of the fixation element  400 . The fixation element  400  further includes a platform  504  that connects or interfaces the driving instrument receiver  410  and cannula  502  to contact and limit the depth of motion of the driving instrument (shown in  FIG. 6 ) in relation to the fixation element  400 . 
         [0035]      FIG. 6  is a side view of an example integrated drill and screwdriver driving instrument (driving instrument)  600 . In a particular embodiment, the driving instrument  600  can be made of a metal, such as titanium. Other applicable materials may also be employed. The driving instrument  600  includes an integrated tip  614  that can penetrate and pre-drill vertebral endplates with a drill tip  606  as well as engage the driving instrument receiver  410  of a fixation element  400  with a fixation element interface  604 . 
         [0036]    The drill tip  606  of the integrated tip  614  can pass into and through the cannula  502  of the fixation element  400  in order to penetrate and pre-drill a vertebral endplate. The fixation element interface  604  can contact the driving instrument receiver  410  once the drill tip  606  has penetrated through the vertebral endplate into the softer bony layer. In a particular embodiment, both the fixation element interface  604  and corresponding driving instrument receiver  410  are of a quadrilateral shape to facilitate rigid contact between the surfaces and allow engagement of the fixation element  400 . 
         [0037]    The driving instrument  600  includes a body  602  to increase operational distance from the spacer  100  and provide access under various angulations. The body  602  is smoothly mated to the integrated tip  614  with a conical transition element  610 . Furthermore, the driving instrument  600  includes a handle  612  that can be operated manually or by an electrical or mechanical tool. In a particular embodiment, the handle  612  can be constructed as a hexagonal bit to fit a standard screwdriver. The handle  612  is smoothly mated to the body  602  with a conical transition element  603 . 
         [0038]      FIG. 7  is an exploded perspective view of the example integrated tip  614 . The integrated tip  614  includes cutting blades  702  to facilitate vertebral penetration during advancement. The integrated tip  614  further includes a rounded transition element  704  between the fixation element interface  604  and the drill tip  606  to allow smooth contact between the fixation element interface  604  and driving instrument receiver  410  during the initial engagement of the fixation element  400 . 
         [0039]      FIG. 8  is a perspective view of an example intervertebral fusion with fixation device  800  with the plural example fixation elements  400  of  FIG. 4  preloaded in the example spacer  100  of  FIG. 1 . As illustrated, the fixation elements  400  can be preloaded into the spacer  100  via holes  202 . The flutes  406  and threading  404  cut into and secure the fixation elements  400  to the spacer  100  via holes  202  to maintain a preloaded assembly. This preloaded assembly ensures fixed trajectories for the fixation elements  400  during delivery of the device  800  and eliminates the need for alignment post-implantation. 
         [0040]      FIG. 9  is a perspective view of an example intervertebral fusion with fixation device of  FIG. 8  with an example driving instrument  600  of  FIG. 6  actuating a fixation element  400  of  FIG. 4 . As illustrated, the integrated tip  614  is delivered into and through the cannula  502  of the fixation element  400  to pre-drill the vertebral endplate with the cutting blades  702  of the fixation element  400 . The penetration of the integrated tip  614  through the vertebral endplate combined with the linear force applied to the handle  612  drives the fixation element interface  604  into contact with the driving instrument receiver  410  of the fixation element  400 . Simultaneously, the torque from the handle  612  engages the fixation element interface  604 , which in turn actuates the driving instrument receiver  410  and advances the fixation element  400  into vertebral endplate. Additionally, the fixation element flutes  406  and major threading  404  penetrate and secure the fixation element  400  to the endplate of the vertebra. 
         [0041]      FIG. 10  is a translucent perspective view of an example intervertebral fusion with fixation device  800  with the plural example fixation elements  400  of  FIG. 4  in a locked position and secured to a vertebra  1001 . In a particular embodiment, the hook protrusion  412  of the fixation element  400  pressure fits the holes  202  of the spacer  100  to prevent the fixation element  400  from toggling and backing-out. Furthermore, the hook protrusion  412  rigidly cut into the spacer  100  via its sharp edge to limit the ability of the fixation element  400  to torque towards the trailing wall  112  of the device  800  and away from the vertebra  1001 . Additionally, the ridges  118  penetrate adjacent vertebral endplates and provide ancillary stability. 
         [0042]    Other apparent modifications and configurations of the invention will be appreciated by those skilled in the art to allow varying applications of the disclosed embodiments without departing from the scope of the embodiments described herein. The disclosed specifications and principles are intended to be used for illustrative purposes only, with the true scope and spirit of the patent document being defined by the following claims.