Abstract:
A unique, universal Zero-Profile Expandable Intervertebral Spacer (ZP-EIS) device for fusion and distraction throughout the entire spine is provided which can be inserted via anterior, anterolateral, lateral, far lateral or posterior surgical approaches dependent on the need and preference. Multiple ZP-EIS embodiments each with unique mechanisms of calibrated expansion are provided. Two of these embodiments incorporate bi-directional fixating transvertebral (BDFT) screws and five other embodiments do not incorporate BDFT screws. A tool for implantation into the intervertebral device and calibrated device expansion is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation-in-part Application of each of co-pending application Ser. No. 13/210,150, filed on Aug. 15, 2011, co-pending application Ser. No. 13/210,157, filed on Aug. 15, 2011, co-pending application Ser. No. 13/210,162, filed on Aug. 15, 2011, co-pending application Ser. No. 13/210,168, filed on Aug. 15, 2011, co-pending application Ser. No. 13/741,361, filed on Jan. 14, 2013, each of which is a Continuation Application of application Ser. No. 13,084,543, filed on Apr. 11, 2011, now U.S. Pat. No. 8,353,913 issued on Jan. 15, 2013, which is a Divisional Application of application Ser. No. 11/842,855, filed on Aug. 21, 2007, now U.S. Pat. No. 7,942,903 issued on May 17, 2011, and a Continuation Application of application Ser. No. 13,108,982, filed on May 16, 2011, which also is a Continuation Application of application Ser. No. 11/842,855, filed on Aug. 21, 2007, now U.S. Pat. No. 7,942,903 issued on May 17, 2011, which is a Continuation-In-Part Application of application Ser. No. 11/536,815, filed on Sep. 29, 2006, now U.S. Pat. No. 7,846,188 issued on Dec. 7, 2010, which is a Continuation-In-Part Application of application Ser. No. 11/208,644, filed on Aug. 23, 2005, now U.S. Pat. No. 7,704,279 issued on Apr. 27, 2010, for which priority is claimed under 35 U.S.C. §120; and this application also claims priority under 35 U.S.C. §119(e) of U.S. provisional application No. 61/801,783, filed on Mar. 15, 2013, U.S. provisional application No. 61/718,707, filed on Oct. 25, 2012, and U.S. provisional application No. 60/670,231, filed on Apr. 12, 2005; the entire contents of all the above identified patent applications are hereby incorporated by reference. 
     U.S. patent application Ser. No. 13/084,543, filed on Apr. 11, 2011, Ser. No. 11/842,855, filed on Aug. 21, 2007, Ser. No. 11/536,815, filed on Sep. 29, 2006, and Ser. No. 11/208,644, filed on Aug. 23, 2005, each claim the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/670,231, filed on Apr. 12, 2005, and this application hereby incorporates the claim of priority to this provisional application under 35 U.S.C. §119(e) from the aforementioned intermediate applications (for which priority of each intermediate application is claimed under 35 U.S.C. §120); and the entire contents of all of the above identified patent applications are hereby incorporated by reference in their entirety. 
    
    
     FIELD OF DISCLOSURE 
     The present invention relates to unique, universal Zero-Profile Expandable Intervertebral Spacer (ZP-EIS) devices for fusion and distraction throughout the entire spine which can be inserted via anterior, anterolateral, lateral, far lateral or posterior surgical approaches dependent on the need and preference. Multiple ZP-EIS embodiments each with unique mechanisms of calibrated expansion are presented. Two of these embodiments incorporate bi-directional fixating transvertebral (BDFT) screws and five other embodiments do not incorporate BDFT screws. A universal tool for their intervertebral placement and device expansion is also described. 
     The ZP-EIS embodiments with incorporated BDFT screws can be used as stand-alone intervertebral devices. These exemplary embodiments combine the dual functions of intervertebral calibrated expandable distraction, and segmental vertebral body spinal fusion. These embodiments can include bone cavities which can be filled with bone fusion material(s) to promote segmental spinal fusion. 
     The calibrated ZP-EIS embodiments without incorporated BDFT screws can also be used as stand-alone devices for calibrated intervertebral expansion and segmental vertebral body fusion. The exemplary devices can include bone cavities which can be filled with bone fusion material. If desirable, the exemplary devices can be supplemented with other forms of screw stabilization. 
     The exemplary ZP-EIS embodiments, especially those with incorporated BDFT screws, may obviate the need for supplemental pedicle screw fixation in many situations. The exemplary embodiments allow nuanced, fine-tuned incremental and calibrated distraction of the disc space to allow nerve root decompression in a minimally invasive and safe manner, as well as promoting segmental spinal fusion. 
     In the related applications in the Cross-Reference to Related Applications, Applicants first introduced the terminology “zero-profile” relating to spinal fusion devices. Applicants also have described zero-profile non-expandable and expandable stand-alone intervertebral spinal fusion device embodiments with incorporated BDFT screws. As described in greater detail below, exemplary embodiments of advanced ZP-EIS devices with BDFT screws are provided which have an improved contoured body with tapered edges to more precisely insert into and conform to the biconcave disc space. The present application also provides exemplary embodiments of more advanced ZP-EIS devices without accompanying BDFT screws each with very unique calibrated expandable mechanisms allowing minimally invasive intervertebral expansion, vertebral body distraction and segmental spinal fusion. An exemplary embodiment of a universal tool also is described that can be adapted to implant one or more (e.g., all) of the intervertebral device embodiments herein described into the intervertebral space, and mechanically expand them. 
     BACKGROUND 
     The history and evolution of instrumented spinal fusion in the entire human spine has been reviewed in Applicants&#39; copending applications set forth in the Cross-Reference to Related Applications (for example in U.S. Ser. No. 11/536,815, filed on Sep. 29, 2006, and Ser. No. 11/208,644, filed on Aug. 23, 2005). Currently, the majority of spinal fusion techniques are typically supplemented with posterior pedicle screw placement and/or anterior (or lateral) plating. Complications of pedicle screw placement in the spine may include duration of procedure, significant tissue dissection and muscle retraction, misplaced screws with neural and/or vascular injury, excessive blood loss, need for transfusions, prolonged recovery, incomplete return to work, and excess rigidity leading to adjacent segmental disease requiring further fusions and re-operations. Recent advances in pedicle screw fixation including minimally invasive and image-guided technology, and the development of flexible rods, imperfectly may address some but not all of these issues. 
     Anterior/and or lateral plating because of the plates&#39; elevated profiles can be complicated by esophageal, or major vascular injury. The zero-profile devices described herein with reference to the exemplary embodiments avoid these complications. 
     Current non-expandable intervertebral spacers must be manufactured with different heights, and the most appropriate sized spacer is selected for insertion. In these situations, the vertebral bodies are forcefully distracted to allow placement of an imperfectly fitting spacer. These are most often supplemented with pedicle screw and/or or plate fixation. 
     SUMMARY 
     The exemplary embodiments described herein can allow a more precisely tailored complimentary fit between spacer and disc space, allowing the spacer to expand gradually in a calibrated manner, and to incrementally achieve the precise fit and degree of distraction desirable. Thus, the process according to the present invention can be more individualized for every patient and apply less forceful disruption to the intervertebral space thereby improving safety and enhancing effectiveness of the placement of intervertebral spacers. The exemplary embodiments are zero-profile, and thus, do not damage or indent overlying soft tissue or vascular structures further decreasing morbidity. 
     Herein described are exemplary embodiments of multiple ZP-EIS devices which combine in a single construct the dual functions of calibrated expandable intervertebral spacer distraction maintaining disc space height, and simultaneous segmental vertebral body spinal fusion. 
     To achieve safe, effective zero-profile and minimally invasive segmental spinal fusion, the exemplary embodiments of the present invention use of novel zero-profile calibrated expandable spacer (ZP-EIS) devices with or without BDFT screws which can be strategically inserted into the intervertebral disc space via anterior, anterio-lateral, lateral, far lateral or posterior surgical approaches. 
     In Applicants&#39; applications set forth in the Cross-Reference to Related Applications, exemplary embodiments are directed to expanding intervertebral spacers which incorporated BDFT screws. One of these embodiments includes two sliding triangular bases to house two screws driven in two opposing directions which can be expanded in two simultaneous directions, height and depth, by turning a built-in screw adjuster. This was facilitated by a combined external drill/screw guide/cage expander to further enhance trajectory precision and to simultaneously expand the screw box in height and depth to custom-fit the individual disc space height. Applicants&#39; copending applications set forth in the Cross-Reference to Related Applications further describe an exemplary embodiment of a universal tool and the adaptability of the tool, for example, to exemplary embodiments of sliding boxes, as well as to the exemplary embodiments described herein, including those with and without BDFT screws. 
     The evolved zero-profile expandable intervertebral spacer (ZP-EIS) embodiments with incorporated BDFT screws presented herein are more finely tapered and contoured to more easily allow insertion and conformation to the biconcave disc space. 
     The exemplary embodiments of ZP-EIS devices without incorporated BDFT screws described herein have the ability to incrementally and uniformly separate and distract the vertebral bodies. Each embodiment has a very unique mechanically designed mechanism of incremental expansion. The devices are all designed with cavities for bone fusion giving the surgeon the option to use these as stand-alone fusion/spacer devices or as supplemental devices if other screw fixation is deemed necessary. These innovations represent a continued evolution of our concept of zero-profile calibrated expandable intervertebral distraction/fusion spacers described in Applicants&#39; applications, for example, as set forth in the Cross-Reference to Related Applications. 
     In the exemplary ZP-EIS embodiments with incorporated BDFT screws, a rostral-directed screw is passed through one built-in screw guide of the device which then is inserted and screwed into the superior vertebral body. Next, a caudally directed screw is passed through an adjacent built-in screw guide, which then is inserted and screwed into the inferior vertebral body. One of many novels features of this design is the built-in prescribed angles of the integral screw guides which allow the transvertebral penetration into the vertebral bodies. This is a truly amazing feat accomplished particularly in the posterior or lateral/far lateral lumbar spine considering the small anatomically restricted work zone within which to work, which is very narrowly prescribed by obtuse angulations between screw and intervertebral bone surfaces, and by nerve root, facet joint and pedicle. Applicants&#39; applications set forth in the Cross-Reference to Related Applications included an angled screw driver specifically designed to fit these devices if a straight screw driver impedes screw placement. Hence, these external tools can provide the means in any circumstance to accomplish precision screw trajectory. 
     The exemplary zero-profile embodiments of the present invention can provide enhanced individualized intervertebral conformation, and multiple methods of finely calibrating intervertebral expansion, and vertebral body distraction further reducing morbidity and enabling more minimally invasive surgical methods of vertebral body distraction and segmental fusion compared to Applicants&#39; applications set forth in the Cross-Reference to Related Applications. 
     The exemplary embodiments of box casings can include perforations to allow bone packing for fusion. These exemplary devices can prevent subsidence. In an exemplary embodiment, both the inside of the denuded intervertebral space, and the devices can be packed with autologous or allograft bone, BMP, DBX or similar osteoconductive material. 
     The zero-profile EIS embodiments, in particular those with incorporated BDFT screws, can provide as strong or stronger segmental fusion as pedicle screws without the complications arising from pedicle screw placement which include screw misplacement with potential nerve and/or vascular injury, violation of healthy facets, possible pedicle destruction, blood loss, and overly rigid fusions. In the case of the posterior Lumbar spine by placing screws across the intervertebral space from vertebral body to vertebral body, engaging anterior and middle spinal columns, and not the vertebral bodies via the transpediclar route, the healthy facet joints, if they exist, are preserved. Because the exemplary techniques accomplish both anterior and middle column fusion, without rigidly fixating the posterior column, the exemplary embodiments in essence create a flexible fusion. This exemplary devices therefore can provide a flexible fusion device because the preserved posterior facet joints retain their function achieving at least a modicum of mobility and hence a less rigid (i.e. a flexible) fusion. 
     The very advantage of transpedicular screws which facilitate a strong solid fusion by rigidly engaging all three spinal columns is the same mechanical mechanism whereby complete inflexibility of all columns is incurred thereby leading to increasing rostral and caudal segmental stress which leads to an increased rate of re-operation. 
     Transvertebral fusion also leads to far less muscle retraction, blood loss, and significant reduction in operating room (O.R.) time. Thus, the complication of pedicular screw pull-out and hence high re-operation rate associated with the conventional flexible fusion pedicle screws/rods is obviated. 
     Although the exemplary embodiments can be supplemented with transpedicular screws, there would be no absolute need for supplemental pedicle screw fixation with these operative techniques. The expandable spacers without BDFT screws can be supplemented with other screw stabilization if desired. 
     Because the exemplary embodiments are zero-profile, these devices also obviate the morbidity involved with profiled anterior or lateral plating. Multi-level fusions can be performed with all of the exemplary embodiments described herein. 
     Currently failed anterior lumbar arthroplasties are salvaged by combined anterior and posterior fusions. The exemplary ZP-EIS embodiments with incorporated BDFT screws could be utilized as a one-step salvage operation for failed/extruded anteriorly placed lumbar artificial discs obviating the above salvage procedure which has far greater morbidity. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       These and other aspects and features of embodiments of the present invention will be better understood after a reading of the following detailed description, together with the attached drawings, wherein: 
         FIGS. 1A-1B  illustrate an exemplary embodiment (Embodiment I) of a non-tapered sliding base ZP-EIS device with incorporated BDFT screws in sagittal-oblique ( FIG. 1A ), and exploded ( FIG. 1B ) views. 
         FIGS. 2A-2D  illustrate an exemplary embodiment (Embodiment II) of a tapered sliding base ZP-EIS device with incorporated BDFT screws in closed ( FIG. 2A ), semi-expanded ( FIG. 2B ), and fully expanded ( FIG. 2C ) positions, and in an exploded view ( FIG. 2D ). 
         FIGS. 3A-3D  illustrate an exemplary embodiment (Embodiment III) of a scissors jack driven ZP-EIS device without incorporated BDFT screws in closed ( FIG. 3A ), semi-expanded ( FIG. 3B ), and fully expanded ( FIG. 3C ) positions, and in exploded view ( FIG. 3D ). 
         FIGS. 4A-4C  illustrate an exemplary embodiment (Embodiment IV) of a tapered thread driven ZP-EIS device without incorporated BDFT screws in closed ( FIG. 4A ), semi-expanded/fully expanded positions ( FIG. 4B ), and in cross-sectional view ( FIG. 4C ). 
         FIGS. 5A-5D  illustrate an exemplary embodiment (Embodiment V) of a dry anchor driven ZP-EIS device without incorporated BDFT screws in closed ( FIG. 5A ), semi-expanded ( FIG. 5B ), and fully expanded ( FIG. 5C ) positions, and in an exploded view ( FIG. 5D ). 
         FIGS. 6A-6D  illustrate an exemplary embodiment (Embodiment VI) of a modified wedge driven ZP-EIS device without incorporated BDFT screws in closed ( FIG. 6A ), semi-expanded ( FIG. 6B ), and fully expanded ( FIG. 6C ) positions, and in an exploded view ( FIG. 6D ). 
         FIGS. 7A-7D  illustrate an exemplary embodiment (Embodiment VII) of a worm drive ZP-EIS device without incorporated BDFT screws in closed ( FIG. 7A ), semi-expanded ( FIG. 7B ), and fully expanded ( FIG. 7C ) positions, and in an exploded view ( FIG. 7D ). 
         FIGS. 7E (i) and  7 E(ii) illustrate top, perspective views of an intervertebral cage construct according to an exemplary embodiment of the invention. 
         FIG. 8A-8C  illustrate a positioning tool/screw guide/box expander in oblique perspective ( FIG. 8A ), lateral ( FIG. 8B ), and exploded ( FIG. 8C ) views according to an exemplary embodiment, which is shown coupled to the exemplary non-tapered sliding base ZP-EIS device illustrated in  FIGS. 1A-1B . 
         FIGS. 8D (i) and  8 D(ii) illustrate superior oblique perspective views of the positioning tool/drill guide/box expander component, according to an exemplary embodiment, which may be optionally used for the exemplary embodiments illustrated in  FIGS. 1A-1B and 2A-2D . 
         FIGS. 8E-8G  illustrate sequential steps (I-III: Step I ( FIG. 8E ), step II ( FIG. 8F ), and step III ( FIG. 8G )) of the positioning tool/screw guide/box expander assembly according to an exemplary embodiment. 
         FIGS. 8H-8I  illustrate three-dimensional views of positioning tools, according to exemplary embodiments, for impaction and placement of two transvertebral screws, for example, of the exemplary embodiments illustrated in  FIGS. 1A-1B and 2A-2D . 
         FIGS. 8J-8K  illustrate the insertion of expandable Lumbar bi-directional screw box with two BDFT screws into the Lumbar spine in oblique ( FIG. 8J ) and lateral ( FIG. 8K ) views. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention now is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     1. The Medical Device 
     Referring now to the drawings,  FIGS. 1A-8K  illustrate exemplary embodiments of ZP-EIS devices that can solve the above described problems and others in the spine by insertion of the ZP-EIS devices into the denuded intervertebral disc space according to the features illustrated in the exemplary embodiments (I-VII). 
       FIGS. 1A-1B  illustrate three-dimensional views of a ZP-EIS device  100  according to embodiment I, with two BDFT screws  101 ,  102 . 
     The expandable ZP-EIS device  100  includes of top and bottom triangular sliding bases  103 ,  104  ( FIGS. 1A-1B ). The superior and inferior segments of the height/depth adjusting screw  105  are integrated and connected to the two separate top and bottom triangular bases  103 ,  104 , respectively. By turning this adjusting (rotation) screw  105  back and forth, i.e. clock-wise, and counter clockwise, the sliding rails  106  of the top triangular base  103  ( FIGS. 1A-1B ) slide up and down the rail inserts  107  on the bottom triangular base  104  ( FIGS. 1A-1B ). This action will simultaneously alter the intervertebral height and depth of the device  100  allowing individualized custom fitting of the ZPEIS device  100  conforming to the dimensions of the disc space. 
     A transvertebral screw  101  penetrates the top base  103 , and a transvertebral screw  102  traverses the bottom base  104  of the screw box (device  100 ). The two screws  101 ,  102  traverse the screw box  100  in opposing directions, bi-directionally. The external edges of the triangular bases  103 ,  104  in contact with vertebral body surfaces can include ridges  107 , which facilitates the ZP-EIS device  100  incorporation into and fusion with the superior and inferior vertebral bodies ( FIGS. 1A-1B ). Both top and bottom ZP-EIS bases  103 ,  104  can be perforated with holes  108  to allow bone placement for fusion. In an exemplary embodiment, the entire construct, furthermore, can be hollow to allow filling with bone filling material. Hence, the exemplary device functions as both an intervertebral bone fusion spacer and bi-directional transvertebral screw fusion device. 
       FIGS. 2A-2D  illustrate a ZP-EIS device  200  according to exemplary embodiment II. This exemplary device  200  incorporates BDFT screws and employs a fusion wedge mechanism of expansion. 
     The device  200  includes a contoured top  208  and bottom  206  housing which have tapered edges and are coupled to each other by a diagonal dovetail interface  204  which constrains the components  208 ,  206  to translate linearly relative to each other. The linear translation causes a vertical separation of the top  208  and bottom  206  housing surfaces which are parallel to each other. The position is secured and adjusted by a threaded rotation screw  220  coupled to a nut  224  and a retaining ring  222  and passed through the top  208  and bottom  206  housing pieces. As the threaded rotation screw  220  is rotated further into the nut  224 , the housing pieces  208 ,  206  expand vertically. 
     By turning this adjusting (rotation) screw  220  back and forth i.e. clock-wise, and counter clockwise, the sliding rails  210  of the top housing piece  208  slide up and down the rail inserts  212  on the bottom housing piece  206 . This action will simultaneously alter the intervertebral height and depth of the device  200  allowing individualized custom fitting of the ZP-EIS conforming to the dimensions of the disc space. A transvertebral screw  101  penetrates the top housing piece  208 , and a transvertebral screw  102  traverses the bottom housing piece  206  of the device  200 . The two screws  101 ,  102  traverse the device  200  in opposing directions, bi-directionally. The external edges of the housing pieces in contact with vertebral body surfaces include ridges  216 . This facilitates the ZP-EIS device  200  incorporation into and fusion with the superior and inferior vertebral bodies ( FIGS. 2A-2D ). Both top and bottom ZP-EIS housing bases  208 ,  206  are perforated with holes  214  to allow bone placement for fusion. The entire device  200 , furthermore, can be hollow to allow bone filling. Hence, the exemplary device  200  functions as both an intervertebral bone fusion spacer and bi-directional transvertebral screw fusion device. 
     The device  200  can include a tapered edge  226  (shown for example in  FIGS. 2A-2B ), which allows easier introduction and insertion of the device  200  into the disc space. 
       FIGS. 3A-3D  illustrate a ZP-EIS device  300  according to exemplary embodiment III, which employs a scissor jack expansion mechanism. 
     In this embodiment the top  302  and bottom  304  housing are attached by one internal linkage arm  310 , and two external linkage arms  308 . The device  300  can include indentations  306  on each lateral side close to the top of the device  300  to mate with the prongs of the universal tool (for example, as described in  FIGS. 8A-8I ) to assist in grasping, inserting and impacting the device  300 . A lead screw or rotation screw  314  is mounted in the bottom housing  304  and secured in place with a retaining ring  316 . When the lead (rotation) screw  314  is rotated by an external tool (for example, as described in  FIGS. 8A-8I ), the screw  314  causes the linear displacement of the separation block  318  which is hinged to the internal linkage  310 . The horizontal motion of the separation block causes the top  302  and bottom  304  housing pieces to separate vertically. The separation distance depends on the amount of rotation of the lead (rotation) screw  314 , and is limited by the freedom of the separation block  318  to move within the bottom housing  304 . The exemplary embodiment can include a plurality of pins, such as eight pins  320 ,  322 ,  324 , to secure the external linkage arms  308  to the top  302  and bottom  304  housing units and to the separation block  318 . The top housing  302  and bottom housing  304  can include one or more cavities  312  for bone incorporation/fusion. 
       FIGS. 4A-4C  illustrate a ZP-EIS device  400  according to exemplary embodiment IV, which employs a tapered thread mechanism of expansion. 
     The exemplary device  400  can include a top housing  402  and bottom housing  404 , which can be attached by one or more pins, such as two pins  412 , which allow rotation of the top housing  402  and bottom housing  404  relative to each other about the axis of the pins  412 . The top housing  402  and/o bottom housing  404  can include indentations  406  on their lateral sides close to the top of the device  400  to mate with the prongs of a tool or universal tool (e.g., prongs  806  in  FIGS. 8A-8I ) to assist in grasping, inserting and impacting the device  400 . The bottom housing  404  can include a mount for the rotation screw  410  ( FIG. 4C ), which can control the relative angular orientation of the two housing pieces  402 ,  404 . When the screw  410  is rotated by an external tool (e.g. as shown in  FIGS. 8A-8I ), the screw  410  engages the internal teeth/ridges  414  of the top housing  402  and acts as a wedge to rotate the top housing  402  away from the bottom housing  404 . More particularly, the device  400  can include a sloped ridge  414 , as exemplary illustrated in  FIG. 4C . When the rotating screw  410  advances, the top housing  402  rotates further and further away from the bottom housing  404 . The device  400  can include one or more bone cavities in the top housing  402  and bottom housing  404  for bone fusion. 
       FIGS. 5A-5D  illustrate exemplary embodiments of a ZP-EIS device according to embodiment V, which employs an anchor mechanism of expansion. 
     The top housing  502  and bottom housing  504  can be coupled or attached by one or more pins, such as two pins  512 , which allow rotation of the top housing  502  and bottom housing  504  relative to each other about the axis of the pins  512 . The top housing  502  and/or the bottom housing  504  can include indentations  506  on their lateral sides close to the top of the device  500  to mate with the prongs of a tool or universal tool (e.g. see  FIGS. 8A-8I ) to assist in grasping, inserting and impacting the device  500 . The bottom housing  504  can include, for example, a mount for the lead (rotation) screw  510 , which can control the relative angular orientation of the two housing pieces  502 ,  504 . The lead (rotation) screw  510  can be secured with one or more retaining rings, such as two retaining rings  518 . When the screw  510  is rotated by an external tool (not illustrated)(e.g., such as the tool shown in  FIGS. 8A-8I ), the screw  510  causes lateral motion of a translation nut  516 , which is attached to two linkage bars  514  to a second nut  516  fixed to the bottom housing. A plurality of pins, such as six pins  512 , can secure the linkage bars or arms  514  to each other and to translation nuts  516 . When the translation nuts  516  move, the linkage bars or arms  514  extend outside of the bottom housing  504 , pushing against the top housing  502 . Alternatively, in other embodiments, the linkage bars or arms  514  can be replaced by a solid material such as spring steel which can bend to produce the same effect. The device  500  can include one or more bone cavities that can be incorporated into the top housing  502  and the bottom housing  504  for bone fusion. 
       FIGS. 6A-6D  illustrate exemplary embodiments of a ZP-EIS device  600  according to embodiment VI which employs a modified wedge expansion mechanism. 
     The device  600  includes a top housing  602  and a bottom housing  604  that can be attached or coupled by one or more pins, such as two pins  612 , which allow rotation of the top housing  602  and the bottom housing  604  relative to each other about the axis of the pins  612 . The top housing  602  and/or the bottom housing  604  can include indentations  606  on their lateral sides close to the top of the device  600  to mate with the prongs of a tool, such as prongs  806  of the universal tool shown in  FIGS. 8A-8I , to assist in grasping, inserting and impacting the device  600 . The bottom housing  604  can include a mount for the lead (rotation) screw  610 , which can control the relative angular orientation of the two housing pieces  602 ,  604 . The lead (rotation) screw  610  can be secured with one or more retaining rings, such as two retaining rings  618 . When the screw  610  is rotated by an external tool (e.g., the tool shown in  FIGS. 8A-8I ), the screw  610  causes lateral motion of a wedge-shaped translation nut  616 . The nut  616  engages an inner tapered surface of the top housing  602  and forces the top housing piece  602  to rotate away from the bottom housing  604 . The device  600  can include one or more bone cavities  608  incorporated into the top housing  602  and/or bottom housing  604  for bone fusion. 
       FIGS. 7A-7D  illustrate exemplary embodiments of a ZP-EIS device  700  according to embodiment VII, which employs a worm drive (gear) mechanism. 
     According to the invention, the device  700  includes a worm drive design that allows a user to rotate a worm gear/drive  712  with an external tool ( FIG. 8 ) to control the translation of the top housing  702  relative to the bottom housing  704   a ,  704   b . The worm gear drive  712  engages a spur gear mount  714  which has internal threading for engaging a corresponding part, such as a threaded stud of bolt  720 , to couple the spur gear mount  714  to the top housing  702 . The top housing  702  can include a plurality of pins, such as four pins  712 , which extend into the bottom housing  704   a ,  704   b . These pins  712  prevent the top housing  702  from rotating with the spur gear  714 , and constrain the spur gear  714  to translate linearly. The bottom housing  704  can include two halves  704   a ,  704   b  to secure the worm drive  710  and spur mount  714  in place. A worm retaining ring and a spur retaining ring  716  also can be used to secure the worm gear drive  710  and the spur gear mount  714 . The device  700  can include one or more bone cavities  708  that are incorporated into the top housing  702  and/or bottom housing  704   a ,  704   b  for bone fusion. The top housing  702  and/or bottom housing  704   a ,  704   b  can include one or more indentations  706  on its lateral sides close to the top of the device  700  to mate with prongs of a tool, such as prongs  806  of the universal tool  800  in  FIGS. 8A-8I , to assist in grasping, inserting and impacting the device  700 . 
       FIGS. 8A-8C  illustrate three-dimensional views of exemplary embodiments of the external drill/screw guide-box expander universal tool  800  which can be used to assist in both screw trajectory and box expansion of an expandible device, such as the exemplary embodiments of devices illustrated in embodiments I and II, and for device expansion of the devices illustrated in embodiments III-VII. The same universal tool  800  can be utilized for all the exemplary embodiments illustrated in embodiments I-VII. In some embodiments, the external drill/screw guide  850  may not be needed or used for embodiments II-VII. The prongs  806  can be inserted into the indentations (e.g.,  202 ,  306 ,  406 ,  506 ,  606 ,  706 ) of the sides of the devices (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ) according to one or all of the exemplary embodiments illustrated in embodiments I-VII, and implant the device into the intervertebral space. Once implanted and impacted, an Allen key (e.g., as shown in  FIG. 8 ) can be used to expand the device (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ) by turning the adjustment (rotation) screw (e.g.,  105 ,  220 ,  314 ,  410 ,  510 ,  610 ,  710 ). 
     The exemplary tool can include, among other things, an Allen key  801 , a spring  802 , a handle  803 , a griper  804  and a screw guide  805 . The Allen key  801 , when inserted in the insertion  814  and turned, can turn the rotation screws (e.g.,  105 ,  220 ,  314 ,  410 ,  510 ,  610 ,  710 ) of one or all of the exemplary embodiments I-VII. The griper  804  includes griper prongs  806 , which insert into grooves  509  of the screw guide  805  and the screw box indentations (e.g.,  202 ) in the exemplary embodiment illustrated in embodiment I (as shown in  FIGS. 8A-8D ), as well as in similar indentations (e.g.,  306 ,  406 ,  506 ,  606 ,  706 ) of devices (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ) illustrated in embodiments II-VII (not shown). 
     As shown in  FIG. 8C , each longitudinal end of the screw box  100  can include a slot or indentation  108  formed adjacent to an edge of an upper surface of the screw box  100  for engaging a protuberant extension of a tool, such as the protuberant extension  807  of the tool  800 . 
       FIG. 8D  illustrates a superior oblique view of the screw guide  805  demonstrating insertions  809  for griper prong  806 , built-in trajectory guides  811 ,  812  for insertion of screws  101  and  102 , and the Allen key  801 . This exemplary embodiment can be limited, for example, to use with the devices of embodiments I and II, which includes BDFT screws. 
       FIGS. 8E-8G  illustrate three-dimensional views of the sequential steps necessary for the external guide assembly.  FIG. 8E  illustrates the insertion of the Allen key  801  into the handle  803 .  FIG. 5F  illustrates the insertion of the handle  803  through the spring  802  and griper  804 .  FIG. 8G  illustrates insertion of the griper  804  into the screw guide  805 . The griper prongs  806  can include medially oriented male protuberant extensions  807  that engage the slot or indentation of a device, such as indentation  108  of device  100 , thereby perfectly aligning the prongs  805  of the tool  800  with the device (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ). This exemplary embodiment can be limited, for example, to use with the devices of embodiments I and II. 
       FIG. 8H  illustrates a three-dimensional view of another exemplary embodiment of a positioning tool  800  for impaction and placement of two transvertebral screws  201 ,  202  for example, for use with the exemplary embodiments I and II. 
     With reference again to  FIGS. 8A-8K , the screw guide  805  can include insertions  809  for receiving the griper prong  806 , built-in trajectory guides  811 ,  812  for insertion of screws  101  and  102 , and the Allen key  801 . 
     The driver assembly  850  can include a screw driver  851 , a flexible shaft  852  and a square recess bit  853 . This exemplary device can facilitate turning the screws  101 ,  102  into the bone. The flexible shaft  852  can facilitate the avoidance of spinous processes which might hinder the screw driving if the shaft  852  were straight. The positioning tool  800  can have a rectangular handle, as shown for example in Embodiment I, or a circular handle, as exemplary shown in Embodiment II. This exemplary embodiment can serve to position a screw box within the intervertebral space, and screws  101 ,  102  within the screw box or device. Once positioned, the screw box or device (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ) can be impacted by tapping the handle  803  with a mallet (not shown). The griper handle  803  inserts into the screw guide and the screw box or device (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ), which maintains alignment. 
     2. The Surgical Method 
     Exemplary embodiments of a surgical method for utilizing the exemplary devices described herein, will now be described. The procedures can be performed open, microscopic, closed tubular or endoscopic. Fluoroscopic guidance can be used with any of these procedures. 
     An exemplary embodiment of a ZP-EIS device, as illustrated in embodiments (I-VII), can be inserted into the intervertebral space (for example as shown in  FIGS. 8J and 8K ) after an adequate discectomy is performed in any disc space throughout the entire spine upon their exposure anteriorly, anterio-laterally, laterally, far laterally or posteriorly. 
     For exemplary embodiments I-II of the ZP-EIS devices can be inserted into the disc space by a tool or universal tool, such as the universal tool  800  in  FIGS. 8A-8I . In operation, the grab prongs of tool  800  can attach to the insets or indentations (e.g.,  202 ,  306 ,  406 ,  506 ,  606 ,  706 ) on the side of the devices. Once in the disc space, the rotation screw (e.g.,  105 ,  220 ,  314 ,  410 ,  510 ,  610 ,  710 ) of each embodiment is turned by rotating the Allen key  801  of the tool  800  to expand the device (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ) to the desirable disc height achieving the desirable intervertebral distraction deemed necessary for the individual patient and disc space. Once this is achieved, BDFT screws  101 ,  102  are inserted and screwed into the vertebral body above and below securing the device (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ) to the vertebral bodies with screws  101 ,  102 . Prior to implantation of the device (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ), the bone cavities of each device can be filled with any type of bone fusion material. 
     For the exemplary embodiments III-VII, the ZP-EIS device (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ) can be inserted into the disc space by the same universal tool, such as tool  800 . The grabs prongs  806  of the tool  800  attach to the insets or indentations (e.g.,  202 ,  306 ,  406 ,  506 ,  606 ,  706 ) on the side of the devices (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ) on the side of the devices (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ). Once in the disc space, the rotation screw (e.g.,  105 ,  220 ,  314 ,  410 ,  510 ,  610 ,  710 ) is turned by rotating the Allen key  801  of the tool  800  expanding the device (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ) to the desirable disc height achieving the desirable intervertebral distraction deemed necessary for the individual patient and disc space. Prior to implantation of the device (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ) the bone cavities of each device (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  700 ) can be filled with any type of bone fusion material. 
     The exemplary embodiments of the present invention may provide effective and safe techniques that overcome the problems associated with current transpedicular and/or plated fusion technology employed for many degenerative stable and unstable spine diseases. These exemplary embodiments may replace much pedicle screw-based and plated based instrumentation in many but not all degenerative spine conditions. 
     The speed and simplicity of the surgical implantation of the exemplary embodiments of the ZP-EIS devices far exceeds that of conventional pedicle screw technology. Furthermore, the exemplary embodiments of zero-profile devices can provide markedly significantly decreased risk of misguided screw placement, and hence decreased risk of neural and vascular injury, and blood loss. The exemplary embodiments can provide decreased recovery and back to work time. The exemplary embodiments of devices may lead to similar if not equal fusion with significantly less morbidity, and hence overall make the exemplary devices a major advance in the evolution of spinal instrumented technology leading to advances in the care of the spinal patient. 
     According to the exemplary embodiments, such as the embodiments in embodiments I and II, an intervertebral fusion device is provided that uses a threaded rod mechanism located at the peripheral of the box to control expansion of the device. The device can include a cavity within the walls for placement of bone material for fusion. 
     In another embodiment, an intervertebral fusion device can include a threaded rod which can obstruct (inhibit) expansion of the device when it is not being turned. The threaded rod can be disposed at the front anterior part of the box or device. 
     In yet another embodiment, an intervertebral fusion device can include a threaded rod, which exerts a clamping force to expand the device until the device properly accommodates the dimensions of the intervertebral disc space and distracts the space based on individual anatomy and surgical judgment. The device can include a cavity for bone in-between the walls of the box. 
     In another embodiment, an expandable intervertebral fusion device can includes indentations on its sides to accommodate a placement tool. 
     In another embodiment, an expandable intervertebral fusion device can be adjusted by using a threaded rod as a wedge to pivot components within the device. The threaded rod can be accessible from the front anterior of the box or device. 
     In another embodiment, an expandable fusion device can include a threaded rod to expand a spacer. The threaded rod can be used as a wedge to mechanically separate the pieces. The threaded rod can be accessible from the front anterior of the box or device. 
     In another embodiment, an expandable fusion device can include wedge components which translate relative to each other along a contact. The degree of expansion can be determined by an adjustment rod located at the peripheral of the box or device. 
     In another embodiment, an expandable fusion device includes components which are mechanically linked together. The expansion of the device is controlled by the user via an adjustment rod coupled to a mechanical transmission that causes mechanical components within the device to separate. The threaded rod is accessible from the front anterior of the box or device. 
     In another embodiment, an expandable fusion device can be provide wherein the position of the device is secured and adjusted by a threaded rod that is mechanically linked to housing pieces. When the threaded rod is rotated, the threaded rod forces the pieces to separate. 
     In another embodiment, an intervertebral fusion device is provide wherein the two internal screw guides are in the top housing unit. 
     In another embodiment, an intervertebral fusion expansile device is provided wherein the center of the two internal screw guides could be in quadrants I and III or II and IV. 
     In another embodiment, an expandable fusion device can be provided that uses a threaded rod (rotation screw) to expand the device using a metal driver as the wedge to mechanically separate the pieces. 
     In another embodiment, an expandable fusion device can be adjusted by using a threaded rod (rotation screw) as a wedge to offset the opposing cages. 
     In another embodiment, an expandable intervertebral fusion device can be provided wherein its position is secured and adjusted by a threaded rod (rotation screw) coupled to a nut and passed through the top and bottom housing pieces. As the threaded rod is rotated further into the nut, the pieces separate. 
     In another embodiment, an expandable intervertebral fusion device can include a tapered edge to allow contoured insertion into the disc space. 
     In another embodiment, an intervertebral fusion device can be provided wherein the internal screw guides for screw insertion within the device are diagonal to each other within the xyz plane. 
     In another embodiment, an intervertebral fusion device wherein the internal screw guides can be adjacent and somewhat diagonal to each other within the xyz plane. 
     In another embodiment, an intervertebral fusion device can be provided wherein the majority each of the 2 screw holes can be in quadrant I and III or II and IV within the xyz plane. 
     In another embodiment, an intervertebral fusion device can be provided wherein the screw guides can have approximately the same xy coordinates and have different z coordinates or vice versa. 
     In another embodiment, an intervertebral fusion device can be provided wherein the center of the two internal screw guides could be in quadrants I and III or II and IV within the xyz plane. 
     In another embodiment, an intervertebral fusion device can be provided wherein one screw guide is in the top housing unit, and another screw guide is in the bottom housing unit. 
     In another embodiment, an intervertebral fusion device can be provided that uses a threaded rod (rotation screw) to engage a moveable component which engages a linkage to expand the device. 
     In another embodiment, an intervertebral fusion device can be provided that uses a threaded rod (rotation screw) to engage a wedge which engages its attaching linkages to expand the device. 
     In another embodiment, an expandable fusion device can be provided that can be adjusted using a threaded rod (rotation screw) coupled to a scissor-jack linkage. 
     In another embodiment, an expandable fusion device can be held together with fastener (s). These fasteners constrain the box to one degree of freedom. Part of the mechanism contains a mount for the rotation screw, which can control the movement of the pieces. As the screw is turned, it engages the teeth of the mechanism and acts as a wedge to rotate the pieces away from each other. 
     In another embodiment, an expandable fusion device adjusted by using a threaded rod (rotation screw) can be used as a wedge to offset the opposing cage surfaces. 
     In another embodiment, an expandable fusion device can be provided that uses a threaded rod (rotation screw) to expand the device using a metal driver as the wedge to mechanically separate the pieces. 
     In another embodiment, an expandable fusion device can be provided that can be adjusted by a threaded rod (rotation screw) coupled to a nut which translates to deform an elastomeric material used to force the expansion of the device. 
     In another embodiment, an expandable fusion device can be provided that has a threaded rod (rotation screw) that engages a wedge to control the expansion of the device. 
     In another embodiment, an expandable fusion device can be provided that can be contained by fasteners and retaining rings. 
     In another embodiment, an expandable fusion device can be provided that can be adjusted by a threaded rod (rotation screw) coupled to a wedge that can move the opposing cage surfaces. 
     In another embodiment, an expandable fusion device can be provided that uses a worm drive to turn a gear that acts as a wedge to expand the device. 
     In another embodiment, an expandable fusion device can be provided that includes fasteners and retaining rings containing and constraining the device pieces. 
     In another embodiment, an expandable fusion device can be provided that can be adjusted by a worm gear coupled to an internally threaded spur gear which, upon rotation, linearly advances a threaded component. 
     In another embodiment, a tool includes a handle, a gripper cooperating with the handle and having a plurality of prongs, a screw guide held in place the plurality of prongs, for controlling the direction of self-drilling screws that are screwed into the vertebral bodies, and an Allen key which expands expandable intervertebral devices. 
     The present invention has been described herein in terms of several preferred embodiments. However, modifications and additions to these embodiments will become apparent to those of ordinary skill in the art upon a reading of the foregoing description. It is intended that all such modifications and additions comprise a part of the present invention to the extent that they fall within the scope of the several claims appended hereto.