Patent Publication Number: US-2022211517-A1

Title: Devices and methods for spinal stabilization and instrumentation

Description:
PRIORITY 
     This application claims priority to U.S. Provisional Patent Application Ser. No. 61/795,658 filed Oct. 22, 2012 of the same title, and to U.S. Provisional Patent Application Ser. No. 61/795,703 filed Oct.  23 ,  2012  of the same title, each of which is incorporated herein by reference in its entirety. 
    
    
     COPYRIGHT 
     A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever. 
     BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure relates generally to skeletal technology. In one exemplary, aspect, apparatus and methods are disclosed that permit stabilization of the bony elements of the skeleton. These devices permit adjustment and maintenance of the spatial relationship(s) between neighboring bones. Depending on the specifics of the design, the motion between skeletal segments may be immobilized completely or preserved. 
     2. Description of Related Technology 
     Whether from degenerative disease, traumatic disruption, infection or neoplastic invasion, alterations of the normal anatomical relationships between the spinal vertebras can cause significant pain, deformity and disability. Spinal disease is a major health problem and procedures that surgically reconstruct the spinal column have become common procedures in the industrialized world. 
     Vertebral fusion may be accomplished by using an anterior, lateral or posterior approach and each has particular advantages and drawbacks. Frequently, circumferential fusion of the unstable level with fixation of both the anterior and posterior aspect of the spine is desired. This requires that patients undergo a combination of the aforementioned approaches. The anterior or lateral approaches are used to insert the bone graft into the disc space between the adjacent vertebras while the posterior approach is used to place bone screws or similar fasteners that are used to immobilize the vertebral bodies. 
     Hence, it would be desirable to provide an improved interbody device. 
     SUMMARY 
     The present disclosure addresses the foregoing needs by disclosing, inter alia, apparatus and methods for providing spinal percutaneous delivery of an implant that can rigidly fixate the spinous process of a first superior bone and a second inferior bone of a functional spinal unit. 
     In a first aspect, a method for placement of at least two orthopedic implants into a target disc space of a subject is disclosed. In one embodiment, the method includes approaching a target disc space, said target disc space being bordered by a first and second bone segments; accessing said target disc space on a first side and creating a first entry point therein; accessing said target disc space on a second side and creating a second entry point therein; advancing a first implant placement instrument into said target disc space through said first entry point, said first implant placement instrument being coupled to a first implant; advancing a second implant placement instrument into said target disc space through said second entry point, said second implant placement instrument being coupled to a second implant; affixing said first implant placement instrument to said second implant placement instrument such that a region of interconnection between said first and second implant placement instruments is positioned outside of said target disc space; and actuating at least one of said first and second implant placement instruments to displace a first one of said at least two implants away from a second one of said at least two implants, said displacement causing at least one of said at least two implants to be positioned onto a region of said target disc space. 
     In another embodiment, the method includes: (i) approaching a posterior aspect of the target disc space, the target disc space being bordered by a superior and an inferior bone segment, (ii) accessing the posterior aspect of the target disc space lateral to a thecal sac structure on an ipsilateral side and creating an entry point therein, (iii) accessing the posterior aspect of the target disc space lateral to a thecal sac structure on a contra-lateral side and creating an entry point therein, (iv) advancing a first implant placement instrument into the target disc space through the ipsilateral entry point, the first implant placement instrument being coupled to a first implant, (v) advancing a second implant placement instrument into the target disc space through the contralateral entry point, the second implant placement instrument being coupled to a second implant, (vi) rigidly affixing the first implant placement instrument to the second implant placement instrument, such that a region of interconnection between the first and second implant placement instruments is positioned outside of the target disc space, and (vii) actuating at least one of the first and second implant placement instruments to displace a first one of the at least two implants away from a second one of the at least two implants, the displacement causing at least one of the at least two implants to be positioned onto a lateral aspect of an epiphyseal ring of the target disc space. 
     In a second aspect of the invention, an orthopedic implant is disclosed. In one embodiment the device comprises two bone abutment members connected via an interconnecting member. 
     In a third aspect of the invention, a placement instrument configured to deliver the implant within the target disc space. In one embodiment, the instrument comprises an implant delivery segment, an anchor segment, and an articulating arm. 
     In a fourth aspect of the invention, a system for spinal stabilization is disclosed. In one embodiment, the system comprises at least two spinal implant apparatus configured to be placed within a target disc space via an implantation apparatus. 
     In a fifth aspect of the invention, a method for the minimally invasive placement of an orthopedic implant within a target inter-vertebral disc space is disclosed. In one embodiment, a first implant is placed into the posterior ipsilateral side of the disc space and a second implant is placed into the posterior contra-lateral side of the same disc space. The insertion instruments for both implants are, in one variant, rigidly anchored to each other, to the vertebral bone, and/or to the operating table onto which the subject is positioned. After instrument stabilization, each of the first and second implants are driven further into the disc space and away from one another, such that at least one of the implants comes to rest onto a segment of the lateral aspect of the epiphyseal ring of the target disc space. The disclosed implants include devices that transition from a first total length and a first total width before insertion into the target disc space to a second lesser total length and a second greater total width after device implantation. 
     The details of one or more embodiments are set forth in the accompanying drawings and description below. Other features, objects, and advantages will be apparent from the following description, the accompanying drawings and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is multiple views of an exemplary spinal vertebral bone. 
         FIG. 2A  is a view of an exemplary functional spinal unit (FSU), which includes two adjacent vertebrae and the intervertebral disc between them illustrating a posterior surface of the adjacent vertebrae and the articulations between them. 
         FIG. 2B  is an oblique view of the exemplary FSU of  FIG. 2A . 
         FIG. 3  is a superior view of an exemplary spinal vertebral bone illustrating the epiphyseal ring on the superior and the inferior surfaces thereof. 
         FIG. 4A  is a side view of three exemplary vertebral bones having relatively normal alignment. 
         FIG. 4B  is a side view of three exemplary vertebral bones having anterior displacement of the middle bone relative to the inferior-most bone. 
         FIG. 5  is a schematic diagram illustrating an exemplary interbody implant positioned within the disc space between the superior and inferior vertebral bodies of the immobilized FSU. 
         FIG. 6A  is a side perspective view of the exemplary interbody implant of  FIG. 5 . 
         FIG. 6B  is a cross-sectional view of the exemplary interbody implant of  FIG. 5 . 
         FIG. 7A  is a schematic representation of an exemplary resection at the L 415  disc space 
         FIG. 7B  is a schematic representation of the exemplary resection of  FIG. 7A  exposing the posterior aspect of the thecal sac. 
         FIG. 8A  is a superior view of an exemplary defect in the posterior Annulus Fibrosis of the target disc space through which an exemplary implant is advanced. 
         FIG. 8B  is a superior view of the exemplary implant placed within the target disc space of  FIG. 8A . 
         FIG. 9A  is a superior view of the exemplary implant having been displaced laterally in the disc space and then detached from placement instrument. 
         FIG. 9B  is a superior view of a bone forming material place into the decorticated area of the disc space. 
         FIG. 9C  is a side perspective view of an exemplary articulating retention arm. 
         FIGS. 10A and 10B  are superior views of an exemplary implant advanced from a posterior to anterior direction by a placement instrument. 
         FIG. 11A  is a superior view of an exemplary connecting member configured to connect an exemplary placement instrument to an exemplary contralateral instrument. 
         FIG. 11B  is a superior view of exemplary implants in a non-expandable configuration after lateral displacement. 
         FIG. 12A  is a superior view of exemplary implants in an expanded configuration after lateral placement. 
         FIG. 12B  is a superior view of exemplary implants after placement of a bone forming material on at least one side of the vertebral midline. 
         FIG. 13A  is a sagital view of an exemplary implant being used to align the implanted FSU segment. 
         FIG. 13B  is a coronal plane section of the vertebral bones that surround an implanted disc space. 
         FIG. 14  is multiple views of an exemplary assembled implant according to the present disclosure. 
         FIG. 15  is an exploded view of the exemplary assembled implant of  FIG. 14 . 
         FIG. 16  is multiple views of a first member of the exemplary assembled implant according to the present disclosure. 
         FIG. 17  is multiple views of a second member of the exemplary assembled implant according to the present disclosure. 
         FIG. 18  is multiple views of a linkage member of the exemplary assembled implant according to the present disclosure. 
         FIG. 19  is multiple views of transitioning of the exemplary implant from an open configuration to a closed configuration. 
         FIG. 20A  is a side perspective view of the exemplary implant in a closed configuration. 
         FIG. 20B  is a sectional view of the exemplary implant in a closed configuration. 
         FIG. 21  is multiple views of a contralateral side of an exemplary implant according to the present disclosure. 
         FIG. 22  is multiple views of another exemplary embodiment of an implant according to the present disclosure. 
         FIG. 23  is multiple exploded perspective views of the exemplary embodiment of the implant of  FIG. 22 . 
         FIG. 24A  is multiple views of a member of the exemplary embodiment of the implant of  FIG. 22 . 
         FIG. 24B  is a superior view of utilization of a placement instrument to implant the exemplary implant of  FIG. 22  within the target disc space. 
         FIG. 24C  is a superior view of the medial displacement of the exemplary implant of  FIG. 22  within the target disc space. 
         FIGS. 24D and 24E  are prospective views of the exemplary implant of  FIG. 22  implanted within the target disc space and having the bone forming material disposed therein. 
         FIG. 25  is multiple views of another exemplary embodiment of an implant according to the present disclosure shown in an open configuration. 
         FIG. 26  is an exploded a view of the exemplary implant of  FIG. 25 . 
         FIG. 27  is multiple views of a first member of the exemplary implant of  FIG. 25 . 
         FIG. 28  is multiple views of a second member of the exemplary implant of  FIG. 25 . 
         FIG. 29  is multiple views of a third member of the exemplary implant of  FIG. 25 . 
         FIG. 30  is multiple views of transitioning of the exemplary implant from an open configuration to a closed configuration. 
         FIG. 31  is a partially exploded view illustrating the positioning of a first member of the exemplary implant. 
         FIG. 32  is multiple views of utilization of a placement instrument to place the members of the exemplary implant. 
         FIG. 33  is a partially exploded view illustrating the positioning of a second member of the exemplary implant. 
         FIG. 34A  is a side and oblique view of another exemplary embodiment of an implant according to the present invention. 
         FIG. 34B  is a side view illustrating movement of one or more segments of the exemplary implant of  FIG. 34A . 
         FIG. 34C  is a superior view of the exemplary implant of  FIG. 34A  within an exemplary vertebral bone. 
         FIG. 35A  is multiple views of an exemplary expandable implant adapted to expand after implantation into the target disc space. 
         FIG. 35B  is an expanded view of the exemplary implant of  FIG. 35A . 
         FIG. 36A  is a superior view of an exemplary implant being introduced into a target disc space. 
         FIG. 36B  is a superior view of the exemplary implant displaced laterally within the target disc space. 
         FIG. 37  is a superior view of two bilaterally positioned implants according to one embodiment of the present disclosure. 
         FIG. 3   8 A is a superior view of advancement of two exemplary first implants into the target disc space. 
         FIG. 38B  is a superior view of rotation of the exemplary implants of  FIG. 38A  laterally within the target disc space. 
         FIG. 39A  is a superior view of advancement of two exemplary second implants into the target disc space. 
         FIG. 39B  is a superior view of a lateral translation of the two exemplary second implants of  FIG. 39A  within the target disc space. 
         FIG. 40A  is a superior view of the two first and the two second exemplary implants prior to a rotation thereof. 
         FIG. 40B  is a superior view of the two first and the two second exemplary implants of  FIG. 40A  after rotation thereof. 
         FIG. 41  is multiple views of an exemplary spinous process fixation implant. 
         FIG. 42A  is a lateral view of an implanted FSU with the exemplary implant of  FIG. 41 . 
         FIG. 42B  is an axial view of an implanted FSU with the exemplary implant of  FIG. 41 . 
         FIG. 43  is a logical flow diagram of a method for implantation of an implant according to the present invention. 
     
    
    
     All FIGS. © Copyright 2013. Samy Abdou. All rights reserved. 
     Overview 
     In one aspect, improved apparatus and methods for spinal stabilization are disclosed. In one exemplary implementation, the improved is advantageously used as part of minimally invasive procedures- including percutaneous operations. Additionally, the improved interbody device and its method of implantation may be employed in any applicable interbody fusion procedure and used at any spinal segment. Still further, the exemplary embodiments of the improved interbody device are configured to provide a safe and reproducible method for performing a minimally invasive posterior vertebral fusion. 
     DETAILED DESCRIPTION 
     In order to promote an understanding of the principals of the disclosure, reference is made to the drawings and the embodiments illustrated therein. Nevertheless, it will be understood that the drawings are illustrative and no limitation of the scope of the disclosure is thereby intended. Any such alterations and further modifications in the illustrated embodiments, and any such further applications of the principles of the disclosure as illustrated herein are contemplated as would normally occur to one of ordinary skill in the art. 
       FIG. 1  shows a diagrammatic representation of a spinal vertebral bone  802  in multiple views. For clarity of illustration, the vertebral bone of  FIG. 1  and those of other illustrations presented in this application are represented schematically and those skilled in the art will appreciate that actual vertebral bodies may include anatomical details that are not shown in these figures. Further, it is understood that the vertebral bones at a given level of the spinal column of a human or animal subject will contain anatomical features that may not be present at other levels of the same spinal column. The illustrated vertebral bones are intended to generically represent vertebral bones at any spinal level without limitation. Thus, the disclosed devices and methods may be applied at any applicable spinal level. 
     Vertebral bone  802  contains an anteriorly-placed vertebral body  804 , a centrally placed spinal canal and  806  and posteriorly-placed lamina  808 . The pedicle ( 810 ) segments of vertebral bone  802  form the lateral aspect of the spinal canal and connect the laminas  808  to the vertebral body  804 . The spinal canal contains neural structures such as the spinal cord and/or nerves. A midline protrusion termed the spinous process (SP) extends posteriorly from the medial aspect of laminas  808 . A protrusion extends laterally from each side of the posterior aspect of the vertebral bone and is termed the transverse process (TP). A right transverse process (RTP) extends to the right and a left transverse process (LTP) extends to the left. A superior protrusion extends superiorly above the lamina on each side of the vertebral midline and is termed the superior articulating process (SAP). An inferior protrusion extends inferiorly below the lamina on each side of the vertebral midline and is termed the inferior articulating process (IAP). Note that the posterior aspect of the pedicle can be accessed at an indentation  811  in the vertebral bone between the lateral aspect of the SAP and the medial aspect of the transverse process (TP). In surgery, it is common practice to anchor a bone fastener into the pedicle portion of a vertebral bone by inserting the fastener through indentation  811  and into the underlying pedicle. 
       FIGS. 2A and 2B  illustrate a functional spinal unit (FSU), which includes two adjacent vertebrae and the intervertebral disc between them. The intervertebral disc resides between the inferior surface of the upper vertebral body and the superior surface of the lower vertebral body. (Note that a space is shown in  FIGS. 2A and 2B  where intervertebral disc would reside.)  FIG. 2A  shows the posterior surface of the adjacent vertebrae and the articulations between them while  FIG. 2B  shows an oblique view. Note that FSU contains a three joint complex between the two vertebral bones, with the intervertebral disc comprising the anterior joint. The posterior joints include a facet joint  814  on each side of the midline, wherein the facet joint contains the articulation between the IAP of the superior vertebral bone and the SAP of the inferior bone. 
     The preceding illustrations and definitions of anatomical structures are known to those of ordinary skill in the art. They are described in more detail in Atlas of Human Anatomy, by Frank Netter, third edition, Icon Learning Systems, Teterboro, New Jersey, the text of which is herein incorporated by reference in its entirety. 
     The epiphyseal ring is the outer rim segment that is located on each of the superior and the inferior surfaces of a vertebral bone- as shown in  FIG. 3 . (Note that the superior and inferior surfaces of the vertebral bone are those surfaces that abut the intervertebral discs.) The epiphyseal ring is circumferentially positioned and forms the most dense and strongest portion of the superior and inferior surfaces of the vertebral bone. The ring is comprised of dense bone that anchors the external fibers of the annulus fibrosis of the adjacent intervertebral disc. (The epiphyseal ring is discussed in detail in: The epiphyseal ring: a long forgotten anatomical structure with significant physiological function. Dar G, et al. Spine (Phila Pa. 1976). 2011 May 15;36(11):850-6, which is herein incorporated by reference in its entirety.) 
     In a healthy spine that is functioning within physiological parameters, the two facet joints of an FSU (Functional Spinal Unit) collectively function to prevent aberrant relative movement of the vertebral bones in the horizontal (i.e., axial) plane. (The horizontal plane of a human spine refers to a plane of the erect spine that is substantially parallel to a level floor on which the subject is standing). With aging and spinal degeneration, displacement of the vertebral bones in the horizontal plane may occur and the condition is termed spondylolisthesis.  FIG. 4A  illustrates three vertebral bones with relatively normal alignment, whereas  FIG. 4B  shows the anterior displacement of the middle bone relative to the inferior-most bone. In the illustration, the vertebral column of  FIG. 4B  is said to have an anterior spondylolisthesis of the middle vertebral bone relative to the inferior-most vertebral bone. 
     A spondylolisthesis can be anterior, as shown in  FIG. 4B , or posterior wherein a superior vertebral bone of a functional spinal unit is posteriorly displaced in the horizontal plane relative to the inferior vertebral bone. In general, anterior sponylolisthesis is more common and more clinically relevant than posterior sponylolisthesis. (Sponylolisthesis can be further classified based on the extent of vertebral displacement. See Principles and practice of spine surgery by Vaccaro, Bets, Zeidman; Mosby press, Philadelphia, Pa.; 2003. The text is incorporated by reference in its entirety.) 
     With degeneration of the spine, constriction of the spinal canal and impingement of the contained nerve elements frequently occurs and is termed spinal stenosis. Spondylolisthesis exacerbates the extent of nerve compression within the spinal canal since misalignment of bone within the horizontal plane will further reduce the size of the spinal canal. Relief of the compressed nerves can be achieved by the surgical removal of the bone and ligamentous structures that constrict the spinal canal. However, decompression of the spinal canal can further weaken the facet joints and increase the possibility of additional aberrant vertebral movement. That is, spinal decompression may worsen the extent of spondylolisthesis or produce spondylolisthesis in an otherwise normally aligned FSU. After decompression, surgeons will commonly fuse and immobilize the adjacent spinal bones in order to prevent the development of post-operative vertebral misalignment and spondylolisthesis. 
     Regardless of the clinical reason or indication for fusion of the vertebral bones, many surgeons position an implant within the disc space that rests between the two vertebral bones to be fused. An example of a generic interbody implant is shown positioned within the disc space between the superior and inferior vertebral bodies of the immobilized FSU in  FIG. 5 , wherein a side view of an FSU is shown. Many embodiments of interbody implants are known in the art, and U.S. Pat. Nos. 4,636,217; 5,015,247; 5,192,327; 5,443514; 5,749,916, 6,251,140; 6,342,074; 6,706,070; 6,767,367; 6,770,096; 6,852,127; 7,037,339; 7,227,477; 7,641,690, among others, disclose some of these inter-body implant device. (Each of the listed patents is herein incorporated by reference in its entirety). In general, and as shown in the example of  FIGS. 6 , a generic interbody implant is usually comprised of an outer superstructure  925  that is a manufactured of a synthetic biocompatible material (such as metal alloy, plastic material, ceramics, and the like) and an internal cavity  922  this is configured to house a bone forming material. Open bores  927  permit communication and fusion between the vertebral bone(s) outside of the device and the bone forming material contained within cavity  922 . In general, the superstructure separates and supports the vertebral bones that abut the implanted disc space. In this way, the device can be used to maintain the disc space height. The internal cavity contains the bone formation material that will form the actual fusion mass that will eventually extend from the superior to the inferior vertebral bones. When the superstructure  925  is manufactured from metallic alloy, it can be advantageously made of limited thickness thereby providing a larger internal cavity  922  for containment of a larger volume of bone fonning material. However, the metallic superstructure is generally X-ray opaque and thus limits the ability to follow bone healing in the post-operative period. In contrast, manufacture of superstructure  925  from plastic materials (such as PEEK) or ceramics permits good X-ray visualization of the healing bone within but significantly limits the size of internal cavity  922  and the volume of bone forming material contained therein. 
     Considerable clinical experience has been gained in the implantation of these interbody implants via a posterior surgical corridor and the limitations and disadvantages of this general design are becoming known. In a fist limitation, these implants are generally large, have a width of at least  10 mm, and requiring substantial bony resection of the posterior spinal elements for device implantation. Implantation of these devices through a posterior surgical approach often involves removal of substantial portions of the facet joint at the implanted level. (It should be noted disc space fusion via a posterior approach without significant facet resection is termed a posterior lumbar interbody fusion (PLIF), whereas extensive facet joint resection and use of a slightly more lateral corridor is termed a trans-foraminal lumbar interbody fusion (TLIF)). Facet joint resection adds to the surgical work. It also significantly destabilizes the implanted FSU so that pedicle screw fixation is needed to re-stabilize the operative level. That is, the implantation of the interbody device may require enough bony resection so as to require large supplemental fixation devices and obviate the use of minimally invasive fixation device—such as spinous process fixators. Given the proximity to nerve elements to the posterior surgical corridor, implant placement with limited facet resection requires a greater degree of nerve retraction and increases the risk of nerve injury. Finally, prior attempts to reduce the width of the interbody implant have produces implants with height to width ratio that is greater than one, and have increased the risk of implant roll-over within the disc space. 
     While the overall implant diameter must be kept at a minimum because of the limited implantation corridor, containment of the bone graft material with an internal cavity of the implant provides a second limitation—since the volume of bone graft material contained within the implant is necessarily small, Attempts to maximize the graft cavity size by decreasing implant wall thickness will require that the implant be manufactured from metallic alloys. As already noted, metallic alloys are radio-opaque and will prevent adequate X-ray evaluation of bone healing in the post-operative period. 
     In a third limitation, the totality of the section of the disc space on which the implant will rest must be prepared by removal of the cartilaginous end plate and decortication of the vertebral bone surfaces that abut (i.e., upper and lower vertebrae) the implant. This is performed so that the bone graft material contained within the implant will fuse with the adjacent vertebral bones, The area of end plate decortication has width of at least D 1  ( FIG. 6A ), which is total width of the implant, instead of limiting decortication to the width D 2 . Unfortunately, decortication of the bony segment upon which the superstructure  925  rests will thin the cortical bone and disadvantageously predispose to implant subsidence within the vertebral bones. This is especially problematic, since subsidence reduces disc space height and threatens to re-trap the adjacent nerve elements—which would obviate the very purpose of the operative procedure. Finally, the decortication process is laborious and adds to the time required to complete the procedure. 
     It is a purpose of the present disclosure to disclose an improved interbody device. The device is particularly advantageous for use in minimally invasive procedures—including percutaneous operations. However, the device and its method of implantation may be employed in any applicable interbody fusion procedure and used at any spinal segment. 
     It is a purpose of the present disclosure to separate the region of the device that provides vertebral support (such as, for example, the superstructure) from that region of the device that houses the material needed to form the fusion mass. The two regions may be implanted separately into the disc space and simply positioned adjacent to one another without mutual attachment. Alternatively, the two separate regions may be attached to one another. Separation of the two segments allows the vertebral support segment to be manufactured form metallic alloys, if desired, without obscuring post-operative X-ray follow-up of bone healing. In a one embodiment, the width of the implant is less than  8 mm at the time of its advancement through the spinal canal (i.e., at the time of insertion past the nerve elements). However other widths may be utilized with equal success. 
     It is a purpose of the present disclosure to provide a method for the safe and reproducible placement of an interbody device into an intervertebral disc space. In a first embodiment, the interbody device is employed without other bone fixation implants (i.e., as a “stand alone” device). In a second embodiment, the interbody device is employed in conjunction with a spinous process fixation implant. In a third embodiment, the interbody device is used with pedicle screw fixation of the vertebral bones. That is, a pedicle screw is placed into an ipsilateral pedicle of each of the superior and inferior vertebral bones that abut the implanted disc space. The bone screws are joined by an interconnecting member, such as a rod, and the assembly is used to rigidly fixate the vertebral bones to one another. (It is understood that either the interbody device or the pedicle screw/rod assembly may be used on one side of the vertebral midline alone (unilateral) or on both sides of the vertebral midline (bilateral). The vertebral midline is substantially defined by the mid-sagittal plane that bisects the implanted disc space/vertebral bones into a right half and a left half). In other embodiments, the interbody device may be used with additional bone fixation implant. 
     In one embodiment of a method for device placement, the disc space that is targeted for inter-body device implantation is identified using radiographic imagining techniques (such as X-rays, CT, MRI and the like). A skin incision is made in the skin immediately posterior to the target disc space. The paraspinal muscles are retracted and a corridor is developed adjacent to the spinous process and the posterior aspect of the lamina. The lamina of each of the superior and inferior vertebrae that border the targeted disc space are identified. In one particular embodiment, this may be accomplished via an imaging modality. Resection of the lamina posterior to the target disc space is performed, wherein at least a portion of the inferior aspect of the lamina of the superior vertebral bone (i.e., the vertebral bone that forms the superior border of the target disc space) is removed. This is schematically shown as resection of segment  1152  ( FIG. 7A ) when targeting the L4/5 disc space. 
     An additional resection of the lamina posterior to the target disc is performed, wherein at least a portion of the superior aspect of the lamina of the inferior vertebral bone (i.e., the vertebral bone that forms the inferior border of the target disc space) is removed. This is schematically shown as resection of segment  1153  ( FIG. 7A ) when targeting the L4/5 disc space. At least a portion of the ligament (i.e., the ligamentum flavum) that spans the region of lamina resection is also removed. In this way the posterior aspect of the thecal sac is exposed through window “W” of  FIG. 7B . While shown as being performed on only one side of the midline, it is understood that window W may be placed bilaterally. (In one particular embodiment, Window W is located on either side of the vertebral midline, wherein the vertebral midline is defined by a sagittal plane that substantially extends through the spinous process and divides a vertebral bone into a left and a right half.) 
     The posterior aspect of the target disc space is exposed through a corridor that is lateral to the nerve elements (and thecal sac), wherein the lateral aspect of the corridor is substantially at or lateral to the medial border to the pedicles. This is best appreciated by the operating surgeon by exposing the medical aspect of the pedicle of the inferior vertebral bone (i.e., the vertebral bone that forms the inferior border of the target disc space). Plane A is positioned substantially at the medial border of the pedicle  810  and is schematically shown in  FIG. 3 . 
     The nerve elements are retracted gently in the medial direction and the posterior aspect of the target disc space is identified. The disc space is entered and at least a segment of the disc material may be removed (termed discectomy). 
       FIG. 8A  illustrates the defect  1170  in the posterior Annulus Fibrosis of the target disc space through which implant  105  is being advanced into the target disc space ( FIG. 8B ). In one particular embodiment, the medial to lateral dimension of the posterior entry window into the disc space is less than  8 . 1 mm. The implant  105  is attached to an implant placement instrument  205 . In another particular embodiment, the medial to lateral dimension of implant  105  as it enters the posterior aspect of the target disc space is less than  6 . 1 mm. The implant placement instrument may attach onto an outer surface of the implant (such as, for example, a posterior surface thereof). While not illustrated, the implant is alternatively (or additionally) advanced into the disc space through a port that forms a corridor to deliver the implant into the target disc space. That is, the implant placement instrument may comprise an internal channel through which the implant is advanced into the target disc space. Regardless of placement instrument design and configuration, the implant may be advanced into the posterior aspect of the target disc space using a posterior to anterior trajectory that is substantially parallel to the mid-sagittal plane (see  FIGS. 8A  and B). 
     A collapsed disc space having a small vertical height is distracted back to a desired height of greater value by the sequential/iterative placement of shims or distractors within the disc space. Alternatively, or in addition, the implant placement instrument may also serve as a distractor of the disc space. For example, the placement instrument may have a segment that is sized to be positioned within the disc space. The intra-discal segment is comprised of an upper and lower surface, such that the upper surface may be forcibly distracted away from the lower surface. In this way, the vertebral bone superior to the target disc space can be forcibly moved away from its immediately inferior vertebral bone and thereby increase the superior to inferior height of the target disc space. (Note that a collapsed disc space has a disc space height that is substantially below the normal value for that disc space level, wherein the disc space height is the vertical distance from the superior disc space surface to the inferior disc space surface.) 
     As shown in  FIG. 813 , implant  105  is placed with its lateral surface substantially at or medial to plane A (Figured  8 B), wherein plane A is a sagittal plane substantially at the medial aspect of the pedicle of the inferior vertebral bone. Implant  105  is then translated laterally within the disc space so that it rests at least partially on the lateral aspect of the epiphyseal ring. In another embodiment, the lateral aspect of the implant rests at the lateral border of the disc space (at the approximate level of the lateral wall of each of the superior and inferior vertebral bones—see  FIG. 9A ), Prior to the lateral displacement of implant  105  with in the target disc space, in one embodiment, at least a portion the placement instrument and/or implant delivery port are anchored to the vertebral bone and/or onto the operating room table. This is done in order to counter the opposing force that would be felt by the placement instrument—as a reaction to the laterally-directed force applied to implant  105 . Without anchoring or securing the placement instrument, the surgeon&#39;s ability to move the implant laterally within the disc space is limited. Further, the un-anchored placement instrument will necessarily be displaced medially in reaction to a force that displaces the implant laterally. Since the nerves are immediately medial to the placement instrument, medial movement of the placement instrument will impinge the nerve elements and can produce nerve injury. 
     The placement instrument and/or implant delivery port are anchored into the posterior bony surface of the inferior vertebral body and/or the superior vertebral body in one embodiment. They may be anchored into the pedicle of the inferior vertebral bone and/or directly into any other part of vertebral bones that are adjacent to (or abut) the target disc pace. They may be also anchored directly to a first segment of an articulating retention arm wherein a second segment of the arm is rigidly attached to the operating room table upon which the patient is positioned. (An example of an articulating retention arm is show in  FIG. 9C .) When the procedure is performed bilaterally (see  FIGS. 10-12 ), the placement instrument and/or implant delivery port may be also (or alternatively) anchored rigidly and directly to one another as will be discussed below. The relative advantages of this method of anchoring the placement instrumentation will also be disclosed below. 
     Frame devices that anchor surgical instruments to the operating table are known in the art. In the illustrated device ( FIG. 9C ), articulated frame  905  has member  9052  that reversibly attaches to the operating table onto which the patient is positioned. Member  9056  is adapted to reversibly and rigidly clamp onto a segment of the placement instrument  208 . Member  9054  is adapted to reversibly transition the frame  905  from the first state (movably articulating frame segments) to the second state (articulated frame segments are rigidly locked to one another). While an example of an articulated frame  905  is illustrated, it is understood that any other applicable such device may be alternatively used. (For example, U.S. Pat. Nos. 4,254,763; 5,908,382; 6,302,843; 6,709,389; 7,156,806, and many others are known to disclose surgical retractor systems that anchor to the operating table. Each of the foregoing is herein incorporated by reference in its entirety). 
       FIG. 9A  illustrated implant  105  having been displaced laterally in the disc space and then detached from placement instrument  208 . The region of the disc space medial to the implant can then be prepared to accept a bone graft member. This is performed by the removal of at least a portion of the disc space as well as decortication (which is comprised of removal of the cartilaginous end plate from bone) of the inferior surface of the upper vertebral bone and the superior surface of the lower vertebral bone. Note that removal of the disc material may be performed through the area of the disc space that will become in contact with the implant. (For example, the disc material is removed from the medial limit of the area of implant entry into the disc space (plane B of  FIG. 9A ) to the lateral aspect of the disc space, where the implant will be ultimately positioned.) In contrast, the area of decortication (i.e., removal of the cartilaginous end plate) is generally limited to the area into which the bone graft material (such as bone graft  310 ) is placed. This provides the relative advantage of discectomy of the area of the target disc space in which the implant will abut the vertebral bone surface rather than decortication of the abutted bone surfaces. After decortication of the vertebral bone surface that is adjacent to the surface abutted by the implant, an allograft or autograft bone graft segment  310  and/or bone graft substitute (collectively termed bone forming material) is placed into the decorticated area of the disc space - as shown in  FIG. 9B . 
     In an alternative embodiment, the procedure may be performed bilaterally.  FIGS. 10A and 1013  show an implant  105  being advanced from a posterior to anterior direction by a placement instrument  208 . In one embodiment, the medial to lateral dimension of the posterior entry window into the disc space is less than 8.1 mm. In another embodiment, the medial to lateral dimension of the implant  105  as it enters the posterior aspect of the target disc space is less than 6.1 mm. A first implant  105  is advanced into the disc space through a corridor immediately lateral to the nerves/thecal sac but substantially medial to the plane demarcating a medial aspect of the inferior pedicle (such as, for example, plane A of  FIG. 8B ). All of the procedural steps disclosed above for the unilateral implant placement are performed. These steps are repeated with a second implant  105  using a comparable but contralateral corridor. (Note that contralateral implant placement indicated positioning the second implant across the vertebral midline from the first implant, wherein the midline is defined by a sagittal plane that divides the vertebral bone into a right and a left half—as shown in  FIG. 813 .) 
     While each implant is labeled as implant  105 , it is understood that the implants need not be identical. For example, the implants may be mirror images of one another or of completely different design, configurations or size. That is, it is contemplated that any implant that is sized and configured for intervertebral disc space implantation may be used on either side. By varying the configuration and size, for example, the implant may be used to impart a different height to the anterior disc space than the posterior disc space and thereby align the implanted FSU segment into a more or a less lordotic curvature ( FIG. 13A —in sagittal view). Further, the heights of implant  105  on either side of vertebral midline may be different so as to change the alignment of the implanted 
     FSU in the coronal plane of the spinal column—such as, for example, in the correction of scoliosis. The latter is illustrated in  FIG. 13B  and shows a coronal plane section of the vertebral bones that surround an implanted disc space. Note the coronal plane curvature created by the different sized implants  105 . Finally, it is understood that each of the two implants are placed into the disc space using a posterior (to anterior) corridor substantially medial to the medial aspect of the pedicle (such as plane A of  FIG. 8B ) but lateral to the thecal sac. That is, the thecal sac rests between each of the placement instruments  208 —as shown by “X” in  FIG. 10B . 
     In another embodiment, and as show in the axial plane view of  FIG. 12A , implant  105  of the first side is separated from the contralateral  105 . That is, implants  105  do not abut one another and are not coupled or connect to one another by one or more other members. Each of implant  105  is freely movable relative to the other implant  105  within the implanted disc space. That is, the application of a force to one implant  105  may not be felt or have any effect on the other/contralateral implant  105 . Any bone graft material that is implant between the opposing implants  105  would not necessarily interlock together the implants  105 . 
     Prior to lateral displacement of each implant  105 , the placement instrument  208  and/or implant delivery port are rigidly anchored relative to the disc space, so as to counter the medially-oriented force that will be felt by the placement instrumentation in reaction to the laterally-oriented force applied to the implant. The anchor is of critical importance, since a non-anchored placement instrument will be displaced medially itself instead of being able to displace the implant laterally. The placement instrument  208  and/or implant delivery port may be anchored (such as with a bone anchor) into the posterior bony surface of the inferior vertebral body and/or the superior vertebral body. They may be also anchored into the pedicle of the inferior/superior vertebral bones. They may be also anchored onto any posterior surface of the vertebral bones such as, for example, the spinous processes or lamina. 
     The placement instruments may be also anchored directly within the disc space to be implanted (such as, for example, using a wedge/shim). They may be also anchored directly to a first segment of an articulating retention arm wherein a second segment of the arm is rigidly attached to the operating room table upon which the patient is positioned. (An example of an articulating retention arm is shown in  FIG. 9 c    and will be discussed further below.) 
     In bilateral implant placement, a placement instrument  218  can be also rigidly connected to the contralateral instrument  218 , such as, for example, using connecting member  225  of  FIG. 11A . In this configuration, the medially-directed force generated by the lateral displacement of an implant (see arrows of  FIG. 11A ) is substantially offset by an opposing force of similar magnitude that is generated by lateral displacement of the contralateral implant. (The use of a connecting member between placement instruments will be discussed further below.) It is further contemplated that the placement instrument may be placed into the disc space on either side of the midline and then interconnected—as shown in  FIGS. 10-12 . Alternatively, the placement instruments may be interconnected to one another prior to advancement into the disc space. The interconnection may be rigid at the time of introduction of placement instruments into the disc space, or it may be an adjustable/malleable interconnection that is subsequently made rigid after advancement of the placement instruments into the disc space but prior to the deployment of the implants. In this embodiment, the interconnecting member must necessarily cross the plane of the vertebral midline. 
     Note that any of the aforementioned anchoring regions/methods are not mutually exclusive and more than one of them may be concurrently used to rigidly anchor the placement instrument and/or implant delivery port relative to the FSU to be implanted. 
       FIG. 11B  shows the implants after lateral displacement. At least one (and in one embodiment both) of the bilaterally-placed implants is positioned with at least a portion of the implant abutting the lateral aspect of the epiphyseal ring. That is, at least a portion of at least one of the implants rests on the lateral aspect of the epiphyseal ring. The implant may be of a non-expandable configuration, as shown in  FIG. 11B , or it may expand and transition to a greater width within the disc space, as shown in  FIG. 12A . While not shown in these axial views, it further contemplated that the implant may transition to a different height. (Implant height is defined as substantially being the greatest implant measure from the inferior surface of the superior bone to the upper abutment surface of the inferior bone).  FIG. 12B  illustrates the construct after placement of bone forming material  310  on at least one side of the vertebral midline. The procedure needed for graft placement was disclosed above. 
     Alternative implant embodiments will now be described. Since it is contemplated that any implant that is sized and configured for intervertebral disc space implantation may be used, the following embodiments are provided as examples and are not intended to be limiting in any way. 
     In an embodiment, an implant  301  has diameter “D” which is equal to or less than 8 mm, and has a height “H” that is equal to or greater than 8 mm. Implant  301  is comprised of a first member  307  and a second member  309  that are linearly aligned. Members  307  and  309  may be movably interconnected by member  701 , as shown, or may be unattached to one another (that is, member  307  and  309  may be simply arranged to follow one another into the disc space but to be otherwise not interconnected). Members  307  and  309  may be of the same or different heights H (as measured from a lower implant surface abutting the upper surface of the lower vertebral body to an upper implant surface abutting the lower surface of the upper vertebral body). When implants  307  and  309  are different in heights, it is preferred (however, not necessary) that implant  309  be of greater height.  FIG. 14  shows views of the assembled implant  301  whereas  FIG. 15  shows an exploded view. 
     In an embodiment, members  307  and  309  may be of the same or different widths D (the width is the measure of the side to side distance, such as, for example, width D of  FIG. 14 ), The members are linearly aligned in one embodiment such that the greatest width across the implant  301  is no greater than width of the implant  307  and/or  309  that is of greater width. As implant is advanced past the nerve elements and into the disc space, members  307  and  309  are aligned in tandem, as shown in  FIG. 14 , with a front end of member  309  abutting a back end of member  307 . In order to minimize the implant width as it passes through the spinal canal (and the nerves contained therein), the side surfaces of member  307  and  309  do not overlap in the expanded configuration shown in  FIG. 14 . Once into the disc space, members  307  and  309  are repositioned to rest next to one another, as shown in  FIGS. 20 . That is, in the expanded configuration, the length L of implant  301  is substantially equal to the sum of length L 1  of member  307  and length L 2  of member  309  ( FIG. 14 ). 
     In an embodiment, at least one of member  307  and/or  309  will contain a cavity that is at least partially contained within its internal aspect and configured to house a bone forming material that can fuse with at least one adjacent vertebral bone. In another embodiment, neither implant contains bone graft material within it. In another embodiment, at least one of members  307  and /or  309  has greater height than the implanted disc space, so that at implantation, the member is recessed within a bony defect that is cut within the superior and/or inferior vertebral bone. In another embodiment, neither member  307  nor  309  is recessed within a cavity cut into the adjacent vertebral bone, but each of the members rests on the intact endplate of the vertebral bones. 
       FIG. 16  shows multiple views of member  307 . There is a superior surface  3072  and inferior surface  3071 , which contain protrusions or are otherwise textured to increase fixation into the adjacent bone in one embodiment. Member  307  contains a front end  3075 , a back end  3076  and side walls  3078 . Channel  3073  extends from superior surface  3072  to inferior surface  3071 . Side channel  3074  extends from a first side wall  3078  to channel  3073 , but does not extend to opposing wall  3078 . Channels  3073  and  3074  are configured to accept member  701 . Back end  3076  contains curved segments  3   0762  that allow member  309  to rotate from a posterior to a side position relative to member  307 —as will be discussed below. Bore  3079  accepts a radio-opaque marker so that the implant&#39;s position may be identified by X-ray imaging after implantation into a subject. The terms superior, inferior, cephalad, caudad, top, bottom, front, back, side and the like are used to facilitate description of this and other the members/devices in this application. The usage is not intended to be limiting in any way. 
       FIG. 17  shows multiple views of member  309 . There is a superior surface  3092  and inferior surface  3091 , which may contain protrusions or be otherwise textured to increase fixation into the adjacent bone. Member  309  contains a front end  3095 , a back end  3096  and side walls  3098 . Channel  3093  extends from superior surface  3092  to inferior surface  3091 . Side channel  3094  extends from a first side wall  3098  to channel  3093 , but does not extend to opposing wall  3098 . Channels  3093  and  3094  are configured to accept member  701 . Front end  3095  contains curved segments  30952  that allow member  309  to rotate from a posterior to a side position relative to member  307  - as will be discussed below. An additional channel  310  is positioned on a side wall  3098  and configured to receive a complimentary protrusion from the implant placement instrument. Channel  310  extends posteriorly and opens onto back end  3096 . 
       FIG. 18  illustrates member  701 . Member  701  is a linkage that movably couples member  307  and member  309 . Each of the two end segments  7012  and  7014  are substantially cylindrical. The ends segments are connected by segment  7016 . One of segments  7012  and  7014  is positioned within channel  3073  of member  307 , whereas the other of segments  7012  and  7014  is positioned within channel  3093  of member  309 . Segment  7016  is contained within channel  3074  of member  307  and within channel  3094  of member  309 . While member  701  is illustrated as a single/unitary device, it may be alternatively made of separate components that are attached to one another.  FIG. 19  illustrates the transition of implant  301  from a first configuration (open) to a second configuration (closed). Application of a Force along direction A ( FIG. 19 ) while holding stationary the front end  3075  of member  307  will transition the implant from the first to the second configuration. In the first configuration, member  307  and member  309  are linearly positioned with member  307  ahead of member  309 , so that front end  3095  abuts back end  3076  and side surface  3078  does not abut side surface  3098 . This minimizes the overall width on implant  301 . In the second configuration, members  307  and  309  are positioned side by side, wherein a side surface  3078  abuts a side surface  3098 .  FIG. 20A  shows implant  301 in the second configuration, whereas  FIG. 20B  shows a sectional view of the implant  301  in the second configuration. While not shown, it is further contemplated that a locking feature may be added to retain implant  301  in the second configuration. That is, a locking feature may be added to immobilize members  307  and  309  relative to one another, once the second configuration has been reached. 
     After member  309  is advanced from a posterior position that is outside the disc space to anterior position within the disc space and laterally displaces member  307 , both members are then further displaced laterally so that the medial wall of member  309  is positioned substantially at or lateral to the medial border of the ipsilateral pedicle (plane 
     A of  FIG. 8B ). At least a portion of the total implant  301  is positioned onto the lateral aspect of the epiphyseal ring. In an embodiment, at least a portion of the lateral wall of member  307  is positioned substantially at the lateral surface of the inferior and or superior vertebral bone. Preferably, but not necessarily, a second implant  301  is placed on the contralateral side—as shown in  FIG. 21 . (In  FIG. 21 , the vertebral bone immediately inferior to the implanted disc space is show whereas the superior vertebral has been removed for diagrammatic simplicity.  FIG. 21  is similar to  FIG. 12B  and illustrates the use of implants  301  in the method of  FIGS. 10 to 12 .) Bone graft  310  may be confined to the region medial to each of the implants  301  on each side of the midline or positioned at any region of space  415 . Preferably, but not necessarily, the bony end plates of the upper/lower vertebral bones are not decorticated in the regions over which the implant(s)  301  are positioned, 
     While implant  301  is illustrated with two members ( 307 &amp; 309 ), additional members may be employed to produce an implant of greater width.  FIGS. 22 to 24  illustrate an implant  801  having at least three members. Implant  801  is comprised of member  307 , member  309  and an intermediate member  811 . (It is understood that implants of greater width may be produced by the having more than one intermediate member  811 .) 
       FIG. 24A  shows multiple views of member  811 . There is a superior surface  8112  and inferior surface  8111 , which may be adapted to contain protrusions or be otherwise textured to increase fixation into the adjacent bone. Member  811  contains a front end  8115 , a back end  8116  and side walls  81182  and  81184 . Channels  8113  extend from superior surface  8112  to inferior surface  8111 . Side channel  81142  extends from a first side wall  81182  to channel  8113 , but does not extend to opposing wall  81184 . Side channel  81144  extends from a first side wall  81184  to channel  8113 , but does not extend to opposing wall  81182 . 
     Implants having one or more intermediate members  811  are particularly useful for placement medial (instead of lateral) to the implantation instrument  208  within the disc space.  FIG. 24B  is similar to  FIG. 8B  and illustrates a placement instrument  208  coupled to an implant  801  that has been passed into the target disc space. (Implant  801  is represented schematically in  FIG. 24B ). Unlike the lateral displacement of implant  105  that is illustrated in  FIG. 9A , implant  801  is displaced medially (i.e., towards the vertebral midline) as shown in  FIG. 24C , After removal of the placement instrument  208 , bone forming material (which may include e.g., autograft and/or allograft bone)  310  is placed lateral to the medially displaced implant  801 . As disclosed above, the placement instrument may be manually held by the operating surgeon, and/or configured to be anchored onto a segment of the adjacent vertebral bone(s) (such as, for example, to the pedicle portion), and/or anchored to the operating room table onto which the patient is positioned.  FIGS. 24D and 24E  illustrate the implant  801  and graft material  310  positioned within the target disc space. (Note that the superior vertebral bone has been removed to uncover the disc space for ease of illustration.) 
     An additional embodiment is disclosed in  FIGS. 25 to 33 . In this embodiment at least one intermediate member is positioned between the front-most member and the back-most member. While similar to member  811  of the prior embodiment, the intermediate members differs in that the axis of each of the center channels (i.e., channels  8113  in member  811 ) are substantially aligned at a right angle to one another when viewed in along direction of the longitudinal axis of the intermediate member. This allows the implant to expand in both height and width as it transitions from the open to the closed configurations - as will be shown further bellow. 
       FIG. 25  illustrates implant  825  in the open configuration. Implant  825  has a front most member  830 , an intermediate member  835  and back-most implant  840 . Each of the members has a height H, a length L and width W. While these dimensions may vary between the members, in an embodiment, the length and width of all three members are substantially equal. The height of member  840  is substantially equal to the height of member  830  when added to the height of member  835 .  FIG. 25  shows implant  825  in the open configuration with member  830 ,  835  and  840  arranged in a linear configuration.  FIG. 26  shows an exploded view. As in prior embodiments that were disclosed above, the members on implant  825  are coupled using connecting members  848  and  850 . Connector members  848  and  850  are similar to member  701  and substantially differ only in the dimensions of the constituent segments. 
       FIG. 27  illustrates member  830 . There is a superior surface  8302 , which in one embodiment, contains protrusions or is otherwise textured to increase fixation into the adjacent bone. Member  830  contains a front end  8305 , a back end  8306  and side walls  8308 . Channel  8303  extends from one side wall  8308  to the other side wall. Channel  8304  extends from inferior surface  8301  to channel  8303 , but does not extend to the superior surface  8302 . Channels  8303  and  8304  are configured to accept member  848 . Back end  8306  contains curved segments  83062  that allow member  830  to rotate from a anterior to a superior position relative to member  835  - as will be discussed below. An anterior cutout  8309  accommodates complimentary protrusion  8359  of member  835  to form a locking feature. 
       FIG. 28  shows multiple views of member  835 . There is a superior surface  8352  and inferior surface  8351 . The latter may be adapted to, in one embodiment, contain protrusions or be otherwise textured to increase fixation into the adjacent bone. Member  835  contains a front end  8355 , a back end  8356  and side walls  83582  and  83584 . Channel  8353  extends from superior surface  8352  to inferior surface  8351 . Side channel  83542  extends from a first side wall  83582  to channel  8353 , but does not extend to opposing wall  83584 . Channel  8357  extends from side wall  83582  to  83584 . Side channel  83544  extends from superior surface  8352  to channel  8357  but does not extend to the inferior surface. Protrusion  8359  extends from superior surface  8352 . 
       FIG. 29  shows multiple views of member  840 . There is a superior surface  8402  and inferior surface  8401 , which contain protrusions or are otherwise textured to increase fixation into the adjacent bone in one embodiment. Member  840  contains a front end  8405 , a back end  8406  and side walls  8408 . Channel  8403  extends from superior surface  8402  to inferior surface  8401 . Side channel  8404  extends from a first side wall  8408  to channel  8403 , but does not extend to opposing wall  8408 . Channels  8403  and  8404  are configured to accept member  850 . Front end  8405  contains curved segments  84052  that allow member  840  to rotate from a posterior to a side position relative to member  835 —as will be discussed below. An indentation  8409  is positioned on a back end  8406  and configured to receive a complimentary protrusion from an implant placement instrument. 
     Application of a Force along direction A ( FIG. 30 ) while holding stationary the front end  8305  of member  830  will produce transition of implant  825  from the first (open) to the second (partially closed) configuration. In the latter, member  830  will forcibly rotate from a position in front of member  835  to a position on top of member  835 —as shown in  FIG. 30 .  FIG. 31  is a partially exploded view intended to illustrate the position of member  848 . Protrusion  8359  extends from superior surface  8352  and will become positioned within cutout  8309  of member  830 . This provides a locking feature that resists the forward migration of member  830  relative to member  835 . (Note that, at this point of the transition of the implant  825 , the placement instrument prevents member  840  from rotating to the side of member  835 .) 
     At this point, the placement instrument will allow member  840  to rotate from a position posterior to member  835  to a position besides member  835 —as is shown in  FIG. 32 . ( FIG. 33  is a partially exploded view intended to illustrate the position of member  850 .) Note that this step allows the implant to transition from the second configuration (partially closed) to a third configuration (fully closed) and is similar in action to the transition of implant  301 frorn the first configuration (open) to the second configuration (closed) that was described previously. While not shown, it is further contemplated that a locking feature may be added to retain implant  825  in the third configuration. That is, a locking feature may be added to immobilize members  840  and  835  relative to one another, once the third configuration has been reached. 
     In use of implant  825 , member  830  is advanced into disc space wherein the space needed for implant advancement is that of the width and height of member  830 . With transition into the second configuration (partially closed) of implant  825 , the implant height expands to that of the sum of the height of members  830  and  835 . With transition into the third configuration (fully closed), the implant width expands to that of the sum of the width of members  840  and the width of the member  835  or  830  with the greater width. In this way, implant  825  expands in both height and width after implantation into the disc space. 
     An additional embodiment  505  is illustrated in a side and an oblique view ( FIG. 34A ), wherein implant  505  is in an expanded configuration. Implant  505  is comprised of a variable number of foldable regions  5052  and interconnecting regions  5054 . An end segment  5056  is poisoned at a first end and an end segment  5058  is positioned at an is opposing end. When end segments  5056  and  5058  are forcibly moved towards one another (as in direction K of  FIG. 34B ), the foldable regions  5052  increase in diameter (dimension M) and decrease in length (dimension N) to produce the folded configuration shown in  FIG. 34B . Note that foldable regions are placed on one side of the interconnection segments  5054  in one embodiment. That is, when considered in the direction of dimension M ( FIG. 34A ), implant  505  has foldable regions on one side and interconnecting regions on the other side of the implant. With transition to the folded configuration, all foldable regions  5052  remain on the same side of the interconnecting segments  5054 . 
     In use, the implant  505  is positioned in the disc space through the space lateral to the thecal sac and substantially medial to the pedicle of the inferior vertebral bone. The implant is placed into the disc space while in the expanded configuration shown in  FIG. 34A . A force is applied to implant  505  so as to transition the implant into the folded configuration of  FIG. 34B . The instrumentation that guides the implant into the disc space and applies the force needed to transition the implant into the folded configuration (instrumentation not shown) may also be adapted to permit the folding of the most distal foldable regions  5052  first (closer to distal end  5056 ) so as to have only the portion of the implant already within the disc space fold while that portion exterior to the disc space remain in the extended (non-folded) state. Once a foldable segment  5052  is in the disc pace, then it is permitted to fold by the placement instrumentation. When positioned into the disc space and deployed into the folded configuration, it is the lateral (side) surfaces (such as  50542  and  50522 ) of the implant that abut the adjacent vertebral bone and bear the load that is transmitted through the disc space. 
     Expandable interbody spacers are known in the art and include disclosures of U.S. Pat. No. 6,86,673; U.S. Patent Application Publication Nos. 2011/0213465, and 2011/0251693, and others; each of which is incorporated herein by reference in its entirety. In at least some of these devices, the spacer is expanded by the addition of at least one or more stackable segments within the implant.  FIG. 35A  shows side and end-on views of generic expandable implant  705  that is adapted to expand along direction “E” after implantation into the target disc space. With expansion, the disc space is distracted and its height is increased. The expanded implant is shown in  FIG. 35B . Note that the implant is positioned within the disc space with the axis of expansion “E” being substantially in the direction of the long axis (i.e., caudad cephalad) of the spinal column. In this way, surface  7052  would abut the inferior surface of the vertebral bone immediately superior to the implanted disc space. Likewise, surface  7054  would abut the superior surface of the vertebral bone immediately inferior to the implanted disc space. In the current disclosure, an implant  705  is positioned into the disc space on at least one side of the vertebral mid-sagittal plane. (In one particular embodiment, the implants are placed bilaterally.) The implant is positioned with the axis of expansion “E” being substantially in the direction of the horizontal axis of the implanted disc space. In this way, a first side surface  7056  abuts the inferior surface of the superior vertebral bone and the opposing side surface  7056  abuts the superior surface of the inferior vertebral bone.  FIG. 36A  shows the implant  705  being introduced into the target disc space through a posterior trajectory “A”, wherein the lateral surface of the implant is positioned substantially at the medial aspect of the pedicle of the inferior vertebral bone (plane “A” of  FIG. 8B ). Implant  705  is expanded laterally within the disc space along axis of expansion “E”. The implant may also be displaced laterally within the disc space so that the lateral aspect of the implant is at least positioned to overlay the lateral aspect of the epiphyseal ring, and, to rest substantially at the very lateral extent of the disc space in one variant—as shown in  FIG. 36B . (Note that the sequence of implant expansion and translation may be interchangeable.)  FIG. 37  shows the implants positioned bilaterally, as would be the configuration in one particular embodiment. 
     In an alternative embodiment, each of one implant  755  is advanced through a posterior corridor via trajectory “A” into the disc space ( FIG. 38A ). The implant is rotated laterally on each side ( FIG. 38B ) and a second implant  775  is positioned via trajectory “A” into the disc space ( FIG. 39A ). Each implant  775  is translated laterally so that its medial border is substantially aligned with plane “A” of  FIG. 8B  (Figure to  3913 ). Implant  755  and  775  may be attached to one another after intra-discal implantation, before intra-discal implantation, or not at all. 
     In another embodiment, one or more implants  795  are positioned into the disc space through a posterior corridor via trajectory “A” (of  FIG. 40A ) into the disc space. Each implant is rotated about a center of rotation “Z” that is centered substantially at the lateral surface of the implant. In one variant, the procedure is performed bilaterally.  FIG. 40A  shows the implants  795  prior to rotation, wherein the lateral implant surface is substantially aligned with plane “A” of  FIG. 813 .  FIG. 40B  illustrates the implants after rotation, wherein the medial border of one or more implants is substantially aligned with plane “A” of  FIG. 813 . As disclosed previously, bone forming material can then be placed within the space between the medial aspect of the implants on one side of the vertebral midline (i.e., mid-sagittal plane) and the medial aspect of the implants on opposing side of the vertebral midline. It should be understood that bone forming material may be placed medial to the laterally positioned implants in any of the disclosed embodiments of this application. 
     Preferably, but not necessarily, supplemental fixation of the implanted FSU is placed in order to rigidly immobilize the superior and inferior vertebral bones. Pedicle screw immobilization can be employed by the placement of a bone screw into the posterior aspect of the ipsilateral pedicle of each of the superior and inferior vertebral bones (a screw enters each of the bones at or about  811  of  FIG. 113 ). The two screws are then rigidly interconnected by a third member, such as a rod or plate. The procedure may be repeated on the contra-lateral side. Pedicle screw fixation of adjacent vertebral bones is well known in the art and is disclosed in U.S. Pat. No. RE 37665, U.S. Patent Application Publication No. 2006/0084981, and many others. (The enumerated art is incorporated by reference in its entirety). 
     As an alternative (or in addition) to pedicle screw fixation, a spinous process fixation implant may be used for supplemental fixation. A generic spinous process fixation implant is illustrated in  FIG. 41 . Implant  605  is comprised of first member  610  and opposing member  612  that are configured to be attached onto opposing (contra-lateral) sides of two adjacent vertebral bones. The spinous processes are forcibly captured between member  610  and  612 . An interconnecting member  615  is then locked relative to members  610  and  612  and prevents them from moving away from one another. Projections  617  penetrate the spinous processes and increase bone fixation of member  610  and  612 . 
       FIGS. 42A and 4213  show a lateral and axial view of the implanted FSU. Note that the interbody device is, in one variant, placed bilaterally. In the axial plane ( FIG. 4213 ), the interbody devices provide two anterior column supports while plate  605  provides a posterior midline support. In the lateral view ( FIG. 42A ), the interbody implant forms an anterior abutment surface and plate  605  forms posterior abutment surface. In this way, the implant assembly forms a balanced three-point support of the vertebral bones. Additional bone graft material may be placed between the spinous process and/or lamina of the superior and inferior vertebral bones after appropriate decortication of the bone at the intended graft recipient site.  FIG. 43  provides a step-wise overview of the procedure for implantation of at least implant  301 —as well as others. 
     The disclosed devices or any of their components can be made of any biologically adaptable or compatible materials. Materials considered acceptable for biological implantation are well known and include, but are not limited to, stainless steel, titanium, tantalum, combination metallic alloys, various plastics, resins, ceramics, biologically absorbable materials and the like. Any components may be also coated/made with osteo-conductive (such as deminerized bone matrix, hydroxyapatite, and the like) and/or osteo-inductive (such as Transforming Growth Factor “TGF-B,” Platelet-Derived Growth Factor “PDGF,” Bone-Morphogenic Protein “BMP,” and the like) bio-active materials that promote bone formation. Further, any surface may be made with a porous ingrowth surface (such as titanium wire mesh, plasma-sprayed titanium, tantalum, porous CoCr, and the like), provided with a bioactive coating, made using tantalum, and/or helical rosette carbon nanotubes (or other carbon nanotube-based coating) in order to promote bone in-growth or establish a mineralized connection between the bone and the implant, and reduce the likelihood of implant loosening. Lastly, the system or any of its components can also be entirely or partially made of a shape memory material or other deformable material. 
     It will be recognized that while certain embodiments of the disclosure are described in terms of a specific sequence of steps of a method, these descriptions are only illustrative of the broader methods, and may be modified as required by the particular application. Certain steps may be rendered unnecessary or optional under certain circumstances. Additionally, certain steps or functionality may be added to the disclosed embodiments, or the order of performance of two or more steps permuted. All such variations are considered to be encompassed within the disclosure and claimed herein. 
     While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made by those skilled in the art without departing from the contents of the disclosure. The foregoing description is of the best mode presently contemplated. This description is in no way meant to be limiting, but rather should be taken as illustrative of the general principles embodied herein. The scope of the present disclosure should be determined with reference to the claims.