Abstract:
Disclosed are surgical implants for providing therapy to a treatment site, tool sets and methods for percutaneously accessing and deploying the implants within the spines. The treatment site may be a vertebral body, disc, and/or motion segments in the lumbar and sacral regions of the spine.

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional App. 61/851,976, filed Mar. 14, 2013, which is incorporated by reference in its entirety herein. Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present invention relates to medical devices, systems and methods used in minimally invasive spinal surgery. More particularly, this invention is directed to spinal stabilization and arthrodesis by implantation of devices via a pre-sacral approach. 
       BACKGROUND 
       [0003]    The present disclosure is an extension of work assigned to TranS1 Inc. with a principle place of business located in Raleigh, N.C. Much of the access work is described in great detail in the many commonly-assigned applications including U.S. Pat. No. 7,530,993 which describes surgical tools, tool sets and methods for percutaneously accessing and preparing treatment sites on the sacrum of the spine. As described in the present disclosure and application, after the spine is accessed, various devices and tools can be inserted into the spine trans-sacrally in order to treat various spinal disorders and injuries. Examples of such procedures and associated devices and tools are disclosed in additional applications including U.S. Provisional Patent Application No. 60/182,748, filed Feb. 16, 2000, U.S. patent application Ser. No. 09/640,222, filed on Aug. 16, 2000 now U.S. Pat. No. 6,575,979, U.S. patent application Ser. No. 09/782,583 filed on Feb. 13, 2001, now U.S. Pat. No. 6,558,390, U.S. patent application Ser. No. 09/848,556 filed on May 3, 2001, now U.S. Pat. No. 7,014,633, U.S. patent application Ser. No. 10/125,771 filed on Apr. 18, 2002, now U.S. Pat. No. 6,899,716, U.S. patent application Ser. No. 10/309,416 filed on Dec. 3, 2002, now U.S. Pat. No. 6,921,403, U.S. patent application Ser. No. 10/972,065, filed on Oct. 22, 2004, U.S. patent application Ser. No. 11/189,943 filed Jul. 26, 2005, now U.S. Pat. No. 7,608,077, and U.S. patent application Ser. No. 11/501,351, filed on Aug. 9, 2006, U.S. Provisional Application No. 61/259,977 filed on Nov. 10, 2009 and U.S. patent application Ser. No. 12/916,463 filed Oct. 29, 2010, the contents of each of which are incorporated in their entirety into this disclosure by reference herein. 
         [0004]    The trans-sacral approach to lumbar surgery described in the above-referenced patents and patent applications represents a pioneering and innovative approach to spinal surgery. In addition, the surgical tools and methods described in these references provide for a minimally invasive and reproducible approach for providing access to primarily, but not limited to, the L4-L5 and L5-S1 vertebral bodies. The devices and methods described above are commercially available and are made by TranS1, Inc. and sold under the trademark AXIALIF®. Accordingly, the background of the disclosure provided herein does not repeat all of the detail provided in the earlier applications, but instead highlights how the present disclosure adds to this body of work. Moreover, as with any implants, surgical tools and methods, there remains a need to continuingly improve such implants, tools and methods. 
         [0005]    The spine is formed of a series of bones called vertebrae. A vertebra consists of two essential parts including an anterior segment or body, and a posterior part, or vertebral or neural arch. These two parts enclose the vertebral foramen, which together form a canal for the protection of the spinal cord. The vertebral arch consists of a pair of pedicles and a pair of laminae. The body is the largest part of a vertebra, and is generally cylindrical with flattened upper and lower surfaces. The pedicles are two short, thick processes, which project backward, one on either side, from the upper part of the body, at the junction of its posterior and lateral surfaces. 
         [0006]      FIG. 1  shows the various segments of a human spinal column as viewed from the side. Each pair of adjacent vertebral bodies and the intervertebral space contributes to the overall flexibility of the spine (known as a motion segment) and contributes to the overall ability of the spine to flex to provide support for the movement of the trunk and head. The vertebrae of the spinal cord are conventionally subdivided into several sections. Moving from the head to the tailbone, the sections are cervical  104 , thoracic  108 , lumbar  112 , sacral  116 , and coccygeal  120 . The individual segments within the sections are identified by number starting at the vertebral body closest to the head. Of particular interest in this application are the vertebral bodies in the lumbar section and the sacral section. As the various vertebral bodies in the sacral section are usually (naturally) fused together in adults, it is sufficient and perhaps more descriptive to merely refer to the sacrum rather than the individual sacral components. 
         [0007]    The individual motion segments within the spinal columns allow movement within constrained limits and provide protection for the spinal cord. The discs are important to allow the spinal column to be flexible and to bear the large forces that pass through the spinal column as a person walks, bends, lifts, or otherwise moves. Unfortunately, for a number of reasons noted below, for some people one or more discs in the spinal column will not operate as intended. The reasons for disc problems range from a congenital defect, disease, injury, or degeneration attributable to aging. Often when the discs are not operating properly, the gap between adjacent vertebral bodies is reduced and this causes additional problems including pain. 
         [0008]    Instability of spinal joints may result from, for example, trauma (to ligamentous structures; fracture, or dislocation); degenerative disease processes (e.g., rheumatoid arthritis; degenerative spondylosis; spondylolisthesis; spinal stenosis); tumor; infection, or congenital malformation that may lead to significant pathological translation, or longitudinal displacement. Cord compression and trauma to the spinal cord can result in respiratory distress, pain, nerve dysfunction, paresis and paralysis, or even sudden death. Therefore, the need for spinal stabilization in the setting of pathological instability is paramount. 
         [0009]    Spinal arthrodesis, or fusion, provides needed biomechanical stability and is a therapy used to treat such instability. The objective is to create a stable biomechanical environment and provide the biological requirements for osseous fusion. Adequate decompression of the neurological structures, where indicated, and recreation of normal sagittal and coronal alignment are prerequisites prior to an arthrodesis procedure. Spinal fixation has been achieved using a variety of techniques to provide stabilization and/or spinal alignment, followed by fusion, or arthrodesis by means of bone graft insertion. Over the years, various techniques and systems have been developed for correcting spinal injuries and/or degenerative spinal processes. One class of solutions is to remove the failed disc and then fuse the two adjacent vertebral bodies together with a permanent but inflexible spacing, also referred to as static stabilization. Fusing one section together ends the ability to flex in that motion segment. However, as each motion segment only contributes a small portion of the overall flexibility of the spine, it can be a reasonable trade-off to give up the flexibility of a motion segment in an effort to alleviate significant back pain. 
         [0010]    Thus, spinal correction frequently requires stabilizing a portion of the spine to facilitate fusing portions of the spine or other correction methodologies and medical correction of this type is frequently employed for many spinal conditions, such as, for example, degenerative disc disease, scoliosis, spinal stenosis, or the like. Frequently, these corrections also require the use of implants and/or bone grafts. Stabilizing the spine allows bone growth between vertebral bodies such that a portion of the spine is fused into a solitary unit. 
         [0011]    Among techniques and systems that have been developed for correcting and stabilizing the spine and facilitating fusion at various levels of the spine is a system for axial trans-sacral access. One example of axial trans-sacral access to the lumbo-sacral spine as shown in  FIGS. 2A and 2B  below, reduces the need for muscular dissection and other invasive steps associated with, traditional spinal surgery while allowing for the design and deployment of new and improved instruments and therapeutic interventions, including stabilization, mobility preservation, and fixation devices/fusion systems across a progression-of-treatment in intervention.  FIGS. 2A and 2B  show an example of a process of “walking” a blunt tip stylet  204  up the anterior face of the sacrum  116  to the desired position on the sacrum  116  while monitored on a fluoroscope (not shown). This process moves the rectum  208  out of the way so that a straight path is established for the subsequent steps.  FIG. 2C  illustrates a representative axial trans-sacral channel  212  established through the sacrum  116 , the L5/sacrum intervertebral space, the L5 vertebra  216 , the L4/L5 intervertebral space, and into the L4 vertebra  220 . 
         [0012]    The use of a trans-sacral approach to provide spinal therapy is described in co-pending and commonly assigned U.S. Pat. Nos. 6,921,403, 7,588,574 and which are incorporated by reference into this application. A brief overview of this method of accessing the spinal region to receive therapy is useful to provide context for the present disclosure. As shown in  FIG. 2A , a pre-sacral approach through percutaneous anterior track towards sacral target, through which trans-sacral axial bore will be made and the access channel extended distally for subsequent advancement of multi-level axial spinal stabilization assemblies. An anterior, pre-sacral, percutaneous tract extends through the pre-sacral space anterior to the sacrum. The pre-sacral, percutaneous tract is preferably used to introduce instrumentation to access and prepare the access channel (e.g., by drilling a bore in the distal/cephalad direction through one or more lumbar vertebral bodies and intervening discs). “Percutaneous” in this context simply means through the skin and to the posterior or anterior target point, as in transcutaneous or transdermal, without implying any particular procedure from other medical arts. However, percutaneous is distinct from a surgical access, and the percutaneous opening in the skin is preferably minimized so that it is less than 4 cm across, preferably less than 2 cm, and, in certain applications, less than 1 cm across. The percutaneous pathway is generally axially aligned with the bore extending from the respective anterior or posterior target point through at least one sacral vertebral body and one or more lumbar vertebral body in the cephalad direction as visualized by radiographic or fluoroscopic equipment. 
         [0013]    More specifically, as shown in  FIG. 2B , the lumbar spine is accessed via a small skin puncture adjacent to the tip of the coccyx bone. The pre-sacral space is entered, using standard percutaneous technique, and the introducer assembly with the stylet&#39;s blunt tip serving as a dilator is placed through the paracoccygeal entry site. Once the tip of the stylet is through the facial layer, the blunt tip is rotated back against the anterior face of the sacrum and “walked” to the desired position on the sacrum under fluoroscopic guidance. Once the target site has been accessed and risk of soft tissue damage mitigated, the blunt-tipped stylet is removed and a guide pin, or wire, is safely introduced through the guide pin introducer tube, and “tapped in”. The guide pin establishes the trajectory for placement of subsequent bone dilators and sheath through which a twist drill is introduced creating an axial bore track, the lumen of which is extended distally. The guide pin maintains the axial alignment of access and preparation tools as well as the alignment of cannulated spinal stabilization devices and assemblies, of larger diameter than the bore track, that are subsequently introduced over a 23″ long, 0.090″ diameter guide pin and through an exchange cannula for deployment within the vertebral column, as described at least in part in co-pending and commonly assigned U.S. patent application Ser. Nos. 10/972,065, 10/971,779, 10/971,781, 10/971,731, 10/972,077, 10/971,765, 10/971,775, 10/972,299, and 10/971,780, all of which were filed on Oct. 22, 2004, and in co-pending and commonly assigned U.S. Provisional Patent Application “Method &amp; Apparatus for Access &amp; Deployment of Spinal Stabilization Devices Through Tissue”, 60/706,704 filed Aug. 9, 2005, and Exchange System For Axial Spinal Procedures Ser. No. 11/501,351 filed Aug. 9, 2006, and all of which are incorporated by reference herein in their entirety. 
         [0014]    U.S. patent application Ser. No. 12/916,463, which is hereby incorporated by reference in its entirety, discloses additional methods, techniques and devices for providing a trans-sacral approach to provide spinal therapy. For example, the tissue retraction device (not shown)) can be inflated or otherwise expanded to device a working space or channel that is generally positioned between the bowl and the sacrum. The working space or channel created by the tissue retraction device can form a portal that extends from a target site on a patient&#39;s sacrum towards or to an surgical access site such that tools and instruments can be inserted from the surgical access site, through the portal and to the target site. In these examples, the tissue retraction device can serve to protect the patient&#39;s soft tissue (e.g., the bowel) as the instruments are advanced towards the target site on the sacrum. In certain examples, the tissue retraction device can provide substantially 360 degrees (about the longitudinal axis of the device) of protection about the portal. In this manner, as tools are advanced towards the access site the tissue retraction device completely surrounds such tools preventing the tools from contacting or traumatizing the soft tissues of the patient. In other examples, the tissue retraction device can form an atraumatic barrier between the tools and the bowel as tools are passed over or partially through the device. In certain examples, the tissue retraction device can also retract the bowel from the sacrum and/or dissect tissue. An advantage of certain examples is that the tissue retractor can conform to the face of the sacrum. 
         [0015]    While stabilization procedures, and in particular surgical implants, instrumentation, and techniques, continue to evolve in the pursuit of improvements in clinical outcomes (e.g., the highest fusion rate with the shortest time to fusion and improvement in neurological function), and in simplicity of use, notwithstanding, there remains a need for ongoing advancements in spinal implant constructs and systems leading to progress in the surgical management of complex spinal disorders, to accommodate an increased spectrum of anatomical variations, to enable simplicity of instrumentation placement, and to avoid certain adverse events such as loss of spinal alignment, in order to achieve more rigid stabilization in a wider variety of spinal diseases. 
         [0016]    There are disclosed herein surgical implants, instruments and methods for minimally invasive spinal stabilization or fusion. It is believed that the use of the systems disclosed herein will overcome limitations noted above and will result in improved maintenance of alignment, increased rate of successful arthrodesis, and minimized occurrence of adverse events as evidenced by clinical and radiographic outcomes. 
       GENERAL COMMENTS AND TERMINOLOGY 
       [0017]    In the context of the present disclosure, as used herein the terms “assembly” or “constructs” are sometimes used interchangeably and refer to implants, implant systems, instruments, or instruments systems which are configured to comprise multiple components, which may or may not be contiguous. It is further understood that individual components may themselves be configured as sub-assemblies, e.g., comprising a plurality of component materials, and that the formation of the components may involve intermediate processes or appliances. It is further understood that the terms spinal implants, implants, devices, cages, mini-cages, pre-sacral mini-cages and/or spacers are sometimes used interchangeably, and moreover, that “pre-sacral” refers to the fact that the devices are advanced through the pre-sacral space to subsequently access (e.g., by means of trans-sacral insertion) and be deployed into or at an intended target site for therapy, e.g., in a motion segment vertebral body or disc space. 
         [0018]    It will also be understood that upon formation of assemblies from multiple components and deployment, individual components of the present disclosure may or may not remain as discernibly distinct. It will also be understood that, for convenience, system components may be packaged and provided either individually, or as in “kits,” and either as reusable or disposable. 
         [0019]    As used herein, the term “biocompatible” refers to an absence of chronic inflammation response or cytotoxicity when or if physiological tissues are in contact with, or exposed to (e.g., wear debris) the materials and devices of the present disclosure. In addition to biocompatibility, in another aspect of the present disclosure it is preferred that the materials comprising the implant and instrument systems are sterilizable. 
         [0020]    In one aspect of the present disclosure, certain components of the device assemblies and systems of the present disclosure are configured to comprise biocompatible materials and are able to withstand, without wear, multiple cycles/procedures without failing. For example, materials selected may include but are not limited to, biomedical titanium, cobalt-chromium, or medical grade stainless steel alloys. 
         [0021]    It will be further understood that the length and dimensions of implant components and instruments described herein will depend in part on the target site selection of the treatment procedure and the physical characteristics of the patient, as well as the construction materials and intended functionality, as will be apparent to those of skill in the art. 
         [0022]    In order to make it easier for a reader to find certain sections of this document that are of particular interest to the reader, a series of headings have been used. These headings are solely for the purpose of helping readers navigate the document and do not serve to limit the relevance of any particular section exclusively to the topic listed in the heading. 
         [0023]    In the context of this discussion: anterior refers to “in front” of the spinal column; (ventral) and posterior refers to “behind” the column (dorsal); cephalad means towards the patient&#39;s head; caudal refers to the direction or location that is closer to the feet. Proximal is closer to the surgeon; distal is in use more distant from the surgeon. “Superior” refers to a top or front surface, while “inferior” refers to a back or bottom surface of a device. When referencing tools, distal would be the end intended for insertion into the patient and proximal refers to the other end, generally the end closer to, e.g., a handle for the tool and the user. 
         [0024]    The sequence of operations (or steps) is not limited to the order presented in the claims or figures unless specifically indicated otherwise. 
       SUMMARY 
       [0025]    Many variations of spinal implants exist on the market today. However, prior systems are limited in the way of minimally invasive placement of implant systems within the disc space. Accordingly, there is a need for improved systems and methods that permit a combination of axial and lateral or radial deployment of devices into the disc space in a low-trauma manner. As used herein, the terms “laterally” and “radially” are sometimes used interchangeably to describe deployment of the spinal implants of the present disclosure within the disc space. 
         [0026]    Currently, using the trans-sacral approaches described above various types of implants can be inserted into the spine. Such implants are sold and made by TranS1 Inc., for example, under the trade name “AXIALIF® Plus.” These implants generally extend across a disc space and into at least two portions of bone superiorly and inferiorly to the disc space. While such implants have been proven to be successful, there is a general need to continue to provide additional implants and techniques that can be used in conjunction with the currently available trans-sacral implants and/or to replace such implants in order to provide improved flexibility, strength and/or stability. 
         [0027]    Accordingly, described below are various examples that provide (generally, one or a plurality of) preformed cages, or a system (e.g., of interlocked cages) of cages, spacers, and/or plugs that can be implanted into the L4-S1 disc spaces using a TranS1 presacral approach. 
         [0028]    In general, the term cage may refer to an implant or device which facilitates fusion, e.g., by means of incorporation of bone growth media for example in channels in the device which may promote bone in-growth into the device and or between vertebral bodies above and below the disc space into which the implant is inserted. The term spacer may refer to a device or implant, including a cage, whether threaded or unthreaded, which may assist in distracting (increasing the distance therebetween) or supporting the vertebral bodies of a motion segment above and below the disc space into which the spacer is inserted, and which also may correct lordosis (e.g., if wedge shaped). As used herein, the term plug generally refers to a device which fills an access channel through which an implant was introduced, and which precludes migration or egress of a device or of bone growth media back out of the channel. An AXIALIF® implant itself may serve as a plug. As used herein, these terms may sometimes collectively refer to and be used interchangeable with one another with respect to the devices and implants described in the present disclosure 
         [0029]    The implants as described in the present disclosure may be used as stand-alone devices and/or in conjunction with an AXIALIF® implant and/or with accompanying posterior fixation devices. When used as adjunct implants, these devices are inserted first into the disc space in the sequence of device deployment, e.g., prior to an AXIALIF® implant. In certain instances, there may be surgical advantages of use of the presently disclosed implants as stand-alone devices, e.g., without an accompanying AXIALIF® implant, e.g., simplicity in terms of fewer steps in deployment. The devices as presently disclosed may also provide added compressive strength to weaker graft material or act as stabilizers to give supplemental stiffness to the construct. In doing so, earlier fusion results may occur more reliably across a larger patient population. 
         [0030]    Advantages (vary depending on device design) can include added stabilization; limitation on anterior flexion (or lateral bending/flexion-extension); lordosis correction (e.g., wedge designs) or spondylolisthesis correction; prevent subsidence and transition syndrome. 
         [0031]    In accordance with this aspect of the present invention, the devices disclosed herein are believed to prevent the phenomena of subsidence and transition syndrome. As used herein, subsidence refers to the detrimental descent of an orthopedic implant into bone that surrounds it. Transition syndrome refers to altered biomechanics and kinematics of contiguous vertebral levels and concomitant risk of adjacent motion segment instability that may occur as a result of spinal therapeutic procedures that are suboptimal in terms of their ability to restore physiological function &amp; properties, and thus risk a cascading deleterious effect on surrounding otherwise healthy tissue. 
         [0032]    Additional advantages and characteristics of certain examples of presently disclosed devices include that they:
       Provide additional anterior support with respect to compressive loading, and stabilization For example, when used as an adjunct device with an AXIALIF® implant, devices of the present disclosure may limit anterior flexion during bone growth leading to fusion, improving patient outcomes   House graft/bone growth media   Exhibit similar compressive stiffness to bone Size range from 4-10 mm in height for varying sized disc spaces   Are able to be delivered through 12 mm outer diameter (OD; e.g., dilator sheath docked to sacrum) or about 10 mm inner diameter (ID), with a range of up to about 15.5 OD instruments/channel cannulated instruments   Are be able to be delivered through an access channel of about 7 mm   Have an increased surface area (endplate support footprint) and are able to withstand compressive loads   Minimize area consumed by the device to allow adequate area for bone to grow; anticipate providing/seeing better radiographic evidence of fusion       
 
         [0040]    Yet another advantage of the trans-sacral approach is that the disc annulus is left intact, which aids in device retention and containment once deployed. In some examples, the cages can be held in by friction fit and/or compressive axial loads, e.g., by means of accompanying posterior fixation. 
         [0041]    Certain examples of cages/systems, spacers, and plugs may be made of allograft, titanium (or alloys), Nitinol (nickel-titanium alloys that exhibit: shape memory and super-elasticity), or polyether ether ketone (PEEK), or combinations thereof (e.g., for “expandability” of implants) with heights ranging from between about 4 mm (posterior side) to about 10 mm (anterior side) and angles of 0 or for lordotic implants from between about 5 to about 10 degrees to assist in correcting the angle lordosis lost with DDD in the L4-S1 portion of the spine 
         [0042]    Many of the examples described herein address a design challenge that is involved with trans-sacral access. Specifically, many examples of cage designs can make a 90 degree turn to be placed into the disc space, i.e. progress form axial to lateral deployment, and can include tools for insertion and removal. 
         [0043]    As noted above, the device concepts as introduced via the trans-sacral approach (and as described herein are for convenience only sometimes interchangeably referred to as “mini-cages”) are spinal implants that may be used in conjunction with AXIALIF®implants (e.g., to achieve improved biomechanical stability with respect to, for example, spondylolisthesis and/or lordosis correction) and/or posterior fixation (e.g., via pedicle screws or facet screws), or as “stand-alone” devices. Certain mini-cage designs (including but not limited to examples as described and shown below) provide anterior support in the form of a cage or scaffold to provide a structure for fusion, that can be placed through channel and into disc space to provide structural support as well as a platform or construct for bone to form on for fusion. 
         [0044]    Aspects of the teachings contained within this disclosure are addressed in subsequent claims submitted with this Provisional Application upon filing, and/or with its conversion to a formal patent application. Rather than adding redundant restatements of the contents of the claims, these claims should be considered incorporated by reference into this summary, although the present disclosure in not intended to be limited in scope by these initial claims. 
         [0045]    This summary is meant to provide an introduction to the concepts that are disclosed within the specification without being an exhaustive list of the many teachings and variations upon those teachings that are provided in the extended discussion within this disclosure. Thus, the contents of this summary should not be used to limit the scope of the claims that follow. 
         [0046]    Inventive concepts are illustrated in a series of examples, some examples showing more than one inventive concept. Individual inventive concepts can be implemented without implementing all details provided in a particular example. It is not necessary to provide examples of every possible combination of the inventive concepts provided below as one of skill in the art will recognize that inventive concepts illustrated in various examples can be combined together in order to address a specific application. 
         [0047]    Other systems, methods, features and advantages of the disclosed teachings will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within the scope of and be protected by the accompanying claims. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0048]    The accompanying figures, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the system and method of the invention. Together with the description, the figures serve to explain the principles of the invention. Unless indicated, the components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced features designate corresponding parts throughout the different views. 
           [0049]      FIG. 1  shows the various segments of a human spinal column as viewed from the side 
           [0050]      FIGS. 2A &amp; 2B  show axial trans-sacral access to the lumbo-sacral spine 
           [0051]      FIG. 2C  illustrates a representative axial trans-sacral channel 
           [0052]      FIGS. 3A &amp; 3B  show examples of representative “mini-cages”/spacers, including a “spring” cage 
           [0053]      FIG. 4  illustrates examples of mini-cages/spaces deployed in conjunction with each other and with an AXIALIF® implant 
           [0054]      FIG. 5  illustrates a wedge system comprising a plurality of wedge components and a ramped insertion tool 
           [0055]      FIG. 6  illustrates the stages of insertion of one example of a wedge system 
           [0056]      FIG. 7  shows modular wedges inserted axially through wedge system cannula with ramp insertion tool and deployed radially in disc space 
           [0057]      FIG. 8  shows each wedge component can include a wedge protrusion and/or wedge slot where each slot and protrusion are configured to complement one another 
           [0058]      FIGS. 9A-C  illustrate a plurality of wedge components and ramped insertion tool that may be cannulated and configured to receive an insertion rod 
           [0059]      FIG. 10  illustrates a pre-sacral mini-cage “analog” to cages used in TLIF procedures 
           [0060]      FIG. 11  depicts a spinal implant that is arch-shaped to facilitate a 90° turn from axial access to lateral/radial deployment during insertion into the disc space 
           [0061]      FIG. 12  shows stacks of multiple, wafer-like implants 
           [0062]      FIG. 13  illustrates a 2-piece expandable plug inserted into the sacral access bore (plug does not extend into disc space) 
           [0063]      FIG. 14  shows a 1-piece, non-expanding plug 
           [0064]      FIG. 15  illustrates a 1-piece threaded cage comprising windows which carry bone graft material, and configured to maximize the device&#39;s “L-5 footprint” for axial/compressive load support and distribution 
           [0065]      FIG. 16  shows one example of a threaded spinal cage that is configured as an expandable “flower, e.g., with a plurality of “petals” at a distal end of the implant 
           [0066]      FIG. 17  illustrates an example of a threaded cage configured as a flower with petals as above, but the cage is also additionally configured for insertion into an endplate 
           [0067]      FIG. 18  depicts an example of a threaded cage configured as a flower with petals additionally configured to comprise Nitinol expandable joints 
           [0068]      FIG. 19  shows an example of a spinal cage configured with an angled or wedge-shaped posterior portion 
           [0069]      FIG. 20  shows an example of a cage with a non-wedged back, deployed by means of rotating a cam tool 
           [0070]      FIG. 21  shows a mini-cage example which is configured as an expandable device that in an expanded configuration distracts a disc space 
           [0071]      FIGS. 22 &amp; 23  depict spherical “bucky ball” mini-cages 
           [0072]      FIG. 24  illustrates an example of a modular, “connected” cage 
           [0073]      FIG. 25  illustrates examples of winged cages 
       
    
    
     DETAILED DESCRIPTION 
       [0074]    Described herein are examples directed toward a spinal implants/spacers and associated assemblies, especially for application in the spinal stabilization arena. However, as can be appreciated, the associated assemblies disclosed herein can be used in any of a number of clinical applications where insertion of a spinal implant or spacer into or through a vertebral body and/or disc space is desired. The devices, systems, and methods described herein are not intended to limit the scope of this disclosure. Rather, it will be apparent to one of skill in the art that the devices, systems, and methods disclosed herein can be used in varied clinical applications. Additionally, it should be noted that elements of one example can be combined with elements of another example, except where the function of the components prohibits such combinations. 
         [0075]    In some examples, a wedge system may be utilized to stabilize the spine. The wedge system is capable of being inserted into a disc space, and maintaining the desired spacing between the surrounding vertebrae. With reference to  FIGS. 5-9 , one example of a preferred wedge system is illustrated. In one aspect, the wedge system can include a plurality of wedge components, a ramped insertion tool, and a wedge system cannula (See  FIGS. 6-8 ). The wedge system can be configured to be implanted into a disc space between two vertebrae with a trans-sacral approach as described above. In one aspect, the wedge system is configured to be implanted into the disc space between the L5 and S1 vertebrae. 
         [0076]      FIG. 6  illustrates the stages of insertion of one example of a wedge system into one example motion segment. As  FIG. 6  shows, with a trans-sacral approach, an implant delivered to the disc space between the endplate of the upper vertebrae and the endplate of the lower vertebrae must make a sharp turn of approximately 90 degrees in order to move radially outwards from the access/insertion site. In some examples, the wedge system is configured to deliver at least one implant into the disc space with a trans-sacral approach, and then cause the at least one implant to move radially from the implantation site. In some examples, the implants can include a plurality of wedge components. In some examples, the plurality of wedge components, as illustrated in  FIG. 6 , are configured to abut the endplate of the upper vertebrae and the endplate of the lower vertebrae, providing a structural support and maintaining a desired vertebral spacing in the disc space between the endplates. 
         [0077]    As  FIG. 5  illustrates, in some examples a wedge system comprises at least one and often a plurality of wedge components and a ramped insertion tool. The plurality of wedge components can include a leading wedge component, or a 1 st  wedge component as depicted in  FIG. 5 , a trailing wedge component, or a 3 rd  wedge component as depicted in  FIG. 5 , and at least one middle wedge component, or a 2 nd  wedge component as depicted in  FIG. 5 . In some examples, as illustrated in  FIG. 6 , the wedge system can also include a wedge system cannula. In some examples, the plurality of wedge components and the ramped insertion tool are constructed to slide within the wedge system cannula. In some examples, the wedge system cannula is inserted using a trans-sacral approach, until its upper end is approximately flush with the endplate of the lower vertebrae at the implantation site. In some examples, the wedge system cannula is substantially perpendicular to the endplates. Then, in some examples, the ramped insertion tool can be forced axially through the wedge system cannula towards the disc space between the vertebral endplates forcing the wedge components into the disc space. The plurality of wedge components and ramped insertion tool can be configured such that as they are forced in a first direction along the axis of the wedge system cannula, each successive component in the plurality of components forces the component it is following to change direction and move radially outward from the implantation site in a second direction, substantially parallel to the endplates. In some examples, the second direction, the direction in which the plurality of wedge components travel radially outward from the access or insertion site, can be dictated by the rotational position of the ramped insertion tool about the axis of the wedge system cannula, and thus the plurality of wedge components. In some examples, the axial force applied to the ramped insertion tool can be provided by the user, an impact by an additional tool which may include, for example, a slap hammer, or the force could be supplied in a more controlled manner which may include for example, axial motion provided by a threaded portion of the wedge/insertion system. 
         [0078]    In some examples, as illustrated in  FIG. 5 , the 1 st  wedge component can include a first ramped surface. The 2 nd  wedge component can include a 2 nd  ramped surface. In some examples, the 2 nd  ramped surface of the 2 nd  wedge component is complimentary to the 1st ramped surface of the 1 st  wedge component. In some examples, as illustrated in  FIG. 6 , the plurality of wedge components can be configured so that advancement of the 2 nd  wedge component and the 2 nd  ramped surface against the 1 st  wedge component and 1 st  ramped surface in a first direction causes the 1 st  wedge component to move in a second direction that is generally perpendicular to the first direction. 
         [0079]    In some examples, the wedge insertion system can include a protection tool. In some examples, the protection tool can include a substantially flat portion which is configured to abut the endplate of the upper vertebra adjacent the implantation site. The substantially flat portion of the protection tool is configured to prevent the plurality of wedge components from breaking through the endplate of the upper vertebra during insertion. In some examples, the substantially flat portion is made of a material stronger than the endplate of a vertebra. 
         [0080]    In some examples, as illustrated in  FIG. 5 , the 2nd wedge component can include a 1 st  ramped surface. The 3rd wedge component can include a 2nd ramped surface. In some examples, the 2nd ramped surface of the 3rd wedge component is complimentary to the 1st ramped surface of the 2nd wedge component. In some examples, as illustrated in  FIG. 6 , the plurality of wedge components can be configured so that advancement of the 3rd wedge component and the 2nd ramped surface against the 2nd wedge component and 1st ramped surface in a first direction causes the 2nd wedge component to move in a second direction that is generally perpendicular to the first direction. In some examples, the movement of the 2 nd  wedge component in the second direction also causes the 1 st  wedge component to move in the second direction. 
         [0081]    In some examples, as illustrated in  FIG. 5 , the wedge system can include a ramped insertion tool. In some examples, the ramped insertion tool may include an insertion tool ramped surface. In some examples, the 3 rd  wedge component can include a 1 st  ramped surface. In some examples, the insertion tool ramped surface of the ramped insertion tool is complimentary to the 1 st  ramped surface of the 3 rd  wedge component. In some examples, as illustrated in  FIG. 6 , the plurality of wedge components can be configured such that advancement of the ramped insertion tool and the insertion tool ramp surface against the 3 rd  wedge component and 1 st  ramped surface in a first direction causes the 3 rd  wedge component to move in a second direction that is generally perpendicular to the first direction. In some examples, the movement of the 3 rd  wedge component in the second direction also causes the 1 st  wedge component and 2 nd  to move in the second direction. 
         [0082]    In some examples, the plurality of wedge components can include more than three wedge components. In some examples, the plurality of wedge components may include a plurality of middle wedge components, or 2 nd  wedge components as depicted in  FIG. 5 . In some examples, as illustrated in  FIG. 6 , each wedge component can include a top surface and a bottom surface. In some examples, the top surface can be configured to abut the endplate of the upper vertebrae. In some examples, the upper vertebra is the L5 vertebrae. In one example, the bottom surface can be configured to abut the endplate of the lower vertebra. In one example, the lower vertebra is the S1 vertebrae. In some examples, the ramped surfaces of each wedge component can be inclined or declined relative to the top surface and/or bottom surface. In some examples, the top surface may be substantially perpendicular to the bottom surface. In other examples, the top surface may be inclined relative to the bottom surface in order to achieve the desired relationship between the vertebrae above the disc space and the vertebrae below the disc space, e.g., in order to accommodate a lordotic angle between them. In one example, the 1 st  wedge component can include a leading edge upper surface and a leading edge lower surface, which converge towards a common point. The converging surfaces allow the 1 st  wedge component to self dilate/distract the disc space to the extent/position desired as it is being advanced radially. In one example, the leading edge upper surface and a leading edge lower surface are configured to aid in the movement of the 1 st  wedge component radially from the implantation site in a second direction. In some examples, the a leading edge upper surface and a leading edge lower surface are each inclined or declined relative to the top surface or bottom surface of the first wedge component. 
         [0083]    In some examples, as illustrated in  FIGS. 5 and 8 , each wedge component can include a wedge protrusion and/or wedge slot where each slot and protrusion are configured to complement one another. In addition, in some examples, the ramped insertion tool may comprise a tool slot configured to complement a wedge slot. In some examples, the wedge protrusions are configured to slide within a wedge slot or tool slot, to maintain the radial orientation of the plurality of wedge components during (and after) insertion. In some examples, the wedge protrusion of the 1 st  wedge component is configured to slide within the wedge slot of the 2 nd  wedge component. In some examples, the wedge protrusion of the 2 nd  wedge component is configured to slide within the wedge slot of the 3 rd  wedge component. In some examples, the wedge protrusion of the 3 rd  wedge component is configured to slide within the tool slot of the ramped insertion tool. In some examples, the complimentary wedge protrusions and wedge/tool slots may include means for retaining the plurality of wedge components together which may include, for example, a dovetail, a key, a metal link, a taper, etc. 
         [0084]    In some examples, as illustrated in  FIGS. 9A-C , the plurality of wedge components and ramped retention tool may be cannulated. In some examples, the cannulation can be configured to receive a retention rod. In some examples, the wedge system can include an insertion rod. The insertion rod can be inserted within the cannulation of the plurality of wedge components and ramped insertion tool. In some examples, the insertion rod can be configured (e.g., with protrusions or slots) to maintain the orientation and position of the plurality of wedge components until they are delivered into the disc space. In some examples, the tip of the insertion rod closest to the implantation site can include means for retaining the 1 st  wedge component, which may include for example, a friction fit, an external thread configured to complement a corresponding internal thread in the 1 st  wedge component, an enlarged portion configured to complement a recess formed within the 1 st  wedge component, etc. In some examples, the 1 st  wedge component may include an internal thread configured to complement an external thread of the insertion rod. In some examples, the 1 st  wedge component may not be completely cannulated to ensure that the insertion rod does not pass all the way through the 1 st  wedge component. In some examples, the means for retaining the first wedge component can be disengaged in order to deliver the plurality of wedge components into the disc space, which may include, for example, rotation of the insertion rod, pulling on the insertion rod, etc. 
         [0085]    In some examples, once the plurality of wedge components are installed in the disc space as illustrated in  FIG. 6D , the ramped insertion tool may be rotated as illustrated in  FIG. 6E . In some examples, the insertion tool is configured so that rotation of the insertion tool forces the plurality of wedge components even further radially outward in the second direction. In another example, rotation of the insertion tool may sever a means for retaining the 3 rd  wedge component to the insertion tool. In another example, rotation of the insertion tool continues to advance the spinal implant radially. 
         [0086]    In some examples, the wedge system cannula is circular in cross section. In some examples, the inner diameter of the wedge system cannula is between approximately 9 mm and 15 mm. In some examples, the plurality of wedge components are circular in cross section. In some examples, the ramped insertion tool is circular in cross section. In some examples, the outer diameter of the plurality of wedge components and ramped insertion tool is between approximately 9 mm and 15 mm. In some examples, the height, or the distance between the top surface and the bottom surface, of the plurality of wedge components is approximately 7 mm to 17 mm. In some examples, the height of the wedge components may vary. In some examples, the wedge components in the system are able to maintain lordotic angles of approximately 0 degrees to 10 degrees. In some examples, the wedge components may include a void/windows configured to accept graft material. In some examples, the wedge components may include tantalum marks for visualizing the disc space during and after insertion. In some examples, the spinal implants comprise endplate-contacting surfaces configured with angled teeth or ridges for device retention. 
         [0087]    In some examples, portions of the wedge system may be made from a variety of biocompatible materials which may include, for example, metal, titanium, stainless steel, Nitinol, purolitic carbon, polymers, polyether ether ketone, and other biocompatible materials known in the art. 
         [0088]    In yet another aspect and example, a trans-sacral spinal implant is serves and an analog to cages used in TLIF procedures. With reference to  FIGS. 3A ,  4 , and  10 , there is illustrated a trans-sacral spinal implant for insertion from anterior target site on the surface of the sacrum into a disc space, the implant having a length between a leading end and a trailing end, the length sufficient to contact each of two adjacent vertebrae; each of the leading end and trailing end including engagement surfaces, e.g., such as “teeth” or ridges, configured to engage endplates of the adjacent vertebrae and the implant having a width that is less than about 15 mm. In one aspect, one or multiple cages in any radial direction (anterior, anterio-lateral, lateral, posterior). In another aspect, a taller cage may be deployed in an anterior direction for lordosis and a shorter cage or cage construct may be deployed posterior. In still other aspects, the cage(s) may comprise: a lordotic angle(s) to fit L5/S1 endplate angle; a wedge design to self-distract disc space as it is being inserted; voids/windows for graft material; tantalum marks for visualizing in the disc space during and after deployment; materials configured from PEEK, allograft, titanium, tantalum, cobalt chrome, or combinations thereof. 
         [0089]    In still another aspect and example, as illustrated on  FIG. 11 , a trans-sacral spinal implant for insertion from an anterior target site on the surface of the sacrum into a disc space comprises an arched shaped body configured to navigate and facilitate an approximately 90 degree turn from axial access to lateral/radial deployment during insertion into the disc space, the arched shaped body having a leading end and a trailing end; the trailing end including a pivotable connection to an insertion device. In this example, the height of the spinal implant is about equal to/determined by the inner diameter of the cannula through which it is inserted for deployment. The attachment point to insertion tool allows rotation so cage can make turn. In some examples, an insertion tool may also have a spring to assist the cage in making the 90° turn. 
         [0090]    In yet another aspect and example, with reference to  FIG. 12 , a spinal implant construct/system is configured and deployed to comprise a stack of individual wafer-like devices, parallel to a vertebral endplate(s). In some examples, stacking one or multiple constructs to different heights permits accommodation or creation of lordosis. In another aspect and example, a benefit is an ability to achieve a gradual distraction. For example, if a height of a disc space is 7 mm and distraction to 11 mm is needed, a surgeon could gradually add wafers in 1 mm height increments to eventually get to the 11 mm height, as opposed to having to deploy a single height 11 mm cage and achieve 4 mm of distraction in one push. Moreover, by gradually stacking wafers the surgeon is able to press fit each construct to match the height of that particular portion of the disc, and can in the manner create or maintain lordosis, e.g. by deployment of more wafers in the anterior portion of a disc as compared to posterior portion of disc 
         [0091]    In still another aspect, with reference to  FIG. 3B  and  FIG. 4 , in some examples a trans-sacral spinal implant for insertion from an anterior target site on the surface of the sacrum into a disc space; the implant comprises a pair of semi-circular intervertebral cages configured from, for example, PEEK, that together form a cylindrical shape, the pair of semi-circular intervertebral cages being joined together by a spring configured, for example, from Nitinol. In some examples, two PEEK components that are connected by a flexible nitinol spring bend together to allow the spinal implant to fit through the inner diameter of a deployment cannula/insertion tool. Once the spinal implant emerges from the distal end of the cannula, the nitinol spring comprised as part of the spinal implant straightens out as it is deployed into the disc space, and the PEEK components serve to bear compressive loads, e.g., between the end plates. 
         [0092]    In still another aspect of the present disclosure, with reference to  FIG. 13 , a 2-piece expandable plug inserted into the sacral access bore (does not extend into disc space). In one aspect of the spinal implant system of the present disclosure, a PEEK plug is also implanted to lock the spinal cage deployed into a disc space and prevent it from migrating back out of an access channel. In another aspect and example, a plug such as depicted above may be used following a “soft fusion” procedure, e.g., where a discectomy is performed and the disc space is filled with bone graft/growth media, to prevent the graft material from “leaking” back out of the disc space. In another aspect and example, a plug is inserted following a revision surgery, for example, to remove a previously implanted AXIALIF® implant. In some examples, a trans-sacral spinal implant for insertion from an anterior target site on the surface of the sacrum into the sacrum comprises a first body having a leading end, a trailing end, a longitudinal axis through the leading and trailing ends, a length parallel to the longitudinal axis, and a sidewall surrounding the longitudinal axis and extending from the leading end to the trailing end, the first body having an interior surface and an opposite exterior surface; a first thread extending along the interior surface of the body and an exterior thread on the exterior surface of the first body; leading end of the first body including at least one slot extending from the leading end of the first body towards the trailing end; the at least one slot extending from the exterior surface to the interior surface; a second body having a leading end, a second and an exterior surface extending from the leading end to the trailing end, the exterior surface comprising an exterior thread that engages the interior thread of the first body; wherein threading the second body into the interior surface of the first body causes the leading end of the first body to radially expand. 
         [0093]    In yet another example, with reference to  FIG. 14 , a 1-piece, non-expanding plug comprises radio-opaque markers on or on a wall of a leading edge to facilitate device placement (e.g., using fluoroscopy) is used for the purposes as just described above for the 2-piece expanding plug (see also caption for  FIG. 13 ) and in one example, is fabricated from PEEK. In some examples, the device may comprise internal retention threads; a graft chamber; a “blind” hole in the leading end. 
         [0094]    In one aspect of the present disclosure, a trans-sacral spinal implant for insertion from an anterior target site on the surface of the sacrum into the sacrum comprises a first body having a leading end, a trailing end, a longitudinal axis through the leading and trailing ends, a length parallel to the longitudinal axis, and a sidewall surrounding the longitudinal axis and extending from the leading end to the trailing end, the first body having an interior surface and an opposite exterior surface; a first thread extending along the interior surface of the body and an exterior thread on the exterior surface of the first body; a second body having a leading end, a second and an exterior surface extending from the leading end to the trailing end, the exterior surface comprising an exterior thread that engages the interior thread of the first body 
         [0095]    In still another aspect and example, with reference to  FIG. 15 , a 1-piece threaded cage comprises (e.g., radial) windows or openings which carry bone graft material, and is configured to maximize the device&#39;s “L-5 footprint” for axial/compressive load support and distribution. In some examples, the threaded cage creates distraction according to the distance the cage is advanced distally, and with axial force from the sacral bone to the outer thread of the mechanical interface and the “L-5 footprint.” In some examples, a trans-sacral spinal implant for insertion from an anterior target site on the surface of the sacrum into the sacrum comprises a first body having a leading end, a trailing end, a longitudinal axis through the leading and trailing ends, a length parallel to the longitudinal axis, and a sidewall surrounding the longitudinal axis and extending from the leading end to the trailing end, the first body having an interior surface and an opposite exterior surface and an exterior thread on the exterior surface of the first body; the first body including at least one aperture extending from the exterior surface to the interior surface; the leading end of the first body forming a substantially flat distal surface that is substantially perpendicular to the exterior surface of the first body. In some examples, a spinal implant comprises an aperture on a radial surface and on a top/distal face. 
         [0096]    In another aspect and example, with reference to  FIG. 16 , a threaded spinal cage is configured as an expandable “flower,” e.g., with a plurality of “petals” at a distal end of the implant that spread as an internal metal plug comprised as part of the cage interfaces with and engages internal threads in the threaded cage, the device is advanced distally, up to but not into an inferior endplate of the L-5 vertebral body. Each petal bends at an approximate angle of 45° to maximize contact with L5 endplate. In a preferred example, the threaded cage comprises between two and six petals. In some examples, a threaded spinal cage with an expandable distal end is dimensioned with a major thread diameter range of between about 13 mm and about 15.5 mm and a length of between about 20 mm and about 40 mm. In some examples, a trans-sacral spinal implant for insertion from an anterior target site on the surface of the sacrum into the sacrum comprises a first body having a leading end, a trailing end, a longitudinal axis through the leading and trailing ends, a length parallel to the longitudinal axis, and a sidewall surrounding the longitudinal axis and extending from the leading end to the trailing end, the first body having an interior surface and an opposite exterior surface; a first thread extending along the interior surface of the body and an exterior thread on the exterior surface of the first body; leading end of the first body including at least one slot extending from the leading end of the first body towards the trailing end; the at least one slot extending from the exterior surface to the interior surface, the leading end forming substantially flat distal surface that is substantially perpendicular to the exterior surface of the first body; a second body having a leading end, a second and an exterior surface extending from the leading end to the trailing end, the exterior surface comprising an exterior thread that engages the interior thread of the first body; wherein threading the second body into the interior surface of the first body causes the leading end of the first body to radially expand. In some examples, the bend is approximately 45 degrees to deploy the petals beyond the radial footprint of the thread major (diameter). 
         [0097]    In yet another aspect and example, with reference to  FIG. 17 , a threaded cage is dimensioned and configured as a flower with petals as an example as described above, but the cage is also additionally configured for insertion into the L-5 endplate and vertebral body and comprises a different internal metal plug such that the distal tip of the metal plug comprises self-tapping bone threads. In some examples, the length of the metal bone threads for L-5 is between about 10 mm and about 25 mm. As a metal plug advances via internal threads in a flower cage it opens the flower “petals” and also begins engaging with the L5 vertebral body. Once the internal plug is fixated to L5 and the “petals” are open, it affords the benefits of rigid fixation between L5 and S1 (advantageous for spondylolisthesis biomechanics and bending resistance) as well as better resistance to subsidence because the open “petals” resist any cage migration up into L5. In some examples, a trans-sacral spinal implant for insertion from an anterior target site on the surface of the sacrum into the sacrum comprises a first body having a leading end, a trailing end, a longitudinal axis through the leading and trailing ends, a length parallel to the longitudinal axis, and a sidewall surrounding the e longitudinal axis and extending from the leading end to the trailing end, the first body having an interior surface and an opposite exterior surface; a first thread extending along the interior surface of the body and an exterior thread on the exterior surface of the first body; leading end of the first body including at least one slot extending from the leading end of the first body towards the trailing end; the at least one slot extending from the exterior surface to the interior surface, the leading end forming substantially flat distal surface that is substantially perpendicular to the exterior surface of the first body; a second body having a threaded leading end, a second and an exterior surface extending from the leading end to the trailing end, the exterior surface comprising a thread that engages the interior thread of the first body; wherein threading the second body into the interior surface of the first body causes the leading end of the first body to radially expand and for the threaded leading end to extend past the leading end of the first body. 
         [0098]    In yet another aspect and example, with reference to  FIG. 18 , a threaded cage configured as a flower with petals as described above additionally is configured to comprise Nitinol for the expandable joints to improve an ability of the threaded cage to withstand repeated loading cycles. In some examples, a segment of the device is configured with nitinol inserted between a PEEK threaded base and a PEEK “petal(s)”, such that advancement of an internal metal plug deflects the petals outward in such a manner that the nitinol joint bears the deflection and the load. 
         [0099]    In another aspect an example, with reference to  FIG. 19 , a mini-cage is configured to comprise an angled or wedge-shaped posterior portion, which enables the cage to be deployed into a disc space using an axial tool to push the wedge shape in the radial direction. This example has an added advantage in that the cage may be expanded, e.g., in situ, a modular manner to configure a larger device in a disc space of greater volume. 
         [0100]    In still another aspect and example, with reference to  FIG. 20 , a mini-cage is configured with a non-wedged posterior portion, and the cage is inserted by means of a cam tool that is then rotated to deploy the cage radially into a disc space. 
         [0101]    In yet another example, with reference to  FIG. 21 , a mini-cage is configured as an expandable device that in an expanded configuration distracts a disc space. An advantage of this configuration is that it allows for deployment of multiple devices of one initial height which are then variably adjustable within the disc space as needed, thereby accommodating lordosis. In one aspect, devices are provided in the non-expanded configuration in sizes (heights) of between about 5 mm and about 9 mm in increments of 1 mm, each with an ability to expand to about 1.5 times the height of the collapsed or non-expanded configuration. In another aspect, the diameter of the cage is configured to conform/be deployable through the inner diameter of the current axial access cannula being used, between about 9 mm and about 15 mm 
         [0102]    In another example, with reference to  FIGS. 22 and 23 , a mini-cage is configured as a hollow sphere with a plurality of exterior sides or surfaces, and may be fabricated from, for example PEEK, Allograft or an medical grade implantable metal or metal alloy. In another aspect, the interior of the hollow sphere can be filled with bone graft or an osteoconductive material to promote bone growth between vertebral bodies in the motion segment and also allow bone to grow into the pourous surface of the cage. An advantage of this example is that a plurality of cages of diameters between about 3 mm and about 17 mm may be deployed without regard to cage orientation or inserter position. Another advantage is that multiple cages of varying sizes may be deployed to create a wedge effect, which has utility as a lordosis therapy, for example, with the largest cage positioned in the anterior portion of the disc space and with progressively descending cage sizes deployed towards the posterior portion of the disc space. In another aspect and example, due to their geometries, the insertion of a plurality of spherical cages of varying diameters allows them to interlock and provide structural support to the disc. 
         [0103]    In still another example, with reference to  FIG. 24 , a mini-cage system comprises a plurality of connected devices, the shape of which is configured to facilitate deployment into the disc space as a single unit, progressively inserted/pushed out into the disc space. In some examples, an individual modular cage is connected to a neighboring cage by means of a flexible wire fabricated, for example, from nitinol or stainless steel. In another aspect and example, the flexible wire is able to be adjusted, e.g., tightened or slackened, following device deployment into the disc space. In one aspect, the diameter of the device ranges from between about 5 mm up to the diameter of the access bore drilled into the vertebral body into the disc space. In another aspect and example, a device diameter is determined by the (available) disc space height, and is further configured for ease of deployment from axial insertion to radial deployment 
         [0104]    In another example, with reference to  FIG. 25 , a spinal implant is configured to be an expandable, winged cage upon deployment, and comprises a first anchor portion and a second anchor portion at opposing distal and proximal ends of the cage, and an intermediate inner member that serves as a distraction device. In one aspect, the device is inserted in a first non-expanded/un-winged configuration, which upon compression of at least one of the anchors, the outer diameter of the anchor deforms, radially creating “wings” or flanges. In some examples, the implant may then be further expanded by rotating an inner member, e.g., by means of threads, to either engage a vertebral endplate, or upon further rotation and advancement, to distract the motion segment. In yet another example, also shown in  FIG. 25 , the winged cage is configured as a non-expanding, non-distraction device. 
         [0105]    Of course, the foregoing description is of certain features, aspects and advantages of the present invention, to which various changes and modifications can be made without departing from the spirit and scope of the present invention. Thus, for example, those of skill in the art will recognize that the invention can be embodied or carried out in a manner that achieves or optimizes one advantage or a group of advantages as taught herein without necessarily achieving other objects or advantages as can be taught or suggested herein. In addition, while a number of variations of the invention have been shown and described in detail, other modifications and methods of use, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is contemplated that various combinations or sub-combinations of the specific features and aspects between and among the different examples can be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed examples can be combined with or substituted for one another in order to form varying modes of the discussed devices, systems and methods (e.g., by excluding features or steps from certain examples, or adding features or steps from one example of a system or method to another example of a system or method). 
         [0106]    Component Details. 
         [0107]    Materials Choices 
         [0108]    Choices for material for use in the various components comprised in the constructs shown herein are machinable and medical grade, and include but are not limited to, e.g., machinable allograft, PEEK, titanium or titanium alloys, cobalt-chromium alloys, and stainless steel alloys, Nitinol, or combinations thereof. These biocompatible materials can withstand sterilization techniques such as Ethylene oxide (EtO) gas, radiation, steam autoclaving, dry heat, and cold sterilization. Other desirable attributes are that the material is able to be imaged, e.g., visible via fluoroscopy, X-ray and/or computed tomography (CT); dimensionally stable, and with sufficient biomechanical properties (strength, stiffness, toughness) for intended use, e.g., is sufficiently stiff to allow a relatively thin wall. If needed, materials may be used with incorporated visualization markers, e.g. tantalum, although other materials may be used. The selected material(s) may be able to undergo surface treatments, such as bead blasting to promote anti-slippage, or surface coating, e.g., with hydroxyapatite (HA), or roughening to promote bone in-growth. 
         [0109]    Provision of Therapy 
         [0110]    After creating access to the targeted spinal vertebra and/or discs, and aligning or stabilizing/fixing them using the methods as disclosed herein, additional therapy may be provided. One form of therapy is to fuse the selected spinal levels together. Spinal fusion typically involves the use of osteogenic, osteoconductive, or osteoinductive material (bone graft). One process to promote fusion is to insert quantities of one or more fusion promoting materials into the areas to be fused, or into openings in certain examples of the spinal cages described in the present disclosure. Bone graft is the material that is used to promote bone growth and forms the scaffold that bridges the adjacent vertebral bodies comprising a motion segment in the spine. The fused portions of the vertebrae do not move with respect to one another. It is useful to have one name for the variety of materials used to promote fusion. Thus, fusion promoting materials including osteogenic, osteoconductive, and/or osteoinductive material are collectively described herein as bone graft, whether the material is autograft or allograft and various bone graft substitutes or bone graft extenders. Various techniques for promoting effective fusion of adjacent vertebrae are well known to those of skill in the art so a minimal summary is sufficient for this document. The spinal cage devices of the present disclosure may be used in conjunction with bone graft types that are autologous or allogenic, e.g., grafts from the iliac crest, rib, or tibia/fibula donor sites. Autograft, a combination of autograft and allograft, or allograft alone may be used. 
       METHOD OF USE EXAMPLES 
       [0111]    While the particulars of the tools for deployment of the implants are briefly illustrated herein, a detailed description is beyond the focus of this Provisional application although the implant deployment tools (e.g., insertion tools; retention tools; extraction tools, and tools that may be used for both insertion and extraction) are contemplated As used herein in this disclosure and application, it will be understood that the terms insertion tool, retention tool and extraction tool are sometimes used interchangeably or collectively and refer to the movement and manipulation of a spinal implant of the present disclosure. Moreover, it will be understood that a tool may serve individual and/or multiple purposes. A brief outline of the intended method of use/deployment of certain devices of the present disclosure is provided below. 
       Example A 
     Mini-Cage with AXIALIF® 
       [0112]    Access and establish trajectory using dissector and beveled guide pin
       6 mm, 8 mm, 10 mm dilator and sheath   9 mm drill through sacrum   L5/S1 discectomy using AXIALIF® discectomy tools (insert initial graft material)   12 mm dilator and sheath   10.5 mm drill through sacrum       
 
         [0118]    Advance sheath opening to S1 endplate 
         [0119]    Deploy mini-cage(s) (All concepts) 
         [0120]    May deploy one or multiple cages (or cage constructs) in any radial direction (anterior, anterio-lateral, lateral, posterior) 
         [0121]    May deploy taller cage or cage construct in anterior direction for lordosis and shorter cage or cage construct posterior 
         [0122]    Cage may have lordotic angle to fit L5/S1 endplate angle 
         [0123]    Cage may have wedge design to self-distract disc space 
         [0124]    Dimensional ranges:
       Diameter for deployment through a tube=9 mm-15 mm (this would cover deployment 10 mm sheath up to tubular retractor); Height=7 mm-17 mm; Lordotic Angles—0°-10°       
 
         [0126]    Insert secondary graft material around cages if this was not done in step 4 
         [0127]    Continue with AXIALIF® procedure—Advance 12 mm sheath to L5 endplate 
         [0128]    Drill or dilate L5 endplate 
         [0129]    Measure 
         [0130]    Remove 12 mm sheath 
         [0131]    Exchange bushing and tubular retractor with fixation wires 
         [0132]    Insert AXIALIF 
         [0133]    Remove tools and close incision 
       Example B 
     Mini-Cage with Expanding Sacral Plug or Axial Threaded Cage 
       [0134]    Same steps as 1-9 in method described for Example A, above 
         [0135]    Measure sacral length for plug length 
         [0136]    Remove 12 mm sheath 
         [0137]    Exchange bushing and tubular retractor with fixation wires 
         [0138]    Insert Expanding Sacral Plug or Threaded Cage 
         [0139]    If Expanding Sacral Plug (PEEK):
       1. Insert until flush with superior S1 endplate (fluoroscopy marker on tip of plug will indicate)   2. Insert expansion arbor (metal), to expand plug and make it press fit inside of sacral bore. Expansion arbor engages internal threads of plug to push open the expanding “fingers” of the plug.       
 
         [0142]    If Axial Threaded Cage (Simple  1 -Piece PEEK)
       1. Pack threaded cage with graft material   2. Insert threaded cage until flush with inferior L5 endplate       
 
         [0145]    If Axial Threaded Cage (Flower Design with no fixation)
       1. Insert Flower cage with internal expansion plug inside until the cage is flush with the inferior L5 endplate.   2. Rotate the internal expansion plug until the “petals” of the flower expand radially. Expansion plug engages internal threads of flower cage to push open the expanding “petals” of the cage.   3. May need to drive the entire expanded flower up to make secure contact with inferior L5 endplate.       
 
         [0149]    If Axial Threaded Cage (Flower Design with fixation)
       1. Insert Flower cage with internal expanding fixation plug inside until the cage is flush with the inferior L5 endplate.   2. Rotate the internal expanding fixation plug until the “petals” of the flower expand radially and the bone threads of the expanding fixation plug self-tap into the L5 vertebral body. Expansion plug engages internal threads of flower cage to push open the expanding “petals” of the cage.   Remove tools and close incision       
 
       Example C 
     “Soft” Fusion* with Expanding Sacral Plug or Threaded Cage 
       [0153]    Access and establish trajectory using dissector and beveled guide pin
       6 mm, 8 mm, 10 mm dilator and sheath   9 mm drill through sacrum   L5/S1 discectomy using AXIALIF® discectomy tools (insert primary graft material)   12 mm dilator and sheath   10.5 mm drill through sacrum       
 
         [0159]    Advance 12 mm sheath to inferior L5 endplate using 12 mm tamp (packs bone radially) 
         [0160]    Measure sacral length for plug length 
         [0161]    Remove 12 mm sheath 
         [0162]    Exchange bushing and tubular retractor with fixation wires 
         [0163]    Insert Expanding Sacral Plug or Threaded Cage (See steps 5.1 through 5.4 in method in Example B, above) 
         [0164]    Remove tools and close incision
       Soft fusion is generally discectomy followed by insertion of bone graft/growth media without accompanying implant within disc space, and often in conjunction with posterior fixation and/or posterior fusion       
 
       Example D 
     Revision with Expanding Sacral Plug 
       [0166]    Access and establish a guide wire in the back the AXIALIF® implant 
         [0167]    Exchange bushing and tubular retractor with fixation wires 
         [0168]    Remove AXIALIF® implant 
         [0169]    Additional L5/S1 discectomy using AXIALIF® discectomy tools if desired 
         [0170]    Pack L5 void and disc space with more graft material 
         [0171]    Insert Expanding Sacral Plug 
         [0172]    Insert until flush with superior  51  endplate (fluoroscopy marker on tip of plug will indicate) 
         [0173]    Insert expansion arbor (metal), to expand plug and make it press fit inside of sacral bore. Expansion arbor engages internal threads of plug to push open the expanding “fingers” of the plug. 
         [0174]    Remove tools and close incision 
       Alternatives and Variations 
       [0175]    One of skill in the art will recognize that alternative variations may be contemplated for the examples presently disclosed that may achieve equivalence in intended function 
         [0176]    Multi-Level Surgery 
         [0177]    For convenience, the description set forth above provides therapy to stabilize vertebra or motion segment(s) via trans sacral access to the S1 sacral and L-5 lumbar levels however one of skill in the art will recognize that the process set forth above may applied to constructs so that more than one motion segment, in multiple spinal levels (e.g., L5-L4) may receive therapy (such as subsequent deployment of bone growth media and fusion) during a single surgical intervention. 
         [0178]    Kits 
         [0179]    One of skill in the art will recognize that the surgical procedures set forth above may benefit from various kits of tools and components for use in these procedures. Kits may focus on reusable or disposable components for creating an access route. Other kits may focus on the tools for preparing the targeted surgical site(s). A kit may include many (possibly even all) the components necessary for a particular procedure including the components needed to create the access route, prepare the targeted sites and even an assortment of implants, as well as the instruments needed for their deployment. 
         [0180]    One of skill in the art will recognize that some of the alternative implementations set forth above are not universally mutually exclusive and that in some cases additional implementations can be created that employ aspects of two or more of the variations described above. Likewise, the present disclosure is not limited to the specific examples or particular embodiments provided to promote understanding of the various teachings of the present disclosure. Moreover, the scope of the claims which follow covers the range of variations, modifications, and substitutes for the components described herein as would be known to those of skill in the art. Individual claims may be tailored to claim particular examples out of the array of examples disclosed above. Some claims may be tailored to claim alternative examples rather than preferred examples. Some claims may cover an embodiment set forth above with a modification from another example as the present disclosure does not include drawings of all possible combinations of feature sets. 
         [0181]    The legal limitations of the scope of the claimed invention are set forth in the claims that follow and extend to cover their legal equivalents. Those unfamiliar with the legal tests for equivalency should consult a person registered to practice before the patent authority which granted this patent such as the United States Patent and Trademark Office or its counterpart. 
         [0182]      FIG. 1  shows the various segments of a human spinal column as viewed from the side. 
         [0183]      FIGS. 2A &amp; 2B  show axial trans-sacral access to the lumbo-sacral spine, an example of a process of “walking” a blunt tip stylet  204  up the anterior face of the sacrum  116  to the desired position on the sacrum  116  while monitored on a fluoroscope (not shown).  FIG. 2C  illustrates a representative axial trans-sacral channel  212  established through the sacrum  116 , the L5/sacrum intervertebral space, the L5 vertebra  216 , the L4/L5 intervertebral space, and into the L4 vertebra  220 . 
         [0184]      FIGS. 3A &amp; 3B  show examples of representative mini-cages/spacers.  FIG. 3B  illustrates the concept of deployment of a (PEEK) “spring” implant comprising, e.g., a flexible Nitinol spring. The implant is deployed through a cannula (not shown) in a compressed or folded configuration, which device expands upon emergence from the distal end of (an axial channel) insertion tool and deployment (e.g., laterally/radially) into a disc space. 
         [0185]      FIG. 4  illustrates examples of mini-cages/spacers shown in  FIGS. 3A &amp; 3B , above deployed in conjunction with each other, at multiple spinal levels, and with an AXIALIF® implant. 
         [0186]      FIG. 5  illustrates a wedge system comprising a plurality of wedge components and a ramped insertion tool Note that the converging point of leading edge surfaces forms a “bullet nose”. 
         [0187]      FIG. 6  illustrates the stages of insertion of one example of a wedge system. 
         [0188]      FIG. 7  shows modular wedges inserted axially through wedge system cannula with ramp insertion tool and deployed laterally/radially in disc space. Note that more than one wedge construct/system may be delivered and deployed into the disc space, and including with or without an AXIALIF® implant or a sacral plug. 
         [0189]      FIG. 8  shows each wedge component can include a wedge protrusion and/or wedge slot where each slot and protrusion are configured to complement one another. 
         [0190]      FIGS. 9A-C  illustrate a plurality of wedge components and ramped insertion tool that may be cannulated and configured to receive a retention rod. 
         [0191]      FIG. 10 . illustrates a mini cage analog to cages used in TLIF procedures: a PEEK cage may be configured with “teeth” for gripping an endplate surface, as well as being configured in parallel (0 degree) and non-parallel (lordotic angles of about 0- to about 10 degrees) versions. In some examples, multiple cages may be deployed in any radial direction (anterior, anterio-lateral, lateral, posterior). 
         [0192]      FIG. 11  depicts a spinal implant that is arch or kidney-shaped to facilitate a 90° turn from axial access to lateral/radial deployment during insertion into the disc space. In some examples, the cage is wedged (shown at top). In another example, the cage has parallel opposing top and bottom surfaces. 
         [0193]      FIG. 12  shows stacks of multiple wafer-like implants which form constructs of varying heights to accommodate or create lordosis, and/or to achieve gradual distraction. 
         [0194]      FIG. 13  shows a 2-piece expandable plug inserted into the sacral access bore (does not extend into disc space). In one aspect of the spinal implant system of the present disclosure, a PEEK plug is also implanted to lock the spinal cage deployed into a disc space and prevent it from migrating back out of an access channel. In another aspect and example, a plug such as depicted above may be used following a “soft fusion” procedure, e.g., where a discectomy is performed and the disc space is filled with bone graft/growth media, to prevent the graft material from “leaking” back out of the disc space. In another aspect and example, a plug is inserted following a revision surgery, for example, to remove a previously implanted AXIALIF® implant. 
         [0195]      FIG. 14  shows a 1-piece, non-expanding plug. In some examples, a plug such as depicted above is used for purposes as described in  FIG. 13 , above, and also fabricated from PEEK. 
         [0196]      FIG. 15  illustrates a 1-piece threaded cage comprising windows which carry bone graft material, and configured to maximize the device&#39;s “L-5 footprint” for axial/compressive load support and distribution. 
         [0197]      FIG. 16  shows one example of a threaded spinal cage that is configured as an expandable “flower, e.g., with a plurality of “petals” at a distal end of the implant and shows it as it is spread as an internal metal plug comprised as part of the cage interfaces with and engages internal threads in the threaded cage, the device is advanced distally, up to but not into an inferior endplate of the L-5 vertebral body. 
         [0198]      FIG. 17  illustrates an example of a threaded cage configured as a flower with petals similar to  FIG. 16  above, but the cage is also additionally configured for insertion into L-5. 
         [0199]      FIG. 18  shows one example of threaded cage configured as a flower with petals additionally is configured to comprise Nitinol expandable joints to improve an ability of the threaded cage to withstand repeated loading cycles. 
         [0200]      FIG. 19  shows an example of a spinal cage configured with an angled or wedge-shaped posterior/back portion of the device. In one aspect, the device may be modularly extended, e.g., by means of in situ attachment of subsequent cages. 
         [0201]      FIG. 20  shows an example of a cage with a non-wedged back. In this aspect, insertion of the cage is by means of a cam tool that is rotated to deploy the device into a disc space. 
         [0202]      FIG. 21  shows a mini-cage example which is configured as an expandable device that in an expanded configuration distracts a disc space. 
         [0203]      FIGS. 22 &amp; 23  depict mini-cages based on, for example, a “bucky ball” concept in which a device is configured as a hollow sphere, the interior of which is filled with bone graft and the porous exterior is conducive to bone in-growth. 
         [0204]      FIG. 24  In some examples, an individual modular cage is connected to a neighboring cage by means of a flexible wire, the flexible connection coupling the cages. 
         [0205]      FIG. 25  shows examples of a spinal implant configured as/becomes an expanded, winged cage with radial flanges formed upon deployment. With reference to the upper row, in some examples, a “bullet nose” spinal implant with a rounded distal or leading end is compressed, forming flanges, then the implant is expanded to achieve distraction. In another example, a nonexpanded device is shown (lower right hand corner, last two examples, no intermediate waist portion). In some examples, a non-expanding winged cage is delivered, for example, though S1 and partially into L5. As the cage is collapsed or compressed, wings or flanges form that are then deployed radially and support the L5 vertebrae. The implant may then be advanced fully into L5. If distraction is needed the implant can be advanced through S1 as the radial wings push on L5. In some examples, a non distracting cage can also be inserted fully. As the cage is collapsed and wings deployed radially, the cage compresses the space. In one aspect, compression of the disc space assists in compressing the bone graft.