Abstract:
A system for accessing a spine from a curved postero-lateral approach may include a curved cannula positioned along a curved path from an opening in the skin to a location proximate the spine. A guide member may be first inserted to establish the path between the tissues and fascia, and one or more intermediate cannulas may be temporarily inserted over the guide member to dilate the tissues prior to insertion of the main cannula. An interbody device may be implanted in an intervertebral space through the cannula. The system may include a guide bar removably coupled to a targeting post. The targeting post may be inserted adjacent the spine to provide a target, and the guide bar may be removably attached to the guide member, to guide it along the path to the target location. An external support arm may be secured to any other component of the system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/856,682, filed Nov. 3, 2006, which is entitled METHOD AND APPARATUS FOR SPINAL SURGERY. 
    
    
     BACKGROUND OF THE INVENTION 
     1. The Field of the Invention 
     The invention relates to orthopaedics, and more particularly, to systems and methods for providing access to the spine to facilitate various implantation procedures. 
     2. The Relevant Technology 
     Many spinal orthopaedic procedures including discectomy, implantation of motion preservation devices, total disk replacement, and implantation of interbody devices require unimpeded access to a targeted portion of the spinal column. A lateral interbody fusion approach requires the patient to be turned mid-process to complete the disc and interbody device procedures. An anterior approach requires the presence of a vascular surgeon or highly experienced general surgeon, due to the risk of injury to vascular anatomy. Accordingly, there is a need in the art for systems and methods that facilitate access to the spine, thereby simplifying surgical procedures and expediting patient recovery. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the present invention will now be discussed with reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. 
         FIG. 1  is a cephalad view of a cross-section of a portion of a patient with an arcuate cannula assembly deployed adjacent a portion of the spine; 
         FIG. 2  is a perspective view of a targeting post of the arcuate cannula assembly of  FIG. 1 ; 
         FIG. 3  is a perspective view of a portion of an instrument support arm; 
         FIG. 4  is a perspective view of the instrument support arm of  FIG. 3  supporting the targeting post of  FIG. 2  adjacent a portion of a spine; 
         FIG. 5  is a perspective view of a guide member of the arcuate cannula assembly of  FIG. 1 ; 
         FIG. 6A  is a perspective view of a guide arm of the arcuate cannula assembly of  FIG. 1 ; 
         FIG. 6B  is a perspective view of a sliding latch bar of the guide arm of  FIG. 6A ; 
         FIG. 7  is a perspective view of a latch assembly of  FIG. 6A , with the guide member of  FIG. 5  latched thereto; 
         FIG. 8  is a perspective view of the arcuate cannula assembly of  FIG. 1  with the guide arm in a first position, adjacent a portion of the spine; 
         FIG. 9  is a perspective view of the arcuate cannula assembly of  FIG. 1  with the guide arm in a second position, adjacent a portion of the spine; 
         FIG. 10  is a perspective view of a cannula; 
         FIG. 11  is a perspective view of the arcuate cannula assembly of  FIG. 1  with the guide arm removed and several cannulas added, adjacent a portion of the spine; 
         FIG. 12  is a postero-lateral perspective view of a cannula of  FIG. 10  adjacent a portion of the spine; 
         FIG. 13  is a perspective view of an arcuate cannula assembly with an adjustable targeting post; 
         FIG. 14  is a perspective view of two arcuate cannula assemblies of  FIG. 1 , adjacent two lateral sides of a portion of the spine; 
         FIG. 15A  is an antero-lateral perspective view of the cannula of  FIG. 10  adjacent a portion of a spine, and an interbody device in an intervertebral space; and 
         FIG. 15B  is a perspective view of the interbody device of  FIG. 15A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention relates to systems and methods for accessing intervertebral space and inserting spine implants between vertebral bodies. Those of skill in the art will recognize that the following description is merely illustrative of the principles of the invention, which may be applied in various ways to provide many different alternative embodiments. This description is made for the purpose of illustrating the general principles of this invention and is not meant to limit the inventive concepts in the appended claims. 
     The present invention provides access to the spine through the use of a postero-lateral approach. A minimally invasive dilation and/or access device employing such an approach would have significant advantages in spinal orthopaedic procedures over the lateral and anterior approaches. These advantages may include avoiding the need to turn the patient during surgery, less muscle retraction, less blood loss, less operating room time, minimized damage to the vascular system, organs, nerves and muscles, faster recovery, and an improved overall outcome for the patient. 
     Referring to  FIG. 1 , one embodiment of an arcuate cannula assembly  10  is shown. The assembly  10  comprises a targeting post  12 , a guide arm  14 , and a curved penetrating guide member  16 . An instrument support arm  20  holds the assembly and connects to an operating table (not shown). The assembly  10  may further comprise a series of graduated curved cannulas (shown in  FIG. 11 ), which are introduced sequentially over the guide member  16  to create access to a targeted portion of a spine. Use of the arcuate cannula assembly  10  creates an access portal to the intervertebral disc space or any element of the anterior spinal column through an arcuate path, from a postero-lateral approach. The access portal is an unimpeded passage through which surgical instruments, implants and other materials may be passed to complete a variety of intervertebral procedures. This arcuate postero-lateral approach may be advantageous in performing a number of procedures, including but not limited to: implantation of motion preservation devices, total disk replacement, implantation of interbody devices, discectomy, lateral plating with or without dynamic elements, vertebra fixation or graft compression using plates or staples, foraminotomy, decompression, annulotomy, nucleotomy, annulus or nucleus repair, vertebral body biopsy, vertebroplasty, height restoration of a collapsed vertebral body (vertebral body augmentation), implantation of a fusion cage with stabilization features, implantation of a fusion cage with teeth to hold endplates together, or implantation of a curved or straight staple across the disc space to provide compression on the cage and stabilization of the cage. 
     Referring to  FIG. 2 , a perspective view of the targeting post  12  is shown. The targeting post  12  comprises an elongate shaft  30  with a distal end  32  and a proximal end  34 . A rounded tip  36  is at the terminus of the distal end  32 . The proximal end  34  adjoins a rectangular connector block  38  which has a first side  42  and a second side  43 . Adjoining the connector block  38  on the first side  42  is a support arm attachment post  44 . The attachment post  44  has a receiving slot  46  which extends transversely into the attachment post through an interface surface  45 . In the preferred embodiment the receiving slot  46  includes an internally threaded surface. A radial spline  48  encircles the receiving slot  46  on the interface surface  45 . Adjoining the connector block  38  on the second side  43  is a rotation post  50 . Extending distally from the rotation post  50  is an optional stop feature  52 . 
     Referring to  FIG. 3 , a perspective view of a support arm  20  is shown. The support arm  20  comprises a shaft  60  which attaches to the operating table via various linkages, pivots, or connections to allow multiple degrees of freedom to accommodate the positioning of the instrument to be held. A wide variety of differently-configured instrument support arms are well known in the art and the assembly  10  may be compatible with the instrument support arm of choice for the surgeon. 
     A distal end  61  of the shaft  60  has a first side  62  and a second side  63 . Extending transversely through the distal end  61  from the first side  62  to the second side  63  is a screw channel  66 . On the first side  62 , an interface surface  65  has a radial spline  64  which encircles the opening of the screw channel  66 . The radial spline  64  is configured to mate with the radial spline  48  on the targeting post  12  when the post is connected to the support arm  20 . Extending through the channel  66  is a thumb screw  68 , and a shaft  70  protrudes from the channel  66  on the second side  63 . In the preferred embodiment, shaft  70  includes an externally threaded surface configured to interface with the threaded receiving slot  46  on the targeting post  12 . 
     Referring to  FIG. 4 , the targeting post  12  is introduced into the patient from a postero-lateral approach through a small incision on the patient&#39;s back posterior to the targeted spine segment. The distal end  32  of the targeting post  12  is advanced antero-medially through the patient just lateral to the targeted intervertebral disc until the tip  36  reaches a desired reference location at the anterior lateral half or one third of the disc. The blunt shape of the tip  36  gently pushes tissues aside as the post  12  is advanced in. The post  12  may also be wired as an electrode during insertion, allowing for nerve monitoring or electromyography (EMG) to avoid nerves as the post  12  advances through the tissues. Of special concern is avoidance of the nerve roots exiting the spinal column as the psoas muscle adjacent to the spine is penetrated by the post  12 . The targeting post  12  is inserted so that it is coplanar with the superior endplate of the inferior vertebral body for the intervertebral level to be treated. Preferably, the post  12  is aligned parallel with the sagittal plane of the patient, but other orientations are possible if necessary to avoid nerves or other obstacles. 
     When the distal end  32  of the targeting post  12  has reached the reference location, the proximal end  30  is attached to the support arm  20  via the thumb screw  68 . The protruding screw shaft  70  is threaded into the receiving slot  46 . As the thumb screw  68  is threaded in, the radial splines  44 ,  64  mesh, locking the targeting post  12  to the support arm  20 . Once attachment is made between the targeting post  12  and the support arm  20 , the various degrees of freedom of the support arm  20  are locked down to provide sufficiently rigid instrument stabilization. In position adjacent to the spine, the targeting post  12  acts as a stabilizing and reference guide for subsequent cannulas, instruments and implants. 
     Referring to  FIG. 5 , the penetrating guide member  16  is shown. The guide member  16  is curved and may be arcuate (i.e., may extend along a fixed radius of curvature). The guide member  16  has a proximal end  110 , and a distal end  112  with an insertion tip  113 . The insertion tip  113  may be rounded or optionally pointed, to penetrate muscles and fascia. Two attachment recesses  114  at the proximal end facilitate attaching the guide member  16  to the guide arm  14 , and are also configured to connect to an instrument support arm. A narrow channel may optionally extend the length of the guide member  16 , sized to receive a wire for nerve monitoring or EMG during dilation. 
     Referring to  FIG. 6A , a perspective view of the guide arm  14  is shown. The guide arm  14  has a first side  80  and a second side  82 . At a proximal end is a pinned end  84 ; a latch end  86  is at the opposite distal end. The pinned end  84  has an attachment feature  88  which is shaped to rotatably attach to the rotation post  50  on the targeting post  12 . Inserted into a horizontal slot  89  in the latch end  86  is a spring loaded guide member latch assembly  90  which is shaped to grip the penetrating guide member  16 . The guide member latch assembly  90  has a sliding latch bar  92  with a keyhole  94  and a tab  96 . On the first side  80  of the guide arm  14 , near the latch end  86  is a round guide member opening  100 . Directly opposite it on the second side  82  may optionally be a smaller pinhole opening  102 . 
       FIG. 6B  is an enlarged view of the sliding latch bar  92 . Keyhole  94  has a rounded lobe  95  disposed toward the tab  96 , and an ovoid lobe  97  opposite the tab  96 . The rounded lobe  95  is sized to fit around the proximal end  110  of the guide member  16 . The ovoid lobe  97  is sized to hold the attachment recesses  114  of the guide member  16 . The tab  96  may be grasped to move the sliding latch bar  92  within the horizontal slot  89 . A spring (not shown) is disposed in the horizontal slot  89  to provide resistance against the sliding latch bar  92 . 
       FIG. 7  is an enlarged view of the latch end  86  of the guide arm  14 , showing the guide member  16  latched in the latch assembly  90 . To latch the guide member  16  in the latch assembly  90 , first the sliding latch bar  92  is introduced into the horizontal slot  89  until the rounded lobe  95  of the keyhole  94  lines up with the guide member opening  100 . The proximal end  110  of the guide member  16  is inserted such that the attachment recesses  114  are adjacent to the lined up keyhole  94  and opening  100 . The sliding latch bar  92  is released, and the spring (not shown) pushes the sliding latch bar  92  distally until the ovoid lobe  97  of the keyhole  94  slides around the attachment recesses  114  of the guide member  16 . The force of the spring traps the guide member  16  in the latch assembly  90 , as the guide member is pinned between the ovoid lobe  97  and the latch end  86  of the guide bar  14  adjacent the guide member opening  100 . 
     Referring to  FIG. 8 , the support arm  20 , targeting post  12 , guide arm  14  and penetrating guide member  16  are shown, with the guide arm  14  and penetrating guide member  16  in a first position. The attachment feature  88  on the guide arm  14  is engaged with the rotation post  50  on the targeting post  12 . Thus attached, the guide arm  14  can rotate about the axis of the rotation post  50 ; however the stop feature  52  on the rotation post  50  may prevent the guide arm  14  from rotating entirely about the rotation post  50 . The guide arm  14  is sized to match the radius of the curve of the penetrating guide member  16 , such that the arc centerpoint of the penetrating guide member  16  is coincident with the center of rotation, or axis of the rotation post  50 . The guide member latch  90  holds the penetrating guide member  16  as seen in  FIG. 7 . 
     After the penetrating guide member  16  is attached to the guide arm  14 , the guide arm  14  is rotated so that the insertion tip  113  of the guide member  16  makes contact with the skin. At this point, the guide member  16  is lifted and an incision of approximately 1-5 cm is made into the skin and fascia. As shown in  FIG. 9 , the guide member  16  is then advanced into the incision via rotation of the guide arm  14 . The guide member penetrates the soft tissues and fascia of the patient, and is advanced antero-medially along an arcuate path until the insertion tip  113  is at the lateral margin of the targeted disc, at a target location. The target location is at a known position relative to the reference location provided by the distal end  32  of the targeting post  12 , as the guide bar  14  holds the guide member  16  in a fixed relationship as the guide bar  14  rotates about the rotation post  50 . At this point the guide arm and guide member are in a second position. The guide member  16  may have a rounded insertion tip, or a sharp, pointed insertion tip if necessary to penetrate the tissues. EMG monitoring may be used to ensure safe passage of the guide member through the fascia. The optional pinhole opening  102  creates access for a wire to pass through the guide arm into the guide member  16  if it is desirable to connect an electrode to the guide member  16  for nerve monitoring. The stop feature  52  (seen in  FIG. 2 ) stops rotation of the guide arm  14  and prevents the guide member  16  from extending past the margin of the disc and contacting the spinal cord. 
     Once the guide member  16  is correctly positioned adjacent the targeted location, the guide arm  14  is detached from the guide member  16  and the targeting post  12 . The guide member  16  is left in the patient to serve as a guide for one cannula or series of cannulas which are graduated in size, and which are inserted sequentially from smaller to larger to increase the cross-sectional area of the access portal to the area to be treated. 
     Referring to  FIG. 10 , a single cannula  18  is shown. The cannula  18  is curved and generally tubular in form, with a tubular support wall  128  which has an open distal end  122  and an open proximal end  124 . The distal end  122  is rounded so that tissues are pushed aside gently as the cannula is inserted through the patient. A bore  130  runs the length of the cannula  18  from the open distal end  122  to the open proximal end  123 , and provides access to the targeted spinal area for instrument insertion, and insertion and removal of interbody devices, arthroscopic devices, implants, bone graft materials, bone cement, and other materials and devices. A cross-sectional shape of the support wall  128  of the bore  130  is generally curved, and may specifically be round, oval, elliptical or another curved shape. The open proximal end  123  has a plurality of grip features  126  which allow the surgeon to grip the cannula. Optionally, the cannula  18  may have attachment features to allow attachment of the cannula to the instrument support arm. The cannula  18  may optionally be substantially radiolucent, and can comprise biocompatible polymers, elastomers, ceramics, or aluminum or other metals. The curve of the cannula  18  may be arcuate, and may sweep through an angle of about 90° such that the open proximal and distal ends  124 ,  122  are substantially perpendicular to each other. 
     Referring to  FIG. 11 , a series of graduated cannulas  15 ,  17 ,  18  are inserted one at a time over the proximal end  110  of the penetrating guide member  16 , and advanced antero-medially over the guide member  16  until the corresponding distal end reaches the distal end  112  of the guide member  16 . Each cannula  17 ,  18  is shorter in length and larger in cross-sectional area than the next smallest cannula, to allow the surgeon to grip each cannula as it is installed and removed. As each cannula  15 ,  17 ,  18  is inserted, the access portal through the soft tissues and fascia is increased in size, creating increased access to the targeted portion of the spine. The number of cannulas inserted is determined by the desired cross-sectional area of the opening to the spine; in many instances two to five cannulas will be inserted. Once all cannulas  15 ,  17 ,  18  are inserted around the penetrating guide member  16 , the guide member  16  and the inner cannulas  15 ,  17  are removed, leaving the largest cannula  18  in the patient. This cannula may be attached via an attachment feature (not shown) to the support arm  20 , to provide additional stabilization for removal of the smaller cannulas, and for subsequent instrument insertion and procedures. 
     In one embodiment of the invention, the largest cannula  18  may have a tooth portion (not shown) which extends longitudinally from the insertion end  122 . During insertion, the tooth portion is placed between the superior and inferior endplates of the intervertebral space, to assist in maintaining access to the space. 
       FIG. 12  is a postero-lateral view of a portion of a spine with a cannula inserted according to the procedure previously described. When in place in the patient, the bore  130  of the cannula  18  is an access portal through which surgical instruments, implants and other materials may be passed to complete a variety of intervertebral procedures. Surgical instruments used in conjunction with the cannula  18  may have rigid, curved shafts or flexible shafts to navigate through the cannula  18  to the intervertebral space. The cannula  18  may be sized to accommodate passage of an interbody fusion implant  300  (shown in  FIGS. 15A and 15B ). 
     Another embodiment of the invention comprises a targeting post which is capable of cephalad-caudal adjustment.  FIG. 13  is a perspective view of an arcuate cannula assembly  210  which includes an adjustable targeting post  212 , a guide arm  214  and a penetrating guide member  16 . The adjustable targeting post  212  has a shaft  230  which has a distal end  232  and a proximal end  234 . Proximally adjacent to the proximal end  234  of the shaft  230  is a connection portion  240 , which extends in a cephalad-caudal direction and comprises a guide arm connector  250 , a cephalad-caudal adjustment feature  238 , and a support arm attachment post  244 . The cephalad-caudal adjustment feature  238  can be adjusted to lengthen or shorten the cephalad-caudal length of the connection portion  240 . Thus, after the targeting post is inserted into the patient, the length of the connection portion  240  can be adjusted as necessary to attain the necessary offset to adjust the resultant cephalad-caudal distance between the guide member  16  and the targeting post  212 . The adjustment allows the target location to vary along the cephalad-caudal direction such that the known position of the target location is offset relative to the reference location. Cephalad-caudal offset of the guide arm  214  and the attached guide member  16  may be useful in avoidance of nerve structures and other objects during the dilation process. 
     Another application of the invention comprises a bilateral implementation of two arcuate cannula assemblies. In this embodiment, two assemblies  10  are used together, one on each lateral side of the spine. Referring to  FIG. 14 , portions of two assemblies  10 , which comprise two targeting posts  12 , two penetrating guide members  16 , and two cannulas  18 , are shown adjacent to each lateral side of the spine. This embodiment permits enhanced access to the targeted area, since access may be attained from both lateral sides simultaneously. Instruments, implants, or other materials may be pushed or pulled into the intervertebral space, or through the entire access pathway. 
     Another embodiment of the invention further comprises an interbody device.  FIG. 15A  is an anterior perspective view of a portion of a spine with a cannula  18  and an interbody device  300  which may be inserted through the arcuate cannula assembly previously disclosed.  FIG. 15B  is a perspective view of the interbody device  300  of  FIG. 15A . The interbody device  300  has a generally rectangular box-like shape, and is slightly curved along its longitudinal axis. The interbody device  300  may optionally have a radius of curvature substantially the same as that of the cannula  18 . 
     In any case, the bore  130  of the cannula  18  is sized to accommodate passage of the interbody device  300 . Because use of the arcuate cannula assembly  10  allows improved access to the intervertebral space, the interbody device  300  may have a larger footprint than many other interbody devices, and can extend across most of the medial-lateral width of the intervertebral space, to provide for increased stability, increased bone in-growth, and improved fusion. A curved insertion tool and curved tamp (not shown) are used to insert and seat the interbody device  300  in the intervertebral space. In the alternative, a flexible insertion tool and/or a flexible tamp may be used. 
     The arcuate postero-lateral approach described above may have many advantages for spinal procedures, particularly procedures involving anterior vertebral column elements. This approach may be used to insert motion preservation devices, such as total disc replacements. By accessing the disc space via an arcuate postero-lateral approach, the surgeon is able to spare the anterior longitudinal ligament as well as avoid complications with the great vessels. This approach also provides for revision options with virtually the same instrumentation and implant designs by accessing the disc space from the opposite lateral side as the first surgery. This approach also allows for total disc replacement (TDR) endplate retention features which are more desirable than anterior approach TDR features, such as endplate keels or teeth which are oriented in the frontal plane to resist the high shear loads seen in the lumber spine lordotic region. 
     This approach may also be used for various intervertebral disc treatment or resection procedures such as annulotomy, nucleotomy, discectomy, annulus replacement, nucleus replacement, and decompression due to a bulging or extruded disc. During an annulotomy, the surgeon may provide an access portal in the manner described previously, and open and/or remove a portion or all of the disc annulus. During a nucleotomy, the surgeon may provide an access portal in the manner described previously, and open and/or resect a portion of the intervertebral disc nucleus. During a discectomy, the surgeon may remove a portion or the entire intervertebral disc through the access portal in order to accomplish decompression of the nerve roots, dura, or spinal cord. This procedure may be done as a conservative therapy to relieve patient symptoms or pain, or it may be done in preparation for total disc replacement or fusion. 
     For annulus repair or replacement, the arcuate postero-lateral approach may facilitate a larger needle and avoidance of complicated vascular structure and may allow a pathway for a prosthetic annulus to be placed or formed in the intervertebral space. Using a bilateral arcuate approach such as that depicted in  FIG. 14  could further facilitate the creation of bounding elements, such as a shield, guard, mold, or equivalent such that the annulus may be repaired, formed, inserted, created, or augmented. Similar benefits are realized for a nucleus replacement procedure where all or a portion of the intervertebral nucleus is repaired or resected and replaced, created or augmented via various techniques. A prosthetic nucleus may be delivered via a passageway that is larger than that afforded by a transpedicular approach, and less complicated and less risky than an anterior approach, by using the arcuate postero-lateral approach described above. Various intervertebral disc treatment methods have been postulated, such as using electrosurgical therapies. It is readily apparent to one of skill in the art how conducting these therapies via an arcuate postero-lateral approach may benefit the surgeon as well as improve clinical outcomes. 
     The arcuate postero-lateral approach may also be utilized for additional vertebral body motion segment stabilization procedures such as interbody device insertion, lateral plating, anterior plating, lateral or anterior plating with dynamic stabilization or compression elements, deformity correction, and/or graft compression devices or procedures. The arcuate postero-lateral access portal such as that depicted in  FIG. 15A  may facilitate interbody fusion procedures by allowing a single surgical exposure or patient positioning to insert all required stabilization elements such as an interbody fusion device similar to that depicted in  FIG. 15B , or posterior stabilization hardware such as pedicle screws, rods, hooks, and facet screws, among others. By approaching the intervertebral disc space with a tangential or almost straight medial-lateral trajectory right next to the vertebral body, the interbody device may more fully occupy the intervertebral space. This may result in a multitude of advantages such a leveraging the higher strength cortical regions on the vertebral body endplates, allowing more cross-sectional surface area or a larger footprint for improved stability, allowing more bone graft surface are to encourage better osteointegration, bony fusion, and 360° fusion. The interbody device may also comprise a lordotic angle which does not require over-distraction such as is the case with transforaminal lumbar interbody fusion (TLIF) and posterior lumbar interbody fusion (PLIF) procedures. 
     The arcuate postero-lateral approach may also be used for lateral plating procedures, in which the implanted plates may comprise fixed, dynamic, or compressive elements. This approach again allows a single patient positioning to conduct lateral plating as well as posterior stabilization hardware such as screws, hooks and rods. These plates may be used for local deformity correction or prevention procedures to treat local scoliosis, kyphosis, hyper-lordosis, or spondylolisthesis. Additionally, the arcuate postero-lateral approach may allow for novel graft compression devices or procedures that enable the surgeon to apply improved local compressive forces between vertebral bodies or an interbody device. Benefits of improved local compressive forces include improved bone graft incorporation, fusion, interbody device stability, as well as a potentially reduced risk of interbody device expulsion that is often the result of over-compressing the disc space and applying unintended moments via traditional pedicle screws and rods. Such graft compression devices include lateral plates with compression features, vertebral body staples which cooperate with the superior and inferior vertebral bodies to apply compression, and integrated interbody device with arms that cooperate with the vertebral bodies to apply compression via screws, tapered surfaces, or the like. 
     Various central canal or foraminal decompression procedures may be performed with the arcuate postero-lateral approach described previously. Decompression procedures are conducted to resect soft or hard tissues that may be impinging on neural elements such as the exiting nerve roots, dura, or spinal cord, resulting in various pathologies such as radiolopathy, myelopathy, pain, tingling, numbness, and loss of motor or sensory control. For example, anterior central canal decompression required due to a diseased intervertebral disc is often a difficult procedure. By using the disclosed arcuate postero-lateral approach, this decompression procedure allows for improved patient positioning, access, and patient outcomes. Foraminal decompression procedures via an arcuate postero-lateral approach may also allow the surgeon an improved trajectory and passageway to decompress the foramen. 
     Procedures involving the vertebral body, such as vertebral body biopsy, vertebral body height restoration, and vertebroplasty may successfully utilize the arcuate postero-lateral approach. Often patients who are experiencing symptoms associated with vertebral body disease, collapse, or fracture will undergo a biopsy of the vertebral body to assess the condition of the structure. Osteoporotic patients, especially female geriatric patients, may experience vertebral body collapse or fracture. This is an extremely painful and debilitating condition which may be addressed via vertebroplasty through the disclosed arcuate postero-lateral approach. Often, vertebroplasty, kyphoplasty or arcuplasty procedures are conducted via a transpedicular approach, to inject a hardenable compound such as PMMA cement into the vertebral body to create an internal cast-like structure to stabilize the bony fragments or fractures. The arcuate postero-lateral approach has numerous advantages for such a procedure. It may allow for a larger access needle than a transpedicular approach and accordingly reduces pressure requirements for the viscous hardenable compounds. In addition, it will likely result in less post-operative pain due to not violating the pedicle, and it allows for a more preferable trajectory of the access needle. Vertebroplasties conducted via a transpedicular approach often require a bilateral approach for sufficient vertebral body stabilization. By using the trajectory of the arcuate postero-lateral approach, the surgeon or radiologist may use a single needle and single approach for a complete fill, because the access needle can be advanced to the distal portions and gradually retracted during injection to accomplish a complete fill. 
     Vertebral body height restoration procedures have recently been disclosed in the art to address collapsed vertebral bodies. The arcuate postero-lateral approach may facilitate such vertebral height restoration procedures by removing the size limitation imposed by the transpedicular approach. Additionally, the ability to access the lateral margins of the vertebral body may be beneficial in insertion of an implant to restore vertebral height and fix it in place via a hardenable compound, or conduct an internal vertebral body distraction and secure the vertebral body via a hardenable compound. 
     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, above are described various alternative examples of systems for accessing intervertebral space. It is appreciated that various features of the above-described examples can be mixed and matched to form a variety of other alternatives. It is also appreciated that this system should not be limited creating access to the intervertebral space. This arcuate access system may be used to obtain access to any portion of the spine. As such, the described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.