Patent Publication Number: US-8523876-B2

Title: Systems and methods for compressing and distracting vertebrae of the spinal column

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a division of U.S. patent application Ser. No. 12/706,150, filed on Feb. 16, 2010, now allowed, which is a division of application Ser. No. 10/885,265, filed on Jul. 6, 2004, issued as U.S. Pat. No. 7,686,814. Each of the referenced applications being incorporated by reference herein in their respective entirety. 
    
    
     BACKGROUND 
     Orthopedic devices such as spinal rods, plates, tethers, staples and other devices can be secured along the spinal column between one or more vertebral levels to stabilize the one or more vertebral levels. While surgical procedures along the spinal column for placement of such devices are becoming less invasive, the decrease in space available in the approach to the surgical site and at the surgical site for handling and manipulating of the devices increases the difficulty in maneuvering, maintaining and finally positioning of the devices during the procedure. Furthermore, the ability to manipulate the vertebrae of the spinal column by compressing or distracting the vertebrae before attachment of the orthopedic devices is hindered by the construct attached to the vertebrae, the complexity and size of the footprint of the instruments involved in delivering the compression or distraction forces, the desire to maintain a minimally invasive approach to the spinal column, the vital anatomical structures adjacent the surgical site, and other factors. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a view of a compression system positioned through a portal and mounted to a construct engaged to the spinal column. 
         FIG. 2  is a top view of the portal and construct of  FIG. 1  showing a compressor of the compression system inserted through the portal and mounted to an anchor. 
         FIG. 3  is a view of the portal, construct and compressor of  FIG. 2  with a fulcrum being positioned through the compressor. 
         FIG. 4  is a view showing the compressor and fulcrum in the portal and mounted to the construct before compression of the spinal column. 
         FIG. 5  is a view showing engagement of the distal portions of the compressor and fulcrum mounted with the construct before compression of the spinal column. 
         FIG. 6  is ad view showing engagement of the distal portions of the compressor and fulcrum mounted with the construct after compression of the spinal column. 
         FIG. 7  is a view of the portal and another embodiment construct engaged to the spinal column. 
         FIG. 8  is a view showing another embodiment compressor being positioned through the portal for mounting with the construct of  FIG. 7 . 
         FIG. 9  is a view showing another embodiment fulcrum being positioned through the portal and compressor for mounting with the construct of  FIG. 7 . 
         FIG. 10  is a view showing the compressor and fulcrum through the portal mounted to the construct of  FIG. 7 . 
         FIG. 11  is a top view showing the compressor and fulcrum through the portal and mounted to the construct of  FIG. 7 . 
         FIG. 12  is a view showing the compressor and fulcrum through the portal and mounted to the construct of  FIG. 7  before compression of the spinal column. 
         FIG. 13  is a view showing the compressor and fulcrum through the portal and mounted to the construct of  FIG. 7  after compression of the spinal column. 
         FIG. 14  is a view of the construct of  FIG. 7  and the distal portions of the fulcrum and compressor-mounted thereto after compression of the spinal column. 
         FIG. 15  is a perspective view of a distractor. 
         FIG. 16  is a view of a distal portion of the distractor. 
         FIG. 17  is a view of a portal and a construct engaged along the spinal column. 
         FIG. 18  is a view of a fulcrum mounted to the construct of  FIG. 17  through the portal. 
         FIG. 19  is a view of the distractor and fulcrum through the portal mounted to the construct of  FIG. 17 . 
         FIG. 20  is a view of the distal portions of the distractor and fulcrum mounted to the construct of  FIG. 17  before distraction of the spinal column. 
         FIG. 21  is a view of the distractor and fulcrum through the portal mounted to the construct of  FIG. 17  after distraction of the spinal column. 
         FIG. 22  is an enlarged view of the distal portions of the distractor and fulcrum mounted to the construct after distraction of the spinal column. 
     
    
    
     DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any such alterations and further modifications in the illustrated devices and described methods, and any such further applications of the principles of the invention as illustrated herein are contemplated as would normally occur to one skilled in the art to which the invention relates. 
     Systems for applying compression and distraction to vertebrae of the spinal column include, in one embodiment, a compressor mountable to a first vertebra and a fulcrum mountable to a second vertebra. The compressor includes an elongated body having an intermediate opening to receive an elongated shaft of the fulcrum therethrough such that when assembled the compressor and fulcrum have a nested configuration where their longitudinal axis cross one another at a location between their distal and proximal ends. Compression of the vertebrae is performed by moving the proximal ends of the compressor and fulcrum toward one another, which moves the distal ends of the compressor and fulcrum toward one another. The body of the compressor contacts the shaft of the fulcrum along a leverage surface adjacent the opening of the compressor, allowing the compressor to be leveraged with the fulcrum. 
     In another embodiment, a system includes an elongated compressor and an elongated fulcrum, which are positionable independently of one another through an operative approach to first and second vertebrae. The fulcrum and compressor are mountable to respective ones of the first and second vertebrae. The compressor and fulcrum are configured to nest with one another so that the compressor can be leveraged with the fulcrum to deliver a compression force between the first and second vertebrae. 
     In another embodiment, a system includes a distractor having an elongated body with a distal end mountable to a first vertebra, and a fulcrum having an elongated shaft with a distal end mountable to a second vertebra. The distractor includes a proximal handle portion and distal portion that is angled relative to the proximal portion away from the fulcrum when each is mounted to the respective vertebra. The distractor includes a leverage surface between the proximal handle portion and the distal angled portion that is positionable against the fulcrum such that at least the proximal ends of the distractor and fulcrum are separated from one another. The proximal ends of the distractor and fulcrum are moveable toward one another to move the distal ends of the distractor and fulcrum away from one another to distract the vertebrae. A mechanical advantage is provided by leveraging the distractor with its leverage surface against the shaft of the fulcrum. 
     In another embodiment, a system includes an elongated distractor and an elongated fulcrum, which are positionable independently of one another through an operative approach to first and second vertebrae. The fulcrum and distractor are separately mountable to the first and second vertebrae. The distractor and fulcrum are configured to act upon one another so that the distractor can be leveraged off of the fulcrum to deliver a distraction force between the first and second vertebrae. 
     In one embodiment, the distal end of the compressor or distractor is mountable to an anchor engaged to the first vertebra, and the distal end of the fulcrum is mountable to an anchor engaged to the second vertebra. A connecting member extends between the first and second anchors, and is secured between the anchors when the desired compression or distraction has been obtained. The connecting member can be a rod, plate, staple, flexible member or other suitable device positionable to extend between vertebrae and engageable to the vertebrae. 
     The systems can be employed in minimally invasive approaches to the vertebrae. In one embodiment, the minimally invasive approach is provided by a tubular retractor inserted through the tissue to provide a protected passageway to the first and second anchors. In a further embodiment, the tubular retractor is expandable to increase the size of the working space adjacent the first and second vertebrae relative to the size of the incision through which the retractor is inserted. In another embodiment, the approach is provided by one or more retractor blades inserted through the incision to provide a pathway to the first and second vertebrae. In another embodiment, the systems are employed directly through the tissue through one or more micro-incisions. In another embodiment, the first and second vertebrae are exposed in an open surgical technique, and the systems are employed through the incision and retracted tissue providing the open approach. 
     The first and second vertebrae can be adjacent vertebrae of the spinal column, or can be vertebrae separated from one another by one or more intervening vertebrae. The approach to the vertebrae can be anterior, posterior, lateral, oblique, postero-lateral, or any other suitable approach. The first and second vertebrae can be located along any one or combination of regions of the spinal column, including the cervical, thoracic, lumbar and sacral regions. 
     Referring to  FIG. 1  therein shown a minimally invasive access portal  200  positioned through skin and tissue  202 . Access portal  200  provides a pathway to the spinal column, including first vertebra  204  and second vertebra  206  and spinal disc space  208  therebetween. In the illustrated embodiment, access portal  200  is an expandable tubular retractor such as is described in U.S. Patent Application Publication No. 2003/0191371 A1, which is incorporated herein by reference. The expandable tubular retractor provides a portal that defines a protected passageway to the spinal column. The tubular retractor includes a first insertion configuration in which the retractor is cylindrical and is moveable in situ to a second configuration in which the distal end of the retractor is enlarged to form a proximally tapered working channel between the distal and proximal ends of the retractor. However, as discussed above, any suitable instrument, technique, or retractor for accessing the spinal column is contemplated. In addition, vertebrae  204 ,  206  need not be directly adjacent vertebrae, and can be separated by one or more other vertebrae. 
     A construct  210  is engaged to vertebrae  204 ,  206  and extends therebetween. In the illustrated embodiment of  FIG. 1 , construct includes a first anchor  212  engaged to first vertebra  204 , a second anchor  214  engaged to second vertebra  206 , and a connecting member  216  extending between first and second anchors  212 ,  214 . Anchors  212 ,  214  can be multi-axial type screws with a first portion (not shown) including a screw member threadingly engageable to the respective vertebra, and a second portion with a receiver member pivotally mounted to an enlarged head of the screw member. Connecting member  216  is an elongated rod received in passages of the receiver members of the anchors. The rod can be secured in the receiver members with a plug that is engaged to respective ones of the receiver members to firmly seat the rod against a bottom surface of the receiver member. 
     Other forms for the construct are contemplated. For example, the anchors can be uni-axial screws, bolts, hooks, staples, spikes, interbody devices, fusion devices or cages, artificial disc devices, or other suitable structure including a first portion for engaging one or more vertebrae and a second portion for engaging the connecting member. The connecting member can be a plate, strut, tether, staple, spacer or other suitable device for extending between two or more anchors. Furthermore, the construct can be arranged to extend between more than two vertebrae, and can be engaged to three or more anchors. The plug can be a set screw, cap, or other device that engages the construct to the anchor. 
       FIGS. 1-6  show a compressor system  30  that is mountable to vertebrae  204 ,  206  and manipulatable relative thereto to deliver a compressive force between vertebrae  204 ,  206 . When the desired compression force has been applied, construct  210  is secured between vertebrae  204 ,  206  to maintain the compression post-operatively. In the illustrated embodiment, system  30  is mountable to anchors  212 ,  214  engaged to respective ones of the vertebrae  204 ,  206 . It is also contemplated that system  30  can be mounted directly to vertebrae  204 ,  206 ; or mounted to a secondary fastener or device engaged to vertebrae  204 ,  206  which does not form a part of the construct  210 . 
     System  30  includes a compressor  40  mountable to first vertebra  204 . Compressor  40  includes an elongated body  42  extending along a longitudinal axis  41  between a proximal end  44  and a distally oriented leverage surface  46 . A pair of arms  48  extends distally from body  42 . Arms  48  define an opening  58  therebetween. An engaging member  50  is provided at the distal ends of arms  48  and extends between arms  48 . As shown in  FIG. 2 , engaging member  50  is offset laterally relative to arms  48  by a pair of extensions  60  extending transversely to and laterally from respective ones of the arms  48  and an end member extending between extensions  60 . Arms  48  and engaging member  50  form a receptacle  51  for receiving a portion of an anchor engaged to a vertebra therein. 
     In the illustrated embodiment, receptacle  51  includes a generally rectangular shape that receives the receiver member of anchor  212  in a manner that prevents the receiver member from rotating relative to engaging member  50 . Other shapes for receptacle  51  are also contemplated, including omitting receptacle  51 , so long as engaging member  50  is capable of engaging an anchor or a vertebra. 
     Body  42  further includes opposing sidewalls  56  extending therealong, and a channel  52  extending between sidewalls  56 . Channel  52  includes a U-shape formed by a concavely curved surface sized to receive elongated shaft  72  of fulcrum  70  therein; however, other shapes are also contemplated. Body  42  includes an outer surface  54  opposite channel  52  having a convex curvature to facilitate gripping of body  42 . Outer surface  54  can also be non-curved, and include grip-enhancing features such as knurling, indentations, protrusions or the like. 
     Compression system  30  further includes a fulcrum  70  nestably positioned relative to compressor  40  and mountable to second vertebra  206 . Fulcrum  70  includes an elongated shaft  72  extending along a longitudinal axis  82  between a proximal end  74  and a distal engaging member  76 . Elongated shaft  72  defines a passage  75  extending therethrough. Handle  78  extends from proximal end  74  along a handle axis  80 . Handle axis  80  is oriented transversely to longitudinal axis  82 . In the illustrated embodiment, handle axis  80  is orthogonal to longitudinal axis  82 ; however, other transverse orientations are also contemplated. The transverse orientation of handle  78  facilitates maneuvering and gesturing of the fulcrum  70  through portal  200 . The transverse orientation of handle  78  also maintains access to passage  75 . In other embodiments, elongated shaft  72  does not include a passage  75 , but rather is solid. 
     Passage  75  can extend through engaging member  76 . Passage  75  includes a distally oriented opening in engaging member  76  that is structured to receive the receiver member of the anchor to which it is engaged therein. As shown in  FIG. 3 , the sides of engaging member  76  can be enlarged relative to the shaft  72  so as to extend about the head of the receiver members. Fulcrum  70  is oriented so that engaging member  76  can be positioned through opening  58  of compressor  40 . In  FIG. 4 , fulcrum  70  is rotated 90 degrees about longitudinal axis  82  relative to its  FIG. 3  orientation to align engaging member  76  with the receiver member of anchor  214 . As shown in  FIG. 5 , engaging member  76  is positioned about the receiver member of anchor  214 . The distal end of engaging member  76  includes a distally-oriented recess  84  ( FIG. 3 ) formed therein to receive connecting element  216  therein when engaging member  76  is fully seated on the receiver member of anchor  214 . The interface between engaging member  76  and the receiver member of anchor  214  can be configured so that fulcrum  70  cannot rotate relative to the receiver member of anchor  214 , allowing the alignment of the receiver member relative to fulcrum  70  to be maintained during the procedure. 
     In use, access portal  200  is positioned to access the spinal column. Procedures can be performed in disc space  208  or on vertebrae  204 ,  206 . Such procedures can include one or more of a discectomy, facectomy, laminectomy, artificial disc placement, fusion device placement, annulus repair or augmentation, or any other spinal surgical procedure. Anchors  212  and  214  can be engaged to respective ones of the vertebrae using any known instruments and techniques. Connecting member  216  can be positioned through access portal  200  and positioned in the receiver members of anchors  212 ,  214 . Connecting member  216  is tightly secured to one of the anchors, such as anchor  212 , with a plug engaged to the receiver member. The plug can be an internally or externally threaded set screw, nut, washer, cap or any other device or combination of devices capable of engaging the connecting member in, on, about or adjacent to the receiver member of the anchor. A second plug can also be positioned in the receiver member of the other anchor  214  to loosely retain connecting member  216  therein. 
     As shown in  FIG. 2 , compressor  40  is positioned about the receiver member of anchor  212 . Opening  58  is aligned with the receiver member of anchor  214 . In  FIGS. 3 and 4 , fulcrum  70  is delivered through portal  220  and opening  58  between arms  48  for engagement with anchor  214 , as shown in  FIG. 5 . When engaged to anchor  214 , fulcrum  70  is manipulated and nestably positioned relative to compressor  40  for manipulation relative to one another to deliver a compressive force to vertebrae  204 ,  206 . The nestable positioning maintains contact and alignment between compressor  40  and fulcrum  70  during compression of the spinal column. 
     In the illustrated embodiment, fulcrum  70  is received through opening  58  of compressor  40  such that shaft  72  and body  42 /arms  48  cross one another. Thus, the longitudinal axes  82 ,  41  of fulcrum  70  and compressor  40  form an X-shape in their engaged positions with anchors  212 ,  214 . Elongated shaft  72  of fulcrum  70  is positioned in contact with leverage surface  46  of elongated body  42 , and channel  52  is oriented toward elongated shaft  72  of fulcrum  70 . Connecting member  216  is received in recesses  62 ,  84  of engaging members  50 ,  76  of compressor  40  and fulcrum  70 , respectively, when compressor  40  and fulcrum  70  are fully seated on the respective anchors. Recesses  62 ,  84  allow engaging members  50 ,  76  of compressor  40  and fulcrum  70  to be seated further distally on the receiver members of the anchors, providing a firm grip about the anchor to maintain engagement during compression of the spinal column. 
     To compress vertebrae  204 ,  206 , the proximal ends  44 ,  74  of compressor  40 , fulcrum  70  are moved toward one another. Compressor  40  pivots relative to fulcrum  70  due to the contact between leverage surface  46  and the outer surface of elongated shaft  72  of fulcrum  70 . The location along elongated shaft  72  in contact with leverage surface  46  to effect pivoting of compressor  40  relative to fulcrum  70  can vary proximally and distally along shaft  72 . The contact location can vary depending on the separation distance of anchors  212 ,  214 , the alignment between vertebrae  204 ,  206 , the orientation of portal  200  relative to vertebrae  204 ,  206 , and the orientation of compressor  40  and fulcrum  70  relative to one another and to the anchors  212 ,  214 . Accordingly, compression system  30  has application even when anchors  212 ,  214  are not aligned with another or spaced various distances from one another while still minimizing the footprint of system  30  through portal  200 . As proximal ends  44 ,  74  are moved toward one another, the distal ends of fulcrum  70  and compressor  40  move toward one another, compressing vertebrae  204 ,  206  as shown in  FIG. 6 . 
     As compressor  40  and fulcrum  70  are moved toward one another, channel  52  of compressor  40  receives elongated shaft  72  of fulcrum  70 . This nesting arrangement further provides a low profile footprint for compression system  30  through portal  200 , allowing the size of portal  200  to be minimized. Furthermore, receipt of fulcrum  70  through opening  58  of compressor  40  provides a low profile footprint extending transversely to connecting member  216  since the longitudinal axes of compressor  40  and fulcrum  70  are aligned along the axis extending between the receiver members of anchors  212 ,  214 . 
     With connecting member  216  secured tightly in anchor  212  with a plug, connecting member  216  moves relative to anchor  214  as the vertebrae are compressed, moving anchors  212 ,  214  toward one another. When the desired compression has been obtained, the plug or set screw provisionally engaged to anchor  214  can be tightened with a driver instrument positioned through passage  75  of fulcrum  70 . Alternatively, a plug can be delivered through passage  75  of fulcrum  70  to engage the connecting member  216  to anchor  214 . Fulcrum  70  can further function as a counter-torque as the plug is tightened in the receiver member against the connecting member. Handle  78  can be grasped to prevent the receiver member and/or the bone engaging portion of anchor  214  from rotating as the plug is tightened into position. When secured to anchors  212 ,  214 , connecting member  216  can post-operatively maintain the compression applied with compressor  40  and fulcrum  70 . Compressor  40  and fulcrum  70  can then be un-mounted from anchors  212 ,  214  and removed through portal  200 . 
     Other embodiments contemplate other nestable arrangements between fulcrum  70  and compressor  40 . For example, compressor  40  and fulcrum  70  can be provided with an nesting configuration in which compressor  40  and fulcrum  70  extend along side one another, and include portions that overlap and are contactable with one another along a leverage surface to effect pivoting of compressor  40  and fulcrum  70  relative to one another. In another example, one or more of the longitudinal axes of compressor  40  and fulcrum  70  are offset relative to the longitudinal axis of the connecting member extending between anchors  212 ,  214 . 
     Referring to  FIGS. 7-14 , there is shown another embodiment compression system  130  that includes a compressor  90  and a fulcrum  120  engageable to another embodiment construct  210 . As shown in  FIG. 7 , construct  210  includes a first anchor  222  and a second anchor  224  engageable to first and second vertebrae, such as vertebrae  204 ,  206  discussed above. Each of the anchors  222 ,  224  includes a first portion (not shown) for engaging the vertebra. Anchors  222 ,  224  also include a second portion for securing the connecting member between the vertebrae. In the illustrated embodiment, the second portion is an enlarged head structure that clamps or secures the plate-like connecting member  220  to the respective vertebra. Connecting member  220  includes one or more central openings  226  through which anchors  222 ,  224  extend. The enlarged head structure of the second portion of the respective anchor bears against the upper surface of connecting member  220  to secure it to the respective vertebra. The head-like structure can be integrally formed with a threaded shaft or other body comprising the first anchor portion that is received through the central opening  226 . The second anchor portion can also be, for example, a nut, cap or other device that engages connecting member  220  to an anchor. 
     As shown in  FIG. 13 , compressor  90  includes an elongated body  92  extending along a longitudinal axis  91  between a proximal end  94  and a distally oriented leverage surface  96 . A pair of arms  98  extends distally from body  92 , and an engaging member  100  extends between arms  98  at their distal ends. An opening  108  is formed between arms  98  to receive the fulcrum therethrough. As shown in  FIG. 8 , engaging member  100  extends transversely to arms  98  and forms a receptacle  102  sized and shaped for positioning about the enlarged head of one of the anchors  222 ,  224 . In the illustrated embodiment, receptacle  102  is circular. Other embodiments contemplate other forms and shapes for receptacle  102 , including omitting receptacle  102 , so long as engaging member  100  is capable of engaging an anchor or a vertebra. As shown in  FIG. 11 , body  92  defines a channel  104  along one side thereof. Channel  104  can be U-shaped and defined by a concavely curved surface  106  extending between opposite sides  110 . A convexly curved outer surface  112  opposite channel  104  facilitates the surgeon grasping compressor  90  during the surgical procedure. 
     Another embodiment fulcrum  120  is positionable through portal  200  and engageable to the other of the anchors  222 ,  224 . Fulcrum  120  includes an elongate shaft  122  extending between a proximal end  124  and an opposite engaging member  126  at its distal end. As shown in  FIG. 11 , a passage  128  can extend through shaft  122  and open at its distal and proximal ends. Engaging member  126  includes a profile that receives and engages the second portion of the anchor  222 ,  224  to which it is mounted. In one embodiment, the second portion of the anchor is a nut or head and engaging member  126  is configured to engage the nut or head to allow rotational forces to be applied to the anchor with fulcrum  120 . 
     Anchors  222 ,  224  are delivered through portal  200  and engaged to respective ones of the vertebrae, and connecting member  220  is positioned between anchors  222 ,  224 , as shown in  FIG. 7 . If top-loading anchors  222 ,  224  are provided, the anchors are engaged to vertebrae  204 ,  206  before connecting member  220  is delivered and engaged to the anchors. If bottom loading anchors are provided, connecting member  220  is positioned along the vertebrae and anchors  222 ,  224  are positioned through central opening  226  to engage the connecting member to the vertebrae. In any event, one of the anchors  222 ,  224  is tightened to securely engage connecting member  220  to the respective vertebra. In the illustrated embodiment, anchor  224  is tightened, while anchor  222  is loosely positioned relative to connecting member  220 . 
     As shown in  FIG. 8 , compressor  90  is positioned through portal  220  with its engaging member  100  oriented toward anchor  224 . In  FIG. 9  fulcrum  120  is positioned with its elongated shaft  122  extending through opening  108 . Fulcrum  120  and compressor  90  are manipulated in portal  200  so that engaging member  126  is positioned about the second portion of anchor  222 , and so that engaging member  100  of compressor  90  is positioned about the second portion of anchor  224 . Leverage surface  96  of compressor body  92  is positioned against elongated shaft  122  of fulcrum  120 , as shown in  FIGS. 10-12 . Compressor  90  and fulcrum  110  are oriented relative to one another so that proximal ends  94 ,  124  are spaced from one another. As shown in  FIG. 12 , the longitudinal axes  91 ,  121  of compressor  90  and fulcrum  120  cross one another such that compressor  90  and fulcrum  120  form an X-shape, and distal engaging members  100 ,  126  are spaced from one another in a direction opposite the spacing of proximal ends  94 ,  124 . Fulcrum  120  is nestably positioned relative to compressor  90  to maintain a low profile footprint for compression system  130  through portal  200 , as discussed above with respect to compression system  30 . 
     To compress the vertebrae, proximal ends  94 ,  124  are moved toward one another, causing compressor  90  and fulcrum  120  to pivot relative to one another about their contact location at leverage surface  96 . As the proximal ends  94 ,  124  move toward one another, the distal engaging members  100 ,  126  move anchors  222 ,  224  and thus vertebrae  204 ,  206  toward one another along connecting member  220 . When the desired compression or separation distance between vertebrae  222 ,  224  has been obtained, anchor  222  can be tightened with fulcrum  120  to secure connecting member  220  between anchors  222 ,  224 . When secured, connecting member  220  maintains the vertebrae in the desired position and with the desired compression attained through use of compression system  130 . 
     A distraction system  160  will be discussed with reference to  FIGS. 15-22 . Distraction system  160  includes a low profile footprint positionable through portal  200  and engageable to vertebrae to distract the vertebrae relative to one another. Distraction system  160  includes a distractor  140  employed with a fulcrum, such as fulcrum  70  discussed above, which are leveraged off of one another to provide a mechanical advantage in delivering the distraction force to the vertebrae through portal  200 . 
     In  FIGS. 15 and 16  there is shown distractor  140  including an elongated body  142  extending along a longitudinal axis  141  between a proximal end  144  and a distal leverage surface  146 . An angled distal extension  148  extends distally along longitudinal axis  149  from leverage surface  146  to a distally extending engaging member  150 . Longitudinal axis  149  is angled relative to longitudinal axis  141  to angularly offset proximal end  144  from engaging member  150 . Engaging member  150  includes a flat, plate-like arm to facilitate positioning between anchors at the surgical site. A distally facing recess  152  is formed in a distal end of engaging member  150 . 
     Body  142  and angled extension  148  include a convexly curved outer surface  158  to facilitate gripping by the surgeon. Opposite outer surface  158  body  142  defines a proximal channel  154 , and angled extension  148  defines a distal channel  156 . Channels  154 ,  156  are in communication with one another and extend along respective ones of the longitudinal axes  141 ,  149  of body  142  and angled extension  148 . Channels  154 ,  156  can be defined by a concavely curved surface as discussed above with respect to compressors  40 ,  90 . Channel  154 ,  156  can form a U-shaped receptacle sized to receive elongated shaft  72  of fulcrum  70  therein. 
     A construct is positioned through the portal and engaged to vertebrae, such as shown in  FIG. 17 . In the illustrated embodiment, the construct includes anchors  212 ,  214  and connecting member  216 . Other embodiments contemplate other embodiment constructs as discussed herein. Connecting member  216  is provided with one end protruding from anchor  214  away from anchor  212  to provide a length of connecting member  216  along which anchor  214  can move as the distraction force is applied to the vertebrae. 
     A plug  215  can be engaged in anchor  212  to firmly secure connecting member  216  therein, and a plug can be loosely positioned relative to connecting member  216  in anchor  214 . In  FIG. 18  fulcrum  70  is positioned through portal  200  and its distal engaging member  76  is mounted to anchor  214 . In  FIG. 19  distractor  140  is positioned through portal  220  so that engaging member  150  is located between anchors  212 ,  214 , and connecting member  216  is received in recess  152 . Distal channel  156  is positioned about elongated shaft  72  of fulcrum  70 , as shown in  FIG. 20 . Fulcrum  70  is nestably received relative to distractor  140  to facilitate maintaining the distractor  140  and fulcrum  70  in contact with one another and in alignment during distraction. 
     In this initial pre-distraction configuration, proximal end  144  of distractor  140  is spaced from proximal end  74  of fulcrum  70 , as shown in  FIG. 19 , due to the angular offset between elongated body  142  and angled extension  148 . Leverage surface  146  is located at the junction between proximal channel  154  and distal channel  156  to provide a contact location for distractor  140  against shaft  72  of fulcrum  70 . Engaging member  150  is offset away from distal channel  156  so it can be positioned between anchors  212 ,  214  without interfering with engaging member  76  of fulcrum  70 . Leverage surface  146  can be positioned against shaft  72  at any one of a number of locations therealong depending on the separation between anchors  212 ,  214 , the angle of approach to the construct taken with distractor  140  and fulcrum  70 , the angle of approach taken with portal  200 , and other factors. 
     To distract the vertebrae, proximal end  144  of distractor  140  is moved from its initial configuration toward proximal end  74  of fulcrum  70 , as shown in  FIG. 21 . Distractor  140  pivots relative to fulcrum  70  about leverage surface  146  to move engaging member  150  and engaging member  76  away from one another as further shown in  FIG. 22 . This movement causes anchor  214  to slide along connecting member  216  as the vertebrae are distracted. When the desired distraction has been obtained, a driving tool can be positioned through passage  75  of, fulcrum  70  to secure the plug in anchor  214  against connecting member  216  to post-operatively maintain the distraction of the vertebrae. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, and that all changes and modifications that come within the spirit of the invention are desired to be protected.