Abstract:
An apparatus is provided for correcting spinal abnormalities, and particularly for providing compression and/or distraction of vertebrae without additional tools or instrumentation. A plate member is provided with a plurality of slots, one of which has a sloped internal edge or surface. The plate is anchored to one vertebra by a first anchor, and a second anchor is then placed through the slot with the sloped internal edge or surface and tightened. Such tightening causes the plate to move with respect to the tightened anchor, and thus to transmit compression or distraction to the vertebrae. The apparatus is particularly useful in minimally-invasive surgeries but can also be used in more traditional open surgeries.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an orthopedic implant assembly for use in stabilizing bone members in a desired spatial relationship in correcting bone misalignment disorders or for spinal or other bone fusion. In particular, the invention concerns a multi-axial spinal fixation system incorporating an elongated member such as a plate.  
         BACKGROUND OF THE INVENTION  
         [0002]    In the art of orthopedic surgery, and particularly in spinal surgery, it has long been known to affix an elongated member, such as a plate or rod, to bones in order to hold them and support them in a given position. For example, in a procedure to fuse damaged, diseased, malformed, or otherwise abnormal vertebrae, the vertebrae are positioned in a corrected position by a surgeon. An elongated plate is placed adjacent to the vertebral bone, and bone anchors, such as specially-configured screws or bolts, are employed to secure the plate to the bones. With such anchors, placement is accomplished by drilling one or more holes in the bone(s) and threading the anchors into the holes. As examples, see U.S. Pat. No. 5,676,666 to Oxland et al., U.S. Pat. No. 5,613,967 to Engelhardt et al., and U.S. Pat. No. 5,603,713 to Aust et al. An anchor can be connected to the bone, as by threading into a vertebral hole, through a plate, or alternatively the plate can be placed in position over or around the anchor after the anchor is connected to the bone. The anchor and plate are then secured to each other to minimize or prevent relative movement. In this way, bones may be spinal held and/or supported in proper alignment for healing.  
           [0003]    It has been found desirable for implant systems to have the capability for angular orientation of a bolt or other anchor in multiple planes relative to the elongated member or other fixation mechanisms of the implant system. Such features enable bone anchors to be placed at angles which are optimal for anchoring, thus reducing the chance of loosening, pull-out, or other movement of the anchors while not compromising the optimal positioning of the fixation plate.  
           [0004]    Additionally, such systems alleviate awkwardness frequently found in spinal surgery due to uneven bone surfaces and the abnormality to be corrected and generally require less adjustment to the implant, rendering corrective surgery easier for the surgeon and less traumatic for the patient.  
           [0005]    Various approaches have been used to achieve such multi-axial capability. For example, U.S. Pat. No. 5,735,853 to Olerud discloses an implant device in which a bone bolt can occupy different angular positions in relation to a plate by providing a compressible spherical collar which snap-fits around the bolt, which collar is rotatable and tiltable in a spherical opening in a plate insert. The compression fit of the bolt and collar within the plate can present difficulty in assembling the apparatus, particularly in a fluid-prevalent environment.  
           [0006]    Another approach is shown in U.S. Pat. No. 5,304,179 to Wagner, which shows a bone screw fixed inside a bushing at an angle with respect to the longitudinal axis of the bushing. The bushing is rotatable within a portion of a connector angled with respect to the axis of the adjoining rod-based instrumentation. The connector is rotatable around the instrumentation axis. The Wagner system permits only discrete positions of a bone screw in three-dimensional space to be achieved, and the bushings add extra length and profile to the construct, as well as extra parts for the surgeon to handle and arrange.  
           [0007]    A third approach is shown in U.S. Pat. No. 5,984,924 to Asher et. al., which shows a bone alignment system having an elongated bone alignment member sandwiched between two pairs of washers. Each such pair of washers have corresponding surfaces that mate together in a “ball and socket” configuration to potentially occupy a plurality of positions. When the shaft of a bone anchor extends through each washer pair, and also through an aperture of the elongated member, the washer pairs enable the shaft to be oriented at various angles relative to the elongated member. This approach also requires a plurality of small parts for handling and assembly during surgery. Further, since the washers in that system lie outside of the elongated member, they increase the thickness of the overall construct, with the attendant increase in the difficulty of use in a small surgical space and in the potential for patient discomfort.  
           [0008]    As noted above, in placing such implants a surgeon is commonly required to reposition vertebrae so that a normal spinal curvature results from the surgery. In open surgical procedures, the surgeon may reposition vertebra(e) manually or may have tools to assist in the repositioning. Once the vertebrae are repositioned, implants can then be attached in order to hold the vertebrae in the desired position. Alternatively, it is also known to provide a rod that is pre-bent to approximate a normal spinal curvature and to provide hooks or screws that can hold the rod which attach to several vertebrae. With such apparatus, vertebrae can be repositioned by forcing the pre-bent rod into engagement with the hooks or screws that are already anchored in the vertebrae. Even with that method, however, additional tools such as a rod reducer are required. For example, to compress (i.e., push together) or distract (i.e., push apart) two vertebrae, it is known to use, among other relatively large tools, a scissors- or tongs-like device by squeezing or pulling apart on handles of such a tool; distal parts of the tool that contact vertebrae or devices attached to vertebrae will cause the distraction or compression.  
           [0009]    Performing these tasks using traditional techniques and devices of open surgery has several undesirable features and consequences. Initially, such open surgery requires a long incision which leaves a relatively long and unappealing scar. Further, such surgery entails incision, retraction, and adjustment of numerous tissues in addition the spinal tissues. As a result, trauma to these tissues and resulting pain and possibility of infection are relatively high. Still further, a standard thoracotomy or other incision may expose only one apex of the spinal curve to be corrected, thus requiring additional long incisions or a longer initial incision in order to be able to fully treat the spine. Even where the apex of the spinal curve is adequately exposed and in good position relative to the thoracotomy for surgery, commonly adjacent vertebrae and intervertebral discs are not parallel to the exposure view provided by the incision, decreasing the effectiveness of instrumentation used to correct the abnormal curvature. For these reasons, an endoscopic, thoracoscopic, or other minimally-invasive approach is preferable.  
           [0010]    Accordingly, there remains a need for a device that simplifies adjustment or repositioning of vertebrae, particularly when a minimally-invasive approach is used.  
         SUMMARY OF THE INVENTION  
         [0011]    In one embodiment, an apparatus is disclosed comprising a plate member having a curvature, a first slot and a second slot, and sized to be inserted into the body through a minimally-invasive, open or other surgical opening. The slots each have a side wall sized to accommodate at least a portion of a bone anchor. A sloped surface is provided within said second slot, with the surface sloping in a longitudinal direction. A first bone fixation element that is adapted to engage the plate member is also provided, wherein at least a part of the first bone fixation element is capable of being within the first slot. A second bone fixation element is adapted to engage the plate member within the second slot along the sloped surface, whereby tightening the second bone fixation element after engagement with the sloped surface causes the plate member to move with respect to the second bone fixation element.  
           [0012]    In specific embodiments, the curvature of the plate member may approximate a natural curvature of one or more spinal segments, such as a lordotic or kyphotic curvature. The sloped surface may slope approximately uniformly, may be integrally formed as a part of the wall of the slot, and may have a downward or upward slope (viewed from an end of the second slot near an end of the plate member toward the end of the second slot in the middle of the plate member). A part of the surface may have no slope, i.e., may be substantially parallel to the bottom of the plate member. A bone fixation element retainer (e.g. a set screw) may be provided connected to the plate member (e.g. via a threaded hole) adjacent the second slot. The bone fixation elements may be part of a multi-axial bone fixation apparatus, standard bone screws, or screws having a head portion with a rounded underside and a diameter larger than a distance between adjacent portions of the sloped surface. The apparatus can further include additional slots sized to accommodate at least a portion of a bone anchor, and bone anchors for such slots.  
           [0013]    In another embodiment, a kit is provided comprising at least one plate member, each having a curvature, a first slot, a second slot and a sloped surface within said second slot. The said surface slopes in a longitudinal direction, and the plate member(s) are sized to be inserted into the body through a minimally-invasive, open or other surgical opening. Also provided is at least one first bone fixation element, each adapted to engage the plate member(s) and each having at least a part capable of being within the first slot, and at least one second bone fixation element, each adapted to engage the plate member(s) along the sloped surface. The kit may include a plurality of plate members not all of the same size and/or curvature, and some may have an upward slope while others have a downward slope. The plate members can be configured for attachment to the spine in one or more of the cervical, thoracic, lumbar, and sacral regions. The kit may also have a plurality of the first and/or second bone fixation elements adapted for attachment to the spine in one or more of the cervical, thoracic, lumbar, and sacral regions.  
           [0014]    In yet another embodiment, a method is provided comprising providing a plate member having a curvature approximating a natural spinal lordosis curvature, a first slot and a second slot with a sloped surface formed within said second slot, and sized to be inserted into the body through a minimally-invasive, open or other surgical opening: inserting the plate member through the opening into a patient proximate to a vertebra to which the plate member is intended to be attached; placing a first anchoring member through the first slot and into a first vertebra; placing a second anchoring member through the second slot and into a second vertebra; and tightening the second anchoring member against the sloped surface so that the plate member moves with respect to the second anchoring member. The first anchoring member can be tightened with respect to said plate member prior to tightening the second anchoring member. The method can also include loosening the first and second anchoring members, adjusting the plate member along the vertebrae, and retightening the anchoring members. Tightening the second anchoring member can cause one of compression and distraction of vertebrae, and tightening can be ceased when a predetermined amount of one of compression and distraction of vertebrae has occurred.  
           [0015]    In still another embodiment, a method of implanting a spinal implant having a lordosis curvature and a plurality of longitudinal slots, at least one of the slots having a surface slanted along the longitudinal direction, comprises making a minimally-invasive, open or other surgical opening proximate to first and second vertebrae in a patient: preparing a first hole in the first vertebra and a second hole in the second vertebra through the opening; inserting a first fixation member through the opening and into the first hole; inserting the implant through the opening and into a position adjacent the vertebrae such that the first fixation member is within one of the implant&#39;s slots and another of the slots in the implant is adjacent the second hole, that second slot including the slanted surface; inserting a second fixation member through the opening and through the second slot and into the second hole; and tightening the second fixation member such that it and the second vertebra move with respect to the implant.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a perspective view of one embodiment of a device having features according to the present invention.  
         [0017]    [0017]FIG. 2 is a side view of the embodiment illustrated in FIG. 1.  
         [0018]    [0018]FIG. 3 is an exploded view of the embodiment illustrated in FIG. 1.  
         [0019]    [0019]FIG. 4 is a cross section taken along the lines IV-IV in FIG. 1 and viewed in the direction of the arrows.  
         [0020]    [0020]FIG. 5 is a magnified view of a portion of the embodiment illustrated in FIG. 1.  
         [0021]    [0021]FIG. 6 is a perspective view of another embodiment of a device having features according to the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated herein 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 alterations and further modifications in the described processes, systems or devices, and any further applications of the principles of the invention as described herein, are contemplated as would normally occur to one skilled in the art to which the invention relates.  
         [0023]    Referring now generally to FIGS. 1-5, there is shown a plate member  20  with a multi-axial bone fixation member  22  and a bone fixation member  24 . Plate member  20  is elongated and includes a plurality of slots. In the illustrated embodiment, plate member  20  includes two slots  30  and  32 , although it will be appreciated additional slots could be placed in plate member  20 . In a particular embodiment, plate member  20  and slots  30  and  32  are sized so that plate member  20  can contact neighboring vertebrae, and slots  30  and  32  will each be adjacent one of those vertebrae so that fixation members can be placed through slots  30  and  32  and into the vertebrae. Plate member  20  may also be sized and configured to extend across more than two adjacent vertebrae.  
         [0024]    In the illustrated embodiment, slot  32  is near a first end  34  of plate member  20 , and slot  30  is near a second end  36  of plate member  20 . Plate member  20 , in the illustrated embodiment, is pre-bent or formed to include a curvature, for example a natural spinal lordosis curvature. As shown particularly in FIGS. 2 and 3, plate member  20  has a concave curvature, as viewed from the top. It will be understood that any curvature appropriate for one or more segments of the spine (whether cervical, thoracic, lumbar or sacral) could be incorporated into plate member  20 . Such curvatures can include entirely convex, entirely concave, entirely straight (i.e. essentially planar), and combinations thereof. As noted previously, in the illustrated embodiment a lordosis curvature is depicted and is particularly a curvature characteristic of the lumbar spine. Plate member  20  could alternatively be part-lordotic with an uncurved portion, part-kyphotic with an uncurved portion, wholly kyphotic, or have another curvature or combination of curvatures.  
         [0025]    In the illustrated embodiment, slot  30  is a longitudinal, oval-shaped slot. Slot  30  extends through plate member  20  from top to bottom. Proximate to the bottom of plate member  20 , a ledge  38  extends into slot  30 . Ledge  38 , along with surfaces  40  and  42  of plate member  20 , defines grooves  44  that run longitudinally along plate member  20  within slot  30 . Grooves  44  accommodate a part of multi-axial bone fixation element  22 , as will be described hereafter.  
         [0026]    Slot  32  is also depicted in the illustrated embodiment as a longitudinal, oval-shaped slot. Slot  32  extends through plate member  20 , from top to bottom. A sloped wall portion  46  extends into slot  32  and is preferably integral with plate member  20 . In the illustrated embodiment, wall portion  46  has a concavely rounded portion  48  that ends in a sloping edge or surface  50 . By “sloping,” it is meant that points along edge or surface  50  are at different distances from the top surface of plate member  20  at different places along edge or surface  50 , and may be approximately linear or have another suitable configuration. In the illustrated embodiment, a point along edge or surface  50  that is closer to first end  34  of plate member  20  than another point along edge or surface  50  will be closer to the top surface of plate member  20 . It will be understood that edge or surface  50  may have a flat or non-sloped portion, that is, a portion that is substantially horizontal or parallel to a bottom surface of plate member  20 . Such a portion in the present embodiment may preferably be adjacent the end of slot  32  that is toward a middle portion of plate member  20 . In a specific embodiment, an upper edge  52  of slot  30  is sized so that the head of a bone screw or other fixation member (e.g., fixation member  24 ) will fit within edge  52 , but edge or surface  50  will not allow the head of such a fixation member to pass.  
         [0027]    The illustrated embodiment of plate member  20  further includes a hole  54  adjacent to slot  32 . Hole  54  is for accommodating a retainer designed to hold fixation member  24  within slot  32 , or to prevent fixation member  24  from backing out, such as set screw  56  (FIG. 5), a cam or sliding wedge member, a spring-loaded member or a similar device. In the embodiment in which set screw  56  is used, hole  54  will include a threaded portion  58 . Hole  54  is preferably sized to accommodate at least a portion of the retainer (e.g., set screw  56 ), so that its top extends minimally or not at all over the top surface of plate member  20 , thus reducing the profile of the overall construct.  
         [0028]    Multi-axial fixation member  22  includes a bone bolt  60 , a stabilizing member  62 , a washer  64 , and a nut  66 . The respective elements of multi-axial fixation member  22  are described in detail in U.S. Pat. Nos. 6,280,445 and 6,315,779 to Morrison et al., and the entirety of those patents are incorporated herein by reference. In the illustrated embodiment, washer  64  and nut  66  are pre-attached, as is shown and described in U.S. Pat. No. 6,315,779. It will be appreciated that embodiments of the present invention are contemplated in which washer  64  and nut  66  are separate and are not associated with each other or in contact with each other until the attachment of multi-axial fixation member  22  to plate member  20 .  
         [0029]    Fixation member  24  is shown in one embodiment as a standard bone screw having an attachment portion  68  with cancellous threads  70 , and a head portion  72 . Head portion  72  includes a tool-engaging aperture  74 , and preferably includes a rounded underside  75 . As noted previously, the diameter of head portion  7 ′ is preferably larger than the distance between sections of edge or surface  50  on opposite sides of slot  32 , so that head portion  72  cannot pass through slot  32  in plate member  20 .  
         [0030]    For ease of use, a kit containing one or more of the parts of the implant may be provided. For example, a kit may include several embodiments of plate member  20 , or one or more embodiments of plate member  20  in several different lengths, sizes and/or curvatures. Lengths or sizes appropriate for cervical, thoracic, lumbar and/or sacral implantation may be included. One or more sets of screws, bolts, stabilizers, washers, and/or nuts, preferably in a variety of sizes or adapted for attachment to one or more of the cervical, thoracic, lumbar and sacral regions of the spine, may also be provided in such a kit. For example, one or more fixation members  22  and/or  24  for engaging one or more slots in the plate members may be included. Further, retainers for holding fixation member  24  within slot  32  (e.g., set screw  56 ) may also be provided. In a specific embodiment of such a kit, each plate member  20  is provided with stabilizing member  62  preloaded into grooves  44  under slot  30 . A catch, boss, or stop may be provided within grooves  44  or on stabilizing member  62  so that stabilizing member  62  cannot exit grooves  44  and fall out of plate member  20 . Similarly, if washer  64  and nut  66  form an initial unit, as shown in U.S. Pat. No. 6,315,779, a variety of such units may be provided in the kit. Alternatively, separate quantities of nuts and washers can be provided.  
         [0031]    A method of using the implant will now be described. As noted above, the implant can be used in minimally-invasive surgical procedures, and the methods described below reflect such procedures. It will be appreciated by those of skill in the art that the features that enable a minimally-invasive approach to be used with the implant will also make the implant easier to insert via a standard open or other surgical procedure.  
         [0032]    Using a minimally-invasive technique, a surgeon will make an incision into the patient at a place relatively proximate to the vertebrae or other bone(s) to which the implant is to be attached. As is known in the art, a tube of sufficient length to extend to the implantation site from a point above the incision in the skin is inserted into the incision, and visual access to the site is obtained. After the appropriate access to the surgical site is obtained, a portion of the inferior vertebra to be instrumented (e.g. the pedicle) is prepared in a standard manner. For example, an awl may be used to prepare a hole, which is then probed for depth and tapped as appropriate for a bolt or screw element. Bolt  60  of the multi-axial bone fixation member  22  is then inserted into the hole in the inferior vertebra. Access to a portion of the superior vertebra (e.g. the pedicle) to be instrumented is then obtained, either via the previous incision or via a similar minimally-invasive incision. The point on the superior vertebra at which the implant is to be attached is identified, and the vertebra is prepared as described above. However, in the preferred embodiment, fixation member  24  is not yet inserted in the superior vertebra. Plate member  20  is then inserted (e.g., through the tube in the minimally-invasive incision). Plate member  20  is positioned over bone fixation member  22  and slot  30  is bottom-loaded (i.e. bone fixation member  22  is inserted into slot  30  through the bottom of plate member  20 ) so that bone fixation member  22  fits within slot  30 . Plate member  20  is then translated or otherwise moved until the hole in the superior vertebra is adjacent slot  32 . In one particular embodiment, the hole in the superior vertebra should be underneath the uppermost region of slot  32 , i.e., the region closest to end  36  of plate member  20 . Washer  64  and nut  66  are then placed on bolt  60 , and nut  66  is tightened down onto washer  64  and plate member  20  to hold plate member  20  in position relative to the inferior vertebra. It will be noted that locking plate member in position can be performed solely by a nut  66 , without an intermediary washer  64 .  
         [0033]    With plate member  20  locked with respect to the inferior vertebra, fixation member  24  can be top-loaded in plate member  20  (i.e. inserted through the top of plate member  20  and through slot  32 ) into the hole prepared in the superior vertebra. Fixation member  24  is inserted until its head portion  72  contacts sloped edge or surface  50  within slot  32 . Fixation member  24  is then tightened further causing the plate member  20  to move with respect to fixation member  24 . In effect, as fixation member  24  is tightened, plate member  20  slides in a direction parallel to slot  32  with respect to fixation member  24  and the superior vertebra, so that fixation members  22  and  24  approach each other. Since plate member  20  is locked with respect to fixation member  22  and the inferior vertebra, this sliding action causes the inferior and superior pedicles to be brought closer together, providing compression. Further, the curvature of the plate itself can provide correction to the curvature of the spine if it contacts the vertebrae as fixation member  24  is tightened with respect to plate member  20 . Tightening of fixation member  24  can continue until the maximum amount of adjustment (e.g. compression) is obtained, or it can be discontinued when a predetermined amount of adjustment has occurred.  
         [0034]    In many cases, the amount of compression or other correction of the vertebrae can be determined prior to surgery, and the positions of the holes in the vertebrae can be predetermined so that the vertebrae are in their proper, corrected positions when fixation member  24  is tightened to the extent that the head of fixation member  24  rests approximately at a point at which edge or surface  50  no longer slopes, or to the end of slot  32  that is toward the middle of plate member  20 . In other words, commonly fixation member  24  can be tightened to a point where no further sliding action of plate member  20  with respect to fixation member  24  is possible. It will be appreciated, however, that in some cases proper correction will dictate that the tightening of fixation member  24  should stop even though head portion  72  of fixation member  24  has not yet reached the end of slot  32 . When the tightening of fixation member  24  is complete, a retainer or anti-migration or holding element (such as set screw  56 ) can be inserted into aperture  54  or otherwise attached to plate member  20  adjacent fixation member  24  to cover and/or contact a portion (e.g. head portion  72 ) of fixation member  24 .  
         [0035]    If it is noted that the steps above do not provide adequate compression, fixation member  22  can be released, i.e., nut  66  can be loosened. Plate member  20  can then be adjusted by moving plate member  20  with respect to bolt  60  along slot  30 , and nut  66  can then be retightened. In this way, end  34  of plate member  20  can be moved closer to the hole in the superior pedicle, resulting in the opportunity for more compression as fixation member  24  is tightened and plate member  20  slides a further distance with respect to fixation member  24 . Similarly, if less compression is desired, plate member  20  should be positioned (or repositioned) such that the hole in the superior pedicle is closer to the end of slot  32  that is toward the middle of plate member  20 . In a case in which no compression of the vertebrae is desired, plate member  20  should be positioned so that the hole in the superior pedicle is directly under the end of slot  32  closer to the middle of plate member  20 , or so that the hole in the superior pedicle is over a relatively flat or non-sloped portion of edge  50 .  
         [0036]    As previously noted, the above-described technique is one preferred embodiment of a method of using the described implant. It should be noted that the technique can be reversed, that is, slot  32  can be adjacent a superior vertebra and slot  30  can be adjacent an inferior vertebra. Those with skill in the art will recognize that compression and/or distraction can also be obtained by using an additional external compression or distraction instrument.  
         [0037]    In another embodiment of the invention, shown in FIG. 6, plate member  120  is shown. Plate member  120  is similar in many respects to plate member  20 , described above. However, plate member  120  is particularly useful in multi-level implantations (i.e., implantation over several respective vertebrae). Plate member  120  would include slots  130   a  and  130   b , similar to slot  30  of plate member  20 , and a slot  132 , similar to slot  32  in plate member  20 . Slots  130   a  and  130   b  are shown with fixation members  122 , which are similar to fixation members  22  with plate member  20 . A fixation member  124  that is similar to fixation member  24  described above is shown in slot  132 . In use, pedicles for three vertebrae would be prepared as described above, each with a hole that may be tapped. The bolt portions of fixation members  124  would be inserted into the two most inferior vertebrae and plate member  120  placed over them so that they extend through slots  130   a  and  130   b . Plate member  120  would then be positioned so that the hole in the superior-most pedicle is under slot  132 . Washers  164  and nuts  166  are placed on bolts  160 . The lower- or inferior-most fixation member  122  is then locked with respect to plate member  120  by tightening its respective nut  166 . Fixation member  124  is then inserted through slot  132  and into the hole in the superior-most pedicle, and tightened as described above, to provide compression or distraction. The middle vertebra is allowed to float during the compression or distraction. Following the tightening of fixation member  124 , the remaining fixation member  122  (attached to the middle vertebra) is locked with respect to plate member  120  by tightening its respective nut  166 .  
         [0038]    Plate member  120  also shows a transverse hole  200  and slot  202  at one end  134  of plate member  120 . If desired, a pin (not shown) can be placed in hole  200  and through slot  202  to provide a way of holding or gripping plate member  120 . The surgeon can use a gripping tool having teeth or a rounded opening, so that the teeth grip or the rounded opening surrounds such pin within hole  200  and slot  202 . Plate member  120  (or plate member  20  if provided with a similar hole and/or slot and pin) can then be lowered into the surgical site while the surgeon holds onto the tool that grips plate member  120 . If no pin is placed in hole  200 , a proper gripping instrument could grip plate  120  at slot  202  (or plate member  20  if provided with a similar slot).  
         [0039]    It will be appreciated that a plate member providing distraction can be formed in a similar fashion to that of plate member  20 . As described above, plate member  20  includes a slot  32  with a sloping edge or surface  50 . The downward slope of edge or surface  50  is generally from a point near the end  36  of plate member  20  toward the middle of plate member  20 . A distraction plate, conversely, could include a sloped edge or surface that slopes generally upward from a point near the end  36  of plate member  20  toward the middle of plate member  20 . Thus, as a fixation member  24  is tightened in such a distraction plate, the distraction plate would slide with respect to fixation member  24  such that the instrumented vertebrae would be pushed apart from each other, providing distraction.  
         [0040]    It will further be appreciated that the embodiments described above should be made of materials suitable for implantation within the human or other body, and may consist of inert metals like titanium or stainless steel. Other sturdy materials such as certain ceramics or plastics may also be considered. Bio-resorbable materials, such as polylactic acid compounds, may be used along with or as a part of the parts described above.  
         [0041]    As noted above, the bone fixation element  22  and  122  is described herein as the structures shown in U.S. Pat. Nos. 6,280,445 and 6,315,779, the entire disclosures of which are incorporated herein by reference. As indicated in those patents, such bone fixation elements allow multi-axial positioning of the plate member  20  with respect to the fixation element  22 . This allows for further freedom in plate positioning and spinal correction via a minimally-invasive incision. It will be appreciated, however, that other known fixation elements may be used in place of the described fixation elements  22 ,  122 ,  24 , and  124 . Further, while slot  30  is described above as bottom-loading and slot  32  as top-loading, it will be seen that with variations in plate member  20  and/or differing fixation elements the slots may be loaded each from the same direction, or slot  30  may be loaded from the top and slot  32  from the bottom.  
         [0042]    Additionally, the methods and structures described above have been generally noted as effective in minimally-invasive surgical procedures, i.e. those in which one or more relatively small holes are opened through the skin and to the surgical site. It will be appreciated that the methods and structures described above can also be used in other types of surgical procedures, such as open procedures.  
         [0043]    It is also contemplated that processes embodied in the present invention can be altered, rearranged, substituted, deleted, duplicated, combined, or added to other processes as would occur to those skilled in the art without departing from the spirit of the present invention. In addition, the various stages, steps, procedures, techniques, phases, and operations within these processes may be altered, rearranged, substituted, deleted, duplicated, or combined as would occur to those skilled in the art. All publications, patents, and patent applications cited in this specification are herein incorporated by reference as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference and set forth in its entirety herein.  
         [0044]    Further, any theory of operation, proof, or finding stated herein is meant to further enhance understanding of the present invention and is not intended to make the scope of the present invention dependent upon such theory, proof, or finding.