Abstract:
Spinal fixation systems may be installed utilizing instruments and techniques alone or in combination with selectively attached extension members mounted on vertebral anchors to extend percutaneously from the spine. The surgical procedures associated with this invention involve making small, discrete incisions for the placement of select vertebral anchors. The extension members retract soft tissue, muscle and the like to thereby provide visibility and access to the head of the anchor. Instrumentation is utilized to deliver and install components such as a spine rod, set screw and other required hardware to the anchors. Once a spine rod or other components are secured to the pedicle screws, the instrumentation and extension members are removed from the patient.

Description:
BACKGROUND 
       [0001]    This invention relates generally to spinal fixation surgery and more specifically relates to instrumentation and associated techniques for minimally invasive installation of vertebral connecting elements of spinal fixation constructs. 
         [0002]    The human spinal column is a highly complex system of bones and connected tissues that provide support for the body and protects the delicate spinal cord and nerves. The spinal column includes a series of vertebrae stacked one atop the other. Each vertebral body includes a relatively strong cortical bone portion forming the outside surface of the body and a relatively weak cancellous bone portion forming the center of the body. An inter-vertebral disc is situated between each vertebral body that provides for cushioning and dampening of compressive forces applied to the spinal column. The vertebral canal containing delicate spinal cords and nerves is located just posterior to the vertebral bodies. 
         [0003]    A variety of types of spinal column disorders may be caused by abnormalities, disease, trauma or the like and result in debilitating pain as well as diminished nerve function in many cases. One known technique to address many such spinal conditions is commonly referred to as spinal fixation. Surgical implants are used for fusing together and/or mechanically immobilizing adjacent vertebrae of the spine. Spinal fixation may also be used to improve the position of the adjacent vertebrae relative to one another so as to alter the overall alignment of the spine. Such techniques have been used effectively to treat many spinal conditions and to relieve pain suffered by the patient. 
         [0004]    One particular spinal fixation technique includes immobilizing the spine by using connecting elements or orthopedic spine rods which run generally parallel to the spine. This is accomplished by exposing the spine posterially and fastening hooks, bone screws, or anchors to the pedicles of the appropriate vertebrae. The vertebral anchors are generally placed two per vertebrae, one at each pedicle on either side of the spinal column and serve as anchor points for the connecting elements or spine rods. The aligning influence of the rods forces the spine to conform to a more desirable shape. In many cases, the spine rods are bent to achieve the desired curvature of the spinal column. 
         [0005]    Installation of such spinal fixation constructs conventionally requires a surgeon to prepare a long incision aligned with the spinal column of a patient. The pedicle screws, hooks or other vertebral anchors are then attached to a number of vertebrae after which the connecting element or spine rod is located with respect to saddles or U-shaped channels attached to the vertebral anchors. Conventional surgical methods require a large midline incision and retraction of skin, muscle and other tissue to provide the surgeon with sufficient visualization of the pedicle bone structure. 
         [0006]    The accuracy of the placement and configuration of the spine fixation elements are very important. In combination with the relatively long incision typically required for the installation of the fixation construct, extended surgical procedures and related difficulties or complications are generally recognized as major contributing influences for extended patient recovery and less than optimal spinal fixation results. Therefore, surgical techniques and the associated instrumentation to accomplish more minimally invasive installation of the spinal fixation construct is highly desirable to avoid the problems associated with known surgical installation techniques. 
       SUMMARY OF THE INVENTION 
       [0007]    This invention addresses these and other shortcomings in the prior art. The devices and methods associated with this invention are used to aid in the surgery and installation of vertebral fixation components, particularly the connecting element or spinal rod. 
         [0008]    As is common in many spinal fixation systems, vertebral anchors such as pedicle screws are inserted into the target vertebrae of a patient&#39;s spinal column. The spinal fixation system typically includes a connecting element joining at least two vertebral anchors to provide added support and a degree of rigidity to the patient&#39;s spine. The connecting element may be a rigid spine rod that is generally linear or shaped, as appropriate, or the connecting element may be a less rigid structure. Nevertheless, installation of the connecting element to the vertebral anchors coupled to the respective vertebrae is facilitated through a minimally invasive surgical procedure according to various embodiments of this invention. 
         [0009]    In one aspect, this invention is directed to a tool for manipulating the connecting element of the spinal fixation system relative to the vertebral anchors. The tool includes a first elongate member having proximal and distal ends in which the distal end is configured for insertion through an incision in a patient for placement proximate one of the vertebral anchors coupled to a vertebrae of the spinal column. A handle is provided proximate the proximal end of the elongate member and configured to be grasped by a surgeon for manipulation of the tool. A connecting element retainer is provided proximate the distal end of the elongate member. The retainer is configured to selectively hold the connecting element for insertion through the incision in an orientation generally perpendicular to the spinal column and subsequent subcutaneous reorientation generally parallel to the spinal column. In another aspect of this invention, a pivoting mechanism is included on the elongate member and is configured to reorient the connecting element relative to the longitudinal axis of the elongate member for installation of the connecting element onto the vertebral anchors after insertion through the incision. 
         [0010]    The tool may include a second elongate element pivotally coupled to the first elongate element at a medial position between the distal and proximal ends of the first elongate element. The second elongate element may also include a handle configured for grasping and manipulation by the surgeon. The first and second elongate element may be coupled together in a scissor-like fashion according to various embodiments of this invention. 
         [0011]    A passage may be included at a distal end of one of the elongate elements is configured to allow installation of the connecting element through the passage. The connecting element retainer is provided on the other elongate element and through manipulation of the handles the connecting element is forced through the passage and into the vertebral anchors for secure attachment. 
         [0012]    In other aspects and embodiments of this invention, a lever is coupled to the elongate member and is adapted to actuate the pivotal movement of the connecting element via the connecting element retainer for appropriate positioning and subsequent installation to the vertebral anchors. 
         [0013]    Other embodiments of this invention utilize a connecting element retainer on the elongate member which is adjustable to accommodate a range of sizes of the connecting element while still holding and retaining the connecting element for proper positioning and installation with respect to the vertebral anchors. In some aspects of this invention, a clamp is configured to selectively retain one end of the connecting element and utilizes a jaw positioned proximate the distal end of the elongate member. The jaw is movable relative to the elongate member and may include a multi-bar linkage to provide for a variety of clamping force parameters to accommodate a variety of connecting elements and associated installation requirements. 
         [0014]    In other embodiments of this invention, an extension member is configured to be selectively coupled to one of the vertebral anchors to provide percutaneous access to the vertebral anchor when coupled thereto. The tool kit for manipulating the connecting element into position relative to the vertebral anchors may include not only the extension member mounted to the vertebral anchors but also the connecting element installation tool. The extension member may include a lumen axially aligned with the vertebral anchor to pass a set screw or other components to the vertebral anchor for installation of the connecting element. A recess may be provided on the extension member which is offset from the primary lumen and configured to direct and guide the connecting element installation tool and the connecting member to the vertebral anchors. 
         [0015]    The various embodiments of this invention enable the surgeon to install the spinal fixation construct with smaller discrete incisions as opposed to an extended incision. As such, a more minimally invasive surgical procedure can be accomplished with this invention thereby promoting patient recovery post-surgery. As a result of these and other aspects of this invention, increased efficiency and accuracy is provided for installation of a spinal fixation construct in a minimally invasive atmosphere thereby promoting patient recovery and optimum spinal surgery results. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0017]      FIG. 1  is a perspective view of a vertebral anchor extension member utilized in a spinal fixation construct according to various embodiments of this invention; 
           [0018]      FIG. 2  is a side elevational, partially in cross-section, of the extension member of  FIG. 1  mounted upon an exemplary vertebral anchor; 
           [0019]      FIG. 3  is a side elevational view, partially in cross-section, of a spinal fixation construct including a pair of extension members and vertebral anchors as shown in  FIGS. 1-2  being surgically implanted in selected vertebrae of a patient&#39;s spine utilizing an installation tool according to a first embodiment of this invention; 
           [0020]      FIG. 4  is a top view of the arrangement shown in  FIG. 3 ; 
           [0021]      FIG. 5  is a view similar to  FIG. 3  with the spine rod installed and being secured to the vertebral anchors by associated set screws; 
           [0022]      FIG. 6  is a side elevational view of an installation tool according to a second embodiment of this invention delivering a spine rod to a pair of vertebral anchors inserted in respective vertebrae; 
           [0023]      FIG. 7  is a view similar to  FIG. 6  with the installation tool preparing to insert the spine rod into the vertebral anchors; 
           [0024]      FIG. 8  is a view similar to  FIG. 7  with the spine rod installed in position relative to the vertebral anchors; 
           [0025]      FIG. 9  is a side elevational view of an installation tool according to a third embodiment of this invention delivering a spine rod to a pair of vertebral anchors inserted in respective vertebrae; 
           [0026]      FIG. 10  is a view similar to  FIG. 9  with the installation tool preparing to insert the spine rod into the vertebral anchors; 
           [0027]      FIG. 11  is a view similar to  FIG. 10  with the spine rod installed in position relative to the vertebral anchors; 
           [0028]      FIG. 12  is a side elevational view of an installation tool according to a fourth embodiment of this invention adapted to deliver a spine rod to vertebral anchors inserted in respective vertebrae; 
           [0029]      FIG. 13  is a side elevational view of an installation tool according to a fifth embodiment of this invention adapted to manipulate a spine rod into vertebral anchors inserted in respective vertebrae; 
           [0030]      FIG. 14  is a view similar to  FIG. 13  with the installation tool engaged with the spine rod; 
           [0031]      FIG. 15  is a front elevational partial view of the embodiment of  FIGS. 13-14  with the tool adapted to engage a range of spine rod sizes; 
           [0032]      FIG. 16  is a side elevational view of an installation tool according to a sixth embodiment of this invention adapted to manipulate a spine rod into vertebral anchors inserted in respective vertebrae; 
           [0033]      FIG. 17  is a view similar to  FIG. 16  with the installation tool engaged with the spine rod; and 
           [0034]      FIG. 18  is a side elevational view of an installation tool according to a seventh embodiment of this invention adapted to manipulate a spine rod into vertebral anchors inserted in respective vertebrae. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0035]    Referring to the drawings, various embodiments of spine rod or connecting element installation tools to assist in a minimally invasive surgery to install a spinal fixation construct and associated installation methods are shown. In  FIG. 3 , an exemplary spinal fixation construct  10  includes a number of vertebral anchors  12  which in one embodiment are each pedicle screw assemblies, each of which is inserted into selected vertebrae  14  of a patient. The pedicle screw assemblies  12  are joined together in the spinal fixation construct by a connecting element  16  which in one embodiment is a spine rod. The connecting element  16  may be something other than a rigid rod according to alternative embodiments of this invention. According to various aspects of this invention, the individual pedicle screw assemblies  12  may be inserted into the patient through discrete and often individual incisions  18  in the patient&#39;s skin  20 . In certain instances, a single incision  18  such as a minimally invasive incision may be available to provide installation of multiple pedicle screw assemblies  12  in adjacent vertebrae  14 . The small, discrete incisions  18  provide the opportunity for insertion of a cannulated pedicle screw via a K-wire (not shown) inserted through the incision  18  to the precise location on the vertebrae  14  for proper installation of the pedicle screw  12 . While cannulated and other pedicle screw assemblies are contemplated and described herein, one of ordinary skill in the art will appreciate that other types of vertebral anchors and vertebrae engaging mechanisms can be utilized such as hooks for anchoring the connecting element  16  to the patient&#39;s spinal column. 
         [0036]    As shown generally in  FIGS. 1-3 , the vertebral anchor  12  according to one embodiment of this invention includes a pedicle screw  12  having a threaded shaft  22  and a distal tip  24  for insertion and stable positioning into the pedicle area of the patient&#39;s vertebrae  14 . The pedicle screw  12  shown herein is a polyaxial pedicle screw in which a polyaxial body  26  mounted opposite from the distal tip  24  of the screw  12  to a screw head  28  provides for a variety of orientations of the polyaxial body  26  relative to longitudinal axis of the screw  12  as is common with many pedicle screw systems. The polyaxial body  26  coupled to the pedicle screw head  28  includes a saddle or U-shaped channel  30  ( FIG. 4 ) formed between a pair of spaced arms  32  extending upwardly. The polyaxial body  26  is adapted to receive the spine rod  16  in the saddle or U-shaped channel  30  and the spine rod  16  is securely retained by the polyaxial body  26  via a fastener such as a set screw  34  ( FIG. 5 ) threadably received therein as is common with many known pedicle screw systems. 
         [0037]    The various embodiments of this invention may be used in conjunction with an extension member  36  projecting upwardly from the vertebral anchor polyaxial head  26  as shown in  FIGS. 1-5 . Examples of such extension members are disclosed in U.S. patent application Ser. No. 11/567,238, filed Dec. 6, 2006, assigned to the assignee of this invention and hereby incorporated by reference entirely. Exemplary extension members  36  for use on the vertebral anchors  12  are shown herein with certain features, but other configurations and designs are readily utilized with this invention. The extension members  36  project through the incision  18  such that a distal end  38  of the members  36  is located percutaneously above the patient&#39;s skin  20  when the anchor  12  is inserted into the vertebrae  14  as shown in  FIG. 3 . 
         [0038]    Embodiments of extension members  36  according to this invention are shown particularly in  FIGS. 1-5 . The extension members  36  are each elongate and adapted to extend percutaneously from the body when the anchor  12  is secured to the patient&#39;s vertebrae  14 . The elongate extension member  36  may include an elongate tubular sleeve having a generally arcuate sidewall  40  with a generally circular cross-sectional configuration. The extension member  36  has a first more proximal end  42  adapted to be coupled to the anchor head  26  and the second or distal end  38  adapted to be positioned percutaneously for access to the anchor head  26  through a primary lumen  44  formed by the arcuate sidewall  40  of the extension member  36 . Other shapes of lumen  44 , such as square, oval or rectangular, may be used to provide access to the anchor head  26 . As shown in  FIG. 1 , the extension member  36  includes slots  46   a ,  46   b  positioned diametrically opposite from one another. 
         [0039]    Referring particularly to  FIGS. 2 and 3 , a socket  48  is formed on the interior of a flange  50  on the distal end  38  and is sized and configured to mate with the anchor head  26  when the extension member  36  is mounted to the anchor  12 . In one embodiment of the invention, the socket  48  has a generally upwardly tapered configuration with a throat or entry region  52  being more narrow than the upper portion of the socket  48 . This contour corresponds generally to the contour of the anchor head  26  thereby providing a snug and secure mating relationship as shown generally in  FIGS. 2-3 . 
         [0040]    One aspect of the extension member  36  according to this invention is one or more slits  54  in the flange  50  which allow the flange  50  to temporarily expand or deform while the extension member  36  is being coupled to or uncoupled from the anchor  12 . As shown most clearly in  FIGS. 2-3 , the flange  50  includes a number of the slits  54 . In alternative embodiments, any number and/or configuration of sized or shaped slits can be used to provide for the desired deflection characteristics. The slits  54  allow the flange  50  of the extension member  36  to temporarily expand as the throat  52  of the extension member  36  passes over the outwardly tapered distal portion of the anchor head  26 . Continued downward movement of the extension member  36  allows the larger diameter portion of the anchor head  26  to enter into the larger diameter portion of the socket  48  in the flange  50  and the reduced neck region of the anchor head  26  seats within the reduced diameter throat  52  of the flange  50 . The slits  54  allow the flange  50  to expand outwardly until the anchor head  26  is seated within the socket  48  as shown in  FIG. 5 . At that time, the slits  54  allow the flange  50  on the extension member  36  to relax into a mating configuration with the anchor head  26 . The extension member  36  may have a telescoping construction such that an outer sleeve  40   a  is slidable relative to an inner sleeve  40   b . The outer sleeve  40   b , when coupled to the inner sleeve  40   a  as shown in  FIG. 3 , restricts the expansion of the slits  54 . 
         [0041]    While the anchor head  26  and the socket  48  are shown and described as having tapered, mating configurations, other configurations and designs are envisioned within the scope of this invention to provide a selectively retained fit between the extension member  36  and the anchor head  26 . 
         [0042]    Similar to other previously described embodiments of this invention, once the extension member  36  is seated on the anchor head  26 , various components may be inserted through the lumen  44  formed in the extension member  36  toward the anchor head  26  for installation onto the vertebral anchors  12  on the spinal fixation construct  10 . The set screw  34  may be inserted through the lumen  44  for mating with the anchor  12  as shown in  FIG. 5 . 
         [0043]    An alternative embodiment of an extension member  36   a  according to this invention is shown in  FIGS. 1-3  and includes a generally U-shaped member  56  that acts as a guide and is positioned near the distal end  38  of the extension member  36   a  at a radial or laterally offset position on an outer side of the sidewall  40 . The U-shaped member  56  defines a recess  58  which is aligned in an offset relationship from the longitudinal axis of the extension member  36   a  and the lumen  44 . The U-shaped member  56  can be formed only at the distal end  42  of, along a portion of, or from the distal end  42  to the proximal end  38  of the extension member  36 ,  36   a . The recess  58  defined by the U-shaped member  56  allows for a connecting element, such as the spine rod  16 , to be inserted along with an associated connecting element insertion tool  60  through the incision  18 . Advantageously, the recess  58  provides a guide offset from the lumen  44  to direct the position of the connecting element  16  without obscuring the lumen  44  of the extension member  36  to provide visualization of the placement of the rod  16  and so that the other components, such as the set screw  34 , may be inserted through the lumen  44  to the vertebral anchors  12  without requiring removal of rod  16  insertion instrumentation. The recess  58  may also provide for instrumentation to be passed and removed at any time throughout the spinal construct installation procedure. 
         [0044]    One embodiment according to this invention of a connecting element installation tool  60  is shown in  FIGS. 3-5 . The installation tool  60  includes an elongate member  62  having a proximal end  64  spaced from a distal end  66 . The tool  60  includes a handle  68  configured to be grasped by the surgeon for manipulation of the tool  60 . The handle  68  is located at the proximal end  64  of the elongate member  62 . A connecting element retainer  70  is located proximate the distal end  66  of the elongate member  62  and is configured to selectively retain the connecting element, spine rod  16  or other component of the spinal fixation construct  10  for insertion through the incision  18  and toward the vertebral anchors  12 . The connecting element retainer  70  according to this embodiment of the tool  60  holds one end  16   a  of the connecting element or spine rod  16  so that the elongate member  62  of the tool  60  is generally perpendicular to the orientation of the spine rod  16 . As such, the spine rod  16  is initially inserted through the incision  18  relative to the recess  58  of the extension member in a direction generally parallel with the axis of the primary lumen  44  and may be laterally offset from the lumen  44  as shown in  FIGS. 3 and 4 . Once the leading end  16   b  of the spine rod  16  mounted on the installation tool  60  reaches the vertebral anchor  12 , the spine rod  16  and installation tool  60  are reoriented in the direction of arrow A of  FIG. 3 . Available space and access for the reorientation procedure is provided by the slots  46  of the extension members  36  and the recess  58 . Advantageously, once the spine rod  16  is inserted through channels  30  of the heads  26  of the vertebral anchor  12  and seated relative to the vertebral anchors  12 , the installation tool  60  may be positioned in the recess  58  as shown in  FIG. 5  so that set screws  34  or other components of the spinal fixation construct  10  may pass through the lumen  44  of the extension member  36  for direct access to the vertebral anchor heads  26  and secure retention of the connecting element or spine rod  16  relative to the vertebral anchor heads  26 . Once the connecting element  16  is appropriately positioned and/or secured to the vertebral anchors  12 , the installation tool  60  can be disengaged from the spine rod  16  for removal from the patient and the extension member  36 ,  36   a.    
         [0045]    Another embodiment of a connecting element installation tool  160  according to this invention is shown in  FIGS. 6-8  in which components of the invention which are the same as or similarly corresponding components in other embodiments of this invention are identified by the same or similar reference numerals. The installation tool  160  according to this embodiment includes the elongate member  162  having a proximal end  164  spaced from a distal end  166  and a handle  168  located at the proximal end  164  of the elongate member  162  for manipulation of the tool  160 . A second elongate member  172  also having a proximal end  174  spaced from a distal end  176  and a handle  178  located at the proximal end  174  is also includes in this embodiment. The two elongate members  162 ,  172  are pivotally coupled together by a pin  180  located between the proximal and distal ends of the members. Each of the elongate members includes a jog  182 ,  184  at which the pivot pin  180  coupling the members  162 ,  172  together is positioned. As such, the installation tool  160  according to this embodiment is a scissor-like instrument such that movement of the proximal ends  164 ,  174  of the members  162 ,  172  toward and away from each other likewise moves the distal ends  166 ,  176  of the members  162 ,  172  toward and away from each other. 
         [0046]    As shown in  FIG. 6 , the connecting element  16  is held by the installation tool  160  by the connecting element retainer  170  located at the distal end  166  or  176  of one of the elongate members  162  or  172 . The retainer  170  of this embodiment  160  is combined with a pivoting mechanism  186  and the combination includes a pivot pin or set screw  188  at the distal end  166  of the elongate member  162 . The connecting element  16  is generally aligned with the longitudinal axis of the installation tool  160  as shown in  FIG. 6  for insertion through the incision  18  relative to the extension member  36  on one of the vertebral anchors  12 . For simplicity and clarity, the extension members  36  are omitted from  FIGS. 6-8 , but it should be readily appreciated that the installation tool  160  according to this and other embodiments of this invention shown and described herein are capable of being used in combination with the extension members  36  as with the embodiment  60  shown in  FIGS. 3-5 . 
         [0047]    The installation tool  160  is inserted through the incision  18  toward the vertebral anchor  12  in a collapsed configuration as shown in  FIG. 6  with the connecting element  16  generally aligned with the longitudinal axis of the installation tool  160 . Once the installation tool  160  and connecting element  16  are positioned as shown in  FIG. 6 , the handles  168 ,  178  at the proximal end of the tool  160  are separated as is the distal ends  166 ,  176  of the elongate members  162 ,  172  as shown in  FIG. 7 . Coincident with the separation of the ends of the installation tool  160 , the connecting element  16  pivots via the pivot mechanism  186  downwardly to a position shown in  FIG. 7 . With the distal end  176  of the second elongate member  172  juxtaposed to the vertebral anchor head  26 , the free end  16   b  of the connecting element  16  is aligned with a passage  190  in the distal end  166  of the first elongate member  162 . To maneuver the rod  16  into its position as shown in  FIG. 7 , a separate instrument (see  FIGS. 13-17 ) may be utilized alone or in conjunction with the installation tool  160  to apply force on the free end  16   b  of the rod  16  until it is positioned in a proper orientation as shown in  FIG. 7 . 
         [0048]    With the connecting element  16  positioned as shown in  FIG. 7 , the handles  168 ,  178  of the installation tool  160  are squeezed together such that the proximal ends  164 ,  174  are forced together as are the distal ends  166 ,  176  of the tool  160 . The connecting element  16  as such will then pierce through the tissues between the pedicle screws  12  until the handles  168 ,  178  are juxtaposed against each other and the installation tool  160  is closed and the connecting element  16  is inserted into the channels  30  of the vertebral anchor heads  26  as shown in  FIG. 8 . Once the connecting element  16  is positioned in the vertebral anchor heads  26 , the installation tool  160  is disengaged from the connecting element by, for example, unscrewing the set screw or pin  188  at the distal end of the elongate member. Advantageously, the set screw  188  is positioned in an orientation that is accessible and visible through the extension member  36  in the configuration of  FIG. 8 . 
         [0049]    In the exemplary embodiments shown herein, the connecting element  16  may include markings  17   a ,  17   b  to identify the proper positioning of the connecting element  16  within vertebral anchors  12 . The markings  17   a ,  17   b  allow for visualization of the proper alignment of the connecting element  16  through a lumen in a percutaneous extension member, like through the lumen  44  in extension member  36 . In alternative embodiments, the connecting element  16  can include a single marking that assists in identifying the proper location of the connecting element  16  within the vertebral anchors  12 . The marking can be formed into the connecting member or added onto the surface of the connecting element. 
         [0050]    A further alternative embodiment of the installation tool  260  and associated installation technique is shown in  FIG. 9-11  in which the installation tool  260  includes the first elongate member  262  in which the connecting element retainer  270  and associated pivoting mechanism  286  are provided on the distal end  266  of the member  262 . The second elongate member  272  includes the passage  290  proximate its distal end  276  and the two members  262 ,  272  are pivotally joined together at a pivot point  280  medially positioned on the second elongate member  272 . A lever  292  is pivotally mounted at the proximal end  264  of the installation tool  260 . The elongate members  262 ,  272  are generally aligned along the longitudinal axis of the installation tool  260  along with the connecting element  16  for insertion through the incision  18  and positioning relative to the vertebral anchor head  26  as shown in  FIG. 9 . 
         [0051]    With the components in this configuration, the lever  292  is forced downwardly toward the remainder of the elongate members about a pivot pin  294 . The lever  292  controls the opening and closing of the distal ends  266 ,  276  of the instrument  260  such that downward motion of the lever  292  forces the distal ends apart from the configuration shown in  FIG. 9  resulting in the configuration shown in  FIG. 10  with the connecting element  16  pivoted downwardly with the free end  16   b  of the connecting element  16  positioned for entry into and through the passage  290  and subsequently the channels  30  of the vertebral anchor heads  26 . An additional tool (see  FIGS. 13-17 ) may be utilized to reposition the connecting element  16  from the orientation shown in  FIG. 9  to the orientation shown in  FIG. 10 . 
         [0052]    With the connecting element  16  poised for insertion into the vertebral anchor channels  30  as shown in  FIG. 10 , the lever  292  is pulled upwardly by the surgeon to thereby collapse the distal ends  266 ,  276  of the installation tool  260  and force the connecting element  16  through the passage  290  and into the channels  30  of the vertebral anchor heads  26  resulting in positioning of the connecting element  16  as shown in  FIG. 11 . Once again, access to the connecting element retainer  270  is provided through the extension members  36  to release the connecting element  16  from the installation tool  260  so that the installation tool  260  can then be removed. Set screws  34  will then be installed on the vertebral anchors through the lumen  44  of the extension members  36  similar to the operation shown in  FIG. 5 . 
         [0053]    A further alternative embodiment of an installation tool  360  according to this invention is shown in  FIG. 12 . The elongate member  362  includes a hinge  396  for the connecting element retainer  370  at the distal end  366 . The hinge  396  couples a collar  398  and provides the pivoting mechanism  386  for reorienting the connecting element  16  retained by the collar  398  from a generally vertical position as shown in  FIG. 12  to a horizontal position as shown in phantom lines in  FIG. 12 . The lever  392  at the proximal end  364  of the elongate member  362  controls the orientation of the connecting element  16  and rotation of the hinge  396 . This allows the connecting element  16  to be introduced through the incision  18  and extension member  36  to the vertebral anchor  12  in a vertical orientation generally aligned with the longitudinal axis of the installation tool  360 . The connecting element  16  is then rotated into a generally perpendicular orientation relative to the elongate member  362  for insertion into the channels  30  of the vertebral anchor heads  26 . Once positioned in the generally horizontal orientation shown in phantom lines in  FIG. 12 , the collar  398  is disengaged from the connecting element  16  and the installation tool  360  is removed from the extension members  36  and the incision  18 . The connecting element  16  is then secured to the vertebral anchors  12  by the insertion of the set screws  34  through the lumen  44  of the extension members  36  as shown generally in  FIG. 5 . 
         [0054]    In another aspect of this invention, a tool  460  for manipulating a component of a spinal fixation construct  10  such as the spine rod or connecting element  16  into position relative to the vertebral anchors  12  is disclosed in  FIGS. 13-15 . The tool  460  according to this aspect of the invention includes a first elongate member  462  having a proximal end  464  spaced from a distal end  466  with a handle  468  located at the proximal end  464  and configured to be grasped by a surgeon. A retainer  470  is positioned proximate the distal end  466  of the elongate member and is adapted to selectively hold the component such as the spine rod  16  for installation onto one of the vertebral anchors  12 . The retainer  470  in the embodiment shown in  FIGS. 13-15  is adjustable to accommodate a range of sizes of the component as shown in  FIG. 15 . The distal end  466  of the elongate member  462  may include a generally arcuate recess  500  which cooperates with a corresponding recess  502  in a jaw  504  positioned in opposition to the distal end  466  of the elongate member  462  to form a clamp for retaining the spine rod  16 . The jaw  504  is formed at a distal end  476  of a multi-bar linkage  508  which is pivotally coupled to the elongate members  462 ,  472  as shown in  FIGS. 13 and 14 . 
         [0055]    A first link  510  of the multi-bar linkage  508  is pivotally coupled to the elongate member  462  adjacent the proximal end  464  of the instrument  460 . An opposite end of the link  510  from the elongate member  462  is captured via a pin  512  within a slot  514  of an actuating link  516 . A distal end of the actuating link  516  is pivotally coupled via a pin  518  to the second elongate member  472  as shown in  FIGS. 13-14 . The second elongate member  472  slides relative to the first elongate member  462  as a result of the manipulation of the linkage  508 . As the actuating link  516  is rotated towards the elongate member  462 , the link  510  pivots upwardly thereby pulling the actuating link  516  and an associated sliding link  520  upwardly and closing and pulling the jaw  504  closer to the recess  500  at the distal end  466  of the elongate member  462  and clamping the connecting element  16  therein. A locking mechanism  522  in the form of a rotatable knob may be provided on the sliding link  520  to secure the sliding link  520  relative to the elongate member  462  and lock the clamped connecting element  16  in place during manipulation and insertion of the connecting element  16  to the spinal fixation construct  10 . The position of the jaw  504  relative to the distal end  466  of the elongate member  462  may be adjusted by moving the pin  512  of the link  510  within the slot  514  provided in the actuating link  516  to accommodate different sized connecting elements  16  and thereby adjust the relative position of the sliding link  520  relative to the elongate member  462  during the clamping operation. 
         [0056]    Another embodiment of an installation tool  660  according to this invention is shown in  FIGS. 16-17 . This embodiment is similar to the embodiment shown in  FIGS. 13-15  wherein a multi-bar linkage assembly  608  is utilized in combination with the elongate member  662  to selectively clamp the connecting element  16  with the jaw  604  and the distal end of the elongate member  666 . However, one difference between the embodiment of  FIG. 16-17  relative to the embodiment of  FIGS. 13-14  is that the actuating link  616  is pivotally coupled directly to the elongate member  662  with the link  610  coupled to the actuating link  616  and the sliding link  620 . The clamp  606  is actuated by rotation of the actuating link  616  away from the elongate member  662  as shown in  FIG. 16 . The more collapsed orientation of the linkage assembly  608  provides for more efficient insertion of the instrument  660  through the incision  18 . The clamped orientation of the tool  660  shown in  FIG. 17  provides for manipulation and insertion of the connecting element  16  relative to the vertebral anchor head channels  30  as previously described. 
         [0057]    Another embodiment of a tool  760  according to this invention is shown in  FIG. 18  in which the elongate member  762  includes a lumen  724  extending there through and a handle  768  mounted on the proximal end  764  of the elongate member  762 . The connecting element retainer  770  is pivotally mounted to the distal end  766  of the elongate member  762  via a pivot mechanism  786  joining an arcuate-shaped retainer  770  to the elongate member  762 . A rod capture device in the form of a collar  798  is provided on an end of the arcuate member  770  opposite from the pivot mechanism  786  to thereby capture the connection element  16  for insertion into the channels  30  of the vertebral anchor heads  26 . The connecting element  16  and installation tool  760  may be inserted through the incision  18  in a generally vertical or parallel orientation as shown in phantom lines of  FIG. 18 . Once the connecting element  16  is positioned adjacent the vertebral anchor heads  26 , the pivoting mechanism  786  rotates the connecting element  16  into a generally perpendicular orientation relative to the lumen  724  and longitudinal axis of the elongate member  762  for insertion into the channels  30  of the vertebral anchor heads  26 . Advantageously, the lumen  724  provides access for the set screw  34  to be inserted into the vertebral anchor head  26  for securing the connecting element  16  thereto. The connecting element retainer  770  is then disengaged from the connecting element  16  for removal of the installation tool  760  as previously described. 
         [0058]    As a result of the various embodiments of this invention, a more minimally invasive spinal fixation construct installation tool and procedure is provided by the pedicle screw assemblies, sleeves and associated devices of this invention without the need for extended incision and associated difficulties. Moreover, increased visualization and minimally invasive disruption are realized with this invention. 
         [0059]    From the above disclosure of the general principles of this invention and the preceding detailed description of at least one embodiment, those skilled in the art will readily comprehend the various modifications to which this invention is susceptible. Therefore, we desire to be limited only by the scope of the following claims and equivalents thereof.