CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. national phase application filed under 35 U.S.C. § 371 of International Application PCT/US2006/037789, filed on Sep. 26, 2006, which claims priority from U.S. Provisional Application No. 60/720,955, filed on Sep. 26, 2005, which are hereby incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to An apparatus and method for implanting surgical devices, in particular, for implanting and securing a fixation device to a bone, and, more particularly, to a driving apparatus and method for implanting an anchor of a spinal rod fixation device in a bone. 
     BACKGROUND OF THE INVENTION 
     There are currently a wide array of surgical devices for spinal surgery. One group of these devices includes a fixation device including a screw or hook anchor for securing the device to a vertebrae, such as the pedicle portion of the vertebra. Many of these surgical devices are spinal rod fixation devices and include a coupling portion for receiving or otherwise securing a spinal rod or other elongated member relative to the anchor. Commonly, the coupling portion or yoke is a distinct member from the anchor so that they can take on a plurality of different orientations relative to each other. 
     For example, for a screw anchor member, a threaded shank of the screw anchor is driven into the pedicle portion at a particular angle. At times, the orientation and position of the threaded shank with the vertebra is dictated by the surface geometry or other characteristics particular to the patient and/or to the individual vertebrae. However, the spinal rod that is to be coupled with and fixed relative to the screw anchor has a configuration and position that is dictated more by the goals of the medical procedure. To allow the yoke to receive the spinal rod, while also permitting the desired positioning of the spinal rod, the yoke member may assume a number of orientations relative to the screw anchor so that their respective axes are other than in alignment with each other. 
     During installation, this polyaxial feature presents a number of issues. The coupling member is not secured relative to the screw anchor during insertion. Thus, the coupling member tends to pivot by its own weight as the screw is being driven into the vertebral bone. This can be problematic as the coupling member may interfere with the rotational driving action, such as by binding with the driver and screw anchor, and this interference may inadvertently alter the position and orientation in which the shank is driven. 
     It is desired to minimize the resection required to implant the fixation device and its associated coupling member. In the event that the coupling member tilts or pivots from alignment with the axis of the screw anchor, the coupling member may contact tissues surrounding the implantation site for the fixation device. As the screw member turns with the coupling member tilted to one side, the coupling member may sweep around the implantation site potentially causing damage to surrounding tissues. As is apparent, the polyaxial movement provided between the screw anchor and yoke coupling member can make the driving operation for implanting the screw into the vertebral bone more difficult than is desired. 
     In general, it is preferred to minimize the incision and resection performed on a patient for most operations. For instance, arthroscopy and endoscopes were developed to permit inspection and surgery for interior anatomical portions while avoiding significant incisions through healthy and non-damage tissues. As such, it is also desired to minimize the size of the fixation device including the coupling member thereof during implantation. 
     There are numerous tools devised for implanting the various designs of fixation devices and coupling devices. A prior art device is further known for seating a screw in the pedicle portion of a vertebrae, the screw having an associated coupling device, wherein the prior art device generally stabilizes the coupling device relative to the screw during driving. More specifically, U.S. Pat. No. 6,858,030, to Martin, et al., discloses a driver for implanting a screw of a pedicle screw assembly that includes a polyaxial coupling element. The driver has threads spaced up along its shaft from the lower driver end for being received in internal threads formed along the inner surface of the walls of the coupling element. Internally threading these walls necessitates that the walls be of sufficient thickness for forming threads therein, undesirably increasing the size or width of the coupling element, as well as the height of these walls along which the threads are formed. Seating of the drive prongs in the corresponding recesses of the screw head is difficult due to the need to positively thread the driver into the coupling element. Further, after the screw has been fully implanted in the pedicle of the vertebra, releasing the driver requires it be turned to back the shaft threads out from the coupling element threads, potentially loosening the implanted screw. 
     In fact, the driver and screw head of the &#39;030 patent require a linear engagement, while the shaft is rotated into the coupling element. To achieve this, the coupling element must be rotated relative to both the driver and the screw so that they are drawn together (or forced away) by the coupling element. Disconnection of the shaft and coupling element would require a surgeon&#39;s fingers, or another device, reaching into the implant site and rotating the coupling element a plurality of revolutions. 
     Accordingly, there is a need for a device for an optimized apparatus and method for implanting screw and anchor members of spinal rod fixation devices having a polyaxial coupling member in terms of the ease in which the screw anchor is driven into the vertebral bone. In addition, an apparatus and method for implanting screw anchors is desired that keeps the size of the device, and in particular the coupling member, to a minimum. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect, an apparatus is disclosed for securing with and generally immobilizing in a pre-determined relative orientation an anchor or screw and a pivotable coupling member of a surgical device such as a spinal rod fixation device. In this manner, the coupling device and fixation device can be secured joined or driven into a bone such as a vertebrae without the coupling device and fixation device pivoting relative to each other. By restricting or eliminating the pivoting of the components of the surgical device, the size of the incision into the anatomy and through the surrounding tissues can be minimized, and damage to surrounding tissues as a result of rotating the surgical device is minimized. 
     Each of the coupling device and fixation device has a central longitudinal axis. When secured with the implantation device, the respective longitudinal axes are aligned with each other. The implantation device is received within the coupling device and fixation device so that it does not substantially exceed the profile and size of the surgical device itself. Thus, the surgical device has a single longitudinal axis, and the radial extent of the surgical device is generally that of the components of the surgical device and, typically, the radial extent of the coupling device. Again, securing the components of the surgical device with the implantation device in such a manner minimizes the size of the incision and resection of surrounding tissues. 
     The implantation device also retains the surgical device. During a surgical implantation procedure, the surgical device must be guided through openings made in the surrounding tissues. The implantation device forms a mechanical connection with the surgical device so that, while being manipulated, the surgical device does not separate or fall off the implantation device. As the fixation device is often a screw, a typical screw and screwdriver cooperation commonly requires a surgeon&#39;s hand to hold the screw in engagement with the screwdriver at least until the screw tip is position at a bone surface for receiving the screw therein. The implantation device retains the surgical device, once secured therewith, until it is desired to release the surgical device, such as post-implantation. 
     With a typical screw and screwdriver cooperation, it is also commonly necessary for a surgeon&#39;s hand to position the screw tip at a desired implantation point or region, and to maintain the screw in proper alignment during at least an initial driving of the screw into a bone. The implantation device with the surgical device secured thereto allows a surgeon to use a second, guiding hand if desired by grasping an elongated body of the implantation device. Furthermore, the surgical device being secured is held in general alignment with the implantation device so that the proper alignment for screw itself is maintained. This allows the surgeon to operate without resecting tissues to an extent to permit a hand to be close to the implantation site for holding the screw or maintaining the screw in desired and proper alignment. 
     In accordance with another aspect, release of the implantation device from the implanted surgical device does not affect the position or securement of the surgical device. As noted, the fixation device is commonly a screw rotationally driven into bone such as a vertebra. The discussed prior art utilizes a threaded connection for joining the driver with the coupling element. As such, disconnecting the driver from the coupling element requires counter-rotation from the direction in which the screw is secured with bone. The present implantation device is inserted within and removed from the coupling device in a linear motion so that removal therefrom does not require rotating the implantation device in a manner that may cause the fixation device, or screw, to back out of the bone in which it is secured. Furthermore, a locking actuator member is linearly advanced to shift, generally in a linear direction, locking portions of the implantation device to lock with the surgical device for general immobilization. To release the device, the locking actuator in the form of a rod actuator is simply linearly retracted from the advanced position, thereby allowing the locking portions to release from the surgical device, and then the entire implantation device may be linearly removed from the surgical device. 
     In accordance with a further aspect, the implantation device does not restrict the surgical device to a limited type of closure member. A coupling device used with, for instance, spinal surgery to receive an elongated member such as a spinal rod for securing the rod with the pedicle portion of a vertebra commonly utilizing a pair of walls, or a yoke-like structure, for receiving the spinal rod therein. To retain and secure the spinal rod therein, the yoke is joined with a closure member. While the discussed coupling element of the prior art system utilizes a threaded connection shared by the driver and the closure element, the present implantation device requires only structure in the coupling device for joining with the locking portion of the implantation device. In the preferred embodiment, this structure is a recess for receiving the locking portion. In a more preferred embodiment, this recess is also utilized by other tools or devices, such as a rod persuader used for seating the spinal rod within the yoke walls and/or a tool for directing and securing the closure member for connection with the surgical device. Accordingly, the structure provided between and on the yoke walls is not dictated by the connection required by the implantation device, and the interior of the yoke walls may be provided with a connection structure for receiving a closure member therebetween, particularly a non-threaded connection structure. 
     The present implantation device, accordingly, further permits the avoidance of threaded connections between closure members and coupling devices. It is presently believed that a threaded connection requires a greater axial length for the coupling device to be properly and securely joined with the closure member. The use of threads by the prior art system therefore requires a greater axial length then other connection designs, and this greater axial length increases the size of the surgical device and increases the effects of the surgical device when implanted in a body with surrounding tissues and with bio-mechanical motion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a driver apparatus coupled to a spinal rod fixation device at a lower drive end portion of the apparatus; 
         FIG. 2  is an exploded perspective view of the driver apparatus and fixation device of  FIG. 1  showing components of the driver apparatus for coupling with an anchor member and with a coupling member of the fixation device; 
         FIG. 3  is an enlarged side view of a distal portion of the driver end portion showing side arms fitting in openings of the coupling member and one of a pair of holding lugs in an associated slots of the coupling member; 
         FIG. 4  is a fragmentary side elevational view of the driver end portion showing drive prongs engaged recesses in the screw head; 
         FIG. 5  is a first side elevational view of the driver showing a driver body and a pair of spaced-apart extensions extending from the body; 
         FIG. 6  is a side elevational view of the driver rotated ninety degrees from the position of  FIG. 5  and showing the profile of the extensions for being received between the upstanding walls of the coupling member; 
         FIG. 7  is an end view of the driver showing drive prongs for cooperating with the fixation device for driving the fixation device into a bone, and showing a central longitudinal bore through the driver body; 
         FIG. 8  is a perspective view of the fixation device in the form of a screw having a threaded shank, and a head having a plurality of recesses for cooperating with the driver engagement structure; 
         FIG. 9  is a second side elevational view rotated ninety degrees from the position of  FIG. 3  showing the coupling member, the screw anchor, and the driver extensions received between the upstanding walls of the coupling member; 
         FIG. 10  is a cross-sectional view corresponding to  FIG. 9  showing the drive prongs engaged within the screw head recesses; 
         FIG. 11  is a side elevational view of a locking member having a body and locking extensions extending from a distal end thereof, a rod actuator including an end configured for forcing the locking extensions outward for engaging lugs thereon within the upstanding wall recesses, the driver in phantom, and the coupling member with the screw inserted therein; 
         FIG. 12  is a cross-sectional view showing the lugs positioned between the upstanding walls for being received by the recesses thereof; 
         FIG. 13  is a cross-sectional view corresponding to  FIG. 12  showing the rod actuator and locking member in a locked position, the rod actuator being advanced to force the locking member extensions outward such that the lugs engage with the upstanding wall recesses; 
         FIG. 14  is a perspective fragmentary view of a proximal end of the apparatus showing the locking member body and a handle for selecting the position of the rod actuator for locking and unlocking the locking apparatus with the fixation device; 
         FIG. 15  is a fragmentary cross-sectional view of the locking member body having a slot receiving a pin secured with the rod actuator, and the handle secured on the pin and on a shoulder formed on the locking member body such that movement of the handle in a longitudinal direction of the locking member body shifts the rod actuator between the locked and unlocked positions; 
         FIG. 16  is a fragmentary perspective view of the proximal end showing a first handle portion having an annular portion threadably received by a sleeve handle portion, the handle portions securing the pin therebetween; 
         FIG. 17  is a perspective view of the first handle portion showing the pin abutting a shoulder formed within the annular portion, and the pin received within a bore of the rod actuator; and 
         FIG. 18  is a perspective view of the sleeve handle portion showing the pin abutting a shoulder formed within the sleeve. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring initially to  FIG. 1 , a driving apparatus  10  is depicted for securing a fixation device  12  to a bone such as a vertebra. The implantation device  10  includes a proximal end portion  14  coupled with an operator handle (not shown) and a distal drive end portion  16  for being coupled with the fixation device  12 . 
     The driving apparatus  10  includes a locking member  20  having a body  22  extending between the proximal end  14  and the distal end  16 . The locking member  20  adjacent the proximal end  14  includes a non-circular end portion  24  for joining with the operator handle. For instance, the operator handle may include a socket (not shown) for receiving the end portion  24  so that rotation of the operator handle effects rotation of the locking member  20  and the implantation device  10 . 
     The locking member body  22  is generally fixed with the drive end portion  16  of the apparatus  10  so that they are fixed for rotating together so that turning of the locking member  20  causes turning of the drive member  50  including drive prongs  64  thereof about a central axis. As shown, the drive end portion  16  is a driver member  50  connected to a distal end  108  of the locking member  20 . In the illustrated form, the locking member body  22  includes a recess  26  such as a notch cut into the side of the locking member body  22  so as to form a surface  28 , which is preferably flat. The driver  50  includes a cylindrical body  52  defining an internal bore  54 . The driver body  52  has a pair of bores  56  aligned with each other and to one side of the central longitudinal axis, that is, offset from a diameter of the driver body  52  and the locking member body  22 . The locking member body  22  is inserted into the driver bore or cavity  54  such that the recess  26  is aligned with the bores  56 . The driver  50  and locking member  22  are then generally secured relative to each other by inserting a pin  30  through the bores  56  and into the recess  26  so as to abut the surface  28 . In this manner, the driver  50  and locking member  20  may not be separated or rotated relative to each other without removal of the pin  30 . 
     The driver  50  engages the fixation device  12  to secure the fixation device  12  with a bone such as a vertebra. In the illustrated form, the fixation device  12  includes an anchor member  70  and a coupling member  90  wherein the anchor member  70  and coupling member  90  are polyaxially coupled and pivotable relative to each. The anchor member  70  may be secured with the vertebra in a position and orientation dictated by the vertebral surface or structure, as well as by access provided to the implantation site on the vertebra. Being polyaxially coupled to the anchor  70 , the coupling member  90  maybe positioned and/or oriented relative to the anchor  70  as desired by a surgeon. For instance, the coupling member  90  includes a base  92  and a pair of upstanding walls  94  together defining a channel  96  into which an elongated member such as a spinal rod (not shown) may be seated for coupling together a plurality of fixation devices  12 , and the position of the coupling member  90  may be dictated by the necessary position for the spinal rod. 
     As shown, the anchor  70  is in the form of a screw, though a hook or other device for securing with a bone may alternatively be used. The screw  70  includes a threaded shank  72  for being driven into and secured with the vertebra, a head  74 , and a neck  76  extending therebetween. The neck  76  may be cylindrical or may be slightly tapered. The head  74  includes a bottom arcuate surface  78  for seating within the coupling member  90 , as will be discussed below, and has a top surface  80  oriented and configured for engaging the driver  50 . 
     As can be seen in  FIGS. 4-8 , the driver  50  and screw head top surface  80  have cooperating structure allowing the driver  50  to rotational drive the screw head  74  into the vertebra. In the preferred embodiment, the head top surface  80  includes a central recess  82  aligned with a screw central longitudinal axis for receiving a pivoting insert  32  for engaging a spinal rod received in the channel  96  regardless of relative orientation between the coupling device  90  and the screw  70 . The head top surface  80  includes a number of drive engagement recesses  84  radially oriented from the screw central axis and central recess  82 . The engagement recesses  84  are preferably rectangular in cross-section, though other shapes may be employed. 
     It should be noted that  FIG. 8  depicts the screw head  74  including a plurality of stakes or tabs  88  surrounding and extending over the central recess  82 . During assembly, the tabs  88  extend away from the screw head top surface  80  generally parallel to the longitudinal axis of the screw  70 . The pivotable insert  32  is positioned in the central recess  82 , and the tabs  88  are then deformed to the position shown in  FIG. 8  to retain the insert  32  therein while permitting the insert  32  to pivot as desired. 
     The driver  50  mates with the screw head engagement recesses  84  to provide rotational drive to the screw  70 . A distal end  58  of the driver  50  includes a plate  60  from which engagement structure  62  protrudes. In the depicted form, the engagement structure  62  includes a plurality of engagement prongs  64  with a shape corresponding to the screw head engagement recesses  84 , such as rectangular in cross-section. As can be seen in  FIG. 7 , the plate  60  includes a depression or recess  66  along a driver central longitudinal axis, the driver  50  thereby allowing clearance for the insert  32  received within the screw head central recess  82  and the crest of the screw head top surface  80  from which the insert  32  may slightly protrude. Accordingly, the mated prongs  64  and engagement recesses  84  require the co-rotation of the driver  50  and the screw  70 . 
     To enable the driver engagement structure  62  to mate with the screw head recesses  84 , the driver distal end  58  is configured for being received in the channel  96  and between the upstanding walls  94 , as can be seen in  FIG. 9 . The driver  50  includes a pair of extensions  68  extending from the driver body  52 . The extensions  68  terminate at and join with the driver plate  60 . As shown, the extensions  68  are dimensioned to have a width for closely fitting within and between the upstanding walls  94 . Thus, the extensions  68  and upstanding walls restrain relative movement between the driver  50  and coupling device  90 . Since the extension  68  fit in the channel  96  between the walls  94 , they will engage one side or the other along the channel  96  openings when the driver  50  is turned, depending on the turning direction, so that the coupling member  90 , along with the engaged screw anchor  70 , turn therewith. In addition, the extension  68  stop the coupling member  90  from pivoting relative thereto, and the engaged screw anchor  70  keeping the coupling member and screw anchor  70  in a substantial co-axial direction. 
     As noted above, the implanted screw  70  and coupling member  90  may pivot polyaxially relative to each other for receiving a spinal rod having a desired orientation. Towards this end, the head  74  includes the bottom arcuate surface  78  for seating within the coupling member  90 . As shown in  FIG. 10 , the coupling member base  92  includes a bore  98  aligned with a central axis of the coupling member  90  and a seat  100  surrounding the bore  98 . The screw  70  is inserted through the channel  96  so that the threaded shank  72  extends through the bore  98 . In general, the contour of the screw head bottom surface  78 , the contour of the seat  100 , a diameter of the neck  76 , and the size and shape of the bore  98  determine the amount of polyaxial motion permitted between the screw  70  and the coupling member  90 . During implantation, the coupling member  90  and the screw  70  are aligned along their central longitudinal axes so as to be in the configuration shown in  FIG. 10 . It is noted that the coupling member  90 , the screw  70 , and the driver  50  are configured so that, when the driver  50  is engaged with the screw  70 , the extensions  68  of the driver  50  restrict pivoting of the coupling member  90 . 
     The fixation device  12  preferably restricts the ability for the coupling member  90  to shift downward along the screw shank  72 . That is, the fixation device  12  includes a retainer  34  inserted within the coupling member  90  in a position to restrict the screw  70  from moving into the channel  96 . More specifically, the retainer  34  includes a peripheral or ring portion  36  and retention structure  38  extending outward from the ring  36 . The screw  70  is inserted through the bore  98  so that the screw head bottom surface  78  is positioned on or near the seat  100 , and the retainer  34  is inserted through the channel  96  so that the ring portion  36  rests on a peripheral portion  86  of the screw head top surface  80 . During insertion, the retainer  34  is compressed slightly to provide clearance for the retention structure  38 . At a predetermined depth of insertion for the retainer  34 , the retention structure  38  aligns with ports or other recesses  102  located on the interior of the upstanding walls  94 , as can be seen in  FIG. 10 . The retainer  34  is resiliently deformable to permit the polyaxial motion described above for the coupling member  90  and the threaded shank  70 , and may be deformed either prior to insertion or due to insertion to restrict the coupling member  90  from falling down the screw shank  72 , as shown in  FIG. 10 . 
     After the driver  50  is engaged with the screw  70 , the locking member  20  is interlocked with the coupling member  90  to generally immobilize the coupling member  90  relative to the screw  70 . A distal end  108  of the locking member  20  includes a pair of extensions or arms  110  extending from the locking member body  52  and between the coupling member walls  94 . The arms  110  have lugs  112  extending laterally or radially outward therefrom a short distance. The driver  50  is inserted within the coupling member  90  to a predetermined depth to bring the lugs  112  into alignment with recesses or ports  114  formed in the coupling device walls  94 , as shown in  FIG. 12 . The retainer  34  permits the polyaxial movement between the screw  70  and coupling member  90 , it may be necessary to draw the coupling member  90  towards the proximal end  14  of the driving apparatus  10  to achieve the proper alignment of the lugs  112  with the ports  114 . 
     With the drive prongs  64  received in the drive recesses  84  of the screw head  74 , the longitudinal axes of the screw  70  and coupling device  90  will be in substantial alignment. This alignment then allows the lugs  112  to be aligned with the ports  114  for being pushed through and holding the coupling member  90  against shifting relative to the drive member  50 , as shown in  FIG. 13 . 
     The fixation device  10  utilizes an actuating rod  120  cooperating with the locking member  20  to direct the lugs  112  into the ports  114 . The actuating rod  120  may be shifted between extended and retracted positions corresponding to locked and unlocked configurations for the driver apparatus  10  with the fixation device  12 . The unlocked configuration is illustrated in  FIG. 12  with the lugs  112  positioned outside of the coupling member wall ports  114 , while the locked configuration is shown in  FIG. 13  with the lugs  112  received within the ports  114 . 
     The locking member  20  includes a central longitudinal bore  130  within which the actuating rod  120  is received. The actuating rod  120  may be reciprocated or actuated for movement along its longitudinal axis to and between the retracted and advanced positions. As noted, the arms  110  extend from the locking member body  52 , and they are positioned generally to permit reciprocation of the actuating rod  120  therebetween. However, the arms  112  have respective inboard sides  132  facing each other. Each inboard side  132  includes a ramp surface  134  extending inwardly in the distal direction and towards the respective ramp surface  134  of the opposed arms  114 . Each ramp  134  terminates at a flat  136  positioned generally on the inboard side  132  opposite the lugs  112 . 
     To lock the lugs  112  in the ports  114 , the actuating rod  120  wedges against the ramps  134 . The actuating rod  120  has a generally cylindrical body  122  with a terminal end  124  which may be conical or wedge-shaped to have at least a portion  126  angled from the body  122  and positionable against each of the ramps  134 . As the actuating rod  120  is advanced towards the fixation device  12  with the driver apparatus  10  secured thereto, the angled portions  126  bear against and wedge outward the ramps  134  and their associated arms  110  and lugs  112 . The actuating rod  120  may be advanced to the locked position in which the lugs  112  are positioned within the ports  114  and the cylindrical body  122  is positioned against and between the flats  136  of the opposed arms  110 . More specifically, as the actuating rod  120  is advanced forward, it bottoms out on the driver  50 . The engagement of the actuating rod  120  causes the lugs  112  to flex or shift laterally into the parts  114  of the coupling member in order to lock the apparatus thereto. 
     When moving from the locked position to the unlocked position, the locking rod  120  is retracted. As the locking rod  120  moves away from the ramps  134  and flats  136 , the arms  110  and associated lugs  112  shift inward so that the lugs  112  are released from the ports  114 . To enable this motion, the arms  110  have a flexibility so that, when the locking rod  120  is retracted, the arms  110  shift inward to a natural position. The treading of the actuator rod  120  to the locking member  20  searves to generally retard or inhibit unintentional retraction of the actuating rod  20 . 
     Referring now to  FIGS. 14-18 , the driver apparatus  10  includes a handle or grip  150  for selecting the position of the actuating rod  120  and, thus, the unlocked and locked positions of the driver apparatus  10  with the fixation device  12 . As noted above, the actuating rod  120  is received within a bore  130  of the locking member body  22 . The bore  130  extends from the arms  110  to a position rearward sufficient for locating the handle  150  on the locking member  20 . Preferably, at least one slot  152  is formed in the side of the locking member body  22  at a position desired for generally locating the handle  150 . As illustrated, a pair of slots  152  are aligned with each other across a diametral line of the locking member body  22 . 
     The actuating rod  120  includes a pinned portion  160  is which positioned between the slots  152  when the actuating rod  120  is in the advanced, locked position. The pinned portion  160  includes a throughbore  162  for receiving a pin  164  therethrough. The pin  164  has ends  166  extending through the slots  152  when assembled. The slots  152  may be sized so that the pin  164  contacts a front edge  154  of the slot  152  when the actuating rod  120  is fully extended. The slots  152  should also be sized so that the pin  164  may shift sufficiently therein to permit full retraction of the actuating rod  120  from between the ramps  134  and flats  136  of the locking member arms  110 . 
     The grip member  150  secures with the pin  164  for shifting the actuating rod  120  between the locked and unlocked positions. The grip  150  includes an outer grip portion  170  and an inner grip portion  200  secured together to capture the ends  166  of the pin  164 . The outer grip portion  170  is a sleeve-like member defining an internal cavity  172 . The cavity  172  includes a first portion  174 , a second portion  176 , and a third portion  178  along its axial length. The first portion is sized closely to the locking member body  22 , though with appreciable clearance so that the first portion  174  may use the locking member body  22  as a guide for relative movement without becoming bound therewith. 
     The second portion  176  of the outer grip cavity  172  is larger in diameter than the first portion  174  so a radial shoulder  180  is formed therebetween. The locking member body  22  includes an enlarged diameter section  182 . When assembled, the enlarged section  182  is generally positioned within the second cavity portion  176 . When the handle  150  and actuating rod  120  are retracted, the shoulder  180  may serve as a stop indicating full retraction thereof. 
     The outer grip third cavity portion  178  ( FIG. 18 ) has a larger diameter than the second portion  176  so that the junction therebetween forms a second shoulder  184 . As can be seen in  FIG. 18 , the pin  164  is positioned against the shoulder  184  and within the third portion  178  when assembled. More particularly, the pin  164  and its ends  166  are positioned within an internally threaded annular portion  186  extending about the third cavity portion  178 . 
     The inner and outer grip portions  170 ,  200  capture the pin ends  166  therebetween. The inner grip portion  200  has a cavity  202  having a first portion  204  sized to utilize the locking member body  22  as a guide, and a second portion  206  sized so that the annular wall  208  extends about the pin  164 . The annular wall  208  is externally threaded so that it may be threadably joined to the internally threaded annular wall portion  186  of the outer grip portion  200 . The second cavity portion  206  is larger in diameter than the first cavity portion  204  so that a shoulder  210  is formed between the two cavity portions  204 ,  206 . When the inner and outer grip portions  170 ,  200  are threaded together, the pin  164  is positioned and captured between the shoulders  184 ,  210 . Accordingly, when the grip  150  is slidably moved along the locking member body  22 , it causes the actuating rod  120  to reciprocate between the locked and unlocked positions with the pin  164  traveling in the guide slots  152  of locking member body  22 . The pin  164  is a guide pin that cooperates with the guide slots  152  to define limits of retracting and advancing movements of the actuating rod  120 . 
     In operation, the driver apparatus  10  is inserted by linear motion directly into an upwardly facing opening of the coupling member  90  so that the driver  50  engages with the screw  70  with the prongs  64  received in the engagement recesses  84  of the screw head  74 , the coupling member  90  and screw will be co-axially oriented and the locking lugs  112  will be aligned with the ports  114  of the opposed coupling member walls  94 . The actuating rod  120  is then advanced forward, towards the screw  70 , to force the lugs  112  into engagement with the coupling member ports  114  and to lock the coupling member  90 , screw  70 , and driver apparatus  10 . The entire assembly may then be rotated to drive the screw  70  into the vertebra. To disconnect the driver apparatus  10  from the implanted fixation device  12 , the actuating rod  120  is retracted to release the lugs  112  from the ports  114 . The driver apparatus  10  may then be retracted by linear motion. Accordingly, the motions for disconnecting the driver apparatus  10  from the implanted fixation device  12  do not require rotation that may otherwise back the screw  70  out of the vertebra. 
     While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques that fall within the spirit and scope of the invention as set forth in the appended claims.
A driver apparatus for implanting spinal rod fixation devices including an anchor member and a coupling member pivotable relative to the anchor member is disclosed. The driver apparatus generally immobilizes the anchor member and coupling member relative to each other and to the driver apparatus during insertion to minimize interference between the coupling member and tissues surrounding the implantation site, as well as to minimize the clearance required for implantation. The driver apparatus includes a driver portion engageable with the anchor member for effecting seating of the anchor member, such as by threadably driving the anchor member in the bone. The driver portion is closely fit between portions such as upstanding walls of the coupling member to prevent relative rotation therebetween. The driver apparatus further includes locking portions shiftable to secure the coupling member with the driver apparatus when the driver is engaged with the anchor member.