Abstract:
A minimally invasive and open surgery surgical system for implanting spinal screw assemblies to be connected by a spinal rod is disclosed. In one form, the system includes an improved tool device for inserting a cap insert into an initial and final locking of a screw assembly and securing a spinal rod inserted through an incision to a vertebra. In another form, the system also includes a screw fixation system that allows greater variability in thread diameter for orthopedic implant for in the spine, iliac crest, or bones.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This patent claims benefit under 35 U.S.C. §119 (e) to U.S. Provisional Application No. 61/304,123 entitled “Spinal Rod and Screw Securing Apparatus and Method” filed Feb. 12, 2010, the contents of which are incorporated herein by reference in its entirety. 
     INCORPORATION BY REFERENCE 
     U.S. Utility application Ser. No. 11/844,259, filed Aug. 23, 2007 and entitled MINIMALLY INVASIVE SURGICAL SYSTEM, is incorporated by reference as if reproduced in its entirety, herein. 
    
    
     FIELD OF THE INVENTION 
     The device disclosed herein provides an instrument for manipulating and securing bone fixation systems for the promotion of proper bone alignment and fusion, in particular, spinal fusion. In the preferred embodiment, the drive tool apparatus is similar to the class of medical instruments generally referred to as rod persuaders, spinal rod reducers and pedicle screw cap inserters, but is not limited to that class of devices. 
     The invention also relates generally to an apparatus and method for surgically implanting a fixation device, more particularly, to an apparatus and surgical method that secures bone or bone segments relative to one another with minimal invasion into the surrounding body tissue. Conversely the present invention is also compatible with conventional “open” surgical approaches for the treatment of more serious trauma injuries, or diseases such as scoliosis. 
     BACKGROUND OF THE INVENTION 
     Implant devices secured to bone or bone segments are utilized to promote the healing and repair of various parts of the human body. In some cases, the implant devices are secured to bone or bone segments such that the bones themselves heal, fuse, or stabilize relative to one another. In other cases, implant or fixation devices are used to secure bones or bone fragments such that the surrounding soft tissue may heal without being disturbed by relative movement of the bones. 
     During the surgical procedure to implant fixation devices, a plurality of bone screws or other fixation elements, in concert with coupling members, are secured to a plurality of respective bones. Each of the bone screws, or anchor members, is then secured relative to the others with an additional apparatus, such as a connecting member, brace or rod. A pedicle screw and rod system is one such example that is commonly used to secure adjacent vertebrae together in a desired relationship. 
     As an example, a patient may require that a number of vertebrae be secured so that fusion of the bones may take place. To accomplish fusion a number of bone anchors may be secured to a plurality of vertebrae via threaded engagement or by hooks that engage anatomy about the vertebrae. Each bone anchor or hook may be integrally attached to a coupling member which often include upstanding walls forming a u-shape resembling a yoke. The coupling members may be integral with the anchor member head or may be movably attached and articulate relative to the anchor members. Each coupling member in turn may be secured relative to the other coupling members by a connecting member or rod. A locking device or cap is driven into each of the coupling members ultimately locking the rod relative to each coupling member. 
     When positioning a bone anchor or hook, the orientation of the anatomical structures often results in a skewed relationship of the coupling members relative to each other. The connecting member, once placed in the coupling members, is utilized to reorient the vertebrae in a more desirable relationship. Undesirable relationships of vertebrae are often attributed to disc collapse, trauma, or disease such as scoliosis. In the case of collapse, distraction of the vertebrae may be desirable. If the anchor, coupling member and rod accompany an interbody device, contraction of the vertebrae to promote fusion may be desirable. However in the case of trauma or scoliosis, the connecting member may be pre-bent in a predetermined manner conforming to the ultimate desired position of the vertebrae. The deformation, or bend, of the spinal connecting member takes the shape of the desired spinal alignment and thus will likely not conform to the skewed relationship of the coupling members. The connecting member or rod may need to be reduced and or rotated to be captured in the coupling members. 
     The reduction and rotation of spinal rods is currently accomplished by devices relying on threaded mechanisms for linear advancement of the rods into the coupling members. While these devices may be effective, they are typically complicated, bulky, involve many revolutions to achieve reduction, offer little in the way of tactile feed back to the operator, require two hands for the reduction process, and are not easily adapted to minimally invasive surgery. 
     Minimally invasive surgeries require that only small incisions be made (typically ¾″) in the skin of the patient posterior to each vertebrae requiring a spinal implant assembly. Tissues that impede entry to the surgical site are then distracted, and a pedicle screw assembly, typically attached to an anchor extension or yoke manipulator, is introduced to the surgical site. All subsequent procedures take place in or adjacent to the yoke manipulator including, but not limited to, rod reduction, rod rotation, and deployment and securance of a locking device. Typical instruments that perform rod reduction are not adaptable from open surgery techniques to the limited area afforded in minimally invasive surgery. In addition the complexity of current instruments, their method of operation, and the need for additional tools to complete the surgery lead to lengthier surgical times. 
     SUMMARY OF THE INVENTION 
     For these reasons it is desirable to have an improved drive tool apparatus that can be utilized in both minimally invasive and open spinal surgery that provides ease of rod reduction and rotation while decreasing the time of surgery. In addition, the instrument should provide the operator a simple stationary grip to apply anti torque while other instruments within the tool are rotated. The instrument should allow for both the initial and final locking of a cap in a coupling member thus reducing the number of additional instruments necessary to successfully complete a spinal reduction surgery. 
     A drive tool apparatus is provided for securing a locking device and a connecting element within a coupling member anchored to a vertebral body. The apparatus has an attachment mechanism for quick engagement to an anchor extension and a single actuating lever that is operable to advance a drive rod, releasably attached to a locking device, linearly along the longitudinal axis of the drive tool. In addition the drive rod of the apparatus is rotatable to initially capture a locking device and connecting element in a coupling member and ultimately fully securing the locking device or cap within the coupling member thus fixing all elements relative to one another. The act of squeezing the lever and advancing the drive rod provides the operator with immediate and constant tactile feedback as to the forces the drive tool is encountering. The stop mechanism insures that the drive rod can only travel in a distal direction, thus the operator need not be concerned with sudden or rapid movement of the drive rod in a proximal direction when releasing the actuating lever. The mechanical guide on the drive tool provides the operator with visual feedback as to the orientation of the locking device and to the depth to which the drive tool has advanced. The mechanical guide thus eliminates the need for the surgeon to determine or guess when the drive rod is fully linearly advanced. The two walls on the mechanical guide give the operator a visual aid during rotation of the drive rod indicating the current status as to whether the locking device is temporarily locked or fully locked. In the fully locked position, the drive rod is no longer mechanically engaged with the drive tool and thus can be easily removed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exploded front view of a pedicle screw assembly; 
         FIG. 2  illustrates an exploded side view of the pedicle screw assembly; 
         FIG. 3   a  is a top view of a coupling member of the pedicle screw assembly; 
         FIG. 3   b  is a front view of the coupling member; 
         FIG. 4  is a perspective view of a locking device or cap of the pedicle screw assembly; 
         FIG. 5  is a front sectional view of the locking device or cap; 
         FIG. 6  is an exploded view of an alternative pedicle assembly (swage embodiment); 
         FIG. 7  is a front sectional view of the assembly of  FIG. 6 ; 
         FIG. 7   a  is a side sectional view of the assembly of  FIG. 6 ; 
         FIG. 8  is a perspective view of a drive tool with a drive rod, anchor extension and the pedicle screw assembly; 
         FIG. 9  is a perspective view of the anchor extension or yoke manipulator; 
         FIG. 10   a  is a front side sectional view of the drive tool, drive rod, anchor extension and pedicle screw assembly; 
         FIG. 10   b  is a right side view of an elongate body of the drive tool; 
         FIG. 11  is a perspective view of the drive tool elongate body with a stationary grip; 
         FIG. 12  is a left side view of the drive tool, drive rod, anchor extension and pedicle screw assembly; 
         FIG. 13  is a perspective view of the drive tool elongate body with attachment structures/portions and the stationary grip; 
         FIG. 14  is a front side sectional view of the drive tool attachment portion; 
         FIG. 15  is a front side sectional view of the drive tool attachment portion; 
         FIG. 16  is a perspective view of the drive rod; 
         FIG. 17  is a front view of the drive rod; 
         FIG. 18  is a perspective sectional view of the drive surface tip of the drive rod; 
         FIG. 19  is a perspective view of the nitinol pin embodiment of a drive rod; 
         FIG. 20  is a perspective view of the nitinol pin of the drive rod of  FIG. 19 ; 
         FIG. 21  is an exploded view of the sleeve capture drive rod embodiment; 
         FIG. 22   a  is a perspective view of the sleeve of the drive rod of  FIG. 21 . with a locking device or cap; 
         FIG. 22   b  is a left side sectional view of the sleeve of the drive rod of  FIG. 21 . with the locking device or cap; 
         FIG. 23  is a front side sectional view of the proximal end of the drive tool with the drive rod; 
         FIG. 24  is a front side sectional view of the mechanical engagement portion and the stop portion of the drive tool; 
         FIG. 25   a  is a perspective view of the actuating lever of the drive tool; 
         FIG. 25   b  is a top view of the actuating lever and pawl mechanism; 
         FIG. 25   c  is a front side view of the drive pawl mechanism; 
         FIG. 25   d  is a perspective view of the drive pawl mechanism; 
         FIG. 26  is a front side sectional view of drive pawl engaging the drive portion of the drive rod; 
         FIG. 27   a  is a perspective view of the stop pawl of the drive tool; 
         FIG. 27   b  is a left side view of the stationary grip of the drive tool; 
         FIG. 28   a  is a top view of the alignment pin of the drive rod abutting the zero degree wall of the mechanical guide on the drive tool; 
         FIG. 28   b  is a top view of the alignment pin of the drive rod in the 40-50 degree position on the mechanical guide on the drive tool indicating temporary lock; 
         FIG. 28   c  is a top view of the alignment pin of the drive rod abutting the hard stop wall of the mechanical guide on the drive tool indicating fully locked; 
         FIG. 29  is a front side view of the drive rod in the proper orientation to enter the drive tool so that drive surface engages both the drive pawl and the stop pawl, and the alignment pin abuts the zero degree wall; 
         FIG. 30  is a front side sectional view of the drive rod in the entry orientation with the drive portion engaging both the drive pawl and the stop pawl; 
         FIG. 31  is a front side sectional view of the drive rod fully deployed in the drive tool and the locking device and connoting member seated in the coupling member with the alignment pin abutting the zero degree wall (not seen); 
         FIG. 32  is a front side sectional view of the drive rod fully deployed in the drive tool and the locking device and connoting member seated in the coupling member with the alignment pin abutting in the 40-50 degree position with the drive portion still engaged to drive pawl and stop pawl; and 
         FIG. 33  is a front side sectional view of the drive rod fully deployed in the drive tool and the locking device and connecting member seated in the coupling member with alignment pin (now not seen) abutting the hard stop wall with the drive portion no longer engaged to drive pawl and stop pawl. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Prior rod persuader designs typically rely on threaded drive systems, such as in U.S. Pat. No. 7,278,995 to Nichols et al. that are cumbersome and slow because they require multiple rotations of a handle for linearly reducing a spinal rod. The &#39;995 patent requires the surgeon to manipulate two separate handles in order to linearly advance a drive rod and also rotate the drive rod to lock a cap in a coupling member. The use of two handles complicates the tool and the girth of the instrument typically requires the surgeon to occupy both hands in use. The advantage of the improved drive tool apparatus is actuation through a pawl on a unitary drive rod by a mechanical linkage allowing for rapid reduction. The reduction of the drive rod is further expedited in that it can be manually advanced distally through the drive tool while being mechanically restrained from moving in the proximal direction. Manual advancement is undertaken until it is determined that the mechanical advantage of the actuating mechanism is required. 
     Unlike the threaded drive and rongeur style persuaders, the improved drive tool apparatus uses a single unitary drive rod or shaft made from a single piece of metal that both drives the spinal rod linearly down and rotates the cap or locking device in place. The simplified unitary drive rod approach eliminates multiple parts, improves reliability, and simplifies operation of the tool. In addition, once the locking device is finally locked in place, the drive rod quickly and easily mechanically disengages from the drive tool due to the orientation of the drive surface relative to both the drive and stop pawls. 
     The improved drive tool apparatus has a unique actuating mechanism that utilizes an engagement of a pawl on a rack or drive portion of a drive rod. The drive pawl is freely rotatable allowing the pawl to engage the drive portion when necessary while allowing disengagement when the actuation lever is released. The lock or stop device prevents displacement of the drive rod in the proximal direction during the return stroke of the pawl on the rack of the unitary drive rod. The actuating mechanism is a hybrid mechanism utilizing both a mechanical leverage and a rotatable pawl linkage that provides dynamic rotary and linear mechanical engagement simultaneously during linear displacement in the distal direction. Finally, the improved drive tool apparatus features an attachment mechanism for quick connection and disconnection to screw extenders and spinal screw assemblies which is desirable in MISS surgeries. The attachment mechanism allows the drive tool to rapidly attach and detach from screw extenders or yoke manipulators by depression of a simple trigger. The quick connection feature allows one drive tool to easily be transferred to multiple different screw assemblies, present in most spinal rod stabilization procedures. The quick connect feature eliminates complicated attachment to greatly reduce time and simplify the surgery. 
     The following location and direction convention will be used through out the drawings and their descriptions. In describing the surgical instrument of the present invention, the term “proximal” P refers to a direction of the tool or instrument away from the patient and towards the user while the term “distal” D refers to a direction of the tool or instrument towards the patient and away from the user. 
     Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present application. 
       FIGS. 1 and 2  provide exploded views of a pedicle screw assembly  100 . The pedicle screw assembly is fully described in U.S. patent application Ser. No. 10/358,530 which is incorporated by reference as if reproduced in its entirety herein. 
     The pedicle screw assembly  100  includes a bone anchor  120 , a coupling member or yoke  140 , a connecting member or rod  160  and a locking device or cap  180 . Bone anchor  120  includes a head portion  121 , a shank portion  122  depending from the head portion, and a threaded portion  123  depending from the shank. Coupling member or yoke  140  includes a body portion  141 , two arms  142  and  143  connected to body  141  adjacent distal end D forming a u-shaped channel  144  for receiving rod  160 . The coupling member  140  of  FIG. 3  includes an anchor bore  145  for receiving bone anchor  120 . The coupling member  140  includes an instrument engagement portion in the form of slot  146  and a bore  147 . Connecting member or rod  160  is circular in cross section with a smooth exterior surface and may come in any number of lengths to satisfy surgeon requirements. In  FIGS. 4 ,  5  and  7   a  the locking device or cap  180  includes inner wall surface  181  for engaging a drive apparatus and an outer wall surface  182 . The cap has a saddle portion  183  with a rod engagement surface  184 . Adjacent the proximal end of the locking device are flanges  185 , 186  which engage interior grooves  148  in coupling member  140  and when rotated serve to lock the rod  160  between the rod engaging surface  184  and the u-shaped channel  144 . The proximal portion of the cap and the saddle portion are attached by a pin  187  with splaying arms  188  and  189 . 
     In addition it is contemplated that the bone anchor  120  may be cannulated  126  thus providing a pathway through the entire anchor member  120  should a guidewire attached to a specifically targeted surgical site wish to be employed. 
       FIGS. 6 and 7  provide another embodiment of a pedicle screw assembly  200 . The assembly  200  contains the exact same components of assembly  100  (coupling member  140 , rod  160 , and locking device  180 ) with the exception of the bone anchor. The bone anchor  220  of assembly  200  includes a threaded portion  223 , and a shaft portion  240 . Threaded portion includes external threads  224  for anchoring into bone, and a crimping or swaging lip  254  for attaching the threaded portion  223  to the shaft portion  240 . The interior of the threaded portion is cannulated  226  having an inside diameter that is constant from the distal end of threaded portion  223  to adjacent the proximal end. At the proximal end there is a hexagonal opening  227  to mate with the hexagonal section  250  of shaft portion  240 . The shaft portion  240  is monolithic but has several sections including head section  248 , neck section  249  depending from head section, hexagonal section  250  depending from neck section, and shaft  251  depending from hexagonal section  250 . The shaft has a taper  252  at distal end D with a swaging or crimping groove  253  proximal and adjacent the taper  252 . 
     After shaft portion  240  and threaded portion  220  are manufactured they are assembled and placed in sets of various external thread ( 224 ) diameters. The shaft portion  240  is fed through anchor bore  145  of coupling member  140 , the head section  248  of shaft portion  240  is larger than that of distal end D of anchor bore  145  of coupling member  140  and will come to rest in distal end of coupling member  140 . The shaft portion  240  is then fed through cannulated section  226  of bone anchor  220  until proximal end of threaded portion  220  abuts distal end of neck section  249  of shaft portion  240 . A common method of swaging or crimping is performed on the swaging or crimping lip  254  until all of the lip material fills the swaging or crimping groove  253  of shaft portion  240 . Shaft portion  240  can no longer advance proximally or distally due to the relationship of the neck section  249  and the proximal end of bone anchor  220  and the swaging or crimping of lip  254  into groove  253 . The ability to rotate both the shaft portion  240  and the threaded portion  220  simultaneously is possible due to the mating surfaces of the hexagonal section  250  of shaft portion  240  and hexagonal opening  227  of bone anchor  220 . 
     The advantage of pedicle screw assembly  200  lies in that virtually any diameter external thread  224  of threaded section  223  can be employed. Since the threaded section  223  of bone anchor assembly  200  is not initially integral with shaft section  240  it need not be passed through anchor bore  145  of coupling member or yoke  140 . The ability select from screws with larger diameters, makes the screw ideal for patients with large anatomies, revision surgeries requiring rescue screws of large diameter and anchoring of screws in the ilium of the patient. Screw assemblies  200  would be provided fully assembled to surgeons in sets with varying diameter external threads  224  thus allowing the surgeon to select the desired diameter best suited for the given operation. Screw assembly  200  after assembled is thereafter employed in the exact same manner as screw assembly  100 . The method of employing the drive tool apparatus  1200  and other instruments of the present invention will be hereafter described using the numeration of pedicle screw assembly  100 , but is not to be considered limiting. 
     Referring now to  FIG. 7   a , in use, bone anchor  120  is inserted through anchor bore  145  of coupling member  140 . The larger diameter of head portion  121  of bone anchor  120  is larger than bone anchor bore  145  of coupling member  140  and thus bone anchor  120  is unable pass through. Two or more bone anchors  120  are driven into the adjacent bones to be stabilized. A connecting member or rod  160  is then placed in the u-shaped channels  144  of respective coupling members  140 , a locking device or cap  180  is then inserted into one of the coupling members  140  and rotated clockwise 10-45 degrees to temporarily capture connecting member  160  in coupling member  140 . After manipulating the spinal rod  160  for the desired results, the temporary locking step is repeated with the second pedicle screw assembly  100 . 
     The difficulties that arise during these types of surgeries often occur during the stage of inserting and reducing the rod  160  into the connecting members  140 . This step is often complicated by the fact that the pedicle screw assembly is almost certain to be surrounded by the patient&#39;s tissues, making a path to the coupling member difficult to navigate. It is at this stage that surgeons often look for instruments to assist in efficiently urging or persuading the rod  160  into the yokes  140 . 
     The improved drive tool apparatus  1200  is provided for the purpose of directly addressing the surgical need for an efficient instrument to persuade a connecting element  160  in a minimally invasive spinal surgery (MISS). Drive tool apparatus  1200  includes yoke manipulator  1100  and drive rod  1300 , which are shown in  FIG. 8  &amp;  FIG. 29-33 . The improved drive tool apparatus  1200  allows rigid attachment to a screw extender  1100  and screw assembly  100  during rotation, distraction, contraction and reduction of a connecting element  160  common in MISS. Drive tool  1200  may also be employed in rotating the spine as is common practice when treating severe trauma or disease such as scoliosis. The improved drive tool apparatus  1200  is able to resist detachment from the screw assembly in a manner superior to other devices enabling the surgeon to both reduce and rotate the spinal connecting element  160 . 
     In minimally invasive spine surgery a guide wire often is inserted into a patient and maneuvered toward the vertebra while fluoroscopy is employed to pinpoint and verify an accurate surgical location. Surrounding tissue is then sequentially dilated. Once the tissue is dilated, cannulated tools may be utilized to prepare the pedicle for a screw assembly  100  (e.g. pedicle probes, awls, taps, etc.) A cannulated bone anchor  120 , moveably attached to coupling member  140  through anchor bore  145  is slid over the guide wire distally until it reaches the surgical site. The use of a guide wire ultimately reduces the amount of tissue affected thus reducing recovery time. Minimally Invasive Spine Surgery may also be conducted without a guidewire relying on just the use of fluoroscopy. In either case, coupling member or yoke  140  needs to be attached to a tool such that the coupling member or yoke  140  may be manipulated by the operator deep within the patient. 
     Screw extender or yoke manipulator  1100  shown in  FIG. 8  and  FIG. 9  has a proximal end P and a distal end D. Screw or shaft extender  1100  includes body portion  1101 , arms  1102  depending distally from body  1101  defining opposing u-shaped slots  1104 , and a shaft or bore  1103  extending from the proximal end to the distal end creating a cannula or working corridor. In addition, screw extender  1100  accommodates attachment to a wide variety instruments with three different instrument attachment structures; bayonet connection slot  1106 , threaded connection  1109  and drive tool connection hole  1107 . For the purpose of the present invention particular attention may be paid to the drive tool connection hole  1107 . The connection hole  1107  is a bore or hole through one side of the extender body  1101  of the screw extender  1100 . Alternatively, the hole  1107  could be in the form of depressions or indentations in the manipulator shaft  1101  in a variety of other varying closed geometries such as, but not limited to, squares, hexagons, etc. The drive tool connection hole allows for rapid connect and disconnect to a variety of instruments and in particular the preferred drive tool apparatus  1200  via the screw extender attachment portion  1201  on drive tool apparatus  1200 . The simple hole  1107  in connection with the attachment portion or releasable connector device  1201  performs the critical functions of simplifying and accelerating the pace of the surgery by allowing the operator to pull a trigger and immediately remove drive tool  1200  from extender  1100 . 
     Screw extender  1100  is attached to coupling member  140  by a coupling member retaining structure  1105  on the inner surface of arms  1102  at distal end D that releasably mates in snap-fit connection with bore  147  of coupling member  140  of pedicle screw assembly  100 . It is contemplated that coupling member retaining structure  1105  may include, but not limited to, a boss, recess, flange, or any other structure that is suitable to mate with a complimentary structure on coupling member  140 . 
     The screw extenders arms  1102  are resiliently splayed away from one another with an extender arm spreader instrument (not shown). The extender  1100  is then placed over the coupling member  140  so that the slots  1104  in the screw extender  1100  are radially aligned with the u-shaped channel  144  of coupling member  140  and coupling member retaining structure  1105  is positioned in radial and longitudinal adjacency to bore  147 . The arms  1102  of screw extender  1100  are then allowed to resiliently return to their original position by the removal of the spreader instrument leaving screw extender  1100  and coupling member  140  rigidly attached in snap-fit engagement. 
     The screw extender  1100  may be used to manipulate the coupling member  140 , previously assembled to anchor member  120 , during the insertion process. If cannulated, the anchor  120 , coupling member  140 , and extender  1100  are fed down the guide wire to the surgical site. An anchor insertion device may then be attached to the extender  1100  at any of the three instrument attachment structure locations  1106 ,  1107 , or  1109 . The engagement of the insertion device (not shown) to the anchor  120  and engagement of extender  1100  to coupling member  140  provides a rigid construct. 
     Referring to  FIGS. 8 ,  10   a ,  11 , and  12 , the long slot  1104  of the manipulator  1100  provides the surgeon with ample clearance and visualization of the surgical site which are beneficial during insertion of connecting member  160 . The insertion of the rod or connecting member  160  will be more fully described when describing the drive tool  1200  in more detail hereinafter. It is contemplated that the slots  1104  of the extenders  1100  may be of varying lengths. In fact, as long as one of the extenders  1100  provides enough clearance for the connecting member  160  to be initially inserted, the other extender(s)  1100  may be provided with shorter slots  1104  or perhaps may include a slot on only one side. In any event, whether the slots  1104  are short or long, they must allow for adequate access during the process of passing the connecting member  160  into the coupling members  140 . 
     The drive tool apparatus  1200  of the present invention has a distal direction D, proximal direction P, and consists principally of a screw extender attachment portion  1201 , elongate shaft assembly or body  1220 , the unitary drive rod  1300 , mechanical linkage portion  1260 , stationary grip  1221 , drive actuator lever  1261  and mechanical guide portion  1232  as shown in  FIGS. 10   a  and  12 . The drive tool apparatus  1200  is used in concert with screw extender  1100 . Screw extender  1100  is designed for minimally invasive spine surgery but may be utilized in open surgical situations which will be addressed later. Screw extender  1100  once rigidly attached to drive tool  1200  provide the operator a working corridor to the implantation site with the ability to manipulate the implant while allowing other instruments to be employed therethrough. 
     The elongate shaft assembly or body  1220  of the drive tool apparatus  1200  has distal end D and proximal end P and is provided for the purpose of providing a structural member intended to resist longitudinal compression forces created during the rod reduction process and to provide structure for accommodating components that can be attached to or rotated relative to body  1220 . The body or shaft assembly  1220  is a substantially hollow tube with varying diameters and wall thicknesses. The elongate body  1220  or elongate shaft assembly also provides rectangular through hole  1271  to accommodate mechanical linkage portion support  1270 , rectangular flat  1208  accommodating attachment portion structure  1225 , and a partial bore  1272  with slot  127  to accommodate stop portion  1274  located inside stationary grip  1221  mounted to body  1220  adjacent the proximal end. Finally, the shaft assembly  1220  provides a mechanical guide flat  1222  for unitary drive rod  1300 . Alternatively, the attachment support structure  1225  and mechanical linkage portion support  1270  could be machined as an integral part of elongate body  1220 . 
     The main tube body  1307  has significant wall thicknesses to support the high compressive loads created by drive actuator pawl  1229  on the unitary drive rod member  1300 , as shown in  FIG. 26 . High compressive loads are created because the main tube body  1220  provides a force to counter and balance the force exerted by the drive actuator pawl  1229  on the unitary drive rod member  1300  on the spinal rod  160 . 
     As shown in  FIG. 13 , elongate body  1220  has a tapered section  1223  which transitions to the distal tube body  1220   a . Distal tube body  1220   a  has a reduced wall diameter because distal portion of distal tube body  1220   a  will enter the furthest depth in the body of the patient. The smaller diameter reduces the footprint of elongate shaft assembly  1220  thus disrupting less tissue upon insertion of drive tool  1200  into the patient. The distal tube body  1220   a  can have a reduced wall thickness and smaller diameter because the screw extender  1100  provides additional significant structural support against longitudinal compression. 
     Referring now to  FIGS. 10   a - 13 . Elongate shaft assembly or body  1220  also provides a mechanical guide portion  1232  for rotational engagement of the unitary drive rod member  1300  as shown in  FIG. 12 . Elongate shaft assembly or body&#39;s  1220  mechanical guide portion  1232  cooperates with an alignment pin  1304  of drive rod  1300  facilitating alignment and providing both a visual means for indicating mechanical engagement and disengagement of the unitary drive rod member  1300  drive portion  1302  with a drive actuator pawl  1229  of the mechanical linkage portion  1260  and lock, portion  1240 , as well as the orientation of locking device  180  relative to coupling member  140 . After the reduction of the rod  160  on to the coupling member  140  and during the locking of the locking device or cap  180 , flat  1222  on body  1220  provides a zero degree wall  1231  that gives the operator a visual (and starting point) reference with respect to the position of cap  180 . Mechanical guide portion  1232  has hard stop  1224  representing 100 degrees of revolution letting the operator know that cap  180  is fully locked in coupling member  140  and rod is captured when alignment pin  1304  abuts hard stop  1224 . Accordingly, the wall  1231  and hard stop  1224  are preferably circumferentially spaced around the top of the elongate body  1220 , as seen best in  FIGS. 12 and 28   a - 28   c.    
     The screw extender attachment portion  1201  as shown in  FIGS. 14 and 15 , and discussed in detail below, provides for the quick capture and release of the pedicle screw extender  1100  to the drive tool  1200 . The attachment portion  1201 , externally visible as a trigger, is attached to the elongate shaft assembly or body  1220  at attachment support structure  1225  as seen in  FIG. 15 . 
     Referring now to  FIGS. 10   b - 13 , attachment support structure  1225  is rectangular in shape and is welded onto assembly body  1220  in rectangular flat  1208 . Rectangular flat  1208  has a throughbore  1209  to receive the catch  1206  of attachment portion  1201 . Attachment support structure  1225  has a keyhole shaped opening  1210  therethrough that houses the screw extender attachment portion  1201 . Distal end of keyhole shaped opening  1210  includes a threaded bore  1211  which receives threaded sleeve  1212 . 
     Referring now to  FIGS. 14 and 15 , the attachment portion  1201  includes trigger  1202 , attachment pin  1203 , attachment collar  1204 , threaded sleeve  1212 , adjustment screw  1205 , catch  1206 , and spring  1207 . The movement of catch  1206  in and out of drive tool connection hole  1107  of screw extender  1100 , when positioned adjacent to the through bore  1209 , allows the drive tool  1200  to be easily attached and detached to screw extender  1100 . The spring  1207  urges the catch  1206  into the drive tool connection hole when the trigger  1202  is released. 
     The surgeon operates attachment mechanism portion  1201  by applying a force in proximal direction to trigger  1202 . Trigger  1202  pivots about attachment pin  1203  moving the distal end of trigger  1202  away from the body  1220  of drive tool  1200  which in turn engages attachment collar  1204 , as illustrated in  FIG. 8 , urging the attachment collar  1204  away from drive tool  1200 . The threaded engagement  1215  of attachment collar  1204  and catch  1206  forces the entire sub assembly to move in the direction away from the screw extender thus catch  1206  mechanically disengages from drive tool connection hole  1107  in screw extender  1100 . The drive tool apparatus  1200  can then be pulled in a proximal direction easily disengaging from screw extender  1100 . Once the operator releases the trigger  1202 , with the drive tool connection hole  1107  adjacent to the through bore  1209 , the spring  1207  urges collar  1204 , screw  1209  and catch  1206  back toward the inner shaft of drive tool  1200 . The attachment mechanism  1201  can then mechanically reconnect the screw extender  1100  to drive tool  1200  once the screw extender  1100  is shifted into position. 
     As shown in  FIG. 14  and  FIG. 15 , the threaded sleeve  1212  prevents the entire attachment mechanism  1201  from detaching from attachment support structure  1225 . Threaded sleeve  1212  is fixed to the attachment support structure  1225  of elongate shaft assembly or body  1220  because threaded sleeve  1212  is threaded into the attachment support structure  1225  at threaded bore  1211 . The sub-assembly cannot escape because inner diameter of the threaded sleeve  1212  is smaller than the outer diameter of spring  1207  and catch  1206 . 
     The attachment collar  1204 , adjustment screw  1205 , and catch  1206  are preferably threadably connected together thus allowing the entire sub-assembly to move in a direction transverse to the longitudinal axis of drive tool  1200 . Alternatively, the sub-assembly could be one single machined part or a combination thereof. 
     Turning now to the unitary drive rod of  FIGS. 16 and 17 , unitary drive rod  1300  has a distal end D and proximal end P and is provided for the purpose of creating a compressive force used to drive locking device  180  on spinal rod  160  within coupling member or yoke  140  while in concert with drive tool  1200  and anchor extension  1100 . The drive rod  1300  in its preferred embodiment is a single solid shaft  1301  with portions that do not move relative to one another including a drive portion  1302  mounted along a length of unitary drive rod, drive surface  1303  for engaging the cap or locking device  180 , tool engagement end  1305  with groove  1306  for mating with an instrument, and alignment structure  1304  for engaging mechanical guide flat  1222  of drive tool  1200 . The unitary drive rod  1300  is preferably formed from a single piece of homogenous metal to improve strength. Because multiple structural elements and linkages tend to increase the diameter of instruments used to apply force, the unitary drive rod  1300  requires minimal material while still providing the structural strength to resist torsion experienced during locking of cap  180 . 
     In use unitary drive rod  1300  applies a compressive force through a locking device or cap  180  that mechanically engages the spinal rod  160 . The application of compressive force through the locking device  180  or cap drives or persuades the rod  160  into yoke or coupling member  140 . Once the rod  160  rests on bottom of u-shaped channel  144  of coupling member  140 , drive rod  1300  is turned forcing the locking device  180  to turn simultaneously, with minimal relative motion between the drive rod  1300  and locking device  180 , to either temporarily or permanently lock the locking device  180  or cap into the yoke or coupling member  140 . The application of linear and rotary force by unitary drive rod  1300  through locking device or cap  180  to the spinal rod  160  provides several beneficial results. Not applying force directly to the spinal rod  160  but though the locking device or cap  180  more evenly distributes the compressive force or pressure over a larger area of rod  160 . The compressive force required to drive the spinal rod  160  typically requires approximately a hundred pounds of force but in the sacral region may require hundreds of pounds of force. The distribution of pressure over rod  160  by cap or locking device  180  avoids large localized pressures being applied to rod  160  during the locking of rod  160  into coupling member or yoke  140 . 
     The drive rod  1300  is sized to fit within screw extender  1100  and drive tool  1200 . As shown in  FIG. 16 , drive rod  1300  includes a shaft  1301  and an alignment pin  1304 . Alignment pin extends from drive rod  1300  transverse and preferably substantially orthogonal to the longitudinal axis  1300   a  of drive rod  1300 . Alignment pin  1304  preferably takes the form of a pin, but other structures are contemplated such as a boss, flange, or any other structure complementary to the mechanical guide flat  1222  of drive rod tool  1200  for orienting the drive rod  1300 . 
     Drive rod  1300  has drive portion  1302  which engages drive actuator pawl  1229  and stop pawl  1246 . Drive portion  1302  has teeth with flat portion  1310  extending orthogonal to the drive rod axis  1300   a  and angled portion  1311  extending at an incline to the axis  1300   a  for forming a triangle in profile that mates with triangular portion  1284  of drive pawl  1229  and surface engagement end  1250  of stop pawl  1246 . Drive rod  1300  may include a proximal engagement end  1305  for non-rotatable engagement with a removable grip, ratchet, or fixed grip instrument (not shown). The rectangular engagement end  1305  allows for the attachment of an “off-the-shelf” T-handle (not shown). Engagement end  1305  preferably allows for the attachment of a quarter inch drive T-handle with a quick disconnect. The quick disconnect utilizes groove  1306  distal and adjacent to engagement end  1305  to quickly connect and disconnect from a handle. The T-handle, once releasably attached to drive rod  1300 , is used to apply torque to unitary drive rod  1300  for rotating locking devices such as cap  180 . In alternate embodiments, the engagement end  1305  could take on numerous other geometric shapes, so long as it mates with an equivalent engagement surface of a handle, such as a hexagonal prism, or a triangular prism. 
     The drive rod  1300  is employed after being mated to the cap or locking device  180  at drive surface  1303 . In the preferred embodiment a “stab and grab” technique or method is used to secure the locking device  180  to drive surface  1303 . The preferred embodiment of drive surface  1303  located at distal end of drive rod  1300  is shown in  FIGS. 17 &amp; 18 . The drive surface  1303  is tapered  1307  in profile and contains a bore  1308  providing clearance for pin  187  in coupling member  140 . The drive rod  1300  is literally stabbed or forcefully friction fit within locking device  180  so that a line contact is formed between the drive surface  1303  and the inner wall  181  of locking device  180 . The locking device  180  is temporarily fastened to the drive surface  1303  by slight deformation of the softer material (preferably titanium alloy) of the inner wall  181  of locking device  180  by the harder material (preferably stainless steel) of drive surface  1303  of unitary drive rod  1300 . 
     An alternative “stab and grab” method is used for the pin cap capture drive rod retention embodiment  1400  shown in  FIGS. 19 and 20 . The pin capture unitary drive rod  1400  has all the same elements of drive rod  1200  except with a differing drive surface and the manner in which pin capture drive rod  1400  mates with locking device  180 . In this alternative embodiment the retention mechanism consists of the drive surface  1403  and a Nitinol pin  1430 . Unlike drive rod  1200  the drive surface  1403  of pin capture drive  1400  is not tapered. In use, distal end D of pin cap capture drive rod  1400 , is stabbed or moved in the distal direction toward the inner wall  181  of locking device  180 . As the pin capture rod  1400  is advanced, the Nitinol pin  1430  resiliently deflects inward. This inward deflection creates a cantilever spring. The Nitinol pin  1430  resists inward deflection and thus makes a press fit on inner wall  181  of locking device  180  as the pin  1430  seeks its original position. The force of the Nitinol pin  1430  against inner wall  181  creates sufficient friction to hold the locking device  180  temporarily in place. 
     In the manufacture of pin capture drive rod  1400  one of the lobes  1420  of drive surface  1403  is omitted and a hole (not shown), slightly smaller than the outside diameter of pin  1430 , is drilled in the open space where missing lobe  1420  would have been. The hole is drilled in the distal to proximal direction to equal length B of pin  1430 . The pin  1430  is then press fit into the hole. The location of the pin  1430  in relationship to the adjacent lobes  1420  is critical in that should the drive rod  1400  be dropped or banged into something, pin  1430  will not be able to bend enough to plastically deform. 
     Materials other than Nitinol may be considered to make pin  1430  so long as those materials are bio-compatible, remain elastically deformable and do not yield under a radial bending force. 
     In yet another embodiment, the same “stab and grab” method is employed using the sleeve cap capture drive rod  1500  shown in  FIGS. 21-22   b . Like drive rods  1300  and  1400 , drive rod  1500  performs the same function of reducing and locking a cap  180  in a coupling member. Sleeve capture drive rod  1500  has a distal end D and a proximal end P. Sleeve capture drive rod  1500  has a body  1501  with a diameter, depending distally from body  1501  is a smaller diameter portion  1545  creating sleeve abutment ledge  1549 . Depending distally from smaller diameter portion  1545  is smallest diameter portion  1547  creating spring abutment ledge  1550 . Drive surface  1503  depends distally from smallest diameter portion  1545 . 
     Drive rod  1500  has a sleeve  1541  with a groove  1551  adjacent distal end D housing o-ring  1543  for the purpose of frictionally engaging the external wall  182  of a locking device  180 . Sleeve  1541  has an outer diameter that matches that of body  1501  and an inner diameter that is slightly larger than smaller diameter portion  1545 . Distal end D of sleeve  1541  has diametrically opposed slots  1552  that defines arms  1553 ,  1554 . In use inside of arms  1553 ,  1554  contact outer wall  182  between flanges  185 ,  186  of locking device  180 . Sleeve  1541  houses spring  1540  which surrounds smallest diameter portion  1547  with proximal end of spring  1540  abutting spring abutment ledge  1550 . Spring  1540  is held within sleeve  1541  by the presence of alignment pin  1546  press fit in hole  1542  of sleeve  1541 . Alignment pin  1546  performs two functions. Pin  1546  prevents the spring  1550  from advancing distally and also aligns the sleeve  1541  so that arms  1553 ,  1554  fit between flanges  185 ,  186  of locking device  180  and inner portion of arms  1553 ,  1554  contact outer wall  182 . The pin  1546  press fit to sleeve  1541  rides on flat  1544  thus preventing sleeve  1541  from rotating about smallest diameter portion  1547 . 
     Drive rod  1500  captures the locking device  180  in two ways. Contact of o-ring  1543  friction fitting with outer wall  182  of locking device previously described, and a pin  187  capturing groove  1548  inside a bore at distal end of drive surface  1503 . As the cap  180  is pressed onto the drive surface splaying arms  188 ,  189  of pin  187  are urged toward one another until proximal portion of arms  188 ,  189  come to rest in groove  1548  thus releasably mating the drive rod  1500  to cap  180 . 
     In use, the locking device or cap  180  is mated to the drive surface  1503  of drive rod  1500  in the orientation allowed by relationship of flanges  188 ,  189  and arms  1553 ,  1554 . The cap  180  is temporarily held in place on drive rod  1500  by o-ring  1543  contacting outer wall  182 , and proximal end of arms  188 ,  189  residing in groove  1548 . During the procedure of locking the cap  180  to the coupling member  140  the distal ends of arms  1553 ,  1554  engage the proximal end of coupling member  140 . The outer diameter of the sleeve  1541  is greater than the inside diameter of coupling member  140 . As the drive rod  1500  is advanced distally the distal outside diameter portion of sleeve  1541  contacts the proximal end of the coupling member. As drive rod  1500  continues to be advanced distally, the pin  1546  in sleeve  1541  acts against spring  1540  thus keeping the sleeve  1541  stationary abutting proximal end of coupling member  140 . As drive rod  1500  is advanced with cap  180 , sleeve  1541  remains stationary, the cap  180  is driven past the friction fit of o-ring  1543 , but remains attached at pin  187 . Drive rod  1500  continues to be advanced until the connecting member or rod  160  is fully seated in u-shaped channel  144  of coupling member  140 . The drive rod  1500  is initially rotated fifty degrees to partially lock the cap  180  in coupling member  160  and eventually to one hundred degrees to final lock the screw assembly  100 . As the cap  180  is rotated the saddle portion  183  is advanced distally taking with it pin  187  thus pulling pin arms  188 ,  189  out of groove  1548  freeing drive rod  1500  from cap  180 . 
     Turning now to  FIGS. 23 and 24  and the interaction between the preferred drive tool  1200  and the unitary drive rod  1300 . There are two elements that give the drive tool  1200  the ability to safely impart mechanical force and receive continuous tactile feedback on the drive rod  1300 , mechanical linkage portion  1260  housed in mechanical linkage support portion  1226  and stop portion  1240  housed in stationary grip  1221 . Drive tool  1200  has a distal end D and proximal end P and a longitudinal axis L as well as two transverse directions E and W. Both the mechanical linkage portion  1260  and stop portion  1240  function by pawls contacting drive portion  1302  of unitary drive rod member  1300 . 
     The mechanical linkage portion  1260  includes drive actuator pawl  1229 , torsion spring  1269 , pawl pin  1268 , stop pin  1274  and a fulcrum pin  1262  all captured in lever  1261 . Lever  1261  is substantially rectangular in cross section, and is substantially straight with a slight bend adjacent proximal end as seen in  FIG. 25 . Lever  1261  has a semicircular distal end  1275  that prevents lever from traveling far enough to do damage to lever leaf spring  1266  and reduces possible pinch points. Depending from distal end  1275 , lever has a bore  1276  partially through lever  1261  to receive end of leaf spring  1266  preventing the spring  1266  from moving in a lateral direction. Adjacent and proximal bore  1276  is a threaded bore  1277  for receiving lever leaf spring attachment screw  1278 . Proximal the slight bend in the lever  1261  is fulcrum pin  1262 . Adjacent and proximal to fulcrum pin  1262  is u-shaped slot  1280  defining arms  1281  and  1282  which house pawl  1229 , pawl pin  1268 , torsion spring  1269  and stop pin  1274 . 
     Drive actuator pawl  1229 , in the working position, has a flat  1283  on the distal end, a triangular portion  1284  in direction W, a substantially circular portion  1285  and a slight recessed portion  1286  forming a catch. Drive pawl  1229  has a bore  1287  in the center of the substantially circular portion  1285  to receive pawl pin  1268 . Pawl also has a slot  1288  to accommodate spring  1269 . In assembly, spring  1269  is placed in slot  1288  of pawl  1229  and both are placed in u-shaped slot  1280  in lever  1261 . Pawl pin is then inserted through bore  1290  in lever  1261 , into bore  1287  of pawl, through spring  1269  and out of the pawl hole  1287  and lever fulcrum pin hole  1290 . Stop pin  1274  is then placed in the stop pin bore  1291 , both ends being flush with the side of lever  1261 . The bores of pawl  1229 , spring  1269  (with stop pin  1274  in place) are lined up with fulcrum pin hole  1279  and fulcrum pin  1262  is inserted. Fulcrum pin  1262  is inserted through lever fulcrum pin hole  1279  capturing the pawl  1229  assembly and pin hole in mechanical linkage support structure  1225 . Fulcrum pin  1262  is then secured to mechanical linkage portion support  1226  by laser welding or by any other means known in the art. 
     Referring now to  FIGS. 24-27 , the stationary grip  1221  performs two functions, it serves as a stationary handle for the operator to hold while squeezing lever  1261 , and it houses stop portion  1240  which in operation prevents drive rod  1300  from releasing or otherwise receding proximally while drive rod  1300  is reducing connecting member  160 . The stationary grip  1221  is located adjacent proximal end of drive tool  1200  and extends transverse and preferably substantially orthogonal to the longitudinal axis of drive tool  1200 . Stationary grip  1221  is attached to drive tool  1200  at bore  1272  abutting slot  1273  as seen in  FIGS. 10   b  and  13 . Stationary grip in cross section is semicircular with a flat  1230  in the distal direction and is tapered with a wider end in direction E leading to a narrower end in direction W. Flat  1230  ends adjacent drive tool  1200  leaving stationary grip fully circular in cross section  1255  at the end to be inserted in bore  1272 . Stationary grip flat  1230  has a threaded bore hole  1251  to receive screw  1252  to secure stationary grip leaf spring  1267 . Stationary grip  1221  is solid except at end  1242  disposed in drive tool  1200 . End  1242  consists of a hexagonal bore  1243 , large circular bore  1244  which houses stop pawl  1246 , and smaller circular bore  1245  which houses stop pawl spring  1247 . Stop pawl  1246  has circular end  1248  which engages spring  1247 , hexagonal portion  1249  which mates with hexagonal bore  1243 , and substantially triangular shape drive surface engagement end  1250  which resides in slot  1273  of elongate body  1220  of drive tool  1200 . 
     In assembly, spring  1247  is placed in small circular bore  1245 , stop pawl  1246  is placed in hexagonal bore  1243  of grip  1221  which in turn is then placed in bore  1272  of drive tool  1200  such that stationary grip flat  1230  is facing distal direction D on drive tool  1200 . The grip  1221  is then press fit, welded or otherwise attached to body  1220 . Hexagonal bore  1243  is slightly larger than hexagonal portion  1249  on stop pawl  1246  allowing stop pawl  1246  to slide back and forth in hexagonal bore  1243  while not allowing stop pawl  1246  to rotate. Slot  1273  is slightly wider than drive surface engagement end  1250  but not wider than hexagonal portion  1249  thus allowing surface engagement end  1250  to enter the shaft of elongate body  1220  while restraining the entire stop pawl  1246  from doing so. Stop pawl spring  1247  urges stop pawl  1246  toward the shaft of drive rod elongate body  1220  while allowing it to completely recede in hexagonal and circular bores  1243 , 1244  should there be enough force against pawl  1246  to collapse spring  1247 . 
     Once the pedicle screw assemblies  100  attached to yoke manipulators  1100  are deposited in the vertebral bodies and rest on the pedicles, the connecting member  160  is introduced and delivered so that it rests just above and spans both of the coupling members  140 . It is at this point that rod  160  needs to be reduced into the coupling members  140  and locked in place with locking device or cap  180 . 
     Drive tool  1200  is attached to yoke manipulator  1100  with attachment mechanism  1201  as previously described. Cap  180  is placed on drive rod  1300  with the “stab and grab” technique. The operator grasps the tool holding stationary grip  1221  and actuating lever  1261 . Drive rod  1300  with cap  180  attached to distal end are introduced into shaft of drive tool  1200  from the proximal end thereof and eventually into yoke manipulator  1100  disposed in drive tool  1200 , in an orientation such that drive portion  1302  will contact both stop pawl  1246  and drive pawl  1229  as seen in  FIG. 29 . This orientation will be visual with alignment pin  1304  which will ultimately reside against zero degree wall  1231  of mechanical guide portion  1223  once rod  160  and locking device  180  are fully reduced in coupling member  140  as seen in  FIG. 28   a . The drive rod  1300  and cap  180  can be advanced manually proximally down the shaft toward the surgical site. Once drive portion  1302  of drive rod  1300  comes in contact with stop pawl  1246  an audible clicking noise will be heard letting the operator of drive tool  1200  hear and feel that the drive rod  1300  is in engagement with the stop pawl  1246 . With drive portion  1302  of drive rod  1300  in engagement with stop pawl  1246 , the operator can continue with manual advancement or take advantage of the mechanical advancement provided by squeezing lever  1261  proximally toward stationary grip  1221 . 
     When the operator of the drive tool  1200  decides to employ mechanical advancement of drive rod  1300 , the operator uses the tool&#39;s handle assembly. In the illustrated and preferred form, the handle assembly includes stationary grip  1221  and actuating lever  1261  with the operator grasping stationary grip  1221  and the activating lever  1261  in one hand and pulling activating lever  1261  proximally toward the grip  1221 . As the activating lever  1261  is pulled toward the grip  1221  it pivots about fulcrum pin  1262 , thereby moving the drive pawl  1284  distally. Since the drive pawl  1284  is engaged against flat  1310  and angle portion  1311  of the ratchet teeth of drive portion  1302  of drive rod  1300 , the distal motion of the drive pawl  1284  drives the drive rod  1300  distally. Also depicted in these views is stop pawl  1246  and a stop pawl spring  1247 . Stop pawl  1246  cannot move distally or proximally, but the stop pawl spring  1247  allows stop pawl to move away from the drive rod  1300  as each angled ratchet tooth advances distally. Once each tooth passes stop pawl  1246 , pawl spring  1247  pushes stop pawl  1246  back toward driving rod  1300 , to engage the next ratchet tooth along drive portion  1302  of drive rod  1300 . Thus the stop pawl  1246  allows distal motion of drive rod  1300  but prohibits proximal motion of drive rod  1300 . In this regard, the tool  120  has a one-way locking mechanism by allowing the drive rod  1300  to be advanced and blocking the drive rod  1300  against being forced back upward in the shaft assembly  1220 . As activating lever  1261  is pulled again or nearer toward the stationary grip  1221 , further distal motion is imparted to drive rod  1300 . 
     Thus, stop pawl  1246  and stop pawl spring  1247  cooperate to restrict or oppose proximal motion of drive rod  1300  as the activating lever  1261  is released by the operator. In the depicted embodiment, actuating lever  1261  is biased away from stationary grip  1221  by leaf springs  1266 ,  1267  toward its initial position. As this occurs, torsion spring  1269  allows drive pawl  1284  to move proximally along drive portion  1302  of drive rod  1300 . This occurs with no distal or proximal motion of drive rod  1300  since torsion spring  1269  allows drive pawl  1284  to move away and toward drive rod  1300  along the ratchet teeth of drive rod  1300  as drive pawl  1284  ramps along drive portion  1302  proximally. The stop pawl  1246 , engaged against the ratchet teeth of drive portion  1302 , opposes proximal motion of drive rod  1300  during this action. It should be noted, that the actuating lever  1261  need not be abutting stationary grip  1221  to be released, but that actuating lever  1261  may be released at any time the operator sees fit. It is during the course of squeezing the lever that the operator of drive tool  1200  gets immediate tactile feedback of the resistance that rod  160  is encountering with tissue surrounding pedicle screw assembly  100 . It is contemplated that alternative types of driving mechanisms could be employed with stop pawl  1246  and stop pawl spring  1247 . Pawl  1246  and spring  1247  could be used to provide similar restricted proximal motion of a drive rod where the drive rod  1300  comprises some ratchet teeth on at least a portion of the drive rod  1300  which can cooperate with stop pawl  1246  and stop pawl spring  1247 . An example would be a toothless ratchet relying on friction. 
     The present invention provides a method for reducing, and rotating a spinal rod  160  as well as the compression or distraction of vertebrae. For the sake of simplicity, a one level surgery is considered with two pedicle screw assemblies  100  and a single connecting member or rod  160 . Once the connecting member  160  and cap  180  have been successfully reduced and seated in the coupling member  140  alignment pin  1304  of drive rod  1300  should be abutting zero degree wall  1231  as seen in and flat  1222  of mechanical guide portion  1223  on body  1220  of guide tool  1200  as shown in  FIGS. 28   a  and  31 . By turning drive rod  1300  in a clockwise direction so that alignment pin  1304  lies roughly half way between zero degree wall  1231  and hard stop  1224  of mechanical guide portion  1223  the rod  160  is captured in the coupling member  140  by locking device  180  as shown in  FIGS. 28   b  and  32 . The resulting temporary lock relieves all the pressure once on drive rod  1300  transferring it to cap  180 . At this point rod  160  and coupling members may still be manipulated. This rotation also causes the pawls  1246  and  1284  to disengage from the drive teeth of the drive rod  1300 . 
     In the case of the need for spinal compression or distraction, the physician temporarily locks both of the caps  180  in coupling members  140  thereby capturing the rod  160 . The physician then elects one of the assemblies  100  to put in a final lock position. The temporary lock on the one assembly  100  will still allow for movement relative to the rod  160 . The physician then can either distract or compress the vertebrae depending on the type of surgery that is being performed. Once the vertebrae are a desired distance from one another, the surgeon then puts the last assembly  100  in a final lock. Final lock is achieved by rotating drive rod  1300  until alignment pin  1304  abuts hard stop wall  1224  on drive tool  1200  as seen in  FIGS. 28   c  and  33 . 
     In the case of spinal deformity rod rotation is often necessary. In a typical surgery where rod rotation is not necessary, the drive tools  1200  when inserted will extend from the patients body substantially perpendicular to the longitudinal axis of the spine. In surgeries that require rod rotation the drive tools often will come reside at a variety of angles off the spine. With the locking devices  180  in both coupling members  140  temporarily locked, the surgeon, manipulates the first drive tool  1200  so that is in the physician desired position roughly perpendicular to the longitudinal axis of the spine. Once the drive tool is in position the surgeon rotates the drive rod  1300  to the final lock position where alignment pin  1304  abuts hard stop  1224 . In the final lock position the drive rod  1300  has been rotated approximately one hundred degrees which is enough to free drive portion  1302  from contact with both drive pawl  1229  and stop pawl  1246 . The drive rod  1300  can then be manually removed from shaft of drive tool  1200 . The second drive tool  1200 , if necessary, is moved into physician desired position and final locked. In cases of severe scoliosis and open surgery may be necessary, despite the fact that the drive tool  1200  and manipulator  1100  were designed for MIS surgeries it is contemplated that both could be used in an open technique without modification. 
     The tools  1200 ,  1100  and  1300  as well as implant devices  100 ,  140 ,  160  and  180  can be made from any suitable, structurally strong material. The structural portions and other components are constructed of suitable materials which are compatible with the uses and environments into which the apparatus will be utilized. Preferably, the tools and implants principally are constructed of metallic materials such as 17-4 stainless steel, or titanium, but not limited to those materials. The tools as well as implant devices are made using standard lathes, milling machines, electro discharge machining as well as T-IG and laser welding. Alternatively, other standard manufacturing processes such as casting could be used. 
     While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.