Abstract:
Minimal Invasive Spine Surgery (MISS) as a surgical approach is increasingly utilized because of the advantages it offers over conventional spine surgery. The smaller incision results in decreased tissue damage, less blood loss, decreased hospital stay &amp; faster postoperative recovery. The drawbacks of MISS are the long learning curve of working through a smaller incision, longer length of surgery, &amp; potential higher complication rate due to compromised visual field. These limitations can be overcome by more effectively using imaging and navigational devices. The pedicle device simplifies the hardest part of MISS instrumented fusion of conventional pedicle screw insertion by introducing a percutaneous temporary device to locate and create the channel for later conventional pedicle screw implantation using available imaging techniques. This results in faster conventional pedicle screw insertion with precision, thereby decreasing implantation error and minimizing soft tissue injury and blood loss, as well as neurological, vascular, and dural injuries and complications.

Description:
FIELD OF THE INVENTION 
     The present invention relates to improvements in the field of spine and more particularly to a system for location, placement, and insertion of pedicle darts which is applicable to both MIS and open surgical technique which allows for more exacting and rapid placement and angular insertion of fixation members into the spinal pedicle, to facilitate one of the most difficult phases of spine surgery. Greater access, angularity and location is allowed independent of manipulation of the pedicle darts into bony tissue, resulting in a reduced time necessary to complete one of the more difficult phases of the operative procedure. The result is increased safety of placement and insertion, as well as less time spent on the operating table. 
     BACKGROUND OF THE INVENTION 
     Lumbar Diskectomy and other spinal techniques require external stabilization of lumbar vertebrae to either side of the vertebra being treated. Traditional pedicle screw insertion has required the identification of the correct insertion point for pedicle screw placement. This process is difficult, even where there is direction visualization of the area of the pedicle where insertion will occur. Because placement, angularity, and turning insertion is a complex process, the insertion process often leads to inaccurate placement of the screw. Such inaccurate placement can have serious neurological, vascular, and dural leak complications. 
     Further, inaccurate placement of the pedicle screw may result in damage such that screw insertion either cannot be achieved, or if it can be achieved it may require additional surgical procedures for correction and may not enable the holding strength necessary. 
     Conventional techniques for insertion of the pedicle screw may involve extensive paraspinous muscle dissection, impairment of surrounding tissue and other compromising tissue removal is commonly necessary to properly insert a pedicle screw. This most often results in significant blood loss during this exposure phase of the operation, which is only one part of a multiple step operative procedure. Any problems at any stage of an operation can risk the patient&#39;s health and compound any unexpected routine problems which occur. 
     The surgical practitioner is faced with the choice between high exposure and a good view, versus a more limited exposure with a much poorer view and a heightened risk of a wrong insertion of the pedicle screw. Further, when a high exposure is attempted, excess bleeding is often encountered directly due to the higher exposure which can even further obscure visualization and may require blood transfusion with its associated complications. 
     Any extra time on the operating table, whether caused by excess bleeding or not places the patient in greater danger. But excess bleeding combined with longer operating time due to poor visibility, and corrective measures required to find the appropriate placement of the pedicle screw can be disastrous. All of the above effects contribute to surgeon fatigue, which can result in increased operative complications. 
     What is needed is a system which will enable correct placement of a pedicle device, accurately and consistently and which will not require extensive paraspinous muscle dissection in order to obtain the required visual area for proper placement. The needed device will ideally enable a gradual graded introduction into the pedicle and give an earlier indication of problems so that any error can be quickly corrected at a time before the introduction goes any further. 
     Currently available surgical retractor systems fail to fulfill all of the above requirements. Consequently there is a severe need for structures and procedures to meet such requirement. 
     SUMMARY OF THE INVENTION 
     The system and method of the invention, enables a staged location and entry into the pedicle for providing insertive, progressively larger threaded fixation and superior surgical control a distance from the spine. The pedicle dart system can be used in conjunction with or without a Jamshedi trocar and sleeve, in order to give additional advantage for early focussing of the early guided location and initial placement of the pedicle dart system. 
     The pedicle dart system is simple and has a small number of components. These components include a guide pin, a pedicle dart fastener (preferably having some control structure for easy manual rotation) having a central opening to accommodate the guide pin, an indexed sleeve (preferably with handle) having a central opening to accommodate the threaded pedicle dart fastener to hold the dart to the sleeve. The threaded pedicle dart fastener should have a manual control surface which facilitates it axial rotation with respect to the indexed sleeve. The indexed sleeve preferably has a handle to enable rotational turning of the pedicle dart into the pedicle for ease and control. 
     The pedicle dart system enables use of the threaded pedicle dart fastener to both engage and disengage from an implaced pedicle dart. The indexed sleeve can impart rotational force of the sleeve directly into the pedicle dart due to the indexed connection between the pedicle dart and indexed sleeve. The threaded pedicle dart fastener is used to engaged and pull the pedicle dart to an indexed position with respect to the indexed sleeve. 
     The preferred method of indexing involves a pair of oppositely located fingers at the end of the indexed sleeve which are narrower than indexed slots located rearward of each of the pedicle darts. By making the fingers of the indexed sleeve narrower than the indexed slots rearward of each of the pedicle darts, the registry of the fingers of the indexed sleeve into the pedicle dart slots will occur much more rapidly. This enables easy location and re-attachment of the pedicle screw no matter whether the pedicle dart is attached away from the patient by hand or whether an implaced pedicle dart is re-attached for engagement with the pedicle dart system to remove it. 
     Further, the pedicle dart system also contemplates the use of the darts as starter devices to facilitate the placement of larger and higher profile conventional pedicle screws where necessary. In this limited view of the system, it can be viewed as a pedicle screw bore starter while eliminating the need to perform undue paraspinous muscle disturbance. 
     Moreover, as designed, one of the important aspects of the pedicle dart system involves the location of smaller fixation structures (pedicle darts) which have a lesser upward projection from the lumbar vertebra during the operation. This enables a major advance over the conventional art in which the need to place pedicle screw fixation devices before the surgical procedure often get in the way of (a) the ability to manipulate manual instrumentation to accomplish the procedure, (b) other structures used with the procedure, and (c) general visual obstruction of the surgical area. 
     The pedicle darts can be made in a variety of sizes, all of which can exhibit a much lower profile adjacent the surgical area. Conventional pedicle screws project high on the patient, perhaps to overcome the difficulty which would accompany conventional methods of accessing the conventional pedicle screws. The pedicle dart system provides instrumentation to reach in and re-engage otherwise hidden pedicle fixation devices. The pedicle dart system of the invention can also enable located re-attachment of larger pedicle darts or pedicle dart extensions to form the fixation needed. Conventional pedicle screws are typically single length devices having a proud, high profile because the use of conventional pedicle screws has no variability. Surgical practitioners have to fight so hard to get them in, they are reluctant to change them out and generally require a high profile. The pedicle dart system enables a level of flexibility not seen in conjunction with other fixation devices. 
     Further, it is not required that the darts must be able to be inserted using a thread. They can be inserted by pushing or turning, such as acting to bore into the bone using a non threaded action. Such shapes may be advantageous in removing bone in a way that will not bind or tend to put significant lateral pressure on bone tissue in the pedicle. 
     The use of the pedicle dart system provides a high number of significant advantages over the use of conventional pedicle screws.
     1. The pedicle dart system enables the use of percutaneous technique, with the result that there is much less blood loss.   2. The pedicle dart system is completely compatible with the use of bi-planer fluoroscopy or navigational method, especially with the elongated components, allowing the insertion of the pedicle dart in a much can be precise manner.   3. The pedicle dart system enables the removal of the bulky C-arm used in conventional operations, and will therefore result in greater surgeon comfort, lessening surgeon fatigue, and therefore decreasing the possibility of surgical complications.   4. The pedicle dart system facilitates placement of a temporary pedicle dart which decreases blood loss from the hole or bore in which the pedicle dart is implaced.   5. The pedicle dart system enables the use of a low-profile pedicle dart that does not interfere with retraction blades, thus allowing for greater visibility of the surgical field.   6. The pedicle dart system enables percutaneous localization of the pedicle and insertion of the pedicle dart as a marker decreases the necessity of wide muscle stripping and therefore patient damage.   7. The pedicle dart system enables the use of a technique that allows for the preservation of the vascularity and the innervation to the longissimus muscle, which always had to previously be sacrificed using the traditional (non-pedicle dart technique). The avoidance of destruction to the longissimus muscle allows for a healthier paraspinus muscle and decreases the incidence of chronic pain associated with devascularized fibrotic paraspinous tissue.   8. Traditional placement of the conventional pedicle screw has high incidence of association with breach of the pedicular wall, which can lead to serious complications. The precision placement of the trans-pedicular path using the pedicle dart technique will minimize such complications.   9. Most important, there is a significant surgical time-saving component, as lengthy muscle dissection and direct exposure will no longer be required.   10. The shortened surgical time will mean less surgical time, providing significant cost savings for the entire health-care system.   

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, its configuration, construction, and operation will be best further described in the following detailed description, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a prior art set of high profile conventional pedicle screws attached into the pedicles of two adjacent vertebrae and illustrating a fixation connector; 
         FIG. 2  is a sectional exploded view illustrating the basic components in a pedicle dart system; 
         FIG. 3  is a sectional assembled view illustrating the interfitted components of the basic pedicle dart system; 
         FIG. 4  is a plan assembled view illustrating the interfitted components of the basic pedicle dart system with a further embodiment of a pedicle dart having conically tapering exterior ribs; 
         FIG. 5  is an expanded perspective view of the pedicle dart seen in  FIG. 4  illustrating the taper and ribs; 
         FIG. 6  is an end view of the pedicle dart of  FIGS. 4 and 5  illustrating the geometric shape as having deep ribs, which are five in number; 
         FIG. 7  is an expanded perspective view of a further embodiment of the pedicle dart as having a taper, but with more shallowly formed and more numerous ribs; 
         FIG. 8  is an end view of the pedicle dart of  FIG. 7  illustrating the geometric shape as having shallow ribs, which are six in number; 
         FIG. 9  is an expanded perspective view of a further embodiment of the pedicle dart as having a conical taper; 
         FIG. 10  is an end view of the pedicle dart of  FIG. 9  illustrating the geometric conical shape; 
         FIG. 11  is an expanded perspective view of a further embodiment of a pedicle dart formed as a probe having a reduced diameter portion with an optional slight small end conical taper; 
         FIG. 12  is an end view of the pedicle dart of  FIG. 11  illustrating the geometric stepped shape; 
         FIG. 13  illustrates the pedicle dart system configured as a probe and using the probe pedicle dart seen in  FIGS. 11 and 12  with the guide pin withdrawn while using it as a probe to locate the point where the guide pin is to be inserted; 
         FIG. 14  illustrates a perspective view of the pedicle dart of  FIGS. 2 and 3  in a position to be loaded onto the end of the pedicle dart fastener and indexed sleeve; 
         FIG. 15  illustrates a perspective view of the components seen in  FIG. 14  but joined to form a complete pedicle dart system assembly ready for guide pin guided implacement; 
         FIG. 16  illustrates a partial sectional view of a vertebra with identification of component parts and with the pedicle shown in dashed line format behind the transfer process; 
         FIG. 17  illustrates insertion of a pedicle dart in comparison with the pedicle screw seen in  FIG. 1  and can be used to illustrate several aspects of the differences and possibilities for cooperation between the two structures; 
         FIG. 18  is a perspective view illustrating the initial step of guide pin location and at the point in the process where the pedicle dart has translated along the guide pin and first makes contact with the pedicle; 
         FIG. 19  is a view similar to that seen in  FIG. 18  in which the pedicle dart has been inserted and at the point where the surgical user is just about to begin turning the control knob of the pedicle dart fastener to release the pedicle dart; and 
         FIG. 20  is a view similar to that seen in  FIGS. 18 and 19  in which the indexed sleeve and pedicle dart fastener has been decoupled from the pedicle dart and is being moved away from the surgical field. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A detailed description of the preferred embodiment will be best begun by examining a perspective view of the lower lumbar vertebrae L 3 , L 4 , L 5  and sacrum S shown in perspective in  FIG. 1 . In operative procedures in which work is to be done between two adjacent vertebrae, those two vertebrae must be fixed and held apart so that the space between those vertebrae is maintained. Traditionally this has been done by using conventional pedicle screws  11 ,  13 ,  15  and  17  seen in  FIG. 1 . The conventional pedicle screws  11 ,  13 ,  15  and  17  engage significant bone mass by placement through the pedicle structure of each vertebra into which they are placed. In the three dimensional view of  FIG. 1 , the conventional pedicle screws  11 ,  13 ,  15  and  17  seem to have an open placement, during an actual surgical procedure on a patient, the pedicle screws  11 ,  13 ,  15  and  17  must be located through and despite significant layers of muscular tissue. 
     As previously discussed, dissection of the muscles surrounding the spiny process  21  of each of the vertebrae will damage the patient, permanently weaken the back and can delay or completely prohibit patient recovery. It is noted that the conventional pedicle screws  11 ,  13 ,  15  and  17  have a high profile, so high as to cause a similarly high engagement of an interconnect member  23  between conventional pedicle screws  11  and  15  and an interconnect member  25  between conventional pedicle screws  13  and  17 . The use of two such interconnect members  23  and  25  act to bilaterally stabilize the adjacent vertebrae (in this case L 3  and L 4 ) in a position as they were located prior to the surgical procedure. In the case of disc removal and implant placement it is advantageous to have the two vertebra stabilized in a natural position so that implant selection and placement into a proper space can be facilitated. 
     However, the use of the conventional pedicle screws  11 ,  13 ,  15  and  17  of  FIG. 1 , along with the interconnect members  23  and  25  create a significant interfering structure which can block access to the intervertebral space, and also can physically interfere with any retractor system used to facilitate access to the intervertebral space. Retractor systems which operate more closely to the spine are more stable and subject to greater control by the surgical practitioner. Further, when retractor system is closer to the patient, a wider view is available, all other factors remaining the same. 
       FIG. 1  also illustrates that the conventional pedicle screws  11 ,  13 ,  15  and  17  have to have an insertion point and angle which will enable the conventional linear pedicle screw to travel straight through the pedicle and into the main vertebra body. This must be accomplished with minimum damage to bone tissue, and without angling into the spine, and without simply missing its path so that it emerges from the pedicle even if it continues back into the vertebra. Any opportunity to fail to fully engage bone volume results in a probability that the conventional pedicle screws  11 ,  13 ,  15  and  17  will not hold and may fail in their contribution to fix the interconnect members  23  and  25 . 
     When it is considered that the large amounts of tissue must be removed or compromised to give the surgical practitioner the ability to locate the exact point of insertion and then to rotatably insert the conventional pedicle screws  11 ,  13 ,  15  and  17  at the correct angle, it can readily be seen that conventional pedicle screw insertion is both difficult and fraught with the possibility of error, times four. Further, because the conventional pedicle screws  11 ,  13 ,  15  and  17  have relative large diameter compared to the pedicle, the room for error which would still allow a successful insertion is reduced. 
     Referring to  FIG. 2 , an exploded view of a pedicle dart system  31  is illustrated. A guide pin  35  is preferably a solid length of material having a sharp point  37  at one end opposite a blunt end  39 . A pedicle dart fastener  41  includes a guide pin through bore  43  for enabling the guide pin  35  to easily pass through as well as to rotate. The pedicle dart fastener  41  in the embodiment shown as a main barrel  45  and a set of external threads at one end. The opposite end has an enlarged control knob  49  spaced apart from an insertion limiting land  51  to insure that the enlarged control knob  49  will be prominent and easily actuatable with regard to any type of instrumentation into which the pedicle dart fastener  41  is inserted. 
     It is understood that the use of external threads  47  to rotationally engage a pedicle dart (to be discussed) by threadable rotation to achieve attachment and axial movement, is but one of many ways this can be accomplished. Other ways include a quick key insertion, an external snap detent, or magnetic attraction or any other structure. The remainder of the structure will reveal that the external threads  47  will not undergo a static turning force and therefore no rotational pressure will be exerted on the external threads  47 . 
     An optional friction washer  55  is seen for eliminating component wear and its need will depend upon the materials chosen for the pedicle dart system. Next is seen the indexed sleeve  61 . Indexed sleeve  61  includes a main cylindrical barrel  63  having a terminal end  65  with a pair of fingers  67  extending beyond the terminal end  65 . The indexed sleeve  61  has a central bore  69  through which the main barrel  45  of the pedicle dart fastener  41  may freely pass and rotate. A pair of handles  71  and  73  extend away from the end of the indexed sleeve  61  to facilitate manual rotation of the indexed sleeve  61  with some level of manual force. 
     To the right of the indexed sleeve  61 , a pedicle dart  77  is shown in cross section. As will be seen, although the pedicle dart  77  can have a variety of functional structures, the pedicle dart  77  shown in  FIG. 2  has a threaded conical exterior and internally threaded surfaces. 
     Beginning at the left, the pedicle dart  77  has a pair of fingers  79 , only one of which is seen due to the cross sectional nature of the drawing. The fingers  79  of the pedicle dart  77  interlock with the fingers  67  of the indexed sleeve  41  and will ideally extend all the way to the terminal end of the indexed sleeve. An end  81  of the pedicle dart  77  defines the point that the pedicle dart  77  fingers  79  extend rearwardly of it. The ends  81  accommodate the terminal ends of the fingers  67  of the indexed sleeve  41  extending toward the pedicle dart  77  to rotationally engage it. 
     Pedicle dart  77  has a bore  83  having an internal threaded surface  85  which is complementary to the threaded surface  57  of the pedicle dart fastener  41 . Beyond the internal threaded surface  85 , the pedicle dart  77  has a guide pin bore  89  which extends through the pedicle dart  77  and opens at a tip end  91  of the pedicle dart  77 . As can be seen, when the pedicle dart  77  is brought close to the end  65  of the indexed sleeve  61  such that the fingers  67  of the indexed sleeve slide past the fingers  79  of the pedicle dart  77 , any rotational force applied to the indexed sleeve will be transmitted to the pedicle dart  77 . Pedicle dart  77  is also seen as having an externally threaded surface  93  for boring into bone tissue. A spiral cutting thread can be used, but also other non-spiral cutting surfaces, such as a ribbed cone with tapered radiating relatively angled members for an even bore, or a conical rasp. 
     So long as the pedicle dart  77  is in close relationship with the indexed sleeve  61 , the fingers  67  and  79  will directly transfer any turning or movement of the indexed sleeve  61  through to the pedicle dart  77 . In essence, the indexed sleeve  61  becomes a long device which can have its tip member selectively attached or removed. The pedicle dart fastener  41  serves several. First it can engage or disengage the pedicle dart  77 . Secondly, it can pull the pedicle dart  77  closer enough to the indexed sleeve  61  that the fingers  67  and  79  will engage each other. Third, it keeps the pedicle dart  77  and index sleeve centered to insure that the engagement of the fingers  67  and  79  are even and both rotate fully engaged around a common axis. 
       FIG. 2  illustrates that the guide pin  35  can be freely inserted into the guide pin bore  43  at any time and from either end of the guide pin bore  43 . The guide pin  35  can be used independently with the combination pedicle dart  77 , indexed sleeve  61  and main cylindrical barrel  63  assembled as a unit. In other words, the guide pin  35  can be inserted either by gentle force or by gentle tapping to locate a point of insertion. The guide pin  35  is used as an easy-to-handle, long object which can be oriented to indicate the angle at which the pedicle dart  77  is to be inserted. Then, the combination pedicle dart  77 , indexed sleeve  61  and main cylindrical barrel  63  assembled as a unit can be guided over the blunt end  39  of the guide pin  35  and then slid along the guide pin directly to the exterior of the pedicle. A few turns of the combination of the pedicle dart  77 , indexed sleeve  61  and main cylindrical barrel  63  assembled as a unit will result in some of the externally threaded surface beginning to engage the bone tissue of the pedicle. Once insertion of the pedicle dart  77  begins, the guide pin  35  can be withdrawn while the remainder of the pedicle dart system  31  is turned to put the pedicle dart  77  fully into the bone tissue. 
     Once the pedicle dart  77  is fully inserted, the surgical practitioner can manually turn the enlarged control knob  49  in a direction that will back the set of external threads  47  of the main barrel  45  out of the threaded surface  85  of the pedicle dart  77 . This action enables the pedicle dart  77  to begin to move forward with respect to the indexed sleeve  61  to enable the fingers  67  of the main cylindrical barrel  63  to disengaged from the pair of fingers  79  of the pedicle dart  77 . Further turning of the enlarged control knob  49  enables the pedicle dart fastener  41  to become completely disengaged from the pedicle dart  77 . 
     The same process can be followed in reverse to re-engage the pedicle dart  77 . The combination of the indexed sleeve  61  and main cylindrical barrel  63  assembled as a unit with the indexed sleeve  61  urged forward will cause the set of external threads  47  of the indexed sleeve  61  to protrude forward of the fingers  67  and in a position to find and engage the internal threaded surface  85  of a pedicle dart  77 . Turning the enlarged control knob  49  in a direction that will begin to engage the set of external threads  47  of the pedicle dart fastener  41  into threaded surface  85  of the pedicle dart  77  will begin to draw the pedicle dart  77  toward the indexed sleeve  61 . Slight turning of the indexed sleeve  61  will cause the fingers  67  to assume a complementary position with respect to the fingers  79  of the pedicle dart  77 , with fingers  67  and  79  sliding past each other to enable rotational re-engagement of the indexed sleeve  61  with the pedicle dart  77 . This same procedure is used for both loading a new pedicle dart  77  by hand and for re-engaging a pedicle dart  77  which may have previously been implaced in bony tissue. In the latter case, once re-engaged, the indexed sleeve  61  can be used to extract the pedicle dart  77 . The technique of extraction will depend upon the type of pedicle dart  77 , as will be shown. Where the externally threaded surface  93  is present, turning to loosen the threads of the externally threaded surface  93  sufficient to disengage such externally threaded surface  93  will precede simple extraction. 
     Referring to  FIG. 3 , a sectional view illustrating the assembled pedicle dart system  31  is seen. The guide pin  35  is preferably much longer than the pedicle dart fastener  41  so that a sufficient length of the guide pin  35  will be available for easy manipulation. The pedicle dart fastener  41  can be withdrawn back through the main barrel  45  of the indexed sleeve  61  main cylindrical barrel  63 , and an optional structure can be present to stabilize the pedicle dart fastener  41  longitudinally with respect to the main barrel  45  of the indexed sleeve  61 . Such optional structure may include a set screw extending through the main barrel  45  of the indexed sleeve  61  to engage a reduced land on the pedicle dart fastener  41 , or some other spring detent can be used. Any optional structure should be configured with a mind toward facilitating sterilization of this instrument. 
       FIG. 4  is a plan assembled view illustrating the interfitted components of the basic pedicle dart system  31  with a further embodiment of a pedicle dart seen as pedicle dart  95 . Pedicle dart  85  has conically tapering exterior ribs  97  and illustrates that the pedicle dart system  31  is not limited to an externally threaded entry into bone tissue. The conically tapering exterior ribs of pedicle dart  95  will enable more of a concentrically even wearing effect by which bone entry is accomplished. This also reduces the possibility that the adjacent tissues might be overly compressed from the action of externally threaded surface  93  combined with forward pressure applied by a surgical practitioner. In effect, the surgical practitioner can select the particular pedicle dart  77  or  95  desired for use given the bone tissue conditions. 
     Referring to  FIG. 5 , an expanded perspective view of a portion of the pedicle dart  95  is seen in a position below the terminal end  65  and pair of fingers  67  seen in previous figures. The relatively deep tapered rib section  97  is seen. Referring to  FIG. 6 , an end view of the pedicle dart of  FIGS. 4 and 5  illustrates the geometric shape as having deep ribs, which are seen to be five in number. 
     Referring to  FIG. 7 , an expanded perspective view of a further embodiment of a pedicle dart  101  as having a tapered rib section  103 , but with more shallowly formed and more numerous ribs. Referring to  FIG. 8 , an end view of the pedicle dart  101  of  FIG. 7  illustrating the geometric shape as having shallow ribs within its tapered rib section  103 , which are six in number. 
     Referring to  FIG. 9 , an expanded perspective view of a further embodiment of the pedicle dart is seen as a pedicle dart  105  as having a conical taper  107 . This embodiment can be used where the bone tissue is soft or where the surgical practitioner wants only a small or force determined opening or starter aperture in the bone tissue. Referring to  FIG. 10 , an end view of the pedicle dart  105  of  FIG. 9  illustrating the geometric conical shape taper  107 . 
     Referring to  FIG. 11  an expanded perspective view of a further embodiment of a pedicle dart  111  formed as a probe having a reduced diameter portion  113  with an optional slight small end conical taper  115 . The pedicle dart  111  is especially useful with an indexed sleeve  61  used as a probe to move tissues and “feel”, in addition to looking for pedicle placement. Thereafter the guide pin  35  can be employed to make an impression on the spot on the pedicle where further activity is to occur. In that case, the assembly including the indexed sleeve  61 , pedicle dart fastener  41  and pedicle dart  111  can be removed from the guide pin  25 , then loaded with pedicle darts  105 ,  95 ,  101  or  77  and then re-inserted over the guide pin  35  for further pedicle dart insertion activity. Referring to  FIG. 12 , an end view of the pedicle dart  105  of  FIG. 11  is shown and illustrating the geometric stepped shape. 
       FIG. 13  illustrates the pedicle dart system configured as a probe and using the probe pedicle dart  111  seen in  FIGS. 11 and 12  with the guide pin  35  withdrawn while using it as a probe to locate the point where the guide pin  35  is to be inserted. Also illustrated is a slightly differently shaped enlarged control knob  49  as having a more spherical appearance. 
     Referring to  FIG. 14 , a perspective view of the pedicle dart  77  of  FIGS. 2 and 3  is shown in a position to be loaded onto the end of the pedicle dart fastener, of which only the tip end having threads  47  is seen, and in which the guide pin  35  is optionally present to aid in alignment. Guide pin  35  is not required for attachment of the pedicle dart  77  but guide pin  35  insertion will automatically concentrically align the pedicle dart  77  so that the only other alignment is rotational, to align the fingers  79  with fingers  67 . Fingers  79  are seen as optionally having a greater radial extent while the fingers  67  have a lesser radial extent, but this need not be the case. Further, instead of using two fingers on each component (pedicle dart  77  and the end of the main barrel  45 ), one finger, three fingers, or four or more fingers could be used. Note that the threaded surface  47  of the end of pedicle dart fastener  41  extends slightly beyond the most distal ends of the fingers  67  so that the internal threaded surface of the pedicle dart  77  may be engaged before the fingers  67  and fingers  79  need be rotated out of any interfering alignment. 
     Referring to  FIG. 15 , a perspective view of the components seen in  FIG. 14  are shown as joined to form a complete pedicle dart system  31  assembly ready for guide pin  35  guided implacement. 
     Referring to  FIG. 16 , a partial sectional view of a vertebra with identification of component parts and with the pedicle  121  shown in dashed line format behind the transfer process is given for further reference. Referring to  FIG. 17 , an illustration of insertion of a pedicle dart  77  is shown in comparison with the conventional pedicle screw  11  seen in  FIG. 1  and can be used to illustrate several aspects of the differences and possibilities for cooperation between the two structures. The conventional pedicle screw  11  is also seen has having a compression screw  131  which operates within a housing  133  to compress the interconnect member  23 . 
     First, it can be noted that the pedicle dart  77  is smaller and shorter than the conventional pedicle screw  11 . The pedicle dart  77  is shown in a location where it has been only half way inserted into the pedicle. It can be inserted further in or less further in. Conventional pedicle screw  11  is seen as having a proud high appearance. With the conventional pedicle screw  11  the surgical view is obstructed in terms of height. The pedicle dart  77  however can go deeper into the bony mass to have a low profile appearance which interferes less with other surgical instrumentation and structures and yet still marks the angle and location. Further, the internal threaded surface  85  of the pedicle dart  77  (not seen in  FIG. 17 ) which is used to engage set of external threads  47 , can similarly be used to anchor other interconnect structure used during the operation where permissible. 
     However, one of the main purposes for the pedicle dart is to more easily “start” the path into the bone tissue, for both angle and location. In many operations the pedicle darts  77  may be implaced for only  30  minutes before either being removed or supplemented by other different sized structures threadably or otherwise inserted into the bone tissue, especially where greater depth, greater diameter, or other characteristics are desired. Other different sized structures may be expected to be inserted and removed by virtue of their compatibility with the pedicle dart system  31  of the invention. 
     Referring to  FIG. 18 . a perspective view is used to illustrate the initial step of initial contact of the pedicle dart  77  with the pedicle dart system  31  at a point in time after the guide pin  35  has used, with or without the probe configuration seen in  FIG. 13 , for marking location where the pedicle dart is to be inserted. It is at this time that the surgical practitioner angularly orients the pedicle dart system  31  so that further manipulation of the pedicle dart system will result in the linear entry path desired. The pedicle dart  77  is shown as being securely attached so that rotation of the indexed sleeve will result in rotation of the pedicle dart  77 . The view illustrates a time just before the rotation of the components of the pedicle dart system  31  begins, with the combination pedicle dart fastener  41 , indexed sleeve  61 , and pedicle dart  77  translated along the guide pin  35  first making contact with the pedicle  121 . 
     Referring to  FIG. 19  is a view similar to that seen in  FIG. 18  in which the pedicle dart has been inserted to a depth of about half of its length and at the point where the surgical user is just about to begin turning the control knob  49  of the pedicle dart fastener  41  to release the pedicle dart  77  and just after the turning operation has ceased. 
     Referring to  FIG. 20 , a view similar to that seen in  FIGS. 18 and 19  is shown in which the indexed sleeve  61  and pedicle dart fastener  41  has been decoupled from the pedicle dart  77  and is being moved away from the surgical field. The practitioner would repeat the process of  FIGS. 18-20  to insert as many pedicle darts as necessary. Ideally, the pedicle dart may be a tapered, cylindrical device having a sharp point at one end leading to self-tapping threads  93  on the outer surface for approximately 75% of its length. The opposite end is flat, and may be male or female indexed to match the female or male index, respectively on the indexed sleeve  61 . The center of the pedicle dart  77  may be cannulated to accept the guide pin  35 . 
     It is clear that the pedicle dart system of the invention can be modified to handle a wide variety of Procedures. The material used for all components of the pedicle dart system should be capable of withstanding sterilization and impact. Different materials may be employed based upon the forces and interconnection forces expected to be encountered. Although the pedicle dart system  31  can be used in many different types of surgical procedures, an example involving minimally invasive surgery transforaminal lumbar interbody fusion (MIS TLIF) will be described as one of those examples. 
     MIS TLIF Procedure 
     
         
         1. Insert any guide pin to identify the level of the lumbar disk to be removed. 
         2. Make a midline incision centered over the guide pin  35  appropriate for the levels of surgery to be performed, which is usually the distance from the tip of the spinous process of the levels to be fused. 
         3. Undermine the full thickness of the skin 2-3 cm circumferentially to allow the incision to be moved in all directions. 
         4. Make a fascial incision 1-2 cm lateral to the spinous processes. Insert Cobb elevator and sweep the multifidus muscle off the spinous processes and lamina and lateral to the facet joint. Insert MIS retractor with the proper blade length and shape and open the retractor blades to retract the soft tissue from the interlaminar space. The inverted “V”-shaped space thus created allows for excellent visualization for the laminectomy/diskectomy. 
         5. Fasten the retractor to the universal arm attached to the surgical table to stabilize the retractor if desired. 
         6. Perform a facetectomy if TLIF procedure is to be performed. Take precaution not to injure the exiting root cephalad to the disk and use a dural retractor to retract the dura and traversing root medially. 
         7. Perform a complete diskectomy. Prepare the disk space and insert the inter body cage of choice. A more lateral Wiltse approach to be described next can be used for inserting a longer “banana” TLIF cage for safer insertion. 
         8. Remove the MIS retractor and make another longitudinal fascial incision on the lateral border of the Longissimus muscle. The location of this fascial incision can also be determined by the location of the pedicle darts  105 ,  95 ,  101  or  77  as visualized with the C-arm. Insert a Cobb elevator to sweep the muscle off of the transverse processes and lateral facet joints. Insert the MIS retractor of the appropriate blade length and open the retractor blades sufficient to visualize the operative area of interest. If the fascial incision appears to be too lateral, the fascial incision can be made more medially and a “true” Wiltse muscle-splitting approach can be utilized. Deploy the retractor blades cephalad-caudally. Medial/lateral retraction may be necessary. On the medial side, a hook retractor should be used, and laterally, a blade retractor would be more effective to retract the muscle. 
         9. Following placement of the TLIF cage, the proud head of the pedicle dart  105 ,  95 ,  101  or  77 , can be engaged easily due to the indexed sleeve  61 . Remove the pedicle dart  105 ,  95 ,  101  or  77 . The appropriate conventional pedicle screw can then be inserted through the hole prepared by the pedicle dart, and the contoured rod can then be applied to the heads of the conventional pedicle screw. The construct can then be compressed, and the locking screws tightened over the rod. The MIS retractor is then removed.
 
Internal Fixation of the Opposite Side
 
         1. Move the midline incision to the opposite side. 
         2. Make a longitudinal fascial incision on the opposite side to begin the Wiltse approach. Using muscle-sparing technique, strip the muscle attachments on the transverse processes. Insert the MIS retractor with the appropriate length retractor blades, and then open the blades Cephalad-Caudally to expose the heads of the pedicle dart  105 ,  95 ,  101  or  77 . Deploy medial/lateral retractor as required for sufficient exposure. Decorticate the transverse processes and lateral surface of the facet joint. Remove the pedicle dart as described before and replace with the final conventional pedicle screw  11 . Insert the appropriate interconnect member  23  into the conventional pedicle screw head housing  133 ; then compress and tighten the locking screws  131 . Apply bone graft to the decorticated postero-lateral gutter, then remove MIS retractor. Suture the fascial incisions with appropriate suture material of choice and close the wound in the usual fashion. 
       
    
     While the present system has been described in terms of a system which includes instrumentation, procedures and wide range of purposes to facilitate a difficult surgical task, one skilled in the art will realize that the structure and techniques of the present system can be applied to many instruments, including any instrument which has the ability to transmit high torque, selective attachment and detachment, and which accentuates the location and angle of approach of an entry into any point in the human body. 
     Although the system of the invention has been derived with reference to particular illustrative embodiments thereof, many changes and modifications of the systems shown may become apparent to those skilled in the art without departing from the spirit and scope of the inventive system. Therefore, included within the patent warranted hereon are all such changes and modifications as may reasonably and properly be included within the scope of this contribution to the art.