Patent Publication Number: US-2023149047-A1

Title: Methods and apparatus for guided spinal growth

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 63/007,597, filed Apr. 9, 2020, and U.S. Provisional Patent Application Ser. No. 63/106,564, filed Oct. 28, 2020, both of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     Various embodiments described herein pertain to methods and apparatus that facilitate positional readjustment of vertebra relative to one another, such as in a surgical procedure using rods that are slidably received by a bone attachment device, and including those attachment devices using a separate low friction bushing that permits sliding but limits translational movement of the rod in lateral and vertical orientations. 
     SUMMARY OF THE INVENTION 
     Various embodiments shown herein pertain to bone anchors that place boundaries on the movement of a spinal rod, while simultaneously permitting the rod to move axially. 
     In some embodiments the rod is able to rotate within a bushing and relative to the bone anchor assembly in roll (about the rod axis) and pitch and yaw (both perpendicular to the rod axis). In yet other embodiments the bushing and rod are able to rotate relative to the bone anchor assembly in roll (about the anchor attachment to the bone) and pitch and yaw (both perpendicular to the anchor attachment to the bone). Still further embodiments contemplate combinations of any of the aforementioned rod relative motions and any of the aforementioned bushing and rod relative motions. 
     Various embodiments include a tulip-type anchoring head that includes within it a low-friction bushing that comes into contact with a spinal rod. It has been found in some patients that the use of a metallic bushing can result in metal particles deposited in the patient as a result of the relative motion of a metal rod against a metal head. These of a polymeric bushing can assist in resolving this problem, and also the use of a bushing of any material that is fabricated from a hard, low-friction, biologically acceptable material, such as a ceramic or metal. One examples of such a metal contains cobalt and chromium. 
     In some embodiments the polymeric bushings are fabricated from a high density polyethylene material, polyetheretherketone (PEEK), or other biologically acceptable, non-metallic material. In some embodiments the polymeric bushing is a separate component that is inserted into the head of the device. In yet other embodiments, the polymeric bushing is contained within a container, such that the separable container is attached to the head. In still further embodiments the polymeric bushing is a coating of polymeric material that can be applied to a surface of the head or to the surface of a separable container. 
     In some embodiments, the bushing (polymeric, metallic, or ceramic) is a closed pathway having two opened ends, through which the rod is inserted. In still other embodiments the bushing can be in multiple pieces, preferably with one of the bushing pieces defining an open pathway having two opposing ends. In such multi-piece bushings the rod can be inserted into the bushing in a direction orthogonal to the direction of the pathway. 
     In some embodiments, the bushing whether separable or integral with the head, is restrained by the head in a single static position, such that movement of the rod does not result in movement of the bushing. In still other embodiments the exterior of the bushing has a shape that coacts with the interior shape of a pocket (either of the head or a container) such that the rod pathway through the bushing can pivot in one or two directions (such as pitch or yaw) relative the head of the guiding retainer assembly. 
     In some embodiments, the bushing aperture through which the rod is placed has a shape that is substantially the same as the exterior shape of the rod, although with provisions (such as clearance around the perimeter) to permit relative sliding motion of the rod. In still further embodiments the interior shape of the bushing pathway has an interior width that is greater than the width of the rod, such that side to side motion of the rod relative to the bushing is permitted. 
     Various embodiments include means for retaining a bushing within a head. Such retaining means can include a set screw having external threads that is received within an internally threaded pocket of the head. In still further embodiments the set screw can have internal heads that are received onto exterior threads of the head or other device. In some embodiments the means for retaining can be a set screw that is oriented generally perpendicular to the rod pathway, and in some embodiments being centered across the width of the bushing and in yet other embodiments offset to one side of the bushing. In still further embodiments the means for retaining the bushing can be a c-clip that is received within a groove of the head, and capturing the bushing between the c-clip and the internal pocket of the head. 
     Preferably, the full tightening of the set screw or locking of other retaining device does not compress the bushing against the surface of the rod so much as to prevent sliding of the rod, especially for sliding that results from the motion of one vertebra relative to another vertebra, or from the actions of the surgeon. Preferably, those embodiments utilizing set screws include a travel-stop feature that limits the full travel of the set screw from compressing the bushing against the surface of the rod when fully the set screw is fully tightened. 
     Still other means for retaining the bushing contemplate bushings within separable containers (the bushings either separately installed or molded within the container), with the container and a head being adapted and configured to securely locate the container on the head. As one example, the container can include a separable bushing, in some embodiments the ends of the bushing extending outwardly from the edges of the container, and in other embodiments remaining flush with the container edges. The container includes one or more head retention features that coact with a corresponding bushing retention feature on the head to securely locate the container and bushing relative to the head. As one example, the head retention features can include one or more projections, preferably on opposite sides of the container exterior that coact with hinged members located on the head, such that the placement of the container within the head causes the bushing retention features to deflect outward (being retained on the head by live hinges), and then snap back into a retaining position once the head retention features are lower than the bushing cantilever arms. 
     In yet another embodiment the bushing container includes one or more flexible arms (by way of live hinges), such that the container can be compressed onto the head with the arms springing outward to pass over locking features on the head during insertion, and then snapping back into place in a locking manner after the bushing container is fully received on the head. 
     In still further embodiments of the present invention the means for retaining the bushing includes heads that are pre-loaded with a bushing (either separable or moldedin), in which can be retained as a single unit on the bone supporting device. As one example, the head includes a head having a receiving pocket that can be popped onto the head of a supporting device, such as by use of a compression tool. 
     Preferably, either the head of the supporting device or the interior of the head pocket is lined with a polymer, metal, or ceramic to act as a bearing and permit one or two axes of relative motion. In yet another embodiment the head is adapted and configured proximate to the device receiving pocket to receive a lockable sliding member. When the sliding member is in an opened position, the assembly of the head, bushing, and sliding member can be placed readily on top of the supporting device. After placement, the sliding device can be pushed into locking engagement with the head, and further capturing the supporting device to the head. 
     In still further embodiments the head of the guiding retainer can be attached by a flexible connector to the vertebra, with some embodiments including a spiked bone interface on the bottom of the head. In such embodiments the flexible connector can be wrapped around the vertebra and captured within the head. 
     Still further embodiments contemplate the use of a flexible connector to attach the bushing to the head, such as a head having a groove or channel in which to locate the bearing, with attachment slots located on either side of the groove. The flexible connector can be wrapped around the exterior of the bushing, with the ends of the connector being attached to the head slots. In yet another variation, the flexible connector is wrapped around the rod directly, such that the wrapping of the flexible connector provides the polymeric pathway for the rod. The ends of the wrapped connector can be attached to the head with any degree of looseness as desired by the surgeon, thus permitting axial movement of the rod, as well as polyaxial pivoting of the rod relative to the head. 
     Still further embodiments of the present invention contemplate a bushing that is supported within a separable container, the container including a support arm, the support arm being coupled to the head and locked to the head. In such embodiments, the pathway for the rod can be laterally offset from the head. 
     Various embodiments of the present invention contemplate various means for supporting the head from a vertebra. In some embodiments, the head is fixed to a supporting device such as a bone screw. In still further embodiments, the head is coupled to a bone screw by means of a joint that permits a single axis of pivotal movement of the head relative to the supporting device. In still further embodiments, the interface between the supporting device and the head permits polyaxial movement of the head relative to the supporting device (along either two axes or three axes). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some of the figures shown herein may include dimensions. Further, the figures shown herein have been created from scaled drawings, scaled models, or from photographs that are scalable. It is understood that such dimensions, or the relative scaling within a figure, are by way of example, and not to be construed as limiting unless so stated in a claim. Persons of ordinary skill will also recognize that CAD renderings may include lines that pertain to changes in the geometry of the computer model, and not necessarily to component features. 
         FIG.  1    is a top, side perspective view of a model of a spine having a pair of rods attached to the spine according to one embodiment of the present invention. 
         FIG.  2    is a top, perspective view of the apparatus of  FIG.  1 B  from the other side. 
         FIG.  3    is a close-up of a portion of the apparatus of  FIG.  1 A   
         FIG.  4    is a close-up top, perspective view of a spine model with two rods attached to the model according to another embodiment of the present invention. 
         FIG.  5 XY  show various embodiments with various arrangements of bushings and heads, each of which is discussed with regards to other figures;  FIG.  5 AY  shows six different arrangements of top loaded bushings, A 1 , A 2 , A 3 , A 4 , A 5 , and A 6 , each captured within the head with different methods and apparatus;  FIG.  5 BY  shows three configurations of heads, B 1 , B 2 , and B 3 , in which the bushings are loaded by laterally sliding the bushings into the cavity;  FIG.  5 CY  shows two configurations, C 1  and C 2 , in which the heads receive the bushings with a tip of the bushing being inserted at an angle into the head; and  FIG.  5 DY  shows four arrangements of heads, D 1 , D 2 , D 3 , and D 4 , in which the bushings are integral with the head. 
         FIG.  6 X  show an anchor in which the bushing is in multiple segments;  FIG.  6 A  shows the anchor assembled with a rod from a top perspective view;  FIG.  6 B  shows an exploded end view of the apparatus of the  FIG.  6 A ;  FIG.  6 C  shows a further exploded view of a portion of the apparatus of  FIG.  6 B ; and  FIG.  6 D  shows a cross sectional end view of the apparatus of  FIG.  6 A  with the cross section being taken through the centerline of the screw and perpendicular to the axis of the rod. These devices include bushing-rod interfaces on multiple different components. In some embodiments these components are assembled together at the time of surgery. 
         FIG.  7 X  show an anchor in which the bushing and bushing container are loaded separately from the top;  FIG.  7 A  shows a top, perspective view of a partly assembled anchor head;  FIG.  7 B  shows an assembled view of the apparatus of  FIG.  7 A ;  FIG.  7 C  is a cross sectional, side view of the apparatus of  FIG.  7 B , as exploded from a view of another bushing container;  FIG.  7 D  shows the assembly of  FIG.  7 C ;  FIG.  7 E  is a perspective, top, side view of the apparatus of  FIG.  7 D  with a bushing inserted; and  FIG.  7 F  is a perspective, cross sectional cutaway of the apparatus of  FIG.  7 E . These devices provide an alternative construction to a press-fit sleeve or bushing, and are useful in many different embodiments shown herein. Further, these devices can also be used with integral bushings. 
         FIG.  8    is a side elevational cross sectional representation of an anchor  10  having a bushing with an internal spherical surface, and illustrating the articulation of the inserted rod. This device allows for angulation of the rod with preferably no moving parts except for the rod itself. 
         FIG.  9 X  compare the spatial envelopes of two different anchors; FIG.  9 A 1  shows an exploded anchor with a fixed head, an oblong cross section, slide-loaded bushing; FIG.  9 A 2  depicts the assembly of the anchor of FIG.  9 A 1 ;  FIG.  9 B  shows a different anchor with a polyaxial attachment and a circular rod cross section;  FIG.  9 C  shows the anchor of  FIG.  9 A , with various external dimensions compared to the anchor of  FIG.  9 B ;  FIG.  9 D  shows the rod maximum articulation envelope (Range of Movement, or ROM) of the anchor of  FIG.  9 B ; and  FIG.  9 E  provides a side-by-side comparison with  FIG.  9 D . Preferably, these embodiments include a cross linked organic material with the bushing. In some embodiments a fixed screw is used with a slide-loaded oblong bushing, the bushing providing mobility. Preferably, some of these embodiments include a low profile after implantation so as to reduce internal irritation within the patient.  FIG.  9 D  illustrates the rod ROM (range of movement).  FIG.  9 E  shows that a fixed screw in some embodiments achieves additional protection of the patent tissue from encroachment by the head of the screw. 
         FIG.  10    show various anchors  10  with integral bushings;  FIG.  10 A  shows a bushing with an oblong interior and oblong exterior;  FIG.  10 B  shows a bushing in a similar anchor with a cylindrical internal cross section and oblong exterior;  FIG.  10 C  shows the bushing of  FIG.  10 B  with the rod pathway offset from the fastener centerline;  FIG.  10 D  shows an opposite-hand version of the anchor of  FIG.  10 C ;  FIG.  10 E  shows the anchor of  FIG.  10 A  with an installed rod (in cross-section) having width that is greater than the height of the busing, so as to limit rotation of the rod. Some of these devices permit an oblong aperture to be converted to a fixed or offset-fixed rod retention envelope. It is thought that the restricted motion may improve the correction of the patient&#39;s spine. In some embodiments the same screw base can be utilized, such that one screw can provide four different rod placement options. 
         FIG.  11 X  show various views of an anchor with a spherical bushing;  FIG.  11 A  is an assembled, top and side perspective view, partly transparent, of an assembled anchor supporting a bushing with a spherical bushing permitting two dimensional rotation of the bushing;  FIG.  11 B  is an exploded view of the anchor of  FIG.  11 A ;  FIG.  11 C  is a side elevational cross sectional representation of the anchor of  FIG.  11 B  containing a rod;  FIG.  11 D  is a side elevational view of the anchor of  FIG.  11 B ; and  FIG.  11 E  shows an anchor similar to that of  FIG.  11 D , except using a polyaxial junction between the head and the support device, and a bushing with a cylindrical outer surface not rotatable within the head. In some of the devices shown herein the bushing is adapted and configured so as to minimize binding of the rod by placement of the point of rotation on the rod axis. In yet other embodiments, a spherical bushing eliminates the screw head to rod moment arm illustrated in  FIG.  11 E . 
         FIG.  12 X  show various views of an anchor;  FIG.  12 A  is a top, side perspective exploded view of an anchor;  FIG.  12 B  is an end elevational view of the partly assembled apparatus of  FIG.  12 A ;  FIG.  12 C  is a side elevational cutaway view of the assembled anchor of  FIG.  12 B ;  FIG.  12 D  shows a portion of the anchor of  FIG.  12 A  showing the busing and busing container and a means of interlocking;  FIG.  12 E  is an external, top, side perspective view of the apparatus of  FIG.  12 C  with the bushing of  FIG.  12 D  locked in place;  FIG.  12 F  is a side cross sectional view, similar to  FIG.  12 C  but taken parallel to the rod axis, and showing the convex internal shape of the rod pathway; and  FIG.  12 G  is a perspective view from above of the partially assembly anchor of  FIG.  12 F . Various of these embodiments include a metal-lined bushing that is reduced into the head of the tulip device, and preferably providing a low profile implantation with less than about fifteen millimeters from the top of the implanted device to the bone surface. Various devices used an unlocked, low-friction junction. Some devices include a metal shell having a taper-lock  56   a  and snap-teeth  26   b  that can be used in place of a set screw. In some embodiments, these devices function with a traditional driver and reducer. The embodiment shown in  FIG.  12    includes an integral polymer bushing that is contoured and metal lined, in one embodiment. It is supported by a traditional tulip with a polyaxial, polymer-lined junction. The bushing is retained with taper locks and/or snap teeth and live hinges. Still further variations include bushing designs that are oblong, modular oblong, and spherical. Still further, wrap-around saddles are contemplated, and further the use of concentric set screws for bushing retention, as non-limiting examples of variations. Further contemplated are bushings or bushing portions of the head that are adapted and configured for loose, low friction support of the rod, and fabricated or coated with polymeric, metallic, or ceramic materials. 
         FIG.  13 XY  show various means for supporting a bushing container from the head;  FIG.  13 A  shows six different attachment heads, A 1 , A 2 , A 3 , A 4 , A 5 , and A 6 , including tulip, slide load, and integral attachment heads;  FIG.  13 B  shows attachment heads and supporting devices that are modular, including B 1  for slide-lock coupling and B 2  for push and snap on coupling;  FIG.  13 C  shows bushing support devices C 1 , C 2 , and C 3  that are modular outriggers; and  FIG.  13 D  shows an anchor in D 1  (perspective cross section), D 2  (perspective assembly) and D 3  (perspective exploded) with a modular outrigger and related screw. In the device shown as FIG.  13 C 2 , it can be seen that the spinal attachment device is shown with slots adapted and configured for a band (such as with BandLoc™). it is understood that this device would also work with a pedicle screw having a tulip head. 
         FIG.  14    show various views of the anchor of FIG.  13 C 3 ;  FIG.  14 A  shows a partial assembly of an anchor in a top, side, perspective orientation;  FIG.  14 B  shows an exploded view of the anchor;  FIG.  14 C  shows the assembled view of the anchor of  FIG.  14 B ;  FIG.  14 D  shows a cross sectional representation of a fully assembled anchor, from a top, side perspective orientation; and  FIG.  14 E  shows the external view of the apparatus of  FIG.  14 D . Various embodiments shown herein include an “inline” outrigger device that preferably moves the polymer bushing (or bushing with polymeric, metallic, or ceramic surfaces for contact with the rod) outside the profile of the device tulip head. As shown in  FIG.  14 D  the rod outer diameter after insertion is clear of the inside  24   b  of the tulip because the rod is supported by the pair of bushing bearing surfaces that roughly match the rod O.D, whereas the inside  24   b  of the tulip is a larger, clearance diameter relative to the rod O.D. 
         FIG.  15 X  show various views of an anchor according to another embodiment of the present invention;  FIG.  15 A  shows a top, side, perspective view of an assembled anchor coupled to a rod;  FIG.  15 B  is a side, top, perspective representation of a portion of the apparatus of  FIG.  15 A ;  FIG.  15 C  is a side elevational cross sectional view of the apparatus of  FIG.  15 B ; and  FIG.  15 D  is a side, top perspective enlargement of the apparatus of  FIG.  15 B . Devices according to some embodiments of the present invention include a band that is loosely wrapped around the rod. In this manner, the rod is retained to the anchor, but the rod can move. Preferably, the band in some embodiments directly wraps around the rod. Still further embodiments, such as that shown in  FIG.  15 D , utilize a fixe anchor with a buckle-style attachment to the band. 
         FIG.  16 X  show an alternative anchor to the anchor of  FIG.  15   ;  FIG.  16 A  is an end view of a cutaway of an anchor according to another embodiment of the present invention; and  FIG.  16 B  is a top, side, perspective representation of a portion of the apparatus of  FIG.  16 A . Various embodiments disclosed herein pertain to implantable devices having a band that wraps around the polymer bushing. In some embodiments a polyester band wraps around a UHMWPE bushing, the band having a metal retaining clip on one end, and being pulled tight through a sliding lock mechanism  44   c  in order to reduce and retain the bushing. 
         FIG.  17 X  show various views of an anchor according to another embodiment of the present invention;  FIG.  17 A  is a side, top, perspective view of an assembled anchor according to another embodiment of the present invention;  FIG.  17 B  is an exploded view of the anchor of  FIG.  17 A ;  FIG.  17 C  is a side elevational cross sectional view of the apparatus of  FIG.  17 A ; and  FIG.  17 D  is a view of the apparatus of  FIG.  17 C  with exemplar dimensions. Various embodiments disclosed herein pertain to a device open from the top, with the bushing being reduced into place within the tulip. Preferably, there is a locking polymer junction that results in a minimization of any excess debris at the interface, and in some embodiments less range of motion. A wrap around middle saddle transfers a compression load past the polymer bushing. Preferably, the devices of  FIG.  17    can be pivotal in either a polyaxial or uniaxial configuration. Further, a similar concept can be used with a cylindrical or contoured bushing. 
         FIG.  18 X  provide comparisons of alternative anchors according to different embodiments of the present invention; FIG.  18 A 1  illustrates that the anchor of FIG.  18 A 2  permits rotation of the head relative to the bone screw in 3 orthogonal axes; FIG.  18 A 2  shows an exploded view of a slide loaded bushing on a polyaxial support device;  FIG.  18 B  shows a device similar to that of  FIG.  18 A , except using a top loaded bushing;  FIG.  18 C  shows an anchor similar to that of  FIG.  18 A , except with a closed head;  FIG.  18 D  shows an exploded view of an anchor similar to that of  FIG.  18 A , except with uniaxial attachment to a support device;  FIG.  18 E  shows a device similar to that of  FIG.  18 B , except with a uniaxial support device; and  FIG.  18 F  shows a device similar to that of  FIG.  18 C , except with a uniaxial support device. It can be seen that the assembled implant shown in  FIG.  18 A  in some embodiments permits rotational movement about two or more axes. In contrast, the device of  FIG.  18 D  shows a single axis of rotation in the medial-lateral direction. 
         FIG.  19 X  show various views of an anchor according to another embodiment of the present invention;  FIG.  19 A  is an exploded view of the anchor from a top, side, perspective orientation;  FIG.  19 B  is a partly assembled view of the apparatus of  FIG.  19 A ;  FIG.  19 C  is a side elevational view of the apparatus of  FIG.  19 B ; and  FIG.  19 D  shows the apparatus of  FIG.  19 C  fully locked into place.  FIG.  19 A  shows that the tulip head can be reduced onto the screw head and have a profile from the top surface of the implant to the bone surface of under seventeen millimeters for those assemblies that are not preassembled, although in some devices that are preassembled such as for upper thoracic use a pre-assembled device has a profile of under fifteen millimeters. In some embodiments, the locking metal junction results in minimization of excess debris, and in some embodiments less range of movement. It is understood that various configurations shown on  FIG.  19    can be configured as an unlocked implant by eliminating the taper lock interface. 
         FIG.  20 X  show various views of an anchor according to another embodiment of the present invention;  FIG.  20 A  shows an exploded view of the anchor from a top, side perspective orientation;  FIG.  20 B  shows the anchor of  FIG.  20 A  partly assembled;  FIG.  20 C  shows the anchor of  FIG.  20 A  fully assembled in a side perspective view;  FIG.  20 D  is a side elevational cross sectional representation of the apparatus of  FIG.  20 C , and  FIG.  20 E  is a close up view of a portion of  FIG.  20 D . The embodiments of  FIG.  20    are preferably implanted by first inserting the screw shank into the bone, then placing the tulip attachment device onto the rod, and then reducing the tulip device and rod onto the screw head. In some embodiments the assembled profile from top of the implant to the bone surface is under seventeen millimeters, and in those embodiments that are preassembled such as for upper thoracic use, the profile is less than fifteen millimeters. Various of these devices include a “pop on” feature for coupling the tulip head the attachment device. The embodiment shown in  FIG.  20    includes an integral bushing with a contoured exterior, used on a modular tulip with pop-in junctions and polymer lined junctions. It is understood that yet various other embodiments pertain to bushing designs that are oblong, modular oblong, and spherical, as a non-limiting list of options. 
         FIG.  21 X  show anchors according to various embodiments of the present invention;  FIG.  21 A  (top view) shows a cross sectional view of a portion of an assembled anchor according to another embodiment of the present invention; and  FIG.  21 B  (lower) shows the external view of the top view. 
         FIG.  22 X  show various views of an anchor according to another embodiment of the present invention;  FIG.  22 A  shows an exploded view of a portion of the anchor in a side, cross sectional representation;  FIG.  22 B  illustrates the partial assembly of the components of  FIG.  22 A ;  FIG.  22 C  shows the seated assembly of the apparatus of  FIG.  22 B ;  FIG.  22 D  shows a top, side, perspective external view of a portion of the anchor, and also a cross sectional, side elevational view of the bushing and bushing container similar to that of  FIG.  12 D ; and  FIG.  22 E  shows an enlarged cross sectional view of a portion of the apparatus of  FIG.  22 C . As best seen in  FIGS.  22 A and  22 B , this implanted device is a thread-in assembly. 
         FIG.  23 X  show views of anchors according to various embodiments of the present invention; FIG.  24 A 1  shows an exploded view of an anchor incorporating a tapered, locking, bushing container; FIG.  24 A 2  shows a side elevational, perspective view of an assembled anchor of FIG.  24 A 1 ;  FIG.  24 B  shows a side elevational, perspective view of an assembled anchor according to another embodiment of the present invention, and using a set screw concentric with the axis of the bone anchor. 
         FIG.  24    shows a side elevational, perspective view of an assembled anchor according to another embodiment of the present invention, and using a set screw that is offset from the axis of the bone anchor.  FIGS.  23  and  24    shows various means for locking a separable bushing onto a device, including by use of taper locks ( FIG.  23 A ), concentric set screws ( FIG.  234 B ), and non-concentric set screws ( FIG.  24   ). 
         FIGS.  25 X and  26 X  show anchors according to various embodiments of the present invention;  FIG.  25 A  shows one anchor assembled in a side elevational view (A 1 ), a cross sectional view partly disassembled (A 2 ) and a cross sectional exploded view (A 3 );  FIG.  26 B  shows a different anchor in side-by-side side elevational views, external and assembled (B 1 ) and cross sectional (B 2 );  FIG.  26 C  shows an exploded side elevational view of a portion of the assembly; and  FIG.  26 D  shows a cross sectional, exploded, partly assembled view of the anchor. In various embodiments the set screw can be external, such as shown in  FIG.  25 A , or can include a C-clip as shown in  FIG.  26 D . 
         FIGS.  27  and  28    show an anchor assembly according to another embodiment of the present invention;  FIG.  27 A  shows a top, side perspective view of the anchor attached to a spine;  FIG.  28 B  shows an exploded, side perspective view of the apparatus of  FIG.  27 A ;  FIG.  28 C  is a cross sectional view of the assembled anchor of  FIG.  27 A ; and  FIG.  28 D  is a side, top, perspective exploded representation of the apparatus of  FIG.  27 A . Various embodiments include a lower bushing (fabricated from or coated with a polymer, metal, or ceramic) that is built into or inserted into a BandLoc-type of tool head, with an external cap that captures a top bushing element, and compresses the band upon assembly. 
         FIG.  29 X  show various views of an anchor assembly according to another embodiment of the present invention;  FIG.  29 A  shows a top, side perspective representation of the assembled anchor;  FIG.  29 E  shows a top plan view of the apparatus of  FIG.  29 A ; and  FIG.  29 C  is an orthogonal, side elevational view of the apparatus of  FIG.  29 B . Various embodiments, one of which is depicted in  FIG.  29    include cross linked polymer bushings with spherical features, although yet further embodiment contemplate bushing with hard surfaces, such as comprising metal or ceramics. The attachment or supporting device can include spikes to prevent rotation after implantation. The angle and height of the rod aperture can be adjusted by rotation of the bushing container  56 . 
         FIGS.  30  and  31    show an anchor according to another embodiment of the present invention;  FIG.  30    is a side, top, perspective view of the assembled anchor; and  FIG.  31    is a top, side, exploded view of a portion of the apparatus of  FIG.  30   . In some embodiments, the flexible band can be aligned with the axis of the rod. Still further, yet other embodiments contemplate that a polymer bushing within a metal sleeve is used to transmit a compressive load onto the band. Some embodiments include that the banded anchor allows the rod to slide without the rod sliding against the band. Still further embodiments include a band and anchor that contains a polymer bushing or any other low friction interface (as one example, polished CoCr or biologically acceptable ceramics). In some embodiments the surgeons can wrap wires/tapes/bands around the bone and rod to create a sliding construct. Some of these embodiments us a dedicated sliding interface for the rod. 
         FIG.  32 X  represent additional views of the apparatus of  FIG.  19   ;  FIG.  32 E  is a side, bottom perspective, exploded representation of a portion of the apparatus of  FIG.  19   ;  FIG.  32 F  is a bottom plan view of the assembled apparatus of  FIG.  32 E ;  FIG.  32 G  is a front, bottom perspective, exploded view of the apparatus of  FIG.  32 E . 
         FIG.  33 X  show additional views of the apparatus of  FIG.  20   , and including alternative bushing at the interface of the bone attachment device and the head;  FIG.  33 E  is a side elevational, cross sectional representation of the apparatus of  FIG.  20   , with an alternative second bushing;  FIG.  33 F  is a side elevational, cross sectional representation of the apparatus of the  FIG.  33 E , and orthogonal to  FIG.  33 E .  FIG.  33 G  shows an enlargement of the apparatus of  FIG.  33 F  after the head  82   c  of the attachment device has been popped-in to bushing  74   a , with the assembled bushing being pushed into pocket  28   d.    
         FIG.  34 X  present various views of an anchor according to another embodiment of the present invention;  FIG.  34 A  is a side, top, elevational exploded view of the anchor;  FIG.  34 B  is an assembled view of the apparatus of  FIG.  34 A ; FIGS.  34 C 1  and  34 C 2  show end and side elevational views, respectively, of the apparatus of  FIG.  34 B ; and  FIG.  34 D  is a side elevational, cross sectional representation of the apparatus of  FIG.  34 A . Some embodiments pertain to an implant using a split bushing in an open configuration. As shown in  FIG.  34    this embodiment can utilize small polymer half-rings that can be sufficiently constrained and supported within a metal head. Still further embodiments contemplate the use of hard, rod-bearing surfaces comprising metal or ceramic. In some embodiments the profile height of the implanted device is about fifteen millimeters. 
         FIG.  35    show various views of an anchor according to another embodiment of the present invention along with instrumentation for removal of the anchor;  FIG.  35 A  is a side elevational, top perspective, cross sectional view of the assembled anchor;  FIG.  35 B  is an external view of the anchor of  FIG.  35 A  and a first instrumentation device;  FIG.  35 C  is a cross sectional representation of the apparatus of  FIG.  35 B ; and  FIG.  35 D  is a cross sectional representation of the apparatus of  FIG.  35 C  and including a second instrument. Various embodiments shown herein pertain to implantable devices that include options for removal, such as by includes “wings” in the pop-in retaining rings. These rings can be grasped by an instrument that will expand the ring for removal. As shown in  FIG.  35 A , wings are added to the pop ring, and cut outs are added to the tulip so as to minimize reaching underneath the tulip. As shown in  FIG.  35 B  the inner sleeve includes flex tabs. As shown in  FIG.  35 C , there are teeth on the flex tabs that engage the wings on the pop ring. As shown in  FIG.  35 D , the instruments outer sleeve is placed over the inner sleeve so as to lock the teeth, and the instrument can be pulled up to release the pop ring, and pull the tulip from the screw shank. 
         FIG.  36    show various views of an anchor according to another embodiment of the present invention;  FIG.  36 A  is a top, side, perspective view of the assembled anchor;  FIG.  36 B  is a partial exploded view of the apparatus of  FIG.  36 A ;  FIG.  36 C  is a top, front perspective view of the apparatus of  FIG.  36 A ;  FIG.  36 D  is a cross sectional view of the apparatus of  FIG.  36 A ; and  FIG.  36 E  is an enlargement of a cross sectional view of an alternative construction for the anchor. Various embodiments shown herein include the use of a “non-rounded surface” for a polyaxial junction construction, including a protrusion on the bushing that assists in clocking the C-clip. The polymer bushing can be reduced onto the tulip head, and then secured with the C-clip for an overall profile relative to the bone surface of about sixteen millimeters. 
         FIG.  37    show various views of an anchor according to another embodiment of the present invention;  FIG.  37 A  is a top, front, perspective view of the assembled anchor;  FIG.  37 B  is a top planar view of the apparatus of  FIG.  37 A ;  FIG.  37 C  is a side, front, top perspective partially exploded view of the apparatus of  FIG.  37 A ; and  FIG.  37 D  is a side elevational cross sectional representation of the apparatus of  FIG.  37 A . Still further embodiments shown herein pertain to a closed anchor, having a slide-loading, self-retaining polymer bushing that is retained by live-hinged tabs. In some embodiments the implanted device has a profile of less than sixteen millimeters. 
         FIGS.  38 A and  38 B  present CAD-rendered perspective views of yet another embodiment, showing (A) implanted and (B) not implanted depictions, respectively. 
     
    
    
     ELEMENT NUMBERING 
     The following is a list of element numbers used with all of the embodiments, and at least one noun used to describe that element. It is understood that none of the embodiments disclosed herein are limited to these nouns, and these element numbers can further include other words that would be understood by a person of ordinary skill reading and reviewing this disclosure in its entirety. 
     
       
         
           
               
               
             
               
                   
               
             
            
               
                  1 
                 spine model 
               
               
                  2 
                 vertebra 
               
               
                 a 
                 spinous process 
               
               
                  4 
                 rod; rigid or flexible; also tether 
               
               
                 a 
                 circular 
               
               
                 b 
                 non-circular 
               
               
                 b1 
                 height 
               
               
                 b2 
                 width 
               
               
                 c 
                 axis 
               
               
                  6 
                 restraining anchor; fixating 
               
               
                 10 
                 guiding anchor 
               
               
                 20 
                 head 
               
               
                 a 
                 1st end, device placement 
               
               
                 b 
                 2nd end, bushing placement 
               
               
                 22a 
                 threads for set screw 
               
               
                 b 
                 groove, 
               
               
                 c 
                 threaded post 
               
               
                 d 
                 unthreaded aperture 
               
               
                 24 
                 cavity 
               
               
                 b 
                 internal 
               
               
                 c 
                 external (platform) 
               
               
                 d 
                 annular; circumferential 
               
               
                 e 
                 non-cylindrical; oblong; oval 
               
               
                 26 
                 bushing or bushing container retention feature 
               
               
                 a 
                 groove, abutment; recess 
               
               
                 b 
                 locking cantilever spring; live hinge 
               
               
                 c 
                 opposing arms of head; tulip 
               
               
                 d 
                 bushing container interface 
               
               
                 e 
                 side opening 
               
               
                 f 
                 top opening 
               
               
                 27a 
                 ring retention groove 
               
               
                 b 
                 insertion slit, aperture 
               
               
                 28 
                 supporting device junction pocket 
               
               
                 a 
                 internal shape 
               
               
                 b 
                 cylindrical, circular 
               
               
                 c 
                 spherical 
               
               
                 d 
                 pop-in, upper pocket 
               
               
                 e 
                 threaded aperture 
               
               
                 f 
                 tapered 
               
               
                 g 
                 cutouts for retainer access 
               
               
                 h 
                 guiding features for sliding member 
               
               
                 i 
                 notches or ledges for sliding member 
               
               
                 j 
                 slots for sliding member 
               
               
                 k 
                 distal underneath extension 
               
               
                 30 
                 slidable member 
               
               
                 a 
                 projection 
               
               
                 b 
                 one-way latch 
               
               
                 c 
                 cantilever arm 
               
               
                 d 
                 device support latch 
               
               
                 32 
                 head to support device interface member 
               
               
                 a 
                 retention; pivotal 
               
               
                 b 
                 bearing support 
               
               
                 c 
                 retention; lockable 
               
               
                 d 
                 passage for locking wire 
               
               
                 e 
                 wings 
               
               
                 d 
                 distal aperture 
               
               
                 34 
                 1 st  bushing interface 
               
               
                 a 
                 cylindrical 
               
               
                 b 
                 spherical 
               
               
                 c 
                 non-cyl oval oblong 
               
               
                 d 
                 groove or apertures 
               
               
                 e 
                 lip or ledge 
               
               
                 f 
                 lateral opposing slots or grooves (external) 
               
               
                 g 
                 internal groove or slot 
               
               
                 k 
                 tapered; conical 
               
               
                 35 
                 insertion direction 
               
               
                 a 
                 rod relative to head 
               
               
                 b 
                 bushing relative to head 
               
               
                 c 
                 head relative to device 
               
               
                 36 
                 bushing container retention feature 
               
               
                 38 
                 bushing retainer 
               
               
                 39 
                 2 nd  bushing interface 
               
               
                 42 
                 set screw; bushing retainer 
               
               
                 a 
                 set screw external threads 
               
               
                 b 
                 set screw internal threads 
               
               
                 c 
                 c-clip 
               
               
                 d 
                 gap; slot 
               
               
                 d 
                 set nut 
               
               
                 43 
                 slot 
               
               
                 44 
                 flexible connector 
               
               
                 a 
                 rod loop 
               
               
                 b 
                 vertebra loop 
               
               
                 c 
                 connector retention device 
               
               
                 45 
                 threaded cap, compress flex conn. 
               
               
                 50 
                 bushing fabricated from or including a surface comprising a 
               
               
                   
                 polymer, metal, or ceramic 
               
               
                 a 
                 separable matl. body 
               
               
                 b 
                 matl. formed, molded or coated 
               
               
                 51 
                 split bushing; bushing segment 
               
               
                 b 
                 button 
               
               
                 p 
                 proximal 
               
               
                 d 
                 distal 
               
               
                 52 
                 rod pathway 
               
               
                 a 
                 closed channel 
               
               
                 b 
                 opened channel 
               
               
                 c 
                 groove 
               
               
                 d 
                 intermediate point of smallest width of height 
               
               
                 e 
                 entrance or exit to pathway 
               
               
                 53 
                 bushing extensions outside of cavity 
               
               
                 54 
                 bushing insertion direction into head 
               
               
                 a 
                 top 
               
               
                 b 
                 side 
               
               
                 55 
                 tab 
               
               
                 56 
                 bushing container; bushing support; rod-bearing surface of head 
               
               
                 a 
                 head retention feature; projection 
               
               
                 b 
                 opened support arms or saddle 
               
               
                 c 
                 tapered locking arm 
               
               
                 d 
                 extension member (overhanging) 
               
               
                 e 
                 ring; sleeve 
               
               
                 f 
                 interface with supporting device 
               
               
                 g 
                 central passage 
               
               
                 h 
                 cavity extensions 
               
               
                 i 
                 outrigger aperture 
               
               
                 j 
                 thickened or strengthened portion of bushing 
               
               
                 57 
                 bushing container interface with set screw 
               
               
                 58 
                 bushing interface with bushing container; pocket; bushing 
               
               
                   
                 external shape 
               
               
                 a 
                 cylindrical 
               
               
                 b 
                 spherical 
               
               
                 c 
                 non-cyl oval oblong 
               
               
                 d 
                 center 
               
               
                 e 
                 retention feature, ledge, pins 
               
               
                 f 
                 ring inner surface 
               
               
                 g 
                 bushing container to head interface 
               
               
                 59 
                 bushing container to supporting device interface 
               
               
                 a 
                 pocket 
               
               
                 b 
                 fissure 
               
               
                 c 
                 retaining ring 
               
               
                 d 
                 aperture 
               
               
                 60 
                 rod to bushing interface; internal shape 
               
               
                 a 
                 cylindrical 
               
               
                 b 
                 semi-spherical; curved 
               
               
                 c 
                 non-cyl; oval; oblong 
               
               
                 c1 
                 height 
               
               
                 c2 
                 width 
               
               
                 d 
                 center 
               
               
                 62 
                 int. - ext. relationship 
               
               
                 a 
                 centered 
               
               
                 b 
                 offset 
               
               
                 67 
                 set screw interface with bushing 
               
               
                 70 
                 support arm 
               
               
                 a 
                 first ring or enclosure 
               
               
                 b 
                 second ring 
               
               
                 c 
                 first ring axis 
               
               
                 d 
                 second ring axis 
               
               
                 e 
                 enlarged end 
               
               
                 f 
                 arm axis 
               
               
                 g 
                 rigid arm 
               
               
                 74 
                 2nd bushing, 
               
               
                 a 
                 device to head 
               
               
                 b 
                 device to lock ring 
               
               
                 c 
                 support arm to head 
               
               
                 d 
                 split; fissure 
               
               
                 e 
                 socket for device junction 
               
               
                 80 
                 supporting device 
               
               
                 82 
                 device junction 
               
               
                 a 
                 external shape 
               
               
                 b 
                 circular, uniaxial 
               
               
                 c 
                 spherical, polyaxial 
               
               
                 d 
                 pop-in 
               
               
                 e 
                 fixed junction w/head 
               
               
                 f 
                 necked-down region for sliding restraint 
               
               
                 84 
                 bone screw 
               
               
                 a 
                 tip 
               
               
                 b 
                 threaded section 
               
               
                 c 
                 cannula 
               
               
                 86 
                 spikes, projections 
               
               
                 90 
                 instrument 
               
               
                 a 
                 inner sleeve 
               
               
                 b 
                 outer sleeve 
               
               
                 c 
                 teeth; projection 
               
               
                 d 
                 slits; flexible portion 
               
               
                   
               
            
           
         
       
     
     DETAILED DESCRIPTION OF ONE OR MORE EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. At least one embodiment of the present invention will be described and shown, and this application may show and/or describe other embodiments of the present invention, and further permits the reasonable and logical inference of still other embodiments as would be understood by persons of ordinary skill in the art. 
     It is understood that any reference to “the invention” is a reference to an embodiment of a family of inventions, with no single embodiment including an apparatus, process, or composition that should be included in all embodiments, unless otherwise stated. Further, although there may be discussion with regards to “advantages” provided by some embodiments of the present invention, it is understood that yet other embodiments may not include those same advantages, or may include yet different advantages. Any advantages described herein are not to be construed as limiting to any of the claims. The usage of words indicating preference, such as “various embodiments” or “preferably,” refers to features and aspects that are present in at least one embodiment, but which are optional for some embodiments, it therefore being understood that use of the word “preferably” implies the term “optional.” 
     The Shilla concept involves placing traditional pedicle screws at the apex of the spinal curve and fusing that short portion of the spine. Guiding (sliding) anchors (pedicle screws with bushings or coatings that permit sliding of a rod) are placed at the top and bottom of the construct. The sliding anchors force the spine to grow along the “rails” established by the rods. The various designs shown and described herein include low-friction bushings, low-friction coatings, unique geometry, the use of screw, bands, and spikes to secure the tulip head to the vertebra, and modular component design. 
     In various embodiments shown herein, it is understood that some, but not all, of the following features will be shown in certain particular embodiments. However, it is understood that the present invention contemplates combinations that comprise any collection of the following features and their equivalents. These features and their equivalents are shown and described with respect to any of the figures shown herein. 
     With regards to the bushing assembly, this bushing can be attached onto a supporting device  80  with any of the following loading configurations: top load; tip load; two piece; slide load; integral; and/or multi-piece assemblies for integral bushings, as examples. Still further examples contemplated herein include rod-bearing surfaces comprising polymeric, metallic, or ceramic materials, and also such surfaces that are fabricated directly onto the cavity of head  20  and not necessarily part of a separable, installable bushing component. 
     With regards to the internal or external features of the bushing  50 , the bushing can be contoured; oblong; modular oblong with options shown herein; spherical; and/or metal lined, as examples. 
     With regards to the design of the anchor head  20 , various embodiments include: a traditional tulip; a modular tulip; a modular outrigger for traditional tulips (both medial/lateral and inline); modular outriggers for custom screws; and/or banded/pedicle hybrid options, as examples. 
     With regards to the support of the bushing  50  onto the supporting device  80 , various embodiments include: a wrap-around saddle; side-locked junctions; pop-in junctions; polymer lined junctions; junctions lined with hard metallic coatings or ceramic coatings; threaded-through assemblies; and/or tapered junctions (esp. those that are not spherical), as examples. 
     With regards to the manner of retaining the bushing, various embodiments shown herein include tapered locks; concentric set screws; non-concentric set screws; snap teeth and live hinges; external set screws; and/or C-clips, as examples. 
       FIG.  5    presents a plurality of embodiments of guiding anchors  10 , the various heads  20  and bushings  50  are presented with regards to the direction from which the bushing  50  is inserted into the head  20 . In  FIGS. A 1    to A 6 , the direction of insertion of the bushing is from a topmost end  20   b  of the head in a direction toward the device end  20   a  (i.e., the end of the head to which the supporting device  80  is coupled).  FIGS. B 1   , B 2 , and B 3  shows various embodiments of heads  20  in which the bushing  50  is inserted in a lateral direction relative to the end of the head that couples to the supporting device  80 .  FIGS. C 1    and C 2  shows a pair of embodiments in which the bushing is inserted along an insertion path that is neither parallel nor perpendicular to the orientation of the head  20 .  FIGS. D 1    to D 4  present various embodiments in which the bushing is molded integrally with the head, or molded integrally into the container, with the container being slid into the head. 
       FIG.  6    shows a guiding anchor  10  that includes a bushing assembly  50  that includes a rod pathway  52   b  that is an open channel. A bushing segment  51  is coupled to the bottom of a set screw  42 , creating surfaces surrounding the rod that are fabricated from a polymer material, although ceramic and metallic materials are also contemplated for the bushing segment. 
       FIG.  6 A  shows an assembled anchor  10  supporting a circular spinal rod  4 .  FIGS.  6 B,  6 C, and  6 D  show partly assembled, exploded, and cross sectional views of the anchor  10  of  FIG.  6 A . 
     Referring to  FIG.  6 C , it can be seen that anchor  10  in one embodiment includes a supporting device  80  preferably comprising a threaded bone screw having a rounded external shape that is adapted and configured to coact with a retention device  32   a , such that the assembly of junction  82   a , retention member  32   a , and the device junction pocket  28   b  results in an attachment of head  20  to supporting device  80  that permits relative pivoting. In some embodiments, a portion of a wire (not shown) is inserted into the annular channel that surrounds pocket  28   a  and device  32   a , preventing removal of supporting device  80 . 
     Referring to  FIG.  6 C , it can be seen that head  20  includes a pair of proximally extending opposed, threaded arms  26   c  that define between the arms a cavity  24 . Referring to  FIG.  6 C , it can be seen that cavity  24  includes one or more bushing retainer features  26   a  that assist in retaining bushing  50  within cavity  24 . In the embodiment shown in  FIG.  6   , it can be seen that the retention feature  26   a  includes a pocket that is wider than the distance between opposing faces of arms  26   c . In some embodiments, bushing  50  has a C-shape, and is inserted into cavity  24  sideways. Once the bushing is placed at the bottom of cavity  24 , the bushing is then rotated so that the open portion of the C-shape faces in a proximal direction and forms the rod pathway  52   b.    
     Referring to  FIGS.  6 B and  6 D , it can be seen that anchor  10  includes an externally threaded set screw  42   a , the bottom of which includes a bushing segment  51 . Referring to  FIG.  6 D , it can be seen that once set screw  42   a  is tightened into arms  26   c , that bushing segment  51  places an upper limit on the rod pathway  52   b . In some embodiments, tightening of set screw  42   a  results in compression of this underneath bushing against the top of rod  4 . In yet other embodiments, the set screw bottoms out mechanically, such that there is little or no contact between bushing  51  and the top of rod  4 . 
       FIG.  7    shows various aspects of a guiding anchor  10  according to another embodiment of the present invention.  FIG.  7    show various views of an anchor  10  in which the head  20  incorporates a bushing maintained in location by one or more bushing container rings  56   e.    
       FIGS.  7 A,  7 B and  7 C  show the installation of bushing container rings  56   e  within head  20 .  FIG.  7 A  shows such a container ring that includes a central aperture that defines within it an opened channel  52   b  for clearance passage of a rod (not shown). In the embodiment shown, ring  56   e  is a complete ring-shape that includes a circular internal aperture  52   b . However, it is understood that this central aperture can be of other shapes consistent with the primary placement of the rod being dependent upon the internal diameter of bushing  50 , with the inner surfaces of rings  56   e  providing harder, more controlled limits on the internal movement of the rod within head  20 . Referring to  FIG.  7 F , bushing container  56   f  in one embodiment includes an internal shape  58   f  that smoothly converges from a larger inner diameter to a smaller inner diameter in a direction from outside of head  20  toward the central bushing  50 . The inner surface of bushing  50  is preferably circular or rounded (in cross sectional shape), and defines the closest fit to the rod within the pathway  52   b.    
     Referring again to  FIG.  7 A , it can be seen that ring  56   e  includes one or more head retention features that coact with one or more ring retention features  27   a  to maintain ring  56   e  fixed in location. However, various other embodiments of the present invention include rings  56   e  that are placed within head  20 , but are retained loosely and able to slightly move within the head after assembly. 
       FIG.  7 C  shows a cross section of a head  20  in which a first ring  56   e  has been inserted through a preferably central aperture  27   b , and then moved sideways into the retention groove  27   a . In some embodiments, there is a single retainer ring within a head  20 . However, in the embodiment shown and as can be seen in  FIG.  7 D , there are a pair of rings  56   e  that have been inserted through slot  27   b , and then laterally shifted into place on opposite sides of a central volume.  FIG.  7 F  shows a bushing  50  that has been inserted through aperture  27   b  into the volume between rings  56   e.    
       FIG.  8    presents a cutaway of a guiding anchor  10  in which a cylindrical rod  4   a  is received within a bushing  50  that has an internal shape  60   b  to the rod interface that is semi-spherical, and permitting angular movement of the rod of about +/−10 degrees relative to the centerline of the bushing pathway. In the embodiment shown, anchor  10  includes a head  20  that is in fixed relationship to device  80  by a fixed junction  82   e . It is understood that head  20  shown in  FIG.  8    could also be attached to a supporting device having a junction that permits uniaxial or polyaxial movement, although in the embodiment as shown, the additional rod pivotal movement that would be permitted by uniaxial or polyaxial attachments are instead provided by the internal shape  60   b  of bushing  50 . In this manner, the overall height of anchor  20  from the bone contacting surface can be reduced by the fixed nature of junction  82   a.    
     As shown, bushing  50  in one embodiment includes a generally cylindrical outer surface  58   a  that is received within the cavity  24  of head  20 . Such a bushing can be inserted into head  20  in a direction generally along the axis of the rod, or in some embodiments can be inserted in a proximal to distal direction through a threaded aperture of head  20  that is later filled with a set screw  42   a.    
       FIG.  8    shows that the internal rounded surface  60   b  (shown as semi-spherical) permits rod  4  to be generally located along the centerline of supporting device  80  due to the positioning of the narrow point of the bushing aperture at that centerline. In such embodiments and as shown, this internal close fit between the rod and the center of bushing  50  allows for pivoting motion, with one end of the rod contacting the upper internal surfaces of bushing  50 , and the other end of the rod contacting the lower internal surface of bushing  50 . 
       FIG.  9    present various views of a guiding anchor  10  that includes a bushing having a non-cylindrical internal shape for the rod interface. It can be seen on the right side E of  FIG.  9    that the oblong or non-spherical shape  58   c ,  60   c  for the busing permits lateral and angular movement of a rod, while avoiding the encroachment into tissue of a uniaxial or polyaxial device attachment. 
     FIGS.  9 A 1  and A 2  show a head  20  of an anchor  10  that is adapted and configured to receive within an elongated or oblong cavity  24  a bushing  50  having at least one retention feature  58   e  (and preferably two) located on the topmost (proximal) surface. Bushing  50  can be inserted through a lateral side of head  20 , and as shown can be loaded in the same direction as the axis of the rod (not shown). In some embodiments, bushing  50  includes an interface  67  that is adapted and configured to receive therein the bottom face of a set screw  42  or similar device. Preferably, after insertion of bushing  50  into head  20  the pair of opposing ledges  58   e  extend above the central set screw interface  67 , such that bushing  50  is trapped within cavity  24  by set screw  42 . In the embodiment shown, supporting device  80  is coupled to head  20  by a fixed junction  82   e . Although the fixed junction (of some embodiments, but not others) does not permit relative motion of head  20  relative to support device  80 , the oblong or elongated rod interface  60   c  is adapted and configured to provide lateral motion of the rod (for example pure lateral motion, laterally pivotal motion, or a combination thereof). 
     Referring to  FIGS.  9 B and  9 C , it can be seen that in some embodiments the anchor  10  shown in  FIG.  9 A  (and reproduced in  FIG.  9 C ) provides a lower overall height of the top of anchor  10  relative to the bone surface (i.e., about sixteen millimeters for the polyaxial screw of  FIG.  9 B ; and about thirteen millimeters for the fixed screw of  FIG.  9 C ). 
     Yet another trade-off between polyaxial and fixed support devices is shown in  FIGS.  9 D and  9 E .  FIG.  9 D  shows the pivotal head  20  of  FIG.  9 B , which can be in different embodiments uniaxial or polyaxial). It can be seen that the side to side pivotal motion results in a distal corner of head  20  moving downward toward the surrounding tissue. In contrast, the fixed nature of head  20  as shown in  FIGS.  9 E and  9 C  provides a fixed interface that minimizes tissue encroachment. 
     In further comparison of  FIGS.  9 D and  9 E , it can be seen that  FIG.  9 D  permits, in some embodiments, a pivotal motion laterally pivotal of about sixteen degrees, with one of the topmost corners of head  20  pivoting upward (in a manner analogous to the downward pivoting of the lower corner). In yet another comparison, the lateral (side to side) envelope of the anchor of  FIG.  9 D  is about twenty millimeters, whereas the fixed lateral envelope of the anchor of  FIG.  9 E  is about fifteen millimeters. 
       FIG.  10    show a plurality of guiding anchors  10  that include a bushing with a non-circular external shape that is preferably molded into the head  20 .  FIG.  10 A  anchor  10  includes a non-cylindrical rod internal interface  60   c  that permits lateral motion and angular motion of a rod (as well as the axial, guided motion). The other three anchors B, C, and D each include smaller rod interfaces (shown as cylindrical interfaces, by way of example only), with some of the internal rod interfaces being offset from the external head interface, and with two anchors in which the internal and external bushing shapes are generally centered. In some embodiments of the present invention, the anchors  10  of  FIG.  10    illustrate a kit of anchors. 
     In each of the four embodiments shown, the head  20  and support device  80  are the same, each incorporating a device junction  82   e  that is fixed. However, the kit is further preferably provided with a plurality of different bushings  50 . As can be seen in  FIG.  10 A , one bushing  50  incorporates a non-cylindrical rod interface  60   c , such an oval or oblong interface, which permits lateral movement of a rod (lateral translation, lateral pivoting, or a combination of both). The bushing  50  of the anchor of  FIG.  10 B  incorporates a generally cylindrical rod interface  60   a  that is generally centered within the oblong cavity  24   e . In contrast, the bushings  50  of the anchors of  FIGS.  10 C and  10 D  include a generally cylindrical rod interface  60   a  that is shown with an offset  62   b  relative to the centerline of the supporting device. In some embodiments, the bushings of  FIGS.  10 C and  10 D  are identical, and simply inserted in a different direction to change the offset. 
       FIG.  10 E  depicts the embodiment of  FIG.  10 A  shown supporting an oblong rod  4   b  having a width  4   b   2 . Rod  4   b  is located within a non-circular bushing interface  60   c  having a height  60   c   1  that is less than the rod width  4   b   2 . Therefore, bushing  60   c  within head  20  will limit any rotation of the rod within the rod pathway  2   b . This limit is reached when the longest cross sectional distance of the rod touches the inner surface of the bushing. 
       FIG.  11    shows a guiding anchor  10  that includes a bushing  50  having a spherical external shape  58   b  that is received within a spherical bushing interface  34   b  of the head  20 . The right side of  FIG.  11    compares head  20  in view D on top that is fixed to the device  80 , and a head  20  at the bottom in view E that interfaces with the device by way of a spherical junction  82   c . In the top device, the bushing is spherical relative to the head, whereas in the bottom device the bushing is fixed relative to head  20 . It can be seen that the rotation point for the rod is different for the two different devices. 
       FIG.  11    show various views of a first anchor  10 , and a view of an alternative anchor in  FIG.  11 E  for comparison.  FIGS.  11 A and  11 B  show partially transparent and exploded views, respectively, of anchor  10 . Anchor  10  includes a bushing  50  having a spherical head interface surface, and which is received within a spherically shaped head pocket  34   b . In the anchor of  FIG.  11 C  a rod can be pivoted about plus or minus twelve degrees vertically (as shown in  FIG.  11 C ) and further pivoted laterally (i.e., in and out of the plane of the figure) plus or minus twelve degrees. 
       FIG.  11 D  shows the anchor of  FIG.  11 A  compared to an anchor  10  of  FIG.  11 E  that includes a cylindrical rod interface, but which includes a polyaxial junction  82   c  between head  20  and support device  80 . It can be seen that the point of rotation of the rod in  FIG.  11 D  is generally the centerline of the bushing  50 . As a rod is urged to pivot, the sliding interface will occur between bushing  50  and pocket  34   b . In contrast, in the anchor of  FIG.  11 E  the bushing  50  is retained in fixed position by retention features  58   e  (in a manner similar to that for the anchor discussed in  FIG.  9 A ), such that any pivotal urging of a rod located within bushing  50  of  FIG.  11 E  would result in pivotal motion of the head assembly  20  relative to the center of the supporting device junction  82   c.    
       FIG.  12    shows a guiding anchor  10  according to various embodiments of the present invention.  FIGS.  12 D , E, F, and G shows a bushing  60  located within a container having a pair of protruding head extensions  56   a . Referring to the bottom of the rightmost column, it can be seen that each of these features  56   a  interface with a corresponding cantilevered locking arm  26   b  of head  20 . Referring now to  FIGS.  12 A , B, and C, it can be seen that in another embodiment one or more protruding features  56   a  can be received in corresponding grooves  26   a  of head  20 , the insertion being accomplished by compressing together bushing  50  and head  20  such that the opposite arms  26   c  spread apart and then snap together, capturing the head retention features  56   a . The cantilevered locking arm  26   b  of head  20  of  FIG.  12 E  operates in a manner similar to that of the cantilevered locking arm shown in  FIGS.  21 B . and  27 . 
       FIGS.  12 A,  12 B, and  12 C  depict various views of an anchor  10  according to another embodiment of the present invention. Comparing  FIGS.  12 A and  12 D , it can be seen that a similar bushing container  56  and bushing  50  are used in each of the two different anchors. The bushing container  56  includes one or more retention features that are generally complementary in shape to retention features on head  20 . Referring to  FIG.  12 A , head  20  includes a groove  26   a  that receives within it the retention features  56   a , as shown in  FIG.  12 C . Whereas the anchor of  FIG.  12 D  incorporates living hinges  26   b  into which the retaining features  56   a  are snap received, in the anchor of  FIG.  12 C  can be located within groove  56   a  by compression of bushing container  56  into the cavity  24  of head  20 , such that the retention features  56   a  are sufficiently resilient to compress inward, and then expand back outward into the groove  26   a . As a further difference, it is further noted that the head retention features  56   a  of  FIG.  12 D  have a generally small circumferential extent and are adapted and configured to fit into a pocket of cantilever arm  26   b  of similar size. In contrast, the retention features  56   a  best seen in  FIGS.  12 A and  12 B  have a more extensive circumferential extent, and in some embodiments extend generally from one side of the bushing aperture to the other side of the bushing aperture. 
     In still further embodiments, a variation of the bushing container and bushing of  FIG.  12 A  can be coupled to a head  20  with a groove  26   a  by a bayonet-type connection. In such embodiments, the bushing  50  would not have the outward extensions  53  shown in  FIGS.  12 D and  12 A . Instead, the ends of the rod pathway would be generally the same as the apertures of container  56 . In such an embodiment, a modified bushing container  56  could be placed within cavity  24 , and then rotated within the cavity such that the retention ledges  56   a  shown in  FIG.  12 A  enter the grooves  26   a  from the open sides of cavity  24 . 
       FIG.  12 F  shows a cross sectional shape  60   b  for the interface between the rod and the bushing  50 , Preferably, in some embodiments the mid-section of bushing  50  has a smaller internal height and/or width  52   d  than the height and/or width of the open ends  52   e  of the bushing. Because of this shape, the intermediate section of the bushing acts as a loose fulcrum for any pivotal motion of the rod relative to the head. Still further, since the open ends are larger, there is less possibility of contact and abrasion of the rod against the bushing openings  52   e.    
       FIGS.  12 C and  12 D  further show the polyaxial coupling of head  20  to support device  80 . Referring to  FIG.  12 C , it can be seen that head  20  includes a cylindrical pocket that is adapted and configured to receive within it a retention member  32   a . Each of head  20  and member  32   d  include a portion of a passageway which can be aligned together and form an annular pocket  32   d  into which a locking wire (not shown) can be inserted. Retention device  32   a  includes within it a pocket having a shape that is generally complementary to the outer shape of a bearing support  32   b . The supports  32   a  and  32   b  interlock with each other by way of this fitting of complementary shapes. Bearing  32   b  further includes an interior spherical recess that is preferably close fitting to the spherical ball junction  82   c  of support device  80 . Preferably, bearing support  32   b  is either comprised of a material, or is coated with material, suitable for it to be a low friction bushing  74   b  for device junction  82   c.    
       FIG.  13    shows various anchor designs according to various embodiments of the present invention. FIGS.  13 B 1  and B 2  show a guiding anchor  10  that includes a pop-in head  28   d . This embodiment is further discussed with regards to  FIG.  20   .  FIGS.  13    C 1 , C 2 , C 3 , D 1 , D 2 , and D 3  show various embodiments, some of which include bushings  50  that are supported by an arm, with the arm being connected to the head  20 . In  FIGS. C 1   , C 2 , and C 3  it can be seen that the arm  70 G is received vertically downward onto the head  20 , with the outer surface of the arm being locked by a set screw within a laterally arranged cavity  24 . In  FIGS. D 1   , D 2 , and D 3 , it can be seen that the arm  70  includes a second ring  70   b  that is received vertically into a cavity  24 . 
     FIGS.  13 A 1  to A 6  shows embodiments 6 embodiments. Embodiment  12 A 1  is discussed further with regards to  FIG.  11 A . Embodiment  12 A 2  is discussed further with regards to  FIG.  11 E . 
     Embodiment  12 A 3  is similar to the embodiment shown in  FIG.  6   . Embodiment  12 A 4  is similar to the anchor shown in  FIGS.  8  and  18   . Embodiment  12 A 5  is further discussed with regards to  FIG.  12   . Embodiment  12 A 6  is further discussed with regards to  FIG.  24 B . 
     Embodiment of  13 B 1  is discussed further with regards to  FIG.  19   . Embodiment  13132  is discussed further with regards to  FIG.  20   . Embodiment  13 C 2  is discussed further with regards to  FIG.  29   . Embodiment  13 C 3  is discussed further with regards to  FIG.  14   . 
     Referring to FIG.  13 C 1 , there is shown a portion of an anchor according to another embodiment of the present invention. Embodiment  13 C 1  includes a preferably rigid arm  70   g  that supports on one end a bushing  50  within a first ring  70   a . As will be discussed in more detail later, the device of embodiment  13 C 1  permits the rod pathway  52   b  at a lateral distance spaced apart from the attachment of anchor  10  (not shown) to the spine. The cylindrical portion of rod  70   g  is coupled in any manner to a head  20 . In that manner, the surgeon is presented with more options for the relative placements of the rod and anchors. 
     As shown in FIG.  13 C 1 , the support arm includes a rigid portion extending outwardly from the ring  70   a . This extension portion can be cylindrical (as shown), or of a faceted nature, grooved, or otherwise prepared so as to improve the security of the connection between arm  70  and the head of the anchor. In some embodiments, the cylindrical shape (as shown) is fixed to the head by friction originating from compression created by a set screw. As one example in contrast, a faceted version (as one example, with an octagonal shape) can be received between a pair of opposed arms having flat surfaces. In such embodiments, a set screw serves to maintain the arm within the head, but is not needed for purposes of preventing rotation of the arm relative to the head (such prevention being provided by the octagonal shape interfering with the internal surfaces of the opposing arms of the tulip head). Yet other embodiments of the support arm (such as those shown in embodiment  13 C 2  and  FIG.  13 D ) are discussed with regards to  FIGS.  29  and  14   , respectively. 
     FIGS.  13 D 1 , D 2 , and D 3  show an “outrigger” configuration in which a laterally-displaced rod path  52   d  is supported on a head  20  by a bushing  74   c . A first ring  70   a  offset by a relatively short support arm  70   g  serves as a bushing container  56  for a bushing  50  that will support a rod (not shown). The other end of the short support arm  70   g  includes a second ring  70   b  that contains within it a second bushing  74   c . This second bushing  74   c  can be of any type, including low friction, harder organic materials (or coatings), as well as softer, more elastomeric organic materials (such as biocompatible rubbers). 
     Referring to FIG.  13 D 3 , it can be seen that the second ring  70   b  defines an axis (for attachment to head  20   b ) that is nonparallel with the rod axis established by bushing  50  as rod pathway  52   b . As shown, the rod axis and head axis are perpendicular in one embodiment, although other embodiments can be of any relative angular orientation. Also shown in FIG.  13 D 3  is an anchor head  20   b  that is modified to accept around it the second bushing  74   c . In one embodiment, the head is fixedly attached to a support device  80 , although any manner of support is contemplated. 
     Referring to FIG.  13 D 1 , it can be seen that the insertion of head  20   b  within bushing  74   c  establishes an annular (or circumferential) cavity  24   d  in cooperation with the interior of second ring  70   b . Second bushing  74   c  is preassembled into ring  70   b , such that the coupling of arm  70  onto head  20   b  simultaneously establishes the annular cavity  24   d  and also fills the annular cavity with bushing  74   c.    
     Preferably, the proximal end of head  20   b  is internally threaded so as to receive therein a set screw  42   a . In some embodiments, set screw  42   a  includes a head that is wide enough to extend over the top annular face of bushing  74   c . A tightening of set screw  42   a  within head  20   b  places second bushing  74   c  in compression between the underside of the head and an internal surface of head  20   b . In some embodiments, this head does not have sufficient extent to compress against the upper annular surface of ring  70   b , such that the support of arm  70   g  relative to head  20   b  is accomplished only through bushing  74   c . This isolation of the arm  70   g  from head  20   b  can also be accomplished with the proper dimensioning of the set screw, head, and ring. 
       FIG.  14    shows exploded and cutaway views of a guiding anchor  10  that includes a bushing container  56  that includes a pair of bushings on either side of channel  52   a . It can be seen that after the bushing container assembly is placed on the rod, that the assembly and rod can be placed downward onto a device  80 . 
       FIG.  14 A  shows the head  20  and supporting device  80  of an anchor  10 . Preferably, head  20  includes a pair of opposing arms (a tulip) that define between them an internal cavity  24   b . Head  20  preferably includes an external bushing container interface  26   d   1  that in the embodiment shown includes a flat external surface on the outside of each arm  26   c . Referring briefly to  FIG.  14 C , it can be seen that this external flat surface  26   d   1  of head  20  comes into sliding contact with a corresponding internal flat face  58   g   1  of bushing container  56 . These lateral flats  26   d   1  are best seen in sliding and abutting contact with bushing container internal head interfaces  58   g   1  in  FIG.  14 C . Head  20  further includes an internal bushing container interface surface  26   d   2  located around the cavity opening  24   b . These external bushing container interfaces  26   d   2  generally surround the rod pathway  52   a , and after assembly will be located opposite of corresponding internal head interface surfaces  58   g  of bushing container  50  (as best seen in  FIGS.  14 B and  14 D ). Preferably, the upper, inner portions of arms  26   d  include a threaded portion  22   a  for threaded mating with the external threads of a set screw  42   a  (as seen in  FIG.  14 D ). 
     In one embodiment, bushing container  50  preferably includes a pair of bushings  50 , with each one located in an outrigger aperture  56   i . Referring to  FIG.  14 B , it can be seen that the assembled head  50  includes a pair of bushings  50  each located in a corresponding aperture  56   i , in alignment with rod pathway  42   a , and on either sides of a central open volume that is adapted and configured to surround a portion of head  20 . 
       FIGS.  14 D and  14 E  show a portion of the assembled anchor  10 . A sets crew  42   a  is threadably coupled to arms  26   c , the set screw including a circumferential lip that seats against the top surface of bushing container  56 . A rod (not shown) is supported internally in pathway  52   a  by the bushings  50  located on either side of the head  20 . Preferably, the internal cavity  24  is adapted and configured to provide clearance around the supported rod, such that there is little or no contact between head  20  and the rod. 
       FIG.  15    shows a guiding anchor  10  in which the rod is coupled to a device  80  by way of a flexible connector  44  that is looped  44   a  around the rod. The ends of the flexible connector are attached to slots  43  of head  20 . 
     The anchor  10  of  FIG.  15    includes a flexible connector  44  that is looped  44   a  around the rod. Flexible connector  44  is attached at each end to the top surface of a platform  24   c , with the ends of the flexible connector being attached to platform  24   c  by one or more grooves  43 . Preferably, platform  24   c  is coupled to a cannulated support device  80  by way of a fixed junction  82   e.    
     The anchor of  FIG.  15    is adapted and configured to generally retain a rod  4  (of any shape) in a general location, yet at the same time provide limited six degree of freedom movement. Referring to  FIG.  15 A , it can be seen that rod  4  is unrestrained from movement along its axis. The lateral (side to side) movement of rod  4  relative to anchor  10  is generally constrained by the tightness and the flexibility of loop  44 . The vertical (distal) motion of the rod is constrained by abutment against platform  24   c . The vertical (proximal) motion of the rod is limited by the flexibility and wrapping of connector  44 . The relative pivotal motions of rod  4  relative to head  20  are limited by the wrapping and flexibility of connector  44  (for yawing motion), and by wrapping and flexibility of the connector along with the abutment against the top platform surface of head  20  (for pitching motion). Note that rolling motion (i.e., rotation about the axis) is generally unconstrained by connector  44 , although in some embodiments a rolling motion in one direction may tighten the interface of the connector  44  with the external surface of rod  4 , and rolling motion in the opposite direction may slightly loosen the connection. 
       FIG.  16    shows a guiding anchor  10  similar to that of  FIG.  15   , except head  20  includes a groove  34   d  that receives a separable organic, polymer bushing  50   a . A loop  44   a  of flexible connector is attached by way of slots  43  to the head  20 . 
     The anchor  10  of  FIG.  16    includes a groove  34   d  that has a shape complementary to the external shape of the bushing, and as shown as a semi-cylindrical shape that is complementary to the cylindrical shape of bushing  50   a . The bushing is held in place in groove  34   d  by a flexible connector  44   a  that wraps around the outside of the bushing, with one end of the connector being retained in a groove  43  by a retaining clip  44   c . As shown, the connector is wrapped around the outside of the bushing and looped through a slot  43  on the opposite side of head  20 . Note that the preferably close-fitting nature of the loop  44   a  restrains many of the degrees of freedom found in the anchor of  FIG.  15   . For example, any yawing or pivoting motion is restrained by placement of the bushing within groove  34   d , as well as the flexibility of connector  44   a . Likewise, any translational movement of the rod is limited by the preferably tight fit of connector  44 . 
       FIG.  17    shows assembled, exploded, and cutaway views of a guiding anchor  10 . Anchor  10  includes a bushing container  56   b  arranged as a saddle which receives within it a bushing having spherical outer surface  58   b . The opened, support arms  56   b  are received within a corresponding pair of arms  26   c  of head  20 . 
     Referring to  FIGS.  17 B,  17 C, and  17 D , it can be seen that the saddle or bushing container  56   b  includes on its distal end an interface  56   f  with the head of supporting device  80 . In one embodiment, the interface  56   f  includes a pair of short arms that extend downwardly and over a generally spherical device junction  82   c  and extending into the space between the spherical head and the pocket  28   c  of head  20 . 
     Referring to  FIG.  17 C , it can be seen that the bushing container  56   d  is received within the cavity  24  of head  20 . The bottom interface  56   f  is preferably in contact with the spherical head  82   c  of device  80 . The pair of arms  56   b  extend out of cavity  24 , and when set screw  42   a  is tightened, the top surfaces of arms  56   b  are in compressive contact with the underside of the set screw. Therefore, compressive loading from the set screw is transferred through container  56   b  through interface  56  and onto the interface between pocket  28   b  and junction  82   c . This compressive force against this interface of the device  80  and head  20  results in a frictional locking of device  80  relative to head  20 . It can also be seen in  FIGS.  17 C and  17 D  that the spherical junction  82   c  is constrained to remain within a distally located pocket of head  20  by a retention member  32   c  that is adapted and configured to restrain a locked spherical device junction. 
       FIG.  18    depicts guiding anchors  10  showing embodiments having both spherical (polyaxial) device junctions  82   c  and circular (uniaxial) device junctions  82   b . As one example, each of these heads  20  include side loaded separable bushings  50   a , each having one or more retention ledges  58   e  that assist in securing the bushings within the heads, and further including a central interface  67  for a set screw. Also shown are closed heads that include molded bushings  50   b.    
       FIG.  18    illustrates the versatility of the various embodiments shown herein. The anchors of FIGS.  18 A 1  and A 2 ,  18 B, and  18 C each show various different heads  20  that are attached to corresponding devices  80  so as to be polyaxially pivotal. Each of the support devices  80  incorporate a device junction  82   c  that includes a preferably spherical surface. The various device junctions are retained within the corresponding heads  20  by a retention member  32   a  that forms an interface between an underside pocket of head  20  and the junction  82   c , so as to permit polyaxial movement (i.e., pivotal in two orthogonal directions), while at the same time constraining the device to remain attached to the head. 
     In contrast, the anchors of  FIGS.  18 D,  18 E, and  18 F  are adapted and configured to limit pivotal motion to a single axis. The various devices  80  are retained within the corresponding heads  20  by a retention member  32   a . However, the outer surfaces of device junctions  82   b  are preferably flattened on opposing sides, with the other opposing sides being rounded and preferably cylindrical. Therefore, the pivotal motion of the anchors of  FIGS.  18 D,  18 E, and  18 F  are limited to a pivotal motion about a single axis. In some embodiments, the flattened sides of head  82   b  are received within an internal slot of head  20  that is likewise flattened on opposing sides. Since these flattened surfaces of the head and device junction are adjacent to one another, pivotal motion about the axis of device  80  is constrained. In contrast, and as shown in FIG.  18 A 2 , the heads  20  shown in those three figures are preferably rotatable in each of three orthogonal directions. 
     The various anchors shown in  FIG.  18    also help illustrate a sample of bushings contemplated for various anchors. FIGS.  18 A 2  and  18 D each show bushings that are loaded from the side, and preferably along the axis of the rod pathway, although side loading in a direction perpendicular to the cavity is also contemplated. These bushings are preferably restrained by set screws. 
       FIGS.  18 B and  18 E  show heads in which the bushings are loaded from the top and received within the corresponding cavity  24  of the head  20 . Bushings are preferably retained by set screws, although they can be retained in any manner. 
     The anchors shown in  FIGS.  18 C and  18 F  show closed heads  20  in which the bushing  50   b  is preferably molded into place. Although the six anchors of  FIG.  18    depict various types of bushings, it is understood that these anchors are shown by way of example only. It will be understood from a review of other embodiments that many different anchors shown herein can be provided with polyaxial support devices or uniaxial support devices. Further, although not shown in  FIGS.  18   , these various anchors can also include provisions for being locked into a user-selected pivotal angle. 
       FIG.  19    shows exploded and assembled versions of a guiding anchor  10  in which a head  20  can be vertically placed on a device  80 , with a sliding member  30  being used to interlock the head and the device. After sliding member  30  is pushed toward device junction  82   c , one or more one-way spring latches  30   b  prevent backing out of sliding member  30 . Additional views of the sliding locking member  30  and head  20  are provided on  FIG.  32   . 
     Anchor  10  of  FIGS.  19  and  32    preferably includes a head  20  that receives within it a side-mounted polymer bushing  50   a . However, yet other embodiments are not so limited and can include bushings that are molded in place or spray-coated in place, bushings inserted from above, and still further bushing/head configurations shown herein. 
     Head  20  is preferably attached to the spine by a support device  80  having a device junction  82  that includes a region  82   f  having a smaller width than the head  82   c  above it, or the threaded area  84   b  below it. Although the device junction in  FIGS.  19 A and  19 B  is shown as a spherical junction  82   c , it is understood that any type of junction geometry can be used, such that the geometry is wider above the necked-down region  82   f . As shown,  82   f  has a smaller outer diameter than the diameter of junction  82   c , or the immediately adjacent diameter threaded area  84   b.    
     Referring to  FIG.  32 F , this supporting device  80  extends through the bottom aperture that extends into cavity  24 . When the sliding member  30  is full inserted (as shown in  FIG.  32 F ), the latch  30   d  is located within the necked-down region  82   f . Latch  80   d  extends toward the reduced width section  82   f , such that fully inserted latch  30   d  interferes with any attempt to remove head  20  from support device  80 . 
     Referring to  FIGS.  32 E , F, and G, it can be seen that sliding member  30  has a pair of cantilever  30   c  that are slidingly received on opposite sides of head guiding features  28   h . Preferably, latch  30   d  is slidingly received between guiding features  28   h . As the sliding member  30  is inserted into head  20 , each of the ends of the cantilever arm are received within a corresponding slot  28   j , the arms being guided by the slots toward notches  28   i  at the end of slots. Referring to  FIG.  32   f   , it can be seen that as the arms  30   c  move within the slots  28   j  that the angled ends of the arms  30   c  pass over notches  28   i  and are elastically pushed inward by notches  28   i . Once the ends of the cantilever arms are passed the notches, the arms spring back into place, such that they come into a locking arrangement with the notches as best seen in  FIG.  32 F . This locking arrangement permits removal of slide  30 , and locks device  80  onto head  20 . 
       FIG.  20    depicts a guiding anchor  10  according to another embodiment of the present invention. Additional views of the anchor of  FIG.  20    are shown in  FIG.  33   . 
     The anchor of  FIGS.  20 , and  33 E and  33 F  are “pop-in,” closed tulip preassembled heads  20  that can be inserted as a subassembly onto an implanted anchor  80 . In some embodiments, the preassembled, subassembly  20  includes a polymer bushing  50  located within a cavity  24 . Head  20  further includes a distally-located tapered pocket  28   f  that includes within it a polymer retaining ring  74   a . It is noted that various different shapes of polymer ring  74   a  are shown in  FIG.  20    and  FIG.  33   . Preferably, each of them include a slit or fissure  74   d  that permits the retaining ring  74   a  to expand (because the hoop stiffness of the ring is compromised by the fissure) and further permits a reduction in the overall size of the retaining ring (i.e., to the extent of the width of the fissure). Fissure  74   d  is further shown in the enlarged view of  FIG.  33 E . It is noted that the pocket  28   f  includes a sidewall that is partly cylindrical, and partly tapered. It is further noted that immediately above the ring  74   a  is a pocket  59   a  in bushing  50  that provides clearance space for the device junction  82   c.    
       FIGS.  33  and  20    each show a pop-on type of coupling between device  80  and head  20 .  FIG.  33 F  shows retention bushing  74   e  in an undeflected state.  FIG.  33 G  shows the expanded state of bushing  74   e  after insertion of the head of the attachment device into the head  20 . As the screw head is inserted into the tulip, bushing  74   e  is simultaneously pushed upwards and radially expanded (in embodiments such as that shown in  FIG.  33 E  there can be a slit in the ring that facilitates expansion) until the screw head can pop through.  FIG.  33 G  shows the moment right after pop-through, before the bushing  74   e  begins to contract back down to size. As it tries to return to its relaxed state (in the radial sense) it also “rides” the screw head to its lower position in the tulip. When the screw head is put under tension, the friction and contact angles at the interface keep it from expanding again. 
     Referring to  FIG.  32   f   , it is noted that when head subassembly  20  is placed into contact with the implanted support device  80 , that the top of the device junction  82  will push upward against the bottom of retainer ring  74   a . This upward pressure will move ring  74   a  upward within the cavity  28   f . In so doing, the pressure of the inner walls of the pocket against the ring is relieved, and ring  74  (because of the fissure  74   d ) is able to expand to a larger diameter, and therefore receive the junction  82   c  within the internal pocket  74   e  of bushing  74 . Continued compression of junction  82   c  within head subassembly  20  thereafter results in a bottoming out (i.e., contact of the top of the device junction with the surfaces of pocket  59   a ). When the now-installed head subassembly  20  is pulled away from device  80 , the shape of the junction  82   c  will pull ring  74   a  back into the tapered region (as shown in  FIG.  32   f   ), and thus close around the device junction  82   c . In this manner, a subassembled head  20  is able to be popped onto an implanted supporting device  80 , but is thereafter restrained from being removed. 
       FIG.  20 E  shows guiding anchor  10 . A second polymeric bushing  74  is received within a pocket of head  20 . The head, which includes integrally molded bushing  50   b , can then be popped on and over the top of device  80 . The compression of device junction  82  into the spherical inner surface of bushing  74  by way of a tool (not shown) will result in a pop-in, loose inner connection of device  80  and head  20 . 
       FIGS.  21 A  and B show a guiding anchor according to another embodiment of the present invention.  FIG.  21 A  shows a split bushing  51  that includes a spherical pocket that accepts within it the spherical device junction  82   c . This split bushing, with the rod inserted, can be placed vertically downward onto the supporting device  80 . The head can be placed over the bushing and supporting device in a vertical direction, with one or more interface pins  58   e  being accepted into corresponding interface apertures  34   d  of head  20 . 
     Anchor  20  of  FIG.  21 A  includes a bushing  50  that incorporates a split or fissure  59   b  between the rod pathway  52   b  and the pocket  59   a  of bushing  50  in which the device junction  82   c  is received. As shown, as one example, device junction  82   c  is spherical, and the pocket  59   a , although any manner of complementary shapes is contemplated. Because of the pliable nature of the material of bushing  50  and the split  59   b , bushing  50  can be spread apart so that pocket  59   a  can be fit over top of device junction  82 . Preferably, the fit of the device junction within the pocket is a close fit. This preassembly of bushing  50  and support device  80  can then be inserted into cavity  24  from the distal end of cavity  24 . In some embodiments, the outer shape of bushing  50  is generally cylindrical, and fits within a generally cylindrical pocket  24 . In some embodiments, bushing  50  is not rotationally constrained by head  20 . However, as shown in  FIG.  21 A , a pair of projecting retention features  58   e  (which can be molded or inserted into bushing  50  separately) are received within corresponding apertures  34   d . The interlocking of the projections and the apertures prevent relative rotation of bushing  50  relative to head  20 . 
       FIG.  21 A  further shows that after the subassembly of bushing and support device are installed within the cavity, a retaining ring  59   c  (such as a C-clip) is inserted into a slit  27   b  of head  20 . Ring  59   c  maintains its position within the slit, and thus prevents removal of bushing  50  (and support device  80 ) from head  20 . 
       FIG.  22    shows various views of a guiding anchor  10  in which the threaded section  84   b  of a bone screw or other supporting device  80  is threadably received within an aperture  28   e  of a head  20 . A second polymer bushing  74  is received around a preferably spherical device junction, and after full engagement into the head  20  the bushing  74  serves as an interface between the device junction  82  and a pocket  28   a  within head  20 . 
       FIG.  22 A  shows a cannulated supporting device  80  having a distal end adapted and configured for insertion into a bone, and a proximal end having, in some embodiments, a spherical device junction  82   c . A bearing or bushing  74   a  has been preloaded onto junction  82   c . Also shown is a head  20  that in some embodiments includes a pair of opposing arms  26   c  defined between them a cavity  24 . As shown in  FIG.  22 B , the assembly of the supporting device  80  and bearing  74   a  can be threaded through an aperture  28   e  of head  20 . Preferably, aperture  28   e  has an inner diameter that is larger than the minor diameter of the screw threads, but smaller than the major diameter. In this manner, supporting device  80  can be readily threaded through aperture  28   a , and loosely maintained by aperture  28 . 
     Referring to  FIG.  22   c   , it can be seen that the assembly of support device  80  and bearing  74  are received within a pocket  28  of head  20  that has an internal shape for receiving the outer surface of bearing  74   a  with minimal side play, and preferably permitting polyaxial rotation of support device  80  relative to head  20 . 
     An enlargement of the assembly of head  20 , support device  80 , and bearing  74   a  is shown in  FIG.  22 D . In some embodiments, at least one of the opposing arms  26   c  includes a spring arm  26   b  that can be elastically cantilevered radially outward in order to fit around the head retention features  56   a  of bushing container  56 . These cantilever spring loaded arms (connected to the head by live hinges) snap back into place once the corresponding retention feature  56   a  is received within the notch  26   b   1  indicated in  FIG.  22 D . Once the live hinge returns the arm  26   b  back to its normal state (as shown at the top of  FIG.  22 D ), the placement of the retention feature  56   a  within groove  26   b   1  discourages any attempt to remove container  56  in a proximal (vertical) direction, unless a tool is used to radially and preferably elastically move the arms  26   b  out of contact. It is further appreciated from  FIG.  22 D  that the underside of bushing container  56  is shaped so as to fit over the assembled junction and bearing within head  20 , and thus not restrain pivotal motion by physical interference or rubbing. 
       FIG.  23    shows various guiding anchors having different methods and apparatus for retaining a bushing such as a bushing comprising or coated with a polymeric, metallic, or ceramic material within a head  20 .  FIGS.  2431    and A 2  show a separable polymeric bushing  50   a  received within a container having a pair of tapered locking arms  56   c . Bushing  50  has an external shape  58   c  that is adapted and configured to fit within a correspondingly shaped bushing interface  34   c  of head  20 . After insertion of the bushing into the head (preferably with the rod) the connector  56  can be pressed onto head  20 , and snap into a retained position as the arms  56   c  spread out over a corresponding projection on the sides of the head. In FIGS.  234 A 1  and A 2 , the opposing arms  56   c  are each received within a corresponding groove or slot  34   f , each located on opposing sides of head  20 . 
       FIG.  24 B  shows a bushing  58  that is inserted along a slightly elevated angle (relative to horizontal), and then placed within the pocket  34   c . A set screw  42  presses downward on the top of the bushing, and the bushing is captured in the head by the coaction of the set screw and the lip  34   e.    
       FIG.  24    shows a head and bushing design similar to that of the column second from the left, except that the lip  34   e  is located along the top of the head, and the set screw is coupled to the head by internal threads  42   b . The coaction of the top lip  34   e  and the overhanging set screw  42  combine to obstruct any attempt to remove bushing  50 . 
     Referring to FIG.  23 A 1 , an anchor  10  is shown having a head  20  that includes an oblong bushing interface  34   c  that is open at the top. A bushing  50   a  is received within cavity  24 , and because of the flattened lateral sides of both the bushing and the cavity, bushing  50  can slide into cavity  20 , but cannot rotate within cavity  20 . 
     After being nested within cavity  20 , a U-shape taper lock bushing container  56   c  is placed across the top and opposing sides of head  20 . Container  56  includes a pair of downwardly (distally) depending arms  56   c , each which are received within a corresponding lateral channel  34   f  of head  20 . Referring to the bottom, assembled view, it can be seen that the channel  34   f  is open as to one corner of the received arm  56   c , but wraps around the corner of the same outward face of the same arm. Because of this channeled, grasping feature of channel  34   f , an arm  56   c  cannot be laterally pivoted away from head  20 . In some embodiments, each arm  56  further includes a lip or edge  34   e . In those embodiments, the tapered arms can include a complementary-shaped feature at the distal ends of the arms, such that downward motion of the container  56  onto channel  20  results in the arms  56   c  snapping over the retention features  34   e . However, as shown in  FIG.  2432   , each opposing arm can further be constrained within a multi-sided channel by friction. 
       FIG.  23 B  shows an anchor  10  in which a bushing  50  is loaded in the direction  54   b  from the side through a side opening  26   e  in head  20 . In some embodiments, and as shown in  FIG.  23 B , the opening  26   e  preferably includes an upwardly projecting lip or ledge  34   e . Because of this ledge, the insertion of bushing  50  is both lateral and slightly angled downward, and once inserted, the bushing is retained from lateral movement by the inner surface of ledge  34   e . Referring to the top under surface of the side opening  26   e , it can be seen that this top surface is angled upward, in a direction so as to cooperate with the angled insertion of the bushing. 
     After insertion, a set screw  42   a  can be coupled to head  20 , such that the bottom side of the set screw comes into obstruction with any attempt to angularly move the installed bushing upward, thus preventing inadvertent removal. Preferably, the bushing  50  includes a thickened area  56   j  (such as the top corner shown in  FIG.  23 B ) which provides both increased strength for potential contact with set screw  42   a , and also for grasping purposes during insertion. Although the coupling of heads  20  in  FIGS.  23 A,  23 B, and  24   , is shown as being fixed to support device  80 , it is understood that any of the other head to device coupling geometries can also be incorporated. 
       FIG.  24    shows a variation of the concepts of  FIG.  23 B , except as rearranged for top loading. Head  20  preferably includes a top opening  26   f  through which a bushing  50   a  can be inserted. Preferably, there is a ledge  34   e  that extends part way over the top of bushing  50 . As referred to with the anchor of  FIG.  23 B , this ledge  34   e  aids in the retention of a bushing  50   a  that has been inserted downward from the top, and further angled into cavity  24 . In some embodiments, head  20  includes a threaded post  22   c  onto which a set nut  42   d  can be installed and tightened. Set nut  42   d  has an outermost width that is sufficiently large enough to extend over the edge of the top opening  26   f , so as to impede any attempt to remove bushing  50  from cavity  24 . Bushing  50  likewise incorporates a thickened portion  56   j  to aid in insertion and improve distribution of contact stresses. 
       FIGS.  25  and  26    show a pair of guiding anchors according to different embodiments of the present invention. FIGS.  25 A 1 , A 2 , and A 3  show an anchor in which the bushing  50  (preferably with the rod inserted) can be inserted vertically into a pocket of the head  20 . The bushing can be retained within the head by a set screw  42   b  having internal threads that threadably engage external threads  22   a  of head  20 . 
       FIG.  25 A  shows an anchor head  20  including a pair of parallel arms  26   c  that define between them a cavity adapted and configured for receiving within it a bushing  50 . Preferably, cavity  24  includes a bushing container interface  26   d   1  that is complementary in shape to a portion of the bushing  50 . As can be seen in  FIGS.  25 A and  25 B , this shape  26   d   1  includes generally flat, parallel sides. The complementary fit of bushing  50  within such a cavity  24  minimizes or eliminates any relative motion of the bushing relative to the head  20 . After a bushing  50  has been inserted from the top into cavity  24 , a cap  42   b  having internal threads is threadably coupled to external threads  22   a  on head  20 . Once the cap is tightened, cavity  24  is closed and bushing  50  is contained within it. It is further noted with regards to the drawing at the bottom of  FIG.  25 A  that the opposite sides of the cavity  24  include narrower bushing retention features  26   d   2  that surround the portions of the bushing around rod pathway  52   b . Therefore, by having an internal cavity that is wider (between walls  26   d   1 ) at the center and narrower (between walls  26   d   2 ) at the end, bushing  50  cannot be removed along the rod axis. 
     The anchor  10  shown in FIGS.  26 B 1  and  26 B 2  also captures a bushing  50  within an internal cavity  24  having wider and narrower side walls  26   d   1  and  26   d   2 , respectively, for receiving therein a bushing  50 . In some embodiments, bushing  50  preferably includes a top projection or button  51   b  that is adapted and configured to be received with a retention mechanism  42 . The anchor of  FIG.  26    incorporates a C-clip  42   c  that fits within a slot or groove  22   b , as best seen in figure of  FIG.  26 D . A middle figure of FIG.  26 B 2  shows a cross sectional view in which the C-clip is captured within groove  22   b  and surrounding the projection  51   b . In some embodiments, portions of the clip  42   c  come into contact with a top annular surface of bushing  50 . FIG.  26 B 2  shows a guiding anchor  10  in which the spherical device junction  82   c  is received within a tapered pocket  28   f  of head  20 . A separable polymeric, metallic, or ceramic bushing (or coating)  50   a  is received within an internal pocket of head  20 , and held in place by a c-clip retained within a groove  22   b.    
       FIGS.  27  and  28    shows a guiding anchor  10  according to another embodiment of the present invention. Head  20  is constrained to a vertebra  4  by a loop  44   b  of a flexible connector, in a manner similar to the BandLoc (™, OrthoPediatrics Corporation) anchors. Head  20  includes a polymeric bushing  50  that provides a pathway  52  for a rod  4 . The head  20  can be assembled onto the rod, and subsequently attached by connector  44  to the vertebra. After the loop  44   b  is sufficiently tight, a threaded cap  45  is installed to capture the bushing and compress the flexible connector. 
       FIGS.  27 A,  28 B,  28 C and  27 D  show different views of an anchor  10  in which the support device  80  comprises a pair of slots  43  integrated into head  20 , and coupled to a bone by a flexible loop  44   b  around a vertebrae in a manner similar to that shown in U.S. Pat. No. 9,173,685, issued Nov. 3, 2015, titled TETHER CLAMP &amp; IMPLANTATION SYSTEM and U.S. Pat. No. 10,595,904, issued Mar. 24, 2020, titled TENSIONING INSTRUMENT &amp; BAND CLAMP TENSIONING SYSTEM, incorporated herein with regards to description of the manner of using a flexible container for retention around a bone, and except as inconsistent with the description provided herein. 
       FIG.  27 A  shows a head  20  located at least in part internally within a bushing container  56 . Bushing container  56  includes a first segment  51  of a polymeric bushing, and adapted and configured to be installed in the top of cavity  24 . It is noted that cavity  24  is partly incorporated in container  56 , and partly incorporated in head  20 . In the bottom of cavity  24  (within head  20 ) is a bushing  50  located within a groove  34   f  of head  20 . 
     Preferably, head  20  includes a pair of threaded opposing arms  26   c  that wrap around the bottom portion of cavity  24 . Referring to  FIG.  28 B , it can be seen that these opposing arms are received within corresponding head retention features  56   a . In some embodiments, these retention features  56   a  have a shape that is complementary to the shape of the arm  26   c , as best seen in  FIG.  27 D . In some embodiments, as these arms  26   c  are fully received within slots  56   a , as best seen in  FIGS.  27 A and  28 C , the top surfaces are generally flush. 
     Referring to  FIGS.  28 B and  27 D , it can be seen that a set screw  42   a  can be threadably received by the arms  26   c , and when fully tightened received within a topmost chamber  57  of container  56 . As the set screw is tightened, the bottom of the set screw pushes against the upper surface of the pocket  57 , and locking together the head  20  and container  56 . The interface between head  20  and container  56  is adapted and configured such that a portion of the bottom of container  56  presses against the flexible connector  44  within the topmost slot  43 , and as shown in  FIG.  28 C . This compression of connector  44  places sufficient friction on connector  44  so as to discourage any relative movement of connector  44  relative to head  20 , in a manner similar to that discussed with the anchors of  FIGS.  15  and  16   . Further consistent with those figures, preferably an end of the connector passing through the bottom slot includes a connector retention device, such as an enlarged head that can be received within the entrance to the bottom slot  43 , but which is too large to pass through the slot  43  itself. 
       FIG.  29    shows one embodiment of a guiding anchor  10  according to another embodiment of the present invention, and the same as previously discussed with regards to FIG.  13 C 2 . It can be seen that in some embodiments the first ring  70   a  of support arm  70  is set at an angle relative to the portion of the support arm that is received within a pocket of head  20 . 
       FIG.  29    shows an anchor  10  according to another embodiment of the present invention, and as previously shown and discussed with regards to  FIG.  13   . Anchor  10  includes a bushing container  56  comprising a ring  70   a  supported from a rigid arm  70   g . Referring to  FIG.  29 B , it can be seen that the rigid arm extends through a cavity  24   b  within a head  20 . One end of the support arm  70  includes an enlarged head  70   e  that has a width greater than the width of the opening between the arms  26   c . Rod  70  is inserted within cavity  24   b  in a direction  35  from above. A set screw or other device coacts with the arms  26   c  to enclose the cavity and constrain support arm  70  therein. In some embodiments, set screw  42  is locked into the threaded interface with head  20 , but bearing only minimally on arm  70  and not preventing rotation of the arm within the cavity. In still other embodiments, the set screw  42  is locked in the threads and maintains the roll angle of arm  70  relative to head  20 . 
     Ring  70   a  of container  56  supports a bushing  50  that can have any type of rod interface, such as, by way of example, a rod to bushing interface that is cylindrical  60   a , semi-spherical  60   b , non-cylindrical or oblong  60   c , including rod pathways that are offset from the centerline of the bushing outer diameter. 
     The arm  70  is further adapted and configured to provide various angular and translational offsets of the rod  4  (not shown) relative to head  20 . Referring to  FIG.  29 B , it can be seen that the ring  70   a  supports a pathway  52   a  for a rod that is laterally (i.e., in yaw) offset from the axis  70   f  of arm  70  as established by cavity  24  by an Angle1. Referring to  FIG.  29 C , support arm  70  can further be established at a pitch Angle2 relative to centerline  70   f . This angular offset Angle2 can further change the Height of the rod pathway above the implantation site. Further,  FIG.  29 C  shows that this Height can be adjusted as arm  70  is rotated within cavity  24 . In some embodiments of the present invention, a support arm  70  can be offset as indicated by Angle1, or by Angle2, or by a combination of both. In some embodiments, it is contemplated that there are kits in which a plurality of arm assemblies  70  are provided, each with a different relationship of Angle1 and/or Angle 2. 
     Referring to  FIG.  29 C , it can be seen that there are a pair of slots  43  between cavity  24  and one or more implantation spikes  86  (the latter aiding in maintaining the position of anchor  10  on a bone). In some embodiments, slots  43  provide a means for attaching anchor  10  to a spine by a flexible connector  44 , as discussed previously with regards to  FIGS.  28 ,  15 , and  16   . However, yet other embodiments contemplate any manner of support device  80  shown herein. 
       FIGS.  30  and  31    show a guiding anchor  10  according to another embodiment of the present invention, and similar to the guiding anchor of  FIGS.  9 A and  18 A and  18 D , except that in  FIG.  30    the head  20  is anchored to a vertebra by a loop  44   b  of flexible connector, as discussed with regards to  FIG.  29   . 
     The anchor  10  of  FIGS.  30  and  31    includes a bearing container  56   e  that supports the midsection of a bushing  50 . As best seen in the exploded view of  FIG.  30 B , an assembly of a bearing container  56   e  and bushing  50  have an external shape that is generally complementary to the internal shape of a cavity  24  of head  20 . In some embodiments, the bushing container includes retention features  58  shown as squared-off top and lower ledges. These ledges are further carried into each of the sides of the bushing  50  (as shown), although it is understood that in yet other embodiments the squared-off ledges (or other retention features) are present only on the central container  56   e.    
     Preferably, container  56   e  is a ring that has molded onto it a bushing  50  on either side. In yet other embodiments the bushing  50  may be a unitary body, with a ring  56   e  placed around a central portion. 
     The bushing container assembly is preferably inserted in a direction along the rod pathway  52   a . After it is in place within cavity  24 , a set screw or other retaining device  42   a  can be attached to head  20  and tightened so as to apply a compressive, frictional force onto sleeve  56  (and in some embodiments, also on to one or more of the bushing portions  50 ). 
     Head  20  preferably includes a pair of slots  43 , one of which extends between head  20  and the bottom of the bushing assembly, and the other of which extends within an additional slot underneath this first slot (in a manner similar to that shown in  FIG.  28   ). In a manner similar to that shown in  FIG.  28 C , the compression of the bushing retainer  42  onto bushing container  56   e  results in a frictional, compressive locking force onto the portion of the flexible connector extending between head  20  and the underside of bushing  56   e . Preferably, a connector retention device  44   c  is located on the end of the flexible connector that extends through the bottommost slot. 
     Although what has been shown and described is the connection of anchor  10  by way of a support device comprising a flexible connector, it is understood that head  20  can alternately incorporate any of the support devices  80  shown herein. In some embodiments, anchor  10  further includes an orientation of slots  43  that provide for tension of the flexible connector  44  in a direction generally parallel to rod pathway  42   a . In contrast, it is noted that the slots  43  shown in the anchor of  FIG.  28    are oriented so as to be placed in tension by application of a force that is generally orthogonal to the direction of the rod pathway. 
       FIG.  34    shows various views of an anchor according to another embodiment of the present invention;  FIG.  34 A  shows a perspective, partly exploded view;  FIG.  34 B  shows a fully assembled, perspective view; FIGS.  34 C 1  and C 2  show front and side views, respectively, of the assembled anchor; and  FIG.  34 D  shows a cross section of the assembled anchor, taken along the axis of the rod pathway. 
       FIG.  34    show various views of an anchor  10  that includes a split polymeric bushing that supports both sides of a rod.  FIG.  34 A  shows an exploded view, having a bushing container  56  that includes within it a pair of proximally-located bushing segments  51   p . Further shown is a head  20  having a pair of opposing, internally threaded arms  26   c  that includes a pair of distally-located bushing segments  51   d , each arranged in a corresponding groove  34   d . In some embodiments, each of the proximal segments  51   p  and the distal segments  51   d  provide, when fully assembled, three hundred and sixty degrees of interface with a rod within pathway  52   a . However, the present invention also contemplates those embodiments in which any of the bushing segments can be of lesser arcs, such that there can be a gap in the surrounding of the rod. Referring to  FIG.  34 D , it can be seen that the distal segments  51   d  are each retained within a corresponding groove  34   d . The bushing segments  51   p  are likewise each received within corresponding grooves or pockets  58 . In some embodiments, the bushing segments are separate, whereas in other embodiments the bushing segments are integrally molded with the corresponding head or bushing container. 
     Bushing container  56  further includes head retention features  56   a  that are adapted and configured to be received within corresponding bushing container retention features  36  placed within head  20 . As best seen in  FIGS.  34 A and  34 B , the bushing container features  56   a  each downwardly depend from the bottom of container  56 , preferably defining a portion of the groove  58 , and are slidably received within slots  36 . The mating of extensions of  56   a  and slots  36  assists in providing accurate line-up of the ends of the bushings  51   p  within the top portion of grooves  34   d  (as best seen in  FIG.  34 D ). These downwardly depending ends of segments  51   p  thus overlap, being contained in both a groove within the bushing container, and when assembled also within a groove of the head. Referring to  FIG.  34 D , it can be seen that the split line between the head and bushing container is preferably located above (proximal) to the centerline of the assembled rod. 
     Anchor  10  of  FIG.  34    includes still further features that locate container  56  relative to head  20 . Referring to  FIG.  34 A , it can be seen that head  20  includes a generally flat surface  26   d  that abuts against a corresponding flattened head interface  58   g . Referring to  FIGS.  34 B  and  34 C 1  and C 2 , it can be seen that the abutment of each bushing container interface  26   d  with each head interface surface  58   g  provides for an interlocking or clocking of container  56  onto head  20 . Referring to  FIG.  34 D , it can be seen that the bushing container further includes a through aperture  59   d  through which a support device  80  can be manipulated. 
       FIG.  35    show various views of a portion of an instrument being used to remove the head of an anchor;  FIG.  35 A  shows a cross sectional view of the assembled and implanted anchor;  FIG.  35 B  shows the implanted anchor with a portion of a first instrument placed over the head;  FIG.  35 C  is a cross sectional representation of the apparatus of  FIG.  35 B ; and  FIG.  35 D  is a cross sectional representation of a second instrument being placed over the apparatus of  FIG.  35 C . 
       FIG.  35    show a version of a pop-in retained anchor  10 , similar to that shown in  FIGS.  18 ,  20 ,  21 C, and  26   , but with a modified pop-in retaining ring to facilitate removal of the head  20  from the support device  80 . 
     Referring to  FIG.  35 A , anchor  10  preferably includes a support device retention ring  32   a , which preferably includes a spherical pocket to support therein a spherical support device junction  82   c  so as to permit polyaxial movement of head  20  relative to anchor  80 . Preferably, retention member  32   a  permits a pop-on assembly of a preassembled head  20  (including a bushing  50 ) onto a previously implanted support device  80 . The head to support device member  32  of anchor  10  preferably includes a pair of outwardly extending projections or wings  32   e  the ends of which are externally accessible through windows or cutouts  28   g  on opposite sides of head  20 . 
       FIGS.  35 B and  35 C  show the assembled anchor of  FIG.  35 A  over which a first inner sleeve  90   a  of an instrument has been placed by a surgeon. Sleeve  90   a  includes a flexible portion preferably defined between a pair of slits  90   d , with flexible sections being presented on opposite sides of sleeve  90   a , and in general alignment with wings or tabs  32   e . As best seen in  FIG.  35 C , each of the flexible portions of sleeve  90   a  include a ledge or projection or tooth  90   c  that slides in place and is received on the underneath (distal) side of each wing  32   e . These teeth  90   c , being integral with the flexible portion  90   c , bend outwardly out of the way when sleeve  90   a  is installed, but elastically spring back into location after passing over the outward ends of wings  32   e.    
       FIG.  35 D  shows a subsequent act of removal, which is to insert a second, outer sleeve  90   b  over the inner sleeve  90   a . Preferably, the inner diameter of outer sleeve  90   b  is a close sliding fit with the outer diameter of inner sleeve  90   a , as shown in  FIG.  35 D . The placement of sleeve  90   b  over sleeve  90   a  prevents flexible portion  90   d  from expanding outward. Therefore, when the two sleeves  90   a  and  90   b  are pulled upward (in a proximal direction) the teeth  90   c  remain engaged with the underside of the corresponding wing  32   e  (because the teeth  90   c  can no longer expand outward). Therefore, upward movement causes an inward compressing of wings  32   d , which will result in an enlargement of the distal aperture  32   d  that surrounds the underside of spherical junction  84   c . As this aperture opens, the assembled head (with bushing and retaining member  32   a ) can be pulled over the spherical head  84   c , and removed from the support device  80 . In the embodiment shown in  FIGS.  35 A and  35 D , the head  20  can include a further extension  28   k  that generally surrounds the distalmost portion of member  32   a , and proximate to aperture  32   d . In such embodiments, the upward movement of the instrument assembly, and therefore of the wings  32   e , results in a movement of the annular material surrounding aperture  32   d  through a conical annular area between the inside of extension  28   k  and the outside of head  84   c . In this manner, as aperture  32   d  opens it further slides up (and generally maintains close contact) with the spherical head  84   c . These extensions  28   k  assist in preventing the unwanted expansion of aperture  32   d , as could be a result of relative motion among the polyaxial head  20 , supporting device  80 , and surrounding tissue. 
       FIG.  36    show various views of an anchor according another embodiment of the present invention;  FIG.  36 A  is a perspective view of a portion of an assembled anchor;  FIG.  36 B  is an exploded view of the anchor of  FIG.  36 A ;  FIG.  36 C  is a top perspective view of the anchor of  FIG.  36 A ;  FIG.  36 D  is a cross sectional view taken perpendicular to the rod pathway of  FIG.  36 A ;  FIG.  36 E  is a partial cutaway of the apparatus of  FIG.  36 D . 
       FIG.  36    show various views of an anchor  10  including a tapered-fit bushing contained within an anchor head  20  by means of a tapered fit, and being connected to a support device by a spherical interface for polyaxial movement. Referring to  FIG.  36 B , a bushing  50  having a central cylindrical rod pathway (by way of example only) and including a top bushing extension  53   a  and a bottom bushing extension  53   b  is received within a cavity  24  of a head  20 . The bottom bushing extensions  53   b  of bushing  50  are placed on generally opposite sides of the bushing centerline, and each is received within a corresponding interface groove  34   g . Referring to  FIG.  36 D , it can be seen that each bottom extension  53   b  extends outwardly from a central underneath surface, and extending laterally and oppositely into rectangular cross sections that fit within one of the grooves  34   g . The placement of bushing extensions  53   b  within grooves of the attachment head  20  minimizes any tendency for rotation of the bushing with the cavity  24 . In some embodiments, the bottom extension  53   b  extends vertically from the bottom of slot  34   g  up to the rod pathway  52   a . In this manner, the extensions  53   b  provide support and clearance of rod  4  relative to head  20  so as to prevent contact with head  20 . 
     Preferably, the bushing  50  and head  20  interface with one another by a tapered sidewall  34   k  that extends on either side of rod pathway  52   a . Preferably, bushing  50  and anchor  20  have complementary-shaped conically tapered abutting surfaces. However, it is further understood that the conical angle of the exterior of bushing  50  does not have to be the same as the conical inner diameter of cavity  24 . Therefore, the interface  34   k  between the bushing and the head is preferably parallel, but is not so constrained in other embodiments, and could be slight diverging or slightly converging (with reference to the proximal to distal axial direction). Preferably, bushing  50  is a snug fit in cavity  24 , and as a result forms a reliable preliminary lock between head  20  and bushing  50  as the anchor is assembled onto the implantation site. 
     After a subassembly of the rod, bushing, head, and support device has been achieved, a C-clip  42   c  is placed within a groove  27   a  of head  20 . Clip  42   c  includes a split  42   d  that is adapted and configured to contain within it the top bushing extension or projection  53   a .  FIG.  36 D  shows the assembly of clip  42   c  into groove  27   a . Clip  42   c  preferably prevents vertical pull-out of bushing  50 , prevents rotation of bushing  50  within cavity  24 , and further provides added rigidity to bushing  50  by ensuring that there is support over the rod by the bottom surface of the C-clip.  FIG.  36 E  shows a support device  80  having a spherical interface  82   c  that is received with a spherically shaped pocked of head  20 . However, it is understood that nay of the support devices and methods shown herein can be adapted into the anchor of  FIG.  36   . 
     In one embodiment, the device of  FIG.  36    are implanted in the following manner: (1) insert screw and tulip head into bone; (2) place the bushing onto the rod; (3) reduce the bushing into the tulip; and (4) use the clip to lock the assembly together. 
       FIG.  37    depict various views of an anchor  10  according to another embodiment of the present invention;  FIG.  37 A  shows a side, perspective view of a portion of the assembly;  FIG.  37 B  shows a top planar view of a portion of the assembly;  FIG.  37 C  shows a partly exploded, side, perspective view of a portion of the assembly; and  FIG.  37 D  shows a side cross sectional view of a portion of the assembly. 
       FIG.  37    depict an anchor  10  according to one embodiment of the present invention that includes a bushing  50  that can be assembled into a head  20  such that it is self-retained within the cavity  24  of head  20 . In some embodiments, this assembly can be done prior to implantation, or during implantation. 
       FIG.  37 D  shows a cross sectional view of the assembled anchor  10 . A polymer bushing  50  with a preferably cylindrical section is shown, along with a plurality of outwardly expanding tabs  55 , each connected to the cylindrical portion by a living hinge. Bushing  50  is inserted into the cavity  24  in the direction of rod pathway  52   a . Referring to  FIG.  37 C , the bushing  50  can be seen prior to insertion, and aligned with one end of cavity  24 . The cylindrical section of bushing  50  is first inserted, and after being fully inserted, will rest within a preferably cylindrical groove or ledge  34   g   1 . Ledge  34   g   1  prevents bushing  50  from being pushed completely through head  20 . As the opposite end of bushing  50  (with the hinged tabs  55 ) enters cavity  24 , each tab is bent inward slightly (as permitted by the slits or cutouts between adjacent tabs), so as to pass underneath the entrance to cavity  24 . After passing through the entrance, and when fully inserted, the tabs  55  spring back into a groove  34   g   2  that has an inner diameter larger than the inner diameter of the inlet to cavity  24 . Once fully nested within cavity  24 , the opposing grooves or ledges  34   g   1  and  34   g   2  prevent bushing  50  from being axially removed from head  20 . 
     Referring again to  FIG.  37 D , it can be seen that the head  20  includes a generally cylindrical pocket  28   b  that receives within it an interface member  32   b . Device member  32   b  includes an internal pocket that preferably has a shape complementary to that of the external shape of the device junction  82 . As shown, the device junction is generally spherical, permitting rotation of head  20  in three directions relative to support device  80 . Referring to  FIGS.  37 B and  37 C , it is shown that head  22  includes a top through aperture  22   d  through which the surgeon can access the driving portion of support device  80 . 
       FIGS.  38 A and  38 B  depict an anchor assembly  10  according to another embodiment of the present invention.  FIGS.  38 A and  38 B  show implanted and non-implanted perspective depictions of an assembled guiding anchor  10  that includes, in some embodiments, a pair of laterally, spaced-apart bushings  50  that are supported by a head  20 . 
     In one embodiment, head  20  is coupled to a spinous process  2   a  (see  FIG.  38 A ) by a flexible connector. A loop of the flexible connector extends from a first slot  43 , wraps around the spinous process  2   a P, and is received within a second slot  43  (not shown) in a manner similar to that shown in  FIG.  28   . One end of the flexible connector includes a connector retention device  44   c  which includes an enlarged end that is incapable of passing through slot  43 . The other, free end of the flexible connector extends through the topmost slot  43 , where it can be held in compression between a support arm  70  and an inner surface of head  20 . 
       FIG.  38 B  shows a non-implanted depiction of anchor  10 . Anchor  10  includes a readily separable component that includes a central support arm  70  and the laterally extending bushing supports  56 . The arm  70  is adapted and configured to fit within an internal passageway of head  20 , in a manner similar to the internal support of rod  4  as shown in  FIG.  28 B . Referring again to  FIG.  38 B , as set screw  42   a  is tightened within the threads of the opposing tulip arms  26   c , friction between connector  44  and central support  70  (above) and a surface of head  20  (below) in frictional compression. 
     Support arm  70  includes on opposing ends a preferably integral bushing container  56 . Each container  56  includes within it a bushing  50  that is adapted and configured to slidingly receive within it a rod (not shown). The bushings  50  include rod interface, internal shapes  60  which are shown to be noncylindrical, or oblong, or oval-shaped. It is further understood that the interior shape of the bushing can be of any type that limits or constrains certain movements (rotation or translation in one or more directions), while permitting axial sliding of the rod, and further permitting sideways or lateral clearance to accommodate rod centerlines that do not necessarily pass through the center of the bushing. 
     While the inventions have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.