reference now will be made in detail to the presently preferred embodiments of the invention , one or more examples of which are illustrated in the accompanying drawings . each example is provided by way of explanation of the invention , which is not restricted to the specifics of the examples . in fact , it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention . for instance , features illustrated or described as part of one embodiment , can be used on another embodiment to yield a still further embodiment . thus , it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents . the same numerals are assigned to the same components throughout the drawings and description . a presently preferred embodiment of the apparatus for and method of anchoring a pedicle screw into a vertebral body is shown in relation to fig1 . initially , apparatus and method suitable for use wherein there has been an open incision will be described . in accordance with an embodiment of the present invention , a fluid insertion device provides cementitious fluid through a hollow feeder tube and thence into a fluid delivery probe that is selectively attachable and detachable to the proximal portion of a cannulated pedicle screw . as shown in fig1 , an embodiment of the apparatus of the present invention can include a fluid insertion device that is schematically represented and indicated by the numeral 10 . the discharge end 10 b of the fluid insertion device 10 is at the distal end 10 b thereof and connected to the proximal end 20 a of the hollow feeder tube 20 . as shown in fig3 a , the distal end 20 b of the feeder tube 20 is connected to the proximal end 30 a of the fluid delivery probe 30 . the distal end 30 b of the fluid delivery probe 30 is inserted into and connected to the proximal end 42 a of the cannula 44 that is defined through the central axis of the shaft 42 of a cannulated pedicle screw 40 . the distal end 30 b of the delivery probe 30 is selectively detachable and attachable to the proximal end 40 a of the cannulated screw 40 . as schematically shown in fig1 , the hollow feeder tube 20 has a proximal end 20 a that is selectively connectable and disconnectable to the fluid insertion device 10 . as shown in fig3 a for example , the fluid delivery probe 30 has a proximal end 30 a that is connected to the distal end 20 b of the feeder tube 20 . as shown in fig3 a , the pedicle screw 40 has a proximal portion 40 a with a head 41 at the free end of the proximal portion 40 a and an intermediate portion 40 c connecting the proximal portion 40 a and the distal portion 40 b . a tip 43 is provided on the free end of the distal portion 40 b of the screw 40 . the pedicle screw 40 can have either an uniaxial head ( fig1 , 2 , 3 a , 3 b , 3 c , 5 and 7 ) or a polyaxial head ( fig4 and 6 ). the uniaxial head remains fixed with respect to the central axis of the elongated body of the screw 40 . the polyaxial head is configured to be pivotable with respect to the central axis of the elongated body 42 of the screw 40 . some examples of polyaxial heads of pedicle screws are disclosed in u . s . patent application publication no . us2005 / 0228385a1 and u . s . pat . nos . 5 , 474 , 555 and 5 , 554 , 157 , which are hereby incorporated herein in their entireties by this reference . as shown in fig4 , the proximal end of the shaft 42 of the screw 40 defines an arcuately shaped bulb 35 that is configured to be rotatable relative to a cavity defined in a socket 36 formed in the distal end of the head 41 of the screw . the bulb 35 defines a fill cavity 42 a at the proximal end of the cannula 44 , and the fill cavity 42 a is configured to receive therein the distal end 30 b of the fluid delivery probe 30 . as shown in fig3 a for example , the axially elongated pedicle screw 40 has a cannula 44 extending axially through generally the central axis of the screw 40 . the cannula 44 is defined by the interior surface of the sidewall 44 a of the screw . as shown in fig2 , the cannulated pedicle screw 40 can be is provided with one or more fluid discharge openings 45 through a generally distal portion 40 b thereof . at least one fluid discharge opening 45 extends from the cannula 44 ( indicated schematically in fig2 by the dashed line ) through the sidewall 44 a of the screw 40 in the distal portion 40 b . no discharge openings 45 are provided through the sidewall 44 a of the shaft 42 of the screw for most of the length of the shaft &# 39 ; s length , as only the distal portion of the shaft is configured with any discharge openings 45 as shown in fig2 for example , the discharge opening 45 of the screw 40 can be configured as an elongated slot that has its longest dimension extending generally in the axial direction . the elongated slot desirably can be configured as a unidirectional slot that opens only through one section of the sidewall 44 a of the screw 40 and thus permits the surgeon to direct the discharge of cementitious fluid in a preferred direction into the vertebral body 60 . alternatively , the slot can be a through slot that extends completely through from one sidewall of the screw 40 to the opposite sidewall of the screw 40 . alternatively , a plane extending through a first slot can be disposed perpendicular to a plane extending through a second slot . alternatively , one of the slots can be disposed at least in part , closer to the tip 43 of the screw than any portion of the other slot . as shown in a cross - sectional view in each of fig3 b , 3 c and 3 d for example , the discharge opening of the screw 40 can be configured as a cylindrically - shaped bore that radially extends through the sidewall and into the cannula . as shown in fig3 b , 3 c and 3 d , more than one such bore can be provided , with the number of bores determining the flow rate from the cannula . as shown in fig3 b and 3d , a first pair of bores 45 a , 45 b can be disposed with each of the bores 45 a , 45 b in the first pair disposed on opposite sides of the screw 40 and with each bore &# 39 ; s 45 a , 45 b central axis slightly offset from the other bore &# 39 ; s 45 a , 45 b central axis when viewed relative to the axial direction of the screw 40 . similarly , as shown in fig3 b and 3d , a second pair of bores 45 c , 45 d can be disposed farther from the tip 43 of the screw 40 than the first pair of bores 45 a , 45 b . each of the bores 45 c , 45 d in the second pair can be disposed on opposite sides of the sidewall 44 a of the screw 40 and with each bore &# 39 ; s 45 c , 45 d central axis slightly offset from the other bore &# 39 ; s 45 c , 45 d central axis when viewed relative to the axial direction of the screw 40 . however , the central axes of all four of the bores 45 a , 45 b , 45 c , 45 d desirably reside in the same plane that includes the central axis of the screw 40 . alternatively , as shown in fig3 c for example , each of a pair of bores 45 e , 45 f can be disposed on the same side of the sidewall 44 a of the screw 40 and with each bore &# 39 ; s 45 e , 45 f central axis residing in the same plane that includes the central axis of the screw 40 . this configuration permits the surgeon to direct the discharge of cementitious fluid in a preferred direction into the vertebral body . one of the bores 45 f can be disposed closer to the proximal end 40 a of the screw 40 than the other bore 40 e . alternatively , as shown in fig3 e and 6a for example , the discharge opening of the screw can be configured as a cylindrically - shaped bore 45 g , 45 h , 45 i , 45 j that extends through the sidewall 44 a and into the cannula 44 along a central axis that is not normal to the central axis of the cannula 44 and thus is not in a radial direction . as shown in fig3 e and 6a , the bore &# 39 ; s 45 g , 45 h , 45 i , 45 j axis desirably extends at a 45 degree angle from the central axis of the cannula 44 , which thus is at a 45 degree angle from the radius that extends from the central axis of the cannula 44 . other angular orientations can be chosen . having a variety of angular orientations provides the surgeon with maximum flexibility in accommodating the different anatomies that are likely to be encountered . as shown in fig3 e and 6a , more than one such bore 45 g , 45 h , 45 i , 45 j can be provided , with the number of bores 45 g , 45 h , 45 i , 45 j determining the flow rate from the cannula 44 . moreover , each of the bores 45 g , 45 h , 45 i , 45 j can be disposed on the same side of the sidewall 44 a of the screw 40 and with each bore &# 39 ; s 45 g , 45 h , 45 i , 45 j central axis residing in the same plane that includes the central axis of the screw 40 . this configuration permits the surgeon to direct the discharge in a preferred direction into the vertebral body . as shown in fig3 e , each bore 45 g , 45 h has an entrance orifice 55 a through the interior surface of the sidewall 44 a that defines the cannula 44 . each bore 45 g , 45 h has an exit orifice 55 b defined through the exterior surface of the sidewall 44 a that defines the cannula 44 of the screw . the exit orifices 55 b of the bores 45 i , 45 j can both be closer to the proximal end of the screw 40 than the entrance orifices 55 a formed in the sidewall 44 a of the screw 40 . one of the bores 45 g can be disposed closer to the tip 43 of the screw 40 than the other bore 45 h . moreover , it is believed that when the cementitious fluid hardens , the direction in which the fluid enters the vertebral body will result in greater integrity of the hardened fluid in that same direction . thus , it is desirable to direct at least one bore in the direction of the bore 45 h shown in fig3 e that points back toward the proximal end of the screw 40 . in this way , the fluid directed from this bore 45 h will act in the same manner as a fish hook barb and retard any tendency for the screw to move out of the vertebral body . accordingly , as shown in fig6 a , an additional embodiment of the screw 400 desirably has more than one such bore 45 i , 45 h . to aid the surgeon in positioning the discharge opening 45 , whether slot ( s ) or bore ( s ), whether radially through the sidewall 44 a or at an angle through the sidewall 44 a , the proximal end of the screw can be provided with one or more markers that indicate where and how the discharge opening ( s ) is / are oriented so that whether the surgery is done percutaneously or open , the desired position of the discharge opening ( s ) could be observed prior to introducing the cementitious material . as shown in fig3 d and 3e , in embodiments of the screw having a cannula 44 that extends completely through the tip 43 of the screw 40 , it may be desirable to block off the opening 43 a of the cannula 44 in the tip 43 of the screw . in such cases , a solid steel ball 46 can be introduced into the cannula 44 and rest on a shoulder portion 44 b within the cannula 44 to thereby block off the opening 43 a in the tip 43 of the screw 40 . this opening 43 a in the tip 43 of the screw is desirably of a smaller diameter than the diameter of the cannula 44 in the remaining portion of the shaft of the screw . in accordance with an embodiment of the method of the present invention , the distal portion of the screw can be introduced through the pedicle of a vertebra and into the vertebral body of the vertebra . this can be done in a conventional way such as using an awl and / or a punch to start a hole through the pedicle and then rotating the screw about its longitudinal axis with a suitable implement that results in the advancement of the screw into the pedicle due to the pitch of the threads formed in the exterior surface of the wall that forms the shaft of the screw . desirably , as shown in fig1 , the exterior surface of the wall of the shaft of the screw is provided with threads 47 that are configured with suitable pitch that is designed to render the screw self - tapping upon rotation of the screw . in accordance with an embodiment of the method of the present invention , a fluoroscope desirably can be used to observe the advancement of the screw into the vertebral body 60 . when the fluid discharge opening 45 in the screw 40 is oriented so as to direct fluid flowing out of the discharge opening 45 in a desired direction into the vertebral body of the vertebra , then the advancement of the screw 40 can be stopped . the particular embodiment of the screw 40 will be chosen according to the particular vertebra in which the screw 40 is to be placed . in accordance with an embodiment of the method of the present invention , a fluid delivery probe can be provided and connected to a filler tube that is connected to a fluid insertion device . as shown in fig3 a for example , a fluid delivery probe 30 has a proximal end 30 a connected to the distal end 20 b of the filler tube 20 . as schematically shown by the arrows 21 a , 21 b , 21 c in fig1 , the proximal end 20 a of the filler tube 20 is connected to the fluid insertion device 10 . in the embodiment shown in fig3 a , the fluid delivery probe 30 extends axially in generally the same direction as the filler tube 20 and thus is generally “ in - line ” with the axis of the filler tube 20 . in the embodiment of fig6 a and 6b , the head of the screw 400 is capped so as to preclude direct axial access to the cannula 44 through the head . thus , access to the cannula 44 by the fluid delivery probe 300 must be directed from the side of the head as shown schematically by the arrow 301 in fig6 a . in the embodiment shown in fig6 a and 6b , the proximal end 300 a of the fluid delivery probe 300 extends axially with the distal end 20 b of the filler tube 20 . however , the distal end 300 b of the fluid deliver probe 300 extends axially generally at a right angle to the axial direction of the filler tube 20 and thus is generally “ out - of - line ” with the axis of the filler tube 20 . the embodiment shown in fig6 a and 6b is thus adapted for use in connection with a screw head that is not threaded on the exterior to receive a nut 50 such as shown in fig3 a . as shown in fig3 a and 6a , each fluid delivery probe 30 , 300 defines therein a hollow channel 31 , 310 that is disposed generally along the central axis of the fluid delivery probe . in the embodiment shown in fig6 a , the channel 310 forms two legs 310 a , 310 b joined by a right angle elbow 310 c . the diameter of the channel 310 desirably is larger than the diameter of the cannula 44 in the shaft of the screw 400 , but desirably is at least as large as the diameter of the cannula 44 , which desirably is formed as a through bore at least as large as would be found in a 10 / 11 gauge injection needle ( 1 . 69 mm / 0 . 0665 inches ). however , in some embodiments , the diameter of the bore in the cannula can be as small as would be found in a 14 gauge needle ( 1 . 628 mm / 0 . 0641 inches ) or a 15 gauge needle ( 1 . 450 mm / 0 . 0571 inches ). in the embodiment shown in fig2 and 3a , each of a pair of opposed ribs 32 a , 32 b extends radially from the exterior surface of the fluid delivery probe 30 . the proximal end 40 a of the head 41 of the screw 40 includes two opposed arms 48 a , 48 b that extend axially and have threaded exterior surfaces . the surfaces of the arms 48 a , 48 b that face one another are the interior surfaces , and each interior surface of each arm defines a recess 49 a , 49 b that is configured to receive therein one of the ribs 32 a , 32 b that is defined on the exterior surface of the fluid delivery probe 30 . in accordance with an embodiment of the method of the present invention , the fluid insertion device 10 can be operated so as to fill the filler tube 20 and fluid delivery probe 30 with fluid so that all air is purged from the filler tube 20 and the fluid delivery probe 30 . as schematically shown in fig1 for example , the fluid insertion device 10 can be operated to deliver cementitious fluid 62 to the filler tube and thence to the channel ( not indicated in fig1 ) of the fluid delivery probe 30 . as schematically shown in fig3 a and 6a for example , the outlets 33 , 330 of the fluid delivery probes 30 , 300 , respectively , are disposed to expel into the environment , cementitious fluid and any air that exists in the filler tube 20 and fluid delivery probe 30 , 300 . in further accordance with an embodiment of the method of the present invention , the fluid delivery probe can be connected to the head of the screw so as to form a high pressure seal between the fluid delivery probe and the head of the screw . as embodied herein and shown in fig3 a and 6a , a sealing o - ring gasket 34 , 340 desirably is disposed against a shoulder formed in the exterior surface of the fluid delivery probe 30 , 300 and near the distal end 30 b , 300 b thereof where the channel 31 , 310 terminates in the outlet 33 , 330 of the fluid delivery probe 30 , 300 . as schematically shown in fig2 and 3a , once the distal end 30 b of the fluid delivery probe 30 is inserted into the distal end 41 c of the head 41 of the screw , the o - ring 34 , which is shown partially cut away in fig2 , is disposed at the entrance 42 a of the cannula 44 in the head 41 of the screw 40 . then in the embodiment shown in fig2 and 3a , a nut 50 is threaded onto the threaded exterior surface of the proximal end 40 a of the head 41 of the screw 40 . as the nut 50 is advanced in the direction toward the distal end 40 b of the screw 40 , then the two opposed arms 48 a , 48 b of the head 41 of the screw 40 are pressed toward one another thereby locking the ribs 32 a , 32 b that extend radially from the exterior surface of the fluid delivery probe 30 into the recesses 49 a , 49 b in the arms 48 a , 48 b of the head 41 . the recesses 49 a , 49 b and ribs 32 a , 32 b are desirably disposed so that when the ribs 32 a , 32 b are locked into the recesses 49 a , 49 b , then the distal end 30 b of the fluid delivery probe 30 and the distal end 41 c of the head 41 of the screw 40 are sealed together via the o - ring 34 so that the cementitious fluid flows from the outlet 33 of the channel 31 of the fluid delivery probe 30 into the entrance 42 a of the cannula 44 in the screw 40 rather than escaping out of the head 41 of the screw 40 and into the environment surrounding the head 41 of the screw 40 . this arrangement ensures against escape of the cementitious fluid where the fluid delivery probe 30 is connected to the head 41 of the screw 40 and the outlet 33 of the channel 31 of the fluid delivery probe 30 is joined to the entrance 42 a of the cannula 44 in the screw 40 . alternatively , in the embodiment shown in fig6 a and 6b , a nut 500 having threads on its exterior surface , is threaded through an axially extending , threaded opening formed in the cap 511 of the head 510 of the screw 400 . as the nut 500 is advanced in the direction toward the distal end 400 b of the screw 400 , then the forward end 500 a of the nut 500 is pressed against the back 300 c of the elbow of the fluid delivery probe 300 thereby locking the fluid delivery probe 300 against movement in the axial direction away from the distal end 400 b of the screw 400 . the externally threaded nut 500 and the cap are desirably configured and disposed so that when the forward end 500 a of the nut 500 is contacting the back 300 c of the elbow of the fluid delivery probe 300 , then the distal end 300 b of the fluid delivery probe 300 and the distal end 510 b of the head 510 of the screw 400 are sealed together via the o - ring 340 so that the cementitious fluid flows from the outlet 330 of the channel 310 of the fluid delivery probe 300 into the entrance 420 a of the cannula 44 in the screw 400 rather than escaping out of the head 510 of the screw 400 and into the environment surrounding the head 510 of the screw 400 . this arrangement ensures against escape of the cementitious fluid where the fluid delivery probe 300 is connected to the head 510 of the screw 400 and the outlet 330 of the channel 310 of the fluid delivery probe 300 is joined to the entrance 420 a of the cannula 44 in the screw 400 . the fluid insertion device 10 can be provided by a screw extruder mechanism that is capable of generating pressures within the screw as high as 4 , 000 pounds per square inch . however , somewhat lower pressures generated in the screw of the present invention can be used , depending upon the viscosity of the flowable fluid that is being used and the configuration of the fluid discharge openings 45 in the distal portion of the pedicle screw . an example of a suitable fluid insertion device is described in u . s . pat . no . 6 , 783 , 515 , which is hereby incorporated herein in its entirety by this reference , and another example of a suitable fluid insertion device is available from discotech medical technologies ltd ., of herzeliya , israel . the fluid insertion device desirably can be provided with a reservoir full of a flowable , cementitious fluid that is capable of setting to a hardened condition . in accordance with an embodiment of the present invention , the cementitious fluid 62 can be chosen so that it does not begin setting up until about at least ten minutes after it is introduced into the vertebral body . cementitious fluid 62 suitable for this purpose includes high viscosity , acrylic cement such as polymethyl methacrylate ( pmma ) that is paste - like in consistency yet can be introduced through the bore that is defined by the cannula 44 . the chosen fluid 62 desirably has a consistency and viscosity that resembles the viscosity of a clay or playdoh brand molding material . whether this flowable fluid includes calcium phosphate or ceramics or an highly viscous bone cement , it will be characterized by a high viscosity that resists travel from the anchoring site for the screw and further dispersion throughout the body of the patient . cementitious fluid 62 suitable for this purpose is available under the trade name hi - visco flow and can be obtained from discotech medical technologies ltd . of herzeliya , israel . in further accordance with an embodiment of the method of the present invention , the fluid insertion device can be operated to discharge fluid from the discharge channel of the screw and into the vertebral body . as schematically shown by the arrows 21 a , 21 b , 21 c in fig1 for example , the fluid insertion device 10 can be operated to pump under pressure , cementitious fluid 62 from a reservoir 11 and through the filler tube 20 . as schematically indicated by the arrow 21 e , the fluid is pumped into and out of the outlet of the channel of the fluid delivery probe 30 . upon leaving the channel of the fluid delivery probe 30 , the cementitious fluid travels under pressure through the entrance 42 b of the cannula and through the length of the cannula 44 as indicated by the arrow 21 f . upon reaching the discharge opening 45 that is defined in the distal portion of the screw 40 , the fluid 62 exits the screw 40 and enters the vertebral body 60 as schematically indicated by the curved arrows . during operation of the fluid insertion device 10 , the surgeon can monitor the discharge of the cementitious fluid 62 into the vertebral body 60 by use of a fluoroscope or other means of visual observation . in accordance with an embodiment of the present invention , once the cementitious fluid 62 fills the vertebral body 60 to the surgeon &# 39 ; s desired extent , then the surgeon or other personnel discontinues operation of the fluid insertion device 10 , and thereafter the fluid delivery probe 30 is detached from the screw 40 . the detachment of the fluid delivery probe 30 can proceed in reverse order of the manner of attachment described above . a cap can be inserted into the fill cavity 42 a and sealed therein by the cementitious fluid , and excess fluid removed . in accordance with an embodiment of the present invention , once the fluid delivery probe has been detached from the screw , support rods then can be attached to the screw , either with or without there having been a cap inserted into the fill cavity 42 a . as shown in fig5 for example , each of a plurality of screws 40 is connected to a steel rod 70 and thus is connected to each other . the steel rod 70 is held in place against the head 41 of each screw 40 by a respective nut 50 . as schematically shown in fig5 , the proximal ends of the arms 48 a , 48 b of the head 41 of each screw 40 desirably can be broken off along a line of weakness 52 a , 52 b that is defined transversely across each of the arms 48 a , 48 b . moreover , the invention contemplates both percutaneous and non - percutaneous , i . e ., open , embodiments of the apparatus and method . the percutaneous embodiment now will be described with reference to fig7 . according to a percutaneous embodiment of the method of present invention , an incision permits insertion of a metal probe , and a hole is made through the pedicle of a vertebra in which it is desired to insert a screw 40 . the proximal end 72 a of a thin guide wire 72 such as shown in fig7 can be held by the surgeon and the distal end 72 b is threaded through the incision and into the hole in the pedicle . a cannulated pedicle screw 40 that is configured according to a percutaneous embodiment of the present invention can be guided by the surgeon into the hole via the guide wire 72 by threading the guide wire 72 through the cannula 44 that is formed axially through the screw 40 . once the tip 43 of the screw 40 is seated in the hole in the pedicle , the head 41 of the screw 40 will protrude through the incision and reside outside the patient &# 39 ; s body . the guide wire 72 then can be removed . a conventional tool can be used to rotate the screw 40 , which desirably is self - tapping , into the pedicle while a fluoroscope or similar device can be used to determine when the screw 40 has passed through the pedicle and is desirably located in the vertebral body 60 as shown in fig1 . if end opening 43 a at the tip 43 of the cannula 44 in the screw 40 should be sealed before introducing the cementitious fluid 62 , then a sealing ball 46 is introduced into the cannula 44 of the screw 44 to seal the end opening 43 a in the tip 43 of the screw 40 . the proximal end of the feeder tube 20 is connected to the fluid insertion device such as a cement pump . if the screw 40 has a threaded head as shown in fig7 , then the mating nut 50 is placed around the fluid delivery probe 30 . the distal end 20 b of the feeder tube 20 is connected to a connector 22 that has a body that defines a hollow conduit 22 a that extends axially through the connector 22 . the distal end of the body of the connector 22 can further define a threaded bore 20 c that is configured to be threaded to a threaded projection 30 c that can be formed at the proximal end 30 a of the fluid delivery probe 30 . the connector 22 desirably has a pair of opposed wings 23 a , 23 b radially extending from the body of the connector 22 and configured to facilitate manually connecting the filler tube 20 to the fluid delivery probe 30 . the cement pump then can be operated to fill the feeder tube 20 with the cementitious fluid 62 until the fluid forces all of the air out the filler tube 20 and out of the fluid delivery probe 30 that is mounted to the distal end 20 b of the filler tube 20 . the distal end 30 b of the fluid delivery probe 30 carries an o - ring 34 and becomes seated in the fill cavity 42 a in the head of the screw 40 . the connector 22 of the feeder tube 20 can be manipulated via a pair of opposed wings 23 thereon until the o - ring 34 is compressed and the fluid delivery probe 30 is snugly seated into the fill cavity 42 a in the head 41 of the screw 40 . if the screw 40 has a threaded head 41 as shown in fig7 , then the mating nut 50 is threaded over the arms 48 a , 48 b of the proximal end of the screw 40 . as the nut 50 is advanced , the recesses 49 a , 49 b in the arms 48 a , 48 b close in around the annular rib 32 formed in the distal end of the fluid delivery probe 30 and hold the fluid delivery probe 30 snugly in the fill cavity 42 a in the head 41 of the screw 40 to effect a pressure tight seal between the fluid delivery probe 30 and the fill cavity 42 a in the head of the screw 40 . before operating the fluid insertion device to insert the cementitious fluid 62 into the vertebral body 60 , the surgeon views the real time x - ray of the position of the distal end of the screw relative to the vertebral body to determine whether the fluid discharge opening 45 in the distal end of the screw 40 is desirably positioned for discharging the cementitious fluid 62 . the various components such as the screws 40 , 400 , nuts 50 , 500 , rods 70 , caps 511 and screw heads 510 desirably can be made of structurally hard materials such as metals like stainless steel or titanium or ceramic or hard plastics such as polyetheretherketone ( aka peek ), provided the materials can be given or inherently have , radiographic markers . while at least one presently preferred embodiment of the invention has been described using specific terms , such description is for illustrative purposes only , and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims . for example , the cementitious material enables the screws to be inserted directly into the vertebral body without going through the pedicle . such a method would allow for anterior or lateral placement of the screws on the vertebral body and be anchored by the injected material .
an improved method and apparatus for anchoring bone screws into bones of living beings includes a cannulated screw or bone anchor that is provided with at least one discharge opening in the distal end thereof . the head of the screw is configured to receive therein a material delivery probe in sealing relationship therewith . a fluid insertion device is connected to the material delivery probe and pumps a highly viscous material through the material delivery probe and into the interior of a bone in which the distal end of the screw has been inserted . the screw can be anchored proximally in bone to prevent backpressure from dislodging the delivery cannula and aides in achieving the high pressures necessary to cause the positive effects of materials previously not injectable in the bone or surrounding areas with the current methods and apparatia .