Abstract:
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.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application hereby claims priority to pending U.S. Provisional Application Ser. No. 60/799,472 filed May 11, 2006. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    N/A 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention pertains to method and apparatus for anchoring bone screws into bones of living beings and injecting under high pressure materials that are high in viscosity. 
         [0004]    One technique for inserting and anchoring bone screws relies on use of an expandable device that is inserted into a starter cavity produced by sharp mechanical means, which may include a drill, operating the expandable device to expand the size of the cavity, operating the expandable device to allow the device to contract, withdrawing the device from the expanded cavity, pumping some quick hardening, less viscous cement into the expanded cavity, inserting the desired screw into the cement-filled cavity, and removing the excess cement, if any, that is displaced by the insertion of the screw. This technique has been used in connection with screws that are inserted into the pedicle of the vertebra. 
         [0005]    Because of the need to create the cavity to receive the cement, this procedure involves time and expense to create the cavity for the screw and cement. The use of a less viscous cement increases the risk that the cement will extravasate and leak into areas where it would cause harm to the patient. 
       OBJECTS AND SUMMARY OF THE INVENTION 
       [0006]    Many new biologic and non-biologic materials are being developed for use in and around areas of bone that are using highly viscous materials. These materials are highly viscous because of their chemical composition or from the use of viscous carriers to deliver biologic materials to sites on or around bone. The areas of current use and need are on the articular surfaces of bone, in the intervertebral spaces, vertebral bodies and bones in general. Additionally new highly viscous cements and new techniques of vertebral body augmentation using this viscous cement have been described which make this described apparatus and method safe and effective for anchoring bone screws as it augments vertebral bodies or other bony structures. 
         [0007]    It is a principal object of the present invention to provide an improved method and apparatus for anchoring bone screws into bones of living beings by means of an apparatus that is capable of using high pressures needed to inject the newer high viscous materials. This same method and apparatus also can be used to inject in areas surrounding bone, materials that are not ordinarily fluid under low pressures. Such materials include the biologics for nucleus replacement or repair and use of nonbiologics for the same purposes. 
         [0008]    It is a further principal object of the present invention to provide method and apparatus for anchoring bone screws into bones of living beings involving less time and expense than conventional methods and apparatus. 
         [0009]    It is another principal object of the present invention to provide an improved method and apparatus for introducing highly viscous material into the interior of a vertebral body in which it is desired to insert a screw. 
         [0010]    It is yet a further principal object of the present invention to provide method and apparatus for introducing highly viscous material into the vertebral body contemporaneously with insertion of the bone screw into the vertebra. 
         [0011]    It is a still further principal object of the present invention to provide a method and apparatus for anchoring bone screws into bones of living beings wherein a highly viscous material is introduced into the bone at pressures within the vertebral body that are lower than in conventional methods and apparatus by using ultra high pressures to introduce slow creeping materials. 
         [0012]    It is yet another principal object of the present invention to provide method and apparatus for introducing highly viscous material into the gaps that have formed due to the loosening of prosthetic implants in the cortical bone of the hip, knee or shoulder. 
         [0013]    Additional objects and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
         [0014]    To achieve the objects and in accordance with one or more of the purposes of the invention, as embodied and broadly described herein, an embodiment of the apparatus of the present invention can include a high pressure material insertion device, a hollow feeder tube having a proximal end that is selectively connectable and disconnectable to the high pressure material insertion device, a material delivery probe having a proximal end that can be detachably connected to the distal end of the feeder tube, and a cannulated pedicle screw that is provided with one or more fluid discharge openings through a distal portion thereof. The screw threads are necessary to achieve connection with the cortical cancellous bone in the pedicle which provides firm anchorage necessary when using high pressures in the delivery system. The distal end of the material delivery probe desirably can be selectively detachable and attachable in a high pressure, sealing engagement to the proximal end of the screw, which can have either an uniaxial head or a polyaxial head. 
         [0015]    In one embodiment of the pedicle screw of the present invention, several fluid discharge orifices are provided by a plurality of holes that are extending transversely from the cannula and through the body of the screw in the distal portion of the screw. In another embodiment of the pedicle screw according to the present invention, only one set of aligned holes are provided along one axial section of the distal portion of the screw. In still another embodiment of the pedicle screw according to the present invention, a single fluid discharge opening is provided by an elongated slot that extends axially along the length of the distal portion of the screw as well as transversely from the exterior of the screw into the cannula in the central portion of the screw. In a further embodiment of the pedicle screw according to the present invention, one or more of the fluid discharge holes is/are angled with respect to both the axial and transverse directions of the screw. The angles can be such as to direct the discharging fluid back toward the head of the screw or toward the tip of the screw. 
         [0016]    The fluid insertion device, such as a cement pump, desirably is provided with a reservoir full of cementitious fluid. The flowable but viscous cementitious fluid desirably should be capable of setting to a hardened condition in no less than about ten minutes. The chosen cementitious fluid desirably has a consistency and ultra high viscosity resembling 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 vertebral body. 
         [0017]    Before the fluid delivery probe is connected in high pressure sealing engagement to the head of the screw, the material insertion device can be operated to fill the feeder tube with the cementitious material or fluid, until the fluid forces all of the air out the filler tube and out of the material delivery probe that can be mounted to the distal end of the filler tube. Before operating the fluid insertion device to pump cementitious fluid into the vertebral body, the surgeon desirably 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 openings in the distal end of the screw are desirably positioned for discharging the cementitious fluid. 
         [0018]    Moreover, the invention contemplates both percutaneous and non-percutaneous, i.e., open, embodiments of the apparatus and method. 
         [0019]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate at least one presently preferred embodiment of the invention as well as some alternative embodiments. These drawings, together with the description, serve to explain the principles of the invention but by no means are intended to be exhaustive of all of the possible manifestations of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is an elevated perspective view of an embodiment of the present invention shown in use with elements depicted schematically and with portions of the anatomy removed in order to reveal features of the present invention. 
           [0021]      FIG. 2  is a front plan view of components of the embodiment shown in  FIG. 1  with dashed lines indicating structure that ordinarily would not be visible in the view shown in  FIG. 2  due to the opacity of various structures. 
           [0022]      FIG. 3A  schematically represents an assembly view of components of the embodiment shown in  FIG. 2  but with portions cut away and revealed in cross-section. 
           [0023]      FIG. 3B  illustrates an alternative embodiment of a component of the device of the present invention shown partially in cross-section. 
           [0024]      FIG. 3C  illustrates a further alternative embodiment of a component of the present invention with portions cut away and revealed in cross-section. 
           [0025]      FIG. 3D  is a cross-sectional view of a partial section of an alternative embodiment of a component of the present invention. 
           [0026]      FIG. 3E  is a cross-sectional view of a partial section of a further alternative embodiment of a component of the present invention. 
           [0027]      FIG. 4  is a view shown in partially in cross-section of the alternative embodiment in a fully assembled view as it would be configured after insertion into the anatomy and ready for dispensing the filling substance and with elements shown in phantom (chain-dashed lines). 
           [0028]      FIG. 5  is an elevated perspective view of an embodiment of the present invention shown in use with portions of the anatomy removed in order to features of the present invention. 
           [0029]      FIG. 6A  illustrates additional alternative embodiments of components of the present invention with portions cut away and revealed in cross-section. 
           [0030]      FIG. 6B  illustrates an assembled view of portions of the components illustrated in  FIG. 6A  with one of the elements rotated 90° from the view shown in  FIG. 6A . 
           [0031]      FIG. 7  is an elevated assembly, front plan view with dashed lines indicating structure that ordinarily would not be visible in the view shown in  FIG. 7  due to the opacity of various structures. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]    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. 
         [0033]    A presently preferred embodiment of the apparatus for and method of anchoring a pedicle screw into a vertebral body is shown in relation to  FIG. 1 . 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  FIG. 1 , 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  FIG. 3A , 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 . 
         [0034]    As schematically shown in  FIG. 1 , 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  FIG. 3A  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 . 
         [0035]    As shown in  FIG. 3A , 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 ( FIGS. 1 ,  2 ,  3 A,  3 B,  3 C,  5  and  7 ) or a polyaxial head ( FIGS. 4 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  FIG. 4 , 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 . 
         [0036]    As shown in  FIG. 3A  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  FIG. 2 , 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  FIG. 2  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   
         [0037]    As shown in  FIG. 2  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. 
         [0038]    As shown in a cross-sectional view in each of  FIGS. 3B ,  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  FIGS. 3B ,  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  FIGS. 3B 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  FIGS. 3B 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 . 
         [0039]    Alternatively, as shown in  FIG. 3C  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.    
         [0040]    Alternatively, as shown in  FIGS. 3E 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  FIGS. 3E 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. 
         [0041]    As shown in  FIGS. 3E 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  FIG. 3E , 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.    
         [0042]    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  FIG. 3E  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  FIG. 6A , an additional embodiment of the screw  400  desirably has more than one such bore  45   i ,  45   h.    
         [0043]    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. 
         [0044]    As shown in  FIGS. 3D 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. 
         [0045]    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  FIG. 1 , 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. 
         [0046]    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. 
         [0047]    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  FIG. 3A  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  FIG. 1 , the proximal end  20   a  of the filler tube  20  is connected to the fluid insertion device  10 . In the embodiment shown in  FIG. 3A , 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 . 
         [0048]    In the embodiment of  FIGS. 6A 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  FIG. 6A . In the embodiment shown in  FIGS. 6A 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  FIGS. 6A 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  FIG. 3A . 
         [0049]    As shown in  FIGS. 3A 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  FIG. 6A , 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). 
         [0050]    In the embodiment shown in  FIGS. 2 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 . 
         [0051]    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  FIG. 1  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  FIG. 1 ) of the fluid delivery probe  30 . As schematically shown in  FIGS. 3A 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 . 
         [0052]    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. 
         [0053]    As embodied herein and shown in  FIGS. 3A 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  FIGS. 2 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  FIG. 2 , 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  FIGS. 2 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 . 
         [0054]    Alternatively, in the embodiment shown in  FIGS. 6A 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 . 
         [0055]    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. 
         [0056]    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. 
         [0057]    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  FIG. 1  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. 
         [0058]    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. 
         [0059]    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  FIG. 5  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  FIG. 5 , 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.    
         [0060]    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  FIG. 7 . 
         [0061]    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  FIG. 7  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. 
         [0062]    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  FIG. 1 . 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 . 
         [0063]    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  FIG. 7 , 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 . 
         [0064]    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  FIG. 7 , 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 . 
         [0065]    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 . 
         [0066]    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. 
         [0067]    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.