referring to fig1 a - d the above described problem can be solved in the cervical , thoracic and lumbar spine by insertion into the denuded intervertebral disc space an expansile bi - directional fixating transvertebral ( bdft ) screw 100 or screws . fig1 a and 1b illustrate three - dimensional views of the screw 100 in closed and opened positions , respectively , upon its insertion into the intervertebral disc space . the screw 100 is self - drilling . the mechanism of its action entails the turning of a midline drive screw 100 / pinion 104 in a clock - wise direction . this motion is bi - directionally translated via an interposing gear mechanism 105 enabling the simultaneous outward movement of left and right handed screws 102 , 103 in equal and opposite directions . when the drive screw 101 and its accompanying drive screw shaft are turned clock - wise , the driving pinion 104 is likewise rotated . this motion is then translated to the driven gear 105 which is interposed between the drive screw 101 and two opposing self - drilling screws 102 , 103 , one left - handed and the other right - handed . the gear ring 110 has screw coupling slots ( fig1 c and 1d ). there are also symmetric keyways 120 and an alignment cylinder 113 . the left handed screw 102 fits into one half of the slots 114 , 115 and the right handed screw 103 into the other half of the slots . this is clearly illustrated in cross sections of the screw and gear in fig1 c and 1d , respectively . fig1 a - c also illustrate the external casing 111 of the device which contains the external screw threads 117 , 118 , against which the left and right handed internal threads interact 116 , 119 with . the casing includes an upper left casing 111 b and an upper right casing 111 a . below the upper casing 111 b there is a surface serration pattern 118 which is part of a retaining outer shell 112 . fig2 a - g illustrate embodiment ii of the bdft 200 . this design differs in two fundamental ways from embodiment i . firstly the driving pinion 201 accomplishes bi - directional movement by engaging left and right gears 204 , 205 which simultaneously turn left and right screws 202 , 203 ( fig2 c - g ). secondly , in it &# 39 ; s resting closed position the solid left screw 202 with a narrower diameter is buried within the right wider diameter hollow right screw 203 . this mechanism allows for greater length of screw expansion compared to embodiment i . maintaining alignment of screws 202 , 203 and pinions 201 is accomplished by upper casings 211 , outer shells 212 , and left and right screw caps 209 a , 209 b ( fig2 a - g ). fig3 a - e illustrate embodiment iii of the bdft 300 . this is similar to embodiment ii . the major difference is the use of two separate driving screws pinions 301 a , 301 b for the two separate gears 304 , 305 . there is one pinion 301 a for the left screw 302 and another pinion 301 b for the right screw 303 . the left screw 302 engages the left gear 304 which engages the left screw 302 . the right pinion 301 a engages the right gear 305 which engages the right screw 303 . because the left and right screws 302 , 303 have separate controls and are not linked by one common pinion , separate distinct motions of the screws 302 , 303 can be obtained , as opposed to equal and simultaneous screw movements of embodiments i and ii . like embodiment ii , embodiment iii consists of a smaller diameter solid left screw 302 which fits into a larger diameter hollow right screw 303 . this can achieve significant screw extension length as in embodiment ii . fig4 a and 4b illustrates the placement of a single btfd 1000 screw anteriorly into the intervertebral space between adjacent lumbar vertebrae 400 . fig4 a illustrates the closed position . fig4 b illustrates the opened position . the illustrations are of a generic bdft screw 1000 i . e . it applies to embodiments i - iii . placement of a single bdft anterior to an intervertbral spacer may be sufficient to prevent interspacer / device extrusion , and enhance spinal stability . fig4 c illustrates the placement of three btfd screws 1000 in a triangulating manner covering anterior and middle columns . the presence of three screws so situated would prevent subsidence of the screws 1000 . hence they act as a very open ibfd 1000 . bone material in the form of dbx or bmp etc . could be inserted into the intervertebral space in between the three screws 1000 . this construct could be used as a supplemental or stand alone - intervertebral fusion device . also illustrated is a cross - section of a vertebral endplate 401 demonstrating the triangular placement of screws 1000 engaging anterior and middle columns . fig5 a illustrates the zero - profile horizontal linear mini - plate 500 . note the slots for placement of the bdft screws 1000 . on the anterior surface are slots 504 for the driving pinion screws . fig5 b illustrates that the plate 500 consists of upper and lower portions 500 a , 500 b which articulate with each other via interdigitation of alignment pins 502 and recesses 503 . fig5 c illustrates the integration of the bdft screws 1000 into the mini - plate 500 . fig5 d illustrates the placement of the plate - bdft construct into the intervertebral space . after the construct is placed into the intervertebral space , the screws 1000 are expanded bi - directionally in order to engage the vertebral bodies 400 . this construct can be surgically placed via anterior or posterior approaches . fig6 a - g illustrate a zero - profile triangular mini - plate 600 . in this embodiment the plate encompasses all three triangularly situated bdft screws 1000 . the posteriorly placed bdft screw 1000 is expanded with a centrally placed drive screw / pinion with a long stem which extends posteriorly . as illustrated in fig6 h and 6i this embodiment 600 ′ could be made hollow to accommodate the packing of bone material and can actually function as a combined three - in - one fusion cage / plate / bdft screw construct . note that this plate embodiment 600 ′ also has upper and lower components similar to 600 a , 600 b ( fig6 a - c ). preferably , plates 600 ′ a and 600 ′ b , however , include slots 610 for placement of bone material . fig6 d - f illustrate the incorporation of the bdft screws 1000 into the triangular mini - plate 600 . fig6 g illustrates the positioning of the triangular mini - plate 600 with incorporated expanded screws 1000 into adjacent vertebral bodies 400 . fig7 a and 7b illustrate a boomerang shaped thoracolumbar ibfd 700 with ratchetable titanium or peek shells 710 , 711 which can expand geometrically in two dimensions . fig7 a illustrates the bdft screws 701 , 702 , 703 in partially expanded position . fig7 b illustrates the bdft screws 701 , 702 , 703 in fully expanded position . the outer shells 710 , 711 themselves when ratcheted width - wise have titanium or peek spikes 713 inserting themselves into and purchasing the endplates 401 , thus securing permanent integration into the vertebral endplates 401 . the outer shell 710 , 711 surfaces can be treated with hydroxyappetite to facilitate bone incorporation . these shells are fully described in our previous pct patent application pct / us2005 / 016493 , filed may 11 , 2005 . the ibfd device 700 has four shells and a plurality of spikes 713 . the height can be modified by adjusting four fixed height screws 712 . sequential turning of these screws 712 leads to height expansion between the rostral and caudal shells 710 , 711 by widening the distance between their superior and inferior shells 710 a , 710 b . once the ibfd 700 is properly positioned in the interspace the spikes 713 engage and purchase the vertebral endplates 401 . the three incorporated bdft screws 701 , 702 , 703 are turned clockwise leading to anterior and middle column engagement of the vertebral bodies 400 above and below the disc space . the bdft screws 701 , 702 , 703 are strategically placed ; one on each side of the superior shell 710 a and one centrally on the inferior shell 710 b . this captures anterior and middle columns of the vertebral column increasing spinal stability . after the bdft screws 701 , 702 , 703 are successfully purchased within the vertebral bodies 400 , bone fusion substances are placed / packed or poured , into the inner aspects of the device 700 and its surrounding intervertebral space . an alternative thoracolumbar ibfd embodiment not illustrated expands in two dimensions and has the additional feature of an incorporated expansile porous elastometric sheath molded to the inner aspects of the titanium shells . within the balloon is a port with or without an attached microsilastic catheter through which bone fusion material can be injected . supplemental bone fusion material can be added to the surrounding area of the device to further enhance fusion . furthermore for certain patients where applicable , a rapid fusion can be effected by the instillation of methyl - methacrylate a similar embodiment for a cervical ibfd is based on our previously described two - dimensional cervical expansion device in pct patent application pct / us2005 / 016493 , filed may 11 , 2005 . the engagement of the ibfd shell spikes 713 and the bdft screws 701 , 702 , 703 into the vertebral bodies 400 above and below the device would obviate the need for any kind of anterior plating system . fig8 a - n illustrate a calibrated facet joint stapler 800 which can be used to staple the thoracolumbar inferior and superior articulating facets with incremental torquedegrees . incrementally increasing the degrees of calibration modulates the extent of facet joint flexibility . this can be used as an option to provide posterior column support and can be used in an open , or percutaneous , endoscopic or fluoroscopic approach . depending on the operative approach and the individual patient , facet stapling can be performed unilaterally or bilaterally . fig8 a illustrates an exploded view of the joint stapler 800 and its components . fig8 b and 8c illustrate the stapler 800 in an open position . fig8 d and 8e illustrate the stapling device 800 and staples 803 a , 803 b in a closed position . fig8 f and 8g illustrate the stapling device 800 and staples 803 a , 803 b in a closed , staple released , position . the stapling device 800 includes two orthogonally placed levers 801 a , 801 b which open and close over a triangular fulcrum 810 . fig8 h - j illustrate an exploded view of the components of the lever 801 a , 801 b . fig8 k and 8l illustrate details of the cartridge 802 a , 802 b . fig8 m and 8 n illustrate a transparent view of details of the triangular fulcrum 810 . as shown in fig8 a - 8j , each lever 801 a , 801 b includes a grip handle 815 , an arm 816 , a rounded wedge or cam 817 , and a fulcrum screw hole 818 . the levers 801 a , 801 b are rotatably coupled to the triangular fulcrum 810 by a fulcrum screw 812 ( shown in fig8 a ), which is inserted in the fulcrum screw hole 818 . also illustrated are spring anchors 814 . fig8 m and 8n illustrate the details of the triangular fulcrum 810 , which is formed by portions 810 a , 810 b . the triangular fulcrum 810 includes mating alignments , which include fastener pins 832 on one portion 810 a of the triangular fulcrum 810 and fastener openings 833 on the other portion 810 b of the triangular fulcrum 810 . the triangular fulcrum 810 includes an opening 831 for receiving the fulcrum screw 812 ( shown in fig8 a ) that rotatably couples the levers 801 a , 801 b to the triangular fulcrum 810 . the triangular fulcrum 810 includes right and left linear guides or slots 809 a , 809 b that guide the sliding elements or followers 825 of the left and right staple cartridges 802 b , 802 b . most importantly , the triangular fulcrum 810 includes four incremental calibration slots 830 for incremental degrees of facet joint stapling . as shown in fig8 k and 8l , the cartridges 802 a , 802 b each include a cartridge portion 823 having a staple slot 824 that holds a titanium staple 803 a , 803 b . the cartridges 802 a , 802 b each include a sliding element or follower 825 that is guided by the right and left linear guides or slots 809 a , 809 b of the triangular fulcrum 810 . the cartridges 802 a , 802 b each include a lever - cartridge pin slot 822 . the cartridges 802 a , 802 b each include a semi - elliptic cam or cam surface that cooperates with a portion of the first lever arm 801 a or the second lever arm 801 b , respectively . as shown in fig8 b - 8f , the rounded wedges or cams 817 of the levers 801 a , 801 b engage the left and right staple cartridges 802 a , 802 b . as shown in fig8 b and 8f , the levers 801 a , 801 b are moved together about the fulcrum screw 812 such that the rounded wedges or cams 817 of the levers 801 a , 801 b engage the left and right staple cartridges 802 a , 802 b and push the left and right staple cartridges 802 a , 802 b linearly together . the sliding elements or followers 825 of the left and right staple cartridges 802 b , 802 b are guided linearly by the right and left linear guides or slots 809 a , 809 b of the triangular fulcrum 810 . in this manner , the portions of the titanium staple 803 a , 803 b , which are held by the staple slot 824 of the left and right staple cartridges 802 a , 802 b are stapled together , as shown in fig8 f and 8g . fig8 o and 8p illustrate frontal and perspective views , respectively of the two opposing titanium facet staples 803 a , 803 b . each staple 803 a , 803 b consists of a bracket 836 , a nail 837 and an alignment pin 835 . illustrated are four sequential calibrated tightening positions of the opposing staples 803 a , 803 b . increasing the calibrated opposition of the two staples 803 a , 803 b leads to increasing opposition of the facet joints and hence increasing rigidity , and decreasing flexibility . each staple 803 a , 803 b has two alignment recesses 838 . the opposition of these staples 803 a , 803 b around the facet joint forms a rectangular facet joint enclosure . fig8 q and 8r illustrate the stapled inferior and superior articulating facets 851 , 852 . fig8 r illustrates the application of the facet stapler 800 on the facets 851 , 852 introducing the facet staple 803 . the facet staple is used to join the exterior articulating facet 851 and the interior articulating facet 852 . the surgical steps necessary to practice the present invention will now be described . the posterior lumbar spine implantation of the bdft screws 1000 , plate and ibfd can be implanted via a previously described posterior lumbar interbody fusion procedure ( plif ) or posterior transforaminal lumbar interbody fusion procedure ( tlif ). the procedure can be performed open , microscopic , closed , tubular or endoscopic . fluoroscopic guidance can be used with any of these procedures . after the adequate induction of anesthesia , the patient is placed in the prone position . a midline incision is made for a plif , and one or two parallel paramedian incisions or a midline incision is made for a tlif . for the plif a unilateral or bilateral facet sparing hemi - laminotomy is created to introduce the bdft screws 1000 , plates or ibfd into the disc space after it is adequately prepared . for the tlif procedure , after a unilateral dissection and drilling of the inferior articulating surface and the medial superior articulating facet , the far lateral disc space is entered and a circumferential discectomy is performed . the disc space is prepared and the endplates exposed . there are then multiple embodiments to choose from for an intervertebral body fusion . with the first and simplest choice , under direct or endoscopic guidance one bdft screw 1000 or three bdft screws 1000 can be placed in a triangulating manner encompassing the anterior and middle vertebral columns ( fig4 a - c ). the screws 1000 are then maximally expanded purchasing and uniting the vertebral bodies above and below the disc space . bone material or an alternative intervertebral fusion device can then be packed into the disc space . the casing of the screws 1000 prevents subsidence of the vertebral bodies . an additional option in the posterior lumbar spine is to place a mini - plate dorsally underneath the thecal sac to prevent bone migration into the nerves . in addition via a tlif approach a triangular mini - plate / cage construct can be inserted , and then the bdft screws 1000 maximally expanded . this is a very simple and practical supplemental or stand - alone intervertebral fusion device . using an alternative ibfd option , utilizing specialized forceps the two - dimensional expanding thoracolumbar expandable ibfd 700 ( fig7 a and 7b ) is introduced into the disc space . the final dimension expansion in all embodiments leads to purchasing of the spikes into the vertebral endplates . the bdft screws 1000 are then driven directly into rostral and caudal vertebral bodies across the intervertebral space . then bone fusion material ; autologous , allograft , bone matrix protein , bmp , rh - bmp , paste or other similar currently available or specially designed osteoconductive substances can be placed into the device and the surrounding intervertebral space . in embodiments with an incorporated viscoelastic balloon sheath , prior to engaging the screws the expandable elastometric sheath / balloon is filled with bone fusion material as mentioned above . if desirable , further material , can be placed outside its confines within the intervertebral space . if further posterior column stability or rigidity is required , unilateral or bilateral , single level or multiple level facet screw stapling can be performed under open , microscopic fluoroscopic or endoscopic vision . radiographic confirmation of staple position is obtained . calibrated stapling leads to opposition of the facet joints with incremental degrees of joint opposition . this can lead to variable degrees of posterior column rigidity and / or flexibility . the anterior lumbar spine implantation of solitary bdft screw ( s ) 1000 , bdft screws incorporated into a horizontal linear or triangular mini - plate , or the ibfd / bdft screw embodiment for l 4 / 5 and l 5 / s 1 interspaces can be performed on the supine anesthetized patient via previously described open micropscopic or endoscopic techniques . once the disc space is exposed and discectomy and space preparation is performed , placement of one , two or three bdft screws 1000 with or without a ventral mini - plate , or placement of two dimensionally expanding ibfd with or without expansile elastometric sheaths and their incorporation is identical to that performed for the posterior approach . the posterior placement of the bdft screws 1000 alone or combined with mini - plates or with ibfd embodiments into the thoracic spine can be performed via previously described transpedicular approaches ; open or endoscopic . the anterior placement of the ibfd 700 into the thoracic spine can be accomplished via a trans - thoracic approach . once disc space exposure is obtained via either approach , all of the above mentioned embodiments can be inserted . engagement of the devices is identical to what was mentioned above . for anterior placement of the cervical embodiments of the bdft screw ( s ) 1000 with or without the horizontal linear or triangular cervical mini - plate , and the ibfd embodiments the anterior spine is exposed in the anesthetized patient as previously described for anterior cervical discectomies . once the disc space is identified , discectomy is performed and the disc space prepared . implantation and engagement of all devices is identical to that described for the anterior lumbar and thoracic spines . the present invention may provide an effective and safe technique that overcomes the problems associated with current transpedicular - based thoracic and lumbar fusion technology , and with current vertical cervical plating technology , and for many degenerative stable and unstable spine diseases , and could replace many pedicle screw - based and anterior vertical - plate based instrumentation in many but not all degenerative spinal conditions . calibrated facet joint screw staples can facilitate flexible fusions and could replace current static trans - facet screws . to our knowledge there has not been any other previously described bi - directional screw for use in the spine , other joints , or for any commercial or carpentry application . the bi - directional screw 1000 described herein may indeed have applications in general commercial , industrial and carpentry industries . to our knowledge the description of zero to subzero profile anterior or posterior horizontal spinal plates which traverse the diameter of the disc space has not been previously described . to our knowledge an intervertebral three - in - one construct combining bone cage , plate and screws has not been previously reported . to our knowledge calibrated facet joint staples 803 a , 803 b have not been previously described .
an apparatus and method for joining members together using a self - drilling screw apparatus or stapling apparatus are disclosed . the screw apparatus includes a shell and first and second first screw members having tapered ends and threaded bodies that are disposed within the shell . a drive mechanism rotatably drives the first and second screw members from the shell in opposite directions and causes the screw members to embed themselves in the members to be joined . the screw apparatus can be used to join members such as bones , portions of the spinal column , vertebral bodies , wood , building materials , metals , masonry , or plastics . the stapling apparatus includes first and second lever arms rotatably joined together at a fulcrum , and the lever arms rotate in opposite directions . first and second cartridges are disposed at the ends of the lever arms . each cartridge is capable of holding a staple including a bracket , a nail member and an alignment slot . when the ends of the lever arms are rotated towards each other the staples from the cartridges are interlocked . the staples can be also be used to join members such as bones , portions of the spinal column , or vertebral bodies .