illustrative embodiments of the invention are described below . in the interest of clarity , not all features of an actual implementation are described in this specification . it will of course be appreciated that in the development of any such actual embodiment , numerous implementation - specific decisions must be made to achieve the developers &# 39 ; specific goals , such as compliance with system - related and business - related constraints , which will vary from one implementation to another . moreover , it will be appreciated that such a development effort might be complex and time - consuming , but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure . the stackable vertebral body replacement , anterior and lateral inserter assemblies , distractor / sizer and methods for implantation disclosed herein boasts a variety of inventive features and components that warrant patent protection , both individually and in combination . fig1 - 13 illustrate an exemplary embodiment of a stackable vertebral body replacement 10 according to one embodiment of the present invention . the stackable vertebral body replacement 10 includes a center core section 11 and two endcaps 12 . the core section 11 and the two endcaps 12 are made from a biocompatible material . for example , the components may be machined from implantation - grade polyether ether ketone ( peek ). in one embodiment , six sides comprise the center core 11 . the following sides of the core are opposite each other and are identical : top 34 and bottom 35 , front 36 and back 37 , and left 38 and right 39 . the top 34 and bottom 35 sides of the core sections 11 have mating sections 13 , which allow the core 11 to couple to the mating sections 14 of the endcaps 12 . the core 11 is may vary in height from 10 mm to 80 mm . the core 11 is held in place between the two endcaps 12 by the stops 15 on front 36 and back 37 of the core 11 which lock into the locking assembly 16 on the back of the endcap 12 . a guide 33 , helps position the core 11 into the mating sections 14 on the endcaps 12 during insertion . additionally , a protrusion 17 on the mating section 13 increases the friction between the core 11 and endcaps 12 holding the assembly together . the top of the core 11 has holes 18 extending longitudinally therethrough , in which radiopaque markers are placed to verify alignment during insertion . on top of the core 11 there are additional holes 19 which allow entry of the core insertion assembly pins 77 for lateral insertion . the side of the core 11 has holes 20 for attachment to the anterior inserter assembly 90 for anterior insertion . additional holes 21 in the side of the core 11 allow for insertion of additional radiopaque markers for verifying alignment during insertion . the endcaps 12 comprise a variable length base 22 and a variable height riser 23 . in one embodiment , the endcap base 22 is rectangular with front 133 , back 134 , left 135 , right 136 , top 137 , and bottom 138 sides . the endcaps 12 range in height from 7 mm to 25 mm . the endcap 12 is comprised of a cavity 24 through the piece which runs from the front 133 to the back 134 to allow for bone fusion through the vertebral body replacement . in one embodiment , in addition to the cavity 24 , the endcap base 22 has additional holes 25 which are cut through the base material at opposite ends of the base , also to promote bone fusion with the endcap 12 . on the top 137 and bottom 138 of the endcaps 12 are screw holes 26 to allow for connection to the endplate retaining rods 45 of the lateral inserter system 40 . additionally on top 137 and bottom 138 of the endcaps 12 are holes 27 for radiopaque markers for proper alignment during insertion and a hole 32 to promote bone fusion . the side of the implant has an additional hole 28 for a radiopaque marker and holes 29 to promote fusion . the front 133 of the endcap 12 has anti - migration elements 30 designed to grip the ends of the vertebrae after implantation in order to maintain its proper spinal alignment . additionally , there are a plurality of small holes 31 in the front 133 of the endcap 22 , partially through the base for the insertion of radiopaque markers which guide insertion and maintain implant position . fig1 - 26 illustrate the lateral inserter system 40 according to one embodiment of the present invention . this embodiment of the lateral inserter system is comprised of two slide retainers 41 , a core inserter 42 , two bracket assemblies 43 , and a clamp assembly 44 . the slide retainers 41 are constructed of a biocompatible material , such as stainless steel and are positioned on either side of the core inserter 42 . endcap retaining rods 45 are slid into the in the top of the slide retainer 41 and travel the complete length of the slide retainer 41 . on the top of the endcap retaining rod 45 is a knurled knob 46 and the opposite end is a threaded end tip 47 . the threaded end tip 47 can be attached to the top of the endcap 12 in screw hole 26 . the front of the slide retainer 41 has a handgrip 48 to assist the surgeon in handling the device . below the handgrip 48 , on the front of the slide retainer 41 is a vertical height adjustment section 49 . this vertical height adjustment section 49 allows varying height adjustment of the bracket assembly 43 . on the inside of the slide retainer 41 is a mating section 50 which allows for coupling the core 11 onto the inside of the slide retainer 41 between the two endcaps 12 . the bracket assemblies 43 maintain position of the lateral inserter system 40 in the body during surgery . the vertical position of the bracket assembly 43 along the slide retainer 41 is adjustable in one embodiment by manually retracting the slide locks 51 by pulling the knobs 52 outward on the bracket assembly 43 . the bracket assembly 43 is positioned vertically along the slide retainer 41 as required and the knobs 52 are released when in the desired position . in one embodiment , the slide locks 51 are held extended in the locked position by the extension force of a spring 53 inside the bracket assembly 43 . here , the slide lock 51 is affixed to the knob 52 by a pin 54 inserted through a hole 55 in the knob and a hole 56 in the top of the slide lock 51 . the inside edges 57 of the bracket assembly 43 are curved to allow the bracket assembly 43 to move along the outside edges of the slide retainer 41 . the clamp assembly 44 allows for both measuring the space between vertebral bodies in the spine and maintaining the proper space between the slide retainers 41 during lateral insertion . the clamp assembly 44 is made of a biocompatible material , such as stainless steel . the upper arm 58 of the clamp assembly 44 is affixed to the slide retainer 41 by means such as a screw 59 and a retaining nut 60 . the lower arm 61 of the clamp assembly is attached to the opposite slide retainer 41 in similar fashion . the measurement bar 62 is mounted into the end of the upper arm 58 opposite the slide retainer 41 attachment point . the lower arm 61 travels along the measurement bar 62 with the opposite end affixed to the slide retainer mount 41 . the lower arm 61 is held in place by a locking device 68 which is attached to the lower arm 41 by the mounting pin 65 . a handle 63 is attached to a locking screw 64 inside the lower arm . turning the handle 63 engages and disengages the locking device 68 , restricting and allowing travel of the lower arm 41 along the measurement bar 62 which changes the distance between the slide retainers 41 . the core inserter 42 is made of biocompatible material , such as stainless steel . in one embodiment , the core inserter 42 comprises an outer container 66 , an inner rod 67 , a core distractor block 80 , a quick release 69 and a locking nut 70 . the inner rod 67 slides within the hollow outer container 66 and is attached at the upper end by release pins 71 which travel through holes in the inner rod and into slots 72 in the outer container which limit the travel of the rod . the quick - release 69 fits around and is attached to the outer container 66 by two lock pins 73 . the inside of the locking nut 70 is threaded and fits around the outer container 66 and screws onto the threaded area 74 on the outside of the container . a spring 75 fits around the outer container 66 between the quick - release 69 and the locking nut 70 . the spring 75 is compressed and the force on the spring is translated as a downward force on the inner rod 67 , keeping the arms 77 at the end of the core inserter 42 extended unless upward force is applied to the quick - release 69 counteracting spring 75 force . the lower end of the inner rod 67 is attached to the center pin 76 holding the core inserter arms 77 together . two pivot pins 78 allow the core inserter arms 77 to pivot around the center pin 76 , opening and closing the arms . with the core inserter arms 77 together , the outer container 66 slides into the distractor block 80 . the distractor block 80 is made of biocompatible material . for example , the components may be machined from implantation - grade polyether ether ketone ( peek ). the distractor block 80 is held onto the core inserter 42 , in one case , by two ball detents 78 on both sides of the core inserter 42 . the top 139 and bottom sides 139 of the distractor block 80 have a mating section with connectors 81 which are smaller than those of the center core 11 in order to take the downward load off the core 11 during distraction . the center of the distractor block 80 is hollow to allow the bottom of the outer container 66 to slide into and attach to the distractor block 80 . on the inside of the left 143 and right 144 sides of the distractor block 80 are recessed holes 83 where the ball detents 79 from the outer container 66 meet with and attach the distractor block 80 to the outer container 66 . pulling the distractor block 80 vertically down off the outer container 66 will release the ball detents 79 , allowing the distractor block 80 to be removed from the outer container 66 . fig2 - 32 illustrate the anterior inserter system 90 according to one embodiment of the present invention . the anterior inserter system 90 is comprised of a hollow outer container 91 a collet 92 , a lock 93 , a bracket assembly 94 , an inner shaft 95 and two bracket arms 96 which attach to the center core 11 . the anterior inserter system 90 is constructed from biocompatible material , such as stainless steel . the end of the bracket arms 96 are machined to enable them to affix to the core 11 by traveling through holes 20 on the core 11 and grasping the inside edge of the core material . both bracket arms 96 are connected to the end of the inner shaft 95 by means such as a center pin 97 . the bracket arms 96 are also connected to the bracket 94 by two pivot pins 98 . the bracket assembly 94 allows vertical movement of the inner shaft 95 , which pivots the bracket arms 96 around the pivot pins 98 causing the bracket arms 96 to open and close . the pivot pins travel through holes 99 on the bracket 94 which affix the bracket arms 96 to the bracket assembly 94 . at the opposite end of the anterior inserter system 90 from the bracket assembly 94 is the release assembly . the release assembly is comprised of the collet 92 , a lock 93 a spring 100 and two release pins 101 . the release pins 101 go through the top of the inner shaft 95 and through slots 102 in the outer container 91 . the release pins 101 ride in the slots 102 allowing for some limited , vertical movement of the inner shaft 95 within the outer container 91 . a spring 100 is placed on the inside of the outer container 91 at the end , between the end of the outer container 90 and the end of the inner shaft 95 allowing for tension being placed upon the inner shaft 95 . the force of the spring 100 causes downward force on the inner shaft 95 which causes the bracket arms 96 to pivot around the pivot pins 98 and the bracket arms 96 to spread out . the spread bracket arms 96 of the anterior inserter 90 affix the center core 11 to the anterior inserter 90 . upward force on the collet 92 , causes the inner shaft 95 to move upwards , causing the bracket arms 96 to move toward the center ( retract ), allowing the anterior inserter system 90 to be removed from the center core 11 after being property positioned in the body . the outer container 91 is travels through the hole in the center of the collet 92 and the collet 92 is affixed to the outer container 91 by the release pins 101 which travel through the collet 92 , the outer container 91 and inner shaft 95 . located just above the collet 92 on the outer container is a threaded area 103 . the inside of the lock 93 is threaded . the top of the outer container 91 is placed through the center of the lock 93 . the lock 93 is then screwed onto the outer container 91 onto the threaded area 103 until it meets the edge of the collet 92 . the lock 93 is used to maintain the collet 92 in the desired position during insertion of the vertebral body replacement . adjusting the position of the lock 93 on the threaded area 103 allows for movement in the collet 92 on the outer container 91 . fig3 - 37 illustrate the distractor / sizer 110 according to one embodiment of the present invention . the distractor / sizer 110 is constructed from a biocompatible material such as stainless steel and is comprised of lower arms 111 held together in the center of the arm by the lower center screw 112 . the top of the lower arms 111 are affixed to the bottom of the upper arms 113 by two screws 114 . the upper arms 113 pivot around the upper center screw 115 . the outer edges of the upper arms 113 are curved to form a handgrip 116 . a pair of flexible bars 117 are affixed between the upper arms 113 by mounting pins 118 . the flexible bars 117 hold the upper arms 113 apart and provide some resistance as the upper arms 113 are closed together . as the upper arms 113 are moved together ( closed ), the bottom end of the upper arms 113 move apart . this movement causes the upper end of the lower arms 111 to move apart and the bottom of the lower arms 111 with the endplates 119 to move apart , causing distraction . a measurement bar 120 is affixed to one end of the upper arms 113 by a mounting pin 121 . the other end of the measurement bar 120 travels through a hole 122 on the other upper arm 113 . a collar 123 is attached to the end of the measurement bar 120 by an endcap 124 affixed to the end of the measurement bar 120 . the endplates 125 are affixed by threaded screws 126 and caps 127 to endcap brackets 128 which have an attaching point 129 which affix the endcap brackets 128 to the bottom end of the lower arms 111 via a pivot pin 130 . the outside edges of the endplates 125 have anti - migration elements 131 to maintain the proper position of the distractor / sizer 110 on the vertebral bodies during distraction . the measurement bar 120 is calibrated to allow the surgeon to determine the size of vertebral body replacement required for the patient . the distractor / sizer 110 allows for distraction and sizing to be completed with one surgical tool . while the invention is susceptible to various modifications and alternative forms , specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail . it should be understood , however , that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed , but on the contrary , the invention is to cover all modifications , equivalents , and alternatives falling within the spirit and scope of the invention as defined herein .
a vertebral body replacement device , dimensioned for implantation between a first and second vertebral bone is described . the vertebral body replacement device includes a superior endcap , an inferior endcap and a central core between the superior and inferior endcaps . the vertebral body replacement device further includes a fusion aperture extending through the superior and inferior endcaps and central core . the vertebral body replacement device is made of radiolucent material and can be implanted from a lateral or anterior approach to the spine .