Abstract:
The present specification contemplates a spinal implant device that goes into, for example, a corpectomy defect in any part of the spine. In one aspect, the device is substantially tubular and is comprised of two hollow rods that coaxially slide on one another. The device can thus then expand in length and can be locked or fixed at a particular length. The device is hollow to configure a malleable trocar to be placed into the device. With this trocar, polymethymethacrylate (PMMA) can be injected and packed into the vertebral body cephlad and caudad. Finally the device can be locked at a desired length by crimping it or locking it using other fastening means.

Description:
FIELD 
     The present specification relates generally to medical devices and more particularly relate to a spinal implant device. 
     BACKGROUND 
     A healthy spine is important to quality of life. In addition to muscular-skeletal support, it is also the central pathway for the nervous system. Many spinal defects can occur which may be mitigated or even repaired through spinal surgery. Corpectomy is one particular type of spinal surgery that typically involves removal of a portion of a vertebral body and/or adjacent intervertebral discs. Such removal is often followed by a reconstruction procedure to provide the mechanical support that is lost by the removal. 
     SUMMARY 
     This present specification contemplates a spinal implant device that goes into, for example, a corpectomy defect in any part of the spine. In one aspect, the device is substantially tubular and is comprised of two hollow rods that coaxially slide on one another. The device can thus then expand in length and can be locked or fixed at a particular length. The device is hollow to configure a malleable trocar to be placed into the device. With this trocar, polymethymethacrylate (PMMA) can be injected and packed into the vertebral body cephlad and caudad. Finally this device can be locked at a desired length by crimping it or locking it using other fastening means. 
     Once inserted, additional PMMA can be packed around the device to allow for further stabilization. This result is roughly analogous to the use of rebar as a structural support of cement. The device can be further designed to have threads on both sides of the implant so as to screw into the body above or below. It can be cannulated or noncannulated/solid. 
     The device can be configured in various dimensions and diameters for the appropriate purpose. The device may be particularly suitable for sites that are not amenable to traditional implants. 
     The device is contemplated for use in, as a non-limiting example, any corpectomy defect. The device can be sized differently for large or small spines. The device may also be used for spines with osteoporotic bone or difficult to access places. The device may be used for patients with cancer who need instant stabilization. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a side-sectional view of a spinal implant device. 
         FIG. 2  shows the spinal implant device of  FIG. 1  with character reference labels. 
         FIG. 3  shows the spinal implant device of  FIG. 1  and  FIG. 2  in an extended position, in contrast to the injection position shown in  FIG. 1  and  FIG. 2 . 
         FIG. 4  shows the spinal implant device of  FIG. 3  having a crimp applied to its diameter to keep each hollow rod fixed in relation to each other. 
         FIG. 5  shows the spinal implant device of  FIG. 1  in situ and ready for deployment. 
         FIG. 6  shows a kit of example surgical tools instruments can be used to deploy the spinal implant device of  FIG. 1 . 
         FIG. 7  shows the spinal implant device of  FIG. 5  during deployment using the instruments from  FIG. 6 . 
         FIG. 8  shows the spinal implant device of  FIG. 7  during injection of bone cement via the spinal implant device during deployment using the instruments from  FIG. 6 . 
         FIG. 9  shows the spinal implant device of  FIG. 8  during further deployment of the device into surrounding vertebra using the instruments from  FIG. 6 . 
         FIG. 10  shows the spinal implant device of  FIG. 9  fully deployed. 
         FIG. 11  shows an alternative embodiment utilizing a set screw rather than a crimp. 
         FIG. 12  shows an alternative embodiment utilizing a lock ring which can be used rather than a crimp. 
         FIG. 13  shows the lock ring of  FIG. 12  in use. 
         FIG. 14  shows an alternative embodiment with forked ends for each rod. 
         FIG. 15  shows an alternative embodiment wherein one of the rods is solid and has a channel for flowing bone cement therealong. 
         FIG. 16  is an end view of the solid rod of  FIG. 15  through the lines XVI-XVI. 
         FIG. 17  shows another surgical instrument that can be used with the spinal implant devices. 
         FIG. 18  shows an alternative embodiment for the spinal implant device of  FIG. 1  and surgical instruments that can be used therewith. 
         FIG. 19  shows the use of the lock ring from  FIG. 12  to secure each rod as part of another embodiment. 
         FIG. 20  shows a hollowing instrument as another embodiment. 
         FIG. 21  shows an alternative embodiment with a drip tray. 
         FIG. 22  shows an end view of the drip tray of  FIG. 20 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1  and  FIG. 2 , a spinal implant device is indicated generally at  50 . Device  50  can be made from any suitable non-toxic or bio-compatible material, such as medical-implant grade stainless steel or plastic. Other materials can include titanium, polyetherketone (PEEK), polyetherketone (PEK), polyetherketoneketone (PEKK), polyetherimide, or polyphenylsulfone, and bismuth trioxide (BiO 3 ) or other material with radioopacity such that it can be viewed under an imaging beam with reduced or minimal artifacts. 
     For illustrative convenience,  FIG. 1  shows device  50  without specific character reference labels, while  FIG. 2  includes such labels. Referring now to  FIG. 2 , device  50  comprises a first hollow rod  54  that is configured to slidably receive a second hollow rod  58  therein. 
     First hollow rod  54  comprises a distal end  62  and a proximal end  66 . A tapered section  70  and a cylindrical section  74  interconnects distal end  62  and proximal end  66 . 
     Distal end  62  comprises an opening  78  that communicates the interior of device  50  with the exterior of device  50 . 
     Tapered section  70  comprises an angle A and a length B that is configured so that tapered section  70  can be driven into a vertebral body. 
     Cylindrical section  74  comprises a length C that is about half the distance of a reconstruction space left by a corpectomy. Further understanding about the selection of length C will become apparent from the following discussion. Cylindrical section  74  has a substantially uniform inside diameter D along its length ending at the wider end of tapered section  70 . 
     Diameter of opening  78  can be selected to be forty percent of diameter D, and likewise the diameter of opening  110  can be selected to be forty percent of diameter H. The taper, as defined by B and A, and by F and E. Can be selected so that B is about .5 cm and F is about .5 cm. The angles A and E can be selected to substantially correspond to the taper of the trocar chosen to make a pilot hole in the target vertebral body. 
     Cylindrical section  74  also comprises a port  82  which provides communication from the exterior of device  50  to the interior of device  50 . As will be discussed further below, port  82  is configured to receive a malleable trocar so that a bone cement, such as polymethylmethacrylate (PMMA) can be injected into port  82  and be expressed from opening  78 . Port  82  typically has a circular opening that defines a cylindrical passage towards the interior of device  50 . 
     Proximal end  66  defines its own opening  86 . Opening  86  has a diameter that substantially corresponds to inside diameter D and is configured to receive second hollow rod  58  therein, so that second hollow rod  58  can slidably move within cylindrical section  74 . 
     The wall thickness of first hollow rod  54  is selected, with due consideration to the material used to construct hollow rod  54 , to provide be sufficiently rigid to pierce veterbral bone and to also to provide at least a certain degree of mechanical support as part of a reconstruction following a corpectomy. 
     Second hollow rod  58  is structurally quite similar to first hollow rod  54  and when device  50  is assembled as shown in  FIG. 2 , second hollow rod  58  is almost a mirror image of first hollow rod  54  except differently dimensioned so that second hollow rod  58  can be slidably received within first hollow rod  54 . 
     Accordingly, second hollow rod  58  also comprises a distal end  90  and a proximal end  94 . Likewise, a tapered section  102  and a cylindrical section  106  interconnects distal end  90  and proximal end  94 . 
     Distal end  90  comprises an opening  110  that communicates the interior of device  50  with the exterior of device  50 . As discussed above, PMMA injected via port  82  may be expressed from opening  110 . 
     Tapered section  102  comprises an angle E and a length F that is configured so that tapered section  102  can be driven into a vertebral body. Angle E and length F may be different from angle A and angle B due to the overall smaller size of second hollow rod  58 , and yet are still selected for driving into a verterbral body. 
     Cylindrical section  106  comprises a length G that is about half the distance of a reconstruction space left by a corpectomy. However, length G may be longer than length C to accommodate the fact that a portion of cylindrical section  98  remains within cylindrical section  74  when device  50  is in an extended position, again discussed further below. Cylindrical section  106  has a substantially uniform inside diameter H along its length ending at the wider end of tapered section  102 . The outer diameter of cylindrical section  106 , not labeled, is slightly smaller than inside diameter D, such that leakage of injected PMMA from opening  86  is minimal or obviated, but still accommodating coaxial slidable movement of cylindrical section  106  within cylindrical section  74 . 
     Various versions of device  50  can be provided having a different dimensions for one or more of A, B, C, D, E, F, G, or H, with each version being configured to accommodate the spines of persons of differing heights, weights, etc. The choice of angles can be influenced by the choice of a trocar or other instrument used to make a starter-hole in the corresponding vertebral body. Dimensions can also be chosen so that device  50  fit a vertebral balloon or kytoplasty balloon. As a non-limiting example, the tapers could be three times the diameter of the hole from which the cement is expressed; so that the taper is almost conical. 
     Cylindrical section  106  also comprises a port  114  that is alignable with port  82  to provide communication from the exterior of device  50  to the interior of device  50 , and more specifically directly to the interior of cylindrical section  106 . As will be discussed further below, port  114  is configured to receive a malleable trocar so that a bone cement, such as polymethylmethacrylate (PMMA) can be injected into port  82  and port  114  and be expressed from opening  110 . Port  114  typically has a circular opening that defines a cylindrical passage towards the interior of cylindrical section  106  that has substantially the same dimensions as port  82 . 
     Proximal end  94  defines its own opening  118 . Opening  86  has a diameter that substantially corresponds to inside diameter D and is configured to receive second hollow rod  58  therein, so that second hollow rod  58  can slidably move within cylindrical section  74 . 
     The wall thickness of second hollow rod  106  is selected, again with due consideration to the material used to construct hollow rod  106 , to be sufficiently rigid to pierce vertebral bone and to also to provide at least a certain degree of mechanical support as part of a reconstruction following a corpectomy. 
     At this point it may be noted that  FIG. 1  and  FIG. 2  show device  50  in an injection position, whereby a substantial portion of cylindrical section  106  is coaxially encased by cylindrical section  74 , and port  82  and port  114  are aligned.  FIG. 3 , in contrast to  FIG. 1  and  FIG. 2 , shows device  50  in an extended position, whereby second hollow rod  58  has been slid outwardly from first hollow rod  54  such that the distance between distal end  90  and distal end  62  is farther apart in  FIG. 3  than in  FIG. 1  and  FIG. 2 . 
       FIG. 4  also shows device  50  in the extended position of  FIG. 3 , but wherein a crimp  122  has been applied to the overlapping portions of first hollow rod  54  and second hollow rod  58  and thereby mechanically secure device  50  into the extended position. Note that a crimp  122  is but one means contemplated of mechanically securing device  50  into the extended position, and other means are contemplated. For example mechanical fastener could also be applied, such as an adhesive or a rivet or a screw. 
     As will now be explained, device  50  can be used to strengthen or stabilize a portion of a vertebral column in various circumstances where the column may be weakened, such as for example as a result of a corpetomy.  FIG. 5  shows device  50  in a fully retracted position whereby port  82  and port  114  are not aligned and cylindrical section  106  is encased by cylindrical section  74  distal end  90  and distal end  62  are closer together than in  FIG. 1  and  FIG. 2 . In  FIG. 5 , device  50  is shown in situ between a first vertebral body  126  and a second vertebral body  130  and nestled in relation to a resected vertebral body  134  that is between first vertebral body  126  and a second vertebral body  130 . It is to be understood that  FIG. 5  is not intended to be to scale but rather is schematic in nature for illustrative purposes. Furthermore the example representation of resected vertebral body  134  is not intended to literally represent a resected vertebral body  134  but is intended to provide a schematic representation for illustrative purposes. Again, the reason for the resection of resected vertebral body  134  is not particularly limited, but can, for example, be the result of a corpectomy. 
     The view in  FIG. 5  contemplates that the patient has been prepped and draped and that device  50  has been fully retracted so that device  50  can be implanted between first vertebral body  126  and second vertebral body  130  according to the teachings herein. 
       FIG. 6  shows surgical instruments that are presently contemplated for use in completing the implantation of device  50  from the state shown in  FIG. 5 . A first clamp  138  is contemplated having a pair of jaws  142  with a complementary diameter to the exterior diameter of cylindrical section  74 . Jaws  142  may have a rubber coating or other material that reduce slippage so that first hollow rod  54  can be held in a substantially fixed position, as discussed later below. A second clamp  146  is contemplated having a pair of jaw  150  complementary to the diameter of the exterior diameter of cylindrical section  106 . Jaws  146  may have a rubber coating or other material that reduce slippage so that second hollow rod  58  can be moved coaxially in relation to first hollow rod  54  while first hollow rod  54  is held fixed using first clamp  138 . While not shown, it is generally contemplated that clamp  138  and clamp  146  will each comprise a ratcheting locking mechanism, which permits jaws to progressively close but restricts jaws from opening unless a specific release is actuated on the ratcheting locking mechanism. Such ratcheting locking mechanisms are known in the art. A crimping tool  154  is also contemplated having a pair of jaws  158  that are formed so as to be able to form crimp  122  shown in  FIG. 4 . Crimping tool  154  also comprises a pair of handles  162  that can be squeezed in order to apply sufficient compressive force via jaws  158  to form crimp  122 . Crimping tool  154  may also comprise a ratcheting locking mechanism. In a variation, not shown, each jaw  158  may comprise a boss or other protuberance to provide a dimpled crimp at the point where the boss contacts the rod, rather than forming a contiguous crimp around the entire diameter. 
       FIG. 7  shows the view of  FIG. 5  except that jaws  142  of clamp  138  are shown as grasping first hollow rod  54 , while jaws  150  of clamp  146  are shown grasping second hollow rod  58 . In this event, first hollow rod  54  can be held fixed or moved along the direction of arrow H, second hollow rod  58  can also be held fixed or moved along the direction of arrow I. Using this technique, end  62  can be urged towards vertebral body  126 , while end  90  is urged towards vertebral body  130 . Likewise end  62  can be manipulated to pierce vertebral body  126  if desired and affix end  62  therein, while end  90  can be manipulated to pierce vertebral body  130  if desired and affix end  90  therein. 
     As a result of the actions described in relation to  FIG. 7 , device  50  is eventually adjusted into the injection position as shown in  FIG. 8 . Clamp  138  or clamp  146  may be now removed, or continued to be used to retain device  50  in the injection position. In  FIG. 8  clamp  138  and claim  146  are still shown as being used to retain device  50 . A flexible trocar  166  is also represented in  FIG. 8 , which is used to inject PMMA  170  or other curable flowable bone cement into device  50  and express PMMA  170  from opening  78  into the vicinity of vertebral body  126  and from opening  110  into the vicinity of vertebral body  130 . While not shown in  FIG. 8 , it is contemplated that trocar  166  may be inserted toward either opening  78  or toward opening  110  to direct more PMMA  70  to the respective vertebral body  126  or vertebral body  130 . Trocar  166  can thus be of different lengths so that PMMA  170  exits at a desired location. A syringe (not shown) or other injecting device may also be connected to trocar  166  to urge PMMA  170  into trocar  166 . 
     Referring now to  FIG. 9 , it is contemplated that the injection of PMMA  170  is complete and that trocar  166  has been removed. Furthermore,  FIG. 9  contemplates, if desired, the further movement of first hollow rod  54  along the direction of arrow H to further embed end  62  into vertebral body  126 , or the further movement of second hollow rod  58  along the direction of arrow I to further embed end  90  into vertebral body  130 . 
     A number of other embodiments are contemplated. For example, tapered section  70  or tapered section  102  or both of them could be provided with exterior threads, such that rotation of a respective rod will bite into a respective surrounding vertebral body. Such threading would further mechanically secure device  50 . 
     Another embodiment is shown in  FIG. 11 , wherein a modified version of device  50 , shown as device  50   a  is provided. In device  50   a , crimp  122  is obviated and in its place, a set screw  200   a  is provided for affixing rod  54  to rod  58 . One or more channels  204   a  (or the like) may be provided about the periphery of rod  58  in order to receive set screw  200   a , such that when set screw  200   a  is fully tightened its tip occupies channel  204   a  and thereby secures rod  54  to rod  58 . 
     A further alternative to crimping is shown in  FIG. 12  and  FIG. 13 .  FIG. 12  shows a side-view of a lock ring  208   b  having a hinge  212   b  and a clasp  216   b . Lock ring  208   b  can be unclasped, as shown in  FIG. 12 , and the halves opened so that lock ring  208   b  can be placed around rod  58 . The diameter of lock ring  208   b , and the clasp  216   b  are sized to be securely affixed to rod  58 , so that rod  54  is prevented from sliding along the length of rod  58 , as shown in  FIG. 13 . 
     Another embodiment is shown in  FIG. 14 , wherein a modified version of first hollow rod  54   c  and second hollow rod  58   c  are provided. First hollow rod  54   c  and second hollow rod  58   c  each have a forked tip configuration. Bone cement can be expressed out of one or more of each end  62   c - 1  or end  62   c - 1  and out of one or more of each end  90   c - 1  or end  90   c - 2 . Each fork may be driven into a respective vertebral body to secure its respective rod therein. 
     Another embodiment is shown in  FIG. 15  and  FIG. 16  and indicated as device  50   d . In device  50   d , first hollow rod  54  is the same as used in device  50 . However, second rod  58   d  is substantially solid but comprises a channel  220   d  along its length. Channel  220   d  can be aligned with port  82  so that delivered bone cement travel therealong and exits from tip  90   d.    
     A further variation on device  50   d  (not shown) contemplates the provision of one or more channels, (like channel  220   d ) along either the exterior or rod  58  and a corresponding boss along the interior of rod  54  that fits within the channel. In this manner, rod  54  and rod  58  can slide coaxially with each other, but cannot rotate in relation to each other. Other mechanical means to permit coaxial movement while restricting rotational movement will occur to those skilled in the art. Such channel and boss combinations can be about three millimeters, for example. 
     In another variation, port  82  can be a slot that run along a portion of the length of rod  54 , rather than the hole as shown in  FIG. 15 . 
     Another embodiment is shown in  FIG. 17  in the form of a solid trocar  230  having a handle  234 , a shaft  238  and a tip  242 . Tip  242  is oriented at a ninety degree angle in relation to handle  234 . It is contemplated that before insertion of device  50  (or any of its variants), trocar  230  can be used to make a pilot hole in an appropriate vertebral body, such a hole being then used to receive a respective end of device  50  (or its variants). 
     Another embodiment is shown in  FIG. 18  in the device  50   e  that is substantially the same as device  50  but also comprises a first boss  250   e  on first hollow rod  54   e  and a second boss  254   e  on second hollow rod  58   e . Additionally a pair of surgical instruments  258   e  are provided having a handle  262   e  and a shaft  266   e  with a chamber  270   e  for receiving boss  250   e  and boss  254   e  respectively. Device  50   e  can be used in combination with instruments  258   e  as an alternative to the use of clamp  138  and clamp  146  in association with device  50 . 
     In some implementations, it is contemplated that bone cement or PMMA will overflow and surround the exterior of device  50 , and not simply be confied to the interior of device  50  or the adjacent vertebral bodies. In this situation, bosses  250   e  and  254   e  can also additionally provide reinforcement as PMMA cures around each boss  250   e ,  254   e . It can thus be desired to provide a plurality of bosses on each rod to provide such reinforcement once PMMA cures. 
     Another embodiment is shown in  FIG. 19  wherein a pair of lock rings  208   b  are used at each end of device  50  once device  50  has been fully deployed. Different sized lock rings  208   b  can be provided to accommodate the different diameters of each rod  54 . When lock rings  208   b  are used as shown in  FIG. 19 , lateral movement of device  50  is restricted. Different configurations of lock rings  208   b  may also be provided. For example, the side of lock ring  208   b  that abuts a vertebral body may be flared to provide greater mechanical contact between the lock ring  208   b  and the adjacent vertebral body. 
     Another embodiment is shown in  FIG. 20  which shows a hollowing instrument  276  that comprises a flexible sleeve  280  and a semi-rigid articulating arm  284  that passes through sleeve  280 . Sleeve  280  and arm  284  are passed through device  50 , as shown, and into vertebral body  130 . The tip  288  of articulating arm  284  comprises a cutting surface to hollow out a small portion of vertebral body  130  to accommodate the tip of device  50  and bone cement. The hollowing instrument  276  can create cavity to receive either kyphoplasty balloon or bone cement. It will thus be now be apparent that the teachings herein can be used to optionally deploy a kyphoplasty balloon. 
     A further embodiment is shown in  FIG. 21 , in a further variation of device  50   f  where a drip tray  290   f  is provided along rod  58   f . Drip tray  290   f  can be provided to capture excess PMMA and which can they flow along the length of drip tray  290   f.    
     While various embodiments have discussed the use of rings or clamps or crimps to secure rod  54  and rod  58  it is contemplated that additional mechanical strength is provided by the cured PMMA. 
     It will now be apparent that the present specification contemplates many variations. The choice of a particular variation can be based on surgical considerations as to the best possible outcome for a particular patient. For example, in a high thoracic (neck area) procedure, it may be desired to select solid versions of device  50 , but in a mid lumbar region, a canulated version of device  50  may be more desired.