Abstract:
An intervertebral instrument includes a shaft having distal and proximal ends. The proximal end of the shaft includes an attaching feature connected to handle. The shaft defines a pair tracks disposed along a portion of the surface thereof. The distal end includes a pair of wings. Each track guides instruments and implants along the intervertebral instrument. The implants are configured to receive bone graft or bone enhancers. The distal end of the shaft may include a removably attachable tip configured to engage the implants. The implants and the removably attachable tip form an implantable intervertebral disk. An intervertebral instrument and implant kit is also disclosed. A method of inserting intervertebral implants is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 12/398,316 filed Mar. 5, 2009, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/068,564, filed Mar. 7, 2008, the entire contents of which are incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Technical Field 
     This application relates to intervertebral distracting instruments, intervertebral disc implants, and a method for inserting intervertebral disc implants between affected vertebrae to achieve spinal fusion. 
     2. Background of Related Art 
     The human spine is composed of thirty-three vertebrae at birth and twenty-four as a mature adult. Between each pair of vertebrae is an intervertebral disc, which maintains the space between adjacent vertebrae and acts as a cushion under compressive, bending, and rotational loads and motions. A healthy intervertebral disc has a great deal of water in the nucleus pulposus, which is the center portion of the disc. The water content gives the nucleus a spongy quality and allows it to absorb spinal stress. Excessive pressure or injuries to the nucleus can cause injury to the annulus, which is the outer ring that holds the disc together. Generally, the annulus is the first portion of the disc that experiences injury. These injuries are typically in the form of small tears. These tears heal by scar tissue. The scar tissue is not as strong as normal annulus tissue. Over time, as more scar tissue forms, the annulus becomes weaker. Eventually this can lead to damage of the nucleus pulposus. The nucleus begins to lose its water content due to the damage, i.e., it begins to dry up. Because of water loss, discs lose some of their ability to act as a cushion. This can lead to even more stress on the annulus and still more tears as the cycle repeats. As the nucleus loses its water content it collapses, allowing the vertebrae above and below the disc space to move closer to one another. This results in a narrowing of the disc space between the two vertebrae. As this shift occurs, the facet joints located at the back of the spine are forced to shift. This shift changes the way the facet joints work together, and thus, can cause problems in the facet joints as well. 
     When a disc or vertebra is damaged due to disease or injury, standard practice is to remove all or part of the intervertebral disc, insert a natural or artificial disc spacer, and construct an artificial structure to hold the affected vertebrae in place to achieve a spinal fusion. The procedure may be accomplished using various approaches such as anteriorly, posteriorly and transforaminally. Depending on which approach is used, a specific geometry spacer device is selected. 
     Anteriorly approached procedures are preferred when one of the clinician&#39;s goals is to use a spacer device that most closely matches the footprint of the vertebral body. This maximum sized footprint also allows for the introduction of a significant amount of bone graft. It may also promote a better bone fusion. The preferred instrument to introduce an anterior spacer device is a “sled” style instrument. The sled provides the necessary vertebral body distraction and a path for introducing the device. Unfortunately, the sleds currently available are very bulky, complicated to use, and obstruct the clinician&#39;s working view. 
     For the above stated reasons, a need exists for a system that includes an instrument for distracting the vertebral bodies in such a way that does not obstruct the surgeon&#39;s view and still allows additional disc space work to be performed. The system must also provide a pathway for introducing the device into the intervertebral disc&#39;s space. 
     SUMMARY 
     The present disclosure relates to an intervertebral instrument including a shaft having distal and proximal ends. The proximal end of the shaft includes an attaching feature for enabling the shaft to attach to a handle for manipulating the shaft. The shaft defines at least one track at least partially disposed along a portion of the surface thereof. The distal end of the shaft includes a pair of wings for distracting an intervertebral disk space defined between two vertebrae. Each track is configured and dimensioned to guide instruments and intervertebral implants used in intervertebral procedures toward the intervertebral disk space. The intervertebral instrument is configured and dimensioned to be utilized with a plurality of different sized patients. 
     In another embodiment of the intervertebral instrument, the distal end of the shaft includes a removably attachable tip configured and dimensioned to engage the implants. The removably attachable tip is configured and dimensioned to keep implants affixed thereto. The intervertebral implants and the removably attachable tip are configured and dimensioned to collectively function as an implantable intervertebral disk. The implantable intervertebral disk is configured and dimensioned to receive bone graft or bone enhancers to enable bone ingrowth. 
     The intervertebral implants include a pair of members. The members each have a body with top, bottom, inside, and outside surfaces. The top and bottom surfaces include ridges disposed thereon. The inside surface has at least one protuberance configured and dimensioned to engage the intervertebral instrument. At least one of the members includes at least one passage for receiving bone graft or bone enhancers to enable bone ingrowth. As such, at least one of the members is configured and dimensioned to receive bone graft or bone enhancers to enable bone ingrowth. 
     In one embodiment, the intervertebral implant includes a removably attachable portion configured and dimensioned to connect each member. The removably attachable portion includes a pair of tracks. Each track is configured and dimensioned to engage the at least one protuberance of each member. Each member is configured and dimensioned to remain affixed to the removably attachable portion. The combination of each member and the removably attachable portion collectively function as an implantable intervertebral disk when the removably attachable portion and each member are collectively detached from the intervertebral instrument. 
     An intervertebral instrument and intervertebral implant kit is also envisioned and includes an intervertebral instrument and at least one intervertebral implant in accordance with the present disclosure. The kit can also include a handle disposed at the proximal end of the shaft for manipulation of the shaft. In another embodiment of the kit, the shaft includes a removably attachable tip disposed at the distal end thereof. In this embodiment of the intervertebral instrument and intervertebral implant kit, the removably attachable tip and the at least one intervertebral implant are configured and dimensioned to collectively function as an implantable intervertebral disk. 
     One aspect of the present disclosure contemplates a method for inserting an intervertebral implant including the steps of inserting an intervertebral instrument into the intervertebral disk space, advancing an intervertebral implant along a track toward the intervertebral disk space, inserting the implant and a removably attachable tip in the intervertebral disk space, and selectively applying bone graft or bone enhancers into the intervertebral disk space for bone ingrowth. The step of inserting the intervertebral instrument can be performed using an anterior, a posterior, a lateral, or a transforaminal approach. During the process, a user can selectively pass complementary instruments down the at least one track for facilitating the insertion of the at least one implant and any removably attachable tip attached thereto. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of one of two identical members of an intervertebral implant in accordance with the present disclosure; 
         FIG. 2  is a perspective view, with parts separated, of one embodiment of the intervertebral instrument including a handle connected to the proximal end in accordance with the present disclosure; 
         FIG. 3  is a perspective view of the intervertebral instrument of  FIG. 2  (without the handle) including one embodiment of a complementary instrument attached thereto; 
         FIG. 4  is a perspective view of the intervertebral instrument of  FIG. 2  (without the handle) including another embodiment of a complementary instrument attached thereto; 
         FIG. 5  is a perspective view of the intervertebral instrument of  FIGS. 2-4  having the one member of  FIG. 1  of the two identical members of the intervertebral implant attached on one side of the distal end thereof and the second member of the two identical members of the intervertebral implant attached on the other side of the distal end thereof, the intervertebral instrument including a handle connected to the proximal end thereof; 
         FIG. 6  is a perspective view, with parts separated, of another embodiment of the intervertebral instrument in accordance with the present disclosure; 
         FIG. 7  is a perspective view of the intervertebral instrument of  FIG. 6  having the one member of  FIG. 1  of the two identical members of the intervertebral implant attached on one side of the distal end thereof and the second member of the two identical members of the intervertebral implant attached on the other side of the distal end thereof; and 
         FIG. 8  is a perspective view of a fusion implant disposed between two adjacent vertebrae in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Various embodiments of the present disclosure will now be described in detail with reference to the drawings, wherein like reference numerals identify similar or identical elements. In the drawings and in the description that follows, the term “proximal,” will refer to the end is closest to the operator, while the term “distal” will refer to the end that is farthest from the operator. In addition, the term “cephalad” is used in this application to indicate a direction toward a patient&#39;s head, whereas the term “caudad” indicates a direction toward the patient&#39;s feet. Further still, for the purposes of this application, the term “medial” indicates a direction toward the middle of the body of the patient, whilst the term “lateral” indicates a direction toward a side of the body of the patient (i.e., away from the middle of the body of the patient). The term “posterior” indicates a direction toward the patient&#39;s back, and the term “anterior” indicates a direction toward the patient&#39;s front. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. 
     Referring now to the drawings, in which like reference numerals identify identical or substantially similar parts throughout the several views,  FIG. 1  illustrates one portion of two identical portions of an intervertebral implant  10  (both portions shown in  FIG. 5 ). In accordance with the present disclosure, the intervertebral implant  10  includes first and second members  20 ,  30 . Each member  20 ,  30  has a body  22 ,  32  with a top surface  22   a ,  32   a , a bottom surface  22   b ,  32   b , an inside surface  22   c ,  32   c , and an outside surface  22   d ,  32   d . The top surface  22   a ,  32   a  and the bottom surface  22   b ,  32   b  include ridges  24 ,  34  disposed thereon. The inside surface  22   c ,  32   c  has a first protuberance  26 ,  36  distally disposed thereon and a second protuberance  28 ,  38  proximally disposed thereon. Each protuberance  26 ,  28 ,  36 ,  38  is configured and dimensioned to engage an intervertebral instrument  100 ,  200  ( FIGS. 2 and 6 ). Each member  20 ,  30  has a channel  25 ,  35  cut therethrough. Each channel  25 ,  35  extends from a respective first opening  25   a ,  35   a  disposed on each respective inside surface  22   c ,  32   c , to a respective second opening  25   b ,  35   b  disposed on each respective outside surface  22   d ,  32   d . In addition, a longitudinal passage  21 ,  31  extends through each respective member  20 ,  30  from a respective first aperture  21   a ,  31   a  disposed on the respective top surface  22   a ,  32   a  to a respective second aperture  21   b ,  31   b  disposed on the respective bottom surface  22   b ,  32   b . Each channel  25 ,  35  and each longitudinal passage  21 ,  31  are configured and dimensioned to receive bone graft or bone enhancers to enable bone ingrowth. 
     Referring to  FIGS. 2-5 , an intervertebral instrument  100  includes a shaft  110  having distal and proximal ends and an attaching feature  150 . The shaft  110  includes a sleeve  112  defining a first track  114  ( FIG. 2 ) and a second track  116  ( FIG. 5 ) extending longitudinally along a portion of opposing external surfaces of the shaft  110 . Each track  114 ,  116  is configured and dimensioned to guide instruments used in intervertebral procedures, such as the first instrument  80  shown in  FIG. 3  or the second instrument  90  shown in  FIG. 4  (each of which is described below), as well as the respective members  20 ,  30  of implants  10  toward the intervertebral disk space. The distal end of the sleeve  112  includes a pair of wings  118 ,  120  orthogonally disposed relative to first and second track  114 ,  116 . The wings  118 ,  120  interconnect with each other by a contoured distal groove  119 . The pair of wings  118 ,  120  are configured and dimensioned to distract an intervertebral disk space defined between two vertebrae. 
     Referring additionally to  FIGS. 2 and 5 , a handle  160  is removably attachable to the attaching feature  150  at the proximal end of the shaft  110 . The handle  160  includes a connector  162  centrally attached to an actuator  164  at the proximal end of the connector  162 . The actuator  164  includes grips  166  for engagement by a user&#39;s hand. The connector  164  is configured and dimensioned to distally and removably connect to the attaching feature  150  about the proximal end of the attaching feature  150 . As such, the handle  160  is configured and dimensioned to enable the shaft  110  to be manipulated. 
     Referring now to  FIG. 3  the first instrument  80  includes a shaft  82  and a distracting tip  84 . The shaft  82  is configured and dimensioned to engage the sleeve  112 ,  212  of each of the intervertebral instruments  100 ,  200  ( FIGS. 2 and 6 ) so that the distracting tip  84  can be positioned within the intervertebral disk space in order to further facilitate the distraction of adjacent vertebrae “V 1 ” and “V 2 ” ( FIG. 8 ). The distracting tip further includes pointed heads  86  disposed at the distal end thereof, at least one cavity  88  disposed in the body thereof for receiving members  20 ,  30 , and a measuring guide  89  disposed on the external surface of the body thereof for measuring the placement of members  20 ,  30 . 
     Referring now to  FIG. 4  the second instrument  90  includes a shaft  92  and a distracting tip  94 . The shaft  92  is configured and dimensioned to engage the sleeve  112 ,  212  of each of the intervertebral instruments  100 ,  200  ( FIGS. 2 and 6 ) so that the distracting tip  94  can be positioned within the intervertebral disk space in order to further facilitate the distraction of adjacent vertebrae “V 1 ” and “V 2 ” ( FIG. 8 ). The distracting tip further includes a top platform  96  and a bottom platform  98 , each platform  96 ,  98  including ridges  97  for engaging vertebrae “V 1 ” and “V 2 .” Each platform  96 ,  98  is separated by a space  99  for receiving members  20 ,  30 . 
     In a second embodiment of the intervertebral instrument, as illustrated in  FIGS. 6 and 7 , the intervertebral instrument  200  is substantially similar to the intervertebral instrument  100 . However, the intervertebral instrument  200  includes a shaft  210  with tracks  214 ,  216  and a removably attachable tip  270  at the distal end thereof. The removably attachable tip  270  removably attaches to the distal end of the sleeve  212  of the intervertebral instrument  200  by a pair of stems  213   a ,  213   b . The removably attachable tip  270  is configured and dimensioned to engage the members  20 ,  30  of the implant  10 . A pair of tracks  272 ,  274  is partially longitudinally defined along opposing external surfaces of the removably attachable tip  270 . The tracks  272 ,  274  are configured and dimensioned to guide the implants  10  ( FIG. 7 ) and their respective members  20 ,  30  thereon. The removably attachable tip  270  is configured and dimensioned to keep the implants  10  affixed thereto. The removably attachable tip  270  is configured and dimensioned to engage each protuberance  26 ,  28 ,  36 ,  38  of each respective member  20 ,  30  ( FIG. 1 ). As illustrated in  FIG. 8 , the intervertebral implant  10  and the removably attachable tip  270  are configured and dimensioned to collectively function as a unitary fusion implant  300  when the removably attachable tip  270  and each member  20 ,  30  are collectively detached from the intervertebral instrument  200 . The fusion implant  300  is configured and dimensioned to remain implanted in the intervertebral disc space, i.e., between adjacent vertebrae V. 
     It is contemplated and within the scope of the present disclosure that the intervertebral instruments  100 ,  200 , implants  10 , and implantable intervertebral disks  300  may be used during procedures performed anteriorly, posteriorly, laterally, and transforaminally. For example, using an anterior approach, minimal disc space preparation is performed and the intervertebral instrument  100 ,  200  is inserted into the disc space, preferably on its midline. The intervertebral instrument  100 ,  200  is rotated approximately 90 degrees engaging the endplates and separating them by the height of the instrument. Several sized intervertebral instruments  100 ,  200  are contemplated to allow for the variations between patients. Additional, complimentary instruments  80 ,  90  may be passed down the tracks  114 ,  116 ,  214 ,  216  to prepare the disc space for the implant  10 , or the implantable intervertebral disk  300 . Additional complimentary instruments include, but are not limited to, box chisels, scrapers and trial implants. When the final intervertebral implants have been appropriately sized, the final intervertebral implants may be packed with bone graft and passed down the tracks  114 ,  116 ,  214 ,  216  of the corresponding intervertebral instrument  100 ,  200 . After final placement of the intervertebral implant  10 , or the implantable intervertebral disk  300  has been achieved, the intervertebral instrument  100 ,  200  may be removed and the subsequent void may be filled with additional bone graft, potentially more than with a typical anterior approach implant. 
     Specifically with respect to intervertebral instrument  200 , the removably attachable tip  270  is made of an implant grade material, preferably PEEK. In doing so, the members  20 ,  30  are passed down the intervertebral instrument  200  so that they may engage and lock to the removably attachable tip  270 . As such, when the intervertebral instrument  200  is removed, the implantable intervertebral disk  300  becomes a one-piece design and the removably attachable tip  270  and the members  20 ,  30  collectively remain in the disc space as a unitary implant  300 . This design provides increased strength. 
     Each of these intervertebral instruments  100 ,  200  are configured and dimensioned to be used with a plurality of different sized patients. 
     While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Thus the scope of the embodiments should be determined by the appended claims and their legal equivalents, rather than by the examples given. 
     For example, it is within the scope of the present disclosure that members  20 ,  30  may be uniform unit without the removably attachable tip  270 , i.e. a single piece intervertebral implant.