Abstract:
An intervertebral distractor possesses a scissors-like mechanism for actuating its distal portion for the spreading of adjacent vertebrae. The distal portion of the distractor possesses a pair of extension members laterally offset therefrom with each extension member possessing a vertebral endplate-engaging member.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/273,307, filed Mar. 2, 2001, the entire contents of which are incorporated by reference herein. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to an instrument and method for spreading apart adjacent vertebrae of a vertebral column to facilitate insertion of an implant into the intervertebral space. More particularly, the present invention relates to a distractor for the distraction of vertebrae using an anterior or posterior approach.  
           [0004]    2. Background of the Invention  
           [0005]    Back pain can be caused by either one or a combination of the following: a loss of disc height, compression of nerve roots, degenerative disc disease, spondylolisthesis, and other causes. The current standard of treatment for people suffering from severe back pain requiring surgical intervention due to different types of pathology is by intervertebral fusion. Intervertebral fusion is achieved by fusing two adjacent vertebral bodies together by removing the affected disc and inserting a suitably sized implant into the disc space that allows for bone to grow between the two vertebral bodies bridging the gap left by the disc removal.  
           [0006]    Known intervertebral fusion procedures typically involve the steps of removing a portion or all of the affected disc material, spreading apart adjacent vertebrae with a distractor, and inserting an implant, e.g., allograft rings, c-sections, dowels, etc., or threaded cages, into the intervertebral space previously occupied by the removed disc material. This procedure can be done either from the front of the patient (anterior interbody fusion) or from the back (posterior interbody fusion).  
         SUMMARY OF THE INVENTION  
         [0007]    In accordance with the present invention, a vertebral distractor is provided which permits an implant to be inserted into the intervertebral space during distraction of adjacent vertebrae. The implant is inserted into the disc space between the vertebrae-spreading members of the distractor while the latter are in spreading contact with the opposed upper and lower vertebral endplates of the distracted adjacent vertebrae.  
           [0008]    In accordance with the present invention, a vertebral extractor is provided which comprises:  
           [0009]    a) a pair of operating members each of which possesses a proximal portion adapted for manual gripping and a distal portion adapted for spreading vertebrae, the operating members being connected to each other by a pivot member disposed between their proximal and distal portions;  
           [0010]    b) a pair of extension members, each extension member being connected to the distal portion of each operating member and laterally offset on the same thereof; and,  
           [0011]    c) at least one vertebral end plate-engaging member connected to each extension member.  
           [0012]    During use of the intervertebral distractor to achieve extraction of adjacent vertebrae, the offset arrangement of its extension members with their corresponding vertebral endplate-engaging members defines a frame-like opening or aperture through which a fusion implant can be readily inserted into the intervertebral space without hindrance or obstruction.  
           [0013]    In one embodiment of the foregoing distractor, each operating member of the distractor is made up of several articulating members possessing a sliding and pivoting action which permits parallel distraction of adjacent vertebrae.  
           [0014]    Further in accordance with the present invention, an instrument set for carrying out an intervertebral fusion procedure is provided which includes the vertebral distractor of this invention and one or more other instruments employed in such procedure, e.g., one or more rasps for removal of tissue from a vertebral endplate, one or more trials, a fusion implant inserter, a slaphammer and a bone tamp. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIGS. 1 and 2 are perspective views of a distractor of this invention in, respectively, the closed and the open (i.e., vertebrae spreading) positions;  
         [0016]    [0016]FIGS. 3 and 4 are partial views of the distal portions of the distractor of FIG. 1 in, respectively, the closed and open positions;  
         [0017]    FIGS.  5 - 7  illustrate the operation of the vertebral distractor of FIG. 1 to achieve the spreading of adjacent vertebrae in a distraction procedure; and,  
         [0018]    FIGS.  8 - 12  show various views of a rasp which is especially well suited for use with the distracter of FIG. 1 in carrying out an intervertebral fusion procedure.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    Preferred embodiments of the presently disclosed vertebral distractor of the invention will now be described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views.  
         [0020]    FIGS.  1 - 4  illustrate one preferred embodiment of the presently disclosed vertebral distractor shown generally as  100 . Vertebral distractor  100  includes first and second operating members  112  and  114  which are pivotably connected to each other about a pivot member  116 . Operating members  112  and  114  include grips  118  and  120 , respectively, and jaws  122  and  124 . Jaw  122  is secured to the distal end of operating member  112  and jaw  124  is secured to the distal end of operating member  114 . A slot  126  is formed in the proximal end of each jaw. Slot  126  is dimensioned to slidably receive a pin which can take the form of screw or rivet  128 . Screws or rivets  128  secure jaws and  122  and  124  to the distal end of operating members  112  and  114 , respectively. A biasing member  130  is positioned between operating members  112  and  114  to urge grips  118  and  120  apart in the direction indicated by arrows “A” in FIG. 1. A locking member  132 , including a screw  134  and nut  136 , extends through an opening (not shown) in operating member  112  and is rotatably fastened to operating member  114 . Nut  136  is threaded onto screw  134  to lock grips  118  and  120  at any position between open and closed positions of the jaws.  
         [0021]    Each jaw  122  and  124  includes elongated body portions  122   a  and  124   a,  lateral extensions  122   b  and  124   b,  and a pair of spaced-apart arms  122   c  and  124   c.  If desired, the angle of spaced-apart arms  122   c  and  124   c  relative to the horizontal can deviate a few degrees therefrom so as to provide a lordotic angle or a kyphotic angle. Extensions  122   b  and  124   b  are laterally offset from the same side of jaws  122  and  124 , e.g., at an angle of approximately 90° relative to the longitudinal axis of distractor  100 , and in the open position, form a frame-like opening with unobstructed access to the intervertebral space thereby facilitating insertion of the fusion implant. The distal end of each arm has a smooth rounded surface  138  or other configuration, e.g., that of a wedge, to facilitate entry of arms  122   c  and  124   c  into the intervertebral space. Each of arms  122   c  and  124   c  includes a vertebral endplate-engaging  146  which engages a vertebral endplate after the arms have been within the intervertebral space. Vertebral endplate-engaging surfaces  146  are advantageously textured, e.g., grooved, to improve their gripping contact with the vertebral endplates.  
         [0022]    A pair of support members  140  are secured to a side of jaws  122  and  124  opposite lateral extensions  122   b  and  124   b.  The distal end of each support member  140  is pivotally fastened to the one of jaws  122  and  124  by a screw or rivet  142 . Support members  140  are rotatably connected to each other by rotating member  144  and are held in close alignment with jaws  122  and  124  to support, or stabilize, the jaws during movement of the jaws between approximated and distracted positions.  
         [0023]    The various elements constituting vertebral distractor  100  are aligned along a common longitudinal axis. However, if desired, the distractor can feature one or more bends or curves in a direction which is opposite the direction of extensions  122   b  and  124   b  so as to place the distal portion of the instrument at an angle to the proximal portion of the instrument. Thus, e.g., a bend or curve of a few degrees can be introduced into the instrument between pivot member  116  and jaws  122  and  124  and/or at the distal portions of jaws  122  and  124 , e.g., at about the location where extension members  122   b  and  124   b  are connected to the jaws. This arrangement provides even greater facility of insertion of the fusion implant into the intervertebral space since it displaces the proximal portion of the instrument away from its vertebral endplate engaging members.  
         [0024]    FIGS.  8 - 12  illustrate a preferred type of rasp, shown generally as  10 , which can advantageously be used in conjunction with the vertebral distractor  100  of this invention in an intervertebral fusion procedure. Rasp  10  includes an elongated handle portion  12  and a head portion  14 . Head portion  14  has a circular configuration and includes upper and lower surfaces  16  and  18  and a sidewall  20 . Alternately, head portion  14  may assume other configurations including triangular, rectangular, square, etc. The distal end of  22  of upper and lower surfaces  16  and  18  is tapered to facilitate entry into the intervertebral space. Each of the upper and lower surfaces  16  and  18  includes a multiplicity of protrusions  24  formed thereon. Protrusions  24  have a triangular configuration including a preferably, substantially arcuate wall  26 , a sloped wall  28  and an edge  30 . Alternatively, wall  26  maybe substantially flat and vertical. The configuration of protrusions  24  will effect abrasion only when rasp  10  is moved over a surface in the forward direction. When the rasp is moved in a rearward direction the sloped wall will slide over the surface and no abrasion to a surface will occur. Alternately, the orientation of the protrusions may be altered to provide abrasion during rearward movement of head portion  14  or during forward and rearward movement of head portion  14 . Further, abrasion may be provided by rotational movement of head portion  14  about the longitudinal axis of the spine.  
         [0025]    As illustrated in FIGS. 9 and 11, head portion  14  includes a bore  32  dimensioned to receive the distal end  34  of handle portion  12 . Head portion  14  and handle portion  12  may be permanently attached using any known fastening technique including welding, brazing, adhesives, etc. Alternately head portion  14  may be removably secured to handle portion  12  using any known fastening technique including threading, friction, set screw(s), etc. By providing rasp  10  with a removable head portion  14 , different size head portions could be provided with a single handle portion such that the appropriate size rasp head portion could be chosen during a surgical procedure to accommodate a particular size intervertebral opening. Alternately, handle portion  12  and head portion  14  may be formed of monolithic construction (not shown). Preferably, rasp  10  is formed of a surgical grade stainless steel. However, other materials suitable for surgical use and meeting the requisite strength requirements could also be used to manufacture rasp  10  including plastics, ceramics, metals, etc.  
         [0026]    Vertical distractor  100  and rasp  10  can be used during an anterior or posterior surgical spinal fusion procedure adjacent vertebrae and to prepare the vertebrae endplates for receiving an implant. Additionally, vertical distractor  100  can be used for during anterolateral as well as transforaminal lumbar interbody fusion procedures. During a typical surgical spinal fusion procedure, the surgeon will perform a partial or total discectomy to prepare the intervertebral space for implant insertion. For example, the surgeon may perform a block discectomy, leaving the outer annulus of the intervertebral disc intact, while removing disc material to provide an anterior or posterior opening. Thereafter, the surgeon will use a trial or gauge to determine the size of the disc space and thus, the size of the implant required for the surgical procedure. A suitable trial is disclosed in U.S. patent application Publication Ser. No. 2002/0,016,633, the contents of which are incorporated by reference herein. A slaphammer may be used to remove the trial from the intervertebral space. Next, as illustrated in FIGS.  5 - 7 , the surgeon will position arms  122   c  and  124   c  of jaws  122  and  124 , respectively, into the intervertebral space such that grooved surfaces  146  engage the vertebral endplates. Operating members  112  and  114  of vertebral distractor  100  are compressed to distract the adjacent vertebrae  150  and  152  a desired amount. Locking member  132  can be adjusted to maintain the vertebrae at the desired degree of distraction. Because a pair of spaced arms are provided on each jaw, distractor  100  will provide a parallel distraction of vertebrae by orienting each jaw with the appropriate lordotic or kyphotic angulation. The trials and rasps may be similarly configured with surfacing to create a parallel, lordotic or kyphotic orientations. Thereafter, the surgeon will use the rasp to remove any remaining disc material from the vertebral endplate and to remove a portion of the cortical endplate to provide bleeding bone. Bleeding bone improves and quickens fusion of the implant and the vertebrae. After the vertebral endplates have been prepared using the rasp, the surgeon will again check the size of the intervertebral space with a trial. An implant can now be inserted into the intervertebral space between jaws  122  and  124 . In an alternate embodiment, the surgeon may use the rasp on the vertebral endplates prior to distracting the vertebrae with the vertebral distractor  100 .  
         [0027]    It is to be understood that the above description is intended to cover all the generic and specific features of the apparatus and method described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween. Moreover, the apparatus may be modified to include additional features not currently shown. For example, a gauge may be attached to the distractor to indicate the actual degree or distance of distraction. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Thos skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.