Abstract:
A system for distracting two tissue surfaces away from one another within a spine, involving a plurality of biocompatible and generally rectangular spinal inserts configured to be successively stacked within a spine to distract the two tissues surfaces away from one another. Each spinal insert has a generally planar top surface having a leading edge and a trailing edge, a generally planar bottom surface disposed generally parallel to the top surface and including a leading edge and a trailing edge, and a beveled surface extending from at least one of the leading edge of the planar top surface and the leading edge of the planar bottom surface. The beveled surface is configured to allow a currently inserted spinal insert to be positioned at least one of above and below a previously introduced spinal insert to distract the two tissue surfaces.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application claims priority from commonly owned and co-pending U.S. patent application Ser. No. 11/053,016, filed Feb. 8, 2005, which claims priority from U.S. patent application Ser. No. 09/904,179 filed Jul. 11, 2001, the complete disclosures of which are hereby incorporated herein by reference in their entirety for all purposes. Additionally, the present application claims benefit under 35 U.S.C. §119(e) from U.S. Provisional Application Ser. No. 60/218,975 filed Jul. 17, 2000, the entire contents of which are hereby expressly incorporated by reference into this disclosure as if set forth fully herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention provides a stackable interlocking intervertebral support system, and methods for supporting adjacent vertebrae using a stackable interlocking intervertebral support system. 
         [0003]    In preferred aspects, the present invention comprises two, three (or more) separate portions which are stacked together to form an interlocked intervertebral support assembly. Advantageously, two of these three (or more) portions may be identical in size and shape, as will be explained. In the optional aspect of the invention in which only two separate portions are used, these two portions may be identical to one another in size and shape. 
         [0004]    In one preferred aspect, the present invention preferably comprises a center portion, a top portion and a bottom portion. The top portion is positioned on top of the center portion and the bottom portion is positioned under the center portion. The top and bottom portions may be identically shaped and dimensioned, but are positioned upside down with respect to one another, on opposite sides of the center portion, as will be explained. In another aspect of the invention, however, only two portions are used, with the top portion being positioned directly on top of the bottom portion (with no center portion(s) required). In further aspects of the present invention, more than three separate portions may be used. In such aspects, a plurality of identically shaped center portions are stacked one on top of the other. In other alternate aspects, various portions (including top, center and bottom portions) may be stacked side by side one another). 
         [0005]    In accordance with the present invention, the center portion has a recess in each of its top and bottom surfaces. Each of the top and bottom portions of the present system also have recesses therein which engage and interlock with the recesses in the center portion. More specifically, the top portion preferably has a recess in its bottom surface and the bottom portion has a recess in its top surface which engage the respective recesses In the top and bottom of the center portion. 
         [0006]    The present invention is assembled simply by stacking the three portions (top, center &amp; bottom) one on top of one another in a patient&#39;s intervertebral space. When stacked together, the present assembly will form an “X” or “cross” type of shape, providing support over a large surface area of the adjacent vertebrae. In further optional aspects of the invention, more than three portions are stacked together one on top of one another in a patient&#39;s intervertebral space. Specifically, a plurality of center portions are stacked on a bottom portion and a top portion is stacked thereover. 
         [0007]    A further advantage of the present system is that, when assembled, it provides support in two perpendicular directions, thereby supporting a large area of the adjacent vertebrae, yet using only a minimal amount of material in actually achieving this advantage. This advantage is due, at least in part, to the assembled “cross” shape of the assembly. Moreover, the present invention can be dimensioned to be of a size such that the “arms” of the “cross” extend outwardly towards the edges of the vertebrae, providing support over the cortical bone at the vertebral edges. 
         [0008]    Another advantage of the present invention is that, as the adjacent vertebrae tend to push together, this will hold the present support assembly together, even in the absence of any mechanical fastening or securing mechanisms between the top, center &amp; bottom portions of the system. Specifically, both (one or more) center portion(s) and the two top/bottom portions are uniquely shaped and dimensioned such that when positioned one on top of another, they will remain firmly together, resisting any lateral tendency to slip apart. 
         [0009]    Yet another advantage of the present invention is that it may be easily inserted into a patient&#39;s intervertebral space in a bi-portal minimally invasive surgical approach. Specifically, the bottom portion may be inserted through a first cannula into the patient&#39;s intervertebral space, with the center portion(s) thereafter being inserted through a second cannula into the patient&#39;s intervertebral space. The top portion may then be inserted through the first cannula into the patient&#39;s intervertebral space. In this aspect of the invention, the first and second cannulae are generally perpendicular to one another, being positioned in opposite posterolateral approaches. Alternatively, all of the portions of the assembly may be inserted through the same operating cannula into the patient&#39;s intervertebral space, with successive portions then rotated perpendicular to one another after they have been positioned in the patient&#39;s intervertebral space. 
         [0010]    In preferred aspects. each of the center, top and bottom portions of the assembly have a tapered end, which is dimensioned to engage a ramping structure disposed within one of the recesses on an adjacent portion such that the separate portions of the assembly may be “slip-fit” together, with pressure between the adjacent vertebrae holding each of the pieces of the assembly together. In addition, an optional tapered front end of the center portion may be used to pry apart the adjacent vertebrae, prior to positioning the top portion thereover. 
         [0011]    In optional aspects of the invention, a plurality of the present support assemblies can be positioned in a patient&#39;s intervertebral space, either on top of, beside, or both on top of and beside, one another. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Many advantages of the present invention will be apparent to those skilled in the art with a reading of this specification in conjunction with the attached drawings, wherein like reference numerals are applied to like elements and wherein: 
           [0013]      FIG. 1  is an exploded front/side perspective view of an exemplary arrangement of the present stackable interlocking intervertebral support system; 
           [0014]      FIG. 2  is a top front/side perspective view of the exemplary arrangement of the present system seen in  FIG. 1 ; 
           [0015]      FIG. 3  is a bottom front/side perspective view of the exemplary arrangement of the present system seen in  FIG. 1 ; 
           [0016]      FIG. 4  is a top plan view of the exemplary arrangement of the present system seen in  FIG. 1 : 
           [0017]      FIG. 5  is a front/side elevation view of the exemplary arrangement of the present system seen in  FIG. 1 , (shown in two adjacent vertebrae in an exploded view); 
           [0018]      FIG. 6  is a rear elevation view of the exemplary arrangement of the present system seen in  FIG. 1 ; 
           [0019]      FIGS. 7A ,  7 B and  7 C are front perspective views of the center portion of the present system; 
           [0020]      FIG. 8  is a rear perspective view of the center portion of the present system; 
           [0021]      FIG. 9A  is a top plan view of the center portion of the present system; 
           [0022]      FIG. 9B  corresponds to  FIG. 9A . but has center ramp/recesses angled to a lateral axis across the center portion; 
           [0023]      FIG. 10  is a side elevation view of the center portion of the present system; 
           [0024]      FIG. 11  is a front elevation view of the center portion of the present system; 
           [0025]      FIG. 12  is a top front perspective view of the bottom portion of the present system, (or is a bottom perspective view of the top portion of the present system): 
           [0026]      FIG. 13  is a top rear perspective view of the bottom portion of the present system, (or is a bottom perspective view of the top portion of the present system): 
           [0027]      FIG. 14  is a bottom rear perspective view of the bottom portion of the present system: 
           [0028]      FIG. 15  is a top plan view of a bottom portion of the present system; 
           [0029]      FIG. 16  is a side elevation view of the bottom portion of the present invention; 
           [0030]      FIG. 17  is a front elevation view of the bottom portion of the present invention; 
           [0031]      FIG. 18  is a top perspective view of a patient&#39;s intervertebral space showing the positioning of the present system (with one vertebra shown in phantom); 
           [0032]      FIG. 19  is a top plan view of a patient&#39;s intervertebral space showing postero lateral approaches used in positioning the separate portions of the present system; 
           [0033]      FIG. 20  is an exploded perspective view of a patient&#39;s intervertebral space showing an assembly comprising four portions, (including two center portions, a top portion and a bottom portion) positioned one on top of the other; and 
           [0034]      FIG. 21  is an exploded perspective view of a two-portion intervertebral support assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]    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 interlocking intervertebral support system disclosed herein boasts a variety of inventive features and components that warrant patent protection, both individually and in combination. 
         [0036]    Referring first to  FIG. 1 , an exploded front side perspective view of the present stackable interlocking intervertebral support system  5  is provided. In one preferred arrangement, system  5  comprises a center portion  10 , a bottom portion  20 A and a top portion  2013 . (As will be explained, other arrangements are possible). As can be seen throughout the attached Figs., portions  20 A and  20 B may preferably be identical in shape and size. Accordingly, the present system  5  may actually comprise one center portion  10  and two top/bottom portions  20 . 
         [0037]      FIGS. 2 and 3  show respective top and bottom perspective views of the present system, in an assembled format. As will be explained, an advantage of the present system is that it provides support between adjacent vertebrae without requiring any mechanical fastening systems between the top, center and bottom portions of the assembly. Rather, center portion  10 , bottom portion  20 A and top portion  20 B are all assembled together with their novel shapes assisting in keeping them together. 
         [0038]    Referring to the attached Figs., (and to  FIGS. 7A to 10  in particular), center portion  10  is provided with bottom recess  11 A and top recess  11 B, passing thereacross, as shown. Also referring to the attached Figs., (and to  FIGS. 13 to 16  in particular), bottom portion  20 A is also proved with a top recess  21 A. (Conversely, being identically shaped to bottom portion  20 A, top portion  20 B is also provided with a bottom recess  21 B). 
         [0039]    An important aspect of the present invention is that, when bottom portion  20 A is positioned below center portion  10 , recess  21 A will engage and interlock with recess  11 A. Conversely, when top portion  208  is positioned on top of center portion  10 , recess  218  will engage and interlock with recess  11 B. Accordingly, when center portion  10 , bottom portion  20 A and top portion  20 B are stacked together, recesses  11  will engage recesses  21 , such that assembly  5  forms an “X” or “cross” shape. As can be seen, recesses  11  and  21  are preferably positioned mid-way (ie: centrally) along the respective lengths of portions  10  and  20 . As illustrated, assembly  5  will have an “X” shape with each of the four branches of the “X” being relatively equal in length. Within the scope of the present invention, however, recesses  11  and  21  may instead be positioned closer to one end of their respective portions than another, such that the “X” shape of the present assembly will instead have two of its branches longer than another two of its branches (and may even approach a “V” shape assembly). Moreover, the angles at which recesses  11  and  21  cut laterally across portions  10  and  20  can be angled as denoted by angle “α” in  FIG. 9B  (for center portion  10 ). As such, when stacked together, the angles between each of the  4  “arms” of the “X” of the present assembly need not be perpendicular to one another. (For example, 2 pairs of arms may be 60° apart, with the other 2 pairs of arms being 120° apart). 
         [0040]    As can be seen throughout the attached Figs., center portion  10  has a bottom surface  12  and a top surface  14 . Bottom portion  20 A has a bottom surface  22 A, and top portion  2013  has a top surface  22 B. When the three portions of the present assembly are assembled, surface  14  is coplanar with surface  22 B and surface  12  is coplanar with surface  22 A. As shown in  FIG. 5 , surfaces  12  and  22 A together support (ie: buttress against) vertebra  50  and surfaces  14  and  22 B together support (ie: buttress against) an opposite adjacent vertebra  52 . (For illustration purposes only, opposite adjacent vertebrae  50  and  52  are shown in an exploded view). It is to be understood that after distraction vertebrae  50  and  52  will tend to move toward one another, applying pressure to the top and bottom of assembly  5 , keeping assembly  5  together. As can be seen, surfaces  12 ,  14 ,  22 A, and  22 B may all have a plurality of small groves  23  (or other surface irregularities) which increases sliding friction across these surfaces. 
         [0041]    A further advantage of the novel shape of center portion  10  is that it has a tapered front end  13 . In a preferred method of assembling the present support assembly  5 , as illustrated in  FIGS. 18 and 19 , center portion  10  is advanced minimally invasively into patient P in a posterolateral approach through cannula  60  and positioned between opposite adjacent vertebrae  50  and  52  (shown here as being on top of vertebra  50 ). Tapered end  13  will tend to pry apart adjacent vertebrae  50  and  52 , providing the surgeon with a “self-distracting” vertebral support system. Bottom portions  20 A and top portions  20 B are advanced through minimally invasive cannula  62  in an opposite posterolateral approach. Typically, bottom portion  20 A is positioned first, followed by center portion  10  and top portion  20 B stacked sequentially thereover. 
         [0042]    Each of center portion  10  and top portion  20 B also have tapered front ends  13  and  25  which (as center portion  10  and top portion  20 B are sequentially slipped over bottom portion  10  and center portion  10 ), will engage ramp structures  17  disposed within recesses  21 A and  11 A in respective bottom portion  20 A and center portion  10 , such that center portion  10  and top portion  20 B are “snap-fitted” over bottom portion  20 A. More specifically, during insertion, vertebrae  50  and  52  will tend to rest against surfaces  12  and  14  of center portion  10 . As center portion (s)  10  and top portion  20 B are “snap-fitted” over bottom portion  20 A and center portion  10 , their respective tapered ends  13  and  25  will assist in urging vertebrae  50  and  52  apart. When assembled, ramp structures  27  disposed within recesses  21 A and  21 B will interlock with engage ramp structures  17  in center portion  10 , such that assembly  5  will be held together, by intervertebral pressure (on surfaces  14  and  22 B, and surfaces  12  and  22 A) urging vertebrae  50  and  52  together. 
         [0043]    Portions  10  and  20  of the present invention may preferably each have a narrow elongated shape, as shown. Accordingly, they may be dimensioned to be small enough to pass through an operating cannula, for example, an operating cannula having an interior diameter equal to, or less than, 8 mm or 6 mm. 
         [0044]    In preferred aspects of the invention, portions  10  and  20  are preferably made of bone allograft material, offering the advantages of promoting healing and eventual absorption of system  5 . Alternatively, portions  10  and  20  may be made of metal, or any other suitable bio-implantable material. Each of center portion  10 , and top/bottom portion  20  may optionally have side grooves  15  and  25  in which opposite prongs  42  of a two prong inserter  40  (such as a “pinching” inserter as shown in  FIGS. 7A and 13 ) which may be used when inserting each of center portion  10  and top/bottom portions  20  through respective surgical cannulae  60  and  62 . 
         [0045]    If desired, the vertical height of the present system can be increased by stacking more than one center portion  10  (as shown in  FIG. 20  in which an assembly  5 A is shown having two center portions  10 ). It is to be understood that more than two center portions  10  may be used in assembling the present intervertebral support system, as desired. In yet another optional aspect of the invention, assemblies  5  may be made small enough such that more than one can be positioned side by side in a patient&#39;s intervertebral space. As is seen in  FIG. 21 , a two portion intervertebral support assembly  5 B is also contemplated. In this aspect of the invention, top portion  20 B is positioned directly on top of bottom portion  20 A, with recesses  21 A and  21 B interlocking together. Many other system arrangements are possible. For example, two, or more than two portions  10  can be stacked on top of one another (similar to the stacking of portions  20  in  FIG. 21 ).