Abstract:
A spinal buttress plate includes a body having a top surface and a bottom surface and including an annular lip, a ledge, and a pair of teeth. The annular lip defines an opening. The annular lip and the opening are adapted to engage a screw for facilitating the securement of the buttress plate to one or more vertebrae. The ledge defines an aperture. The ledge and aperture are adapted to engage an instrument for positioning the buttress plate adjacent a spinal bone graft. The teeth are disposed in spaced-apart relation on the bottom surface of the body and are positionable within the one or more vertebrae.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to, and the benefit of, U.S. Provisional Patent Application Ser. No. 61/107,115, filed Oct. 21, 2008, the contents of which are hereby incorporated by reference in their entirety. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates generally to a spinal plate and, more particularly, to a spinal buttress plate for providing spinal bone graft support. 
         [0004]    2. Background of Related Art 
         [0005]    The human spinal column is a highly complex structure. It includes more than twenty discrete bones, known as vertebrae, coupled sequentially to one another to house and protect critical elements of the nervous system. Vertebrae, like any other bone, often fracture and require surgical reconstruction. Grafting materials such as autologous bone, allograft bone, xenograft, organic/inorganic material (“bone paste”), or other similar materials are commonly used in these procedures. These materials are used to promote bone healing as a biologic response and to provide structural support. 
         [0006]    Intraarticular fractures are a common example of a situation in which grafting material can be used. The primary role of the grafting material is to buttress and/or support bone fragments in an anatomic or functional position. Additionally, the graft material may function to promote healing. 
         [0007]    If the grafting material does not maintain its position at the site of application, several potential problems may occur. First and foremost, the material no longer functions for its intended purpose. Migration of graft material may lead to migration of the fragment to be supported. As a result, complications may arise such as joint incongruity, arthritis, stiffness, pain, crepitance with joint motion, non-union or malunion. Furthermore, secondary procedures (i.e. additional surgical procedures), may also be required. 
         [0008]    In addition to losing intended function, migration of graft material may have additional deleterious effects. Migration of grafting material into adjacent soft tissues may initiate an inflammatory reaction or cause complications from mechanical pressure and irritation. For instance, graft material pressing on a nerve may cause nerve damage. Graft material pressing on tendons may cause fraying or rupture of the tendon or it may even cause scarring and limitation of tendon gliding. Migration of graft material into an adjacent joint can cause arthritis and joint damage. Moreover, the ability of grafting material to stimulate bone formation may cause problems if the graft migrates into the soft tissues. Occasionally, this may even stimulate formation of heterotopic bone in the soft tissues, which can cause scarring, stiffness, inflammation and pain. 
         [0009]    Accordingly, a need exists for a spinal buttress plate that can be readily affixed to a vertebral body for protecting a vertebral bone graft. 
       SUMMARY 
       [0010]    The present disclosure relates to a spinal buttress plate including a body having a top surface and a bottom surface and including an annular lip, a ledge, and a pair of teeth. The annular lip defines an opening. The annular lip and the opening are adapted to engage a screw for facilitating the securement of the buttress plate to one or more vertebrae. The annular lip may be formed of commercially pure titanium. The diameter of the annular lip increases as the surface of the annular lip approaches the top and bottom surfaces of the body. The annular lip may have a curvaceous surface. The material of the annular lip may be softer than the material of the screw such that the screw deforms the annular lip as the screw is secured thereto. The screw may be a self-tapping or a self-starting screw. 
         [0011]    The ledge defines an aperture and may be disposed on either or both ends of the body. The ledge and aperture are adapted to engage an instrument for positioning the buttress plate adjacent a spinal bone graft. 
         [0012]    The teeth are disposed in spaced-apart relation on the bottom surface of the body and are positionable within the one or more vertebrae. The teeth and the ledge are disposed on opposing ends of the body. One or both of the teeth are mounted to the body by a footing. 
         [0013]    In one aspect, a method of attaching a buttress plate includes providing a buttress plate including a body having an annular lip defining an opening, a ledge defining an aperture, and a pair of teeth. The method includes providing an instrument having a rod and a prop extending therefrom adapted to support the buttress plate, mounting the rod within the aperture of the ledge, supporting the ledge against the prop of the instrument; positioning the buttress plate adjacent a superior vertebral body on one or both of the anterior or lateral sides of the spinal column over a bone graft, and securing one or more screws through the opening of the body of the buttress plate into the superior vertebral body. The method includes driving the pair of teeth into the superior vertebral body. The method may include deforming the annular lip with the at least one screw. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    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: 
           [0015]      FIG. 1A  is a top perspective view of a spinal buttress plate in accordance with the present disclosure; 
           [0016]      FIG. 1B  is bottom perspective view of the spinal buttress plate set forth in  FIG. 1A ; 
           [0017]      FIG. 1C  is a top plan view of the spinal buttress plate of  FIGS. 1A and 1B ; 
           [0018]      FIG. 1D  is a cross-sectional view of  FIG. 1C  taken along section line  1 D- 1 D; 
           [0019]      FIG. 2A  is a side view of a plate holder; 
           [0020]      FIG. 2B  is a top plan view of the plate holder of  FIG. 2A ; 
           [0021]      FIG. 2C  is a cross-sectional view of the plate holder of  FIGS. 2A and 2B ; 
           [0022]      FIG. 3  is an enlarged view of the detailed area D of  FIG. 2A ; 
           [0023]      FIG. 4  is an exploded view of the plate holder of  FIGS. 2A and 2B ; 
           [0024]      FIG. 5  is perspective view of a self-starting screw; and 
           [0025]      FIG. 6  is a side view of a self-tapping screw. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0026]    Various embodiments of the presently disclosed spinal buttress plate and system 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 of a device or system that is closest to the operator, while the term “distal” will refer to the end of the device or system 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. 
         [0027]    Referring now to the drawings, in which like reference numerals identify identical or substantially similar parts throughout the several views, the spinal buttress plate shown in  FIGS. 1A-1D  is referred to generally as the plate  100 . The plate  100  has a body  122 , the body  122  including a pair of teeth (a first tooth  106  and a second tooth  108 ) disposed in spaced-apart relation on the underside thereof. The body  122  also has an opening  102  disposed on a distal end  122   d  thereof. The opening  102  has an annular lip  104 . Additionally, the body  122  has a receiving ledge  114  disposed on a proximal end  122   p  thereof. The receiving ledge  114  has an aperture  120  whereby a plate holder  900  ( FIG. 2A ) can releasably grasp and position the plate  100  over a spinal bone graft. The first and second tooth  106 ,  108  are affixed to the body  122  via respective first and second footings  110 ,  112 . The body  122  has first and second side notches  124 ,  126  and a top notch  128 . The receiving ledge  114  is disposed at the proximal end  122   p  of the body  122  and is centrally positioned along a longitudinal axis “L” thereof. The receiving ledge  114  is offset a top and bottom distance from the respective top and bottom surfaces  122   t,    122   b  of the body  122 . The top distance is defined by the depth of a top side wall  116 , while the bottom distance is defined by the depth of a bottom side wall  118 . The length and width of the ledge  114  are defined to mesh with a prop  908  of a support arm  906  on a plate holder  900  ( FIG. 2A ). In other words, the ledge  114  is dimensioned to be releasably grasped by the plate holder  900 . The aperture  120  is centrally disposed through the ledge  114 . The aperture  120  is shaped to receive an engaging portion, such as a retaining rod  916  of a plate holder  900 . In certain variations, the aperture is substantially elliptical or substantially circular. However, the aperture can be any polygonal shape. 
         [0028]    Furthermore, the annular lip  104  of the opening  102  is defined by a pair of mirrored frustoconical cavities (see  FIG. 1D ) extending into the body  122  about the opening  102  from the top and bottom surfaces  122   t,    122   b.  In other words, the diameter of the annular lip  104  increases as the surface of the annular lip  104  approaches the top and bottom surfaces  122   t,    122   b  of the body  122 . The annular lip  104  has the smallest diameter at the most central portion of the body  122  between the top and bottom surfaces  122   t,    122   b  and the largest diameter at the top and bottom surfaces  122   t,    122   b  of the body  122 . The annular lip  104  may have a curvaceous surface. It is envisioned that the plate  100  is made from a relatively soft material such as commercially pure titanium or another suitable biocompatible material. 
         [0029]      FIGS. 2A-2C  and  FIGS. 3-4  illustrate a plate holder  900 . The plate holder  900  has a central assembly  902 . The central assembly  902  has a handle  904  with a pawl end  904   a,  a support arm  906 , and a pivot  912 . The support arm  906  has a prop  908  disposed on the distal end thereof, while slide cavities  910   a,    910   b,    910   c  can be disposed therein in spaced-apart relation for receiving respective slides  918   a,    918   b,    918   c  extending from a shaft  914  having a retaining rod  916  disposed on the distal end thereof. A driving orifice  920  is disposed on the proximal end of the shaft  914  for receiving a drive bar  934  connected to the top portion of an actuator  922 . The actuator  922  is pivotably connected to the central assembly  902  at the pivot  912 . The actuator  922  is connected to a first bias bar  926  via screws  932 . In addition, the actuator  922  and a ratchet  924  are connected at their respective distal ends. The first bias bar  926  and a second bias bar  928  are compressively connected at their respective distal ends. The second bias bar  928  is connected to the handle  904  of the central assembly  902  via screws  932 . 
         [0030]    Referring now to  FIGS. 5 and 6 , a self-starting screw  10  and a self-tapping screw  50  are illustrated. The self-starting screw  10  has a shank  12 , a tapered head portion  14  located at a proximal end of the shank  12  and a pointed tip portion  16  located at a distal end of the shank  12 . The shank  12  has a uniform outer diameter and a first continuous helical thread  20  formed thereon. The first continuous helical thread  20  defines a cancellous bone thread. A second continuous thread  22  is formed on the head portion  14  and defines a thread thereon. The pitch of the first thread  20  is greater than the pitch of the second thread  22 . Each of the threads  20 ,  22  has a uniform pitch. The self-starting screw  10  also includes a self-starting portion that extends proximally from the pointed tip portion  16 . The self-starting portion includes first and second sidewalls that define a flute section  36 . The first and second sidewalls of the flute section  36  extend from the pointed tip  16  to a second crest of cancellous bone thread  20 . 
         [0031]    The self-tapping screw  50  includes a shank  52 , a tapered head portion  54  located at a proximal end of the shank  52 , and a rounded tip portion  56  located at a distal end of the shank  52 . The shank  52  has a uniform outer diameter and a first continuous helical thread  58  formed thereon. The first continuous helical thread  58  defines cancellous bone thread. A second continuous thread  60  is formed on the head portion  54  and defines a thread thereon. The pitch of the first thread  58  is greater than the pitch of the second thread  60 . Each of the threads  58 ,  60  have a uniform pitch. The self-tapping screw  50  includes a self-tapping portion that extends proximally from the rounded tip portion  56 . The self-tapping portion includes first and second sidewalls that define a flute section  80 . The first and second sidewalls of the flute section  80  extend from the rounded tip  56  towards the second crest of cancellous bone thread  58 . Each of the screws  10 ,  50  are formed from a suitable biocompatible material such as Ti-6AL-4V alloy. Alternatively, it is contemplated that other suitable biocompatible materials may be used to form the screws  10 ,  50 . 
         [0032]    Referring additionally to  FIGS. 1A-1B  and  5 - 6 , the lip  104  is configured for engaging the screw  10 ,  50  such that rotating the screw  10 ,  50  causes the threads  22 ,  60  of the head  14 ,  54  of the respective screw  10 ,  50  to engage the lip  104  such that each screw  10 ,  50  is secured in the opening  102  and resists backing out of the screw opening  102 . Since the material of the plate  100  is softer than the material of the screw  10 ,  50 , the threads  22 ,  60  on the screw  10 ,  50  engage and deform the lip  104  as the screw  10 ,  50  is inserted into the opening  102 , thereby securing the screw  10 ,  50  to the body  122 . The threads  22 ,  60  of the screw  10 ,  50  engage the lip  104  when the screw  10 ,  50  is in various angular orientations with respect to the axis of the opening  102 . A suitable screw and locking mechanism for use in the plate  100  are disclosed in U.S. Pat. No. 6,322,562 to Wolter, the entire contents of which are hereby incorporated by reference, although other mechanisms for locking the screw  10 ,  50  to the plate  100  are contemplated. 
         [0033]    In operation, an end user affixes the plate holder  900  to the receiving ledge  114  of the buttress plate  100 . Generally, the end user actuates the actuator  922  causing the drive bar  934  to drive the shaft  914  and rod  916  distally and the ratchet  924  to drive proximally. The ratchet teeth  930  cam under the pawl end  904   a  of the handle  904  as the end user continues to actuate the actuator  922 . The rod  914  engages the aperture  120  from the top surface of the ledge  114  and locks the plate  100  to the prop  908  as the prop  908  engages the ledge  114  on the bottom surface of the ledge  114 . Upon fully engaging the plate  100 , the end user releases the actuator  922  and the pawl end  904   a  of the handle  904  locks into the ratchet teeth  930  of the ratchet  924  from the compression caused by the biasing of the first and second bias bars  926 ,  928 , holding the plate  100  in locked position. 
         [0034]    The end user then positions the plate  100  using the plate holder  900  into the superior vertebral body on the anterior or lateral side of the spinal column over a bone graft. When the desired position is reached, the end user can partially engage first and second teeth  106 ,  108  with the bone enabling the end user to fasten a bone screw  10 ,  50  through the opening  102  on the plate  100  to the superior vertebral body. Consequently, the bone screw  10 ,  50  fastening drives first and second teeth  106 ,  108  farther into the bone for additional support. The end user can remove the plate holder  900  from the plate  100  by re-actuating the locked actuator  922 , which disengages the pawl end  904   a  of the handle  904  from the ratchet teeth  930 , enabling the compression forces from the first and second bias bars  926 ,  928  to springingly thrust actuator  922  and ratchet  924  forward, disengaging the rod  916  from the aperture  120 . The end user can then disengage the plate holder  900  from the plate  100 . As mentioned above, the bone screw  10 ,  50  is locked to the plate  100  to inhibit the screw  10 ,  50  from backing out since the material of the plate  100  is softer than the material of the screw  10 ,  50 . 
         [0035]    Since the first and second tooth  106 ,  108  provide added engaging support to the plate  100  while it is affixed to the vertebra, the end user may remove the plate holder  900  when the first and second teeth  106 ,  108  are partially engaged into the bone. Alternatively, the end user can remove the plate holder  900  when the plate  100  is fully fastened by the bone screw  10 ,  50 . 
         [0036]    It will be understood that various modifications may be made to the embodiments of the presently disclosed spinal buttress plate. Therefore, the above description should not be construed as limiting, but merely as exemplifications of embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the present disclosure.