Abstract:
A surgical staple for discectomy by an anterior approach that comprises a plate with sharp-pointed projections positioned at each of four corners of the plate and extending perpendicularly there from for frictional insertion into pilot holes formed in the vertebrae, and a pair of circular apertures in the plate spaced along a centerline for insertion of bone screws. The plurality of projections may further comprise four barbed and pointed projections that a surgeon may quickly tap into the bone, thereafter securing the staple with two smaller bone screws. An Annular C shaped retention locking clip retains the bone screws and prevents counter-rotation and back out.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application derives priority from provisional application 60/965,471 filed on Aug. 20, 2007. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the invention 
         [0003]    The present invention relates to a surgical staple for discectomy by anterior approach to the cervical spine. 
         [0004]    2. Description of the Background 
         [0005]    Spinal stenosis is a medical condition in which the spinal canal narrows and compresses the spinal cord and nerves causing pain and neural degeneration. This is commonly due to spinal degeneration that naturally occurs with aging but can also be caused by spinal disc herniation (from trauma for example), osteoporosis, tumor or a variety of other causes. Stenosis may occur at any point along the spinal column but is more prevalent in the cervical and lumbar regions of the spine. 
         [0006]    Cervical discectomy is a surgical procedure for treating spinal stenosis and disc herniation in the cervical region. Removal of the intervertebral disc and often the vertebral lamina (laminectomy) can relieve pressure from the spinal cord and neural structures. To maintain the stability of the spine in the absence of one or more intervertebral discs, spinal fusion is performed to immobilize the vertebrae. 
         [0007]    Spinal fusion or spondylosyndesis is a surgical technique used to combine two or more vertebrae. Supplementary bone graft tissue is used in conjunction with the body&#39;s natural osteoblastic processes. A variety of approaches to fusion are available including posterolateral fusion which places the bone graft between the transverse processes in the back of the spine and anterior or posterior interbody fusion which places the bone graft between the vertebra in the area usually occupied by the intervertebral disc. 
         [0008]    In most cases fusion is augmented by a process called fixation in which metallic screws, rods, plates or cages are implanted to stabilize the vertebra and facilitate bone fusion. The addition of hardware such as a cervical plate has been shown to maintain the stability of the graft/host junction increasing the chance of successful fusion. Conventional plates come in a basic construct of thin piece of metal and four screws that secure them to the bone. The typical screws are large and bulky. More recently narrow plates have emerged that use only two screws. There are benefits and drawback to both of these constructs. 
         [0009]    Large plates and multiple screws offer a solid fixation but are bulky, use large screws, and require significant retraction for cases of multiple fixations which may lead into patients suffering from swallowing difficulties and possible changes in voice. Narrow plates with only two screws offer little fixation but minimize the hardware and intrusion. A variety of designs for spinal fixation devices have been proposed over the years although none have been entirely satisfactory. 
         [0010]    It would be greatly advantageous to provide an anterior cervical staple for cervical fusion that: (1) allows for a more precise and a much smaller profile of fixation than prior art devices, (2) imposes less traction on the esophagus and trachea than prior art devices, (3) is lightweight, and (4) is inexpensive to manufacture and be applied for widespread use. 
       SUMMARY OF THE INVENTION 
       [0011]    It is an object of the present invention to provide an anterior cervical staple that allows for a precise, small profile of fixation. 
         [0012]    It is yet another object to provide an anterior cervical staple that imposes little traction on the esophagus and trachea. 
         [0013]    It is yet another object to provide a cervical staple that is strong and rigid yet lower profile. 
         [0014]    Still another object is to provide an anterior cervical staple that is lightweight. 
         [0015]    In accordance with the foregoing objects, the present invention comprises a surgical staple for the anterior approach that includes a plate with sharp-pointed projections positioned at each of four corners of the plate and extending perpendicularly there from for frictional insertion into pilot holes formed in the vertebrae, and a pair of circular apertures in the plate spaced along a centerline for insertion of bone screws. The plurality of projections further comprise four barbed and pointed projections that a surgeon may quickly tap into the bone, thereafter securing the staple with two smaller bone screws. This leads into a quicker implant application, less retraction as it may be done individually for each level and much stronger fixation than two screws alone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0016]    Other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment and certain modifications thereof, in which: 
           [0017]      FIG. 1  is a front perspective view of an embodiment of the staple. 
           [0018]      FIG. 2  is a front perspective view of another embodiment of the staple without the pins welded in place. 
           [0019]      FIG. 3   a  is a top view of an embodiment of the staple without the pins welded in place. 
           [0020]      FIG. 3   b  is a side view of an embodiment of the staple. 
           [0021]      FIG. 3   c  is an end view of an embodiment of the staple. 
           [0022]      FIG. 3   d  is a bottom view of an embodiment of the staple. 
           [0023]      FIG. 4  shows an embodiment of the staple affixed to the vertebrae. 
           [0024]      FIG. 5  is a perspective view of an embodiment of the screw locking clip. 
           [0025]      FIG. 6  is a perspective view of an embodiment of the locking clip recess in the plate. 
           [0026]      FIG. 7  is a perspective view of an embodiment of the screw locking mechanism of the staple 
           [0027]      FIG. 8  is a section view of an embodiment of the screw locking mechanism of the staple 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]    The present invention comprises a staple for anterior fusion.  FIG. 1  is a front/oblique perspective view of an embodiment of the staple  1 . The staple  1  as depicted in  FIG. 1  includes a substantially planar plate  2  with a plurality of projections  3 . The projections  3  are positioned at each of the four corners of the plate  2  and extend downwardly in a perpendicular direction from the bottom surface of the plate  2 . The projections  3  may be separate components press-fit through holes in the plate  2  or may be integrally formed therewith. The projections  3  are preferably barbed (such as, for example, with concentric annular teeth as shown in  FIG. 1 ) and terminate in a pointed distal end to facilitate their insertion into the vertebrae. The plurality of projections  3  provide for the staple  1  to be quickly hammered into the vertebrae V after a discectomy is done and bone graft is in place, as opposed to fixating the plate with four screws in a conventional manner. 
         [0029]    The body of the plate  2  includes two central inline gumdrop openings  5  proximate to and directed inward toward each other. The gumdrop openings  5  allow visualization of the graft through radiography. The plate  2  also includes a circular aperture  6  at each of the distal corners of the plate  2 . The circular apertures  6  allow screws to penetrate through the plate and into the bone. Each circular aperture  6  is centrally located between the respective projections  3  at each end of the plate  2 , outside the gumdrop openings  5  and in alignment therewith. 
         [0030]    The exact shape of the anterior staple  1  and plate  2  are a matter of design choice. The essential utility lies in the fact that it is equipped with four corner projections  3  and two inline circular apertures  6  for screws. Other staples  1  with these features have the requisite components. For example, the projections  3  and circular apertures  6  may be connected together by any other suitable plate  2 , such as a star-shaped plate  2  or double-H shaped plate as seen in the inset of  FIG. 1 . 
         [0031]      FIGS. 2 and 3   a  through  3   d  depict yet another embodiment of the plate  12 . In this alternate embodiment of the plate, circular screw apertures  16  remain at opposite ends of the plate along its midline and between the pair of projections  3  (not shown) at each end of the plate. Four apertures  13  are depicted for receiving projections  3  in this embodiment. As previously observed, projections  3  may also be integrally formed with plate  12 . Gumdrop openings  5  have been enlarged and merged to form a single ovoid opening  15 . As best seen in  FIGS. 3   b  and  3   c , the plate  12  is formed with a gentle concave curvature on both of the major planar axes. This compound curvature provides better cooperation between the plate  12  and the vertebra. The sides of the plate  2 ,  12  are tapered inward as seen in  FIGS. 1 and 3   a ,  3   d  and have a smooth contoured surface to prevent perforations of the vessels proximate the vertebral column. 
         [0032]    All of the above components can be constructed of durable, surgically, implantable material such as titanium or stainless steel. The staple  1  possesses a simple and scalable design and may be fabricated of other lightweight materials providing an appropriate degree of flexibility, resiliency, durability, and longevity. Also, the staple  1  is inexpensive to manufacture and sell, to provide for widespread use. 
         [0033]      FIG. 4  shows the staple  1  affixed to the vertebrae V. The staple  1  is of sufficient length to span the disc space between two adjacent vertebrae V. The staple  1  engages, via projections  3 , the vertebrae V adjacent to that disc space. 
         [0034]    The staple  1  according to the present invention is broadly applicable to the anterior, posterior and lateral aspects of the spinal column, including the cervical, thoracic or lumbar area. The staple  1  is especially beneficial in performing cervical facet fusion by the anterior approach (from the front of the neck), which can provide exposure from C2 down to the cervico-thoracic junction. Under this approach, only one thin vestigial muscle needs to be cut (after a skin incision is made), after which anatomic planes can be followed right down to the seven vertebra V of the cervical spine. Next, the surgeon retracts tissues and muscles and identifies the disc space that is in need of repair. Complete discectomy is performed and a bone graft is applied to the defect. 
         [0035]    A suitable drilling instrument such as a Universal Bone Drill—S. S. Gears (Cat. No. 320-010), Micro Hand Drill (Cat. No. 320-020), Universal Open Hand Drill—S. S. Gear (Cat. No. 320-030) is then used to create insertion holes in the vertebrae above and below the removed disk for receiving the projections  3  of the staple  1 . The staple  1  is applied across the disc space aligning projections  3  with the insertion holes as seen in  FIG. 4 . The surgeon drives the staple  1  into the bone V by applying a high impact force via a driving instrument such as a surgical mallet. The staple  1  is driven into the bone V until the projections  3  are fully inserted into the insertion holes, and the bottom surface of the top plate  2  rests against the surface of the vertebrae V. Next, conventional bone screws are inserted into the circular apertures  6  in the top plate  2  and into the vertebrae V for the purpose of stabilization. 
         [0036]      FIGS. 5-7  illustrate an optional locking clip  20  that may be utilized in cooperation with plates  2 ,  12  or other embodiments of the invention to prevent counter-rotation and loosening of the bone screws inserted into apertures  6 . With reference to  FIG. 5 , locking clip  20  is primarily “C” or “U” shaped having two arms  22  tracing an incomplete arc around a central aperture  24 . As seen in  FIG. 6 , the locking clip  20  seats within a conforming recess  32  formed about the apertures  6  and grips the bone screws inserted into the apertures  6 . With combined reference to  FIGS. 5-6 , a pair of extensions  26  are keyed to the recess  32  of plates  2 ,  12  to prevent counter-rotation of the bone screws. Extensions  26  are provided at the exterior of the arc opposite the opening in the arc as seen in  FIG. 5 . It should be understood that the location of the extensions in relation to the opening of the “C” may be other than as depicted. A single extension may also be utilized, preferably but not necessarily directly opposite the opening of the “C”. The top interior surface of the arms  22  are provided with a bevel  28  to form a frustum encircling the the aperture  24 . The distal ends of arms  22  may be provided with a widened profile at flares  30 . 
         [0037]    Locking clip  20  operates in cooperation with recess  32  in the surface of plates  2 ,  12  around aperture  6 ,  16 , as depicted in  FIG. 6 . Recess  32  is shaped to receive locking clip  22  in the recess such that the aperture  24  is generally aligned with the circular aperture  6 ,  16  of the plate  2 ,  12 . On insertion the extensions  26  abut the outer wall  34  of the recess preventing lateral movement in that direction. The extensions  26  may be affixed to the plate  2 ,  12  via small welds (as depicted), by micro-screws, or by seating them inside a pocket or overhanging lip formed on the plate  2 ,  12 . The diameter of aperture  24  of the “C” is slightly smaller than the diameter of circular aperture  6 ,  16  such that the arms  22  project over aperture  6 ,  16  when the locking clip  20  is inserted into the recess  32 . An annular groove  36  is provided in the interior surface of the circular aperture  6 ,  16  for receiving and retaining arms  22 . 
         [0038]    As seen in  FIGS. 7 and 8  a bone screw  40  having a head  42  and a lip  44  is inserted into the aperture  6 ,  16  and driven into the bone. The lip  44  is formed with an upward flare or taper, which may be frusto-conical or fluted. Upon insertion, as the tapered lip  44  encounters the bevel  28  of the locking clip  20  it forces the arms  22  of the “C” to spring open into the annular groove  36  allowing the head  42  and lip  44  of the screw  40  to pass. Once the screw  40  has passed the arms  22  spring back to their original shape projecting over the aperture  6 ,  16 . Engagement of the widened arms  22  in the groove  36  resist any counter-rotation or reversing action of the screw  40 . Because the underside of the clip  20  is not beveled the arms  22  will not spring open to permit the screw to back out. 
         [0039]    Locking clip  20  may can be constructed of durable, surgically implantable metal such as titanium or stainless steel or other lightweight materials providing an appropriate degree of flexibility, resiliency, durability, and longevity such as Polyetheretherketone (PEEK). 
         [0040]    It should now be apparent that the above-described anterior cervical staple provides for strong and robust fixation despite a precise, small profile, and yet it is lightweight and it imposes very little traction on the esophagus and trachea. 
         [0041]    Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It is to be understood, therefore, that the invention may be practiced otherwise than as specifically set forth in the appended claims.