Abstract:
A cervical spinal fixation system that offers a strong and stable construct for maximum fusion augmentation and yet is versatile enough for any patient and is easy to use. A method of implanting a fusion plate is disclosed where the plate includes at least two primary fastener openings. In one embodiment the method includes the step of the throat of the patient being opened which provides access to the spinal column of the patient. The fusion plate can be inserted into the throat opening, and the fusion plate is then positioned on the spinal column.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Priority of U.S. Provisional Patent Application Ser. No. 61/039,486, filed Mar. 26, 2008, incorporated herein by reference, is hereby claimed. 
     
    
     BACKGROUND 
       [0002]    The human spinal column includes a row of 26 bones or vertebrae in the back and allows a person to stand up straight and bend over. The spinal column also protects a person&#39;s spinal cord from being hurt. The vertebrae are commonly classified by position into cervical (neck), thoracic (chest), and lower back (lumbar) vertebrae, with intervertebral discs separating each vertebra from the adjacent vertebrae. 
         [0003]    In the neck, degeneration of discs often causes vertebrae to undesirably compress their associated spinal nerves, causing uncomfortable symptoms such as pain, numbness, weakness, and disordered reflex symptoms. Degenerated cervical discs may be treated by resection of the discs utilizing a surgical approach through the neck. Once the resection is completed, common procedure is to fuse the vertebrae adjoining the former position of the removed disc. Other conditions which may require fusion include treatment of fractured or broken vertebrae, correction of deformities, treatment of herniated discs, treatment of tumors, treatment of infections, or treatment of instability. 
         [0004]    Fusion is a surgical technique in which one or more of the vertebrae of the spine are united or joined to prevent relative movement. The spinal fusion procedure does not directly connect the vertebrae; rather, a bone graft or spacer is positioned between endplates of adjacent vertebrae of the spine during surgery. Over a period of time healing occurs as living bone from vertebrae spans the intervertebral graft and connects the adjacent vertebrae together. Fusion is complete when living bone has completely spanned the graft and the adjacent vertebrae are thus connected by a solid bridge of bone. 
         [0005]    Various apparatus are known for retaining vertebrae of a spinal column in a desired spatial relationship so that fusion of the vertebrae can occur. Such known apparatus can include rod or plate systems, with either commonly being attached to the vertebrae with bone screws, hooks, or other structures. For example, anterior fusion of the cervical spine is commonly stabilized using a fixation plate screwed to the vertebrae. The rods and/or plates can be temporary (removed after fusion of the vertebrae is complete) or permanent. 
         [0006]    However, currently available plates are generally larger than needed to simply maintain adjacent cervical vertebrae in fixed orientation in most patients. These oversized structures require a relatively large incision and dissection for insertion, which may be complex and time-consuming for the surgeon and require broader dissection of tissues in the neck and greater pressure on tissues being moved out of the way. This generally results in longer healing time and a larger risk of complications in the patient than in a smaller incision and dissection. 
         [0007]    Accordingly, it is desired to develop procedures and implants for surgically addressing stenosis through minimally invasive procedures, and preferably such surgical procedures can be performed on an outpatient basis. 
       SUMMARY 
       [0008]    In one embodiment is provided a method of implanting a fusion plate, having at least two openings, into a patient is described. 
         [0009]    In one embodiment of the method, a throat of the patient is dissected, providing access through the throat dissection to a spinal column of the patient. The fusion plate is inserted into the throat dissection, and the fusion plate is then positioned in on the spinal column. 
         [0010]    In one embodiment a portion of an anterior surface of a first vertebra of the spinal column and a portion of an anterior surface of a second vertebra of the spinal column are contacted by the fusion plate. 
         [0011]    While certain novel features of this invention shown and described below are pointed out in the annexed claims, the invention is not intended to be limited to the details specified, since a person of ordinary skill in the relevant art will understand that various omissions, modifications, substitutions and/or changes in the forms and details of the device illustrated and in its operation may be made without departing in any way from the spirit of the present invention. No feature of the invention is critical or essential unless it is expressly stated as being “critical” or “essential.” 
     
    
     
       FIGURES 
         [0012]      FIG. 1  is a top perspective view of one embodiment of a single level cervical fusion plate. 
           [0013]      FIG. 2  is a bottom perspective view of the fusion plate of  FIG. 1 . 
           [0014]      FIG. 3  is a bottom perspective view of the fusion plate of  FIG. 1 . 
           [0015]      FIG. 4  is a top perspective view of the fusion plate of  FIG. 1  where one of the locking covers is in a locked position and the second locking cover is in an unlocked position. 
           [0016]      FIG. 5  is a bottom perspective view of the fusion plate of  FIG. 4 . 
           [0017]      FIG. 6  is a side perspective view of the fusion plate of  FIG. 1 . 
           [0018]      FIG. 7  is a front perspective view of the fusion plate of  FIG. 1 . 
           [0019]      FIG. 8  is a rear perspective view of the fusion plate of  FIG. 1 . 
           [0020]      FIG. 9  is an anterior perspective view of the fusion plate of  FIG. 1  installed on two vertebrae. 
           [0021]      FIG. 10  is a perspective view from the line  10 - 10  of  FIG. 9 . 
           [0022]      FIG. 11  is a left side perspective view of the fusion plate of  FIG. 9 . 
           [0023]      FIG. 12  is a right side perspective view of the fusion plate of  FIG. 9 . 
           [0024]      FIG. 13  is a top perspective view of the fusion plate of  FIG. 9 . 
           [0025]      FIG. 14  is another perspective view from the line  10 - 10  of  FIG. 9 . 
           [0026]      FIG. 15  is a top view of the fusion plate of  FIG. 1  where the locking covers have been removed for clarity. 
           [0027]      FIG. 16  is a top view of an alternative fusion plate for two levels where the locking covers have been removed for clarity. 
           [0028]      FIG. 17  is a top view of an alternative fusion plate for three levels where the locking covers have been removed for clarity. 
           [0029]      FIG. 18  is a top view of an alternative fusion plate for four levels where the locking covers have been removed for clarity. 
           [0030]      FIG. 19  is a top view of a locking cover. 
           [0031]      FIG. 20  is a top view of the fusion plate of  FIG. 15  showing the locking covers in an unlocked position. 
           [0032]      FIG. 21  is a top view of an alternative fusion plate of  FIG. 16  for two levels showing the locking covers in an unlocked position. 
           [0033]      FIG. 22  is a top view of an alternative fusion plate of  FIG. 17  for three levels showing the locking covers in an unlocked position. 
           [0034]      FIG. 23  is a top view of an alternative fusion plate of  FIG. 18  for four levels showing the locking covers in an unlocked position. 
           [0035]      FIG. 24  is a top view of the fusion plate of  FIG. 15  now showing the locking covers in a locked position. 
           [0036]      FIG. 25  is a top view of an alternative fusion plate of  FIG. 16  for two levels now showing the locking covers in a locked position. 
           [0037]      FIG. 26  is a top view of an alternative fusion plate of  FIG. 17  for three levels showing the locking covers in a locked position. 
           [0038]      FIG. 27  is a top view of an alternative fusion plate of  FIG. 18  for four levels showing the locking covers in a locked position. 
           [0039]      FIG. 28  is a side view of a installation tool which can be used to lock and unlock the locking covers. 
           [0040]      FIG. 29  is a bottom view of the tip of the installation tool 
       
    
    
     DETAILED DESCRIPTION 
       [0041]      FIG. 9  shows an anterior perspective view of a cervical fusion apparatus  10 . The cervical fusion apparatus  100  can include includes a cervical fusion plate  100  which is attached to cervical spinal column  20 . Spinal column  20  includes a plurality of vertebrae  30  (such as vertebra  31 ,  32 ,  33 ,  34 ). The drawings will show fusion plates which can be used for fusing one, two, three, or four levels. 
         [0042]    In one embodiment anterior cervical locking plate  100  is provided. Plate  100  can be used for a single level fusion (two adjacent vertebra). Plate  200  can be used for a two level fusion (three adjacent vertebrae). Plate  300  can be used for a three level fusion (four adjacent vertebrae). Plate  400  can be used for a four level fusion (five adjacent vertebrae). 
         [0043]    However, the description will describe in detail only the plate  100  for a one level system; as the construction and operation of the fusion plates for additional levels are similar with a repetition of the individual components of the fusion plate for each additional level. 
         [0044]    Each vertebra  31 ,  32 ,  33 ,  34 , etc., has an anterior surface substantially centered about the midline sagittal plane. Cervical fusion plate  100  can be adapted to simultaneously engage a plurality of vertebrae (e.g.,  32  and  33 ) of the spinal column  20  to retain the engaged vertebrae in a desired relationship (and the engaged vertebrae need not be adjacent). However, in the interest of simplicity only a two level fusion system will be shown installed. 
         [0045]    The construction of cervical locking plate  100  will be generally described. Plate  100  can have a generally linear form with an overall shape of a parallelogram (such as a rectangle) with rounded corners. However, additional shapes of cervical fusion plate  100  can be used (such as elliptical, rectangular, triangular, etc.). 
         [0046]    Plate  100  can be curved in both the traverse and sagittal planes. Plate  100  can be shaped so that its bottom surface  150  (the surface which will be in contact with the anterior portion of the vertebrae) has a bi-concave curvature, being concave both in the longitudinal plane (corresponding to its length—see arrow  62  in  FIG. 3 ) and in the plane transverse thereto, corresponding to its width (see arrow  52  in  FIG. 3 ). The concave curvature in the longitudinal plane can conform to the proper shape of the anterior aspect of the spine with the vertebrae aligned in appropriate lordosis. Having plate  100  curved in two orthogonal directions (along its length and its width) allows the connecting bone screws to enter the vertebrae at converging angles, and these converging angles of the bone screws are believed to increase the overall stability of fusion plate  100  and the anchored vertebrae (allowing for a better overall fusion between the anchored vertebrae). 
         [0047]    In one embodiment that longitudinal curve can be an arc along the circumference of a circle (referred to herein as the “radius of curvature”) which is typically 15.0 centimeters to 30.0 centimeters in radius, and more preferably 20.0-25.0 centimeters. 
         [0048]    In one embodiment, plate  100  can have has a radius of curvature of between 15 to 25 millimeters, preferably between 19-21 millimeters. In one embodiment, plate  100  can have a thickness between 2 to 3 millimeters, preferably between 2.25 and 2.5 millimeters. In one embodiment, the curvature of plate  100  conforming closely to the surface of the anterior cervical spine reduces the amount of projection of plate  100  from the anterior of the spinal column  20 , reduces the risk that soft tissue will slide underneath the plate&#39;s edges, and reduces the risk of damage. 
         [0049]    Various portions of cervical fusion plate  100  can be removed from its overall shape (e.g., portions  102 ,  103 ,  104 ,  105 , and  106 ). Removal of these portions can decrease the overall size of plate  100  along with increasing the opacity of plate  100  to subsequent investigative and/or viewing techniques. Such increased opacity to X-rays or other investigative techniques can allow for better viewing and tracking of the progress of the overall fusion. For example, as will be described below viewing window  106  can be provided in the approximate position of the middle of the two vertebrae to be fused. This window  106  can allow a post surgery investigative technique which can view the overall progress of the fusion such as be looking at the connection point or points between upper and lower vertebrae being fused. 
         [0050]    Plate  100  can include connecting fastener openings  180 ,  182 ,  184 , and  186 , which can be circular. These openings can be recessed so that screw heads are flush with the surface of plate  100 . Alternatively, these openings may have any suitable configuration, such as substantially round holes, elongated slots, or open-sided notches in fusion plate  100 . These openings may be filleted, chamfered, countersunk, or otherwise shaped to accept the corresponding fasteners, respectively, in a snug mating relationship and optionally prevent any portion of the fastener, such its fastener head, from protruding from plate  100  once implantation is complete. 
         [0051]    In one embodiment screw openings  180 ,  182 ,  184 , and  186 , can be shaped to guide a screw into a predetermined angular relationship with one or more of the other screws. The angular placements of the screws with respect to the cervical fusion plate  100  and/or the vertebrae may be determined by one of ordinary skill in the art, but should be chosen to engage the plate  100  and the vertebrae together to retain the vertebrae in the desired spatial relationship while accommodating individual patient anatomy. Alternatively, the longitudinal axes the screws can form a converging angle in the transverse plane. 
         [0052]    Each screw may be of any suitable type (e.g., bolt, screw, spike, barbed rod, adhesive/peg, or the like). The screws used in any one plate are preferably of the same type and size, however, they need not be matched in type, size, material, position, or any other characteristic and may be readily selected as desired by one of ordinary skill in the art. 
         [0053]    Preferably, the screw openings may have anchoring structures associated with such openings. In one embodiment cervical fusion plate  100  can include one or more rotating locking covers or plates  500 ,  600 . Rotating locking covers can be pivotally connected to plate  100  at rotation points  510 ,  610 . 
         [0054]    In one embodiment locking covers  500  and  600  can be flushly mounted on plate  100  (respectively in recesses  502  and  602 ). Locking cover  500  can fit inside recess  106  to enable cover plate  500  to be flush with the top surface of plate  100 . Cover plate  500  can include first end  520  and second end  530 . As shown in  FIG. 15 , pivot points  510  and  610  can be located on a centerline respectively between openings  180 / 182  and  184 / 186 . Additionally, pivot points  510  and  610  can be located on a centerline passing through the longitudinal center of window or cutout  106 . 
         [0055]    Arrows  504 ,  604  schematically indicate the ability of locking cover  500  to rotate relative to plate  100 . In a first position locking cover  500  does not block a portion of any of the holes such as  180  an  182 . However, in a second position locking cover rotates to block a portion of holes  180  and  182 . Locking covers  500  and  600  can be pivotally connected to plate  100  such that friction tends to lock or resist movement of covers relative to plate  100  (and a substantial force is required to rotate such locking covers). 
         [0056]      FIGS. 1 and 24  are top views of plate  100  with locking covers  500  and  600  rotated such that they are in a locked position.  FIG. 20  is a top view showing locking covers  500  and  600  in an unlocked position.  FIG. 15  is a top view where all locking covers have been removed. As shown in  FIGS. 1 ,  15 ,  20 , and  24 , locking covers in the unlocked position extend outside of the body of plate  100 . For example, first side  520  of locking cover  500  extends outside of cutout  105 ; and second side  530  extends into cutout  106 . As another example, second side  630  of locking cover  600  extends outside of cutout  104 ; and first side  620  extends into cutout  106 . However, in the locked positions neither of these covers extends outside of the body of plate  100 . Because of such extension or extensions in the unlocked position, X-rays could determine whether either of these locking covers are in the unlocked position because at least part of the locking cover would show up in the X-ray. Accordingly, such property provides a convenient method of confirming that the locking covers are in a locked position. 
         [0057]    In one embodiment screws can be used to attach plate  100  to upper and lower vertebrae. In one embodiment screws can be bone screws. In one embodiment openings  180 ,  182 ,  184 , and  186  can include recessed areas which allow the heads of screws to be flush with the top surface of plate  100 . 
         [0058]    In one embodiment pivot locations  510  and  610  are large enough to be used as a cervical pin holder. Plate  100  can be temporarily fixed by two cervical pins positioned at points  510  and  610 —which locations are also the pivot points for locking covers  500  and  600 . In one embodiment the method of positioning and holding fixed plate  100  by installing cervical pins first in openings  510  and  610  through the vertebrae, drilling holes in the vertebrae through openings  180 ,  182 ,  184 , and  186  into the vertebrae, installing screws in the vertebra 
         [0059]    In one embodiment a pair of bone screw holes is used for each vertebra to be fused. For example, a plate for a one level fusion would have two pairs of bone screw holes—one in each of the vertebra being fused. As another example, for a two level fusion each of the three vertebra would have a pair of screw holes. For each of these pairs of screw holes the cervical plate can have a pair of openings, and a locking cover which is located in the middle of the paired openings. 
         [0060]    In one embodiment, the bottom surface  150  of plate  100 , preferably has a textured, roughened, and/or porous surface (shown is a ribbed or knurled surface). In one embodiment bottom surface  150  can be coated with, impregnated with, or comprise fusion promoting substances (such as bone morphogenetic proteins) so as to encourage the growth of bone from vertebrae to vertebrae. In one embodiment plate  100  can comprise at least in part a resorbable material which can further be impregnated with the bone growth material so that as plate  100  is resorbed by the body of the patient, the bone growth material is released, thus acting as a time release mechanism. 
         [0061]    As shown in  FIGS. 16-18 ,  21 - 23 , and  25 - 27 , in alternative embodiments, fusion plates  200 ,  300 ,  400  for fusing more than two levels could have additional screw openings corresponding to additional paired bone screw holes. In one embodiment additional locking covers can be provided for each of the paired screw openings. In one embodiment the locking covers are pivotally connected to the plate, and at the point of rotation an opening for a positioning pin can be found. 
         [0062]      FIG. 16  is a top view of an alternative fusion plate  200  for two levels where the locking covers have been removed for clarity.  FIG. 21  is a top view of fusion plate  200  for two levels showing the locking covers ( 500 ,  600 ,  700 ) in an unlocked position.  FIG. 25  is a top view of fusion plate  200  for two levels now showing the locking covers ( 500 ,  600 ,  700 ) in a locked position. In the unlocked position it can be noticed that at least part of the locking covers will be visible though an opening (e.g.,  106  or  106 ′) and/or through a cutout (e.g.,  102 ,  104 ′). 
         [0063]      FIG. 17  is a top view of an alternative fusion plate  300  for three levels where the locking covers have been removed for clarity.  FIG. 22  is a top view of fusion plate  300  for three levels showing the locking covers ( 500 ,  600 ,  700 ,  800 ) in an unlocked position.  FIG. 26  is a top view of fusion plate  300  now showing the locking covers ( 500 ,  600 ,  700 ,  800 ) in a locked position. In the unlocked position it can be noticed that at least part of the locking covers will be visible though an opening (e.g.,  106 ,  106 ′,  106 ″) and/or through a cutout (e.g.,  102 ,  104 ″). 
         [0064]      FIG. 18  is a top view of an alternative fusion plate  400  for four levels where the locking covers have been removed for clarity.  FIG. 23  is a top view of fusion plate  400  for four levels showing the locking covers ( 500 ,  600 ,  700 ,  800 ,  900 ) in an unlocked position.  FIG. 27  is a top view of fusion plate  400  for four levels now showing the locking covers ( 500 ,  600 ,  700 ,  800 ,  900 ) in a locked position. In the unlocked position it can be noticed that at least part of the locking covers will be visible though an opening (e.g.,  106 ,  106 ′,  106 ″,  106 ′″) and/or through a cutout (e.g.,  102 ,  104 ″′). 
         [0065]      FIG. 28  is a side view of a installation tool  1000  which can be used to lock and unlock the locking covers (e.g.,  500 ,  600 ).  FIG. 29  is a bottom view of the tip or second end  1020  of the installation tool  1000 . Installation tool  1000  can include first end  1010 , second end  1020 , and body  1030 . On second end or tip can be included first and second projections  1100 ,  1110 . First and second projections  1100  and  1110  can fit around the middle portion of the locking covers such as locking cover  500  (and between first and second ends  520 ,  530  of locking cover  500 ) such on opposite sides of the pivot point  510  of locking cover. 
         [0066]    Projections  1100  and  1110  can have a shape which fits the locking covers (e.g.,  500 , 600 ) tool  1000  turns. Because locking covers (e.g.,  500 , 600 ) have an “hour glass” shape, projections  1100  and  1110  can have curved internal surfaces to match the hour glass shape of projections. Projections  1100  and  1110  are believed to be self centering over locking covers (because the shape of locking covers match the interior shape of projections). However, various other mechanisms can be used to assist in positioning and/or centering tool  1100  over a locking cover. 
         [0067]    Shown in this embodiment is a recessed area  1060  which is designed to accept the raised area around the pivot points of any locking cover (e.g., pivot point  510  of locking cover  500 ), which centers tool  1000  around the pivot point and the locking cover. Also shown in this embodiment is central opening  1050  extending from first end  1010  to second end  1020  of body  1030 . Central opening  1050  allows the used of a centering tool such as a centering rod or wire to be placed through body  1030  and enter the pivot point (e.g., pivot point  510  of locking cover  500 ) of the locking cover to be locked or unlocked to center tool  1000  over such locking cover. Alternatively, recessed area  1060  and central opening can be constructed to accept a cervical positioning pin which was placed in the pivot point (e.g., pivot point  510  of locking cover  500 ) so that the positioning pin centers tool  1000 . Also alternatively, a cervical positioning pin can be installed in a cervical plate while tool  1000  is installed on a locking cover (e.g., pivot point  510  of locking cover  500 ). 
         [0068]    In an alternative embodiment a middle projection or pointer can replace recessed area  1060  where the middle projection or pointer would enter the pivot point of the locking cover (e.g., pivot point  510  of locking cover  500 ) which would center the tool over locking cover. In another alternative embodiment tips  1100  and  1110  can be increased in length so that the raised portion of the pivot point (e.g., pivot point  510  of locking cover  500 ) of a locking cover is less than the length of the projections—otherwise, if such was not the case, the raised portion interfere with the projections interlocking with the locking cover to be locked or unlocked. 
         [0069]    In use projections  1100  and  1110  of tool  1000  are placed over a locking cover to be locked and turned (causing the locking cover to turn) to a locked position (locked positions are shown in  FIGS. 24 through 27 ). Additionally, projections  1100  and  1110  of tool  1000  can be placed over a locking cover to be unlocked and turned (causing the locking cover to turn) to an unlocked position (unlocked positions are shown in  FIGS. 20 through 23 ). 
       Surgical Method for a Single Level Fusion 
       [0070]      FIGS. 9 through 14  show plate  100  affixed to cervical vertebrae  31  and  32 . In these figures locking covers  500  and  600  have been removed to be able to view the bone screws in openings  180 , 182 , 184 , and  186 . 
         [0071]    When the cervical fusion apparatus  10  is implanted in a patient, a surgeon dissects the patient&#39;s throat below the patient&#39;s chin to access the cervical spinal column  20  of the patient. Optionally, the throat dissection may be done asymmetrically with respect to the throat to minimize invasion of the throat while positioning the cervical fusion plate  100  in the desired relationship with the cervical spinal column  20 . The surgeon then inserts the cervical fusion plate  100  into the throat dissection and maneuvers the cervical fusion plate  100  around the larynx and other throat structures to a position near the spinal column  20 . The size or shape of the cervical fusion plate  100  may be chosen to minimize damage or irritation to the patient&#39;s throat during implantation while maintaining strength to retain the vertebrae (e.g.,  31  and  32 ) in the desired relationship after implantation. 
         [0072]    Once the cervical fusion plate  100  is located near the spinal column  20 , the surgeon positions the cervical fusion plate  100  on the cervical spinal column  20 . The surgeon contacts a portion of the anterior surface of a first vertebra (e.g.,  31 ) and a side portion of the anterior surface of a second vertebra (e.g.,  32 ) with the cervical fusion plate  100 . 
         [0073]    The surgeon uses cervical positioning pins in openings  510  and  520  to hold the cervical fusion plate  100  in engagement with the vertebrae (e.g.,  31  and  32 ) while drilling or tapping reception holes in the vertebrae to receive the fasteners or bone screws. These reception holes should match the openings for the fasteners (e.g.,  180 ,  182 ,  184 , and  186 ) for precise implantation of the cervical fusion apparatus  100 . Alternately, the vertebrae (e.g.,  31  and  32 ) could be prepared with such reception holes before the cervical fusion plate  100  becomes engaged with the vertebrae. However, if the fasteners are self-tapping, the surgeon need not prepare reception holes but instead might drill small pilot holes or even just initially penetrate the anterior surface of the vertebrae directly with the fasteners to be installed. 
         [0074]    Once the cervical fusion plate  100  has been positioned as desired and the vertebrae (e.g.,  31  and  32 ) have been prepared as needed to accept the fasteners, the surgeon inserts the fasteners through the holes ( 180  and  182 ) and into the first vertebra (e.g.,  31 ). The surgeon also inserts fasteners through a second fastener openings ( 184  and  186 ) and into the second vertebra (e.g.,  32 ). Once these fasteners have been tightened and anchored as desired, the cervical fusion apparatus  100  is operative to retain the engaged vertebrae (e.g.,  31  and  32 ) in the desired spatial relationship. 
         [0075]    The surgeon can use tool  1000  to lock locking covers  500  and  600  over the fasteners. Projections  1100  and  1110  connect to locking cover  500  and can be turned to a locked position. Projections  1100  and  1110  connect to locking cover  600  and can be turned to a locked position. Locking covers  500  and  600  now resist loosening of the fasteners in openings  180 ,  182 ,  184 , and  186 . 
         [0076]    When all of the desired fasteners have been implanted to the surgeon&#39;s satisfaction, all tools are removed from the throat dissection and the patient&#39;s throat is closed in a known manner. 
         [0077]    The method and apparatus of certain embodiments of the present invention, when compared with other apparatus and methods, may have the advantages of: being useful in a minimally invasive surgical procedure, allowing the patient&#39;s throat structures to remain largely in place during the operation, being usable in a timely and efficient manner, and being more economical to manufacture and use. Such advantages are particularly worthy of incorporating into the design, manufacture, and operation of a cervical fusion apparatus  10 . In addition, the present invention may provide other advantages which have not yet been discovered. 
         [0078]    Some of the perceived advantages of fusion plates  100 ,  200 ,  300 , and  400  are as follows: 
         [0079]    (A) Plate profile and graft window allow for good visibility of graft; 
         [0080]    (B) Pre-curved plate reduces the amount of possible bending needed during the surgical procedure; 
         [0081]    (C) Due to the location of anti-migration locking covers allows for a reduction of the risk of damage to the locking covers and/or too large of play between locking covers and screws being constrained. That is, if the pivot points were moved and the plate bent, an excessive gap could occur between the locking cover and the screw being held by the locking cover; 
         [0082]    (D) The pivot point of a locking cover also being used as an insertion point for a cervical pin holder, allows for the use of a temporary plate holding pin during initial installation; and 
         [0083]    (E) Easy to use locking covers allows surgeon to easily remove existing 4 millimeter bone screws and install 4.5 millimeter recovery screws if necessary for a fusion. 
         [0084]    Some non-limiting examples of plate features include a precurved plate body in both the traverse and sagittal planes; graft window; capability of accepting fixed and variable angle screws; uses 4 millimeter bone screws and 4.5 millimeter recovery screws; easy to use anti-migration locking covers with a hole through the cover and plate for use of a plate holding pin. 
         [0085]    While aspects of the present invention have been particularly shown and described with reference to the preferred embodiment above, it will be understood by those of ordinary skill in the art that various additional embodiments may be contemplated without departing from the spirit and scope of the present invention. For example, the elements of the present invention could be made of any variety or combinations of materials, though preferably all chosen materials are biocompatible; the fasteners could be angled differently than described; the fasteners could be inserted in a different order than described, the cervical fusion plate  100  could include various contours, apertures, or other shaping providing advantages in strength, weight, infection-resistance, cost, or the like; any desired number of addition/different vertebrae could be engaged with the cervical fusion plate  100 ; or the engaged vertebrae need not be adjacent. 
         [0086]    The following is a list of reference numerals: 
         [0000]    
       
         
               
             
               
               
             
               
               
             
           
               
                   
               
               
                 LIST FOR REFERENCE NUMERALS 
               
             
          
           
               
                 (Ref No.) 
                 (Description) 
               
               
                   
               
             
          
           
               
                 10 
                 cervical fusion apparatus 
               
               
                 15 
                 patient 
               
               
                 20 
                 cervical spinal column 
               
               
                 30 
                 plurality of vertebrae 30 
               
               
                 31 
                 vertebra 
               
               
                 32 
                 vertebra 
               
               
                 33 
                 vertebra 
               
               
                 34 
                 vertebra 
               
               
                 50 
                 line or axis 
               
               
                 52 
                 arrow 
               
               
                 60 
                 line or axis 
               
               
                 62 
                 arrow 
               
               
                 100 
                 cervical fusion plate 
               
               
                 102 
                 portion 
               
               
                 103 
                 portion 
               
               
                 104 
                 portion 
               
               
                 105 
                 portion 
               
               
                 110 
                 viewing window 
               
               
                 150 
                 bottom surface 
               
               
                 160 
                 upper surface 
               
               
                 180 
                 screw opening 
               
               
                 182 
                 screw opening 
               
               
                 184 
                 screw opening 
               
               
                 186 
                 screw opening 
               
               
                 200 
                 cervical fusion plate for two level fusion 
               
               
                   
                 (three adjacent vertebrae) 
               
               
                 300 
                 cervical fusion plate for three level fusion 
               
               
                   
                 (four adjacent vertebrae) 
               
               
                 400 
                 cervical fusion plate for four level fusion 
               
               
                   
                 (five adjacent vertebrae). 
               
               
                 500 
                 locking cover 
               
               
                 502 
                 recessed area 
               
               
                 504 
                 arrow 
               
               
                 510 
                 pivot point or opening for positioning pin 
               
               
                 520 
                 first end 
               
               
                 530 
                 second end 
               
               
                 600 
                 locking cover 
               
               
                 602 
                 recessed area 
               
               
                 604 
                 arrow 
               
               
                 610 
                 pivot point or opening for positioning pin 
               
               
                 620 
                 first end 
               
               
                 630 
                 second end 
               
               
                 632 
                 arrow 
               
               
                 634 
                 arrow 
               
               
                 700 
                 locking cover 
               
               
                 702 
                 recessed area 
               
               
                 710 
                 pivot point or opening for positioning pin 
               
               
                 720 
                 first end 
               
               
                 730 
                 second end 
               
               
                 800 
                 locking cover 
               
               
                 802 
                 recessed area 
               
               
                 810 
                 pivot point or opening for positioning pin 
               
               
                 820 
                 first end 
               
               
                 830 
                 second end 
               
               
                 900 
                 locking cover 
               
               
                 902 
                 recessed area 
               
               
                 910 
                 pivot point or opening for positioning pin 
               
               
                 920 
                 first end 
               
               
                 930 
                 second end 
               
               
                 1000 
                 installation tool 
               
               
                 1010 
                 first end 
               
               
                 1020 
                 second end or tip 
               
               
                 1030 
                 body 
               
               
                 1050 
                 central bore 
               
               
                 1060 
                 recessed area 
               
               
                 1100 
                 first projection 
               
               
                 1110 
                 second projection 
               
               
                   
               
             
          
         
       
     
         [0087]    All measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise. All materials used or intended to be used in a human being are biocompatible, unless indicated otherwise. 
         [0088]    It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention set forth in the appended claims. The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.