Patent Publication Number: US-9848994-B2

Title: Low profile plate

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part application of U.S. Ser. No. 14/190,948, filed Feb. 26, 2014, which is a continuation-in-part application of U.S. Ser. No. 13/785,434, filed Mar. 5, 2013 and of U.S. Ser. No. 14/085,318, filed Nov. 20, 2013, which is a continuation-in-part application of U.S. patent application Ser. No. 13/785,856, filed Mar. 5, 2013, which is a continuation-in-part of U.S. patent application Ser. No. 13/559,917, filed Jul. 27, 2012, which is a continuation-in-part of Ser. No. 13/267,119, filed Oct. 6, 2011, which claims priority to U.S. Provisional Application 61/535,726, filed on Sep. 16, 2011, the entire contents of which are incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present application is generally directed to orthopedic systems, and in particular, to systems including plates and spacers. 
     BACKGROUND 
     Spinal discs and/or vertebral bodies of a spine can be displaced or damaged due to trauma, disease, degenerative defects, or wear over an extended period of time. One result of this displacement or damage may be chronic back pain. In some cases, to alleviate back pain, the disc can be removed and replaced with an implant, such as a spacer, that promotes fusion. In addition to providing one or more spacers, a plating system can be used to further stabilize the spine during the fusion process. Such a plating system can include one or more plates and screws for aligning and holding vertebrae in a fixed position with respect to one another. 
     Accordingly, there is a need for improved systems involving plating systems and spacers for spinal fusion and stabilization. 
     SUMMARY OF THE INVENTION 
     Various systems, devices and methods related to plating systems are provided. In some embodiments, a spinal system comprises a spacer for inserting into an intervertebral space and a plate configured to abut the spacer. The spacer can include an upper surface, a lower surface and an opening that extends between the upper surface to the lower surface, wherein the spacer further includes a tapered leading end. The plate for abutting the spacer can include a plate body, a first opening formed in the plate body for receiving a first bone screw, a second opening formed in the plate body for receiving a second bone screw, a set screw, and a pair of extensions that extend from the plate body that are configured to engage the spacer. The first opening can angled in an upward direction, while the second opening can be angled in a downward direction. The set screw can be configured to prevent back-out of both the first and the second bone screws, wherein the set screw has a first position whereby the first and second bone screws can be inserted past the set screw and into the first and second openings and a second position following rotation of the set screw whereby the first and second bone screws are prevented from backing out by the set screw. A first bone screw is provided for inserting into the first opening in the plate body, wherein the first bone screw is configured to be inserted into a first vertebral body. A second bone screw is provided for inserting into the second opening in the plate body, wherein the second bone screw is configured to be inserted into a second vertebral body different from the vertebral body. 
     In other embodiments, a spinal system comprises a spacer for inserting into an intervertebral space and a plate configured to abut the spacer. The spacer can include an upper surface, a lower surface and an opening that extends between the upper surface to the lower surface, wherein the spacer further includes a concave leading end. The plate for abutting the spacer can include a plate body, a first opening formed in the plate body for receiving a first bone screw, a second opening formed in the plate body for receiving a second bone screw, a set screw, and a pair of extensions that extend from the plate body that are configured to engage the spacer. The first opening can angled in an upward direction, while the second opening can be angled in a downward direction. The set screw can be configured to prevent back-out of at least one of the first and the second bone screws, wherein the set screw has a first position whereby at least one of the first and second bone screws can be inserted past the set screw and into at least one of the first and second openings and a second position following rotation of the set screw whereby at least one of the first and second bone screws are prevented from backing out by the set screw. Each of the pair of extensions can include a window that extends along a length of the extension. A first bone screw is provided for inserting into the first opening in the plate body, wherein the first bone screw is configured to be inserted into a first vertebral body. A second bone screw is provided for inserting into the second opening in the plate body, wherein the second bone screw is configured to be inserted into a second vertebral body different from the vertebral body. 
     In some embodiments, a spinal system comprises a spacer for inserting into an intervertebral space and a plate configured to abut the spacer. The spacer can include an upper surface, a lower surface and an opening that extends between the upper surface to the tower surface. The plate for abutting the spacer can include a plate body, a first opening formed in the plate body for receiving a first bone screw, a second opening formed in the plate body for receiving a second bone screw, a set screw, and a pair of extensions that extend from the plate body that are configured to engage the spacer. The first opening can angled in an upward direction, while the second opening can be angled in a downward direction. The set screw can be configured to prevent back-out of at least one of the first and the second bone screws, wherein the set screw has a first position whereby at least one of the first and second bone screws can be inserted past the set screw and into at least one of the first and second openings and a second position following rotation of the set screw whereby at least one of the first and second bone screws are prevented from backing out by the set screw. Each of the pair of extensions can include a window that extends along a length of the extension. A first bone screw is provided for inserting into the first opening in the plate body, wherein the first bone screw is configured to be inserted into a first vertebral body. A second bone screw is provided for inserting into the second opening in the plate body, wherein the second bone screw is configured to be inserted into a second vertebral body different from the vertebral body. The spacer and the plate are independent from one another such that the spacer can be inserted into a desired spinal location prior to abutting the spacer with the plate. 
    
    
     
       BRIEF DESCRIPTION OF TUE DRAWINGS 
         FIGS. 1A-1D  illustrate different views of a low profile plate attached to a spacer according to some embodiments. 
         FIGS. 2A-2D  illustrate different views of the low profile plate shown in  FIGS. 1A-1D . 
         FIGS. 3A-3D  illustrate different views of a PEEK spacer to be used with the low profile plate shown in  FIGS. 2A-2D . 
         FIGS. 4A-4D  illustrate different views of an allograft spacer to be used with the low profile plate shown in  FIGS. 2A-2D . 
         FIGS. 5A-5D  illustrate different views of a second alternative embodiment of a tow profile plate attached to a spacer according to some embodiments. 
         FIGS. 6A-6D  illustrate different views of the low profile plate shown in  FIGS. 5A-5D . 
         FIGS. 7A-7D  illustrate different views of a PEEK spacer to be used with the low profile plate in  FIGS. 6A-6D . 
         FIGS. 8A-8D  illustrate different views of an allograft spacer to be used with the low profile plate in  FIGS. 6A-6D . 
         FIGS. 9A-9D  illustrate different views of a third alternative embodiment of a low profile plate attached to a spacer according to some embodiments. 
         FIGS. 10A-10D  illustrate different views of the low profile plate shown in  FIGS. 9A-9D . 
         FIGS. 11A-11D  illustrate different views of a fourth alternative embodiment of a low profile plate attached to a spacer according to some embodiments. 
         FIGS. 12A-12D  illustrate different views of the low profile plate shown in  FIGS. 11A-11D . 
         FIGS. 13A-13D  illustrate different views of a multi-piece allograft spacer to be used with the low profile plates discussed above according to some embodiments. 
         FIGS. 14A-14D  illustrate different views of an alternative multi-piece allograft spacer to be used with the tower profile plates discussed above according to some embodiments. 
         FIGS. 15A-15D  illustrate different views of an alternative low profile plate attached to a spacer according to some embodiments. 
         FIGS. 16A-16D  illustrate different views of a low profile plate shown in  FIGS. 15A-15D . 
         FIGS. 17A-17C  illustrate different views of a spacer shown in  FIGS. 15A-15D . 
         FIGS. 18A-18D  illustrate different views of another alternative low profile plate attached to a spacer according to some embodiments. 
         FIG. 19  illustrates a lordotic version of the low profile plate and spacer shown in  FIGS. 18A-18D . 
         FIGS. 20A-20D  illustrate different views of another alternative low profile plate attached to multiple spacers according to some embodiments. 
         FIGS. 21A and 21B  illustrate different views of another alternative low profile plate attached to multiple spacers according to some embodiments. 
         FIG. 22  illustrates another alternative low profile plate attached to multiple spacers according to some embodiments. 
         FIG. 23  illustrates another alternative low profile plate attached to multiple spacers according to some embodiments. 
         FIGS. 24A-24C  illustrate another alternative low profile plate attached to a multi-piece spacer having three pieces according to some embodiments. 
         FIGS. 25A and 25B  illustrate another alternative low profile plate attached to a multi-piece spacer having a metal insert according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     The present application is generally directed to orthopedic systems, and in particular, to systems including plates and spacers. 
     The present application discloses orthopedic plating systems that can be used in spinal surgeries, such as spinal fusions. The plating systems disclosed herein include a plate and a spacer that are independent from one another. In some cases, the plate and the spacer can be pre-attached to one another before positioning them in a desired location of the spine. In other cases, the spacer can first be inserted into a desired location of the spine, and then the plate can be inserted thereafter. Advantageously, the plating systems disclosed herein are of low-profile. For example, they can provide a very small, anterior footprint cervical plate solution for fusion procedures. One skilled in the art will appreciate that while the plating systems can be used with cervical procedures, the plating systems are not limited to such areas, and can be used with other regions of the spine. 
       FIGS. 1A-1D  illustrate different views of a plating system comprising a low profile plate attached to a spacer according to some embodiments. The plating system  5  includes a spacer  10  attached to a low-profile plate  50 . Advantageously, the plating system  5  can be inserted through an anterior approach into a spine, and can desirably provide a small anterior footprint. 
     The spacer  10  is configured to have an upper surface  12 , a lower surface  14 , and a leading end  22 . In some embodiments, the upper surface  12  and/or lower surface  14  includes texturing  16 , such as teeth, ribs, ripples, etc. to assist in providing frictional contact with adjacent vertebral bodies. In some embodiments, the leading end  22  of the spacer  10  can be slightly tapered, as shown in  FIG. 1A . With the taper, the leading end  22  can serve as a distraction surface that helps the spacer to be inserted into an intervertebral space. As shown in  FIG. 1B , the leading end  22  can be concave, though in other embodiments, the leading end  22  can be straight or convex. 
     The spacer  10  can be substantially C-shaped (as shown in  FIG. 3B ), whereby it includes two side arms  13  that surround an inner opening  20 . Adjacent the side arms  13  is a convex wall  19 . In some embodiments, the convex wall  19  is substantially parallel to the concave surface of the leading end  22 . The opening  20 , which is configured to receive natural or synthetic graft material therein to assist in a fusion procedure, has an open side that is opposite convex wall  19 , thereby giving the spacer  10  its C-shape. 
     The spacer  10  has a number of unique features that accommodate the attachment of a plate  50  thereto. Each of the side arms  13  of the spacer  10  includes a notch  17  (shown in  FIG. 3B ) for receiving a corresponding protrusion  71  of a lateral arm or extension  70  of the plate  50 , thereby advantageously forming a first locking mechanism between the spacer  10  and the plate  50 . In addition, in some embodiments, each of the side arms  13  of the spacer  10  can also include a hump region  26  (shown in  FIG. 3B ) that can extend in part into a window  72  of an attached plate  50  (shown in  FIG. 2A ), thereby advantageously providing a second locking mechanism between the spacer  10  and the plate  50 . Advantageously, by providing secure first and second locking mechanisms between the spacer  10  and the plate  50 , the plate and spacer will be kept securely together during any type of impaction of the plating system within the body. Furthermore, each of the side arms  13  of the spacer  10  can include a cut-away portion or chamfer  18 ,  19  (shown in  FIG. 3C ) to advantageously accommodate screws which pass through the plate. In embodiments that involve a pair of screws through the plate  50 —one of which passes in an upward direction, and the other of which passes in a downward direction—one side arm  13  of the spacer  10  will include an upper chamfer  18  formed on an upper surface to accommodate the upwardly directed screw, while the second side arm  13  of the spacer will include a lower chamfer  19  formed on a lower surface to accommodate the downwardly directed screw. 
     The spacer  10  can be formed of any material. In some embodiments, the spacer  10  is formed of a polymer, such as PEEK, as shown in  FIG. 3A . In some embodiments, the spacer  10  is formed of allograft bone, as shown in  FIG. 4A . In some instances, to form an allograft implant, allograft bone may be cut or shaved from a desired bone member. The cut allograft bone will then be assembled together, using an adhesive or mechanical fastener (e.g., bone pins). Accordingly, in some embodiments, an allograft spacer  10  is formed of two, three, four or more layers that are assembled together, such as by one or more bone pins. One particular advantage of the invention is that the plate  50  can work with a variety of different spacers  10 , as the plate  50  is independently removable from and attachable to the spacer  10 . Regardless of whether a surgeon chooses to implant an allograft spacer or PEEK spacer  10  into an intervertebral space, the surgeon can simply attach the low-profile plate  50  to the spacer  10  following implantation into the intervertebral space. 
     The plate  50  is configured to have a plate body and a pair of lateral extensions  70  that extend from the plate body, each of which has a protrusion  71 , for inserting into a corresponding notch  17  of the spacer  10 . These lateral extensions  70  help form the first locking mechanism between the plate  50  and the spacer  10 , as discussed above. In addition, the lateral extensions  70  of the plate  50  each include a window  72  (shown in  FIG. 2A ) for receiving a hump region  26  on the arms  17  of the spacer  10 , thereby helping to form the second locking mechanism between the plate  50  and the spacer  10 , as discussed above. 
     In addition to attaching to the spacer  10 , the plate  50  is also configured to attach into one or more vertebral bodies via one or more bone screws. As shown in  FIG. 1A , the plate  50  includes a first screw hole  52  and a second screw hole  54  for receiving bone screws therein. In some embodiments, screw hole  52  is angled upwardly such that an inserted bone screw passes upward into an upper vertebral body, while screw hole  54  is angled downwardly such that an inserted bone screw passes downward into a tower vertebral body. White the illustrated embodiment illustrates a pair of screw holes for receiving a pair of bone screws, it is possible to have one, three, four, five or more screw holes for receiving a different number of bone screws. 
     Over time, it is possible for bone screws to back-out. The plate  50  thus has a blocking or set screw  56  (shown in  FIG. 1C ) that assists in preventing back-out of inserted bone screws. As shown in  FIG. 1C , the set screw  56  can be in an initial position that allows first and second bone screws to pass through holes  52 ,  54 . Once the bone screws have been inserted through the holes  52 ,  54 , the set screw  56  can be rotated (e.g., 90 degrees), to thereby block the bone screws and prevent back out of the bone screws. In some embodiments, the set screw  56  abuts a side of the head of the bone screws to prevent back-out of the bone screws, while in other embodiments, the set screw  56  rests over a top of the head of the bone screws to prevent back-out of the bone screws. In some embodiments, the set screw  56  comes pre-fixed with the plate  50 . As shown in  FIG. 1C , a single set screw  56  can be used to conveniently block a pair of bone screws. In other embodiments, each bone screw can be assigned its own set screw, which can operate independently of one another, to prevent back-out of the bone screw. 
     The plate  50  can also include one or more knife-like edges  63  that provide additional torsional stabilization when the plate  50  rests against a bone member. As shown in  FIG. 1C , the knife-like edges  63  can be formed on both the upper and lower surfaces of the plate  50  body. While the illustrated embodiment shows a pair of knife-like edges  63  on an upper surface of the plate body and a pair of knife-like edges  63  on a lower surface of the plate body, one skilled in the art will appreciate that a different number of knife-like edges  63  can be provided. 
       FIGS. 2A-2D  illustrate different views of the low profile plate shown in  FIGS. 1A-1D . From these views, one can see the pair of lateral extensions  70  that extend from the body of the plate  50 . At the distal end of each of the lateral extensions  70  is an inwardly-facing protrusion  71  that is configured to fit into a corresponding notch in the spacer  10 . In addition, from these views, one can see the windows  72  that are formed in each of the lateral extensions  70 . The windows  72  advantageously receive hump regions  26  of the spacer to provide a locking mechanism, and also help to improve desirable radiolucency. Advantageously, the windows  72  can have rounded edges to accommodate the spacer  10  therein. While the illustrated windows  72  are shown as rectangular with rounded edges, in other embodiments, the windows  72  can have a different shape, such as circular or oval. In some embodiments, the plate  50  is assembled axially to the spacer  10 . 
     In some embodiments, the low profile plate  50  can also include indented gripping sections  73  (shown in  FIGS. 2A and 2B ). These indented gripping sections  73  advantageously provide a gripping surface for an insertion instrument, thereby facilitating easy delivery of the plate to a spacer body during surgery. 
       FIGS. 3A-3D  illustrate different views of a PEEK spacer to be used with the low profile plate shown in  FIGS. 2A-2D . From these views, one can see how the spacer  10   a  includes an upper surface  12   a  and a lower surface  14   a  with texturing  16   a ; a generally C-shaped body including a pair of arms  13   a  each having a notch  17   a  formed therein and an upper chamfer  18   u  or lower chamfer  19   a ; and a tapered leading edge  22   a . In addition, one skilled in the art can appreciate the substantially symmetric shape of the inner opening  20   a , which serves as a graft hole for receiving graft material therein. 
       FIGS. 4A-4D  illustrate different views of an allograft spacer to be used with the tower profile plate shown in  FIGS. 2A-2D . While the allograft spacer  10   b  shares similar features to the PEEK spacer  10   a  shown in previous figures, such as the notches  17   b , hump surfaces  26   b , and chamfers  18   b , 19   b , the allograft spacer  10   b  need not be the same. For example, the shape of the graft opening  20   b  can be more of an arch, as shown in  FIG. 4B . 
       FIGS. 5A-5D  illustrate different views of a second alternative embodiment of a low profile plate attached to a spacer according to some embodiments. Rather than having a plate  50  with lateral extensions  70  that extend around the outer surface of a spacer  10 , the present embodiment of the plating system  105  includes a plate  150  with an enclosed posterior extension  155  that fits within the body of the spacer  110 . The enclosed posterior extension  155  includes extending surfaces  166 ,  167  that are fitted into corresponding inlets  121 ,  123  formed in the body of the spacer  120 , thereby forming a first locking mechanism between the plate  150  and the spacer  110 . In addition, the enclosed posterior extension  155  of the plate  50  includes one or more deformable locking tabs  160  (shown in  FIG. 6B ) that securely lock into tab holes  181   a  in the spacer body  110 , thereby forming a second locking mechanism between the plate  150  and the spacer  110 . While in some embodiments, the plate  150  can be attached to the spacer  110  after inserting the spacer  110  into a desired location in the body, in other embodiments, the plate  150  can be pre-assembled with the spacer  110  prior to inserting the plating system  105  into the desired location. 
     Like the spacer  10  in  FIG. 1A , the spacer  110  is configured to have an upper surface  112 , a tower surface  114 , and a leading end  122 . In some embodiments, the upper surface  112  and/or lower surface  114  includes texturing  116 , such as teeth, ribs, ripples, etc. to assist in providing frictional contact with adjacent vertebral bodies. In some embodiments, the leading end  122  of the spacer  110  can be slightly tapered, as shown in  FIG. 7D . With the taper, the leading end  122  can serve as a distraction surface that helps the spacer  110  to be inserted into an intervertebral space. As shown in  FIG. 1B , the leading end  122  can be concave, though in other embodiments, the leading end  122  can be straight or convex. 
     The spacer  110  can be substantially C-shaped (as shown in  FIG. 7B ), whereby it includes two side arms  113  that surround an inner opening  120 . Adjacent the side arms  113  is a straight wall  119  that forms the border of the graft opening  120 . The straight wall  119  can include one or more tab holes  181  (shown in  FIG. 7A ) for receiving deformable tab locks  160  therein. The graft opening  20 , which is configured to receive natural or synthetic graft material therein to assist in a fusion procedure, has an open side that is opposite the straight wall  119 , thereby giving the spacer  110  its C-shape. 
     In some embodiments, the graft opening  120  (shown in  FIG. 7B ) has a different shape from the opening  20  of the spacer  10  of the prior embodiment, as the graft opening  120  is configured to not only receive graft material, but also the enclosed posterior extension  155  of the plate  150 . For example, the graft opening  120  includes two inlets—a first inlet  121  formed at the junction between the first arm  113  and wall  119  and a second inlet  123  formed at the junction between the second arm  113  and wall  119  (shown in  FIG. 7B )—for receiving outwardly extending surfaces  166 ,  167  of the plate  150  (shown in  FIG. 6B ). In addition, the graft opening  120  includes two outwardly tapering walls  111  that provide enough space to accommodate any bone screws inserted in the plate  150 . As such, additional chamfers  18 ,  19  (as shown in  FIG. 313 ) are optional. 
     Like spacer  10 , the spacer  110  can be formed of a variety of materials. In some embodiments, the spacer  110  comprises PEEK, as shown in  FIG. 7A , while in other embodiments, the spacer  110  comprises allograft bone, as shown in  FIG. 8A . 
     The plate  150  is configured to have a plate body, and an enclosed posterior extension  155  that extends from the plate body, which is received within and retains the spacer  110 . The enclosed posterior extension  155  includes first and second outwardly extending surfaces  166 ,  167  that fit into inlets  121 ,  123  formed within the spacer  110  body to form a first locking mechanism. In addition, one or more deformable tab locks  160  extend from an exterior surface of the enclosed posterior extension  155  and are received in corresponding tab holes  181  in the spacer  150  to form a second locking mechanism. In some embodiments, the side walls of the enclosed posterior extension  155  can include one or more windows  172  (shown in  FIG. 6A ) for improving radiolucency of the plating system. In some embodiments, the plate  150  is assembled axially to the spacer  110 . 
     In addition to attaching to the spacer  110 , the plate  150  is also configured to attach into one or more vertebral bodies via one or more bone screws  88 ,  89 . As shown in  FIG. 5A , the plate  150  includes a first screw hole  152  and a second screw hole  154  for receiving bone screws  88 ,  89  therein. In some embodiments, screw hole  152  is angled upwardly such that an inserted bone screw  88  passes upward into an upper vertebral body, while screw hole  154  is angled downwardly such that an inserted bone screw  89  passes downward into a lower vertebral body. While the illustrated embodiment illustrates a pair of screw holes for receiving a pair of bone screws, it is possible to have one, three, four, live or more screw holes for receiving a different number of bone screws. 
     Over time, it is possible for bone screws to back-out. The plate  150  thus has a blocking or set screw  156  (shown in  FIG. 5C ) that assists in preventing back-out of inserted bone screws, As shown in  FIG. 5C , the set screw  156  can be in an initial position that allows first and second bone screws to pass through holes  152 ,  154 . Once the bone screws have been inserted through the holes  152 ,  154 , the set screw  156  can be rotated (e.g., 90 degrees), to thereby block the bone screws and prevent back out of the bone screws. In some embodiments, the set screw  156  abuts a side of the head of the bone screws to prevent back-out of the bone screws, white in other embodiments, the set screw  156  rests over a top of the head of the bone screws to prevent back-out of die bone screws. In some embodiments, the set screw  156  comes pre-fixed with the plate  150 . As shown in  FIG. 5C , a single set screw  156  can be used to conveniently block a pair of bone screws. In other embodiments, each bone screw can be assigned its own set screw, which can operate independently of one another, to prevent back-out of the bone screw. 
     The plate  150  can also include one or more knife-like edges  163  that provide additional torsional stabilization when the plate  150  rests against a bone member. As shown in  FIG. 5C , the knife-like edges  163  can be formed on both the upper and lower surfaces of the plate  150  body. While the illustrated embodiment shows a pair of knife-like edges  163  on an upper surface of the plate body and a pair of knife-like edges  163  on a lower surface of the plate body, one skilled in the art will appreciate that a different number of knife-like edges  163  can be provided. 
       FIGS. 6A-6D  illustrate different views of the low profile plate shown in  FIGS. 5A-5D . From these views, one can see the enclosed posterior extension  155  that extends from the body of the plate  150 . At the distal end of the enclosed posterior extension  155  are a pair of outwardly extending surfaces  166 ,  167  that are configured to fit within inlets  121 ,  123  formed in the spacer. From these views, one can also see the deformable tab lock  160  ( FIG. 6B ) that can help secure the plate  150  to the spacer  110 . In addition, from these views, one can see the windows  172  that are formed in each of the arms of the enclosed posterior extension  155 . The windows  172  advantageously help to improve desirable radiolucency, and are of large size to provide a large viewing surface area. While the illustrated windows  172  are shown as triangular with rounded edges, in other embodiments, the windows  172  can have a different shape, such as circular or oval. In some embodiments, the plate  150  is assembled axially to the spacer  110 . 
     In some embodiments, the low profile plate  150  can also include indented gripping sections  173  (shown in  FIGS. 6A and 6B ). These indented gripping sections  173  advantageously provide a gripping surface for an insertion instrument, thereby facilitating easy delivery of the plate to a spacer body during surgery. 
       FIGS. 7A-7D  illustrate different views of a PEEK spacer to be used with the low profile plate shown in  FIGS. 5A-5D . From these views, one can see how the spacer  110   a  includes an upper surface  112   a  and a lower surface  114   a  with texturing  116   a ; a generally C-shaped body including a pair of arms  113   a  each having an inner inlet  121 ,  123   a  formed therein; and a tapered leading edge  122   a . In addition, one skilled in the art can appreciate the substantially symmetric shape of the inner opening  120   a , which serves as a graft hole for receiving graft material therein. 
       FIGS. 8A-8D  illustrate different views of an allograft spacer to be used with the tower profile plate shown in  FIGS. 5A-5D . While the allograft spacer  110   b  shares similar features to the PEEK spacer  110   a  shown in previous figures, such as the C-shaped body including a pair of arms  113   b  each having an inlet  121   b ,  123   b  formed therein, the allograft spacer  110   b  need not be the same. 
       FIGS. 9A-9D  illustrate different views of a third alternative embodiment of a low profile plate attached to a spacer according to some embodiments. In the present embodiment, the plating system  205  includes a plate  250  having lateral arms or extensions  270  that extend around an exterior surface of a spacer  210 . The lateral extensions  270  extend wider than the lateral extensions  70  in the first embodiment, and do not necessarily have to interlock with the spacer  210 . While in some embodiments, the plate  250  can be attached to the spacer  210  after inserting the spacer  210  into a desired location in the body, in other embodiments, the plate  250  can be pre-assembled with the spacer  210  prior to inserting the plating system  205  into the desired location. 
     Like the spacer  10  in  FIG. 1A , the spacer  210  is configured to have an upper surface  212 , a tower surface  214 , and a leading end  222 . In some embodiments, the upper surface  212  and/or lower surface  214  includes texturing  216 , such as teeth, ribs, ripples, etc. to assist in providing frictional contact with adjacent vertebral bodies. In some embodiments, the leading end  222  of the spacer  210  can be slightly tapered, as shown in  FIG. 9D . With the taper, the leading end  222  can serve as a distraction surface that helps the spacer  210  to be inserted into an intervertebral space. As shown in  FIG. 9B , the leading end  222  can be slightly concave, though in other embodiments, the leading end  122  can be straight or convex. Unlike previously illustrated spacers, the spacer  210  can have a graft hole  220  that is completely enclosed. As shown in  FIG. 913 , the graft hole  220  can surrounded by four walls. In addition, the spacer  210  can include four outer walls: two straight walls, a convex wall and a concave wall. 
     In some embodiments, the graft opening  220  (shown in  FIG. 9B ) has a different shape from the openings of prior embodiments, as the graft opening  220  is enclosed. While the graft opening  220  is rectangular with rounded edges, in other embodiments, the graft opening  220  can have a different shape. For example, in some embodiments, the graft opening  220  can have curved walls, instead of straight walls, or can have tapered walls, instead of straight walls. 
     Like spacer  10 , the spacer  210  can be formed of a variety of materials. In some embodiments, the spacer  210  comprises allograft bone, while in other embodiments, the spacer  210  comprises PEEK. 
     The plate  250  is configured to have a pair of lateral extensions  270  that receive the spacer  220 . As shown in  FIG. 9A , in some embodiments, the lateral extensions  270  include one or more windows  272  for improving radiolucency of the plating system. In some embodiments, the plate  250  is assembled axially to the spacer  210 . 
     In addition to capturing the spacer  210 , the plate  250  is also configured to attach into one or more vertebral bodies via one or more bone screws  88 ,  89 . As shown in  FIG. 9A , the plate  250  includes a first screw hole  252  and a second screw hole  254  for receiving bone screws  88 ,  89  therein. In some embodiments, screw hole  252  is angled upwardly such that an inserted bone screw  88  passes upward into an upper vertebral body, while screw hole  254  is angled downwardly such that an inserted bone screw  89  passes downward into a lower vertebral body. While the illustrated embodiment illustrates a pair of screw holes for receiving a pair of bone screws, it is possible to have one, three, four, five or more screw holes for receiving a different number of bone screws. 
     Over time, it is possible for bone screws to back-out. The plate  250  thus has a blocking or set screw  256  (shown in  FIG. 9C ) that assists in preventing back-out of inserted bone screws. As shown in  FIG. 9C , the set screw  256  can be in an initial position that allows first and second bone screws to pass through holes  252 ,  254 . Once the bone screws have been inserted through the holes  252 ,  254 , the set screw  256  can be rotated (e.g., 90 degrees), to thereby block the bone screws and prevent back out of the bone screws. In some embodiments, the set screw  256  abuts a side of the head of the bone screws to prevent back-out of the bone screws, while in other embodiments, the set screw  256  rests over a top of the head of the bone screws to prevent back-out of the bone screws. In some embodiments, the set screw  256  comes pre-fixed with the plate  250 . As shown in  FIG. 9C , a single set screw  256  can be used to conveniently block a pair of bone screws. In other embodiments, each bone screw can be assigned its own set screw, which can operate independently of one another, to prevent back-out of the bone screw. 
       FIGS. 10A-10D  illustrate different views of the low profile plate shown in  FIGS. 9A-9D . From these views, one can see the lateral extensions  270  that extend from the body of the plate  250 . From these views, one can also see the windows  272  ( FIG. 10A ) that extend along a substantial length of the lateral extensions  270 . In some embodiments, each window  272  has a length greater than half the length of each lateral extension  270 , thereby advantageously increasing the radiolucency of the plating system. In some embodiments, the plate  250  is assembled axially to the spacer  210 . 
     In some embodiments, the low profile plate  250  can also include indented gripping sections  273  (shown in  FIGS. 10A and 10B ). These indented gripping sections  273  advantageously provide a gripping surface for an insertion instrument, thereby facilitating easy delivery of the plate to a spacer body during surgery. 
       FIGS. 11A-11D  illustrate different views of a fourth alternative embodiment of a low profile plate attached to a spacer according to some embodiments. Like the previous embodiment, the plating system  305  includes a plate  350  having lateral arms or extensions  370  that extend around an exterior surface of a spacer  310 . The lateral extensions  370  extend wider than the lateral extensions  70  in the first embodiment, and do not necessarily have to interlock with the spacer  310 . While in some embodiments, the plate  350  can be attached to the spacer  310  after inserting the spacer  310  into a desired location in the body, in other embodiments, the plate  350  can be pre-assembled with the spacer  310  prior to inserting the plating system  305  into the desired location. 
     Like the spacer  10  in  FIG. 1A , the spacer  310  is configured to have an upper surface  312 , a tower surface  314 , and a leading end  322 . In some embodiments, the upper surface  312  and/or lower surface  314  includes texturing  316 , such as teeth, ribs, ripples, etc. to assist in providing frictional contact with adjacent vertebral bodies. In some embodiments, the leading end  322  of the spacer  310  can be slightly tapered, as shown in  FIG. 11D . With the taper, the leading end  322  can serve as a distraction surface that helps the spacer  310  to be inserted into an intervertebral space. As shown in  FIG. 11B , the leading end  322  can be slightly concave, though in other embodiments, the leading end  322  can be straight or convex. In some embodiments, the spacer  310  can have a graft hole  320  that is completely enclosed. As shown in  FIG. 11B , the graft hole  320  can surrounded by four walls. In addition, the spacer  320  can be comprised of four outer walls: two straight, one concave and one convex. 
     In some embodiments, the graft opening  320  (shown in  FIG. 11B ) of the spacer  310  is enclosed. While the graft opening  320  is rectangular with rounded edges, in other embodiments, the graft opening  320  can have a different shape. For example, in some embodiments, the graft opening  320  can have curved walls, instead of straight walls, or can have tapered walls, instead of straight walls. 
     Like spacer  10 , the spacer  310  can be formed of a variety of materials. In some embodiments, the spacer  210  comprises allograft bone, while in other embodiments, the spacer  310  comprises PEEK. 
     The plate  350  is configured to have a pair of lateral extensions  370  that receive the spacer  320 . As shown in  FIG. 11A , in some embodiments, the lateral extensions  370  include one or more windows  372  for improving radiolucency of the plating system. In some embodiments, the plate  350  is assembled axially to the spacer  310 . 
     In addition to capturing the spacer  310 , the plate  350  is also configured to attach into one or more vertebral bodies via one or more bone screws  88 ,  89 . As shown in  FIG. 9A , the plate  350  includes a first screw hole  351 , a second screw hole  352  and a third screw hole  354  for receiving bone screws  87 ,  88 ,  89  therein. In some embodiments, screw holes  352  and  354  are angled upwardly such that inserted bone screws  87 ,  88  pass upward into an upper vertebral body, while screw hole  351  is angled downwardly such that inserted bone screw  89  passes downward into a lower vertebral body. While the illustrated embodiment illustrates three screw holes for receiving three bone screws, it is possible to have one, two, four, five or more screw holes for receiving a different number of bone screws. 
     Over time, it is possible for bone screws to back-out. The plate  350  thus has blocking or set screws  356 ,  357 ,  358  (shown in  FIG. 12C ), each of which corresponds to one of screw holes  351 ,  352 ,  354 . As shown in  FIG. 12C , the set screws  356 ,  357 ,  358  can be in an initial position that allows first, second and third bone screws to pass through holes  351 ,  352 ,  354 . Once the bone screws have been inserted through the holes  351 ,  352 ,  354 , the set screws  356 ,  357 ,  358  can be rotated (e.g., 90 degrees), to thereby block the bone screws and prevent back out of the bone screws. In some embodiments, the set screws  356 ,  357 ,  358  abut a side of the head of the bone screws to prevent back-out of the bone screws, while in other embodiments, the set screws  356 ,  357 ,  358  rest over a top of the head of the bone screws to prevent back-out of the bone screws. In some embodiments, the set screws  356 ,  357 ,  358  come pre-fixed with the plate  350 . As shown in  FIG. 12C , a single set screw  356 ,  357 ,  358  can be used to conveniently block a single bone screws. In other embodiments, each set screw can be designed to block more than one set screw to prevent back-out of the bone screw. 
       FIGS. 12A-12D  illustrate different views of the low profile plate shown in  FIGS. 11A-11D . From these views, one can see the lateral extensions  370  that extend from the body of the plate  350 . From these views, one can also see the windows  372  ( FIG. 12A ) that extend along a substantial length of the lateral extensions  370 . In some embodiments, each window  372  has a length greater than half the length of each lateral extension  370 , thereby advantageously increasing the radiolucency of the plating system. In some embodiments, the plate  350  is assembled axially to the spacer  310 . 
     The plating systems describe include a plate that is independent from a spacer. The plate is low-profile and can be used with any type of spacer, such as allograft or PEEK. 
       FIGS. 13A-13D  illustrate different views of a multi-piece allograft spacer to be used with the low profile plates discussed above according to some embodiments. The multi-piece allograft spacer  410  can be formed of an upper member  436  and a tower member  438  that are connected together via one or more pins  475 . The upper member  436  and the lower member  438  each include cut-out portions that help form a graft opening  420  in the spacer  410 . 
     The upper member  436  can include an upper surface having bone engagement surfaces (e.g., ridges, teeth, ribs) and a lower interfacing surface  446 . The lower member  438  can include a tower surface having bone engagement surfaces (e.g., ridges, teeth, ribs) and an upper interfacing surface  448 . In some embodiments, the upper member  436  can include one or more holes  462 , while the lower member  438  can include one or more holes  464  which align with the one or more holes  462  of the upper member. The aligned holes are configured to receive one or more pins  475  to keep the upper and lower members of the allograft spacer together. In some embodiments, the pins  475  are also formed of bone material, such as allograft. 
     As shown best in  FIG. 13C , the lower interfacing surface  446  of the upper member  436  is directly engaged with the upper interfacing surface  448  of the lower member  438 . While the lower interfacing surface  446  and the upper interfacing surface  448  can be flat-on-flat, as both surfaces are planar, in some embodiments (as shown in  FIG. 13C ), the interface between the two surfaces is at an angle relative to the holes for receiving the pins  475 . In other words, the pins  475  are received at an angle to the interface between the upper member  436  and the lower member  438 . In addition, as shown in  FIG. 13C , holes  462  and  464  need not go through the entirety of their respective members. For example, as shown in  FIG. 13C , while hole  462  goes entirely through the upper and lower surface of the upper member  436 , hole  464  goes only through the upper surface of the lower member  438 , and does not go through to the lower surface. Accordingly, in some embodiments, aligned holes  462  and  464  create a “blind” pin-hole, whereby the hole does not go through the uppermost and lowermost surfaces of the spacer  410 . Advantageously, in some embodiments, the use of such blind holes for receiving pins helps to maintain the pins within the spacer body. 
       FIGS. 14A-14D  illustrate different views of an alternative multi-piece allograft spacer to be used with the tower profile plates discussed above according to some embodiments. The multi-piece allograft spacer  510  can be formed of a left member  536  and a right member  538  that are connected together in series or side-by-side (e.g., laterally) via one or more pins  575 . The left member  536  and the right member  538  each include cut-out portions that help form a graft opening  520  in the spacer  510 . 
     The left member  536  can include upper and lower surfaces having bone engagement surfaces (e.g., ridges, teeth, ribs). In addition, the left member  536  further includes a right interfacing surface  546 . The right member  538  can also include upper and lower surfaces having bone engagement surfaces ridges, teeth, ribs). In addition, the right member  538  further includes a left interfacing surface  548 . In some embodiments, the left member  536  can include one or more holes  562 , while the right member  538  can include one or more holes  564  which align with the one or more holes  562  of the left member. The aligned holes are configured to receive one or more pins  575  to keep the left and right members of the allograft spacer together. 
     As shown best in  FIG. 14A , the right interfacing surface  546  of the left member  536  is directly engaged with the left interfacing surface  548  of the right member  538 . While the right interfacing surface  546  and the left interfacing surface  548  can be flat-on-flat, as both surfaces are planar, in some embodiments (as shown in  FIG. 14A ), the interface between the two surfaces is at an angle relative to the holes for receiving the pins  575 . In other words, the pins  575  are received at an angle to the interface between the left member  536  and the right member  538 . In addition, as shown in  FIG. 14B , holes  562  and  564  need not go through the entirety of their respective members. In other words, one or more of the holes (e.g., holes  562 ,  564  or combined) can be blind holes, whereby the holes do not go through the left and right surfaces of the lateral implants. 
     By having multi-piece allograft spacers that are either stacked or aligned side-by-side, it is possible to have spacers of increased height and width. While the embodiments herein show two piece spacers, one skilled in the art will appreciate that three or more members can be combined to form multi-piece allograft spacers for use with any of the plate members described above. 
       FIGS. 15A-15D  illustrate different views of an alternative low profile plate attached to a spacer according to some embodiments. The plating system  605  comprises a plate  650  attached or mounted to a spacer  610 . 
     The system  605  includes a number of similar features to prior embodiments. The spacer  610  includes a body having an upper surface  612  and a lower surface  614  with texturing (e.g., ribs, grooves, teeth, protrusions) and sidewalk including one or more notches  617  for receiving plate extensions. The body of the spacer  610  can be U-shaped or C-shaped, such that a central portion includes a graft opening  620  for receiving graft material therein. The plate  650  includes a body having a first screw hole  652  for receiving a first screw member therethrough, a second screw hole  654  for receiving a second screw member therethrough, and a recess for receiving a blocking fastener or set screw  656 . In addition, a pair of extension arms or members  617  extend from the plate body and are received in each of the notches  617  formed in the spacer  10 . Each of the extension members  617  includes a window  672  for receiving a hump portion or region of the spacer to further secure the spacer  610  with the plate  650 . In addition, the plate member  650  can include one or more stabilizers or knife-like edges  663  that can help secure the plate member  650  to a vertebral body. While the stabilizers  663  are shown as sharp and pointed, in other embodiments, the stabilizers  663  are more blunt and in some cases, even slightly rounded. 
     The plating system  605  in  FIGS. 15A and 15D  is unique in that the first upper screw hole  652  has been raised such that a central axis of the first upper screw hole  652  is positioned higher than the upper surface  612  of the spacer  610 . In addition, the second lower screw hole  654  has been lowered such that a central axis of the second lower screw hole  654  is positioned below the lower surface  614  of the spacer  610 . As shown in  FIG. 15B , each of the holes  652 ,  654  has an adjacent brow member that extends from the plate body. First screw hole  652  is adjacent upper brow member  662 , while second screw hole  654  is adjacent lower brow member  664 . Upper brow member  662  has been raised to accommodate the raised upper screw hole  652 , while lower brow member  664  has been lowered to accommodate the lowered tower screw hole  654 . Advantageously, by raising the upper screw hole  652  and lowering the lower screw hole  654 , this reduces the likelihood of any viewing obstruction that may occur from the spacer  610 . Moreover, even though the upper brow member  662  is raised and the lower brow member  664  is lowered, advantageously, the plating system  605  still maintains a low profile such that most if not all of the plate system remains in a disc space. In other embodiments, it may be desired for a part of the upper brow member  662 , a part of the lower brow member  664  or both to contact a vertebral face (e.g., an anterior face), thereby providing stability to the plating system  605 . 
       FIGS. 16A-161 ) illustrate different views of a plate member  650  used in the plating system  605 . From these views, one can clearly see how the upper brow member  662  and first upper hole member  652  have been raised, while the lower brow member  664  and second lower hole member  664  have been lowered, relative to other designs. In some embodiments, the entire central axis of first upper hole member  652  (e.g., from a front of the plate member  650  to a back of the plate member  650 ) is continuously above the upper surface of the spacer, thereby advantageously providing a less unobstructed view of the first upper hole member  652 . Likewise, in some embodiments, the entire central axis of the second lower hole member  654  (e.g., from a front of the plate member  650  to aback of the plate member  650 ) is continuously below the lower surface of the spacer, thereby advantageously providing a less unobstructed view of the second lower hole member  654 . 
       FIGS. 17A-17C  illustrate different views of a spacer  610  used in the plating system  605 . From these views, one can clearly see features of the spacer  610  includes its upper surface  612 , lower surface  614 , side-walls with notches  617  and graft opening  620 . In addition, with the plate member removed from the views, one can also see an upper chamfer  618   a  and a lower chamfer  618   b  that are cut into the spacer  610 . These chamfers  618   a ,  618   b  advantageously provide clearance for bone screws that are inserted through the plating system  605 . One skilled in the art will appreciate that the spacer can be made of many different materials. In some embodiments, the spacer will be made out of bone (e.g., allograft), while in other embodiments, the spacer will be made of PEEK. Advantageously, the plating system  605  is removably attached to the spacer  610  such that a surgeon can choose to include a spacer of a certain material as so desired during a surgical procedure. 
       FIGS. 18A-18D  illustrate different views of yet another plate system involving a plate member and a spacer having a unique multi-piece composition in accordance with some embodiments. The plate system  705  includes similar elements as found in prior embodiments, including a plate member  750  having a first upwardly oriented screw hole  752  for receiving a first screw, a second downwardly oriented screw hole  754  for receiving a second screw, and a blocking member or screw  756 , as well as a spacer  710  allograft or PEEK) having an upper surface  712 , a tower surface  714 , a graft opening  720 , and notches  717  for receiving arms or extensions  770  of the plate member  750 . The plate member  750  also includes one or more windows  772  in its extensions  770  for receiving a raised or bump out portion of the spacer  705 , thereby helping to retain the spacer  705  within the plate member  750 . In addition, the plate member  750  includes stabilizers  763  in the form of knife-like edges that help to grip into a vertebral body. 
     In addition to these features, the spacer  710  has a unique multi-piece composition. As shown in  FIGS. 18A and 18D , in some embodiments, the spacer  710  has a body formed of two adjacent members—a first member  711  and a second member  713 . The first member  711  and the second member  713  can be held together via one or more pin members, although in other embodiments, the first member  711  and second member  713  can be held via adhesive, mateable connections, etc. As shown in  FIG. 18D , second member  713  can include an upper overhang region  717  that hangs over a part of the first member  711 . Similarly, first member  711  can include a lower overhang region  711  that hangs below a part of the second member  713 . Advantageously, these overhang regions  711  serve as guides to identify the location of the interface  715  between the first member  711  and the second member  713 . During manufacturing, the overhang regions  711  make it easy to inspect the interface to  715  to ensure that the two members  711 ,  713  are properly secured together. While the illustrated embodiment shows a spacer  710  having two separate overhanging regions, in other embodiments, the spacer  710  can have one single overhanging region. As before, the spacer  710  can be made of many different types of materials, including bone (e.g., allograft) and PEEK), and a surgeon can advantageously decide what type of spacer should accompany the plate before or during surgery. 
       FIG. 19  shows a plating system  805  having a plate member  850  having extensions  870  and a spacer  810  similar to that found in  FIGS. 18A-18D ; however, the spacer  810  is designed to accommodate lordosis. In other words, while the upper surface  712  and lower surface  714  of the spacer  710  can be substantially parallel (as shown in  FIG. 18C ), the upper surface  812  and lower surface  814  of the spacer  810  can have some degree of angulation or lordosis. In some embodiments, relative to a mid-line of the spacer  810 , the upper surface  812  and/or lower surface  814  can have a degree of angulation of 2, 3, 5, 7, 12 degrees or more. Advantageously, the lordotic spacer  810  (which is accompanied with the plate member  850 ) helps to accommodate different anatomies. 
       FIGS. 20A-20D  show yet another alternative plating system having a plate member attached to multiple spacers in accordance with embodiments of the present application. The unique plating system  905  comprises a plate member  950  having a pair of inner arms or extensions  975  and a pair of outer arms or extensions  970  for receiving one or more spacers  910  therein. In some embodiments, both the inner and outer extensions  975 ,  970  include protruding portions designed to be received in notches in the one or more spacers. 
     As shown in  FIG. 20A , the plating system  905  includes a first spacer  910   a  that is retained between a shorter outer extension  970  and a longer inner extension  975  of the plate member  950 . The shorter outer extension  970  of the plate is configured to be received in notch  917  of the spacer  910   a , while the longer inner extension  975  of the plate is configured to be received in notch of the spacer  910   a . In addition, advantageously, the shorter outer extension  970  includes a window  972  and the longer inner extension  975  includes a window  974 . Each of the windows  972 ,  974  is configured to receive a bump out portion of the spacer  910 , thereby helping to retain the spacer  910  to the plate member  905 . In addition, the windows  972 ,  974  help to provide a means to visualize fusion (e.g., in a lateral image) that is occurring once the spacer is implanted within a disc space. Similarly, the plating system  905  includes a second spacer  910   b  that is retained between a shorter outer extension  970  and a longer inner extension  975  on an opposite side of the plate member  950 . While in the present embodiment, each of the longer inner extensions  975  is separated from the other without any connecting member, in other embodiments, a connection bar or bridge (such as shown in  FIGS. 21A and 21B ) can extend between the two inner extensions  975 . Advantageously, when the plating system  905  is placed in a disc space, graft material can be packed between the two inner extensions  975  to promote fusion within the disc space. 
     Advantageously, in accordance with some embodiments, the plating system  905  is designed to hold at least two spacers  910   a ,  910   b . In some embodiments, the spacers  910   a ,  910   b  are substantially rectangular pieces. In some embodiments, the spacers  910   a ,  910   b  can have substantially rounded edges. In some embodiments, the spacers  910   a ,  910   b  can include one or more chamfers  918  for providing clearance for one or more screws that are inserted through the plate member  905 . For example, spacer  910   a  can include a chamfer that provides clearance for a screw that passes through plate opening  954 , while spacer  910   b  can include a chamfer that provides clearance for a screw that passes through plate opening  952 . Advantageously, the use of two spacers  910   a ,  910   b —one on each side of the plate system  905 —helps to stabilize the plate system within the disc space. Moreover, having multiple individual spacers  910   a ,  910   b  that are smaller in size can ease manufacturing issues, as the spacers can be formed of relatively small pieces of bone, which can be easier to find than larger pieces of bone. In other words, bone that is removed from a body can improve the yield of production, as it will be easier to create the spacer members. While the spacers  910   a ,  910   b  are illustrated as being single-bodied members in the present embodiments, in other embodiments, the spacers can be formed of multiple pieces (e.g., pinned together). 
       FIGS. 21A and 21B  illustrate different views of another alternative low profile plate attached to multiple spacers according to some embodiments. The plate system  1005  comprises a plate member  1050  attached to a pair of spacers  1010   a  and  1010   b . Like the embodiment in  FIG. 20A , the plate member  1050  of the present embodiment includes a pair of outer arms or extensions  1070   a ,  1070   b  and a pair of inner arms or extensions  1075   a ,  1075   b . Plate extensions  1070   a  and  1075   a  are configured to retain spacer  1010   a , while plate extensions  1070   b  and  1075   b  are configured to retain spacer  10101 ). As shown in  FIGS. 21A and 21B , the inner extensions  1075   a  and  1075   b  includes a connection or bridge member  1088  that extends between them. Advantageously, the bridge member  1088  helps provide added stability to the plate system  1005 , and also helps provide a barrier to retain graft material within the plate system  1005 . As shown in  FIG. 21A , in some embodiments, the inner extensions  1075   a  and  1075   b  are parallel to one another. 
     As shown in  FIG. 21B , outer plate extensions  1070   a  and  1070   b  include at least one window  1072  formed therein. Similarly, inner plate extensions  1075   a  and  1075   b  include at least one window formed therein. As shown in  FIG. 21B , inner plate extensions each include two windows— 1074  and  1075 —that are formed adjacent to one another. Inner plate extension  1075   a  includes windows  1074   a  and  1075   a , while inner plate extension  1075   b  includes windows  1074   b  and  1075   b . In some embodiments, the windows  1072 ,  1074 ,  1075  can advantageously be designed to hold a bump out portion of the spacers and/or provide increased visualization to a surgeon during or after a fusion procedure. While in some embodiments, each of the windows  1072 ,  1074 , and  1075  perform the same duties and functions, in other embodiments, the windows can perform different functions. For example, while inner window  1074  can be used to both retain the spacer and aid in fusion visualization, inner window  1075  can be used simply for fusion visualization. 
       FIG. 22  illustrates another alternative low profile plate attached to multiple spacers according to some embodiments. The plate system  1105  comprises a plate member  1150  attached to a pair of spacers  1110   a  and  1110   b . Like the embodiment in  FIG. 21A , the plate member  1150  of the present embodiment includes a pair of outer arms or extensions  1170   a ,  1170   b  and a pair of inner arms or extensions  1175   a ,  1175   b . Plate extensions  1170   a  and  1175   a  are configured to retain spacer  1110   a , white plate extensions  1170   b  and  1175   b  are configured to retain spacer  1110   b . As shown in  FIGS. 21A and 21B , the inner extensions  1175   a  and  1175   b  includes a connection or bridge member  1188  that extends between them. Advantageously, the bridge member  1188  helps provide added stability to the plate system  1105 , and also helps provide a barrier to retain grail material within the plate system  1105 . In contrast to the inner extensions  1075   a ,  1075   b    FIG. 21A , the inner extensions  1175   a ,  1175   b  are non-parallel and angulated relative to one another. Furthermore, due to the shape of the plate member  1150 , the shapes of the individual spacers  1110   a  and  1110   b  differ in that they have a prominent angled surface adjacent to the inner extensions  1175   a ,  1175   b.    
       FIG. 23  illustrates another alternative low profile plate attached to multiple spacers according to some embodiments. The plate system  1205  comprises a plate member  1250  attached to a pair of spacers  1210   a  and  1210   b . Like the embodiment in  FIG. 22 , the plate member  1250  of the present embodiment includes a pair of outer arms or extensions  1270   a ,  1270   b  and a pair of inner arms or extensions  1275   a ,  1275   b . Plate extensions  1270   a  and  1275   a  are configured to retain spacer  1210   a , white plate extensions  1270   b  and  1275   b  are configured to retain spacer  1210   b . As shown in  FIG. 23 , the inner extensions  1275   a  and  1275   b  includes a connection or bridge member  1288  that extends between them. Advantageously, the bridge member  1288  helps provide added stability to the plate system  1205 , and also helps provide a barrier to retain graft material within the plate system  1205 . In contrast to the bridge member  1188  in  FIG. 22 , the bridge member  1288  is elongated and extends to a distal end of the spacers  1210   a ,  1210   b , thereby creating an even larger space for receiving graft material in the middle of the plate system  1205 . 
       FIGS. 24A-24C  illustrate another alternative low profile plate attached to multiple spacers according to some embodiments. The plate system  1305  comprises a plate member  1350  attached to a multi-piece spacer  1310  formed of three members  1310   a ,  1310   b ,  1310   c . Like the embodiment in  FIG. 23 , the plate member  1350  of the present embodiment includes a pair of outer arms or extensions  1370   a ,  1370   b  and a pair of inner arms or extensions  1375   a ,  1375   b  connected by a bridge member  1388 . The inner extensions  1375   a ,  1375   b  and bridge member  1388  are configured to be enclosed by the body of the spacer  1310 . Advantageously, the bridge member  1388  helps provide added stability to the plate system  1305 , and also helps provide a barrier to retain graft material within the plate system  1305 . 
     In some embodiments, the spacer  1310  is formed of three different members  1310   a ,  13110   b ,  1310   c . The members  1310   a  and  13110   b  can be outer members which bound the inner member  1310   c . As shown in  FIG. 24C , the members  1310   a  and  1310   b  can be substantially similar, and can include upper and tower surfaces with surface protrusions to enable better gripping of bone. Inner member  1310   c  can be different from the other members and can include a relatively smooth surface without surface protrusions. In addition, the inner member  1310   c  can be of a different height than the other members. In some embodiments, the three members  1310   a ,  1310   b ,  1310   c  are pinned together, while in other embodiments, they can be joined together via an adhesive or mateable connection. Advantageously, the addition of the inner member  1310   c  provides further support to the overall structure of the plate system  1305 . 
       FIGS. 25A and 25B  illustrate another alternative low profile plate attached to a multi-piece spacer having a metal insert according to some embodiments. The plate system  1405  comprises a plate member  1450  attached to a multi-piece spacer  1410  formed of two similar components  1410   a ,  1410   b  and a metal insert  1439 . The plate member  1450  can include a first screw opening, a second screw opening and a rotatable locking mechanism  1456  to prevent back out of screws that are inserted through the openings. In some embodiments, the plate member  1450  of the present embodiment is mounted to the front of the spacer. In other embodiments, the plate member  1450  includes a pair of outer arms or extensions and/or a pair of inner arms or extensions (not shown) to help retain the spacer  1410  within the plate member  1450 . 
     In some embodiments, the spacer  1410  is formed of two members  1410   a  and  1410   b  separated by a metal insert  1439 . These members partially enclose a graft opening  1420 . The two members  1410   a  and  1410   b  can be formed of a material different from the metal insert  1439 , such as PEEK. Advantageously, the metal insert  1439  is designed to provide additional strength to the spacer  1410 . In some embodiments, the metal insert  1439  is formed of titanium. As shown in the exploded view in  FIG. 25B , the spacer  1410  be attached to the plate member  1450  via vertical fastening members  1429   a ,  1429   b . One skilled in the art will appreciate that the spacer  1410  can be used with any of the other plate members discussed above. 
     One skilled in the art will appreciate that any of the plate systems described above can be used with other spinal implants. Among the other implants that can accompany the plate systems include stabilization systems and rod systems, including rod members, hook members, and bone fasteners such as pedicle screws. One skilled in the art will appreciate that any of the plate systems described above can also be used with one another, or can be used multiple times along different segments of the spine. In addition, any of the plate systems described above can be used with a variety of navigation and guidance tools, including those related to neuromonitoring and robotics. Furthermore, one of skill in the art will appreciate that the plate systems described above can be produced in a number of different ways, including in part via 3-D printing methods. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. Moreover, the improved plate systems and bone screw assemblies and related methods of use need not feature all of the objects, advantages, features and aspects discussed above. Thus, for example, those skilled in the art will recognize that the invention can be embodied or carried out in a manner that achieves or optimizes one advantage or a group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. In addition, while a number of variations of the invention have been shown and described in detail, other modifications and methods of use, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure, it is contemplated that various combinations or subcombinations of these specific features and aspects of embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the discussed bone screw assemblies. Thus, it is intended that the present invention cover the modifications and variations of this invention provided that they come within the scope of the appended claims or their equivalents.