Patent Publication Number: US-8523917-B2

Title: Anterior cervical instrumentation systems, methods and devices

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application is a continuation application claiming priority under 35 U.S.C. §120 to U.S. patent application Ser. No. 12/554,220, filed 4 Sep. 2009 now U.S. Pat. No. 8,147,529, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/094,340 filed 4 Sep. 2008, which are hereby incorporated in their entirety as if fully set forth herein. 
    
    
     TECHNICAL FIELD 
     Embodiments of the present invention relate to implantable surgical stabilization systems, devices, and methods for use in spinal surgery, and particularly to systems, methods, and devices that stabilize the cervical spine or other osseous structures. 
     BACKGROUND 
     Fusion of spinal vertebrae is often necessary to relieve debilitating pain or to correct a deformity. Cervical spinal fusion is often prescribed for patients suffering from degenerative disk disease whose symptoms may include neck pain of discogenic origin with degeneration of the disk confirmed by patient history and radiographic studies, trauma including fractures, tumors, deformity such as kyphosis, lordosis or scoliosis, pseudoarthrosis, or failed previous fusions. 
     Spinal surgical fusion is the process of bringing together two or more vertebrae under conditions whereby the vertebrae fuse together to form a unitary member of the spinal column. When vertebrae are fused, e.g., with bone grafts, graft extenders, or interbody spacers such as interbody cages or boxes (collectively termed “grafts” herein), it is desirable to stabilize the fused vertebrae using an apparatus such as a plate to fixate one cervical vertebra to another to promote fusion across motion segments. In carrying out the procedure, the members must be brought together under conditions that are critically controlled to prevent infection, maintain alignment of opposing members, and allow for the stress in the bone that is generated as the healing process matures. Immobilization is an important requirement during this healing process. 
     Another common spinal ailment is the degeneration of an intervertebral disc caused by trauma, disease, and/or aging. A degenerated intervertebral disc may have to be partially or fully removed from a spinal column. Partial or full removal of an intervertebral disc may destabilize a spinal column. Destabilization of a spinal column may alter the natural separation distance between adjacent vertebrae. Maintaining a natural separation distance between vertebrae may help prevent pressure from being applied to nerves that pass between vertebral bodies. Excessive pressure applied to the nerves may cause pain and/or nerve damage. During a spinal fixation procedure, a spinal implant may be inserted in a space created by removal or partial removal of an intervertebral disc between adjacent vertebrae. A spinal implant may maintain the height of the spine and restore stability to the spine. Intervertebral bone growth may fuse the implant to adjacent vertebrae. 
     A spinal implant may be inserted during a spinal fixation procedure using an anterior, lateral, or posterior spinal approach. A discectomy may be performed to remove or partially remove a defective and/or damaged intervertebral disc. A discectomy creates a disc space for a spinal implant. After a discectomy, a spinal implant may be inserted into the disc space. One or more spinal implants may be inserted between a pair of vertebrae. Spinal implants may be inserted into disc spaces prepared between more than one pair of vertebrae during a spinal fusion procedure. 
     A spinal plate may be coupled to vertebrae after insertion of one or more spinal implants. A spinal plate may stabilize the vertebrae and inhibit back out of the spinal implant from between vertebrae. A spinal plate may share a compressive load applied to one or, more spinal implants inserted between vertebrae. Fasteners, such as bone screws, may couple the spinal plate to vertebrae. Spinal plates may stabilize sections of cervical spine and/or sections of lumbar, spine. 
     The process of bone healing has been widely studied. Micro fractures, once thought to be negative events, are now seen as part of the natural process of bone remodeling and occur within bone in the course of everyday wear and tear. In the early stage of these cycles, bone resorption is first accomplished by osteoclasts. This is followed by new bone formation by osteoblasts over the latter part of each cycle. Osteoblasts serve a critical role in new bone formation, filling in the bony cavity in areas of bone remodeling with bone matrix. Osteoblasts are further known to release cytokines to attract osteoclasts. Osteoclasts serve to release proteases, which act to dissolve bone mineral matrix, collagen, and clear away damaged bone. Osetoclasts also releases matrix-bound growth factors and may serve as a chemo attractant for osteoblasts. The process of bone healing is currently believed to be a continual cycle, in which the body&#39;s response to microfractures and stress injuries within healing bone actually serve to strengthen healing ultimately and produce more solid bone. 
     What is needed are systems, methods and devices such as a plating system to repair bone fractures or to stabilize separate bony structures and allow them to fuse into a single item that may incorporate or harness the elements of the natural bone healing process. What are needed are systems, methods and devices that promote optimal fusion at a graft, particularly at cervical vertebrae. Further, methods, systems and devices that utilize a minimum number of parts and which may be easily customized intraoperatively by the surgeon are also needed. 
     SUMMARY 
     The present invention is directed to spinal instrumentation systems, methods and devices. The present invention comprises plating systems for use in spinal treatments, including, but not limited to, the cervical spine. Embodiments of the present invention are directed to anterior cervical instrumentation systems. Such systems may facilitate immobilizing or providing support for the cervical portion of the vertebral column of a patient. Such systems are composed of plates and screws for aligning and holding vertebrae in a desired position relative to one another. The systems may be “stand alone” as instrumentation is applied only to the anterior portion of the vertebral column (cervical vertebrae), or the systems may include other devices or compositions such as instrumentation on the posterior vertebral column. The systems, methods and devices allow a surgeon to modify and customize system components intraoperatively for optimal fit. 
     The present invention comprises systems, methods and devices comprising an implantable device for affixing to the anterior side of vertebrae, such as cervical vertebrae, for stabilizing the spinal column. Systems and devices of the present invention comprise a plate having an anterior surface and a posterior surface. A plate may comprise two parallel elongate channels extending from the distal end of the plate to the proximal end of the plate. Each of the channels forms an elongated opening through plate. A plate may further comprise at least one aperture, which may be centrally located, or at least one aperture at both the distal and proximal ends, and for stability reasons, may comprise two apertures at both the distal and proximal ends. The apertures may function in attaching the plate to a spinal vertebra using fasteners, such as screws. For example, apertures may be round, oval or rounded rectangular or combinations of these or others in shape. The systems may comprise a plurality of different length plates, which allows a surgeon the flexibility to select the desired length plate pre- or intraoperatively. 
     Systems and devices of the present invention may further comprise attachment elements for attaching the plate to one or more spinal vertebrae or for stabilizing the plate device. For example, a system and device may comprise a plurality of elements referred to herein as cross-linking elements. Cross-linking elements comprise at least two types of elements which may be similar in design, but differ in function. The two types of cross-linking elements comprise attachment cross-links and spacer cross-links and, for example, each may be a small bar that is as long as the plate is wide, with a defined width, that has two apertures, and each aperture may have the diameter of the apertures of the plate, and may also be sized so that a fastener, such as a screw, is sized to pass through the cross-linking aperture and also pass through the channel. Cross-linking element apertures may be located near both ends of a cross-linking element so that the apertures of the cross-linking elements align with each of the two channel openings in a plate. 
     The attachment elements comprise fasteners, elements for directly attaching the plate or attachment cross-links to the vertebrae, or attaching spacer cross-links to the plate, and such fasteners may comprise pins, dual head pins or screws. Fasteners may be sized to pass through the apertures of the cross-linking elements, the channels, and the apertures of the plates. Fasteners comprise a pin having two heads, wherein each head is spaced apart so that each pin head may enter a plate channel or two adjacent apertures. 
     Methods of the present invention comprise methods of spinal treatment, including treatment of the cervical spine. Methods comprise approaching the cervical spine from an anterior position. Using a template of a plate of the present invention, the exact location and placement of a plating system and device on the patient is determined. The template may be used on the exposed vertebrae or on x-rays or other visualizations of the spinal area. The size of plate to be used, the number cross-linking elements and attachment sites, where the attachment elements are to be placed through the plate apertures and the cross-link apertures is determined. Thus, the size of the plate and cross-link placement may individualized for the patient during the surgical procedure. 
     The appropriately sized plate may then be placed over the anterior portion of the vertebrae and anchored in place by the placement of fasteners, such as screws, through the at least one aperture, such as those found on the proximal and distal ends of the plate. The plate may be held in place with a temporary fastener, including but not limited to, a dual-headed pin. The pin is temporary in that the pin is placed through the plate to temporarily anchor the plate to the bone(s), for example to examine placement of the plate and alignment of the pin, and then the pin is removed. The pin may serve as a guide for bone screws which anchor the plate in place. 
     The proximal and distal apertures of a plate can be of several types. The first type may have the apertures of the same size and be round in shape, which allows for semi-constrained movement at the screw heads. Another type may have proximal and distal apertures that would be slightly elongated in the vertical axis, referred to herein as oval, to allow for translational movement at the proximal and distal ends of the plate. Another type may have proximal and distal apertures that would be elongated in the vertical axis, referred to herein as rounded rectangular, to allow for translational movement at the proximal and distal ends of the plate. 
     One or more attachment cross-links may be placed on the anterior side of the plate in the predetermined locations for attachment of the plate to the vertebrae, and attached to the vertebrae. For example, the plate and attachment cross-link may be attached to a spinal vertebra by passing a screw through each of the apertures of the cross-link and the parallel channels of the plate, and into the bone. The attachment cross-link may be fixed in position relative to the bone, but may move relative to the plate as the screws move in the parallel channels of the plate. Alternatively, the attachment cross-links may be spring loaded to lock it in position relative to the plate. The attachment cross-link may be positioned relative to the plate at any point along the length of the channels. Consequently, the surgeon may custom fit the location of the attachment cross-link to the bone because the position is not limited by predetermined screw holes in the plate. 
     Once one or more attachment cross-links are coupled to the vertebral bones, spacer cross-links may be fastened to the plate. The spacer cross-links do not attach to vertebrae, but fill the channel space on the device where the attachment cross-links are not present and function to stabilize the device. The entire length of the channels of the plate that are not occupied by the attachment cross-links may be filled with the spacer cross-links until there remains little or no open space in the channels of the plate. The spacer cross-links may be attached to the plate using a variety of fasteners, including, but not limited to, a hole-to-hole clamp or a screw head, or a short screw. The distance between the cross-links may be determined by the surgeon to create a range of travel of the attachment cross-link to provide a desired degree of subsidence. In this manner, the attachment cross-link attached to the bone may be locked in place relative to the plate or may have a predetermined degree of movement. The fasteners for attaching the plate device to the bone, such as screws, may be maintained in place by using locking heads or other designs known in the art. 
     An aspect of the present invention comprises systems, methods and devices wherein the plates may be provided in multiple lengths, but the apertures of the plates and the cross-linking elements, and the channel sized openings are uniform and allow for the use of the same size and style fastener head, such as the same screw head, for attachment of cross-linking elements, though the lengths of the fasteners may be a variety of lengths. This allows the surgeon to use one instrument, such as the same screw driver implement, to attach the plate to the vertebrae and to stabilize the device. The size, such as length and width of the cross-linking elements, is uniform and may be used with any length plate. This uniformity allows for a more simplified system for the surgeon to use, and for fewer tools to be needed in the operating theater. 
     These and other features as well as advantages, which characterize various aspects of the present invention, will be apparent from a reading of the following detailed description and a review of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1A  illustrates an exemplary embodiment of a plate of the present invention. 
         FIG. 1B  illustrates an exemplary embodiment of a plate of the present invention. 
         FIG. 1C  illustrates an exemplary embodiment of a plate of the present invention. 
         FIG. 1D  illustrates a side view an exemplary embodiment of a plate attached to a region of the spinal column. 
         FIG. 2  illustrates an exemplary embodiment of a system having a plurality of plates. 
         FIG. 3A  illustrates three embodiments of cross-linking elements. 
         FIG. 3B  illustrates an embodiment of a dual-headed pin. 
         FIG. 3C  illustrates an embodiment of an offset dual-headed pin. 
         FIG. 3D  illustrates an embodiment of placement of an offset dual-headed pin. 
         FIGS. 4A  and B illustrate a top view of a plate and cross-linking elements of an exemplary embodiment of the present invention. 
         FIG. 5  illustrates a side view of an exemplary embodiment of the system attached to a spinal column. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention comprises methods, systems and devices for treatment of spinal vertebrae, such as cervical vertebrae. The present invention comprises implantable devices comprising plates and attachment elements that allow for aligning and maintaining adjacent vertebrae, including but not limited to, cervical vertebrae, in a selected spatial relationship. The present invention may be used in spinal fusion methods. 
     The present invention comprises anterior cervical plating systems and devices that allow for the intersegmental compression of the spinal segment, such as compression of the adjacent vertebrae and the fusion graft in the disc space between the adjacent vertebrae, in lordosis, and where desired, multisegmental compression. For example, a device of the present invention comprises a plate, attachment elements comprising cross-linking elements comprising attachment cross-links and spacer cross-links, and fasteners, elements for directly attaching the plate and cross-linking elements to the bone, or attaching cross-linking elements to the plate, including, but not limited to, screws and dual-headed pins. For example, a system of the present invention comprises a plurality of plates of various lengths, and uniformly sized attachment elements and fasteners with uniform head design, and having multiple lengths. The invention further comprises tools and instruments used with such systems and devices in methods of spinal treatment such as drills, taps, screw drivers and the like. 
     Systems and devices of the present invention comprise a plate, which may be provided in a length that is sufficient to span a disc space and to overlap, at least in part, at least two adjacent cervical vertebrae. The anterior and posterior surfaces of a plate may be the same or may be different, in that one of the surfaces, such as the posterior surface which faces the vertebrae, may be textured and/or treated to induce bone growth or aid in attachment or stability. The plate, and other elements of the systems and devices, may be made of the same or different materials, such as steel, titanium, plastics, ceramics, or other biocompatible materials that have the structural strength and durability to withstand the cyclical loading associated with long term fixation. Materials that are also compatible with visualization systems, such as fluoroscopy or MRI, are also contemplated by the present invention. The plate and other elements may also comprise bioresorbable materials, bone in-growth materials, and/or growth promoting materials. For example, such bioresorbable, bone in-growth, or bone growth promoting materials may be found on surfaces of the plate and/or attachment elements such as screws. A plate of the present invention may be curved transverse to the longitudinal axis to conform to the anterior surface of a vertebrae, or may be curved along the longitudinal axis to conform to the lordotic curvature between the vertebrae, or may not be curved at all, or may be made of a material so that a surgeon or other personnel may curve the plate at the time of surgery, or may be made of a material that does not allow curving by a surgeon or other personnel. 
     A plate of the present invention comprises an anterior surface and a posterior surface and the two surfaces may be the same or different over the whole surface or a part of the surface areas. For example, the posterior surface, which directly faces the vertebrae surface, may be textured or coated with a material so as to encourage bone growth. For example, the anterior surface may be textured so as to allow better purchase of the attachment elements. The plate comprises a distal end and a proximal end. An aperture may be found on one or both of the distal or proximal ends, or may be located in a central position at the distal or proximal ends, or between the channels at one or both of the proximal or distal end areas, or in a midline position. 
     An example of a plate of the present invention comprises at least one aperture on both the proximal and the distal ends, and may further comprise at least two apertures on at least one of the proximal or distal ends, or at least two apertures on both the proximal and distal ends. The apertures may be the same size diameter or may have differently sized diameters. An example of the present invention comprises a plate having at least two apertures at both the proximal and distal ends that are of the same size diameter. An example of the present invention comprises a plate have at least one aperture at the midline of the plate equidistant between the channels. An example of the present invention comprises a plate having one or more apertures with the same size diameter or differently sized diameters. An example of the present invention comprises a plate having one or more apertures on the at least the proximal or distal end(s) where the apertures are longer in vertical length than the screw head to allow for true translational movement at both ends. 
     Where the one or more apertures on the distal and proximal ends of the plate are round or where the aperture allows for little adjustment for screw placement, the movement of the plate is based upon semi-constrained movement at the screw heads. Where the one or more apertures on the distal and proximal ends of the plate are elongated so that the vertical length is longer than the horizontal length, as in oval or rounded rectangular shaped apertures, there may be movement of the embedded screws in relation to the plate to allow for translational movement. Where the one or more apertures on the distal end are different from the one or more apertures on the proximal end, for example wherein rounded apertures are present on the proximal end to provide semi-constrained movement and one or more elongated or oval apertures are found at the distal end, translational movement is provided. Similarly, apertures in the cross-linking elements also allow for semi-constrained or translational movement depending on the shape of the aperture. The movement may be constrained by use of apertures having a particular shape that locks a screw tightly with the aperture. For example, the screw head and the aperture shape may be complementary so that a tight junction is formed between the screw head and the top of the aperture. For example, the aperture may be shaped like a star or other figure into which the screw head or a locking head fits exactly and constrains the movement at that location. 
     A plate of the present invention comprises at least two channels that are open from the anterior to the posterior surfaces, and which form openings that traverse a substantial portion of the length of the plate. The at least two channels run from an area near an aperture found at the distal end to an area near an aperture found at the proximal end, or where there are no apertures on the ends of the plate, the channels run from near the proximal end to near the distal end. The width of a channel may be the same or different size as the diameter of an aperture of a plate. An example of the present invention comprises a plate having two channels having widths of the channel openings that are the same as the diameter of the apertures of the plate, wherein the apertures of the plate have the same sized diameter. 
     Devices and systems of the present invention comprise attachment elements. Attachments elements comprise cross-linking elements and fasteners, elements that interact intimately with the bone or that attach cross-linking elements to a plate, such as screws and dual-headed pins. Cross-linking elements comprise attachment cross-links and spacer cross-links. Cross-linking elements are rectangular shaped bars that fit transversely across a plate, and for example, may be as long as a plate is wide. Cross-linking elements may have no apertures or at least one aperture. For example, a cross-linking element has two apertures that are located so that an aperture is on each end of the cross-linking element, so that when the cross-linking element is placed on the anterior surface of a plate, the cross-linking apertures align with the two channels of the plate. The apertures of a cross-linking element may have the same or different diameter as that of the plate aperture(s), and/or may have the same or different diameter as that of the width of the plate channels. An example of the present invention comprises a device having apertures of the same diameter, and having channel widths that are the same as the aperture diameters of the plate and the cross-linking elements. An example of the present invention comprises a device having apertures of the same diameter, and having channel widths that are the same as the aperture diameters or widths of the cross-linking elements. 
     An attachment cross-link is used for attaching the device to a bone, such as a vertebra. The attachment cross-link may have as many apertures as the plate has channels, for example, an attachment cross-link has two apertures that will align with two channels of a plate. An attachment cross-link is placed transversely across the anterior surface of a plate and an aperture of the attachment cross-link provides an opening though the cross-linking element and on through the channel opening of the plate. An attachment cross-link length may be shorter or longer than the width of the plate. An attachment cross-link may be as thick as or thinner than the thickness of the plate. An attachment cross-link may be textured on either its anterior or posterior surface, for example, so that texturing on its posterior surface meshes with texturing on the anterior surface of the plate, or either or both surfaces of the attachment cross-link may have a material that promotes bone in growth, bone growth, or aids in healing soft tissues. It is contemplated by the present invention that in use, an attachment cross-link is held with the device by the passing of a fastener such as a screw or pin through each of the aperture(s) of the attachment cross-link, through the channel opening of the plate and into the bone of the vertebrae. The head of the screw would engage with the attachment cross-link and the other end of the screw would be secured in the bone, and lock the attachment cross-link to the plate and the device to the bone. 
     A spacer cross-link is used for stabilizing the device. A spacer cross-link is placed transversely across the plate in the area of the channels where the attachment cross-link(s) is not present. In use, the spacer cross-links occupy the area between the proximal and distal ends of the plate where the channels are and provide stability to the device. A spacer cross-link may have as many apertures as the plate has channels, for example, a spacer cross-link has two apertures that will align with two channels of a plate. A spacer cross-link is placed transversely across the anterior surface of a plate and the two apertures of the spacer cross-link provide an opening though the cross-linking element and on through the channel opening of the plate. A spacer cross-link may be shorter or longer than the width of the plate. A spacer cross-link may be as thick as or thinner than the thickness of the plate. A spacer cross-link may be textured on either its anterior or posterior surface, for example, so that texturing on its posterior surface meshes with texturing on the anterior surface of the plate, or either or both surfaces of the spacer cross-link may have a material that promotes bone in growth, bone growth, or aids in healing soft tissues. It is contemplated by the present invention that in use, a spacer cross-link is held with the device by the passing of a fastener such as a short screw through each of the aperture(s) of the spacer cross-link, or by use of a spring loaded mechanism that clamps the spacer element to the plate, or by other methods of attachment. For example, the head of a short screw would engage with the anterior surface of the spacer cross-link and the other end of the screw may be flush with the posterior surface of the plate, which would lock the spacer cross-link to the plate. 
     A spacer cross-link may or may not be the same size, as in length, width, and/or thickness, as the attachment cross-link. For example, a system and device of the present invention comprise attachment cross-links and spacer cross links that are the same length, width and thickness, and have the same number and size apertures. Such a system and device would comprise only one type of cross-linking element that could be used for attachment and for spacing purposes. Such a system would use a fastener such as a screw, having only one diameter head, which may be provided in longer and shorter lengths, depending on the use of the cross-linking element, long for attachment and shorter for spacing. This would provide for use of only one type of screw driver. Such a system and device provides for uniform components to be used in implanting the device, and simplifies the methods and decisions performed by the surgeon. 
     Attachment elements of the present invention comprise fasteners, elements that interact intimately with the bone, or that attach cross-linking elements to a plate, such as bone screws, screws, bolts, pins, dual-headed pins, rivets, projecting elements, cements, plastics, or other components that may attach the plate to the bone or cross-linking elements to a plate. A description is provided herein comprising screws, but the invention is not necessarily limited to the use of only screws for this purpose. An aspect of the present invention provides for a device that allows for the placement of screws entering bone have sufficient angular freedom relative to the plate, in the variability of the axis of screw placement in the superior, inferior, medial and lateral directions. In the present invention, the surgeon may insert the bone screws into the vertebrae as to best to fit the anatomy of the individual patient, or multi-axial placement of a screw, such as at any angle up to 10-20 degrees from normal to the surface of the plate. The bone screws may be of a length that is sufficient for unicortical or bicortical placement. The bone screws may be self tapping, or may be inserted after tapping or drilling procedures, or after pin placement and removal. The bone screws may be locked into place with locking mechanisms known to those skilled in the art, such as a locking cap, locking ring, or a threaded cap. The screws used in the present invention for bone attachment may all be identical or different. For example, the screws used in the present invention are identical in length, width, and head design. For example, the screws used with attachment cross-links are identical to screws used with spacer cross-links in width and head design, but not in length. 
     Methods of the present invention comprise use of the systems and devices disclosed herein for treatment of spinal disease, damage or other conditions and pathologies. For example, a common approach for the surgical management of cervical disk disease is anterior cervical spinal fusion. The procedure for cervical spinal fusion is initiated by incising a small opening in the front of the neck. There is minimal trauma to the neck tissues. The damaged disk and/or bone spurs may be removed anterior to the spinal cord. This approach allows for minimal spinal or cord traction. Frequently, if there is significant spinal cord compression or if there is more than one disk level involved, a small plate is affixed on the anterior surface of the cervical vertebrae to provide greater permanent stability. 
     In a method of the present invention for anterior cervical spinal fusion, the following steps are performed. A template of a plate of the present invention may be used to determine placement of the plate, the attachment cross-links, the number of spacer cross-links needed, and the placement and angular location of the screws. A template is a replica of a plate of a particular length, and may be of a material that allows for visualization of the area under the template, i.e., may be transparent, and may be capable of having measurements written on it. The template may be used once the spinal vertebrae are exposed or may be used with x-rays or other visualization data. While the device components are being assembled based on the determinations made from the template placement, operating personnel may be preparing the vertebrae for insertion of screws, such as by pre drilling sites or tapping. Alternatively, no template is used and alternatively sized plates are used to make the determinations of placement and components. 
     A method of the present invention comprises temporary attachment of the plate to the vertebral bones. A plate may be held in place on the anterior spine temporarily by the use of pins, including, but not limited to, dual headed pins. The plate may be held in position using an instrument that allows for the insertion of temporary pins in apertures found at both the distal and proximal ends of a plate, or in the proximal and distal ends of elongated channels in plates that do not have end apertures. An inserter allows for a dual-head pin to be placed through the aperture or channel with visualization techniques, such as fluoroscopy. Use of the dual-headed pin and visualization allows the surgeon to determine the correct angle of placement for the screws that will follow the pins, to determine the correct length of the screws, and whether the plate is centrally and correctly aligned along the long axis of the vertebral bodies. 
     The dual-headed pins as disclosed herein are a single construct with an inserter that causes the pin heads to be placed in a parallel relationship. The placement of the pins under fluoroscopy aids in correct alignment in the sagittal and coronal planes. If the plate is correctly aligned coronally (not tilted to one side vertically), with lateral imaging, the dual pins will appear as one pin. If there is no or poor coronal alignment, two pins will show. If the pins are aligned coronally, but are not equally placed in the vertebral bodies, then under lateral visualization, the pins will be parallel, but one pin will appear to be deeper than the other pin. 
     The dual-headed pin, or any other pin known in the art, are contemplated to be of a sufficient size such that the placement in the bone and removal creates a tract or path for the bone screw or other fastener to follow. A pin or dual-headed pin may be disposable, in that it may be used only once, or may be reusable as long as the pin is structurally sound. 
     As an example, the surgeon can align the plate first and then select the best angle to place the pins under direct fluoroscopy. Pins, such as the dual-headed pin, may have pin heads of several lengths, ranging from about 8 to about 28 mm, from about 10 to about 25 mm, from about 12 to about 20 mm, from about 12 to about 16 mm, from about 15 to about 20 mm. Use of the pins allows for the estimation of the length of the bone screws to be used. The nonparallel angles of entry may prevent exact measurement of the length needed by the screws, but the present invention provides for a close approximation of the longest screws that can be safely used to attach the plate. 
     When elongated apertures are used, a dual-headed pin would be located in the upper portion of the upper (proximal) apertures, and the lower portion of the lower (distal) apertures, which would allow for translational dynamic movement once the device is assembled on vertebral bodies with screws or other attachment elements in place. For convenience, proximal and distal are in relation to the head, with items closer to the head being proximal. 
     To allow for true translational movement, the dual headed pin could have a 1-2 mm off-set on one side. This off-set would allow for pin placement in the upper end of the plate to have the off-set turned down and for pin placement in the lower end of the plate to have the off-set turned superior. The pins will fit into the upper portion of the upper (proximal) apertures and the lower portion of the lower (distal) apertures insuring the correct placement to allow translational dynamic movement. See  FIG. 3C  for a side view of a dual head pin with an offset, wherein the pin heads are offset from the central plane of the dual head pin. The b indicates the side of the pin with the offset, as does the ribbing on the handle  355 , to indicate in which direction the pin heads are offset. See  FIG. 3D  for an example of placement of two dual headed pins with offset pin heads. In  FIG. 3D , only one distal and proximal apertures are shown with pin placement and direction of the pin, indicated by a and b, are shown. The body of the pin is not shown. In practice, the dual headed pin with offset pin heads would be placed in the apertures, or in elongated channels, with the pins in the upper portion of the proximal apertures or channels and in the bottom of the lower (distal) apertures. The pin could be a single device that is flipped over for placement in either the upper or the lower apertures. The dual head pin could be labeled or color-coded to indicate the off set side. For example,  FIG. 3C  shows ribbing  355  on the side of the pin head offset for easy identification by a user. 
     In an embodiment where there are no end apertures and the at least two channels are elongated from the proximal area to the distal area, an aperture may be present in a central midline position between the channels. This central aperture may be used to provide minimal fixation of the plate without significant bone disruption during the initial placement of the plate for sizing. Once a pin is in place in the central aperture, differently sized plates could be placed on the pin to ascertain the correctly sized plate for that patient. Once the plate is selected, temporary dual-headed pins could be used to anchor the plate distally and proximally by putting in a pin at each end of the channels. The cross-linking elements and attachment elements such as bone screws can then be used to completely anchor the device to the vertebral bodies. The pins may be removed when the screws which replaced them are to be provided. Translational movement is possible with a plate having elongated channels without end apertures. 
     Once a compatible plate and attachment elements are determined, the plate may be attached to the selected vertebrae by providing temporary pin placements or by providing screws through the plate apertures to affix the plate at least at one end. The plate may be affixed to at least two vertebrae by providing screws through the distal and proximal end apertures, or by providing other attachment elements. The screws may follow a tract made by the placement and removal of a temporary pin, or one of the heads of a dual-headed pin. One or more attachment cross-links are added to the plate by providing temporary pins followed by screws or screws only or other fasteners only, through the attachment cross-link, through the channels of the plate and into the vertebral bone. Spacer cross-links are added to the plate, around the attachment cross-links, if necessary, or at least enough spacer cross-links are added to substantially cover the channels. The spacer cross-links may be attached by screws, spring loaded clamps, or other locking components. Once all of the determined attachment cross-links and spacer cross-links are added to the plate, the device is fully assembled and the surgical site may be closed. 
     Referring now in detail to the drawing figures, wherein like reference numerals represent like parts throughout the several views,  FIG. 1A  illustrates an exemplary embodiment of a plate  110  of an anterior cervical instrumentation system  100 . The plate  110  may be substantially flat, as shown, or curved, not shown, and may have a thickness ranging from 1-3 millimeters (mm). In an embodiment, the plate  110  may be 2 mm thick. The plate  110  may be rectangular in shape, having a proximal and distal end. The plate  110  may measure 12-120 mms in length and 14-18 mms in width. In an embodiment, the plate  110  may be approximately 18 mms long and approximately 16 mms wide. The edges and corners of the plate  110  may be square, or rounded or smoothed to reduce potential damage or trauma to surrounding bone and/or tissue when implanted. 
     The plate  110  is adapted to be implantable in the human body, for example, on the cervical portion of the spine. The plate  110  may be composed of a suitable biocompatible or sterilizable material such as stainless steel, titanium, titanium alloys, memory alloys, nitinol, amorphous metal alloys, plastic, ceramic compounds, polymer compounds, carbon fiber, or another suitable material. The plate may be texturized, treated or coated on a portion or all of one or more sides to aid in joining of component parts, for bone growth or enhancement, to provide antimicrobial function, or immune response control. 
     The plate  110  may comprise a first aperture  120   a  and a second aperture  120   b , both disposed at the proximal end of the plate  110 . The radius of the apertures  120   a  and  120   b  may be between 4-6 mms. In an embodiment, the radius of the apertures  120   a  and  120   b  may be approximately 4.6 mms. The radius of the apertures  120   a  and  120   b  may correspond to the diameter of bone screws that will be used to secure plate  110  to the bone at a target site. The distance between the centers of the aperture  120   a  and  120   b  may be between 6-12 mms. In an embodiment, the distance between the centers of the aperture  120   a  and  120   b  may be approximately 9 mms. The plate  110  may further comprise a third aperture  120   c  and a fourth aperture  120   d  disposed at the distal end of the plate  110 . The dimensions and arrangement of the third and fourth apertures  120   c  relative to the plate  110  may be substantially identical to the first and second apertures  120   a  and  120   b.    
     The interior perimeters of the apertures  120   a - d  may be substantially cylindrical. In such embodiments, the apertures  120   a - d  are adapted to interface with a round head surgical screw or fastener. The head of such a fastener may extend above the surface of the plate  110  when threaded through one of the apertures  120   a - d . This may not be optimal in situations where a minimal profile of the plate  110  and system  100  is desired. In other embodiments, at least a portion of the interior perimeter of the apertures  120   a - d  may be frusto-conical. In such embodiments, the apertures  120   a - d  may be adapted to interface and receive the angled surface of a flat head surgical screw or fastener. The head of such a fastener would be flush with the surface of the plate  110  when threaded though one of the apertures  120   a - d.    
     In exemplary embodiments of the plate  110 , the interior perimeter of the apertures  120   a - d  may be substantially smooth. The apertures  120   a - d  may be substantially wide enough to enable the entire width of the fastener, including the treads, to pass through. In such embodiments, the plate  110  would be secured to the surface of the bone at least partial due to the compression caused by tightening the screw or fastener. In other contemplated embodiments, the interior perimeter of the aperture  120   a - d  may be counter-threaded to correspond to the threading on a selected screw or fastener. In such embodiments, the fastener may be threaded through apertures  120   a - d  and engage the bone to provide a secure attachment of the plate  110  to the vertebrae. 
     The plate  110  may further comprise a first channel  130   a  and a second channel  130   b . The first and second channels  130   a  and  130   b  span the thickness of the plate  110  to provide elongated openings in the plate. The first and second channels  130   a  and  130   b  are elongate and extend in the distal-proximal direction. The first channel  130   a  may be disposed between and axially aligned with the first and third apertures  120   a  and  120   c . Similarly, the second channel  130   b  may be disposed between and axially aligned with the second and fourth apertures  120   b  and  120   d.    
     The channels  130   a  and  130   b  may be adapted to receive a fastener substantially similar to the fasteners used to secure plate  110  to the vertebrae through apertures  120   a - d  as described above. The width of the channels  130   a  and  130   b  may be substantially equal to the width of apertures  120   a - d . The length of the channels  130   a  and  130   b  may be between 14-100 mms. In an embodiment, the length of the channels  130   a  and  130   b  may be approximately 20 mms. The channels  130   a  and  130   b  may be centered between apertures  120   a - d  such that the ends of the channels  130   a  and  130   b  are equidistant from the nearest aperture  120   a - d.    
     The interior perimeter of the channels  130   a - 130   b  may be substantially smooth. This may enable the body of a fastener passing through the channels  130   a - 130   b  to smoothly translate in the distal to proximal direction. This feature allows for the attachment cross-links elements, described below, to “float” relative to the plate  110 . 
     The plate  110  may be adapted to attach to vertebrae using temporary pins, surgical screws or fasteners as described above as attachment elements. In particular, the plate  110  is adapted to be disposed on the anterior side of the cervical portion of the spinal column. In other contemplated embodiments, the plate  110  may by used in other regions of the spinal column or other bones of the body. 
       FIG. 1B  shows exemplary plates wherein the distal and proximal end apertures  120   e - h  are elongated, or wherein the proximal apertures  120   i,j  are elongated and the distal apertures  120   k,l  are round. For elongated apertures, the vertical length of the aperture may be 6-8 mm. The apertures and channels  130   c,d  may be as described in  FIG. 1A . 
       FIG. 1C  shows an exemplary plate wherein the channels  130   g  and  130   h  are located substantially from near the proximal end of the plate  110  to near the distal end of the plate  110 , and provide an opening from the anterior to the posterior sides of the plate  110 . There are no end apertures. A central midline aperture  120   m  is shown as an elongated aperture, but may be a round or other shaped aperture (not shown). The plate, aperture and channels may be as described for  FIGS. 1A and 1B . 
       FIG. 1D  illustrates a side view of an exemplary embodiment of a plate  110  attached to a region of the spinal column. The plate  110  may be attached to a first vertebra  150   a  by means of fasteners threaded through the first and second apertures  120   a  and  120   b  and engaging the bone. Because the depiction is a side view, it is difficult to distinguish in the illustration between the first and second apertures as one is directly behind the other. Further, the channels  130   a  and  130   b  are not depicted in the drawing. 
     The plate  110  may be positioned such that the proximal end is directly above the first vertebra  150   a . The surgeon may maneuver the plate  110  such that the first and second apertures  120   a  and  120   b  are directly over a target drill site, or a site for placement of a dual-headed pin, or two pins. The surgeon may mark the drill sites, remove the plate  110 , and use a guide to drill holes of the appropriate depth at the target drill sites. Alternatively, the surgeon may leave the plate in place and either use the plate as a drill guide or place a drill guide atop the plate to drill the necessary holes. Alternatively, the surgeon may leave the plate in place and provide a dual-headed pin through both apertures  120   a  and  120   b  simultaneously. A dual-headed pin or two pins may be placed through apertures  120   c  and  120   d . One of the dual-headed pins is then removed, and the surgeon may then attach the plate  110  to the first vertebra using the selected screw or fastener. The other dual-headed pin or two pins are removed, and screws are placed through the plate apertures and into the bone. 
     The above process may be substantially repeated to attach the distal end of the plate  110  to a second vertebra  150   b . This will lock the first and second vertebrae  150   a  and  150   b  in position relative to each other. The first and second vertebrae  150   a  and  150   b  are preferably on opposite sides of a target vertebra  150   c  or vertebrae undergoing treatment. The vertebra  150   c  undergoing treatment may be attached to the plate  110  using cross-linking elements, as will be described below. 
     Given the differences in anatomy and injuries between patients, and number of vertebrae undergoing treatment, the distance between suitable attachment sites on the first and second vertebrae may differ substantially from the distance between the first and second apertures  120   a  and  120   b  at the proximal end of the plate  110  and the third and fourth apertures  120   c  and  120   d  at the distal end. To enable optimal fitment, the system  100  may comprise a plurality of plates of variable lengths. 
       FIG. 2  illustrates an exemplary embodiment of a system having a plurality of plates. In this exemplary embodiment, the system  200  may comprise a first plate  210   a , a second plate  210   b , and a third plate  210   c . The plates  210   a - c  may be substantially identical in design and dimension to plate  110  with the exception of the overall length of the plates and the elongate channels. Alternatively, a system may comprise plates of differing lengths as shown in  FIG. 2 , but plates in each size may have differently shaped apertures, or a central aperture, and/or channels are exemplified in  FIGS. 1A-C . 
     The plates  210   a - c  each may have a different length. In one embodiment, the difference between the lengths of the plates may be in an increment substantially equal to the height of a vertebra. In such an embodiment, the first plate  210   a  could be intended to attach to a first and second vertebra, as described above, which have three target vertebrae undergoing treatment located there between. The second plate  210   b  could be adapted to be used when two vertebrae are undergoing treatment. Similarly, the length of the third plate  210   c  could make it suitable for situations where a single vertebra is undergoing treatment. 
     In other embodiments, the difference in length between the plates  210   a - c  may correspond to the difference in lengths between desirable drilling sites on the vertebra of patients. For example, plates  210   a - c  could be similar in length and adapted for use in situations where a single vertebra is undergoing treatment. The differences in the length of plates  210   a - c  could correspond to the difference in the size of vertebra of patients. This would enable a surgeon to intraoperatively select the appropriate length plate to attach to the vertebra of a patient. 
     In other contemplated embodiments, the plates  210   a - c  could have a wide range of lengths accounting for both applications with one or more target vertebra and vertebra of different sizes. In such embodiments, the system  200  may comprise more plates that the three illustrated. For example, the plates may incrementally vary in length to span an operational range from the shortest to the longest plate that may feasibly be used. 
       FIG. 3A  illustrates embodiments of cross-linking elements. The cross-linking element  340  may be constructed from the same material as the plate  110  described above. The cross-linking element  340  may be substantially equal in length to the width of plate  110 . The width of the cross-linking element  340  may be between 14-18 mms. In an embodiment, the cross-linking element may be 16 mm wide. The thickness of the cross-linking element  340  may be between 1-3 mms. In an embodiment, the cross-link may be 2 mm thick. 
     The cross-linking element  340  may comprise a first aperture  341   a  and a second aperture  341   b . The dimensions and distance between apertures  341   a  and  341   b  may be substantially similar to those of apertures  120   a  and  120   b.    
     The interior perimeters of the apertures  341   a  and  341   b  may be substantially cylindrical. In such embodiments, the apertures  341   a  and  341   b  are adapted to interface with a round head surgical screw or fastener. In other embodiments, a portion of the interior perimeter of the apertures  341   a  and  341   b  may be frusto-conical. In such embodiments, the apertures  341   a  and  341   b  may be adapted to interface and receive the angled surface of a flat head surgical screw or fastener. 
     In exemplary embodiments of cross-linking element  340 , the interior perimeter of the apertures  341   a  and  341   b  may be substantially smooth. The apertures  120   a - d  may be substantially wide enough to enable the entire width of the fastener, including the threads, to pass through. In other contemplated embodiments, the interior perimeter of the aperture  341   a  and  341   b  may be counter-threaded to correspond to the treads on a selected screw or fastener. 
     The cross-linking element  360  may be constructed from the same material as the plate  110  described above. The cross-linking element  360  may be substantially equal in length to the width of plate  110 . The width of the cross-linking element  360  may be between 14-18 mms. In an embodiment, the cross-linking element may be 16 mm wide. The thickness of the cross-linking element  360  may be between 1-3 mms. In an embodiment, the cross-linking element may be 2 mm thick. 
     The cross-linking element  360  may comprise a first aperture  361   a  and a second aperture  361   b . The dimensions and distance between apertures  361   a  and  361   b  may be substantially similar to those of apertures  120   a  and  120   b.    
     The cross-linking element  370  may be constructed from the same material as the plate  110  described above. The cross-linking element  370  may be substantially equal in length to the width of plate  110 . The width of the cross-linking element  370  may be between 14-18 mms. In an embodiment, the cross-linking element may be 16 mm wide. The thickness of the cross-linking element  370  may be between 1-3 mms. In an embodiment, the cross-linking element may be 2 mm thick. 
     The cross-linking element  370  may comprise a first aperture  371   a  and a second aperture  371   b . The dimensions and distance between apertures  371   a  and  371   b  may be substantially similar to those of apertures  120   a  and  120   b.    
       FIG. 3B  shows an exemplary dual-headed pin  350 . The pin has two pin heads  351  and  352 , and a handle  353 . The pin heads may be from 12-20 mm and a system may comprise one or more dual-headed pins having at least one of each of the 12-20 mm lengths. The handle  353  may be of any length that is suitable for holding or tapping by the surgeon. 
       FIG. 4A  illustrates a top view of a plate and cross-linking elements of an exemplary embodiment of the system. In an exemplary embodiment, the system  400  may comprise a plate  410  having apertures  420   a - d , and cross-links. The plate  410  and cross-linking elements may be substantially similar to the plates and cross-linking elements described above. Cross-linking elements may be employed either as a spacer cross-link or as an attachment cross-link. In an embodiment, the system  400  comprises attachment cross-link  440  and  470 , a first spacer cross-link  450 , and a second spacer cross-link  460 . 
     The attachment cross-link  440  may be coupled to the plate  410  by threading fasteners through apertures  441   a  and  441   b  and channels  430   a  and  430   b , and engaging the vertebra disposed below the plate. In an embodiment, the attachment cross-link  440  is not fixed in position relative to plate  410 . Rather, attachment cross-link  440  may move atop the plate  410  as the fasteners glide though channels  430   a  and  430   b.    
     The attachment cross-link  470  may be coupled to the plate  410  by threading fasteners through apertures  471   a  and  471   b  and channels  430   a  and  430   b , and engaging the vertebra disposed below the plate. In an embodiment, the attachment cross-link  470  is not fixed in position relative to plate  410 . Rather, attachment cross-link  470  may move atop the plate  410  as the fasteners glide though channels  430   a  and  430   b.    
     Spacer cross-links  450  and  460  may be disposed on both sides of the attachment cross-link  440  and proximal to cross-link  470  to limit their degrees of motion. In an exemplary embodiment, the first spacer cross-link  450  may be attached to the plate  410  on the proximal side of the attachment cross-link  440 . The second spacer cross-link  460  may be attached on the distal side of the attachment cross-link  440 , and proximal to attachment cross-link  470 . The spacer cross-links  450  and  460  may be attached to the plate  410  using a fastener, such as a hole to hole clamp, a screw head, or short screw, by means of channels  430   a  and  430   b  and apertures  451   a ,  451   b ,  461   a , and  461   b . The spacer cross-links  450  and  460  may be fixed in position relative to the plate  410  upon attachment to the plate. In other contemplated embodiments, the spacer cross-links  450  and  460  may be spring loaded or employ spring loaded fastening elements to attach to the plate  410 . There are multiple different spring loaded fastening elements known in the art and the decision for which fastening elements to use is within the knowledge of those skilled in the art. 
     The attachment position of spacer cross-links  450  and  460  may be selected to limit the range of motion of the attachment cross-links  440  and  470  as desired. The cross-links minimize rotational movement. Upon coupling to the plate  410 , spacer cross-links  450  and  460  define how far attachment cross-links  440  and  470  may move along the plate  410  on channels  430   a  and  430   b , as illustrated by the dashed arrows. 
       FIG. 4B  illustrates a top view of a plate and cross-linking elements of an exemplary embodiment of the system. In an exemplary embodiment, the system  410  may comprise a plate  410  having only a central aperture  420   e , two channels that are located from an area near the proximal end to an area near the distal end, and cross-linking elements. The plate  410  and cross-linking elements may be substantially similar to the plates and cross-linking elements described above. Cross-linking elements may be employed either as a spacer cross-link or as an attachment cross-link. In an embodiment, the system  410  comprises attachment cross-links  445 ,  475  and  490 , and spacer cross-links  455 ,  465  and  480 . 
     The attachment cross-links  445 ,  475  and  490  may be coupled to the plate  410  by threading fasteners through apertures  446   a  and  446   b ,  476   a  and  476   b ,  491   a  and  491   b , respectively, and through channels  435   a  and  435   b , and engaging the vertebrae disposed below the plate. In an embodiment, the attachment cross-links  445 ,  475  and  490  are not fixed in position relative to plate  410 . Rather, attachment cross-link  445 ,  475  and  490  may move atop the plate  410  as the fasteners glide though channels  435   a  and  435   b.    
     Spacer cross-links  455 ,  465  and  480  may be disposed on the plate  410  to limit the degrees of motion of attachment cross-links  445 ,  475  and  490 . In an exemplary embodiment, spacer cross-link  455  may be attached to the plate  410  on the proximal side of the attachment cross-link  445 . Spacer cross-link  465  may be attached on the distal side of the attachment cross-link  445 , and proximal to attachment cross-link  475 . Spacer cross-link  480  may be attached on the proximal side of the attachment cross-link  490 . The spacer cross-links  455 ,  465  and  480  may be attached to the plate  410  using a fastener, such as a hole to hole clamp, a screw head, or short screw by means of channels  435   a  and  435   b  and apertures  456   a ,  456   b ,  466   a , and  466   b ,  481   a  and  481   b , respectively. The spacer cross-links  455 ,  465  and  480  may be fixed in position relative to the plate  410  upon attachment to the plate. In other contemplated embodiments, the spacer cross-links  455 ,  465  and  480  may be spring loaded or employ spring loaded fastening elements to attach to the plate  410 . There are multiple different spring loaded fastening elements known in the art and the decision for which fastening elements to use is within the knowledge of those skilled in the art. 
     The attachment position of spacer cross-links  455 ,  465  and  480  may be selected to limit the range of motion of the attachment cross-links  445 ,  475  and  490  as desired. The cross-links minimize rotational movement. Upon coupling to the plate  410 , spacer cross-links  455 ,  465  and  480  define how far attachment cross-links  445 ,  475  and  490  may move along the plate  410  on channels  430   a  and  430   b , as illustrated by the dashed arrows. The attachment cross-links are also limited in movement by the ends of the channels  435   a  and  435   b.    
     In other contemplated embodiments, multiple attachment cross-links could be used with a multiple spacer cross-links. For example, a spacer cross-link could be attached to the middle of the plate and attachment cross-links placed on either side. The ends of the channels  435   a  and  435   b  and the spacer cross-link would limit the range of motion of the attachment cross-links. In other embodiments, various configurations and spacer and attachment cross-links are contemplated to attain a desirable result for a particular application. 
       FIG. 5  illustrates a side view of an exemplary embodiment of the device  500  and system attached to a spinal column. Plate  510  may be attached to a first vertebra  550   a  and a second vertebra  550   b  in substantially the same manner as plate  110  described above, using fasteners through apertures  520   a - d . The attachment cross-link  540  may be placed atop plate  510  and attached to the a target vertebra  550   c  by passing a fastener  580  through the apertures of the cross-link  540  and channels (not pictured) of the plate  510  and engaging with a hole in the vertebra  550   c.    
     Spacer cross-links  550  and  560  may be attached to the plate in a fixed position as described above. The attachment cross-link  540  may move along plate  510  as the fasteners glide through the channels of the plate  510 . The movement of the attachment cross-link  540  is limited by the spacer cross-links  550  and  560 . Attachment cross-link  540  may move upward until it comes in contact with the first spacer cross-link  550 . Similarly, attachment cross-link  540  may move downward until it comes in contact with the second spacer cross-link  560 . 
     Movement of attachment cross-link  540  enables the target vertebra  550   c  to move up and down, relative to the first and second vertebrae  550   a  and  550   b . This movement or subsidence allows for bone-to-bone contact. 
     The various embodiments described above are intended to enable a surgeon to intraoperatively customize the anterior cervical instrumentation system for optimal application. Consequently, the embodiments described above are merely exemplary and not limiting. In particular, the configurations, dimensions and orientation of components described above may be modified from what has been recited and described without departing from the design of the invention. Further, embodiments of the present invention are not limited to applications in the anterior region of the spine. Particularly, the embodiments of the present invention can also be used in the thoracic and lumbar regions.