Abstract:
A system for performing surgical repair of the spine includes a distractor and a permanently implanted bone plate system. A surgical repair methodology is also disclosed that employs an implanted bone plate system with a substantially void internal volume which is attached to adjacent vertebrae subsequent to the distraction and adjustment of curvature of the vertebrae and prior to the excision of disc and/or end plate tissue through the bone plate. The device further facilitates the subsequent delivery of an interbody repair device for the purpose of either fusion or dynamic stabilization, such as by disc arthroplasty. The plate may be permanently implanted, such as when a fusion between the attached vertebral bodies is desired, but it need not be permanently implanted

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. patent application Ser. No. 11/855,124 entitled “Implantable Bone Plate System and Related Method for Spinal Repair”, filed Sep. 13, 2007, which claims priority to U.S. Provisional Patent Application Ser. No. 60/954,511 entitled “Implantable Bone Plate System and Related Method for Spinal Repair”, filed Aug. 7, 2007. Each patent application is incorporated herein by reference in its entirety. 
     
    
       [0002]    The present invention relates to a system for performing surgical repair of the spine, such as for but not limited to the delivery of an interbody repair device for the purpose of either fusion or dynamic stabilization. 
       BACKGROUND 
       [0003]    It is current practice in spinal surgery to use bone fixation devices to improve the mechanical stability of the spinal column and to promote the proper healing of injured, damaged or diseased spinal structures. Typically, corrective surgery entails the removal of damaged or diseased tissue, a decompression of one or more neural elements, followed by the insertion of an intervertebral implant for the purposes of a fusion or disc arthroplasty. In cases where spinal fusion is the desired surgical outcome, the final step is often to apply a bone plate in order to immobilize adjacent vertebral bones to expedite osteogenesis across said vertebral segments. 
         [0004]    Most current surgical techniques require that damaged vertebral tissue be placed under rigid axial distraction throughout much of the procedure. This allows for greater ease in the removal of tissue, provides a larger working space for instrument maneuverability, enhances the surgeon&#39;s visibility and assists with the fit of the interbody implant once the distractor apparatus is removed. Conventional distraction of the spine typically employs the use of temporary “distractor pins” placed directly into the bone tissue adjacent to the disc space to be repaired, which are subsequently induced to move axially by the attachment and adjustment of a secondary tool. An alternative method employs the use of a ratcheting spreader device which is inserted directly into the vertebral interspace and is adjusted thereafter to achieve desired distraction. These distraction methods offer an imprecise means to restore preferred vertebral alignment, add several steps, require more time to install and remove, increase the risk for entwining of surrounding vascular structures or peripheral nerves and can present significant physical impediments and technical challenges to the surgeon. Additionally, because the distractor device remains temporarily inserted during the decompression and fusion portions of the procedure, the surgeon must essentially work around the obtrusive projecting devices while completing the majority of the surgery. 
         [0005]    It is also known that current distraction methods, while generally not designed or intended for this purpose, are often employed to adjust or maintain the angular alignment of adjacent vertebra in an attempt to restore normal lordotic curvature. The outcomes are varied, the degree of distraction and the angular correction produced by current distraction methods are often imprecise, require substantial subjective assessment by the surgeon and can vary significantly from patient to patient. Further, excessive distraction can result in a negative surgical outcome which can result in nerve damage or on-going post surgical pain for the patient. 
         [0006]    There is a high degree of dimensional variability in the resulting intervertebral volume after distraction has been achieved using these devices. As a result, the surgeon must often make “trial and error” assessments as to the size and shape of the interbody implant to be inserted and may be required to customize the implant intraoperatively prior to final insertion. 
         [0007]    In the conventional method, once the implant has been inserted, the distractor device is removed and the vertebrae can be secured by the attachment of a bone plate. Such bone plates, including a plurality of bone screws, are applied near the completion of the procedure to provide vertebral fixation and prohibit undesirable migration of the intervertebral implant. 
         [0008]    Several design constructs have already been proposed in which a device is applied to adjacent vertebrae at the start of a procedure, prior to tissue removal, for the purposes of achieving and maintaining preferred vertebral alignment while serving also to constrain tissue removal throughout the procedure. The disclosed or published art in this method can generally be categorized into two broad categories: removable devices and permanently implantable devices. 
         [0009]    The removable devices differ from the present proposed invention in that the devices used to maintain preferred vertebral alignment are temporary inserts and are subsequently removed after tissue removal so that a repair device may be delivered thereafter. The prior art which discloses permanently implantable devices differs in that the devices function solely to maintain preferred vertebral alignment and are not part of a comprehensive system and related method to precisely control and permanently maintain the preferred spatial relationship of adjacent vertebral members for controlled tissue removal and delivery of a repair device. 
       Removable Devices 
       [0010]    U.S. Pat. No. 7,153,304 entitled Instrument System for Preparing a Disc Space Between Adjacent Vertebral Bodies to Receive a Repair Device, issued Dec. 26, 2006 to Robie et al., discloses a removable instrument system for preparing a disc space between adjacent vertebral bodies using a series of distractors that restore natural lordosis before a temporary template is attached for vertebral immobilization and to function as a guide for an insertable reamer meant for tissue removal. 
         [0011]    U.S. Pat. No. 7,083,623 to Michelson, entitled Milling Instrumentation and Method for Preparing a Space Between Adjacent Vertebral Bodies, issued Aug. 1, 2006, discloses a removable milling device and method for preparing a space between adjacent vertebral bodies which essentially maintains preferred vertebral alignment while functioning as a saw guide to control bone and soft tissue removal. 
         [0012]    US Pat. App. 2005/0043740 to Haid, entitled Technique and Instrumentation for Preparation of Vertebral Members, published Feb. 24, 2005, discloses a removable instrumentation set and technique for preparation of vertebral members utilizing a docking ring which is temporarily applied to the anterior spine to maintain preferred vertebral alignment and to function as a docking plate for an articulating bone removal device. 
         [0013]    U.S. Pat. No. 7,033,362 to McGahan, entitled Instruments and Techniques for Disc Space Preparation, issued Apr. 25, 2006, discloses a removable instrumentation set and method for disc space preparation whereby an intervertebral device is temporarily inserted for the purpose of constraining tissue removal and guiding the position of an intervertebral repair device. 
         [0014]    US Pat. App. 2003/0236526 to Van Hoeck, entitled Adjustable Surgical Guide and Method of Treating Vertebral Members, published Dec. 25, 2003, discloses a removable surgical guide and method with adjustable functionality for the preparation of adjacent vertebra. 
         [0015]    US Pat. App. No. 2006/0247654 to Berry, entitled Instruments and Techniques for Spinal Disc Space Preparation, published Nov. 2, 2006, discloses a removable milling instrument assembly for vertebral endplate preparation which constrains a cutting path obliquely oriented to the axis of the vertebra. 
       Permanently Implanted Devices 
       [0016]    US Pat. App. 2004/0097925 to Boehm, entitled Cervical Spine Stabilizing System and Method, published May 20, 2004, discloses a permanently implantable spine stabilizing system and method whereby a plate configured to be positively centered along the midline is placed to retain adjacent vertebra in a desired spatial relationship during discectomy and fusion procedures. The disclosed invention uses a series of temporary implants and removable drill templates in an attempt to assure the alignment of the implanted device along the midline of the spinal column. This alignment is typically not considered to be significant in determined the clinical outcome of the procedure and is further considered impractical for the purposes of performing repair procedures on multiple adjacent disk spaces due to the normal scoliotic curvature of the spine. 
         [0017]    US Pat. App. 2005/0149026 to Butler et al., entitled Static and Dynamic Cervical Plate Constructs, published Jul. 7, 2005, describes an implanted cervical bone plate having a graft window located between the bone screw holes for the purposes of providing visualization and access to an intervertebral implant. The device described is applied after the intervertebral space has been repaired and after the implant has been positioned. The specification states specifically that an appropriately “sized dynamic plate is placed over the inserted bone implant”; thereafter the bone plate is located with respect to the implant by viewing the implant through the graft window and secured in place using bone screws. 
         [0018]    Additional bone plate devices are disclosed in U.S. Pat. No. 3,741,205 to Markolf et al, and US Pat. Apps. 2005/0149026 to Butler et al. and  2007 / 0233107  to Zielinski. 
         [0019]    Accordingly, it is apparent that there remains a need for and advantage to a permanently implantable spinal repair system and related method whereby the final preferred vertebral alignment and fixation occurs prior to the surgical removal of damaged tissue, without the use of temporary implants or fasteners and where the surgical procedures can be performed there-through in the minimum amount of time with the minimum number of entries into the surgical field. It is further apparent that there is a need for a system wherein subsequent recovery procedures can be performed with minimal effort should implantation fail or should subsequent surgery be required. 
       SUMMARY OF THE DISCLOSURE 
       [0020]    The invention relates generally to systems and methods for establishing and securing adjacent vertebrae in a defined spacial relationship prior to the excision and repair of damaged tissue. In one embodiment, the system includes at least one distraction device, at least one implantable vertebral frame, at least one interbody repair implant, and at least one retention member. In this embodiment, the distraction device is configured for temporary placement between adjacent vertebrae for achieving a desired spatial relationship between the vertebrae. In this embodiment, the implantable vertebral frame is configured to span between the adjacent vertebrae, the frame being configured to attach to each of the adjacent vertebra while the distraction device is in place to postoperatively maintain the desired spatial relationship between the vertebrae after the distraction device is removed, the frame also having at least one internal operating aperture there-through for providing access to at least one intervertebral disk space. In this embodiment, the interbody repair implant is sized in relationship to the aperture of the frame to fit there-through and into the intervertebral space. And finally, in this embodiment, the retention member is attachable to the frame to cover at least a portion of the aperture. 
         [0021]    In various embodiments of the above summarized system, the frame may assume various forms and include various features that will now be summarized. In some embodiments of the system, the frame may be configured to span between and remain postoperatively attached to at least three adjacent vertebrae. In some embodiments of the system, the frame may include external walls having integrally manufactured retractor blade engaging features. In some embodiments of the system, the frame may have a plurality of through holes to facilitate attachment of the frame to adjacent vertebrae by means of bone screws. In some of these particular embodiments, the holes may be a combination of elongated slots and circular holes to accommodate the insertion of bone screws there-through into vertebral bone tissue. In some embodiments of the system, the frame may have a plurality of protrusions to facilitate attachment of the frame to the adjacent vertebrae by means of impingement into the bone tissue of the adjacent vertebrae. 
         [0022]    Further, in some embodiments of the system, the frame may have one or more receiving elements to accept a locking member for securing the retention member. In various of these particular embodiments, the locking member may be any of a threaded screw device, a snap lock device, or a cam lock device, and further in some of these particular embodiments, the one or more receiving elements for the retention member may accommodate the temporary location of at least one tissue retractor pin. 
         [0023]    Still further, in some embodiments of the system, the frame may be configured to receive bone screws there-through to attach the frame to the vertebrae, the retention member being adapted to cover the bone screws when the member is attached to the frame to prevent back-out of the screws. 
         [0024]    In some embodiments of the system, the retention member may be configured to retain the interbody implant in its surgically established position. 
         [0025]    According to an aspect of the invention, a vertebral implant may be provided. Embodiments of the implant are configured to rigidly interconnect at least two vertebrae, the implant being manufactured from a generally rigid material having thereon contact surfaces for engaging on vertebral bone material, the contact surfaces including a biocompatible, compressible, polymeric material. In some of these embodiments, the generally rigid material may also include a biocompatible metallic material. 
         [0026]    In another aspect of the invention, various embodiments of methods are provided for applying the system and/or the vertebral implant, as summarized above. In one method of applying the system, the adjacent vertebrae are distracted and spacially oriented with the distraction device, the vertebral frame is secured to the adjacent vertebrae, the damaged tissue is excised through the operating aperture in the vertebral frame, the vertebral interspace is prepared to receive the repair implant, said implant being placed through the operating aperture into said prepared interspace, and the retention member is then installed onto the vertebral frame. 
         [0027]    Another embodiment of a method for applying the system is also provided. In this embodiment, the vertebral frame is attached to one or more vertebrae, the vertebrae are then distracted and spacially oriented by operating through the operating aperture in the vertebral frame, the vertebral frame is secured to each adjacent vertebrae, the damaged tissue is excised through the operating aperture in the vertebral frame, the vertebral interspace is prepared through the operating aperture to receive the repair implant, the interbody implant is inserted through the operating aperture into the prepared interspace and the retention member is installed onto the vertebral frame. 
         [0028]    In another aspect of the invention, a method for treating a portion of a spinal column is provided. The method includes distracting and spacially orienting adjacent vertebral bodies of the spinal column, securing a vertebral frame to the adjacent vertebral bodies, the vertebral frame having at least one operating aperture there-through, preparing a vertebral interspace to receive an interbody implant, inserting the interbody implant through the operating aperture and into the prepared interspace, and maintaining the vertebral frame in place on the vertebral bodies postoperatively. 
         [0029]    In some embodiments of this method for treating a portion of a spinal column, the distracting step is performed using a distraction device placed between the vertebral bodies, and the distraction device is removed from between the vertebral bodies through the operating aperture in the vertebral frame after the vertebral frame is secured to the vertebral bodies. In some of these methods for treating a portion of the spinal column, the method may further include the step of excising damaged tissue through the operating aperture in the vertebral frame. In another embodiment, the method may further include the step of installing a retention member onto the vertebral frame after inserting the interbody implant. In still other embodiments, the step of preparing a vertebral interspace to receive an interbody implant may be performed through the operating aperture of the vertebral frame. 
         [0030]    In some embodiments of the method for treating a portion of the spinal column, the vertebral frame may have particular features or aspects. Thus, in some embodiments, the vertebral frame may be attached to at least one of the vertebral bodies before the distraction step, the distraction step being performed through the operating aperture in the vertebral frame. In other embodiments, the vertebral frame may be secured to more than two adjacent vertebral bodies. In still other embodiments, the vertebral frame may be maintained in place permanently, generally from the time it is first secured to the vertebral bodies. 
         [0031]    According to some aspects of the present invention, a means and method to precisely control and permanently maintain the preferred spatial relationship of adjacent vertebral members prior to the surgical removal of damaged tissue may be provided. 
         [0032]    According to some aspects of the invention, a means may be provided whereby preferred spatial relationship of adjacent vertebra can be achieved and permanently maintained using conventional vertebral distraction methods or in conjunction with a novel intervertebral distractor apparatus disclosed separately in the co-pending patent application Ser. No. 60/954,507 titled “Device and Method for Variably Adjusting Intervertebral Distraction and Lordosis” filed on Aug. 7, 2007. 
         [0033]    According to some aspects of the invention, the surgical removal of damaged tissue may be constrained in order to minimize the risk of damage to the adjacent tissue. 
         [0034]    According to some aspects of the invention, the preferred spatial relationship of adjacent vertebral members may be precisely controlled and permanently maintained with a device having a low profile, allowing the surgeon to work in an unrestricted manner, within, around, above and below the device. 
         [0035]    According to some aspects of the invention, the preferred spatial relationship of adjacent vertebral members may be precisely controlled and permanently maintained for the insertion of a spinal repair device. 
         [0036]    According to some aspects of the invention, the insertion of a spinal repair device may be spatially controlled. 
         [0037]    According to some aspects of the invention, a locking member may be accommodated to prevent undesirable migration of the spinal repair device and bone screws. 
         [0038]    According to some aspects of the invention, the method and device may be utilized across one or multiple vertebral segments. 
         [0039]    According to some aspects of the invention, a permanent rigid internal fixation may be provided across one or multiple vertebral segments. 
         [0040]    In one particular embodiment, a permanent semi-rigid fixation is provided across one or multiple vertebral segments. 
         [0041]    In one particular embodiment, a retractor apparatus is accommodated by providing integrally manufactured receiving and engaging means for the tissue control blades of said retractor. 
         [0042]    In one particular embodiment, removable templates which locate and constrain the surgical removal of tissue to the desired vertebral area are accommodated. 
         [0043]    In one particular embodiment the vertebral fixation element in the system is manufactured using two biocompatible materials, the structural component being manufactured from a high modulus rigid material such as Titanium, Stainless steel or other metal and having therein contact elements for engaging on the vertebral tissue, said contact pads being manufactured from a bio-compatible compliant material such as polyethylene or a silicone. These contact pads are intended to be plastically deformed under compressive loads and to be compressed and deformed by the insertion of the bone screws in order to act as damping elements to absorb vibration during bone tissue removal and consequently to minimize the risk of associated screw dislocation. These pads further increase the initial friction between the vertebral fixing element and the vertebrae thereby reducing premature dynamic compression of the distracted vertebrae. Finally, the compliant elements act as shock absorbers during patient healing and promote osteogenesis within the implanted repair device. 
         [0044]    In one particular embodiment, the inventive device may be coupled with a stereotactic navigational system for preferred device positioning and to constrain the surgical removal of tissue. 
         [0045]    According to aspects of the invention, a system and surgical method for use in surgical spinal repair or reconstruction procedures are described herein, whereby preferred and final vertebral axial and angular positioning and fixation occurs prior to the cutting and removal of the tissue. 
         [0046]    In one embodiment, the system can generally be described as a combination of:
       1) An intervertebral distraction device placed temporarily between adjacent vertebrae for purposes of achieving a desired spatial relationship between adjacent vertebrae.   2) A vertebral plate.   3) A locking and retention member engaging with said vertebral plate.   4) An implantable interbody repair device.   5) Bone screws.   6) The vertebral plate having through holes for the purposes of accommodating attachment to the vertebrae using the bone screws.   7) Said vertebral plate having a generally open interior volume through which the removal of damaged tissue is performed.   8) Said vertebral plate having a generally open interior volume which constrains the insertion and prevents migration of an intervertebral repair device.   9) Said vertebral plate having accommodation means for attaching the locking and retention member for retention of the implanted repair device and the bone screws.   10) One embodiment of the surgical method may be generally described as the sequence of spacially orienting adjacent vertebrae, locking said vertebrae in their prescribed relative positions using the vertebral plate and bone screws, preparing and repairing the intervertebral space through the operating window in the installed vertebral plate and securing the implant in place by securing a locking member to the vertebral plate.   11) An alternate surgical method may be generally described as the sequence of attaching the vertebral plate to one of the adjacent vertebrae, spacially orienting the adjacent vertebrae through the operating window in the vertebral plate, locking said vertebrae in their prescribed relative positions using the vertebral plate and bone screws, preparing and repairing the intervertebral space through the operating window in the installed vertebral plate and securing the implant in place by securing a locking member to the vertebral plate.   12) In an alternate surgical method, the vertebrae are partially distracted and held in this position by the insertion of bone screws through slots in the vertebral plate. In this instance the final distraction is achieved by the forcible insertion of an interbody repair device which has a cranio-caudal dimension that is larger than the dimension of the receiving intervertebral space. The differences in the two dimensions results in a further, final distraction of the adjacent vertebrae. This final movement of the vertebrae is accommodated by the movement of the screws within the slots in the vertebral plate.       
 
         [0059]    In an anticipated procedure a conventional intervertebral distractor apparatus is manually inserted into or between the vertebrae resulting in axial distraction of the vertebrae. In the case of a standard wedge style distractor the degree of distraction results from a combination of the included angle and the depth to which it is inserted between the vertebrae. In the case of a distractor pin system the distraction results from the manipulation of a secondarily applied axial adjustment device. 
         [0060]    In a further embodiment the included angle of the distractor device is variably adjustable by the surgeon after insertion between the vertebrae, this adjustment being achieved mechanically by means of a screw adjustment or the use of another adjusting tool. Such a distractor device is disclosed in application Ser. No. 60/954,507 titled “Device and Method for Variably Adjusting Intervertebral Distraction and Lordosis” filed Aug. 7, 2007. 
         [0061]    In a further embodiment the distractor apparatus can be mated with a stereotactic navigational device to establish, monitor and control the positioning of the device relative to the adjacent vertebra. 
         [0062]    After distraction and lordotic adjustment has been achieved the spinal bridge is located on the vertebrae relative to the distractor device and attached to the adjacent vertebra by at least two bone screws, securing the vertebrae in their prescribed positions. 
         [0063]    If intervertebral distractor devices have been employed they are removed, exposing a predefined accessible and constrained operating field allowing the controlled cutting and removal of tissue to occur. 
         [0064]    In a further embodiment the vertebral plate can accommodate insertable control templates which can be placed within it by the surgeon to further assist precise tissue removal. 
         [0065]    In a further embodiment the vertebral plate can serve as a mounting base for the attachment of soft tissue retractors, further aiding the surgeon by assuring an un-impeded surgical field. 
         [0066]    In a further embodiment the vertebral plate can be removed after the placement of a disc arthroplasty device. 
         [0067]    The intervertebral repair device may be generally wedge shaped, it may have an initial radius or taper for engagement with the adjacent vertebrae or it may be conically or cylindrically shaped. 
         [0068]    Further, this device may have surface contours thereon which are intended to increase the surface area of contact between said surfaces and the exposed cancellous bone tissue and to increase the intimate compressive engagement with said cancellous tissue so as to induce and encourage osteogenesis therein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0069]      FIG. 1   a  shows the typical sequence of steps in a current surgical procedure. 
           [0070]      FIG. 1   b  shows the sequence of one embodiment of the inventive method herein. 
           [0071]      FIG. 2   a  is an anterolateral isometric view of a single level implantable bone plate. 
           [0072]      FIG. 2   b  is a posterolateral isometric view of a single level implantable bone plate. 
           [0073]      FIG. 3   a  is an anterior isometric view of a multi-level implantable bone plate. 
           [0074]      FIG. 3   b  is a lateral isometric view of a multi-level implantable bone plate. 
           [0075]      FIG. 4  is an oblique perspective view of a multi-level bone plate. 
           [0076]      FIG. 5  illustrates a retention member relative to the vertebral frame. 
           [0077]      FIG. 6  depicts a retention member in an installed position on the vertebral frame. 
           [0078]      FIG. 7  is an anterior (surgical) view of a vertebral frame in its installed position on adjacent vertebrae. 
           [0079]      FIG. 8  is an anterolateral perspective view of the vertebral frame in its installed position on adjacent vertebrae. 
           [0080]      FIGS. 9 and 10  depict a retention member in-situ after installation onto the vertebral plate. 
           [0081]      FIGS. 11A-11E  show another embodiment of an implantable bone plate. 
           [0082]      FIG. 11F  is a side view showing an exemplary bone screw for use with the implantable bone plate of  FIGS. 11A-11E . 
           [0083]      FIGS. 12A-12F  show an exemplary cover plate for use with the implantable bone plate of  FIGS. 11A-11E . 
           [0084]      FIG. 12G  is a perspective view showing an exemplary locking arm for use with the cover plate of  FIGS. 12A-12F . 
           [0085]      FIGS. 13A-13G  show an exemplary instrument guide tool for use with the implantable bone plate of  FIGS. 11A-11E . 
           [0086]      FIGS. 14A-14C  show an exemplary tissue retractor being used with an implantable bone plate mounted on a vertebral body. 
           [0087]      FIGS. 15A-15C  show an exemplary interbody repair implant. 
           [0088]      FIGS. 16A-16C  show an exemplary intervertebral distraction device. 
           [0089]      FIGS. 17A-17X  show an exemplary spinal fusion surgical procedure. 
       
    
    
     DETAILED DESCRIPTION 
       [0090]      FIG. 1   a  describes the typical operational sequence currently employed, wherein vertebrae are distracted, tissue is excised, an implant in placed between adjacent vertebrae and a bone plate is attached.  FIG. 1   b  describes the preferred operational sequence associated with this invention, wherein vertebrae are distracted and placed in their preferred relative angular positions and a vertebral frame is attached to adjacent vertebrae using bone screws to maintain the prescribed spatial relationship during the subsequent steps. In an alternative sequence, the vertebral frame may be attached to adjacent vertebrae prior to distraction and preferred positioning. Thereafter tissue is excised though the aperture in the frame, the implant is inserted through said aperture. A retaining member may be attached to said vertebral frame to maintain the position of the implanted insert and to prevent back-out of the bone screws. 
         [0091]      FIGS. 2   a  and  2   b  depict a single level vertebral frame  100 , intended to secure two adjacent vertebrae. The device has surfaces  101  and  102  which are generally contoured to engage positively with the anterior surfaces of the adjacent vertebrae. The device has through holes  103  and  104  intended to accommodate the insertion of bones screws into the vertebral tissue. Holes  104  may be elongated to accommodate post surgery dynamic settling of the vertebrae. The device further has one or more holes  105  intended for receiving screws (or other fixation devices) securing the retaining member thereto or there-through. The receiving holes  105  also provide a mounting means for the insertion of temporary soft tissue retractor pins. The device has an operating window defined by the side walls  106 ,  107 ,  108  and  109 . This window is intended to allow unimpaired access to the intervertebral space in order to excise tissue and subsequently to allow the insertion of the interbody repair device there-through. 
         [0092]      FIG. 3   a  depicts a multi-level vertebral frame  200 , intended to facilitate the orientation, fixation and repair of three or more vertebrae. 
         [0093]      FIG. 3   b  depicts a side view of a multilevel device and illustrates the presence of a receiving means  201  on the vertebral frame, thereby permitting the plate to accommodate the location and retention of soft tissue retractor blades. 
         [0094]    Referencing  FIGS. 4 and 5 ; the retention member  300  has a posterior surface  301  contoured to match the anterior surface of the vertebral frame  200  and through holes  302  which align with the receiving holes  105  in the vertebral frame, these holes being intended to secure the retention member  300  to the vertebral frame  200  in order to retain the interbody implant in position and to prevent the back-out of the bone screws used to secure frame  200  to the vertebral bone tissue. 
         [0095]      FIG. 6  shows retention member  300  installed to the vertebral frame  200 , the anterior surface of the retention member having a contour  401  which generally matches that of the vertebral frame  200  to create a smooth, continuous surface after installation. 
         [0096]      FIG. 6  further shows the retention member having extensions  420  that cover the bone screws and thereby preventing screw back-out. 
         [0097]      FIG. 7  depicts the vertebral frame in position on adjacent vertebrae and illustrates the operating window in the region of the disk space. The operating window is defined by the cross members  503 ,  504 ,  505  and  506  respectively which produce a contained area through which all procedures may be executed. Further, these members act to restrain the surgeon during tissue excision and thereby minimize the risk of accidental damage to surrounding tissue. 
         [0098]      FIG. 7  further illustrates how the device provides access to facilitate the removal of disk material  502  and the preparation of the intervertebral space  501  prior to the insertion of the interbody implant. 
         [0099]      FIG. 8  is a perspective side view of the vertebral frame in the installed position on adjacent vertebrae. The device has clearance spaces  601  in the region of the disk material to accommodate a better fit to the vertebral surfaces and to provide additional clearance to allow for the removal of unwanted bone material after device installation. 
         [0100]      FIGS. 9 and 10  depict the retention member  300  placed in-situ on the vertebral frame  200  after the insertion of the interbody implant. The member  300  is located so as to prevent substantial movement of the interbody implant and thereby promote bone tissue growth therein. 
         [0101]    Instead of screws, or in combination therewith, one or more snap lock devices may be used to attach retention member  300  to vertebral frame  200 . Such devices may employ a compressible feature, such as a split barb, that locks into place when inserted sufficiently into hole  105  or other mating feature. By using snap lock device(s), member  300  can be simply aligned with frame  200  and pressed into place without requiring the surgeon to align screws and install them with a driver. One or more cam lock devices may also be used, alone or with screws and/or snap lock devices. In some cam lock embodiments a torsional force is applied to a component, inducing rotation and causing it to become engaged in a corresponding feature within a receiving element. This twisting action causes the component to turn and lock under another component, again with less effort than required when installing a screw. 
         [0102]    The system offers substantial benefits over those previously disclosed and those currently employed. These benefits include, but are not limited to: 
         [0103]    1) A novel method which allows for precise control and fixation of optimal vertebral position. 
         [0104]    2) Constrained and controlled tissue removal 
         [0105]    3) Elimination of patient to patient variation 
         [0106]    4) Integration of soft tissue retraction devices 
         [0107]    5) Reduction in surgical time and maneuvers throughout the case. 
         [0108]    Referring to  FIGS. 11-16  another exemplary embodiment of an implantable vertebral frame system and method of use will be described.  FIGS. 11A-11F  show the vertebral frame itself and the associated screws of this embodiment. Frame  700  is similar in construction and method of use to previously described frame  100 . In this embodiment, frame  700  is curved in the mediolateral direction (as best seen in  FIG. 11E ) and generally straight in the craniocaudal direction (as best seen in  FIG. 11D ) to match the anterior surfaces of adjacent vertebrae to which frame  700  will be affixed. In other embodiments, the frame may also be curved in the craniocaudal direction. In some embodiments it is desirable to have the radius or radii of curvature as small or smaller than the associated radii of the adjacent vertebrae to ensure that the frame does not wobble when mounted on the vertebrae. In some embodiments, frame  700  has a radius of curvature of about 25 mm, an overall length of about 25 mm, an overall width of about 19 mm, and a plate thickness of about 2.5 mm. It is 
         [0109]    Frame  700  includes four bone screw holes  702  extending through frame  700  from its anterior face  704  to its posterior face  706 . As best seen in  FIG. 11A , the anterior side of each hole  702  may be provided with a spherically curved countersink  708 . Spherical countersink  708  mates with a complementary shaped spherical shoulder  710  on bone screw  712 , as shown in  FIG. 11F . Countersink  708  and shoulder  710  cooperate to allow bone screw  712  to be inserted through screw hole  702  in a wide range of mediolateral and craniocaudal angles while still allowing the head  714  of screw  712  to remain firmly seated against frame  700  when installed to prevent movement of frame  700 . As best seen in  FIG. 11D , bone screw holes  702  and countersinks  708  can be configured to provide nominal screw angles such that screws  712  angle away from each other in the craniocaudal direction. As best seen in  FIG. 11E , bone screw holes  702  and countersinks  708  can be configured to provide nominal screw angles such that screws  712  angle towards each other in the mediolateral direction. While the spherical countersinks  708  allow the surgeon to vary the screw angle from nominal as previously described, these nominal compound screw angles allow frame  700  to withstand greater extraction forces in the anterior direction than if each screw were perpendicular to frame  700 , thereby allowing frame  700  to be affixed to the adjacent vertebral bodies more rigidly. 
         [0110]    Referring to  FIGS. 11A and 11B , frame  700  also includes an operating aperture  716  through its midsection, the purpose of which will be later described. In this exemplary embodiment, operating aperture  716  has a height of about 10.5 mm and a width of about 15 mm. Coplanar reference surfaces  718  may also be provided, such as along the longitudinal centerline of frame  700  on opposite sides of operating aperture  716  as shown. Surfaces  718  may be held to high tolerances to provide accurate datum points for surgical tools and a cover plate that will be later described. Slotted through holes  720  or similar features may be provided on opposite sides of operating aperture  716  to allow frame  700  to be placed over distractor pins located in adjacent vertebrae. Slotted holes  720  may also serve as additional datum points. In this exemplary embodiment, all other critical features of frame  700  are formed in reference to surfaces  718 , holes  720 , and the edges of operating aperture  716  adjacent to surfaces  718 . Frame  700  may be provided with indents  722  along the longitudinal centerline of frame  700  to aid the surgeon in placing frame  700  on the centers of adjacent vertebral bodies. 
         [0111]    Referring to FIGS.  11 A and  11 C- 11 E, recesses  724  may be provided in each corner of frame  700  as shown for anchoring mating prongs of soft tissue retractors, as will be subsequently described in more detail. As shown in  FIG. 11C , an anteriorly extending pocket  726  may be formed in the generally posteriorly facing surface of each recess  724  to more positively engage the mating prongs of the retractors. 
         [0112]    Referring to  FIGS. 11A and 11C , two pairs of opposing undercuts  728  and  730  are shown on the posterior face  706 . The first pair of undercuts  728  are on mediolaterally opposite sides of operating aperture  716  and each have a posteriorly facing surface located between the anterior face  704  and posterior face  706  of frame  700 . These undercuts  728  serve to receive snap-fit protrusions of a cover plate to temporarily hold it in place, as will be subsequently described in more detail. The second pair of undercuts  730  are on craniocaudally opposite sides of operating aperture  716  and also each have a posteriorly facing surface located between the anterior face  704  and posterior face  706  of frame  700 . These undercuts  730  serve to receive the distal ends of a rotatable locking arm of the cover plate to permanently hold the cover plate in place, as will also be subsequently described in more detail. 
         [0113]    Referring to  FIG. 11F , a proprietary bone screw  712  may be used with the inventive frame  700 . Screw  712  includes a head  714  and a threaded shank  732 . Threaded shank  732  may be configured to be self drilling and/or self tapping. As previously described, screw  712  also includes a shoulder portion  710 . Screw  712  may be provided with head relief portion  734  to cooperate with a screw locking portion of a cover plate, as will be subsequently described in detail. 
         [0114]    As shown in  FIGS. 11A-11E , the vertebral frame  700  in this embodiment is completely symmetrical about the longitudinal and transverse centerlines. This allows the surgeon to install the plate on the vertebrae without having to first determine a proper craniocaudal orientation. 
         [0115]    Referring to  FIGS. 12A-12G , an exemplary cover plate  750  configured to interface with vertebral frame  700  is shown. In this exemplary embodiment, cover plate  750  serves to prevent an intervertebral implant from moving anteriorly, and prevents screws  712  from backing out of the vertebral bodies. 
         [0116]    Cover plate  750  may be curved in mediolateral direction, as best seen in  FIG. 12F , to generally match the curvature of frame  700 . In this exemplary embodiment, cover plate has an anterior side  751  and a posterior side  753 . Cover plate  750  may include a pair of opposing mediolateral wings  752  and a pair of opposing craniocaudal wings  754 . When cover plate  750  is installed on frame  700 , the central portion of cover plate  750  and the mediolateral wings  752  are received within the operating aperture  716  of frame  700  and serve to cover aperture  716 . Mediolateral wings  752  each comprise a laterally extending arm  756  with a tongue  758  located at its distal posterior edge. Each tongue  758  is engagable with one of the previously described opposing undercuts  728  of frame  700 . This arrangement allows a surgeon to snap cover plate  750  in place and have it temporarily held in place by tongues  758  locking into undercuts  728 . In this embodiment, arms  756  have some resiliency, allowing them to flex as tongues  758  begin entering operating aperture  716  and before entering undercuts  728 . Craniocaudal wings  754  cover reference surfaces  718  of frame  700  when installed. Additionally, distal portions  760  of craniocaudal wings cover a portion of screw heads  714 , as will be subsequently described in more detail. As best seen in  FIG. 12C , distal portions  760  include undercuts  762  for engaging head relief portions  734  of screws  712 . 
         [0117]    Referring to  FIG. 12G , a locking arm  764  configured for permanent assembly with cover plate  750  is shown. Locking arm  764  may be a unitary member that snaps into a central bore of cover plate  750 , or may comprise a separate arm that is swaged, press fit or otherwise fixedly secured to locking socket  766  before or during assembly with cover plate  750 . Once assembled, locking arm  764  is rotably retained on cover plate  750  with locking socket  766  accessible from the anterior side  768  of cover plate  750 , as shown in  FIGS. 12A and 12B . Locking arm  764 , which is driven by locking socket  766 , is located on the posterior side  770  of cover plate  750 , and is rotatable between a locked position, as shown in  FIG. 12C , and an unlocked position, as shown in  FIG. 16S . When in the locked position, the distal ends of locking arm  764  are received within the second pair of undercuts  730  on opposite ends of operating aperture  716  in frame  700 , shown in  FIG. 11A . In this position, cover plate  750  is securely locked to frame  700  since reference surfaces  718  ( FIG. 11A ) are captured between locking arm  764  and the craniocaudal wings  754  of cover plate  750  ( FIG. 12C ). In other embodiments (not shown), the locking arm engages the frame on opposite mediolateral sides instead of craniocaudal sides. 
         [0118]    Locking arm  764  may include a raised dimple  768 , as shown in  FIG. 12G , that extends from the locking arm towards the underside of cover plate  750 . Cover plate  750  may be provided with a through-hole  770 , as shown in  FIG. 12D , for receiving the raised dimple  768  when locking arm  764  is in the locked position. Cover plate  750  may also be provided with a ramped recess  772  adjacent to hole  770 . Recess  772  becomes deeper as it extends away from hole  770 . This arrangement biases locking arm  764  toward the unlocked position as dimple  768  is urged toward the bottom of the ramp at the opposite end of recess  772  from hole  770 . This arrangement also provides better tactile feedback to the surgeon, who feels increasing resistance when turning locking socket  766 , until dimple  768  snaps into hole  770 . Dimple  768  and/or locking arm  764  may have a different color that contrasts with cover plate  750  to provide visual feedback through hole  770  when locking arm  764  is in the fully locked position. Dimple  768  and arm  764  may be configured to click when entering hole  770 . Accordingly, the surgeon may be provided with tactile, visual and audible confirmation when arm  764  is in the fully locked position. 
         [0119]    Through hole  774  may be provided in locking arm  764 , as shown in  FIG. 12G , to align with blind hole  776  in cover plate  750 , as shown in  FIG. 12D , when locking arm  764  is in the unlocked position. Holes  774  and  776  may be used in conjunction with assembly tooling (not shown) when cover plate  750  is being manufactured. Raised portions  778  may be provided on the posterior side of cover plate  750 , as shown in  FIGS. 12C and 12D , to limit the travel of locking arm  764 . In some embodiments, the travel of arm  764  between the unlocked and locked positions is about 45 degrees. 
         [0120]    Cover plate  750  may be made of PEEK so as to be radiolucent. This allows bone growth into an implant beneath cover plate  750  (as will be subsequently described) to be viewed with various imaging techniques. Locking arm  764  may be made of titanium so its locked status can be confirmed by imaging. 
         [0121]    Referring to  FIGS. 13A-13G , an exemplary instrument guide  800  configured for use with vertebral frame  700  is shown. Instrument guide  800  has a proximal end  802  and a distal end  804 . A handle  806  may be provided for holding guide  800  in place during a surgical procedure. In some embodiments, a removable divider or insert  808  is configured to be received within guide  800 . 
         [0122]    As best seen in  FIG. 13E , instrument guide  800  includes a tri-lobe lumen  810  extending therethrough from the proximal end  802  to the distal end  804 . Lumen  810  includes a central bore  812  overlapping two lateral bores  814 . 
         [0123]    The distal end  804  of guide  800  is configured to mate with the anterior side  704  of vertebral frame  700 . As best seen in  FIGS. 13A and 13G , distal end  804  may be curved in the mediolateral direction to match the curvature of frame  700 . As best seen in  FIGS. 13C and 13D , the body (and therefore lumen  810 ) of guide  800  may be angled in the caudal direction relative to the distal end  804 . In some embodiments, this angle is about 3 degrees to correspond with the angle of the interverbral space relative to the anterior surface of vertebral bodies in the cervical spine. When guide  800  is coupled to frame  700 , lumen  810  of guide  800  lines up with operating aperture  716  of frame  700 . 
         [0124]    Referring to  FIGS. 13E-13G , features of the distal end  804  of guide  800  are shown. Registration surfaces  815  are provided on guide  800  for contacting reference surfaces  718  of frame  700 , shown in  FIGS. 11A and 11B . Bosses  816  may be provided on registration surfaces  815  as shown for engaging holes  720  in reference surfaces  718 . The above features cooperate to accurately align features on guide  800  that may be critical, such a lumen  810  and proximal surface  802 , with features on frame  700  and underlying anatomical features. 
         [0125]    Insert  808  has rounded sides corresponding with central bore  812 , as best seen in  FIG. 13B . When optional insert  808  in temporarily placed in central bore  812  in this exemplary embodiment, the tri-lobe lumen of guide  800  is converted into two individual lateral bores  814  as shown. Insert  808  may be provided with a handle  818 . In this embodiment, handle  818  includes an elongated rib  820  which is received in slot  822  in the guide body, as shown in  FIG. 13A . This arrangement allows insert  808  to be keyed with guide  800  in only one orientation. Insert handle  818  may also be provided with a direction indicator, such as an arrow pointing to the patient&#39;s feet and corresponding indicia, as shown in  FIG. 13B . 
         [0126]    Referring to  FIGS. 14A-14C , an exemplary soft tissue retractor  830  constructed according to aspects of the invention is shown. One or more retractors  830  may be used in conjunction with intervertebral frame  700  after it is installed on one or more vertebrae to retract soft tissue away from frame  700  during a surgical procedure. Retractor  830  includes a blade  832 . The distal end of blade  832  may be provided with a fulcrum  834  for contacting vertebral body  836 , and a pair of tongues  838  for engaging with previously described recesses  724  in frame  700 . The distal ends of tongues  838  may be provided with protrusions  840  projecting in the anterior direction for engaging with previously described pockets  726  in recesses  724 . As shown in  FIG. 14A , the distal end of blade  832  may be placed adjacent to frame  700 , and then tongues  838  may be inserted into recesses  724  as shown in  FIG. 14B . The proximal end of blade  832  may be provided with a feature, such as hole  842  in flange  844 , for attaching a handle or spreading device (not shown) to urge the proximal end of blade  832  in a lateral direction against soft tissue adjacent to frame  700 . A single spreading device may be attached between a pair of opposing retractors  830  (only one shown for clarity) to keep them spread apart. Blade(s)  830  may be curved, as shown in  FIG. 14C , and/or may be provided with a longitudinal rib  846 , as shown in  FIGS. 14A and 14B , for increased rigidity. 
         [0127]    Referring to  FIGS. 15A-15C , an exemplary interbody repair implant  850  constructed according to aspects of the invention is shown. In this embodiment, implant  850  has an elongated tri-lobe shape which includes a central cylindrical portion  852  and two lateral cylindrical portions  854  which overlap with the central portion  852 . Cylindrical portions  852  and  854  correspond with central bore  812  and overlapping lateral bores  814 , respectively, of instrument guide  800 . Implant  850  may be provided with one or more graft windows  856  for receiving cages containing bone material and/or for promoting bony ingrowth between the vertebrae and implant  850 . One or both ends of implant  850  may be provided with a central hole  858  and two lateral holes  860 , or other suitable features, for engaging implant insertion instrumentation. In this exemplary embodiment, central hole  858  is threaded and lateral holes  860  are configured for sliding engagement with features on the instrumentation. One or more radio markers  862  may be provided on implant  850 , such as shown in the four corners of the implant in  FIGS. 15B and 15C . Radio markers  862  may comprise titanium, tantalum or other biocompatible, radio-opaque material(s) to assist in determining the position of implant  850  in imaging. 
         [0128]    In some embodiments, the tri-lobe configuration of implant  850  helps resist undesirable axial rotation between axial vertebrae. In some embodiments this configuration minimizes the tissue that is removed from the adjacent vertebrae as compared with a rectangular or other shape implant. In some embodiments surgeons are provided with implants that are either 11 mm or 15 mm long, and 15 mm or 18 mm wide. 
         [0129]    In some embodiments implant  850  is made of PEEK. Since PEEK is radiolucent, bony ingrowth into the implant may be monitored with imaging during the healing process. In other embodiments, the implant comprises titanium and/or stainless steel. 
         [0130]    Referring to  FIGS. 16A-16B , an exemplary intervertebral distraction device  870  constructed according to aspects of the invention is shown. Distraction device  870  includes a wedge portion  872  and a head portion  874 . In this embodiment, wedge portion  872  includes a first pair of non-parallel surfaces  876 ,  878 , and a second pair of non-parallel surfaces  880 ,  882 . First surfaces  876  and  878  serve as lead-in surfaces when distraction device  870  is being introduced between the endplates of adjacent vertebral bodies. Second surfaces  880  and  882  serve to orient the vertebral endplates at a predetermined distraction distance h and lordosis angle α. 
         [0131]    Head portion  874  of distracton device  870  may have a height H in a craniocaudal direction larger than the height h of wedge portion  872  in the same craniocaudal direction, as shown in  FIG. 16C . This prevents head portion  874  from entering the intervertebral space between the adjacent vertebrae. In other words, shoulders  884  serve as a depth stop by contacting the anterior surfaces of the vertebrae, as will be subsequently described in more detail. In some embodiments, the surgical team may be provided with a kit comprising distraction devices each having the same head height H and different wedge portion heights h, such as 4, 5, 6, 7, and 8 mm. As can also be seen in  FIG. 16C , wedge portion  872  has a predetermined length L, which in some embodiments is 10 mm. Wedge portion  872  has a longitudinal axis that in some embodiments is not perpendicular to shoulders  884 . In this exemplary embodiment, the angle of offset between wedge portion  872  and head portion  874  matches the previously described angle of the body (and therefore lumen  810 ) of guide  800  relative to the distal end  804 . In some embodiments, this angle is about 3 degrees to correspond with the angle of the interverbral space relative to the anterior surface of vertebral bodies in the cervical spine. 
         [0132]    Head portion  874  of distracton device  870  may be provided with a central hole  858  and two lateral holes  860 , or other suitable features, for engaging implant insertion instrumentation as previously described in relation to interbody repair implant  850 . 
         [0133]    Referring to  FIGS. 17A-17X , an exemplary spinal fusion surgical procedure using the previously described components is depicted according to aspects of the invention. 
         [0134]      FIG. 17A  shows an exemplary distraction device  870  temporarily attached to an insertion instrument  900  and about to be inserted between adjacent vertebrae  836 ,  836 . Insertion instrument  900  may include a separate shaft portion  902  removably attached to a handle  904 , such as a handle having a standard “AO” interface. 
         [0135]      FIG. 17B  shows distraction device  870  inserted between adjacent vertebrae  836 ,  836  as the insertion instrument is being removed. 
         [0136]      FIG. 17C  shows a cross-section of distraction device  870  inserted between adjacent vertebrae  836 ,  836  after the insertion instrument has been removed. 
         [0137]      FIG. 17D  shows intervertebral frame  700  placed on adjacent vertebrae  836 ,  836  over distraction device  870 . Operating aperture  716  through frame  700  can be configured with a craniocaudal height just nominally larger than the craniocaudal height of head  874  of distraction device  870 . This arrangement allows a surgeon to properly center frame  700  over the intervertebral space  906  between adjacent vertebrae  836 ,  836  merely by placing frame  700  over head  874 . As previously described, indents  722  at the top and bottom of frame  700  can provide assistance to the surgeon when centering frame  700  in the mediolateral direction. 
         [0138]      FIG. 17E  shows a drill guide  908  placed over one of the screw holes  702  in frame  700  for guiding optional drill  910  to create holes in vertebrae  836  for receiving bone screws. A reamer, tap and/or other bone cutting instruments may also be optionally used to prepare screw holes. In some embodiments, self drilling and/or self-tapping screws may be used. The screws may be installed by hand or with a screw guide similar to drill guide  908 . The screws may be fixed angle and/or variable angle. In some embodiments, the screws have an aggressive thread. In some embodiments a 4.0 mm standard size screw is used. In some embodiments a 4.5 mm recovery screw is used. 
         [0139]      FIG. 17F  shows frame  700  secured to adjacent vertebrae  836 ,  836  with four screws  712 . 
         [0140]      FIG. 17G  shows frame  700  secured to adjacent vertebrae  836 ,  836  after distraction device  870  has been removed. Distraction and lordotic angle is now permanently set and locked in place by frame  700 . 
         [0141]      FIG. 17H  shows frame  700  secured to adjacent vertebrae  836 ,  836  with retractor  830  attached and instrument guide  800  being lowered into position on top of frame  700 . 
         [0142]      FIG. 17I  shows instrument guide  800  in position on top of frame  700  and a large drill  912  being inserted into central bore  812  of guide  800  to begin preparing the intervertebral space between vertebrae  836 ,  836  by removing the disc and/or end plate material. A drill, trephine, reamer, other bone cutting tool, or a combination thereof may be used to prepare the intervertebral space. Standard sizes of 6, 7, 8 or 9 mm can all be produced using the same instrument guide. In some embodiments a custom cutter is used with cutting sides and face. In some embodiments, the natural bone material being removed is collected from the cutting tool(s) and packed into the interbody implant before it is implanted in the patient. 
         [0143]      FIG. 17J  shows instrument guide  800  in position on top of frame  700  and guide insert  808  being inserted into central bore  812  of guide  800 . 
         [0144]      FIG. 17K  shows instrument guide  800  in position on top of frame  700  and guide insert  808  fully inserted into central bore  812  of guide  800 . 
         [0145]      FIG. 17L  shows instrument guide  800  in position on top of frame  700  and a small drill  914  being inserted into one of the lateral bores  814  of guide  800  to further prepare the intervertebral space between vertebrae  836 ,  836 . As with the central bore, a drill, trephine, reamer, other bone cutting tool, or a combination thereof may be used in the lateral bores, and the harvested bone tissue may be packed into the implant. In some embodiments, the lateral bores are prepared without the use of an insert  808 , and/or the lateral bores may be prepared before or after the central bore. 
         [0146]      FIG. 17M  shows frame  700  secured to adjacent vertebrae  836 ,  836  with the intervertebral space  906  prepared for receiving a tri-lobe intervertebral implant. 
         [0147]      FIG. 17N  depicts the nominal diameters (in millimeters) of the central and lateral bores for preparing the intervertebral space in various exemplary embodiments. In some embodiments, a variety of implant and guide configurations are made available to the surgical team in a single kit. Each configuration may have the same overall width. In other words, the distance between the outer circumferences of the lateral bores remains fixed across multiple configurations rather than the distance between the centers of the axial bores. Lobe sizes may be surgeon selected based on physiology and disk condition. Standard kerrisons and curettes may be used through the channel. 
         [0148]    In some embodiments, the intervertebral space  906  is configured to be nominally smaller than the associated interbody implant, requiring the implant to compressively engage the vertebrae endplates when implanted. This arrangement can provide immediate structural stability of the repaired spine segment and can promote boney ingrowth into the implant. 
         [0149]      FIG. 17O  shows an interbody implant  850  attached to an insertion tool  900  and being inserted through the operating aperture  716  of frame  700  into the prepared intervertebral space. Insertion stops may be provided on the implant and/or insertion tool to limit the depth of insertion of the implant. 
         [0150]      FIG. 17P  shows a craniocaudal cross section of interbody implant  850  in place in the prepared intervertebral space. 
         [0151]      FIG. 17Q  shows a mediolateral cross section of interbody implant  850  in place in the prepared intervertebral space. 
         [0152]      FIG. 17R  shows cover plate  750  in position over frame  700 . 
         [0153]      FIG. 17S  depicts locking arm  764  of cover plate  750  in the unlocked position and moving towards the locked position. 
         [0154]      FIG. 17T  depicts locking arm  764  of cover plate  750  in the locked position. 
         [0155]      FIG. 17U  shows an oblique posterior view of a craniocaudal cross-section of cover plate  750  coupled to frame  700  with locking arm  764  in the locked position. 
         [0156]      FIG. 17V  shows an oblique anterior view of a craniocaudal cross-section of cover plate  750  coupled to frame  700  mounted on adjacent vertebrae  736 ,  736 , with locking arm  764  in the locked position. 
         [0157]      FIG. 17W  shows an oblique mediolateral cross-sectional view of a coverplate  750  coupled to frame  700  and covering a portion of screw heads  714 . 
         [0158]      FIG. 17X  shows a mediolateral cross-sectional end view of a coverplate  750  coupled to frame  700  and covering a portion of screw heads  714 . 
         [0159]    In some embodiments, not every step shown in  FIGS. 17A-17X  is performed. In some embodiments, additional and/or alternative steps may be performed. 
         [0160]    In summary, an exemplary trans-plate cervical decompression and fusion procedure may include at least the following steps: 
         [0161]    Anterior incision 
         [0162]    Retraction 
         [0163]    Distraction and pre-lordosing 
         [0164]    Vertebral frame installation over the distraction device 
         [0165]    Removal of distraction device 
         [0166]    Discectomy and end plate preparation through the frame 
         [0167]    Decompression 
         [0168]    Implant insertion 
         [0169]    Cover implant and lock 
         [0170]    Close incision 
         [0171]    All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.