Anterior cervical plating system and method

Abstract

The present invention is directed to a system for anterior fixation of the spine that utilizes an elongated fixation plate. The plating system stabilizes the spine and promotes fusion and incorporation of a graft or implant in a portion of the spinal column. In one aspect of the invention, the fixation plate has a first end with a pair of holes. Bone screws extend through the holes to rigidly secure the plate to a first vertebra. The second end of the plate is provided with a pair of slots through which bone screws extend for engagement with a second vertebra. The screws extending through the slots are translatable in the slot to maintain compression of the spinal column portion. The plating system includes a retainer assembly that prevents screw back out. Methods and instruments relating to the plating system are also described.

What is claimed is:  
     
         1 . A bone fixation system for a portion of the spinal column, comprising: 
 a plate having a length along a central axis extending longitudinally between a first end and a second end, and a top surface and a bottom surface along said length, and said plate having a plurality of first openings and a plurality of second openings between said surfaces, wherein: 
 at least one of said plurality of first openings is positioned adjacent said first end, said one first opening defining a circular hole having a first diameter adjacent said bottom surface;  
 at least one of said plurality of second openings is positioned adjacent said second end, said one second opening defining a slot having a first width and a first length adjacent said bottom surface;  
   bone engaging fasteners extending through said first and second openings, each bone engaging fastener having an elongated shank defining bone engaging threads thereon and an enlarged head, said shank having a substantially cylindrical portion with a third diameter less than said first diameter so said bone engaging fastener can be inserted through said one first opening and said cylindrical portion contacts said plate in said one first opening so that said bone engaging fastener assumes a fixed orientation relative to said plate, said cylindrical portion third diameter also less than said second width so said bone engaging fastener can be inserted through said one second opening from said top surface of said plate and said head of said bone engaging fastener is translatable along the length of said at least one second opening to maintain compression of the spinal column portion.    
     
     
         2 . The bone fixation system of  claim 1 , wherein said second openings include a ramp that guides said bone engaging fastener as it is inserted into said one second opening to provide a dynamic compression load to the spinal column portion.  
     
     
         3 . The bone fixation system of  claim 1 , whereby each of said at least one first and second openings define a recess adjacent said top surface and said enlarged head defines a partially spherical surface complementary to said recess of said at least one first and second openings.  
     
     
         4 . The bone fixation system of  claim 3 , wherein said head of said fastener includes a truncated top surface.  
     
     
         5 . The bone fixation system of  claim 3 , further comprising a retainer assembly for retaining said heads of said number of bone engaging fasteners within said at least one first opening and said at least one second opening.  
     
     
         6 . The bone fixation system of  claim 5 , wherein said retainer assembly includes: 
 a first fastener bore defined in said plate adjacent said at least one first opening and a second fastener bore defined in said plate adjacent said at least one second opening;    a washer having at least a first aperture adjacent said at least one first opening and a second aperture adjacent said at least one second opening and a countersink portion communicating with each of said apertures, said washer further having a body with portions overlapping said at least one first and second opening when said washer is in a first position relative to said at least one first and second openings, said body portions being arranged so that bone engaging fasteners can be inserted through said at least one first opening and said at least one second opening when said washer is in a second position relative to said at least one first and second openings; and    a locking fastener for each of said apertures having a head configured to be at least partially recessed within said countersink portion of said washer and having an elongated shank extending through said aperture and configured to engage said fastener bore of said plate.    
     
     
         7 . The bone fixation system of  claim 6 , wherein said plate further defines a groove in said top surface extending longitudinally along said plate, said groove being overlapping said at least one first and second openings, said first and second fastener bores being positioned within said groove.  
     
     
         8 . The bone fixation system of  claim 5 , wherein said retainer assembly includes a washer having a contact surface for contacting said head of said bone engaging fastener in said one first opening and an outer surface for overlapping said heads of said bone engaging fasteners in said one second opening.  
     
     
         9 . The bone fixation system of  claim 1 , further comprising a retainer assembly including: 
 a first fastener bore defined in said plate adjacent said at least one first opening and a second fastener bore defined in said plate adjacent said at least one second opening;    a washer having at least a first aperture adjacent said at least one first opening and a second aperture adjacent said at least one second opening and a countersink communicating with each of said apertures, said washer further having a surface configured to contact said head of said bone engaging fastener extending through said at least one first opening; and    a locking fastener for each of said apertures having a head configured to be at least partially recessed within said countersink portion of said washer and an elongated shank extending through said aperture configured to engage said fastener bore of said plate.    
     
     
         10 . The bone fixation system of  claim 9 , wherein said washer has an outer surface that overlaps said head of said bone engaging fastener extending through said at least one second hole without contacting said head.  
     
     
         11 . The bone fixation system of  claim 9 , wherein said plate further defines a groove in said top surface extending longitudinally along said plate, said groove overlapping said at least one first and second openings, said first and second fastener bores being positioned within said groove.  
     
     
         12 . The bone fixation system of  claim 1 , wherein said elongated plated defines a plurality of vertebral nodes at longitudinally spaced location along the plate.  
     
     
         13 . The bone fixation system of  claim 12 , wherein there are provided a pair of said first openings at one said vertebral nodes adjacent said first end of said plate and a pair of said second openings at one of said vertebral nodes adjacent said second end of said plate.  
     
     
         14 . The bone fixation system of  claim 13 , wherein said openings of said pair of first openings are symmetrically positioned about said central axis and said openings of said pair of second openings are symmetrically positioned about said central axis.  
     
     
         15 . A bone fixation system for a portion of the spinal column, comprising: 
 a plate having a length along a central axis extending longitudinally between a first end and a second end, a top surface and a bottom surface along said length, said plate further defining a plurality of first openings and a plurality of second openings between said surfaces, wherein: 
 at least two of said first openings are circular, having a first diameter, and are positioned adjacent said first end;  
 at least two of said second openings are slotted, having a first width and a first length, and are positioned adjacent said second end of said plate;  
   bone engaging fasteners extending through said first and second openings, each bone engaging fastener having an elongated shank having bone engaging threads thereon and an enlarged head, said bone engaging fasteners configured for insertion into said first and second openings from said top surface; and    means retaining said heads of said bone engaging fasteners in said first and second openings, said retaining means translatable from a first position allowing bone engaging fastener insertion into said first and second openings to a second position retaining said bone engaging fasteners in said first and second openings.    
     
     
         16 . The bone fixation system of  claim 15 , wherein said two first openings have a recess portion adjacent said top surface and said two second openings have a recess portion adjacent said top surface.  
     
     
         17 . The bone fixation system of  claim 16 , wherein said heads of said bone engaging fasteners are configured to be at least partially recessed in said two first and second openings.  
     
     
         18 . The bone fixation system of  claim 15 , wherein said two first and second openings each include a recess adjacent said top surface and said enlarged head has a partially spherical surface complementary to said recess of said two first and second openings.  
     
     
         19 . The bone fixation system of  claim 18 , wherein said plate further defines a groove in said top surface extending longitudinally along said plate for receiving said retaining means therein, said groove overlapping said recesses.  
     
     
         20 . The bone fixation system of  claim 15 , wherein said head of said bone engaging fastener has an inclined surface and said retaining means has a contact surface to contact said inclined surface of said bone engaging fasteners extending through said two first openings.  
     
     
         21 . The bone fixation system of  claim 15 , wherein retaining means includes: 
 a first fastener bore defined in said plate adjacent said two first openings and a second fastener bore defined in said plate adjacent said two second openings;    a washer having a body defining at least a first aperture adjacent said two first openings and a second aperture adjacent said two second openings and a countersink portion communicating with each of said apertures, said washer further having a contact surface configured to contact said head of said bone engaging fastener extending through said two first openings; and    a locking fastener for each of said apertures having a head configured to be at least partially recessed within said countersink portion of said washer and an elongated shank extending through said aperture and configured to engage said fastener bore of said plate.    
     
     
         22 . The bone fixation system of  claim 21 , wherein said apertures of said washer each form a slot having a length extending longitudinally with the plate.  
     
     
         23 . The bone fixation system of  claim 22 , wherein at least one of said aperture countersink portion is tapered along said length of said slot and has a width that increases along said length of said aperture from said second end towards said first end.  
     
     
         24 . The bone fixation system of  claim 22 , wherein said at least one aperture is positioned adjacent said two second openings.  
     
     
         25 . The bone fixation system of  claim 15 , wherein said retaining means includes: 
 a first fastener bore defined in said plate adjacent said two first openings and a second fastener bore defined in said plate adjacent said two second openings;    a washer having at least a first aperture adjacent said two first openings and a second aperture adjacent said two second openings and a countersink portion communicating with each of said apertures, said washer further having a body with portions overlapping said two first openings and said two second openings when said washer is in a first position relative to said two first and second openings, said body portions being arranged so that bone engaging fasteners can be extended through said two first openings and said two second openings when said washer is in a second position relative to said two first and second openings; and    a locking fastener for each of said apertures having a head configured to be at least partially recessed within said tapered portion of said washer and an elongated shank extending through said aperture and configured to engage said fastener bore of said plate.    
     
     
         26 . The bone fixation system of  claim 25 , wherein said apertures of said washer form slots having a length extending in the direction of the length of the plate.  
     
     
         27 . The bone fixation system of  claim 26 , where said countersink communicating with each of said apertures has a width that increases along the length of said aperture in a direction from said second end towards said first end.  
     
     
         28 . A bone fixation system for a portion of the spinal column, comprising: 
 four bone engaging fasteners, each having an enlarged head and a threaded shank; and    an elongated plate having a length extending between a first end and a second end and sized to span between at least two vertebrae, said plate defining a one pair of adjacent holes adjacent said first end and one pair of adjacent slots adjacent said second, each of said holes and said slots configured to receive said threaded shank of a corresponding one of said bone engaging fasteners therethrough,    wherein said bone engaging fasteners extending through said pair of holes fix said plate to said first vertebra and said bone engaging fasteners extend through said slots to secure said plate to said second vertebra, and said bone engaging fasteners received in said slots are enabled to translate in said slots in a direction of the length of the plate to maintain compression on the spinal column portion.    
     
     
         29 . The bone fixation system of  claim 28 , wherein said plate has a top surface and a bottom surface and said holes and said slots each further include a recess adjacent said top surface.  
     
     
         30 . The bone fixation system of  claim 28 , further including a retainer assembly having a washer configured to overlap each of said holes and slots and retain said bone engaging fasteners extending through said holes and slots.  
     
     
         31 . The bone fixation system of  claim 30 , wherein said head of each of said bone engaging fasteners has an inclined surface and said washer has a contact surface configured to contact said inclined surface of said bone engaging fasteners extending through said pair of holes.  
     
     
         32 . The bone fixation system of  claim 30 , wherein said plate includes a first fastener bore defined in said plate between said pair of holes and a second fastener bore defined in said plate between said pair of slots, and said retainer assembly further includes: 
 said washer has at least a first aperture adjacent said holes and a second aperture adjacent said slots and a countersink portion communicating with each of said apertures; and    a locking fastener for each of said apertures, said locking fastener having a head configured to be recessed within said recess of said washer and an elongated shank extending through said aperture and configured to engage said fastener bore of said plate.    
     
     
         33 . The bone fixation system of  claim 32 , wherein said elongated shank of said locking fastener terminates in a sharp point for penetrating a vertebral body.  
     
     
         34 . The bone fixation system of  claim 33 , wherein said head of said locking fastener defines a lower conical surface for contacting said washer.  
     
     
         35 . A bone fixation system for a portion of a spinal column, comprising: 
 six bone engaging fasteners, each having an enlarged head and a threaded shank; and    an elongated plate having a length extending between a first end and a second end and sized to span between at least three vertebrae, said plate defining one pair of holes over a first vertebra, one pair of intermediate slots over a second vertebra, and one pair of slots over a third vertebra, each of said holes and said slots configured to receive said threaded shank of a corresponding one of said bone engaging fasteners therethrough,    wherein said bone engaging fasteners extending through said pair of holes fix said plate to said first vertebra and said bone engaging fasteners extend through said slots to secure said plate to said second vertebra, and said bone engaging fasteners received in said slots are enabled to translate in said slots in a direction of the length of the plate to maintain compression on the spinal column portion.    
     
     
         36 . The bone fixation system of  claim 35 , further including a retainer assembly having a washer configured to overlap each of said holes and slots and retain said bone engaging fastener extending through said holes and slots in said plate.  
     
     
         37 . A fastener retainer assembly for an elongated plate having a length extending between at least two vertebrae, the plate defining a number of openings therethrough for insertion of bone engaging fasteners to attach the plate to the at least two vertebrae, said retainer assembly comprising: 
 a first fastener bore defined in said plate adjacent at least one of the openings positioned over the first vertebra and a second fastener bore defined in said plate adjacent at least one the openings positioned over the second vertebra;    a washer defining at least a first aperture adjacent said at least one opening positioned over the first vertebra and a second aperture adjacent said at least one opening positioned over the second vertebra, said washer configured to retain said bone engaging fasteners extending through said openings in said plate; and    a locking fastener for each of said apertures, said locking fastener having an elongated shank extending through said aperture and configured to engage said fastener bore of said plate, said openings in said plate being positioned and configured wherein said washer is movable between a first position enabling insertion of said bone engaging fasteners into said at least one openings and a second position wherein said washer retains said inserted bone engaging fasteners in said plate.    
     
     
         38 . The retainer assembly of  claim 37 , wherein said apertures of said washer form slots having a length extending in the direction of the length of the plate.  
     
     
         39 . The retainer assembly of  claim 38 , wherein each of said apertures include a countersink portion communication with said slot.  
     
     
         40 . The retainer assembly of  claim 39 , wherein said countersink portion of at least one of said apertures is tapered and has a width that increases along the length of said aperture from a second end to a first end.  
     
     
         41 . A fastener retainer assembly for an elongated plate extending between at least two vertebrae, the plate defining a number of openings for insertion of bone engaging fasteners therethrough to secure the plate to the at least two vertebrae, and the plate defining at least one fastener bore, said retainer assembly comprising: 
 a washer having a central axis and defining at least a firs aperture in communication with said at least one fastener bore, said washer further configured to retain said heads of at least two bone engaging fasteners extending through certain ones of said openings in said plate; and    a locking fastener for said first aperture having an elongated shank extending through said aperture and configured to engage said fastener bore of said plate, said washer being movable along said central axis between a first position whereby said at least two bone engaging fasteners are insertable into certain ones of said openings and a second position whereby washer retains said at least two bone engaging fasteners in said plate.    
     
     
         42 . The retainer assembly of  claim 41 , wherein said apertures of said washer form slots having a length extending in the direction of the length of the plate.  
     
     
         43 . The retainer assembly of  claim 42 , wherein each of said apertures include a countersink portion communication with said slot.  
     
     
         44 . The retainer assembly of  claim 42 , wherein said countersink portion of at least one of said apertures is tapered and has a width that increases along the length of said aperture from a second end to a first end.  
     
     
         45 . A method for applying a compressive load to a portion of the spinal column, the spinal column portion including at least a first vertebra and a second vertebra, the method comprising: 
 engaging a pin to the second vertebra;    placing a sleeve over the pin;    providing a plate having a length extending between a first end and a second end, the plate including a notch on the second end, and a number of openings through the plate;    placing the plate on the spinal column portion with the sleeve nested in the radius of the plate;    fixing the first end of the plate to the first vertebra with bone engaging fasteners extending through the openings positioned over the first vertebra;    removing the sleeve from the pin to form a gap between the pin and the notch;    connecting a compression tool to the pin and the plate; and    applying a compression load to the spinal column portion with the compression tool until the pin contacts the notch.    
     
     
         46 . The method according to  claim 45 , wherein engaging a pin to the second vertebra includes: 
 providing a template having a guide surface and a notch;    positioning the template on the second vertebra with the guide surface on an endplate of the second vertebra to locate the notch on the body of the second vertebra;    inserting a pin through the notch of the template into the body of the second vertebra; and    removing the template;    
     
     
         47 . The method according to  claim 45 , further comprising providing a plate with holes positioned over the first vertebra and slots positioned over the second vertebra.  
     
     
         48 . The method according to  claim 45 , further comprising retaining the bone engaging fasteners in the plate with a retainer assembly.  
     
     
         49 . A method for allowing graft settling in a portion of a spinal column, comprising: 
 providing a plate having a length between a first end and a second end sized to span at least two vertebra, the plate having a pair of holes at the first end positioned over the first vertebra and a pair of slots at the second end positioned over the second vertebra;    fixing the first end of the plate to the first vertebra with bone engaging fasteners extending through the pair of holes;    securing the second end of the plate to the second vertebra with bone engaging fasteners extending through the pair of slots; and    translating the bone engaging fasteners in the slots to allow settling of the spinal column portion.    
     
     
         50 . The method according to  claim 49 , further comprising retaining the bone engaging fasteners in the plate with a retainer assembly.  
     
     
         51 . The method according to claim  50 , wherein the retainer assembly includes a washer having a length substantially corresponding to the length of the plate.