Device and method for resiliently locking a screw to a plate

Abstract

A spinal fixation device for stabilizing one or more segments of the human spine and for preventing the dislodgement of intervertebral spinal fusion implants, which remains permanently fixated once applied.

1 . A spinal device for stabilizing two adjacent cervical vertebral bodies of the human spine, each of the adjacent cervical vertebral bodies having an anterior aspect, said device comprising:
 a member having an upper surface, a lower surface opposite said upper surface, and a length sufficient to span a disc space between the two adjacent cervical vertebral bodies, said lower surface being adapted to contact the anterior aspect of each of the two adjacent cervical vertebral bodies, said member including a screw hole having a central longitudinal axis and a depth from said upper surface to said lower surface along the central longitudinal axis, said screw hole intersecting with said upper surface to form an entrance having a diameter, said screw hole intersecting with said lower surface to form an exit having a diameter, said screw hole having an interior surface from said entrance to said exit, said interior surface including a circumferential recess around the central longitudinal axis of said screw hole, said circumferential recess having a maximum diameter greater than the diameter of said exit, the maximum diameter of said circumferential recess of said interior surface being greater than the diameter of said entrance of said screw hole, said circumferential recess of said interior surface including a circumferential projection having an inner diameter less than the maximum diameter of said circumferential recess; and   a screw having a head, a shaft, a mid-longitudinal axis and a length along the mid-longitudinal axis, said shaft including a thread, said screw being configured for insertion into said screw hole of said member, said length of said screw being greater than the depth of said screw hole, said head including a circumferential ledge having an outer diameter greater than the inner diameter of said circumferential projection, said circumferential ledge of said screw and said circumferential projection cooperating together to resiliently lock said screw to said member when said screw is inserted into said screw hole and said circumferential ledge of said screw is below the inner diameter of said circumferential projection.   
     
     
         2 . The device of  claim 1 , wherein said projection is a lip. 
     
     
         3 . The device of  claim 1 , wherein said member includes a plurality of through-holes having a diameter less than the diameter of said entrance of said screw hole. 
     
     
         4 . The device of  claim 1 , wherein said member has two ends defining the length of said member, said member including two through-holes that each have a diameter less than the diameter of said entrance of said screw hole, each through-hole being proximate a respective one of said ends of said member. 
     
     
         5 . The device of  claim 1 , wherein said member includes a width transverse to the length of said member, said member including opposite sides along the length, one of said sides having a portion curved partially around the central longitudinal axis of said screw hole. 
     
     
         6 . The device of  claim 5 , wherein the other of said sides is straight. 
     
     
         7 . The device of  claim 1 , wherein said member is generally triangular-shaped. 
     
     
         8 . The device of  claim 1 , wherein said lower surface of said member includes two ratcheted projections at opposite ends of said member. 
     
     
         9 . The device of  claim 1 , wherein said screw hole is a fixed-angle screw hole. 
     
     
         10 . The device of  claim 1 , wherein said screw hole is centrally located along the length of said member. 
     
     
         11 . The device of  claim 1 , wherein said thread of said screw has a maximum diameter, said screw including a non-threaded portion below said ledge, said non-threaded portion having a diameter equal to the maximum diameter of said thread of said screw. 
     
     
         12 . The device of  claim 1 , wherein said shaft has an insertion end, said thread of said screw having a reduced pitch proximate said insertion end of said shaft. 
     
     
         13 . The device of  claim 1 , wherein said head of said screw is resiliently flexible to cooperatively lock said screw to said member. 
     
     
         14 . The device of  claim 1 , in combination with a spinal implant, said screw being adapted to couple said member to said spinal implant. 
     
     
         15 . A spinal device for stabilizing two adjacent cervical vertebral bodies of the human spine, each of the adjacent cervical vertebral bodies having an anterior aspect, said device comprising:
 a member having an upper surface, a lower surface opposite said upper surface, and a length sufficient to span a disc space between the two adjacent cervical vertebral bodies, said lower surface being adapted to contact the anterior aspect of each of the two adjacent cervical vertebral bodies, said member including a screw hole having a central longitudinal axis and a depth from said upper surface to said lower surface along the central longitudinal axis, said screw hole including a circumferential anti-back out element having an inner diameter centered at the central longitudinal axis of said screw hole; and   a screw having a head, a shaft, a mid-longitudinal axis and a length along the mid-longitudinal axis, said shaft including a thread, the length of said screw being greater than the depth of said screw hole, said head including a circumferential ledge having an outer diameter greater than the inner diameter of said circumferential anti-back out element, said circumferential ledge of said screw and said circumferential anti-back out element cooperating together to resiliently lock said screw to said member when said screw is inserted into said screw hole and said circumferential ledge of said screw is below the inner diameter of said circumferential anti-back out element.   
     
     
         16 . The device of  claim 15 , wherein said circumferential anti-back out element is a lip. 
     
     
         17 . The device of  claim 15 , wherein said screw hole has a maximum diameter, said member including a plurality of through-holes having a diameter less than the maximum diameter of said screw hole. 
     
     
         18 . The device of  claim 15 , wherein said screw hole has a maximum diameter, said member having two ends defining the length of said member, said member including two through-holes that each have a diameter less than the maximum diameter of said screw hole, each through-hole being proximate a respective one of said ends of said member. 
     
     
         19 . The device of  claim 15 , wherein said member includes a width transverse to the length of said member, said member including opposite sides along the length, one of said sides having a portion curved partially around the central longitudinal axis of said screw hole. 
     
     
         20 . The device of  claim 19 , wherein the other of said sides is straight. 
     
     
         21 . The device of  claim 15 , wherein said member is generally triangular-shaped. 
     
     
         22 . The device of  claim 15 , wherein said lower surface of said member includes two ratcheted projections at opposite ends of said member. 
     
     
         23 . The device of  claim 15 , wherein said screw hole is a fixed-angle screw hole. 
     
     
         24 . The device of  claim 15 , wherein said screw hole is centrally located along the length of said member. 
     
     
         25 . The device of  claim 15 , wherein said thread of said screw has a maximum diameter, said screw including a non-threaded portion below said ledge, said non-threaded portion having a diameter equal to the maximum diameter of said thread of said screw. 
     
     
         26 . The device of  claim 15 , wherein said shaft has an insertion end, said thread of said screw having a reduced pitch proximate said insertion end of said shaft. 
     
     
         27 . The device of  claim 15 , wherein said head of said screw is resiliently flexible to cooperatively lock said screw to said member. 
     
     
         28 . The device of  claim 15 , in combination with a spinal implant, said screw being adapted to couple said member to said spinal implant. 
     
     
         29 . A spinal device for stabilizing two adjacent cervical vertebral bodies of the human spine, each of the adjacent cervical vertebral bodies having an anterior aspect, said device comprising:
 a member having an upper surface, a lower surface opposite said upper surface, and a length sufficient to span a disc space between the two adjacent cervical vertebral bodies, said lower surface being adapted to contact the anterior aspect of each of the two adjacent cervical vertebral bodies, said member including a screw hole having a central longitudinal axis and a depth from said upper surface to said lower surface along the central longitudinal axis; and   a securing means for resiliently locking a head of a screw to said member, said securing means circumferentially surrounding a mid-longitudinal axis of said screw.   
     
     
         30 . The device of  claim 29 , wherein said securing means includes a lip. 
     
     
         31 . The device of  claim 29 , wherein said securing means includes a recess. 
     
     
         32 . The device of  claim 29 , wherein said securing means includes a flange surrounding said head of said screw. 
     
     
         33 . The device of  claim 29 , wherein said screw hole has a maximum diameter, said member including a plurality of through-holes having a diameter less than the maximum diameter of said screw hole. 
     
     
         34 . The device of  claim 29 , wherein said screw hole has a maximum diameter, said member having a length with two ends, said member including two through-holes that each have a diameter less than the maximum diameter of said screw hole, each through-hole being proximate a respective one of said ends of said member. 
     
     
         35 . The device of  claim 29 , wherein said member includes a width transverse to the length of said member, said member including opposite sides along the length, one of said sides having a portion curved partially around the central longitudinal axis of said screw hole. 
     
     
         36 . The device of  claim 35 , wherein the other of said sides is straight. 
     
     
         37 . The device of  claim 29 , wherein said member is generally triangular-shaped. 
     
     
         38 . The device of  claim 29 , wherein said lower surface of said member includes two ratcheted projections at opposite ends of said member. 
     
     
         39 . The device of  claim 29 , wherein said screw hole is a fixed-angle screw hole. 
     
     
         40 . The device of  claim 29 , wherein said screw hole is centrally located along the length of said member. 
     
     
         41 . The device of  claim 29 , wherein said screw has a shaft with an insertion end, said screw having a thread with a reduced pitch proximate said insertion end of said shaft. 
     
     
         42 . A method for stabilizing two adjacent vertebral bodies of the human spine, each of the adjacent vertebral bodies having an anterior aspect, the method comprising:
 implanting a spinal implant at least in part into a disc space between the two adjacent vertebral bodies;   placing a lower surface of a member against the anterior aspects of the two adjacent vertebral bodies to span the disc space containing the spinal implant, the member including a screw hole having a central longitudinal axis and a projection circumferentially surrounding the central longitudinal axis of the screw hole;   inserting a screw having a head with a circumferential ledge into the screw hole so that the circumferential ledge of the head of the screw resiliently engages the circumferential projection; and   blocking outward excursion of the screw from the screw hole with the circumferential projection contacting a portion of the circumferential ledge of the head of the screw.   
     
     
         43 . The method of  claim 42 , wherein the inserting of the screw includes flexing a portion of the head of the screw. 
     
     
         44 . The method of  claim 42 , wherein the inserting of the screw includes inserting a portion of the screw into the spinal implant. 
     
     
         45 . The method of  claim 42 , further comprising compressing the two adjacent vertebral bodies toward one another.