Spinal implant

Abstract

A screw and rod fixation assembly includes a body member including a screw seat for seating a screw head therein and a rod seat for seating a rod therein. An adjustable locking ring applies a locking force against the screw head seated in the screw seat and a locking cap adjustably applies a locking force against a rod seated in the rod seat. The adjustable screw locking ring and locking cap function independent of each other. A method of fixing the rod to the screw includes the steps of inserting a screw head into a screw seat in one end of a body member and inserting a rod into a rod seat in a second end of a body member and selectively and independently adjusting a locking force on both the screw head and the rod within the screw seat and rod seat, respectively.

1 . A screw and rod fixation assembly comprising:
 a body member including a screw seat for seating a screw head therein and a rod seat for seating a rod therein,   adjustable rod locking means for adjustably applying a locking force against a rod seated in said rod seat; and   adjustable screw locking means for adjustably applying a locking force to a screw head seated in said screw seat, said adjustable screw locking means being functionally independent of said adjustable rod locking means.   
     
     
         2 . An assembly as set forth in  claim 1 , wherein said body member includes a first end having a pocket therein, said pocket including outwardly flexible walls for receiving and retaining a screw head therein, thereby defining said screw seat, said adjustable screw locking means including a compressor member disposable over said outwardly flexible walls for adjustably compressing said outwardly flexible walls in locking engagement against the screw head. 
     
     
         3 . An assembly as set forth in  claim 2 , wherein said screw seat includes at least one slot therein provides outward flexibility to said screw seat and thereby allowing a screw head to enter therein. 
     
     
         4 . An assembly as set forth in  claim 2 , wherein said compressor member includes a locking ring having an internal bore defined by a straight cylindrical wall, said first end of said body member including an outer surface tapering outwardly when a screw head is seated within said screw seat towards said first end, said internal bore of said locking ring interacting with said outer surface to selectively and adjustably compress said pocket about the screw head as said locking ring is moved there along. 
     
     
         5 . An assembly as set forth in  claim 2 , wherein said body portion includes a second end including a base portion and two spaced arms extending therefrom defining said rod seat, said adjustable rod locking means including compressing means for adjustably and selectively compressing said arms about a rod seated in said rod seat to adjustably and selectively lock the rod in said rod seat. 
     
     
         6 . An assembly as set forth in  claim 5 , wherein said rod locking means including an annular body portion having an internal bore for receiving and retaining said arms therein, said arms being outwardly flexible to allow outward deflection of said arms when a rod is seated therein, said bore having a predetermined diameter small than a diameter defined by a distance between an opposing outer surface of said arms, whereby application of said body portion about said arms selectively radially inwardly deflects said arms to adjustably grip and lock the rod seated within said rod seat. 
     
     
         7 . An assembly as set forth in  claim 6 , including fixing means for fixed locking said rod locking means in locked engagement with a rod seated in said rod seat. 
     
     
         8 . An assembly as set forth in  claim 7 , said arms include a radially outwardly extending projection, said rod locking means including a recess for mating engagement with said projections when said rod locking means is in locking engagement with the rod seated in said rod seat. 
     
     
         9 . An assembly as set forth in  claim 7 , wherein said arms include recesses therein and said rod locking means including radially inwardly extending projections for mating engagement with said recesses when said rod locking means is in locking engagement with the rod seated in said rod seat. 
     
     
         10 . An assembly as set forth in  claim 1 , wherein said rod seat includes a substantively spherical inner surface. 
     
     
         11 . A screw and rod fixation member comprising a body portion including a first end having a screw seat for seating a screw head therein and a second end including a rod seat for seating a rod therein, said first end including a pocket therein having outwardly flexible walls for receiving a screw head therein, thereby defining said screw seat and a said second end including a base portion and two spaced arms extending therefrom defining said rod seat, said arms including a smooth outer surface and fixing means for engagement with a rod locking member. 
     
     
         12 . A fixation screw comprising a threaded portion for engagement with base and a head pocket and a neck portion therebetween, said screw head including multiple engagement surfaces for contacting multiple areas of a spherical screw seat surface. 
     
     
         13 . An assembly as set forth in  claim 12 , wherein said screw head includes a radially outer cylinder surface having oppositely disposed upper and lower tapered portions defining a diamond or square, said tapered surfaces defining said multiple engagement surfaces. 
     
     
         14 . A method of fixing a rod to a screw by:
 inserting a screw head into a screw seat in one end of a body member;   inserting a rod into a rod seat in a second end of the body member; and   selectively and independently adjusting a locking force on both the screw head and rod within the screw seat and rod seat, respectively.   
     
     
         15 . A method as set forth in  claim 14 , further including the step of inserting the screw head into the screw seat and a locking ring about the body portion and spaced from the outer surface of the screw seat prior to surgery; and insert the rod with the rod seat and independently and selectively apply a locking force of the locking ring to the screw seat and rod locking member about an outer surface of the rod seat during surgery. 
     
     
         16 . A method as set forth in  claim 15 , further including the steps of independently and adjustably forcing locking means on the locking ring about the screw seat and on the rod locking member about the rod seat. 
     
     
         17 . A method of fixing a rod to a screw head by seating a screw head having multiple contact points in a screw seat of a body portion causing the screw head to interfere with and contact multiple portions of the spherical seat creating sufficient friction to lock the screw head in a desired position during rod insertion while allowing the body portion to rotate relative to the screw head. 
     
     
         18 . A method as set forth in  claim 17 , further including the steps of:
 fixing at least one screw in a bone;   the screw seat as in  claim 17 , and   adjusting the position of the rod seat relative to the screw during seating of the rod into the screw seat.   
     
     
         19 . A method as set forth in  claim 17 , including the step of radially outwardly deflecting an outer surface of the screw seat and forming an outwardly tapering outer surface and;
 disposing a locking ring over the outwardly tapering surface to lock the screw head in the screw seat.   
     
     
         20 . A fixation screw assembly comprising a screw including a head portion for engagement with a seat portion within a body member, said head portion having a larger dimension than said seat portion such that said screw head portion creates interference with the body seat portion when seated therein. 
     
     
         21 . An assembly of  claim 20 , whereby said interference of the fixation screw head with said seat portion of the body forces said body section around said screw head to be forced radially outwardly creating a taper in an outer surface of an external lower portion of said body member. 
     
     
         22 . An implant comprising a body portion having a U shaped rod receiving slot, said U shaped slot being smaller in width than the width of a rod seated therein and having a seated condition when the rod is seated within the U shaped channel such that the rod forces arms of the U shaped slot radially outwardly creating a taper, said taper at an open end of the U shaped slot being larger in diameter and tapering to a smaller diameter at a base of said U shaped slot. 
     
     
         23 . The assembly of  claim 22 , wherein said taper created by the rod seated in the U shaped slot contours around the rod when a locking cap engages the larger diameter opening of the U shaped slot and forces the arms of the U shaped slot inward around the rod. 
     
     
         24 . The assembly of  claim 23 , wherein said U shaped slot is defined by two arms, each of said arms having a distal end defining said opening of said U shaped slot, each of said distal ends having a baffled portion to allow ease of disposal of said locking cap over said distal ends. 
     
     
         25 . A method of retaining a rod in a U shaped slot of a body member of a rod fixation assembly by inserting a rod into a rod seat that is smaller in diameter than the rod while forcing the arms of the rod seat radially outwardly to form an outer taper on the outside surface of the rod seat, and disposing a rod locking cap over the spread arms of the rod seat, the rod locking cap forcing the arms radially inwardly and forcing the arms of the rod seat around the rod.