Minimally invasive spinal stabilization system

Abstract

A spinal fixation assembly including a pedicle rod and pedicle screws which secure the pedicle rod to the spine. Each pedicle screw includes a head configured to receive a portion of the pedicle rod, and a threaded portion extending from a first end of the head and configured to engage a vertebra. The pedicle rod is secured to the head by a fastener. The head includes a breakaway region that defines a location in which at least a first portion of the head can be easily separated from the remainder of the head upon application of sufficient force to the first portion.

1 . A minimally invasive spinal fixation assembly configured to provide relative fixation of a series of vertebrae, comprising:
 a pedicle rod;   pedicle screws, each screw including
 a head configured to receive a portion of the pedicle rod, the head having a first end and an open second end opposed to the first end, the head being generally tubular and formed of a single piece having a first opening that extends from the open second end along an axial direction of the head to a location adjacent to, and spaced apart from, the first end, and a second opening on an opposed side of the head relative to the first opening, the second opening extending from the open second end along an axial direction of the head to a location adjacent to and spaced apart from the first end, the first and second openings being diametrically aligned so as to form a transverse through channel through the head, and a threaded portion extending from the first end of the head and configured to engage one of the vertebrae, 
   a fastener including external threads configured to engage corresponding threads formed on an inner surface of the head; and   a cap configured to engage the open second end of the head, wherein the pedicle rod is a hollow tube and is secured to the head by the fastener, and the head includes a breakaway region between the first end and the open second end, the breakaway region including a portion of the head that is formed to be relatively structurally weak compared to the remaining portions of the head so as to define a location in which at least a first portion of the head can be easily separated from the remainder of the head upon application of sufficient force to the first portion of the head.   
     
     
         2 . The minimally invasive spinal fixation assembly of  claim 1 , wherein the pedicle rod is configured to engage a suture. 
     
     
         3 . The minimally invasive spinal fixation assembly of  claim 1 , wherein the cap includes a hollow cylindrical body having
 an open end dimensioned to receive therein the open second end of the head, and   an opposed end, the opposed end including a central cap opening, wherein the open end includes an interior surface having an annular protrusion, and the head includes a circumferential groove adjacent to the open second end configured to engage the annular protrusion whereby the cap can be releasably secured to the open second end of the head.   
     
     
         4 . The minimally invasive spinal fixation assembly of  claim 3 , further comprising a U-shaped pedicle screw stabilizer including
 a grip portion;   an annular base extending from one side of the grip portion and having a diameter substantially equal to the diameter of the head; and   a pair of legs extending from one side of the annular base, the legs configured to conform to the shape of, and be received within, the respective first and second openings of the head.   
     
     
         5 . The minimally invasive spinal fixation assembly of  claim 4 , wherein the central cap opening is configured to receive therethrough the legs of the U-shaped pedicle screw stabilizer. 
     
     
         6 . The minimally invasive spinal fixation assembly of  claim 5 , wherein a portion of the edge of the cap corresponding to the central cap opening is formed having a shape that conforms to a cross sectional shape of a leg. 
     
     
         7 . The minimally invasive spinal fixation assembly of  claim 1 , further comprising a pedicle screw breaking device configured to be received within an interior space of the head and to facilitate separation of the open second end of the head from the first end of the head along a prescribed circumferential breakaway line provided on the head between the first end and the open second end of the head. 
     
     
         8 . The minimally invasive spinal fixation assembly of  claim 1 , further comprising a suture guide assembly including
 a suture leader configured to retain a suture, and   a guide tool including pivotably-joined first and second arms, the first arm terminating at a first end in a male suture guide, the second arm terminating at a first end in a female suture guide,   wherein the male and female suture guides are configured to permit the suture leader to be passed from the male suture guide to the female suture guide upon movement of the first and second arms between an open position in which the male and female suture guides are spaced apart and a closed position in which the male and female suture guides are adjacent.   
     
     
         9 . The minimally invasive spinal fixation assembly of  claim 8 , wherein the suture leader comprises
 a tip shaped to facilitate insertion into the female suture guide, and   an opening formed adjacent to the tip.   
     
     
         10 . The minimally invasive spinal fixation assembly of  claim 8 , wherein the first and second arms are configured to be received within the hollow interior space of the head and pass through the first and the second opening. 
     
     
         11 . The minimally invasive spinal fixation assembly of  claim 1 , wherein the series of vertebrae includes at least two vertebrae. 
     
     
         12 . The minimally invasive spinal fixation assembly of  claim 1 , wherein the spinal fixation assembly is configured to be implemented via non-continuous wound sites having a length generally corresponding to a cross sectional dimension of the head. 
     
     
         13 . A pedicle screw for use in spinal fixation, comprising:
 a head including a first end, an open second end opposed to the first end;   a threaded body extending from the first end; and   a removable cap configured to close the head second end for stabilizing the open second end, the removable cap being a hollow cylinder having a sidewall including a transverse through channel,   
       wherein the head is tubular, and is formed of a single piece having a first opening that extends from the open second end along an axial direction of the head to a location adjacent to, and spaced apart from, the first end, and a second opening on an opposed side of the head relative to the first opening, the second opening extending from the open second end along an axial direction of the head to a location adjacent to and spaced apart from the first end, the first and second openings being diametrically aligned so as to form a transverse through channel through the head, the head having a breakaway region located between the first end and the open second end, the breakaway region including a portion of the head that is formed to be relatively structurally weak compared to the remaining portions of the head so as to define a location in which at least a portion of the open second end can be easily separated from the head upon application of sufficient force to the open second end. 
     
     
         14 . The pedicle screw of  claim 13 , wherein the distance between the first end and the open second end of the head is in a range from 40 mm to 120 mm. 
     
     
         15 . The pedicle screw of  claim 13 , wherein the distance between the first end and the open second end of the head is in a range from 50 mm to 80 mm. 
     
     
         16 . The pedicle screw of  claim 13 , wherein the portion of the head that is formed to be relatively structurally weak includes a circumferential groove, the circumferential groove configured to provide a prescribed breakaway line along which at least a portion of the open second end can be easily separated from the head 
     
     
         17 . The pedicle screw of  claim 13 , wherein the force is a twisting force about a longitudinal axis of the head. 
     
     
         18 . The pedicle screw of  claim 13 , wherein the head includes a circumferential groove adjacent to the open second end configured to engage a corresponding annular lip provided on an interior surface of the removable cap. 
     
     
         19 . The pedicle screw of  claim 13 , wherein the first end of the head is configured to permit poly-axial rotation of the threaded body relative to the head.