Spinal Stabilization Device

Abstract

A flexible connection unit for use in a spinal fixation device that includes: a longitudinal member having first and second ends and a flexible member interposed between the first and second ends, at least one of the first end and second end configured to be engaged by a first bone securing member; and at least one spacer located between the first and second ends, the spacer comprising a resilient element and a ring element encircling at least a portion of the resilient element, wherein the ring element is configured to be engaged by a second bone securing member.

What is claimed: 
     
         1 . A flexible, elongated connection unit for stabilizing a human spine where the flexible connection unit is configured to be surgically implanted into the human body adjacent the spine and held in place by a first and a second pedicle screw assembly that are configured to be anchored into a first and second, adjacent vertebra, respectively, the flexible, elongated connection unit comprising:
 (a) a first, metallic rigid portion having an outer surface configured to be secured within the first pedicle screw assembly;   (b) a second, metallic rigid portion;   (c) a cylindrical flexible member extending from the first rigid portion to the second rigid portion and directly secured to the second rigid portion; and   (d) a longitudinally compressible spacer comprising:
 (1) a metallic, rigid portion having a length and having an inner bore extending the length of the spacer metallic portion, the flexible member extending through the bore of the spacer metallic portion, the inner bore of the spacer metallic portion having a larger dimension than a diameter of an outer surface of the flexible member along the length of the spacer metallic portion bore such that the spacer metallic portion can slide over the outer surface of the flexible member along a length of the flexible member, and where the spacer metallic portion has an outer surface configured to be secured within the second pedicle screw assembly, the spacer metallic portion being located entirely between the first rigid portion and the second rigid portion such that along the length of the connection unit no portion of the spacer metallic portion overlaps with any portion of the first or second rigid portion; 
 (2) a first elastomeric portion located between the first rigid portion and the spacer metallic portion, the first elastomeric portion having a length and having an inner bore extending the length of the first elastomeric portion with the flexible member extending through the bore of the first elastomeric portion; and 
 (3) a second elastomeric portion located between the second rigid portion and the spacer metallic portion, the second elastomeric portion having a length and having an inner bore extending the length of the second elastomeric portion with the flexible member extending through the bore of the second elastomeric portion; 
   whereby the first and second elastomeric spacer portions limit sliding of the spacer metallic portion over the flexible member along the length of the flexible member.   
     
     
         2 . The flexible connection unit of  claim 1 , wherein the spacer metallic portion is physically separate from and does not physically contact the first rigid portion or the second rigid portion. 
     
     
         3 . The flexible connection unit of  claim 1 , wherein the spacer metallic portion is not integral with the first rigid portion or the second rigid portion. 
     
     
         4 . The flexible connection unit of  claim 1 , wherein the second rigid portion has a longitudinal dimension that is shorter than the longitudinal dimension of both the first elastomeric portion and the second elastomeric portion individually. 
     
     
         5 . The flexible connection unit of  claim 1 , wherein the first and second elastomeric spacer portions limit sliding of the spacer metallic portion over the flexible member in response to external forces of the magnitude experienced from movement of the spine applied to the first rigid portion and the spacer metallic portion. 
     
     
         6 . The flexible connection unit of  claim 1 , wherein the spacer is constructed such that the first elastomeric portion physically separates the first rigid portion and the spacer metallic portion and the second elastomeric portion physically separates the second rigid portion and the spacer metallic portion. 
     
     
         7 . The flexible connection unit of  claim 6 , wherein the spacer metallic portion physically separates the first and second elastomeric portions. 
     
     
         8 . The flexible connection unit of  claim 6 , wherein both the first and second spacer elastomeric portions comprise polycarbonate urethane. 
     
     
         9 . The flexible connection unit of  claim 6 , wherein the first rigid portion is longer than the second rigid portion. 
     
     
         10 . The flexible connection unit of  claim 1 , wherein the flexible member is metallic. 
     
     
         11 . A method for stabilizing a human spine with a flexible, elongated connection unit, comprising:
 (a) securing a first pedicle screw assembly to a first vertebra and a second pedicle screw assembly to a second vertebra;   (b) securing the flexible connection unit to the first and second pedicle screw assemblies, wherein the flexible connection unit comprises:
 (1) a first, metallic rigid portion; 
 (2) a second, metallic rigid portion; 
 (3) a flexible member extending from the first rigid portion to the second rigid portion and directly secured to the second rigid portion; 
 (4) a longitudinally compressible spacer extending between the first rigid portion and the second rigid portion, the spacer comprising:
 (i) a metallic, rigid portion having a length and having an outer surface and an inner bore extending the length of the spacer metallic portion, the flexible member extending through the inner bore of the spacer metallic portion, the inner bore of the spacer metallic portion having a larger dimension than an outer surface of the flexible member along the length of the spacer metallic portion bore such that the spacer metallic portion can slide over the outer surface of the flexible member along a length of the flexible member; 
 (ii) a first elastomeric portion located between the first rigid portion and the spacer metallic portion, the first elastomeric portion having a length and having an inner bore extending the length of the first elastomeric portion with the flexible member extending through the bore of the first elastomeric portion; 
 (iii) a second elastomeric portion located between the second rigid portion and the spacer metallic portion, the second elastomeric portion having a length and having an inner bore extending the length of the second elastomeric portion with the flexible member extending through the bore of the second elastomeric portion; 
 
   wherein the flexible connection unit is secured by securing the first, metallic rigid portion to the first pedicle screw assembly and securing the spacer metallic, rigid portion to the second pedicle screw assembly;   whereby the first and second elastomeric spacer portions limit sliding of the spacer metallic portion along the length of the flexible member.   
     
     
         12 . The method of  claim 11 , wherein the spacer metallic portion is physically separate from and does not physically contact the first rigid portion or the second rigid portion. 
     
     
         13 . The method of  claim 11 , wherein the second rigid portion has a longitudinal dimension that is shorter than the longitudinal dimension of both the first elastomeric portion and the second elastomeric portion individually. 
     
     
         14 . The method of  claim 11 , wherein the spacer is constructed such that the first elastomeric portion physically separates the first rigid portion and the spacer metallic portion and the second elastomeric portion physically separates the second rigid portion and the spacer metallic portion. 
     
     
         15 . The method of  claim 14 , wherein the spacer metallic portion physically separates the first and second elastomeric portions. 
     
     
         16 . The method of  claim 15 , wherein the outer, longitudinal surface of each of the first rigid portion and the spacer metallic portion is cylindrical. 
     
     
         17 . The method of  claim 15 , wherein the first rigid portion is longer than the second rigid portion. 
     
     
         18 . The method of  claim 17 , wherein the spacer metallic portion is longer than the second rigid portion. 
     
     
         19 . The method of  claim 11 , wherein the second elastomeric portion can be compressed between the spacer metallic portion and the second rigid portion.