Longitudinal connecting member with sleeved tensioned cords and releasable end blocker-bumper

Abstract

A dynamic fixation medical implant having at least two bone anchors includes a longitudinal connecting member assembly having rigid sleeves for attachment to the bone anchors, at least one spacer engaging the bone anchors and the sleeves, and in some embodiments, an end elastic bumper. A flexible cord is initially slidingly received within the rigid sleeves, the spacer and the bumper. The spacer may include an optional inelastic inner liner, with at least one of the sleeves having an extension slidingly receivable within the liner. Some sleeves include apertures for receiving a closure top portion for locking the cord against the sleeve, or alternatively receiving a closure top that does not extend into the aperture, the slip or grip option provided by the aperture in each sleeve resulting in an overall connector with variable segmental stiffness.

What is claimed and desired to be secured by Letters Patent is as follows: 
     
         1 . In a medical implant assembly having at least first and second bone anchors cooperating with a longitudinal connecting member having a tensioned cord, the bone anchors having opposed upstanding arms, the improvement comprising:
 a) a first non-elastic sleeve for attachment to the first bone anchor, the first sleeve having a first through bore sized and shaped for slidably receiving the tensioned cord, a first aperture formed in the sleeve substantially transverse to the through bore, the aperture sized and shaped for receiving a portion of a first optional cord gripping closure top and a first body portion sized and shaped for being closely received between the bone anchor arms;   b) a second non-elastic sleeve for attachment to the second bone anchor, the second sleeve having a second through bore sized and shaped for slidably receiving the tensioned cord, a second aperture formed in the sleeve substantially transverse to the second through bore, the second aperture sized and shaped for receiving a portion of a second optional cord gripping closure top and a second body portion sized and shaped for being closely received between the second bone anchor arms; and   c) a spacer located between the first and second bone anchors, the spacer engaging each of the first and second sleeves, the cord extending through the spacer and held in tension at at least first and second ends of the connecting member.   
     
     
         2 . The improvement of  claim 1  comprising at least a first closure top having an extended portion in gripping contact with the cord and fixed to one of the first and second sleeves. 
     
     
         3 . The improvement of  claim 1  comprising at least a second closure top having a surface in gripping contact with one of the first and second sleeves, the closure top being spaced from the cord. 
     
     
         4 . The improvement of  claim 1  wherein at least one of the first and second sleeves includes an extension slidingly received within the spacer. 
     
     
         5 . The improvement of  claim 4  further comprising a hard inner liner disposed between the extension and the spacer. 
     
     
         6 . The improvement of  claim 1  wherein at least one of the first and second sleeves includes an outer flange abutting against an outer surface of the spacer. 
     
     
         7 . The improvement of  claim 6  wherein the outer flange is a first outer flange and further comprising a second outer flange substantially parallel to the first outer flange, each flange being disposed outside of the bone anchor. 
     
     
         8 . The improvement of  claim 7  further comprising at least one tubular structure extending outwardly from at least one of the flanges. 
     
     
         9 . The improvement of  claim 6  wherein the outer flange is a first outer flange and further comprising a second outer flange disposed at an obtuse angle with respect to the first outer flange, each flange being disposed outside of the bone anchor. 
     
     
         10 . The improvement of  claim 9  further comprising at least one tubular structure extending outwardly from at least one of the flanges. 
     
     
         11 . The improvement of  claim 1  wherein at least one of the first and second sleeves has an outer surface flush with an outer surface of the bone anchor. 
     
     
         12 . The improvement of  claim 1  wherein at least one of the first and second sleeves has a first U-shaped lower surface sized and shaped to frictionally engage a second U-shaped surface of a pressure insert located within the bone anchor. 
     
     
         13 . The improvement of  claim 1  wherein at least one of the first and second sleeves has a first planar surface in frictional engagement with a second planar surface of a pressure insert located within the bone anchor. 
     
     
         14 . The improvement of  claim 1  wherein the bone anchor is a polyaxial bone screw having a shank pivotable with respect to a receiver, at least one of the first and second sleeves being held within the receiver and directly engaging the shank. 
     
     
         15 . In a medical implant assembly having at least first and second bone anchors cooperating with a longitudinal connecting member, the improvement wherein the connecting member comprises:
 a) a first non-elastic sleeve for attachment to the first bone anchor, the first sleeve having at least a first extension;   b) a second non-elastic sleeve for attachment to the second bone anchor;   c) a spacer located between the first and second bone anchors, the spacer engaging the first and second sleeves, the spacer received over the first extension and being movable with respect thereto; and   d) a tensioned cord slidingly received within the first and second sleeves and the spacer, the cord being in one of a fixed and slidable relation with respect to the first and second sleeves.   
     
     
         16 . The improvement of  claim 15  wherein at least one of the sleeves has an aperture formed therein sized and shaped to receive a portion of a closure top, the closure top portion being fixed against the cord. 
     
     
         17 . The improvement of  claim 15  further comprising a hard liner disposed between the first extension and the spacer, the first extension being in slidable relation with the hard liner, the liner being in fixed relation with the spacer. 
     
     
         18 . In a surgical method for implanting a tensioned cord between at least first and second implanted bone anchors with a spacer disposed between the bone anchors, the bone anchors having opposed upstanding arms, the improvement comprising:
 a) providing a first non-elastic sleeve for attachment to the first bone anchor, the first sleeve having a first through bore sized and shaped for slidably receiving the cord, a first aperture formed in the sleeve substantially transverse to the through bore, the aperture sized and shaped for receiving a portion of a first optional cord gripping closure top and a first body portion sized and shaped for being closely received between the bone anchor arms;   b) providing a second non-elastic sleeve for attachment to the second bone anchor, the second sleeve having a second through bore sized and shaped for slidably receiving the cord, a second aperture formed in the sleeve substantially transverse to the second through bore, the second aperture sized and shaped for receiving a portion of a second optional cord gripping closure top and a second body portion sized and shaped for being closely received between the second bone anchor arms;   c) loading the first sleeve on the cord, followed by the spacer, followed by the second sleeve;   d) inserting the first sleeve in the first bone anchor and the second sleeve in the second bone anchor;   e) tensioning the cord and fixing the cord at each end of the connector;   f) optionally fixing the cord to one of the first and second bone anchors by inserting a closure top through one of the first and second sleeves into engagement with the cord; and   g) optionally allowing the cord to slip with respect to one of the first and second bone anchors by inserting a closure top into one of the first and second bone anchors, the closure top having an end surface that remains spaced from the sleeve aperture.