Expandable Ring Intervertebral Fusion Device

Abstract

An expandable tube having a substantially semicircular unexpanded shape is inserted into the disc space after the disc material has been removed therefrom. A plurality of expandable lockable rings are passed over this tube in their unexpanded states and positioned along the anterior edge of the endplates. The tube is then expanded, thereby forcing the rings to expand. The rings hold their final expanded configuration via a one-way locking mechanism. Once sufficient distraction is achieved and the rings locked, the tube is collapsed and removed, thereby leaving the expanded, locked rings behind to support the disc space.

We claim: 
     
         1 . A method of distracting a disc space having opposing vertebral endplates, comprising the steps of:
 a) inserting a tube having a throughbore into the disc space,   b) passing a plurality of rings having a one-way locking mechanism over the tube in a first unexpanded state,   c) positioning the plurality of rings along an anterior edge of the endplates,   d) expanding the tube to force the rings to a second expanded locked state,   e) collapsing the expanded tube to leave the locked rings behind to support the disc space, and   f) removing the tube.   
     
     
         2 . The method of  claim 1  wherein each ring in its expanded locked state has a diameter substantially corresponding to a height of the disc space. 
     
     
         3 . The method of  claim 1  wherein each ring in its expanded locked state has a first row of gripping teeth extending outwards for gripping a first vertebral endplate. 
     
     
         4 . The method of  claim 1  wherein each ring in its expanded locked state has a second row of gripping teeth extending outwards for gripping a second vertebral endplate. 
     
     
         5 . The method of  claim 1  wherein the expansion step comprises providing a fluid in the throughbore of the flexible tube. 
     
     
         6 . The method of  claim 1  wherein each ring has a first and second end, the first end having a first mating tooth, the second end having a second mating tooth, wherein the first and second mating teeth mate with each other in the expanded locked state to prevent return of the ring to its unexpanded state. 
     
     
         7 . A method of distracting a disc space having opposed vertebral endplates, comprising the steps of:
 a) inserting a tube into the disc space, the tube carrying a plurality of rings thereon, wherein the rings are in a first unexpanded state and have a one-way locking mechanism,   b) positioning the rings along an anterior edge of the endplates,   c) expanding the tube to force the rings to expand and lock,   d) collapsing the expanded tube to leave behind the rings to support the disc space, and   e) removing the tube.   
     
     
         8 . A method of making an in-situ formed intervertebral fusion cage, comprising the steps of:
 a) inserting an assembly into a disc space, the assembly comprising an expandable balloon having a plurality of expandable rings thereon,   b) expanding the expandable balloon to expand the expandable rings.   
     
     
         9 . A method of making an in-situ formed intervertebral fusion cage, comprising the steps of:
 a) inserting into a disc space a fusion ring in an unexpanded state,   b) expanding the ring to an expanded state.   
     
     
         10 . A method of making an in-situ formed intervertebral fusion cage, comprising the steps of:
 a) inserting into a disc space a spiral-shaped fusion ring having an inner end and a outer end, wherein the ends overlap,   b) expanding the ring so that the first end abuts the second end.   
     
     
         11 . An assembly for inserting an intervertebral fusion device, comprising:
 a) a first flexible tube having an outer radius and a throughbore, a first unexpanded state and a second expanded state,   b) a plurality of bladder rings having a first unexpanded state and a second expanded, locked state,   wherein each bladder ring surrounds the outer radius of the tube and is filled with a curable component,   wherein the plurality of rings are in their unexpanded states when the tube is initially in its unexpanded state, and   wherein the plurality of bladder rings are in their expanded states once the tube has been placed in its expanded state.   
     
     
         12 . An intervertebral fusion device comprising an assembly for inserting an intervertebral fusion device, comprising:
 a) a first flexible tube having an outer radius and a throughbore, a first unexpanded state and a second expanded state,   b) a plurality of expandable rings having a first unexpanded state and a second expanded, locked state, wherein each ring comprises;
 i) upper and lower plates, each plate having an outer surface adapted for gripping a vertebral endplate and an inner surface adapted for bearing against the outer radius of the first flexible tube, and 
 ii) a pair of elongatable struts connecting the upper and lower plates, each strut adapted to resist recession, 
   
       wherein each expandable ring surrounds the outer radius of the tube, 
       wherein the plurality of rings are in their unexpanded states when the tube is initially in its unexpanded state, and 
       wherein the plurality of rings are in their expanded states once the tube has been placed in its expanded state. 
     
     
         13 . An intervertebral fusion device comprising:
 a) first U-shaped component having first and second legs and an intermediate curved region comprising a convex surface and a concave surface,   b) second U-shaped component having first and second legs and an intermediate curved region comprising a convex surface and a concave surface,   
       wherein the concave surfaces oppose each other, and the convex surfaces are adapted for gripping respective opposed vertebral endplates, and 
       wherein the first legs of each component are adapted to nest with each other to form a first keyway, and 
       wherein the second legs of each component are adapted to nest with each other to form a second keyway. 
     
     
         14 . The device of  claim 13  further comprising a securement pin, wherein the first legs of each component further comprise a throughhole, and wherein the securement pin passes through each throughhole. 
     
     
         15 . The device of  claim 13  wherein the first legs of each component further comprise ratchet teeth adapted for one way movement.