Lateral approach expandable spinal implant and method

Abstract

An expandable interbody fusion device configured for placement into the intradiscal space between vertebral bodies in a lumbar spine from a lateral approach. The device is expanded by the insertion of a plurality of wafers into the device in situ. The length of the device is configured to extend on the vertebral body endplate from pedicle to pedicle and to reside interiorly of the ring apophysis with at least a portion of the device resting on the area of increased bone density at the posterior portion of the endplate between the pedicles.

What is claimed is: 
     
         1 . An expandable interbody fusion device for insertion into the intradiscal space of a lumbar spine to reside at least in part on the area of increased bone density at the posterior portion of the endplate of the vertebral body between a lateral spacing defined as the pedicle-to-pedicle dimension and laterally within the interior of the ring apophysis extending peripherally around the endplate, comprising an elongate device having an upper surface for engaging the endplate of a vertebral body and a lower surface for engaging the endplate of an opposing vertebral body, the upper surface and a lower surface being separable increasingly upon expansion of the device, the device having a length configured to be less than the lateral spacing within the ring apophysis and not less than the pedicle-to-pedicle dimension. 
     
     
         2 . The expandable interbody fusion device of  claim 1 , wherein said device comprises a superior endplate including said upper surface, an inferior endplate including said lower surface and an expansion structure therebetween. 
     
     
         3 . The expandable interbody fusion device of  claim 2 , wherein said expansion structure comprises a plurality of elements stacked between said superior endplate and said inferior endplate. 
     
     
         4 . The expandable interbody fusion device of  claim 3 , wherein said elements each comprise a generally planar wafer. 
     
     
         5 . The expandable interbody fusion device of  claim 4 , wherein said wafers are each configured to be introduced between said superior endplate and said inferior endplate individually consecutively. 
     
     
         6 . The expandable interbody fusion device of  claim 5 , wherein each of said wafers comprises a leading end defining a lifting surface for engaging a trailing end of an earlier introduced wafer so as to displace and lift said earlier introduced wafer in said stack of wafers. 
     
     
         7 . The expandable interbody fusion device of  claim 5 , wherein each of said wafers comprises structure for interlocking said wafers to each other. 
     
     
         8 . The expandable interbody fusion device of  claim 1 , wherein said device comprises a radiopaque marker at least on said upper surface and said lower surface. 
     
     
         9 . The expandable interbody fusion device of  claim 1 , wherein said upper surface and said lower surface each comprises a convex surface along a length of said device. 
     
     
         10 . The expandable interbody fusion device of  claim 9 , wherein said upper surface and said lower surface each comprises a convex surface along a width of said device. 
     
     
         11 . The expandable interbody fusion device of  claim 1 , wherein said upper surface and said lower surface defined a lordotic angle therebetween. 
     
     
         12 . The expandable interbody fusion device of  claim 1 , wherein said device has an unexpanded height between said upper surface and said lower surface and an expanded height therebetween, the expanded height being at least 50% greater than said unexpanded height. 
     
     
         13 . The expandable interbody fusion device of  claim 12 , wherein said device has an unexpanded height of about 8 mm ranging to an expanded height of about 17 mm. 
     
     
         14 . The expandable interbody fusion device of  claim 1 , wherein said device has a length for use in the L1 to L5 region of the lumbar spine ranging from about 31 mm to 48 mm. 
     
     
         15 . The expandable interbody fusion device of  claim 1 , wherein said device has a width ranging from about 14 mm to 20 mm. 
     
     
         16 . The expandable interbody fusion device of  claim 1 , wherein said device has a length of about 37 mm, a width of about 16 mm and unexpanded height of about 8 mm. 
     
     
         17 . A method of inserting an expandable interbody fusion device from the lateral approach into the intradiscal space of the lumbar spine, comprising the steps of:
 providing an access corridor to the spine from the lateral approach;   providing an elongate expandable device having a length less than the lateral width of the vertebral endplate between the peripheral ring apophysis and not less than the pedicle-to pedicle spacing of the vertebral body;   inserting said device into the intradiscal space between opposing vertebral bodies and within the ring apophysis of said endplate with at least a portion of said device residing on the area of endplate increased bone density at the posterior portion of the endplates between the pedicles; and then   expanding the expandable device in situ to increase the height of the intradiscal space and stabilize the spine.   
     
     
         18 . The method of  claim 17 , wherein said elongate expandable device comprises a superior endplate, an inferior endplate and an expansion structure therebetween, and wherein said expansion structure is expanded to increase the height of said device. 
     
     
         19 . The method of  claim 18 , wherein said expansion structure comprises a plurality of elements that are introduced into said device individually consecutively to form a stack of elements between said superior endplate and said inferior endplate. 
     
     
         20 . The method of  claim 18 , wherein the height of said device is increased from an unexpanded height to an expanded height, said expanded height being at least 50% greater than said unexpanded height. 
     
     
         21 . The method of  claim 17 , wherein said device is inserted generally along a transverse center line extending across the lateral width of a vertebral endplate of the lumbar spine. 
     
     
         22 . The method of  claim 21 , wherein said device is positioned to reside within said intradiscal space more posterior than anterior. 
     
     
         23 . The method of  claim 17 , wherein said access corridor is created with the use of intraoperative nerve monitoring instruments. 
     
     
         24 . The method of  claim 23 , wherein said access corridor is created with the use of tissue dilators. 
     
     
         25 . The method of  claim 24 , wherein a retractor having a plurality of blades is used to enlarge the access corridor, and wherein said device is inserted through said retractor. 
     
     
         26 . The method of  claim 24 , wherein a cannula of fixed dimension is placed over a last and largest dilator, and wherein said device is inserted through said cannula. 
     
     
         27 . The method of  claim 17 , wherein a bone filler is inserted into said intradiscal space adjacent said expanded device. 
     
     
         28 . The method of  claim 27 , wherein said bone filler is injected with a graft insertion instrument to inject said filler under pressure to stress load the filler against the vertebral endplates of opposing vertebral bodies communicating with said intradiscal space.