System and method for segmentally modular spinal plating

Abstract

A modular implant for stabilizing the relative motion of spinal vertebrae comprises at least two pairs of plates which connect to two adjacent spinous processes, a spacer configured to be positioned between the spinous processes, and a fastener which pivotably connects to the plates and the spacer. The spacer is interchangeable and may comprise a variety of materials, each providing a different level of elasticity to the spinous processes. Relative motion between vertebrae can also be controlled by varying the surface configuration of the plates and by varying threading of the fastener. Several implants may be linked to provide stabilization across multiple vertebral levels, and the relative motion provided at each vertebral level may differ. A method for revising the implant is provided which comprises accessing the implant and replacing the spacer.

1 . An implantable modular device for stabilizing relative motion of spinal vertebrae, comprising:
 a first pair of plates attachable to a first spinous process;   a second pair of plates attachable to a second spinous process;   a first spacing member comprising an inner end and an outer end, wherein the first spacing member is positionable to fit between the first and second spinous processes to provide a selected level of stiffness between the spinous processes, the first spacing member comprising a first bearing surface and a second bearing surface orthogonal to the first bearing surface, the first bearing surface positionable to contact an inferior surface of the first spinous process and a superior surface of the second spinous process, the second bearing surface shaped as a continuous annulus, the second bearing surface positionable to directly contact a lateral surface of the first spinous process and an ipsilateral surface of the second spinous process;   a cap member configured to engage the inner end of the first spacing member, wherein the cap member comprises a third bearing surface shaped as a continuous annulus, the third bearing surface positionable to directly contact a lateral surface of the first spinous process and an ipsilateral surface of the second spinous process, the third bearing surface on the alternate side of the first spinous process from the second bearing surface; and   a fastener joining the first spacing member and the first and second pairs of plates, the fastener comprising a head and a shaft, the shaft having a first end and a second end and a longitudinal axis extending therebetween,   wherein the first and second pairs of plates are rotatably attachable together at any of a variety of relative orientations in response to securement of the fastener to the first and second pairs of plates to permit further relative rotation between the pairs of plates, thereby permitting dynamic relative motion between the first and second spinous processes.   
     
     
         2 . The device of  claim 1 , wherein the first spacing member is positioned transverse to the first and second pair of plates, the first spacing member having an axis extending in a medial lateral direction, wherein the first spacing member is interchangeable with a different spacing member to permit variation in the stiffness between the spinous processes, wherein each spacing member comprises a material chosen from the group consisting of biocompatible polymers, metals, natural tissues, and synthetic tissues. 
     
     
         3 . The device of  claim 1 , further comprising:
 a third pair of plates attachable to the second spinous process via an attachment mechanism that also attaches the second pair of plates to the second spinous process;   a fourth pair of plates attachable to a third spinous process;   a second spacing member configured to fit between the second and third spinous processes to provide a selected level of stiffness between the spinous processes; and   at least one additional fastener joining the second spacing member to the third and fourth pairs of plates.   
     
     
         4 . The device of  claim 1 , wherein the cap member further comprises a concavity configured to engage the inner end of the first spacing member. 
     
     
         5 . The device of  claim 4 , wherein the cap member further comprises a cap bore extending through the cap member, the cap bore configured to slidably receive the fastener. 
     
     
         6 . The device of  claim 1 , wherein the first and second pairs of plates are further configured to be rigidly attached together at any of the variety of relative orientations in response to securement of the fastener to the first and second pairs of plates to substantially prevent further relative rotation between the pairs of plates, thereby keeping the first and second spinous processes at a substantially fixed relative displacement. 
     
     
         7 . The device of  claim 1 , wherein the first pair of plates are substantially planar and the second pair of plates are substantially non-planar. 
     
     
         8 . The device of  claim 1 , wherein the fastener comprises a longitudinal axis extending in a medial lateral direction and positioned transverse to the first and second pair of plates, wherein the fastener shaft is threaded and the outermost one of the second pair of plates comprises a threaded bore, the threaded fastener shaft threadibly engaging the threaded bore to axially draw the first pair of plates, the second pair of plates and the spacer together along the longitudinal axis of the fastener shaft. 
     
     
         9 . An implantable modular device for stabilizing relative motion of spinal vertebrae, comprising:
 a first pair of plates attachable to a first spinous process immediately adjacent a second spinous process, the first pair of plates comprising a first plate and a second plate;   a second pair of plates attachable to the second spinous process, the second pair of plates comprising a third plate and a fourth plate;   a first fastener having a shaft with a longitudinal axis, the shaft extending through the first and second pairs of plates;   and a spacing member positionable to fit between the first and second spinous processes wherein the spacing member comprises an inner end and an outer end and a first flange positioned toward the outer end, the first flange shaped as a continuous annulus, the first flange positionable to directly contact a lateral surface of the first spinous process and an ipsilateral surface of the second spinous process.   
     
     
         10 . The device of  claim 9 , further comprising a second fastener comprising a shaft, the shaft configured to pass through the first and second plates, wherein the shaft comprises a threaded portion and the second plate comprises a bore with threads, wherein the threaded portion of the shaft is directly engageable with the second plate bore threads to axially draw the first and second plates together. 
     
     
         11 . The device of  claim 10 , further comprising a third fastener, the third fastener configured to pass through the third and fourth plates. 
     
     
         12 . The device of  claim 9 , further comprising a spacing member bore, wherein the first fastener passes through the spacing member bore. 
     
     
         13 . The device of  claim 12 , further comprising a cap member configured to engage the inner end of the first spacing member, wherein the cap member comprises a second flange shaped as a continuous annulus, the second flange positionable to directly contact a lateral surface of the first spinous process and an ipsilateral surface of the second spinous process, the second flange on the alternate side of the first spinous process from the first flange. 
     
     
         14 . The device of  claim 9 , wherein at least one of the first and second pairs of plates is substantially non-planar. 
     
     
         15 . The device of  claim 9 , wherein at least one of the first and second plates further comprises a first interface surface comprising a plurality of ridges, and at least one of the third and fourth plates further comprises a second interface surface comprising a plurality of ridges, wherein the ridges of the first interface surface are directly engageable with the ridges of the second interface surface to lock the first and second pairs of plates together at any of the variety of relative orientations. 
     
     
         16 . An implantable modular device for providing dynamic relative motion of spinal vertebrae, comprising:
 a first pair of plates attachable to a first spinous process, the first pair of plates comprising a first plate and a second plate;   a second pair of plates attachable to a second spinous process, the second pair of plates comprising a third plate and a fourth plate;   a first spacing member positioned transverse to the first and second pair of plates, the first spacing member with an axis extending in a medial lateral direction, the first spacing member comprising an inner end and an outer end, the first spacing member further comprising a first bearing surface, the first spacing member configured to fit between the first and second spinous processes to provide a selected level of stiffness between the spinous processes, and   a fastener formed separately from the first spacing member, the fastener having a shaft and a fastener axis and extending through the first plate, the third plate, the spacing member, the fourth plate, and the second plate in sequence,   wherein the first spacing member further comprises a locking feature, wherein the locking feature is lockable with one of the first and second pairs of plates to lock the first spacing member to one of the first and second pairs of plates.   
     
     
         17 . The device of  claim 16 , wherein at least one of the first and second plates further comprises a first interface surface, and at least one of the third and fourth plates further comprises a second interface surface, wherein the first interface surface is in slidable contact with the second interface surface when the first pair of plates is in direct engagement with the second pair of plates. 
     
     
         18 . The device of  claim 16 , wherein the first bearing surface is configured to contact an inferior surface of the first spinous process and a superior surface of the second spinous process; and wherein the first spacing member further comprises a second bearing surface, the second bearing surface shaped as a continuous annulus, the second bearing surface configured to directly contact a lateral surface of the first spinous process and an ipsilateral surface of the second spinous process. 
     
     
         19 . The device of  claim 18 , wherein the first spacing member further comprises a cap member configured to engage the inner end of the first spacing member, wherein the cap member comprises a third bearing surface, the third bearing surface shaped as a continuous annulus, the third bearing surface positionable to directly contact a lateral surface of the first spinous process and an ipsilateral surface of the second spinous process, the third bearing surface on the alternate side of the first spinous process from the second bearing surface. 
     
     
         20 . The device of  claim 16 , wherein the first spacing member is elastically compliant and configured to provide resilient force to stabilize the dynamic relative motion.