Translational instrumentation for spondylolisthesis and scoliosis reduction

Abstract

An instrument includes a distraction mechanism having a proximal end and an opposed distal end. The distal end includes opposed first and second end members. A first vertebral endplate spreader includes a proximal spreader section mounted to the first end member of the distraction mechanism. The first spreader also includes a distal spreader section operatively connected to the proximal spreader section for lateral movement relative to the proximal spreader section. A second vertebral endplate spreader is mounted to the second end member of the distraction mechanism. The distraction mechanism is configured and adapted to distract the spreaders apart and to retract the spreaders together along a distraction axis. The distal spreader section of the first spreader is configured to move relative to the second spreader in a lateral direction relative to the distraction axis for correction of vertebral alignment, as in treatment of spondylolisthesis, scoliosis, and the like.

What is claimed is: 
     
         1 . A vertebral endplate spreader for a vertebral distraction instrument comprising:
 a proximal spreader section configured to be mounted to an end member of a distraction mechanism; and   a distal spreader section operatively connected to the proximal spreader section for lateral movement relative to the proximal spreader section, wherein the distal spreader section is configured and adapted to engage a vertebra.   
     
     
         2 . A vertebral endplate spreader as recited in  claim 1 , further comprising a pair of guides engaged with the proximal and distal spreader sections to maintain a parallel relationship between the proximal and distal spreader sections during relative lateral travel of the proximal and distal spreader sections. 
     
     
         3 . A vertebral endplate spreader as recited in  claim 2 , wherein the guides are mounted to the distal spreader section and are slideably engaged to the proximal spreader section. 
     
     
         4 . A vertebral endplate spreader as recited in  claim 1 , further comprising a linear actuator engaged with the proximal and distal spreader sections to actuate relative lateral travel of the proximal and distal spreader sections. 
     
     
         5 . A vertebral endplate spreader as recited in  claim 4 , wherein the linear actuator includes a threaded screw engaged to threads in the proximal spreader section, and rotatably engaged with the distal spreader section so rotation of the threaded screw adjusts separation of the proximal and distal spreader sections for relative lateral travel thereof. 
     
     
         6 . A vertebral endplate spreader as recited in  claim 1 , wherein at least one of the proximal and distal spreader sections includes a bone screw passage for accommodating a bone screw to engage the distal spreader section to a vertebra. 
     
     
         7 . A vertebral endplate spreader as recited in  claim 1 , wherein the distal spreader section includes at least one tong for engaging a vertebral endplate. 
     
     
         8 . A method of correcting vertebral alignment comprising:
 engaging a distal spreader section of a first vertebral endplate spreader to a first vertebra;   engaging a second vertebral endplate spreader to a second vertebra proximate to the first vertebra;   distracting the first and second spreaders apart along a distraction axis to distract the first and second vertebrae from one another; and   translating the distal spreader section of the first spreader relative to the second spreader laterally relative to the distraction axis for correction of alignment of the first and second vertebrae.   
     
     
         9 . A method as recited in  claim 8 , wherein the steps of engaging the first and second spreaders to the vertebrae include approaching the vertebrae with the spreaders from an anterior approach. 
     
     
         10 . A method as recited in  claim 9 , wherein the step of translating includes moving the superior of the two vertebrae in a posterior direction to correct a listhesis condition of the vertebrae. 
     
     
         11 . A method as recited in  claim 8 , wherein the step of translating includes moving the superior of the two vertebrae in an anterior direction to correct a retrolisthesis condition of the vertebrae. 
     
     
         12 . A method as recited in  claim 8 , wherein the steps of engaging the first and second spreaders to the vertebrae include approaching the vertebrae with the spreaders from a lateral approach. 
     
     
         13 . A method as recited in  claim 12 , wherein the step of translating includes moving the two vertebrae relative to one another in a lateral direction to correct a lateral slippage condition of the vertebrae related to scoliosis.