Therapy device with fixated distraction distance

Abstract

Assemblies for implantation across one or more adjacent bones to allow for control of the distance between bone anchors. Control of distance between bone anchors may be provided by one inter-anchor element pushing the pair of bone anchors apart and a second inter-anchor element pulling the pair of bone anchors together. Control of distance between bone anchors may be provided through use of dissimilar thread pitch. Compression of the space between bone anchors through controlled movement of a pair of anchored bone anchors towards one another.

What is claimed is: 
     
         1 . A method for setting a distance between a pair of bone anchors consisting of a proximal bone anchor inserted into a proximal bone and a distal bone anchor inserted into a distal bone, the method comprising:
 rotating a first inter-anchor element threadedly engaged with the proximal bone anchor to set a minimum distance between the pair of bone anchors; and   rotating a second inter-anchor element threadedly engaged with the distal bone anchor to set a maximum distance between the pair of bone anchors with the maximum distance equal to the previously set minimum distance.   
     
     
         2 . The method of  claim 1  wherein the method further comprises:
 rotating the first inter-anchor element threadedly engaged with the proximal bone anchor to set a first distance between the pair of bone anchors before rotating the first inter-anchor element threadedly engaged with the proximal bone anchor to set the minimum distance between the pair of bone anchors; and 
 wherein the step of rotating the second inter-anchor element threadedly engaged with the distal bone anchor to set the maximum distance between the pair of bone anchors equal to the previously set minimum distance pulls the pair of bone anchors towards one another. 
 
     
     
         3 . The method of  claim 2  further comprising inserting material between the pair of bone anchors after setting the first distance between the pair of bone anchors and before reducing a distance between the pair of bone anchors. 
     
     
         4 . The method of  claim 3  wherein the material inserted between the pair of bone anchors is compressed between the distal bone and the proximal bone connected to the pair of bone anchors. 
     
     
         5 . The method of  claim 2  further comprising inserting a device to assist in a process of creating a stable fused space between the pair of bone anchors after setting the first distance between the pair of bone anchors and before reducing a distance between the pair of bone anchors. 
     
     
         6 . The method of  claim 5  wherein the device is inserted through a large port in the first inter-anchor element. 
     
     
         7 . The method of  claim 5  wherein the device is inserted through a path that does not include the first inter-anchor element. 
     
     
         8 . The method of  claim 2  further comprising inserting a distal end of a tool between the pair of bone anchors after setting the first distance between the pair of bone anchors and before reducing a distance between the pair of bone anchors. 
     
     
         9 . The method of  claim 8  wherein the distal end of the tool is inserted through at least one large port in the first inter-anchor element. 
     
     
         10 . The method of  claim 8  wherein the distal end of the tool is inserted through a path that does not include the first inter-anchor element. 
     
     
         11 . The method of  claim 1  wherein the step of rotating the first inter-anchor element threadedly engaged with the proximal bone anchor to set the minimum distance between the pair of bone anchors includes interacting with a proximal end of the proximal anchor to prevent the proximal bone anchor from rotating as the first inter-anchor element is rotated. 
     
     
         12 . The method of  claim 1  wherein the step of rotating the second inter-anchor element threadedly engaged with the distal bone anchor to set the maximum distance between the pair of bone anchors equal to the previously set minimum distance includes monitoring a fluoroscopic image of the distal bone anchor to look for a distal tip of the second inter-anchor element. 
     
     
         13 . The method of  claim 1  wherein the minimum distance is less than an actual distance between the pair of bone anchors before rotating the first inter-anchor element to set the minimum distance between the proximal bone anchor and the distal bone anchor. 
     
     
         14 . A method for controlling a distance between a pair of bone anchors consisting of a distal bone anchor and a proximal bone anchor, the method comprising:
 implanting the distal bone anchor in a distal bone;   implanting the proximal bone anchor in a proximal bone that is adjacent to and proximal to the distal bone;   threadedly advancing distally a first inter-anchor element within the proximal bone anchor to push against the distal bone anchor;   inserting a threaded portion of a second inter-anchor element through a channel within the first inter-anchor element and engaging a threaded bore within the distal bone anchor; and   threadedly advancing the second inter-anchor element to pull the pair of bone anchors together until the distance between the pair of bone anchors is fixed.   
     
     
         15 . A method for setting a distance between a proximal bone anchor anchored in a proximal bone and a distal bone anchor in a distal bone adjacent to the proximal bone; the method comprising rotating a first inter-anchor element threadedly engaged with the proximal bone anchor and the distal bone anchor to use dissimilar thread pitch to set the distance between the proximal bone anchor and the distal bone anchor. 
     
     
         16 . The method of  claim 15  wherein the first inter-anchor element has at least one lateral port in fluid communication with a proximal end of the first inter-anchor element such that material may be delivered between the proximal bone anchor and the distal bone anchor through the at least one lateral port. 
     
     
         17 . The method of  claim 16  further comprising inserting a second inter-anchor element through an interior channel in the first inter-anchor element and creating a threaded engagement with the distal bone anchor. 
     
     
         18 . The method of  claim 15  wherein at least a portion of the first inter-anchor element is made from a material with a Young's Modulus between that of titanium and cancellous bone. 
     
     
         19 . An assembly for implantation across a proximal bone and an adjacent distal bone comprising:
 an externally threaded distal anchor for engagement with the distal bone;   an externally threaded proximal anchor for engagement with the proximal bone;   a spanning component that is threadedly engaged with the proximal anchor and extends into an interior of the distal anchor, wherein the spanning component may be rotated to set a minimum distance between a distal end of the proximal anchor and a proximal end of the distal anchor; and   a compression inducing element adapted to:
 extend into an open interior of the spanning component; 
 engage a shoulder within an interior of the proximal anchor, the shoulder facing a proximal end of the proximal anchor; 
 engage a threaded bore within an interior of the distal anchor; and 
 receive rotational input at a driver engagement section at a proximal end of the compression inducing element accessible via the proximal end of the proximal anchor such that a driver engaged with the driver engagement section of the compression inducing element has a capacity to reduce a distance between the distal anchor and the proximal anchor by pulling the distal anchor towards the proximal anchor. 
   
     
     
         20 . The assembly of  claim 19  wherein the shoulder within the interior of the proximal anchor is part of a component threadedly engaged to the interior of the proximal anchor. 
     
     
         21 . The assembly of  claim 19  wherein a portion of the spanning component extending into the interior of the distal anchor is fluted to reduce contact area between the spanning component and the distal anchor. 
     
     
         22 . The assembly of  claim 19  wherein a portion of the spanning component extending into the interior of the distal anchor is adapted to reduce surface contact between the portion of the spanning component and the interior of the distal anchor. 
     
     
         23 . The assembly of  claim 19  wherein the spanning component has at least one lateral port in fluid communication with a proximal end of the spanning component so that the spanning component may be used as a conduit to deliver material between the distal bone and the proximal bone. 
     
     
         24 . The assembly of  claim 19  wherein the spanning component imposes the minimum distance between the distal anchor and the proximal anchor, the minimum distance selected from a range of different possible minimum distances enabled by a capacity of the spanning component to move via threaded engagement relative to a threaded portion of the interior of the proximal anchor. 
     
     
         25 . The assembly of  claim 24  where the range of different possible minimum distances is broad enough to allow imposition of a hyper-distraction distance between the distal anchor and the proximal anchor to allow delivery of material into a hyper-distracted space between the distal bone and the proximal bone before using the compression inducing element to reduce the distance between the distal anchor and the proximal anchor and thus reduce the distance between the distal bone and the proximal bone. 
     
     
         26 . The assembly of  claim 24  wherein the compression inducing element limits the distance between the distal anchor and the proximal anchor to not exceed the minimum distance imposed by the spanning component. 
     
     
         27 . The assembly of  claim 19  wherein:
 the spanning component has a spanning component driver engagement section at a distal end; 
 the distal anchor has a distal anchor driver engagement section at a proximal end; and 
 the spanning component driver engagement section has a relationship with the distal anchor driver engagement section such that one driver tip could be inserted from the proximal end to simultaneously engage both the spanning component driver engagement section and the distal anchor driver engagement section to allow both to be torqued, and wherein another driver tip could be used to engage the spanning component driver engagement section but not the distal anchor driver engagement section such that the spanning component may be rotated without driving the distal anchor. 
 
     
     
         28 . The assembly of  claim 19  wherein the distal anchor is adapted to engage two adjacent bones, the distal bone and an adjacent more distal bone. 
     
     
         29 . The assembly of  claim 28  where the distal anchor is adapted to distract a space between the distal bone and the more distal bone through use of dissimilar thread pitch. 
     
     
         30 . The assembly of  claim 19  wherein one bone is a portion of a sacrum. 
     
     
         31 . The assembly of  claim 19  wherein the proximal end of the proximal anchor is adapted to engage a counter-torque tube. 
     
     
         32 . An assembly for implantation across two adjacent bones, a proximal bone and a distal bone comprising:
 a distal anchor for engagement with the distal bone;   a proximal anchor for engagement with the proximal bone; and   a distraction inducing element adapted to engage a threaded section within an interior of the proximal anchor and to engage a threaded section within an interior of the distal anchor to form an adjustable but substantially rigid structure such that rotation of the distraction inducing element has a capacity to alter a distance between the distal anchor and the proximal anchor through use of dissimilar thread pitch between a thread pitch for the threaded section within the interior of the proximal anchor and a thread pitch for the threaded section within the interior of the distal anchor.   
     
     
         33 . The assembly of  claim 32  wherein the distraction inducing element has at least one lateral port in fluid communication with a proximal end of the distraction inducing element so that the distraction inducing element may be used as a conduit to deliver material between the distal anchor and the proximal anchor. 
     
     
         34 . An assembly for insertion across a space between a proximal bone and a distal bone, the assembly comprising:
 a distal anchor for threaded engagement with the distal bone;   a proximal anchor for threaded engagement with the proximal bone;   a spanning component with an external thread adapted to engage an internal thread within the proximal anchor so that a distal end of the spanning component can be selectively advanced beyond a distal end of the proximal anchor to limit movement of the distal anchor towards the proximal anchor; and   a compression inducing element with a distal end that passes through a bore in the spanning component and engages a threaded bore in the distal anchor, the compression inducing element having a distal facing shoulder which engages a proximal facing shoulder within the proximal anchor so that rotation of the compression inducing element draws the distal anchor towards the proximal anchor to decrease distraction of a space between the distal bone and the proximal bone by decreasing a distance between the distal anchor and the proximal anchor until limited by the spanning component.