Minimally invasive expanding spacer and method
A minimally invasive spacer for positioning between vertebral members. The spacer is adjustable between a first orientation having a reduced size to facilitate insertion between the vertebral members. A second orientation has an enlarged size for contacting the vertebral members. The spacer includes linkages that are attached to a pair of plates. A pull arm is operatively connected to the linkages for adjusting the spacer from the first orientation to the second orientation. A indicator gauge indicates the height of the spacer.
1. A device to space vertebral members comprising:
first and second linkages each including first and second ends;
a pull arm pivotally connected to the first end of each of the first and second linkages;
a plate connected to the second end of each of the first and second linkages;
an elongated delivery device that extends around the pull arm and includes:
a first section that extends around a distal section of the pull arm;
a second section disposed proximally of the first section;
an intermediate section positioned between the first and second sections and engaged with a distal portion of the second section;
the first section and the intermediate section being movable relative to the pull arm;
the first, second, and intermediate sections being distinct from each other and distinct from the pull arm;
a handle mounted to the intermediate section and configured to rotate the intermediate section relative to the second section to adjust a spacing between the first and second sections and adjust a height of the device, the handle including a plurality of markings disposed at corresponding circumferential positions that extend around the handle and indicate the height of the device, each of the markings indicating an equal incremental change in the height of the spacer with each subsequent one of the markings being positioned a greater rotational distance away from an adjacent previous one of the markings;
an indicator positioned on the second section adjacent to the markings;
the handle configured to rotate a first rotational distance to align a first one of the markings with the indicator to indicate a first height when the pull arm is at a first position for which the second ends of the linkages are spaced a first distance from the pull arm and the plate assumes a first angle relative to the pull arm;
the handle configured to rotate a greater second rotational distance to align a second one of the markings with the indicator to indicate a second height when the pull arm is at a second position for which the second ends of the linkages are spaced a second and greater distance from the pull arm than the first distance and the plate assumes a second angle relative to the pull arm greater than the first angle;
the handle configured to rotate a third rotational distance that is greater than either of the first and second rotational distances to align a third one of the markings with the indicator to indicate a third height when the pull arm is at a third position for which the second ends of the linkages are spaced a third and greater distance from the pull arm than the second distance and the plate assumes a third angle relative to the pull arm greater than the third angle;
a difference between the first and second heights being equal to a difference between the second and third heights;
wherein movement of the second section away from the first section moves the pull arm from the first position to the second position and from the second position to the third position.
2. The device of claim 1 , wherein the second linkage includes a different length than the first linkage.
3. The device of claim 1 , wherein teeth are positioned at the second ends of the first and second linkages, with the second end of the first linkage mating with the second end of the second linkage.
4. The device of claim 1 , wherein the markings include multiple rows of indicia that each extend around the circumference of the handle.
5. The device of claim 1 wherein the intermediate section is hollow with a longitudinal bore and a substantially cylindrical outer surface; wherein the longitudinal bore of the intermediate section is collinear with the pull arm.
6. The device of claim 1 wherein the second section is connected to a distal portion of the pull arm so as to be repeatably removable therefrom.
7. The device of claim 1 wherein the pull arm extends along a longitudinal axis of the delivery device; wherein the intermediate section and the second section extend substantially equally normal to the longitudinal axis in all directions.