Within a given spinal segment, the stable vertebral level is identified.
Within the lower lumbar spine, that level is most commonly at the sacrum.
A bone fastener is rigidly affixed to the stable spinal segment and an
interconnecting member is rigidly affixed to the bone fastener so as to
form a cantilever construct. Vertebral bodies that exhibit aberrant
spinal motion and/or mal-alignment relative to the stable segment are
then attached to the interconnecting member using non-rigid bone
fastener(s). The motion profile of the dynamic fastener can be varied and
may be selected to provide the desired vertebral motion characteristics.
The interconnecting member may be rigid or it may be alternatively made
rigid parallel to the direction of greatest instability and non-rigid in
the other planes.