Patent ID: 8100943

Claim:
An apparatus, comprising: an outer body having a collapsed configuration and an expanded configuration, the outer body having a distal portion, a central exterior portion, and a proximal portion disposed sequentially along a longitudinal axis, the central exterior portion configured to be disposed between adjacent spinous processes, the central exterior portion comprising a longitudinal midpoint of an exterior of the outer body; an inner body disposed within an interior area of the outer body, the inner body having an outer surface in slidable contact with an inner surface of the outer body; wherein a length of the outer body is greater in the collapsed configuration than in the expanded configuration, the length being measured along the longitudinal axis and transverse to a direction of expansion; wherein a height of the central exterior portion does not increase as the outer body moves from the collapsed configuration to the expanded configuration, wherein the height of the central exterior portion is measured in the direction of expansion and transverse to the longitudinal axis.