An interspinous implant includes a spacer having an upwardly facing concave saddle and a downwardly facing concave saddle. The lateral sides of the implant are pulled inward to force the saddles vertically away from each other, thereby increasing the effective height of the implant. In one version, a strap extends circumferentially around the anterior and posterior surfaces of the spacer, such that tightening the strap causes the saddles to move away from each other. In another version, the spacer includes a first outwardly facing convex segment disposed on a first lateral side of the saddles and a second outwardly facing convex segment disposed on a second lateral side of the saddles. A rod extends between the first and second convex segments and is fixed to the first convex segment and movable relative to the second convex segment.
