An implant adapted to traverse an interspinous space and promote fusion of the adjacent spinous processes comprising: a spacer body comprising a first end and a second end, the spacer body comprising at least a superior wall and an inferior wall, the inferior wall separated from the superior wall by an internal space, the superior wall comprising a superior proximal edge and at least one superior protrusion extending from the first end of the superior wall, the inferior wall comprising an inferior proximal edge and at least one inferior protrusion extending from the first end of the superior wall, the spacer body comprising a block including a set of ramps to cooperatively engage a first ramp on the superior wall and a second ramp (296") on the inferior wall, the block movable in the internal space from relatively more proximate the second end to relatively more proximate the first end causing the superior wall to move relative to the inferior wall such that the spacer body changes from a first configuration where the superior wall and the inferior wall are separated by a first distance to a second configuration where the superior wall and the inferior wall are separated by a second distance greater than the first distance; a first extension comprising a medial facing surface adapted to reside adjacent a spinous process and a lateral facing surface, the medial facing surface cooperatively engaging the at least one superior and the at least one inferior protrusion of the spacer body such that at least one of the superior proximal edge or the inferior proximal edge move along the medial facing surface, the medial facing surface comprising a plurality of fasteners extending medially and adapted to engage the adjacent spinous process; and a draw movable laterally and cooperatively engaged to the block to move the block between the second end and the first end of the spacer body, wherein movement of the draw in a first direction causes the spacer body to distract from the first configuration to the second configuration and movement of the draw in a second direction causes the spacer body to compress from the second configuration to the first configuration. a spacer body comprising a first end and a second end, the spacer body comprising at least a superior wall and an inferior wall, the inferior wall separated from the superior wall by an internal space, the superior wall comprising a superior proximal edge and at least one superior protrusion extending from the first end of the superior wall, the inferior wall comprising an inferior proximal edge and at least one inferior protrusion extending from the first end of the superior wall, the spacer body comprising a block including a set of ramps to cooperatively engage a first ramp on the superior wall and a second ramp (296") on the inferior wall, the block movable in the internal space from relatively more proximate the second end to relatively more proximate the first end causing the superior wall to move relative to the inferior wall such that the spacer body changes from a first configuration where the superior wall and the inferior wall are separated by a first distance to a second configuration where the superior wall and the inferior wall are separated by a second distance greater than the first distance; a first extension comprising a medial facing surface adapted to reside adjacent a spinous process and a lateral facing surface, the medial facing surface cooperatively engaging the at least one superior and the at least one inferior protrusion of the spacer body such that at least one of the superior proximal edge or the inferior proximal edge move along the medial facing surface, the medial facing surface comprising a plurality of fasteners extending medially and adapted to engage the adjacent spinous process; and a draw movable laterally and cooperatively engaged to the block to move the block between the second end and the first end of the spacer body, wherein movement of the draw in a first direction causes the spacer body to distract from the first configuration to the second configuration and movement of the draw in a second direction causes the spacer body to compress from the second configuration to the first configuration.