An insertion instrument for a spinal implant, wherein the spinal implant includes: a) an elongated body to function as a spacer placed in a target interspinous process space between two adjacent spinous processes, wherein the body defines an interior and a proximal internal recess for access to the interior, the proximal internal recess forming a transverse groove; b) a distal anchor that is at least partially threaded and has opposing radially deployable blades mounted for rotation about a pin transversely mounted in the interior; c) a proximal anchor including a spike cap mounted to slide along the body and a drive nut mounted for longitudinal movement along the body between a first position spaced apart from the distal anchor and a second position relatively closer to the distal anchor to thereby compress the two adjacent spinous processes between the spike cap and the distal anchor; and d) an actuation plunger slidably inside the interior for moving the blades from a stowed position to an implant deployed position, the insertion device comprising: an elongated main body having a distal locking portion for coupling to the implant and a proximal handle portion, the main body defining a central passage and the distal locking portion having outer ridges and at least one slot to allow at least one of the outer ridges to flex radially inward; a plunger slideably coupled in the central passage for movement between an unlocked position for mounting the implant on the distal locking portion, a locked position for locking the implant on the distal locking portion, and an insertion instrument deployed position for deploying the actuation plunger to move the blades from the stowed position to the deployed position; a spike cap drive rotatably mounted on the main body having a socket end for engaging the drive nut to, in turn, move the spike cap; and a plunger stop coupled to the main body, the plunger stop having a central passage substantially aligned with the central passage of the main body, wherein: the plunger stop has a boss protruding into the central passage; and the plunger forms a three-part groove that captures the boss as the plunger slides and rotates within the central passage, the three-part groove having a first axial part that defines the unlocked position, an intermediate radial part that defines the locked position, and a second axial part that defines the insertion instrument deployed position. an elongated main body having a distal locking portion for coupling to the implant and a proximal handle portion, the main body defining a central passage and the distal locking portion having outer ridges and at least one slot to allow at least one of the outer ridges to flex radially inward; a plunger slideably coupled in the central passage for movement between an unlocked position for mounting the implant on the distal locking portion, a locked position for locking the implant on the distal locking portion, and an insertion instrument deployed position for deploying the actuation plunger to move the blades from the stowed position to the deployed position; a spike cap drive rotatably mounted on the main body having a socket end for engaging the drive nut to, in turn, move the spike cap; and a plunger stop coupled to the main body, the plunger stop having a central passage substantially aligned with the central passage of the main body, wherein: the plunger stop has a boss protruding into the central passage; and the plunger forms a three-part groove that captures the boss as the plunger slides and rotates within the central passage, the three-part groove having a first axial part that defines the unlocked position, an intermediate radial part that defines the locked position, and a second axial part that defines the insertion instrument deployed position. the plunger stop has a boss protruding into the central passage; and the plunger forms a three-part groove that captures the boss as the plunger slides and rotates within the central passage, the three-part groove having a first axial part that defines the unlocked position, an intermediate radial part that defines the locked position, and a second axial part that defines the insertion instrument deployed position.