A fin retention and deployment mechanism includes a detent in each of a plurality of fins, a mechanism that engages the detent, and at least one spring clip that maintains each of the fins in a non-deployed position. The controller controls dimming of a light source according to the rectified voltage if the rectified voltage comes from the TRIAC dimmer. Upon insertion into the disc space, a drive screw or similar mechanism can be actuated to drive expansion blocks closer together, which causes flexure members to deflect, resulting in expansion of the structural members and distraction of the end plates.