One exemplary device includes a main body including a shaft having a longitudinal axis; a first clamping mechanism having first and second jaws configured to clamp a spinous process of a first vertebra, and a second clamping mechanism having third and fourth jaws configured to clamp a spinous process of a second vertebra. The first, second, third and fourth jaws extend transversely from the shaft and at least two of two of the jaws are releasably mounted to the shaft and are mountable to and removable from the shaft by relative movement between the respective jaw and the shaft in a direction normal to a longitudinal axis of the shaft.