The present invention provides spinous process implant and associated methods. In one aspect of the invention the implant limits the maximum spacing between the spinous processes. In another aspect of the invention, a spacer has at least one transverse opening to facilitate tissue in-growth. In another aspect of the invention, an implant includes a spacer and separate extensions engageable with the spacer. The spacer is provided in a variety of lengths and superior to inferior surface spacings. In another aspect of the invention, an implant includes a spacer and a cerclage element offset from the midline of the spacer in use so that the spacer defines a fulcrum and the cerclage element is operative to impart a moment to the vertebrae about the spacer. In another aspect of the invention, instrumentation for inserting the implant is provided. In other aspects of the invention, methods for treating spine disease are provided.