Spinal motion preservation assemblies adapted for use in a spinal motion segment are disclosed including the process for delivering and assembling the spinal motion preservation assemblies in the spinal motion segment via an axial channel created with a trans-sacral approach. The spinal motion preservation assemblies make use of a dual pivot. A number of different embodiments of spinal motion preservation assemblies are disclosed which include at least one component adapted for elastic deformation under compressive loads. The disclosed mobility preservation assemblies provide for dynamic stabilization (DS) of the spinal motion segment.