Check reins in the form of elongated members are used to limit the extreme range of motion which would otherwise be permitted by some ADR designs. The check reins serve two main purposes. First, they retain disc spacers, if present. Additionally, the wedge shape of ADRs and the removal of the Anterior Longitudinal Ligament (ALL) and a portion of the Annulus Fibrosus (AF) to insert the ADR from an anterior approach, favor anterior extrusion of disc spacers. In preferred embodiments the check reins are therefore limited to the anterior portion of the periphery of the ADR. Second, check reins serve to prevent excessive spinal motion. Again, although they may be helpful in other locations, anterior check reins help restore the motion limiting functions of the ALL and AF that were removed in anterior approaches to the spine.