Spacer ring 12 and/or locking implant 14 can be made from either cortical or cancellous bone or, alternately, from any biocompatible material having the requisite strength requirements including ceramics, polymers, composites, metals such as stainless steel, titanium, etc. [0022] In one embodiment, spacer ring 12 includes a generally C-shaped body 16 having upper and lower vertebral surfaces 18 an