The human spine is a mechanically complex system of joints crucial for stable posture and movement. The ultimate goal of a vertebral body replacement following a spinal injury that necessitates such a procedure is to have the replacement strut fully incorporate into the spine. This incorporation process is known as bony "fusion", which facilitates the restoration of stability. Bone graft and metallic implants have been used for vertebral body replacement procedures. Both methods have been associated with failure of fusion and recurrence of instability. The development and rationale of the mechanical testing procedures implemented to best differentiate the stability afforded by bone graft versus expandable titanium cage is presented.