Long-term follow up data on the efficacy of the Brantigan Interbody fusion cage, Ray Threaded Fusion cage, and Bagby and Kuslich cages are limited, with the most rigorous studies (i.e. controlled prospective studies) typically providing outcomes approximately 2 years post-surgery. Overall, these studies show that, while existing intervertebral cages have made significant advances in terms of addressing the disadvantages associated with traditional bone grafting/fixation techniques, problems continue to persist. Through comprehensive and accurate clinical evaluation of the Trabecular Metal™ intervertebral cage, the Research Team hopes to document advances in the PLIF technique, thereby informing current research as well as clinical practice.