A Comparison of Stryker's Tritanium Posterior Lumbar Cage and PEEK Implant

Inclusion Criteria: * Subject is skeletally mature * Subject has one or more of the following diagnoses: 1. Degenerative Disc Disease (DDD) at one level or two contiguous levels from L2 to S1 a. DDD may include up to Grade 1 spondylolisthesis at the involved level(s) 2. Degenerative Scoliosis for which the interbody fusion device will be used as an adjunct to fusion * Subject has received 6 months of non-operative therapy * Subject understands the conditions of enrollment and is willing to sign and date the Informed Consent * Subject agrees to comply with visit schedule and study assessments * Provision of signed and dated informed consent form * Subject stated willingness to comply with all study procedures and availability for the duration of the study * Subject is in good general health as evidenced by medical history Exclusion Criteria: * Subject is obese (BMI \> 40) * Subject is sensitive to titanium materials * Subject has an active infection at the operative site * Subject has marked local inflammation * Subject has any abnormality present which affects the normal process of bone remodeling including, but not limited to, severe osteoporosis involving the spine, bone absorption, osteopenia, tumors involving the spine, active infection at the site, or certain metabolic disorders affecting osteogenesis * Subject has any mental, trauma, or neuromuscular disorder which would create an unacceptable risk of fixation failure or complications in postoperative care * Subject has any open wounds * Subject is pregnant or plans to become pregnant during the course of the study * Subject has inadequate tissue coverage over the operative site. * Subject has an neuromuscular deficit which places an unsafe load on the device during the healing period * Subject has any condition of senility, mental illness, or substance abuse * Subject has any other medical or surgical condition which would preclude the potential benefit of spinal implant surgery, such as the presence of tumors, congenital abnormalities, elevation of sedimentation rate unexplained by other diseases, elevation of white blood cell count (WBC), or marked left shift in the WBC differential count. * Subject has prior fusion at the levels to be treated * Subject is incarcerated