Lumbar Fusion With Nanotube Versus Titanium Cage

Inclusion Criteria: * Subject is scheduled to undergo 1- or 2-level TLIF with the principal investigator. * Subject has failed nonoperative management for a minimum of 3 months prior to enrollment. * Diagnosis is degenerative disc disease (DDD), defined as discogenic back pain with disc degeneration confirmed by history and radiographic studies, at 1 or 2 contiguous spinal levels from L2 to S1. Subjects may have up to grade 1-2 spondylolisthesis or retrolisthesis at the index level(s). * Subject is able to provide written informed consent. * Subject is, in the investigator's opinion, psychosocially, mentally, and physically able to comply with the protocol, required follow-up visits, and completion of required study forms. Exclusion Criteria: * Prior lumbar arthrodesis surgery at any level. * Diagnosis of osteoporosis (T-score = -2.5) or severe osteopenia (T-score = -2.0 with fragility fracture history). * Body mass index (BMI) greater than 40 kg/m². * Requirement for additional bone grafting materials beyond milled local autograft bone (e.g., rhBMP-2, iliac crest autograft, allograft structural spacers). * Active local or systemic infection. * Known metal sensitivity or foreign body reaction to titanium or PEEK. * Active malignancy or history of spinal malignancy. * Known diabetes mellitus with preoperative HbA1c =8%, confirmed within 90 days of the planned surgery date. Diabetic patients with HbA1c \<8% are eligible following standard preoperative medical optimization. * Condition requiring medications known to interfere with bone healing (chronic oral or parenteral glucocorticoids, immunosuppressives, bisphosphonates initiated within 3 months of surgery, methotrexate, or similar agents). * Inadequate tissue coverage over the operative site or open wound at the operative area. * Pregnancy or planned pregnancy within the next 12 months, or currently lactating. * Current involvement in litigation or receipt of Worker's Compensation related to back or leg pain. * Current enrollment in another investigational drug or device study that could confound study data. * History (present or past) of substance abuse that, in the investigator's opinion, would interfere with protocol adherence or follow-up completion. * Any medical condition or extenuating circumstance that, in the opinion of the investigator, would preclude safe participation in the study. * Subject is a prisoner.