Post-market Safety and Effectiveness of the CORUS-LX System in Improving Lumbar Interbody Fusion Outcomes (ILIF)

Inclusion Criteria: 1. Age 18-80 years (Skeletally Mature) 2. Indicated for lumbar interbody fusion for treatment of degenerative lumbosacral disease at two contiguous disc levels between L4-S1 as determined by the following: a) Diagnosis of radiculopathy of the lumbar spine, with pain, including at least one of the following: i) Leg and/or buttock pain, weakness, numbness, or paresthesia ii) Low back pain iii) Neurogenic claudication b) Radiographically determined pathology (CT, MRI, X-rays) at the levels to be treated correlating to primary symptoms including at least one of the following: i) Decreased disc height in comparison to a normal adjacent disc. ii) Degenerative instability ≤ grade 1 spondylolisthesis (\<25% slip). iii) Recurrent disc herniation. iv) Central and/or foraminal stenosis. 3. Oswestry Disability Index Score of \> 40/100 (Severe Disability). 4. Unresponsive to non-operative, conservative treatment (rest, heat, electrotherapy, physical therapy, chiropractic care and/or analgesics) for: 1. At least six weeks from symptom onset; or 2. Have the presence of progressive symptoms or signs of nerve root/ spinal cord compression despite continued non-operative conservative treatment. 5. Reported to be medically cleared for surgery. 6. Physically and mentally able and willing to comply with the Protocol, including the ability to read and complete required forms 7. Willing and able to adhere to the scheduled follow-up visits and requirements of the Protocol. 8. Written informed consent provided by subject. Exclusion Criteria: 1. Any disease or condition that, in the investigator's opinion, would preclude accurate radiographic evaluation of any treated vertebrae (e.g. morbid obesity). 2. Any anatomy or condition that makes posterior fusion treatment infeasible (e.g. fused facets). 3. Has, in the Investigator's opinion, any disease or condition that would preclude accurate clinical evaluation (e.g. neuromuscular disorders). 4. Active systemic infection or infection at the operative site. 5. Anticipated treatment for active systemic infection, including HIV or Hepatitis C. 6. Previous trauma to any of the L3 to S1 levels resulting in significant bony or disco-ligamentous lumbar spine injury that may prevent device placements. 7. Prior instrumented surgery or pseudoarthrosis at the operative or adjacent levels. 8. Indicated for or history of laminectomy at any of the index or adjacent levels 9. Fixed or permanent neurologic deficit related to the target treatment levels that cannot be improved with surgery 10. Leg, buttocks, or back pain in the absence of other symptoms of radiculopathy or myeloradiculopathy justifying the need for surgical intervention. 11. Symptomatic disc degeneration requiring surgical intervention at more or less than two levels. 12. Diagnosis of spondylolisthesis, grade \>1. 13. Diagnosis of lytic spondylolisthesis 14. Diagnosis of iatrogenic, traumatic, or dysplastic spondylolisthesis 15. Congenital bony and/or spinal cord abnormalities affecting spinal stability. 16. Diagnosis of Paget's disease, osteomalacia or any other metabolic bone disease other than osteopenia. 17. Diagnosis of osteoporosis, defined as a previous DEXA bone density T-score of ≤-2.5. 18. Active malignancy or a history of any invasive malignancy (except non-melanoma skin cancer), unless treated with curative intent and without clinical signs or symptoms of the malignancy for at least five years. 19. Has an uncontrolled seizure disorder. 20. Cauda equina syndrome or neurogenic bowel/bladder dysfunction; 21. Use of epidural steroids within 14 days prior to surgery. 22. A concomitant condition requiring daily, high-dose oral steroids. High dose steroid use is defined as: 1. Daily, chronic use of oral steroids of 5 mg/day or greater (steroid inhalers are not exclusionary). 2. Use of short-term (less than 10 days) oral steroids at a daily dose greater than 40 mg within one month of the study procedure. 23. Long-term use (\>6 months) of opioids \>120 mg morphine equivalents. 24. Known allergy to titanium (Ti) 25. A current or recent history (≤1 year prior to screening) of substance abuse that required medical treatment. 26. Is pregnant, nursing, or interested in becoming pregnant within the next 3 years from the time of screening. 27. Participation as a subject in any other clinical studies involving medical devices or drugs in the last 30 days prior to surgery 28. A pending personal litigation relating to spinal injury (worker's compensation is not exclusionary). 29. Anticipated or potential relocation greater than 50 miles that may interfere with completion of follow-up examinations. 30. A mental illness or belongs to a vulnerable population, as determined by the investigator (e.g., prisoner or developmentally disabled), that would compromise ability to provide informed consent or compliance with follow-up requirements.