The goal of this clinical trial is to assess the safety and effectiveness of the study device, CORUS-LX, as an adjunct to lumbar interbody fusion, when used in combination with pedicle screw and rod constructs for the treatment of lumbosacral degenerative disease in patients requiring 2 level (L4-S1) lumbar fusion, for the treatment of symptomatic degenerative lumbosacral disc disease. The main questions it aims to answer are:

Is there fusion success at the treated posterior anatomy of each level? Is there an absence of major adverse device related events? Is there an absence of injections (steroid, facet joint, nerve block) or subsequent revision surgery at index levels for symptoms related to back or leg pain?

Researchers will compare a control arm to the treatment arm to see if research results vary from standard minimally invasive supplemental posterior fusion.

Eligible participants will undergo one of the below interventions:

• Two-level lumbar interbody fusion at L4-L5 & L5-S1 segments, with supplemental posterior fusion performed using the study device, including pedicle screw and rod fixation.
• Two-level lumbar interbody fusion at L4-L5 & L5-S1 segments, with standard minimally invasive supplemental posterior fusion including pedicle screw and rod fixation.

Participants will also be asked to read, understand, and sign the informed consent, attend a Screening/Baseline visit, undergo surgery for their designated intervention, and participate in 5 additional study visits where they will complete surveys for patient reported outcomes and SOC procedures. These visits will occur at the below intervals (based upon surgery day as day 0):

• 6 weeks
• 3 months
• 6 months
• 12 months
• 24 months

The study device is designed to provide surgeons a tissue-sparing solution for both preparing a fusion bed around the facet space in addition to stabilizing the joint in sync with percutaneous pedicle screw and rod fixation. There have been few rigorous studies looking at the posterior fusion aspect of circumferential lumbar fusion. Through a randomized controlled trial design and multi-modal imaging protocol, we aim to explore whether the opportunity for improved outcomes exists.

This randomized controlled trial was designed to compare outcomes in subjects treated with interbody fusion including supplemental posterior fusion for the treatment of degenerative lumbosacral disease. For the control arm subjects, supplemental posterior fusion will be performed with each surgeon's standard protocol for fusion with pedicle screw and rods. Treatment arm subjects will also receive percutaneous pedicle screw fixation but will also have the posterior anatomy prepared for fusion using the study device. In both arms, all posterior instrumentation will be placed using navigation technology. Study success will be defined as the demonstration of statistical superiority by the treatment arm over the control arm with respect to the primary endpoint, which is the incidence of arthrodesis achieved across the posterior anatomy. Additional data of interest will be collected to explore relationships between observed arthrodesis rates at the posterior anatomy and the rates of arthrodesis across the interbody space, serious device-related adverse events, device failure, subsequent surgical revisions, patient-reported outcomes, and return-to-work measures assessed through 24 months. Eligible subjects will be those with degenerative lumbosacral disease diagnosed at 2 levels between the L4 and S1 segments who are indicated for treatment using an interbody fusion approach supplemented with posterior fusion including pedicle screw and rod fixation. Major exclusionary factors will be history of prior instrumentation at the index or adjacent levels, fused facet or facet hypertrophy that prohibits device implantation, and a diagnosis of osteoporosis.

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.

Specific IPD will be shared on a case-by-case basis after review of proposals by the Sponsor and Investigators.

Participants will be masked to their assignment through the day of surgery, however will be informed of what treatment they received once the surgery is completed.