This study is being conducted to evaluate the clinical and radiographic outcomes of three different interbody implant types when used with cancellous allograft chips with BMA or cellular allograft in patients undergoing XLIF surgery. The study will evaluate success by comparing the rate of fusion, complications profile, and any relationships between clinical outcomes (pain and function) and radiographic outcomes (fusion rate) between the three implant groups.

This study is a prospective, non-concurrent, multicenter study to compare the clinical and radiographic outcomes of smooth PEEK, 3D-printed titanium, and Porous PEEK interbody implants when used with cancellous allograft chips with BMA or cellular allograft in subjects who undergo XLIF surgery at one or two levels. To minimize selection bias, all consecutive patients at a given site who meet eligibility requirements will be asked to consent to participate in the study. These patients will present with degenerative conditions in the lumbar spine that are amenable to surgical treatment and will be screened prior to study enrollment. Once enrolled into the study, subjects will undergo their XLIF operation using one of the 3 previously noted interbody implants based on a non-concurrent enrollment schedule. The bone graft material used inside the interbody implant will be randomly assigned between cancellous allograft chips with BMA or cellular allograft prior to surgery based on surgeon investigators' equipoise for the effectiveness of both bone graft materials. Subjects will be followed for 24 months following surgery to determine the number of study subjects that are solidly fused at or before 24 months postoperatively.

Inclusion Criteria:

1. Male and female patients who are 18-80 years of age;

2. Planned interbody fusion surgery, including at least one level of extreme lateral interbody fusion (XLIF) prior to enrollment in the research at one or two consecutive lumbar levels for degenerative disc disease, including those with up to Grade 2 spondylolisthesis, with one of the following NuVasive, Inc. interbody implants:

   1. Coroent® XL PEEK interbody implant; or
   2. Modulus® 3D-printed titanium interbody implant; or
   3. Cohere® XLIF Porous PEEKTM interbody implant.

   If a transforaminal lumbar interbody fusion or anterior lumbar interbody fusion (TLIF or ALIF) is planned adjacent to the XLIF level, the same NuVasive, Inc. interbody implant material type must be used as determined by the implant enrollment schedule. For example:

   1. Smooth PEEK: Coroent XL PEEK (XLIF) + Coroent L (TLIF) or Coroent XLR (ALIF) or Brigade (ALIF)
   2. 3D-printed titanium: Modulus XLIF + Modulus TLIF or Modulus ALIF
   3. Porous PEEK: Cohere XLIF + Coalesce TLIF (currently no ALIF option)

3. The planned procedure must include placement of bilateral posterior screw fixation with or without intrafacet fusion using autograft (with or without the assigned allograft used at the XLIF level(s)) at the treated level(s). Direct posterior decompression at the index interbody fusion level(s) is acceptable.

4. Preoperative coronal Cobb angle of < 10°;

5. Able to undergo surgery based on physical exam, medical history, and surgeon judgment;

6. Understands the conditions of enrollment and willing to sign an informed consent to participate in the evaluation.

Exclusion Criteria:

1. Use of BMP, synthetic bone graft substitutes, allografts, or any other graft material in the interbody or intrafacet spaces other than those under study;
2. Posterior grafting other than the allowed intrafacet fusion at the treated level(s);
3. Revision of prior fusion at treated level(s) (adjacent level interbody fusion is acceptable);
4. XLIF procedure that requires or results in the release of the anterior longitudinal ligament or posterior osteotomy;
5. Preoperative coronal Cobb angle of ≥ 10°;
6. Procedures performed with XLIF interbody implants with integrated vertebral body screw(s);
7. Active smoking six (6) weeks prior to surgery;
8. Systemic or local infection (active or latent);
9. Diseases that significantly inhibit bone healing (e.g., prior diagnosis of osteoporosis, metabolic bone disease, uncontrolled diabetes, dialysis dependent renal failure, symptomatic liver disease);
10. Rheumatoid arthritis or other autoimmune disease that, in the option of the investigator, would interfere with bone healing and/or fusion;
11. Treatment with pharmaceuticals interfering with calcium metabolism;
12. Undergoing chemotherapy or radiation treatment or chronic use of steroids (defined as more than 6 weeks of steroid use within 12 months of surgery or anytime postoperatively, other than episodic use or inhaled corticosteroids);
13. Use of bone stimulators postoperatively;
14. Non-ambulatory, wheelchair-bound;
15. Involvement in active litigation relating to the spine (worker's compensation claim is allowed if it is not contested);
16. Significant general illness (e.g., HIV, active metastatic cancer of any type, uncontrolled diabetes, dialysis dependent renal failure, symptomatic liver disease);
17. Spinal metastases or active spinal tumor malignancy;
18. Immunocompromised or is being treated with immunosuppressive agents;
19. Pregnant, or plans to become pregnant during the study;
20. Mental or physical condition that would limit the ability to comply with study requirements;
21. Prisoners;
22. Participating in another clinical study that would confound study data.

Male and female patients who are 18-80 years of age with planned extreme lateral interbody fusion (XLIF) surgery prior to enrollment in the research at one or two lumbar levels for the treatment of degenerative disc disease, including those with up to Grade 2 spondylolisthesis.