The objective of this retrospective study is an investigational clinical follow-up, of patients treated with interbody fusion devices (IBFD), both expandable (EXP) and static (STC), according to their intended use and cleared labeling to understand IBFD design and technique characteristics that affect occurrence rates of subsidence.

Patients treated with IBFD's (both EXP and STC) according to their intended use and cleared labeling

1. EXP IBFD's that expand in width and height demonstrate reduced occurrence of subsidence post-operatively when compared to EXP IBFD's that expand in height only and STC IBFD's.
2. EXP IBFD's that are comprised of multi-material composition with Polyetheretherketone (PEEK) endplate contacting surfaces demonstrate reduced occurrence of subsidence on post-operative radiographs when compared to EXP and STC IBFD's that are primarily comprised of Ti with Ti endplate contacting surfaces.
3. achieve radiographic fusion at a rate consistent with the state-of-the-art
4. achieve significant improvements in pain and function compared to baseline
5. experience adverse events at a frequency comparable to reported rates for TLIF or PLIF surgery
6. not demonstrate any intraoperative complications during the implant process
7. operative approach does not correlate with increased rates of subsidence

Inclusion Criteria:

1. The patient was treated with TLIF or PLIF surgery using the IBFD according to the cleared labeling, based on the surgeon's clinical judgment and patient-specific decision making. Based on the product labeling, the patient must:

1. Was at least 18 years of age and skeletally mature at the time of surgery
2. Had clinical and radiological evidence of DDD of the lumbar spine
3. Undergone treatment with the IBFD with autogenous bone graft and/or allogeneic bone graft composed of cancellous and/or corticocancellous bone at 1 or 2 contiguous levels from L2 to S1

Exclusion Criteria:

1. History of fusion surgery or large laminectomy at L2 to S1 prior to treatment with the IBFD(s) Spondylolisthesis unable to be reduced to grade 1 as part of the surgical procedure
2. Surgery with the IBFD(s) at more than 2 contiguous levels
3. Surgery with the IBFD(s) at levels outside the range of L2 to S1
4. Treated with any bone grafting material other than autogenous or allogenic bone graft in the device(s) or surrounding disc space
5. Any contraindications listed in the cleared product labeling
6. Osteoporosis, Other Systemic Bone D.O. T score ≤ -1.5
7. BMI > 40
8. Systemic Infection
9. H/O IV Drug Use
10. Cancer

Skeletally mature individuals with degenerative disc disease (DDD) of the lumbar spine at one or two contiguous levels from L2 to S1, who were treated with TLIF or PLIF surgery using an EXP or STC IBFD according to the surgeon's and patient's choice, as part of the standard of care.