The study is a prospective non-randomized multi-center feasibility clinical trial to establish the safety and efficacy of the Nucel® allograft tissue for use in lumbar interbody fusion procedures.

Two hundred non-randomized subjects will participate in the study at up to ten clinical sites in the United States. Participants will be between 18 and 75 years of age. All subjects will have been established with lumbar spine disease at one or two levels of the lumbar spine that requires lumbar interbody fusion procedure as per the opinion of the treating surgeon. The diseases included in the study are spondylosis, degenerative disc disease and spondylolisthesis. All subjects who meet the inclusion criteria and do not meet the exclusion criteria and who elect to participate and sign the informed consent will be included in the study.

Inclusion Criteria:

1. Be between 18 and 75 years of age
2. Have clinical and/or radiological evidence of stenosis, spondylolisthesis, spondylosis or degenerative disc disease, or at either one or two levels of lumbar spine.
3. In the opinion of the treating surgeon, must already be a qualified candidate for interbody lumbar fusion surgery with supplemental fixation.
4. Be likely to return for regular follow-ups until the end of the study period.
5. Be willing and able to provide Informed Consent for study participation.

Exclusion Criteria:

1. Previous lumbar spine fusion surgery at operative level.
2. Back pain due to acute trauma.
3. Clinical, laboratory and/or radiological evidence of back pain secondary to acute or chronic infection, malignancy, other space occupying lesions and metabolic bone demineralization diseases (e.g. osteomalacia, gout, Paget's disease etc.)
4. No chronic steroid or chronic prescription NSAID use within three (3) months prior to surgery.
5. Any active malignancy, infectious process, or documented chronic autoimmune disease.
6. Any other concurrent medical disease or treatment that might impair normal healing process.
7. Recent history (within past 6 months) of any chemical or alcohol dependence.
8. Morbid obesity (BMI > 40).
9. Currently a prisoner.
10. Currently experiencing a major mental illness (psychosis, schizophrenia, major affective disorder) which may indicate that the symptoms are psychological rather than of physical origin.
11. Pregnancy at the time of enrollment or planned pregnancy, which would interfere with follow-up imaging.