A Clinical Study to Evaluate Safety and Performance of PEEK-OPTIMA™ HA Enhanced.

Inclusion Criteria: 1. Aged 18 years of age or older. 2. Primary diagnosis of symptomatic degenerative disc disease (DDD) or symptomatic degenerative disc disease (DDD) with spondylolisthesis (Grade 1), or retrolisthesis, at one or two contiguous levels from L2 to S1. 3. Have discogenic back pain. 4. Suitable for transforaminal lumbar interbody fusion (TLIF) surgery. 5. Indicated for surgical treatment with the Keos Lumbar IBFD with autologous bone graft. 6. Completed at least 6 months of conservative non-operative treatment. 7. Female subjects of childbearing age must have a negative pregnancy test. 8. Able to understand this clinical study, co-operate with procedures. 9. Able to give voluntary, written informed consent to participate. Exclusion Criteria: 1. Not undergone previous spinal surgery at the affected disc level(s). 2. Evidence of tumour and/or malignant disease. 3. Known osteoporosis or severe osteopenia. 4. Known rheumatoid arthritis, ankylosing spondylitis or who are immunocompromised. 5. Known allergy to the material used in the instrumentation. 6. Evidence of an active infection. 7. Any conditions outlined as contraindicated in the Instructions for Use. 8. Receiving any drug treatment that may affect bone metabolism. 9. Female subjects who are pregnant or lactating. 10. Current smokers or have stopped smoking less than 6 months ago. 11. Known drug or alcohol abusers. 12. Currently enrolled in a clinical study.