The aim of this trial is to evaluate if P-15L bone graft (investigational device) is not inferior in effectiveness and safety to local autologous bone (and allograft where necessary) as an extender (control device) when applied in instrumented transforaminal lumbar interbody fusion (TLIF) in subjects with degenerative disc disease (DDD). In addition to the general overall objective, a sub-group analysis will be performed on the high-risk subject population (tobacco use, obesity, diabetes), as previous studies have shown negative effects of smoking, obesity and diabetes on fusion and bone healing, increased peri/postoperative complications, and lower patient-reported outcome scores.

Inclusion Criteria (abbreviated):

Skeletally mature adults between 22 and 80 years old (inclusive);

Back pain with radicular symptoms as evidenced by leg pain, confirmed by history and physical exam;

Oswestry Low Back Pain Disability Questionnaire score of ≥ 35;

Involved disc(s) between L2 and S1;

Exclusion Criteria (abbreviated):

Significant metabolic disease that in the surgeon's opinion might compromise bone growth such as osteoporosis, osteopenia, or osteomalacia;

Active malignancy;

Nondiscogenic source of symptoms (e.g. tumor, etc.);

Multiple level symptomatic degenerative disc disease where more than one level requires fusion;

Previous spinal instrumentation or a previous interbody fusion procedure at the involved level;

More than one level to be fused