This study is designed to generate data relating to patient safety, bone generating activity associated with the use of the rhBMP-2/BCP device as compared to autograft and to evaluate the feasibility of conducting a larger clinical trial in a patient population requiring spinal fusion.

Inclusion Criteria:

• Subject has radiographically documented spinal degeneration with instability as documented by the presence of translation >= 4mm or angulation >= 5°.
• Subject has intractable back pain which does not respond to conservative treatment and in the investigator's opinion, requires surgical spinal fusion.
• Subject's pain is predominantly associated with the back.
• Subject has only one level involvement at L3-L4, L4-L5, or L5-S1.
• Subject is 18 years of age or greater at the time consent is given to participate in the study.
• Subject is willing to comply with the study plan and sign the informed consent.
• Subject is male or a non-pregnant, non-nursing female. All females of child-bearing age must agree to use adequate contraception for a period of no less than 16 weeks following surgery.

Exclusion Criteria:

• Subject has primary spinal diagnosis of a disorder other than spinal degeneration with instability at the involved surgical level.
• Subject has spinal stenosis or condition which requires a full laminectomy procedure.
• Subject has had a previous fusion, discectomy or laminectomy procedure at L3-L4, L4-L5 or L5-S1.
• Subject has received drugs which may interfere with bone metabolism within two weeks prior to the planned date of spinal fusion surgery (e.g., steroids, methotrexate) or has a condition which requires postoperative medications that interfere with fusion (e.g., steroids, nonsteroidal antiinflammatory drugs, or methotrexate).
• Subject has overt or active infection near the operative spinal region.
• Subject has active systemic infection.
• Subject has history of autoimmune disease (Systemic Lupus Erythematosus or Dermatomyositis).
• Subject's history includes hypersensitivity to protein pharmaceuticals (monoclonal antibodies or gamma globulins).
• Subject has received treatment with an investigational therapy within 28 days prior to implantation surgery or such treatment is planned during the 16 weeks following rhBMP-2/BCP implantation.
• The subject requires electrical bone growth stimulation, allograft, or bone substitute as part of treatment.
• Subject has history of endocrine or metabolic disorder known to affect osteogenesis (e.g. Paget's disease, renal osteodystrophy, Ehlers Danlos syndrome, or osteogenesis imperfecta).
• Subject has a known diagnosis of diabetes which requires treatment with medication.
• Subject has received previous radiation therapy at the site to be fused.
• Subject is unwilling to return for required follow-up visits.
• Subject is a prisoner.
• Subject has insufficient bone mass which precludes surgery (e.g., severe osteopenia or osteoporosis).