Clinician directed use of bone morphogenetic proteins (BMPs) in ways other than FDA approved, has increased recently due to the morbidity associated with harvest of iliac crest bone graft in spinal arthrodesis procedures. FDA approved for the use in anterior lumbar fusions with LT Cage, other clinical applications of these proteins is becoming widely adopted due to their effectiveness in forming bone and facilitating fusion. Clinicians have realized while these proteins are potent stimulators of bone formation there have been anecdotal reports of increased rates of radicular pain in the postoperative period when used in interbody arthrodesis procedures. Speculation as to the mechanism of this radiculitis is postulated to be due to the inflammatory effects of these proteins. Excess bone overgrowth around the spinal nerves in proximity to the fusion cage has been reported. No prospective studies have been performed assessing the incidence and etiology of this complication. The investigators propose a prospective study evaluating the incidence of this complication as well as postoperative imaging studies to help determine whether bony overgrowth is indeed occurring adjacent to the effected spinal nerves.

Inclusion Criteria:

• male or female age 18-75
• candidate for TLIF
• Lumbar levels L1-S1

Exclusion Criteria:

• more than 3 TLIF levels
• had a previous fusion attempt at involved level(s)
• had more than 2 previous open, lumbar spine procedures at the involved level(s)
• currently implanted with anterior instrumentation at the involved level(s)
• BMI >40
• active localized or systemic infection
• presence of a disease entity or condition which significantly affects the possibility of bony fusion
• has immunosuppressive disorder actively requiring treatment
• pregnant or interested in becoming pregnant during the study
• has a known sensitivity to device materials
• mentally incompetent or is a prisoner
• currently a participant in another study for the same indications

Patients age 18-75 with lumbar degenerative conditions including degenerative disk disease, spondylolisthesis with significant back and or leg complaints that have failed greater than 6 weeks of conservative therapy that are felt to be candidates for posterior lumbar instrumented fusion with transforaminal interbody fusion (TLIF).