Comparison of Posterior Cellular Bonegraft Options for Single Level Lumbar Spinal Fusion

Consecutive patients who are surgical candidates for a one-level anterior/posterior lumbar fusion are eligible for inclusion into the study. Inclusion criteria included:

• 18 to 65 years of age.
• Primary degenerative disc disease of one level with or without prior decompression.
• None or up to moderate stenosis that could be treated with a laminotomy
• degenerative spondylolisthesis grade 2 or less.

Exclusion criteria:

• More than single level symptomatic degenerative disc disease.
• Advanced stenosis that needed extensive laminectomy for adequate decompression.
• Lytic spondylolisthesis.

The study proposal underwent IRB review (HealthEast IRB #1510002). All the participants provided written informed consent. After completing IRB approved consent, patients were randomized, by computer generated program, to 5cc IBG or one of 5 other types of PSF osteoinductive bone graft alternatives: bone morphogenic protein (BMP, small Infuse, Medtronic, Memphis, TN), autologous concentrated bone marrow aspirate (BMA) from the iliac crest (combined with 5cc Allo chips), allograft bone marrow derived stem cells (cAlloBone, 5.3cc Trinity Elite, Orthofix, Lewisville, TX), fat derived allograft stem cells (Allostem, AlloSource, Centennial, CO) combined with 5cc morcelized cancellous allograft (cAlloFat), or placental derived allograft stem cells (NuCel, Nutech, Birmingham, Alabama) combined with 5cc morcelized cancellous allograft (cAlloAm). A historical control group of 5cc cancellous freeze-dried allograft (Allo) was used as an inert "negative" control group. There are 27 patients in each group. All anterior fusions used BMP (small Infuse). The decortication technique of the posterior fusion is identical for all patients. All patients have identical fixation instrumentation implanted (anterior lumbar plate and posterior facet screws). Posterior fusions were instrumented to eliminate posterior micromotion and subsequent pseudarthrosis as a confounding variable. All the fusion procedures were performed by the lead author to ensure a uniform surgical technique across all bone graft type groups. Therefore, the surgical technique is as uniform as practically possible to minimize confounding variables related to the surgery with the only variable being the various posterior fusion bone graft materials. Patients are blinded to the posterior type of bone graft. The volume of bone graft is the same for each type, approximately 5cc.

Postoperatively, all patients are followed for a minimum of 2 years. During this time radiographs and lumbar Thin-cut CT scans of the fused level are obtained at approximately one year postoperatively to assess fusion success of both anterior and posterior spinal columns. Specifically for the posterior fusion, if only a unilateral fusion was identified, the fusion was tallied as half fused. The limited (to the levels fused) CT scan had 2.88 mSv radiation exposure, or similar to one year's worth of background radiation. Radiographs at >2 years are reviewed for progressive loss of adjacent segment disc height for assessment of adjacent level degeneration. Secondary endpoints of clinical outcomes are assessed pre- and postoperatively with multiple outcome instruments: visual analog scales (VAS, 0 to 10 scale with greater value is worse pain) for back and leg pain; pain drawing; Oswestry disability index (ODI, 0 to 100 scale with greater value is worse disability); pain medication usage (non-opioid and opioids); and patient self-assessment of procedure success over a minimum 2-year follow-up period. Outcome results are entered by office personnel (blinded to the type of bone graft) into computer spreadsheets, with the treating surgeon blinded to these results. The historical control group consisted of retrospective cohort of consecutive patients which fit the inclusion/exclusion criteria and had their PSF with freeze-dried allograft morcelized bone. Additional surgeries were tracked for all groups, including pseudarthrosis repair, adjacent level decompression, adjacent-level fusion extension, spinal cord stimulator implantation, and posterior instrumentation removal.