Despite the dramatically higher number of lumbar spinal fusion procedures over the past decade 18,19), the potential for psuedoarthrosis persists. Lumbar fusion success with autologous bone graft alone have reported fusion rates of 65–93% 20–24). Autologous iliac crest bone graft (ICBG) is considered the gold standard for spinal fusion 13). However, ICBG also comes with complications, such as donor site pain, infection and prolonged recovery. Local bone at the surgical site is available, however the supply is limited; thus the need for alternative bone grafting 1,2). There are promising alternatives to autologous bone that offer comparable fusion success rates, and avoid donor site harvesting 5–10).
Cellular bone allografts are an alternative to autograft given they have all three principal components of a bone graft, namely osteoconductivity, osteoinductivity, and osteogenicity.
Musante et al reported 90% fusion success in procedures using viable osteogeneic cells, with no differences in reported fusion rates in patients with and without risk factors 26). Other CBAs, including Vivigen (DepuySynthes, Raynham MA), have shown spinal fusion rates at 90% 27). In a study of multilevel fusion in a posterolateral construct with CBA, the fusion rate was reported as 98.7% 15). Elgafy et al, reported a fusion rate of 91.7% with CBA in 96 patients and 222 treated levels 14). Further, Ammerman et al reported 91.3% successful fusion in minimally invasive TLIF cases using CBA in 23 patients totalling 26 levels 16. In extreme lateral interbody (XLIF) procedures, Tohmeh reported a fusion rate of 90.2% in 40 patients with a total of 61 levels 17). These data demonstrate cellular bone allografts result in fusion rates that are comparable to autograft.
This prospective clinical trial demonstrated successful fusion in 95.3% of patients, and also showed significant improvement in three key clinical outcomes, ODI, VAS-Back Pain, and VAS-Leg Pain. Copay et al suggest a meaningful clinical important difference (MCID) change in clinical outcome values from baseline to 12 months to be 12.8 for ODI, 1.2 for VAS-Back, and 1.6 for VAS-Leg 26). In the current study, the average improvement was statistically significant for all three clinical outcomes; -20.5 for ODI, -40.8 for VAS Back, and − 55.1 for VAS Leg. All clinical outcome measures met the MCID criteria, further demonstrating the positive impact and meaningful improvement from lumbar spinal fusion in this patient population.
Fusion success and clinical outcomes may be affected by patient risk factors for pseudoarthrosis, including older age, osteoporosis, alcoholism, malnutrition, and smoking 29–31). In this study, we analyzed subsets of patients with known risk factors for nonunion and found the fusion rates not significantly different between patients with a single risk factor or multiple risk factors.
While there has been a recent report of disease transmission through the usage of a different CBA where multiple tuberculosis cases in graft recipients were traced to a single donor lot, allogeneic bone has an extensive clinical safety record and Trinity allografts have never been linked to donor-derived infections after more than 13 years of being commercially available 32–34). Prior to this incident, only one other occurrence of suspected tuberculosis disease transmission through the transplantation of allograft bone was identified in the published literature and that was reported nearly 70 years ago before modern donor screening criteria were established 35). In order to address the risk of disease transmission with Trinity Elite allografts, the medical and social history of each donor is carefully screened prior to donation for medical conditions or disease processes that would contraindicate the donation of tissue in accordance with current policies and criteria that have been established by FDA and the American Association of Tissue Banks (AATB). 36,37)
This study adds significant value to current literature regarding CBAs and their efficacy in spinal fusion. By preserving the inherent properties of these grafts, including the osteoinductive and osteogenic components retained within the bone matrix, CBAs provide a unique alternative to autograft. An important distinction of note is that due to propriety processing techniques, one CBA cannot be easily compared to another. Ultimately, with a CBA, we found fusion rates to be comparable to ICBG with fusion rates being consistent across the entire patient population. Successful fusion was attained using a CBA regardless of risk factor reported, and without the drawback of donor site morbidity and complications associated with BMP products.
Varying surgical approachs (e.g., TLIF, ALIF, PLF) were included within this analysis, as opposed to a single-approach, therefore is a primary limitation of this study. Although limiting form a statistical standpoint, this analysis provides real-world evidence of lumbar fusion in the general community. In addition, this analysis does not include a control arm for comparison, only comparison to outcomes identified within available scientific literature. In spite of these limitations, the preliminary data provided within this report demonstrates that Trinity ELITE is an effective bone graft alternative for patients being treated with lumbar spinal fusion.