Mesenchymal Stem Cell Allograft and ACDF Study Outcomes
Commentaries by lead author Sheeraz A. Qureshi, MD and Brian Kwon, MD
Patients who received mesenchymal stem cell (MSC) allografts during anterior cervical discectomy and fusion (ACDF) had lower fusion rates compared with a matched cohort of patients who received standard allografts, according to a retrospective study in The Spine Journal. The between-group difference was not statistically significant.
“Achieving a solid fusion is critical to the success of anterior cervical discectomy and fusion surgery,” said lead author Sheeraz A. Qureshi, MD, who is Associate Professor of Spinal Surgery at Mount Sinai Medical Center in New York, NY. “As such, surgeons are looking for ways to improve the outcomes for fusion by trying different substrates.”
“While MSCs are being marketed as having the ability to improve fusion rates, our study shows that there is NOT a significant improvement in fusion outcome compared to standard allograft,” Dr. Quershi said. “This is important given the higher cost of MSCs compared to standard allograft.”
“This is a nonindustry sponsored study of the performance of 2 bone graft alternatives used in 1- and 2-level ACDF,” commented Brian Kwon, MD, who is Assistant Clinical Professor of Orthopedic Surgery at Tufts University School of Medicine and a spine surgeon at New England Baptist Hospital in Boston, MA.
“The 2 groups studied were MSC in cervical allograft cages versus allograft cages alone. Their primary endpoint was fusion rates, which were compared between the groups,” Dr. Kwon explained. “The authors found at 1 year after surgery, the MSC group had a fusion rate of 87.7% and the allograft group had a rate of 94.7% (P=0.19). The authors concluded that addition of MSC to interbody allograft vs allograft alone does not appear to increase fusion rate and may increase costs, approximately $1,250/level, to the operation.”
Matched Cohort Analysis
The authors retrospectively reviewed a consecutive series of 57 patients who underwent a 1- or 2-level instrumented anterior cervical discectomy and fusion that included interbody allograft, an anterior plate, and Osteocel® Bone Graft (NuVasive®, Inc., San Diego, CA) between 2010 and 2012 at a single institution. Osteocel is a first-generation iliac crest bone graft made from demineralized bone matrix, cancellous cadaveric bone, and MSCs, the authors noted.
A group of 57 patients matched for diagnosis, number of fusion levels, smoking status, and comorbidity burden served as the control group. The fusion construct in the control group included a structural interbody bone allograft (VertiGRAFT®, DePuy Synthes Spine, Raynham, MA) without Osteocel or other graft enhancers followed by anterior plating.
In both cohorts, approximately half of the procedures were 1-level and the other half were 2-level.
One-Year Fusion Rates Were Lower With MSC Allografts
At 1-year postoperatively, the rate of solid fusion was lower in the MSC allograft group than in the non-MSC cohort (87.7% vs 94.7%), although this difference was not statistically significant (P=0.19).
Of the 7 patients with failed fusion in the MSC allograft group, 4 were symptomatic and required revision surgery with posterior cervical fusion, while the remaining 3 were asymptomatic and did not require an additional intervention. Of the 3 patients with failed fusion in the non-MSC cohort, all 3 required revision surgery.
“As the authors conclude, if the addition of MSC to allograft used in ACDF does not improve fusion rates but increase associated costs, surgeons should give more careful thought to the regular use of MSC when performing ACDF; especially if their rationale is to improve fusion rates or control costs,” Dr. Kwon commented.
“The strength of this study is that it is observational and non-industry supported,” Dr. Kwon said. “The observational nature better reproduces what happens in everyday practice and without industry support the risk of bias for the commercial product is lower.”
“The weakness, in my opinion, is in the cohorts,” Dr. Kwon said. “The cohorts based on basic demographics appear to be similar but retrospective case matching does not always impart equipoise of the 2 groups. Additionally, the study may be underpowered to detect a true difference in fusion rates or support that there is a statistical difference between the 2 groups. Lastly, the follow-up is short, and whether some of the nonunions would go on to fuse and become less symptomatic cannot be answered.”
“It is important to understand that our study shows that MSCs work,” Dr. Quershi said. “Our findings just suggest that they don’t provide enough of an improvement to justify the significant increase in cost. I hope that industry will provide us with the opportunity to continue to validate MSCs in an unbiased clinical setting to determine optimal dosing.”
Dr. Quershi suggested the need for a prospective randomized controlled trial of MSCs, and added that he and his colleagues “are continuing to critically evaluate MSCs in other areas, including lumbar spine fusion.”
“Our hope is that the spine community will continue to critically evaluate new technology for the value it provides in patient care,” Dr. Quershi said. “Developing technology that improves the care we can provide is extremely important, but we want to make sure that the technology we are using is not increasing cost without truly being impactful on outcomes.”
“There are nearly limitless options for bone grafts available for today’s spine surgeon,” Dr. Kwon told SpineUniverse. “We as the end users owe it to our patients to be critical in our evaluations of bone graft materials that we so rely upon. Our patients’ good outcomes depend on them. McAnany et al have added one small piece to this complicated puzzle, and I applaud them.”
Overall, the findings suggest, “if it ain’t broke, don’t fix it,” Dr. Kwon concluded.