Biologics is an emerging area of the spine field and while good work has been done in this space, there is plenty of room for additional development and acceptance.
"There is really no consensus on what exact products or techniques are at the forefront of biologics in spine surgery today," says Hooman M. Melamed, MD, an orthopedic spine surgery at DISC Sports & Spine in Marina Del Rey, Calif., and director of scoliosis at Marina Del Rey Hospital. "If you ask spine surgeons in the same city you will get different answers. It all depends on their historical results and their individual training."
Iliac bone crest vs. synthetics
Traditionally spine surgeons harvested iliac crest bone graft to promote fusion, but some surgeons have replaced this method with alternatives, including BMP-2 and other bone graft strategies carrying a lower morbidity profile.
There are several classes of biologics with the potential to improve spine surgery outcomes. BMP-2 remains the most dominant player in the market currently, but several promising materials could eventually become more prominent in the future.
"Ceramics is a whole other class of biologics with a host of agents that includes osteoconductive material," says R. Alden Milam, MD, of OrthoCarolina based in Charlotte, N.C. "That seems to encompass the majority of new products coming out. BMP is osteoinductive. The focus of new products on the forefront combine both the osteoinductive with osteoconductive properties, and all of these things are done with the idea of improving the fusion rate and decreasing morbidity associated with harvesting the patient's bone."
Manufactured materials have an advantage over allograft, says Dr. Milam, because they are more reproducible from one patient to the next. Allograft is highly variable in terms of the cadaver's age, condition and disease, and certain processes can cause bone to become brittle. Surgeons won't have to worry about these factors with manufactured biological substances. But not all surgeons are onboard with synthetic biologics available today.
"The jury is still out if any of these developments are more effective than the use of bone," says Dr. Melamed. "There are a wide variety of answers and many products but not one that is truly superior. We thought that BMP-2 was the gold standard, but unfortunately complications have been reported and many doctors shy away from using it."
Some of the biggest strides being made right now in spine biologics considers cost in addition to outcomes for various products. "Surgeons are looking at the outcomes of patients with iliac crest bone graft versus those who have synthetic materials, or even BMP, as a way of measuring what the associated costs are for these devices and how biologics can improve patient outcomes," says Dr. Milam.
Research & development challenges
There are still challenges for manufactured biologic materials for spinal fusions. Surgeons and engineers are still experimenting with the ideal size for a scaffold and whether anything that could be added to the scaffold that causes induction of bone.
"We are searching for a modulus of elasticity that matches the type of bone where the device is being placed. The modulus of elasticity measures the strength of the scaffold," says Dr. Milam. "Everyone is looking for that perfect thing that causes bone to form 100 percent of the time without any complications. You don't want to form too little or too much bone — just the right amount."
Developers also face an up-hill battle to achieve FDA clearance and reimbursement for new innovations. "Research and development is challenged by the cost of bringing new products to the market and the associated reimbursement of the products once it reaches the market," says Andrew Cash, MD, director of the Desert Institute of Spine Care in Las Vegas. "With the costs increasing and reimbursement decreasing, investors are significantly less likely to risk developing a new product."
New product development is pricey and often more expensive as it enters the market. Today's healthcare environment focuses on both cost and quality of care, which could hinder small advancements going forward.
"I suspect that biologics will always be expensive because of the cost to develop them," says Daniel Resnick, MD, Congress of Neurological Surgeons President and Professor and Vice Chair of Neurological Surgery at the
University of Wisconsin School of Medicine and Public Health in Madison. "They can't piggy back like a lot of devices. In order for them to be successful, they need to provide groundbreaking advances or do something so much better than existing technologies that it's worth the price to pay for them."
Beyond fusion
Beyond spinal fusion, surgeons and engineers are developing biologic products for injecting growth factors into degenerated discs.
"The most exciting research in spine biologics is the concept of restoring a health disc matrix with protein injections — growth factors and/or inflammatory cytokine blockers. [They will perhaps play] a more important role will be the prevention of disc degeneration," says Dr. Cash. "The greatest opportunity for spine biologics exists in the arena of prevention, which will improve patient satisfaction, diminish time lost from work and life, and will significantly reduce the overall costs of spine healthcare on an individual world-wide scale."
There are also surgeons participating in studies using cell-based therapies for disc repair, such as Mesoblast's stem cell therapy, ISO Technologies' NuQu and DiscGenics.
Future opportunities
So what does the future hold five to 10 years down the road? Dr. Milam is excited about using nanotechnology to differentiate the synthetic materials from genetic biologics. "There might be nanotechnology for pedicle screws to encourage bone to grow into the screw so that it doesn't loosen later," he says. "Or another substance to put onto the PEEK spacer to cause the bone to grow into that."
Stem cells are also being tested for their effectiveness in helping patients. "Injecting these cells with cadaver bone and allograft can potentially create an optimal environment for bone healing," says Dr. Melamed. "This is an exciting area of regenerative medicine that can possibly be very beneficial for bone healing and yet very cost effective."
Biologics could also play a huge role in restoring neurological function after spinal cord injuries. There are a few companies in the marketplace today, such as InVivo Therapeutics, focused on developing biologic material for spinal cord injuries, but solutions are still in their early stages.
"I think the most important area where the use of biologics could really provide a benefit is in restoration of neurological function in spinal cord injury or nerve root injury and an amelioration of pain related to either nerve or disc disorders," says Dr. Resnick. "That's where we don't really have anything else and those are biological processes that can be impacted by various factors. There are no other screws, graft or substance that we can use for that. For biologics to really make a statement, they need to do something groundbreaking. Those two areas are where there is an opportunity for a paradigm shift in how we view patients with those disorders."
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