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A Porous PEEK Solution for Spinal Implants

By Sean Fenske, Editor | January 5, 2017

As titanium regains acceptance for spinal fusion implants, an innovative PEEK option could slow that trend.

During my trip to the NASS (North American Spine Society) annual meeting in October of last year, I was “formally introduced” to the technologies involved with spinal fusion. While that trip led to my own predictions on what will happen to this market sector in the not-too-distant future, I was also made aware of a debate over materials for spinal fusion implants—PEEK vs. titanium.
While PEEK has surpassed titanium as the leading material of choice, the needle has started to swing back the other way. Further complicating the debate are hybrid options where an implant is developed using both PEEK and titanium. Manufacturers disagree on the superior option between the three choices and it doesn’t seem there will be an accepted consensus that puts one over the other two anytime soon.
While attending NASS, I did find a PEEK-based implant, however, that could prove a worthy adversary to the pro-titanium side. At the Vertera Spine booth, I meet with the company’s CEO, Dr. Chris Lee. He took the time to speak with me about an innovative technology that allows his company to manufacture a solid PEEK implant with the three-dimensional porosity that is seen with some titanium implants coming off of it. It’s not the result of a coating or a second layer being adhered to the solid PEEK implant. Rather, the entire implant is one solid piece. Following is a brief discussion I had with Dr. Lee about the technology.
Sean Fenske: What are the concerns with current PEEK implants for the spine?

Chris Lee, Ph.D., is the CEO of Vertera Spine.
Dr. Chris Lee: The primary concern with current PEEK implants is their inability to effectively integrate with bone. Instead, PEEK implants generate a fibrous (scar) tissue capsule that can reduce the implant’s stability and increase the chance of implant migration.
Fenske: How does your technology address these concerns?
Dr. Lee: Our porous PEEK Scoria technology features a porous architecture that seamlessly transitions to solid PEEK. This porous structure promotes bone formation on the cellular level and allows for tissue infiltration into the pores, effectively creating a strong mechanical interlock between implant and bone, to ensure good implant stability and fusion. The solid PEEK base allows the mechanical and imaging properties of regular PEEK to be retained.
Fenske: Do you develop your own implants or do you work with implant manufacturers on a technology-licensing basis?
Dr. Lee: We develop our own implants and perform the porous PEEK Scoria processing for our implants in-house. That said, we have extensive collaborations with professors at Duke University, Georgia Tech, Emory University, and Colorado State University, along with surgeons across the country, to study our porous PEEK implants and begin developing our pipeline products.
Fenske: As titanium begins its push to return as the leading material for the orthopedic spine sector, does PEEK have a limited lifetime in the industry? Is using PEEK in combination with this type of integration technology superior to titanium?
Dr. Lee: PEEK has been around in the industry for over 15 years and has been the leading implant material for interbody fusion cages for a decade. Despite PEEK’s limitations described previously, PEEK implants still offer a number of advantages over metal implants, including modulus close to bone (to reduce subsidence) and the ability to not produce any medical imaging artifacts. The return of titanium can partially be attributed to the new methods manufacturers are finding to incorporate nano topography or porosity into the implant. Titanium implants with three-dimensional porosity have shown to stimulate an osteogenic cellular response and allow for better osseointegration over their smooth counterparts. Independent studies and our own research indicate that adding porosity to PEEK can have the same effect as what has been seen with titanium while still offering the mechanical and imaging properties of traditional PEEK implants. Additionally, research from our collaborators is starting to show that porous metals, regardless of design, stress-shields bone that grows into the devices, which calls into question the long-term stability of this bony tissue ingrowth. Porous PEEK does not stress shield bone due to its favorable modulus. Therefore, porous PEEK could be the ultimate fusion solution for surgeons and we are excited to see this technology gain adoption in the spine fusion market.
Fenske: Does this process have applications in other orthopedic areas beyond the spine?
Dr. Lee: Yes, porous PEEK can be applied to numerous orthopedic applications, such as joint replacements, where there is a need for solid and long-term integration of the implant to bone.
Fenske: What’s ahead for Vertera and this technology? What do you foresee five years from now?
Dr. Lee: Currently, we are in transitioning into the full market release of our Cohere Cervical cage, our first product featuring our porous PEEK technology, for use in ACDF surgery. Since May 2016, Cohere has been under a limited market release to a select group of surgeons at leading institutions across the country. As we begin to see early successful outcomes with Cohere, we are looking to expand this technology to other spinal fusion applications, specifically lumbar fusion in the near future. However, we are most excited about porous PEEK's potential to bring to life implant designs and applications that were previously not possible and the development of other multifunctional materials that complement porous PEEK.

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