Data demonstrate reduced subsidence of Endoskeleton titanium interbody fusion implants compared to PEEK

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Results of a new study demonstrating a statistically reduced subsidence rate and overall subsidence amount of its Endoskeleton TA device compared to a commercially-available PEEK device were presented during an oral podium presentation at the annual meeting of the International Society for the Advancement of Spine Surgery (ISASS, 15–17 April, San Diego, USA).

The presentation was delivered by lead author Antonio Valdevit during the general session on biomechanics.

The findings, which come from a dynamic mechanical study assessing subsidence rates of spinal implants during continuous cyclic loading, demonstrate that Titan’s TA anterior lumbar interbody fusion (ALIF) interbody device provided for a 410% reduction in rate of subsidence and a 40% reduction in overall subsidence amount compared to a commercially-available ALIF PEEK implant of similar footprint (p<0.001). The parameters of the study were designed to reflect the three-month post-operative period in which the incidence of subsidence is most likely to occur in-situ.

Antonio Valdevit, professor, Department of Chemical Engineering & Materials Sciences at Stevens Institute of Technology, and lead author of the study, said, “Most mechanical subsidence studies for interbody fusion devices are performed statically according to ASTM testing standards. However, from a clinical standpoint, subsidence occurs dynamically under continuous cyclic loading. Our study replicated this clinical condition and demonstrated that Titan’s titanium TA implant resulted in a statistically slower and more gradual settling upon the endplate surface, producing a soft landing, whereas the PEEK implant had a statistically increased settling rate and overall subsidence amount. The PEEK implant’s hard landing may be the result of its anti-expulsion teeth that distributed the overall compressive force over a smaller contact area as compared to Titan’s roughened macro surface. This study distinctly shows that subsidence is a function of more than the implant’s material modulus, but also importantly involves device design, which may have meaningful clinical implications.”

Valdevit spoke to Spinal News International about the results, suggesting that “It is a combination of the material and the shape that has given us this result. With the titanium device that Titan makes, what happens is that because of all the indentations it has, it sits on the vertebral body on the outer rim a little better than most others. Those inter-digitation spread the loading around so that it fits, sort of like when you fit your two hands together you can interdigitate your fingers, but if you have one hand out and you make a fist with the other it is not going to fit in too easily.”

Valdevit continued, “I think the biggest thing we could do for patients, and this is from a research perspective, is to standardise how we look at these implants. The way that we examine dynamic loading, I have been doing it for years, but it is not very common. People usually look at research in terms of where we start and where we end, but there is a lot more information that we have been throwing out. If we can collect the data in-between where we started and where we ended then we can get a lot more information, such as how fast subsidence is happening, and is that important, especially in the way that bone heals. “

 

Andrew Shepherd, vice president of marketing of Titan Spine, commented, “The importance of this study cannot be overstated. The spinal community has long been led to believe that subsidence is purely a function of an interbody device’s material modulus and that PEEK implants will subside less than titanium devices since PEEK’s modulus is closer to that of the vertebral body. Valdevit’s study directly refutes this myth and confirms what the biomechanical community has always known. Implant design plays a much larger role in subsidence than the implant’s modulus of elasticity. Titan will continue to design its implants based on scientific principles rather than marketing misconceptions to drive sales.”

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