Biostability of an orthopaedic device and its long-term implantable biomaterials

The BDyn device is a bilateral posterior dynamic stabilisation spinal implant used to treat degenerative disc disease. The BDyn device consists of a polycarbonate urethane (PCU) component, a silicone component, a mobile titanium alloy rod, a fixed titanium alloy rod and it is fixed to the vertebrae by titanium alloy pedicle screws. The viscoelastic properties, chemical structure and surface morphological changes of the untreated, in vitro degraded and in vivo degraded were compared. The macro and micro-scale viscoelastic properties, chemical structure and surface morphology of five long-term implantable PCU biomaterials, which were in vitro degraded by four separate degradation methods were also investigated. No resonant frequencies were reported for the untreated and in vitro degraded components and devices however, resonance was detected in the frequency sweep test of BDyn Explant 2 with the sharp increase of the loss stiffness occurred at 4 Hz; this highlights the importance of evaluating orthopaedic devices with frequency dependent mechanical testing techniques. The biomaterials were viscoelastic throughout the frequency range tested and were significantly different at specific frequencies when comparing untreated specimens to specimens degraded by a specific degradation method; this further highlights the need to evaluate elastomeric biomaterials with frequency dependent mechanical testing techniques

Viscoelastic properties of human and bovine articular cartilage : a comparison of frequency-dependent trends

Acknowledgments The authors would like to thank Spencer C. Barnes and Hamid Sadeghi for assistance during experimentation. We would also like to thank patients donating tissue and the surgeons collecting these. Funding The equipment used in this study was funded by Arthritis Research UK (Grant number H0671). We are grateful to Arthritis Research UK for the award of a PhD studentship to Anna A. Cederlund (Grant number 19971). Arthritis Research UK had no role in the design of the study and collection, analysis and interpretation of data and in writing the manuscript.Peer reviewedPublisher PD

Contributor to the March Issue/Notes

Notes by Bernard F. Grainey, Warren A. Deahl, William B. Lawless, James F. McVay, and Thomas F. Halligan

Analysis of hydration and subchondral bone density on the viscoelastic properties of bovine articular cartilage.

Funding JC is currently funded by an Engineering and Physical Sciences Research Council scholarship (EP/N509590/1). We are also grateful to Arthritis Research UK for the award of a PhD studentship to Anna A. Cederlund (Grant number 19971). The materials and testing equipment used in this study was funded by an Arthritis Research UK grant (H0671). The Engineering and Physical Sciences Research Council and Arthritis Research UK (now part of Versus Arthritis) had no role in the design of the study and collection, analysis and interpretation of data and in writing the manuscript.Peer reviewedPublisher PD