Flexible Metal – Leveraging Powerful Design Tools to Create Compliant Medical Devices

Mechanobiology – the emerging field of biomedical engineering that is concerned with how biological mechanisms adapt and respond to external stimuli, notably stresses and strains – is now teaching us how important the idea of compliance (used here in reference to flexibility) is to medical devices. Indeed, the idea of orthopedic device stiffness has long been debated, with  the current trend leading to more patient-specific applications tuned to the loading conditions. The control of orthopedic device stiffness has long been relegated to material development, with PEEK (polyether ether ketone) its shining star – first used in spine devices during the turn of the century to great success. Although PEEK is biocompatible, it’s surface lacks certain osseointegrative capabilities, leading to most implants needing a plasma spray coating of titanium or another material. As metal additive technologies continue to become more advanced, titanium is poised to again become the material king.

But how can engineers turn the rigid nature of metal into a benefit? The answer lies in a combination of computational modeling and an understanding of material stiffnesses – which we can analyze using Finite Elements Analysis in nTop Platform.

Stress Values at different static compression values

By investigating the stress and displacement parameters at differing compression values, the stress and displacement fields can be combined mathematically into a function.

A Heat Map of von Mises Stress Values, where Colors Show the Localized Stress Values of the Field

This function allows us to computationally “tune” the stiffness of a structure exactly, utilizing what I like to call “the movement of material!”