Spinal Implant Testing
Service life testing of spinal constructs is critical as fatigue failure is more common than catastrophic failure. During normal patient activity, spinal constructs can be subjected to high in vivo loading, which may result in catastrophic failure. Cyclic testing is performed in order to evaluate the number of cycles it takes for fatigue failure to occur. Loading is typically applied with a constant-amplitude load-controlled sinusoidal waveform running in excess of five million cycles. Simple static testing is also performed to evaluate the load required to result in spinal fracture.
The Instron® Linear-Torsion ElectroPuls™ system is recommended as it allows the user to complete both static and dynamic tests according to ASTM F1717-12 standards on a single machine. A dedicated spinal fixture can easily be mounted to this system with the option of mounting a saline bath onto the base for in vivo testing. When using the bath, the load cell is designed to be mounted onto the actuator utilizing Instron’s patented Dynacell technology for inertia compensation. Instron’s patented stiffness-based turning algorithm ensures excellent waveform fidelity, even with non-linear specimens.