A Guide to Static and Cyclic Fatigue Testing of Surgical Fixation Devices in accordance with ASTM F2193
A summary of the standard and the tests involved
Standard At A Glance
- ASTM F2193
- ASTM F1717
- ASTM F1798
- ASTM F2706-18
- ISO 12189-8
- High Cycle Fatigue
Written by Toby Lane
We recommend that you review the standard fully to understand all of its requirements.
Test SystemBoth the static and fatigue tests can be carried out on a single dynamic test frame such as the ElectroPuls® E3000 or ElectroPuls E10000 All-Electric Dynamic Test Instruments. For customers with Servohydraulic infrastructure, the 8872 and 8874 test frames would also be suitable options for this testing.
Test ParametersBoth Spinal Plates and Rods are tested via the same four-point bending procedure to determine the stiffness, yield moment, ultimate moment and fatigue runout moment at 2,500,000 cycles. Firstly, in both cases, static testing at a displacement rate up to 10 mm/min is carried out for a minimum sample size of 5 specimens.
The fatigue test follows with at least 2 specimens being tested at each load level. Three load levels must be used to provide a minimum of 6 data points. The specimen must not fail after the 2,500,000 cycles for one of these load levels so that the fatigue runout moment can be identified. The load values can be determined by the user or should correspond to 75%, 50% and 25% of the static yield moment.
For the dynamic tests an R ratio of 0.1 is used for thoracic and lumbar components and -1.0 for cervical spine components (to illustrate reverse loading). Testing can be done up to 30 Hz in all cases.
The static tests should be carried out with a loading rate no greater than 25 mm/min for a minimum of 5 samples to create load-versus-displacement graphs. The fatigue tests should be completed with a sinusoidal waveform at a maximum of 30 Hz and an R ratio of 0.1 for thoracic and lumber screws. Again, an R ratio of -1.0 should be used for cervical screws. The procedure should then be the same as that of the other two components, with at least 2 specimens being tested at each load level, three load levels being used to create 6 data points, a maximum of 2,500,000 million cycles and 75%, 50% and 25% of the static yield moment acting as starting points for loading values. For all components, testing can be completed in other environments (namely saline solution) with justification and quotation of characteristics such as temperature, pH and solution strengths.
ElectroPuls instruments are state-of-the-art electrodynamic test systems for dynamic and static tests on materials and components. Powered entirely from a single-phase mains supply, they feature the latest in testing technology and a host of other user-oriented features.