This testing is used primarily for making comparisons between the behavior and performance of different artificial disc models under the same simulated conditions. Testing artificial intervertebral discs requires a complex series of tests that mimic the motion of natural biomechanical processes a person engages in on a daily basis. By simulating the environment in which prostheses will effectively function, these pre-clinical tests provide critical insight as to how this device will perform in a patient. It highlights the strengths of a model’s design and can highlight areas for future improvements.
ASTM 2346 testing begins by using static loading to determine the maximum load the device can take without failure. The first thing that is done is a fixture stiffness test using steel blocks in light contact to determine the fixture stiffness. This is needed because the devices are often composites of an elastomer or crystalline polymer and a metallic endplate. This stiffness data is compared to the specimen stiffness data to help remove the fixture effects from the final testing. Once the baseline stiffness is established, we test a minimum of 6 specimens to complete failure to determine the ultimate load. The tests are normally run in compression, shear compression and torsion.
Depending on the design and generation of the artificial disc, axial compression, and compression-shear test series are conducted. These tests are also used on elastomeric components to test for axial compliance under load volumes that mirror those biomechanically sound. In addition, specimens containing elastomers, and sometimes polyethylene, are further subjected to creep and creep recovery testing to ensure that the device does not suffer permanent height loss during its useful life in the body.
The dynamic fatigue behavior of an artificial intervertebral disc is established by a running the device for 5M cycles in each of the testing modes used int eh static testing, compression, shear and torsion
Most commonly, all the testing performed on artificial discs is performed in a saline environment that is heated to 37C. The particulate is often collected but is not usually analyzed since we will be performing wear testing on the products also.
Other types of lubrication can be used to simulate body fluid, such as distilled water, saline mist or drip, bovine serum, HLA, or another lubricant to create alternative testing environments for a more comprehensive dataset.
A controlled testing environment is pivotal to the precision and accuracy of the testing and making sure that we have a good handle on R&R. The failure of prosthetic devices depends on stress, surface treatments, test frequency, manufacturing procedures, and materials. When a parameter is adjusted, all others must be kept exactly the same for the test to be accurate. If you are looking for a reputable partner to test an artificial disc, Empirical Technologies can help you.
