Wear Testing of Medical Devices

When is wear testing required?

The FDA and other regulatory bodies will often request mechanical wear testing when the device is introducing a new material couple or new material interactions that have not been adequately characterized through mechanical testing. Wear testing is also critical for comparing the wear properties of new devices to a previous generation device.

Test with Predicates

If you find you need wear testing, Element strongly recommends testing your implants side-by-side with a predicate device, to ensure an “apples-to-apples” comparison for your submission. Element’s wear testing frames are configured for easy side-by-side comparison testing of both your device and a predicate on one single frame, ensuring reliable and repeatable results.

Wear Testing per ISO 14242-3: Samples for hip wear testing are enclosed in an environmental chamber for submersion in bovine solution in accordance with ISO 14242-3. The hip implants are cycled repeatedly through the complex motions required by the specification. Periodically, testing is haulted in order to measure for mass loss, typically (7) times throughout the program. After testing, the particulate resulting from the femoral head/acetabular liner interaction is evaluated in-house utilizing our SEM/EDS capabilities.

Our Equipment: Our proprietary in-house hip wear simulators each contain 6 test stations with 2 load/soak controls. All stations are linked to ensure uniform axial force and displacement. In order to accurately reproduce walking kinematics, each station oscillates with a 23 degree bi-axial rocking motion that simulates flexion/extension, abduction/adduction, and internal/external rotation.

Wear Testing per ISO 14243: Our knee wear test equipment measures wear between the femoral component and the tibial insert. The test frames can simulate force or displacement controlled gait kinematics per ISO 14243-1 (load control) or ISO 14243-3 (displacement control). Axial force (Fz), anterior/posterior force (Fx), flexion/extension (My), and tibial rotation (Mz) are coupled in order to accurately simulate the complex, simultaneous motions of the human knee.

During testing, periodic mass/loss analyses are performed using the stringent clean, dry, and weigh process laid out in ISO 14243. The post-test particulate is also evaluated using scanning electron microscopy (SEM) after the conclusion on testing.

Wear Testing per ASTM F2423 & ISO 18192: For spinal implant wear testing, Element utilizes our 6 station MTS Bionix® Spine Wear Simulator with load/soak control. This test machine offers 6 degrees of freedom and satisfies both ASTM F2423 and ISO 18192 standard test methods. Our in-house metallurgical laboratory also provides analysis of both wear surfaces and particulate by utilizing SEM, EDS, and stereoscopic evaluation equipment.