Element’s team of Engaged Experts performs mechanical testing on total knee prostheses as well as individual knee replacement components, including femurs, patellas, tibial trays, and tibial inserts.These implants and components are typically subjected to endurance testing, including fatigue and wear testing, in order to characterize useful life and durability. In addition, various static tests assist in determining system properties, such as range of motion, constraint, contact pressure, and component interlocking strength.
Whether for feasibility or submission purposes, Element's fatigue testing services provide the critical data you need to validate your device design.
Tibial Tray (ASTM F1800 & ISO 14879): Tibial tray fatigue testing is performed by fixating one half of the tibial baseplate and applying a constant amplitude load to the unsupported half of the baseplate. Per ASTM F1800 & ISO 14879, testing is performed to a run-out of 10 million cycles. For submission testing, five samples must survive 10 million cycles under at least 900 N of load.
Tibial Bearing Components: For implants that are posterior-stabilized, shear fatigue testing of the UHMWPE tibial post is recommended. Six samples are cycled at varying loads to develop an S/N curve. At least one sample should complete full run-out to 10 million cycles.
Femoral implants: Femurs are evaluated for fatigue properties in a variety of conditions. Various flexion angles and cementing configurations can be tested to evaluate fatigue performance. Both S/N curves and minimum run-outs can be tested.Tibial Insert Endurance under High Flexion: For knee systems designed to allow high flexion, this test method evaluates the ability of UHMWPE inserts to resist deformation and fracture due to repeated deep knee bend activities. Tests are performed in-vitro to 220,000 cycles at a 2,275 N load. Results are bench marked by performing pre- and post-test scans, along with constraint tests.
Contact Pressure & Constraint Testing
Contact pressure and distribution can have significant effects on knee implant wear properties, while constraint testing is critical in determining the dislocation and motion resistance of the implant system.
Contact Pressure: Utilizing a variety of pressure sensitive films, Element provides contact stress analysis of tibiofemoral and femoral-patellar knee implant contact mechanics. Testing is performed at multiple flexion angles with varying normal loads.
Constraint Testing (ASTM F1223): Element provides both translational and rotational knee constraint testing services per ASTM F1223. Anterior, posterior, medial, lateral and rotational tibiofemoral shear forces are applied to induce either subluxation or a specified angle of rotation. This test can be crucial when comparing standard inserts, congruent inserts, or posterior stabilized inserts.
Wear Testing (ISO 14243-1 or ISO 14243-3)
Knee wear testing allows for the measurement of wear rates between the femoral component and the tibial insert. Element can perform wear testing in either force or displacement control.
ISO 14243-1 or ISO 14243-3: 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. Test programs run at a frequency of 1 Hz to 5,000,000 cycles. At various intervals, the samples are removed and precisely measured for mass loss. After testing, a particle analysis is performed on the test solution using SEM/EDS equipment to create a comprehensive morphology report.
Element’s knee wear test frames contain:
- 6 test stations and 2 load/soak controls
- Ability to perform force or displacement-controlled testing (ISO 14243-1 or ISO 14243-2)
- Environmental chambers for bovine solution
Related Services and Standards
ISO 14243-1, ISO 14243-3, ISO 14879
Tibial Fatigue Testing
Component Interlock Strength
Contact Pressure Testing
Porous Coating Testing
Range of Motion Testing
Femoral Fatigue Testing
Fretting Corrosion Testing
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Maciej has over 10 years of experience in medical device testing and analysis for FDA 510(k) and CE submissions.
Kent is the co-founder of Medical Device Testing Services, acquired by Element in 2017. Kent’s expertise in medical device testing has led to the development of new test instruments, standards and protocols.