Hip replacements fail by loosening of the mechanical components such as the acetabular cup or the stem of the prosthesis. There are many causes of loosening including fatigue endurance and fracture, fatigue endurance of cement, and biological adaptations. Consequently high quality test machines for hip implants remain critical to the future of the industry. Fatigue endurance tests of hip implants establishes endurance properties and performance by simulating the dynamic loading of the implant during gait.
Fatigue Test Results for Femoral Stem require testing six femoral stems and comparing results to the acceptance criteria in ISO 7206-8 (cyclic loading with a minimum load of 300N and a maximum load of 2.3kN for five million cycles) or ASTM F2068. Alternatively, the fatigue strength of the stem should equal the fatigue strength of a comparable predicate femoral stem. Test six devices for five million cycles. Femoral neck fatigue testing requires testing six femoral stems and comparing results to the criteria in ASTM F2068. Demonstrated fatigue strength of the neck should exceed fatigue strength of a comparable predicate femoral neck. Test six devices for ten million cycles. Spinal implant fatigue tests can run 10 million cycles and may require both axial and torsional loading. In addition, the test sample may require a wet saline 37C test bath environment and specialized fixtures. Implants and disc prostheses are inherently designed for load bearing over a known range of motion and to give years of trouble-free operation in the body. Electrodynamic servocontrolled fatigue test equipment has become the industry standard solution, replacing servo hydraulic test machines for these types of applications.
Applicable Testing Standards
- ISO 7206 Hip Implants Tests
- ASTM F1612 Cyclic Fatigue Testing Hip Arthroplasty Femoral Components
- ASTM F1820 Fatigue Test Machine Modular Acetabular Device
- ASTM F2009 Axial Taper Implants Prostheses Test Equipment
- ASTM F2068 Femoral Prostheses
- ASTM F2345 Determination of Static and Cyclic Fatigue Strength of Ceramic Modular Femoral Heads
- ASTM F2580 Fatigue Test Equipment for Hip Prosthesis
- ASTM F2582 Fatigue & Static Femoral Head & Acetabular Prosthesis
Recommended Test Machine
Static and fatigue forces up to 50 kN (11,250 lbf)
Frequency ratings up to 75 Hz
Oil-free, all electric actuator for clean test conditions
Lower purchase, operating, and maintenance costs than hydraulic equivalents
Static and fatigue forces up to 25 kN (5,500 lbf)
Frequency ratings up to 100 Hz
Servohydraulic
Small, portable footprint
Recommended Testing Accessories
Allows for testing in temperature-controlled water or saline solution
PID controlled temperature up to 45°C (113°F)
Size is optimized per application
Accompanied by a broad set of accessories that are designed for biomedical baths