Design and manufacturing of electronic controlled and feedback fatigue testing device for spine implants

Dynamic loads ocur continuously in the human spine during daily activities. This is also viable for implanted patients, and this field of stud is fairly new and interesting. With the Fatigue Tester for Spinal Implants with electronical control and feedback, it is aimed to examine the behavior of spinal implants under dynamic loads, which can stay in the body of the patients for 2 years or more time. Parameters such as the magnitude and speed of the force to be applied with the fatigue test device can be changed and all information is continuously recorded in text format. Based on ASTM F1717 standard. Since there is a distance between the loading axis of the device and the connection axis of the specimens, the device performs a compression bending test. The fatigue tester uses a pneumatic piston and other pneumatic assembly to achieve dynamic loading. Since pneumatic actuators generally deviate from the expected force, the applied force is constantly controlled by a load cell and the pressure can be changed momentarily with the proportional regulator according to the data received from loadcell, and the force control within itself can be provided continuously. The developed fatigue device can perform dynamic loading tests of spinal implants in the range of 1Hz to 5Hz, with forces between 50-250N. According to the data read from the regularly calibrated load cell, the normality test is successful and the tests are carried out with high reliability. A specimen should endure 5x106 cycles of load and if the specimen can endure this number of cycles will be considered as runout. This is equivalent of 7000 cycles per day for almost 2 years.