ASTM F1798 describes the procedure for testing subassemblies and interconnection mechanisms to determine the fatigue strength and resistance to loosening during arthrodesis.(fusion)
Hooks, screws, and bands connect to rods and plates. These connected parts form Spinal Implant Subassemblies. In this specification the parts are tested in a saline or simulated body fluid in vitro to predict the behavior of the parts in vivo performance.
Procedure for Measuring Static Mechanical Properties
Measure tightening torques of all assembled parts
Apply 20N/sec (25 mm/min) and 25Nm/min (25 degrees/min).
Static A-P load (Fx), Transverse load (Fy), axial gripping capacity (Fz), transverse moment (My), and axial torque (Fz)
Procedure for Measurement of Fatigue Run Out
Measure tightening torques of set screws or nuts in connected parts.
Max Frequency not specified, but reported
Fatigue loads will be sinusoidal- load amplitude control
Perform tests in Fx, Fy, Fz, Mx, My, and Mz.
In each relevant loading direction, apply continuous sinewave. If failure occurs prior to 2.5 M Cycles, decrease load and test in same manner. Loading in some directions is Uni-directional whereas in others it may be reversing.
For a full description of this specification go to www.ASTM.org.