An apparatus for spine biomechanical testing

A testing system that applies a pure bending moment will uniformly load a spinal construct and be capable of identifying its weakest point. This study describes an apparatus for use with a material testing machine that is simple, inexpensive, and reliably creates a pure bending moment along the whole spine. We tested the system using two strain gauges attached to an aluminum alloy beam. First we verified the reliability and accuracy of the strain gauges system by comparing experimental measurement strain to theoretical prediction of strain in a cantilever beam model. The second experiment assessed the moment and strain created at two locations on a beam which was fixed at one end. The mean strain recorded from the two gauges demonstrated that moment is not uniformly distributed along the length of beam that is fixed at one end. The third experiment was similar to the second except that the beam was attached to an X-Y table instead of being fixed. Results demonstrated that a pure bending moment status is achieved when the end of the beam is fixed to an X-Y table.