The initial phase of a military ejection sequence exerts substantial axial loads on the spinal column. Eccentric inertial loading on the thoracolumbar spine can lead to injury. Most serious injuries due to ejection are in the form of a vertebral fracture, most commonly occurring at the thoracolumbar junction. The objective of the current study was to understand characteristics of a military seat ejection by employing an experimental model designed to simulate the boost or in-rail phase. The model incorporates realistic boundary conditions and is capable of quantifying metrics associated with injury tolerance such as applied accelerations and resultant loads and spinal kinematics.

A total of four human cadaveric spine specimens (T12-L5) were tested. The test matrix consisted of two parts. The first part subjected specimens to sub-failure loading to outline spinal kinematics during dynamic vertical acceleration. The second part of the test matrix consisted of acceleration tests designed to induce compression and/or burst fractures as sustained by military aviators during ejection. The developed experimental model is the first to simulate realistic inertial loading during ejection-type accelerations using isolated osteoligamentous spines and may provide imperative injury mechanism data for future safety design considerations.