Reappraisal of biodynamic implications of human ejections.

Vertebral compression represents a significant percentage of the morbidity associated with upward ejection. Vertebral and intervertebral structure reacts to and is sometimes irreversibly altered by ejection acceleration. Design and material properties of the normal vertebral column are sufficiently constant that when structural characteristics are defined and acceleration profiles known, prediction of failure may be made. Compressive load analyses of vertebra-disc complexes have demonstrated that the vertebral endplates are the Initially falling structures of the spinal column. From experimental data on vertebral breakingloads, acceptably accurate probability-of-mjur»curves for static loading have been generated. These data together with data describing the dynamic response characteristics of the human body permit calculation of the probability-of-injury for dynamic loading produced by exposure to impact accelerations. As sn aid to the designer of ejection systems, application of these concepts should refine the estimate cf "safe" acceleration profiles and minimize the risk of irreversih!; vertebral deformation.