Biomechanics of the Vertebral Column and Internal Organ Response to Seated Spinal Impact in the Rhesus Monkey (Macaca Mulatta)

Rhesus monkeys were anesthetized; radiographed; restrained by lap belt, torso harness, and limb retention straps; positioned in an impact carriage; and exposed to +G_z seated rectangular acceleration-time histories from predetermined drop heights. The shock programmer used throughout these experiments was aluminum honeycomb. Pulse accelerations ranged 25-900 G and total time duration 2-22 ms. Shortly after impact, all primates were radiographed, killed, and a necropsy performed. Attempts were made to determine injury potential as a function of plateau acceleration and pulse duration for various target organs. Spinal injury data support previous results and theoretical considerations that there are two distinct injury potential regimes; one, for which the velocity change is the determining physical parameter, and the other for which peak g is the determining factor. Injuries observed in parenchymatous organs included external and surface hemorrhaging in the liver, lesions of the lung, and cardiac lesions. Their severity ranged from minor reversible abrasions to lethal trauma. These experiments strengthened confidence in the applicability of animal experiments to the quantitative explanation of human injury and to the extrapolation of animal results - after the application of the proper scaling factors - to human situations.