Establishment of the model of motorcyclist ejection injury

Objective： To establish the device and model of motorcyclist ejection injury. Methods： Based on our laboratory devices, a motorcyclist ejection injury simulation system was developed. A total of ! 8 pigs were approved by the local animal experi- mentation and ethics committee to serve as the motorcyclist substitutes. In this ejection motion, the animal rode freely at the motor driver seat and was straightly accelerated by means of our custom motorcyclist ejection injury simulation system. When it was speeded up to the preset velocity （v=30, 40 or 50 km/h） at the preset position, the animal was ejected forward. Pathological and dynamic analyses were conducted, accompanied with the high-speed photograph, acceleration/velocity signal test, gross observation and light microscope examination as well as the abbreviated injury score-injury severity score （AIS-ISS） scale. Results： The high-speed photograph indicated that during the ejection procedure the motorcycle was first arrested and decelerated suddenly, and then the motorcycle driver was ejected forward, accompanied with the rotation motion in the air. Finally, the head, shoulder and thorax of the ejected animal impacted directly on the hard ground. Varying degrees of injury focusing on the liver, heart, lung and spleen were found. There existed a significant positive correlation between ISS and the ejection velocity of the motorcycle drivers （ISS=16.7±2.9 for 30 km/h, 25.0±0.0 for 40 km/h and 37.3±1.0 for 50 km/h）. The detailed injury characteristics were as follows： for the mildly injured animals, there were interlobar gaps or leaf gaps and lobar surface blood coagulation blocks in the liver, and mild lung hemorrhage; for the severely injured animals, there were liver comminuted laceration, moderate lung hemorrhage and heart injury. Animals suffering from the most severe injuries died half an hour later. Conclusion： The new injury model stated in this paper has a high stability and good repeatability, and is likely to be helpful to deeply investigate the injury mechanisms and protection countermeasures of motorcyclist ejection injury.