Characterisation of soft tissue and skeletal bullet wound trauma and three-dimensional anatomical modelling

Abstract

Effects of firearm projectiles causing injuries to human vital organs were investigated. In this study, the effects of high and medium velocity projectiles on thoracic organs (hearts and lungs) and abdominal organs (livers and kidneys) were investigated using fresh porcine organs and tissue simulants. Furthermore, characteristics of wounds caused by bullets to the cranium, ribs, sternum, vertebrae, scapula and pelvis were analysed. The direction of bullet entry, the manner of death and the mechanisms that caused bone injuries were also determined. A mounted, remotely operated firearm was used to fire a spherical projectile at 900m/s and 500m/s. Doppler radar, infrared sighting screens and high-speed video cameras were used to determine the velocities of the projectiles during their passage through 50mm cubes of fresh porcine lungs, livers, kidneys and hearts, and ballistic tissue simulants. The organs were tested at room (16°C) and core body (37°C) temperature. Time and temperature associated changes in porcine organs were histologically analysed. Two skeletal collections with documented cases of firearm trauma were used for skeletal analyses. Energy loss from projectiles penetrating porcine organs tested at 16°C and 37°C were not significantly different. Histological features of porcine organs did not change during the time of heating from refrigeration to core body temperatures. The energy loss from projectiles penetrating organ simulants at the two tested velocities were different from those measured in porcine organs. This may be the result of differences in densities between the simulants and porcine organs. In skull bones, shape and extent of wounds varied according to the projectile entry energy. Small nicks, circular wounds, or butterfly-like mid-shaft and comminuted fractures were seen in ribs. Injuries in the sternum and ilium were circular in appearance. In the vertebrae, shattering of the vertebral bodies, small fractures and missing segments of the pedicles occurred. Wound characteristics of scapulae varied according to the bone thickness across the scapula. Circular wounds with/without internal bevelling and larger irregularly shaped injuries with/without external bevelling were identified as entry and exit wounds, respectively. High velocity projectiles caused radiating and concentric fractures in brain cases. Skeletal wound characteristics, location and number of wounds, and projectile path allowed the determination of the manner of death. Fracture patterns varied according to the physical properties of bone and projectile entry energy. Re-heating of organs to core body temperature in ballistic research was not necessary. Furthermore, 50mm cubes of organ tissue were adequate to significantly reduce the projectile velocity from entry to exit. New organ simulants with densities similar to soft tissues of human organs or simulants where the density could be altered to match that of the test organ should be used in future ballistic research. Simulants used to represent bone should behave like fresh bone. Accurate information generated by such simulants is of value for the construction of digital programmes or 3D-models to predict how different types of ammunition fired from a variety of firearms cause injury to the human body. They will also be valuable in the development of new ammunitions, firearms, protective body armour and medical treatment of such injuries.