[Gunshot injury of the spinal cord]

108 pigs were shot at the level of lumbar 1 to investigate the changes of spinal cord in relation to the speed of shooting and the trajectory through which the bullet passed. The cord lesions of the specimens could be divided, according to its severity, into 4 grades: (1) transection in 41; (2) complete destruction in 43; both lesion 1&2 resulted in permanent paraplegia; (3) incomplete destruction in 13, those resulted in incomplete paraplegia eventually recovered; (4) mild damage, that was concussion in 11, resumed perfectly. Through a transducer sealed into the spinal canal, the intracanal pressure was recorded: (1) Shooting through spinal canal with a pressure over 5 kg caused cord transection. (2) shooting through canal wall with a pressure of 2.5 to 5; 0 kg caused complete cord destruction. (3) shooting nearby the outer margin of vertebra with a pressure less than 1.0 kg caused mild cord damage. It was found that the speed of bullet, the trajectory with relation to cord and the grade of cord lesion are in agreement with each other. The mutual effects among them would make one think it reasonable to classify cord injury as follows: 1. Injury from bullet through spinal canal or vertebral body usually causes cord transaction; 2. Injury from bullet through canal wall at high speed would make a chance of complete destruction in 94%; at low speed, a chance of either complete or incomplete lesion in 50% each. 3. Injury nearby vertebra, high speed bullet would cause a chance of complete cord lesion in 86%; low speed one would make a chance of incomplete lesion in 1/3 and mild lesion in 2/3.