Acute spinal cord injury in the rat: comparison of three experimental techniques.

Three techniques to produce experimental spinal cord injuries in the rat are compared; 1) the weight dropping method, 2) the aneurysm clip compression method and 3) the extradural balloon compression method. In principle, different forces were used in technique one, while a constant force for different durations is maintained in techniques two and three. The relationship between these different types of injuries and subsequent clinical recovery was assessed quantitatively by the inclined plane method of Rivlin and Tator. The weight dropping technique was found unreliable for experimental spinal cord injury in the rat while the aneurysm clip compression technique resulted in consistent cord injuries with respect to subsequent clinical recovery. The extradural balloon compression method invariably resulted in complete recovery after three and five minutes but no recovery after seven minutes of 0.1 cc air inflated balloon compression of the cord indicating a steep dose--response curve. However, using a 0.2 cc air inflated balloon, no recovery was noted after one minute compression. The major factor in the pathogenesis of spinal cord injury produced by the weight dropping technique is believed to be mechanical, while both mechanical and vascular factors seem to operate in the clip and balloon compression techniques.