Characterization of an experimental spinal cord injury model using waveform and morphometric analysis

Study Design. A weight-drop device based on a displacement transducer and feedback detection circuitry was designed to produce consistent experimental spinal cord injuries in a rat model. The device was characterized and evaluated based on biomechanical parameters, quantitative histology, and neurologic behavior. Objective. To develop, characterize, and evaluate a spinal cord injury device for use in animal models. Summary of Background data. The biomechanical parameters of spinal cord injury, including compression, velocity, force, energy, impulse-momentum, and power, can be derived from the displacement waveform. It has been shown that the magnitude and variability of certain of these injury parameters are correlated with lesion size and neurologic deficit. Methods. Two groups of six male Sprague-Dawley rats were injured using the device an their injury displacement waveforms digitally recorded on a personal computer equipped with a data acquisition board. Group 1 animals were sacrificed immediately after injury. Quantitative morphometric and numerical analyses were performed on histologic specimens and injury waveforms, respectively. Biomechanical injury parameters were compared with histologic and behavioral measures of injury. Results. All kinetic injury parameters were reproducible to within standard deviations of less than +/-22%, whereas spinal cord displacement variability was +/-29%. Motor scores for animals on day 14 animals were 4.3 +/- 0.4, whereas lesion sizes were much more variable, exhibiting percent volumes of 5.5 +/- 2.5 immediately after injury, and 11.9 +/- 7.1 on day 14. Conclusion. This device should benefit studies of experimental spinal cord injury in animals by reducing interanimal variations in injury severity, especially in the acute phase of injury.