Spinal cord contusion in the rat: production of graded, reproducible, injury groups.

A weight drop technique was used to produce a contusive injury of the spinal cord in the rat. A restricted laminectomy was carried out at T8 and the spinal column stabilized by clamps attached to the spinous processes of adjacent vertebrae. A 2.4-mm-diameter impounder was lowered onto the dura and a 10-g weight dropped 0.0, 2.5, 5.0, 7.5, 10.0, or 17.5 cm onto the impounder. The functional deficit was assessed for 4 weeks after injury and the spinal cord tissue processed for histopathologic analysis. The results indicated that groups of rats (N = 10) subjected to the weight dropped from increasing heights exhibited a graded final functional deficit as measured by scores on a modified Tarlov scale or the mean angle attained in the inclined plane test of Rivlin and Tator. Histopathologic results also indicated the production of graded lesions. Three groups of experimental animals were statistically distinguished corresponding to those with mild, moderate, or severe final functional deficit. The average functional deficit in these injury groups, produced by dropping the weight 2.5, 5.0, or 17.5 cm, respectively, was reproducible in replicate experiments. This model of spinal cord contusion in the rat may be useful in screening putative therapeutic drug regimens for subsequent clinical trials on different groups of patients with spinal cord injury.