Analysis and measurement of some sources of variability in experimental spinal cord trauma

Experiments were performed on anesthetized cats to determine whether the variability that is common in experimental spinal cord injuries produced by the weight-drop technique can be reduced if a more accurate determination of the actual intensity of the insult to the cord is measured. In addition, determinations of the contribution of such variables as mass of drop-weight, impounder diameter, and animal weight to variability were made. It was found that of the three measures of intensity readily available from a strain gauge transducer, impulse (change in momentum of drop-weight) showed the highest correlation with the histologically determined extent of the lesion. It was shown that the mass of the drop-weight had a significant effect on lesion size even when the gram X centimeter quantification of the injury was constant. Animal weight and impounder diameter did not make a significant contribution to the variability of injury as determined by low-power microscopy.