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.