Biomechanics of acute subdural hematoma.

Acute subdural hematoma (ASDH) due to ruptured bridging veins occurs under acceleration conditions associated with rates of acceleration onset. That this is due to the strain-rate sensitivity of these veins was confirmed in an experimental model of ASDH. The results of this model were consistent with the clinical causes of ASDH, where 72% are due to high-strain falls and assaults and 24% are due to lower strain-rate vehicular injuries. A mathematical model embodying the known mechanical properties of subdural veins was used to develop tolerance criteria for the occurrence of ASDH. This tolerance curve was consistent with the clinical and experimental data but differed from tolerances previously proposed for head injury.