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Response and injury severity of the head-neck unit during a low-velocity head impact
Published September 24, 1997 by International Research Council on Biokinetics of Impact in Switzerland
Skull, brain and cervical spine injuries through direct head impacts are reported.
Fourteen head impacts (frontal, lateral or occipital and rigid or padded) with cadavers and 6 padded head impacts by using Hybrid III and EURO-SID dummies at a velocity of 20 km/h were performed. A pneumatic impactor with a movable mass of 23 kg was used; the impact surface was a disc with 150 mm of diameter.
Accelerations at the the top of the head and the epidural pressure at the contre coup site were measured. The impact situation was documented laterally with a high-speed camera of a rate of 1,000 pic/sec.
According to the acceleration measurements at the top of the head the evaluated acceleration at the head c.g. amounts between 70 g (padded) and 160 g (rigid); the rotational acceleration of the head around the rotation axis varies between 2700 rad/sec2 (padded) and 11,000 rad/sec2 (rigid). Furthermore, the epidural pressure is between -20 kPa and -46kPa.
The evaluated resultant acceleration in the center of gravity for padded impacts of the cadavers is in agreement with the values observed for the dummy, whereas the HIC values of the dummy tests are clearly higher than those of the cadavers.
Except for one test, all the rigid impacts show skull fractures. These fractures are located at the impact area and include usually the basis of the skull.
The brain injuries include contre coup subarachnoid hematomas of different size; the hematomas were observed independent of the rigid or padded impact and were found in 54% of the investigated cases. Possible mechanisms for causing of subarachnoid hematomas are interactions between the skull-brain interface.
Skin lacerations were observed in rigid frontal impacts and scalp contusions in occipital rigid head impacts.
It is concluded that padding prevents skull fractures but not brain injuries. Only in two cases the cervical spine was uninjured. Usually, strains of soft tissue and ruptures of ligaments were found.
Response and injury mechanism are critically discussed with those existing in the literature.