Photoelastic Analysis of Intracranial Stress Distribution under Impact Loading to the Head

Aim: To investigate the injury characteristics and the cause of craniocerebral impact injury. Methods: Clinical data from a total of 265 cases with severe closed craniocerebral injury were used to analyze the common injury regions and injury patterns, and craniocerebral photo-elastic models were developed to estimate the intracranial stress distribution due to impact loading of the head. Results: Clinical data showed that the most common injured regions were the parietal, temporal, occipital and frontal areas, and a range of injury was observed in these regions. Impacting the photo-elastic craniocerebral models revealed stress concentrations in the cranial bone, first at the impact site, followed by new areas of stress concentration due to the propagation of stress waves across the cranial bone and the brain tissues to areas remote from the site of impact. When the frontal and parietal regions were impacted, the stress waves propagated relatively farther. But when the occipital and temporal parts were impacted, the stress concentration was usually limited to areas near the impacted site. Conclusion: The injury mechanisms of the frequently injured regions on the brain, such as the frontal, temporal, occipital and parietal regions were found to be different. Frontal and parietal impacts, caused intracranial stress waves to propagate relatively farther into the brain. Also, stress concentration could cause injury to the parietal bone, frontal process, nasal bone and middle cranial fossa or diencephalon because of coarse inner surface with sharp prominency and sharp edge in the parietal and frontal region where the irregular anatomical structure facilitated multi-directional stress wave reflections in the parietal region and precranial fossa. Temporal and occipital impacts usually resulted in injuries to areas near the site of loading because of the smooth outer and inner surfaces of the occipital bone and a weak temporal bone.