A Strain Energy Approach to the Mechanics of Skull Fracture

The mechanics of skull fracture in humans has been investigated by many people for over 90 years. A variety of techniques has been used in past studies. Test specimens have been whole cadavers, cadaver heads, skulls and sections of skulls with material conditions including both fresh and embalmed tissue, both dried and moist. Test techniques have incorporated cadaver drop tests, drop towers, and universal testing machines with the impacting surfaces including large surfaces, both flat and curved, and localized flat and curved surfaces. Some of the studies used impact energy as the measured test parameter, others used impact load and some studies used both quantities to describe the impact.

The results of recent studies on the mechanical properties of cranial bone suggest that local values of strain energy density present in the bone of an impacted skull may be the critical parameter in the initiation of skull fracture. It is the purpose of this paper to summarize the results of the large body of information on the phenomenology of skull fracture and then to analyze the results in terms of local strain energy density considerations. Based on this reasoning, the differences and similarities between the results of the many different studies are discussed in a qualitative manner. Conclusions are drawn on the influences of such factors as impactor size and shape, skull geometry, and soft tissue effects.