Effects of input energy and impactor shape on cranial fracture patterns.

This study documents relationships between input energy, impactor shape, and the formation of fractures in human crania. Parietal impact experiments (n = 12) were performed at 67% higher input energy compared to previously reported experiments. Fracture origins, characteristics, and locations were compared at two input energy levels with three impactor shapes (focal "hammer", flat "brick", and curved "bat"). Impacts with all three impactors at both energy levels produced fractures originating at and remote to the impact site, indicating both mechanisms are typical in temporoparietal blunt force impacts. Higher energy impacts generally produced more impact site fractures, depression, and comminution than lower energy impacts. A small, focal impactor produced cone cracks, depression, and fractures localized near the impact site. A broad, curved impactor produced circumferential fractures and linear fractures extending into adjacent bones. A broad, flat impactor produced fracture patterns ranging from linear fractures to large depressed and comminuted defects.

Experimental investigation of cranial fracture initiation in blunt human head impacts.

The relationship between the point of blunt impact and the location of cranial fracture initiation continues to be poorly understood. The current study used high-speed video to capture cranial fracture initiation and propagation in impact experiments on twelve unembalmed, intact human cadaver heads. Video footage provided direct evidence that blunt cranial impacts can produce linear fractures initiating peripheral to the impact site. Four tests produced only remote peripheral linear fractures with no damage at the known point of impact, demonstrating that the pattern of linear fractures does not necessarily indicate impact site. The range of variation observed in these experiments suggests that cranial fracture formation is more complex than it is typically described in the current literature. Differences in biomechanical and fracture results obtained with three different shaped implements provided evidence that impact surface is one important factor influencing the outcomes of blunt cranial impacts.