Study hypothesis: Information on the influence of the mass of the helmet on the pattern of head injuries suffered by motorcyclists involved in collisions is scarce. This study was undertaken to verify a possible connection between the weight of the helmet worn and the occurrence of a ring fracture of the base of the skull surrounding the foramen magnum.
Design: One hundred twenty-two fatally injured motorcyclists were studied retrospectively. In all cases, an autopsy had been performed. Data, including the autopsy report, were obtained from official police files. All helmets were studied in a technical laboratory. Statistical tests were performed using ANOVA, Fisher's exact test, Student's t test, and the chi 2 test. A p < 0.05 was considered significant.
Results: The overall incidence of this type of injury was 9.2%. There was a positive correlation between the incidence of complete or partial circular fractures of the base of the skull and the weight of the involved helmet. There was a significant increase (p = 0.012) in the incidence of this type of fracture when the helmet weighed more than 1,500 grams. An increase in the dynamic active mass caused by the combination of head and helmet leads to a supramaximal stress load during a collision, resulting in such injuries.
Conclusions: In accidents with axial load shift, helmets weighing more than 1,500 grams increase the risk of a basal skull fracture. Therefore high-weight helmets should be avoided.