Effectiveness of Safety Helmets for Motorcyclists: An Analysis of 158 Fatally Injured Cases in South Australia

• Published in: Nihon Kyukyu Igakukai Zasshi 1998/08/15, Vol.9(8), pp.325-331
• Main Authors: Murakami, Shigeyuki, McLean, A.J., Blumbergs, P.C., Nakamura, Norio, Tani, Satoshi, Takekawa, Mitsuru, Abe, Toshiaki
• Format: Article
• Language: English
• Subjects: diffuse axonal injury; head injury; helmet; motorcyle; skull fructure
• ISSN: 0915-924X; 1883-3772
• DOI: 10.3893/jjaam.9.325

This paper is intended as an investigation of the effectiveness of protective helmets for motorcyclists. Three hundred and two motorcyclists were killed in South Australia during the 9-year period from 1983 to 1991. One hundred and fifty-eight fatally injured cases have been investigated by the National Health and Medical Research Council (NHMRC) Road Accident Research Unit. The average age of the riders was 25.6 years, and 72% were 16 to 29 years of age. The driver's blood alcohol level was known in 132 cases. Half had been drinking and 72% of that group had a blood alcohol level above 0.08g/100ml, which was the legal limit for drivers and motorcyle riders at that time, with the highest reading being 0.275. The cases were divided into two groups according to helmet usage and retention in the crash: (1) the ‘ON’ group, in which the helmet was worn throughout the accident (95 cases); and (2) the ‘OFF’ group, in which the helmet was not worn or had come off during the accident (41 cases). The proportion of cases in which head injury was a cause of death in the ‘OFF’ group was larger than that in the ‘ON’ group (p=0.0031). Skull fracture occurred more frequently in the ‘OFF’ group (p=0.0439). Although some intracranial lesions, such as cerebral contusion, damage of the corpus callosum, subarachnoid hemorrhage, acute epidural hematoma and brain swelling, also occurred more frequently in the ‘OFF’ group, there was no statistically significant difference in the frequency of diffuse axonal injury between the two groups. These results suggest that the hard shell of the helmet reduced deformation of the skull, resulting in a lower incidence of skull fractures. Also, in general, acute subdural hematomas or brain contusions are more likely to occur with a shorter duration of acceleration while diffuse brain injury is more likely with the longer duration. The buffering effect of the helmet liner at the impact point may effectively prolong the duration of acceleration. Thus, it is possible that an impact which could produce a focal injury such as acute subdural hematoma or brain contusion is reduced to one causing a diffuse brain injury. The role of helmet use in the attenuation of diffuse axonal injury is the subject of continuing investigation.