Crash simulation shows helmet protection
6 April 2016. Research at the KTH Royal Institute of Technology in Sweden has shown that bike helmets can reduce the risk of concussions by 54 percent, and drastically cut the risk of skull fractures.
The findings are based on computer-simulated reconstructions of bike crashes in which the riders wore no helmet and sustained head injuries.
Researchers can now apply advanced kinematics to real injury data from medical databases and build advanced crash reconstruction and simulation models.
Remarkably the study showed that helmets would reduce the chance of skull fractures by 98 per cent.
Strain in the brain tissue, which is associated with brain injuries, was reduced by up to 43% for the accident cases studied when a helmet was included.
This resulted in a reduction of the risk of concussion of up to 54%. The stress to the skull bone went from fracture level of 80 megapascals (MPa) down to 13–16 MPa when a helmet was included and the skull fracture risk was reduced by up to 98% based on linear acceleration.
Even with a 10% increased riding velocity for the helmeted impacts, to take into account possible increased risk taking, the risk of concussion was still reduced by up to 46% when compared with the unhelmeted impacts with original velocity.
KTH neuronics researcher Madelen Fahlstedt says the simulations of the crashes—and their impact on the brain—drew upon data from the U.S. National Institutes of Health Visible Human Database, which captures the complex behavior of soft tissues.
"Together with researchers in Leuven, Belgium, we have recreated kinematics of three bike accidents where riders lost control of the situation, fell and hit their head," Fahlstedt said.
"We captured the cyclists' movements during the accidents and then applied the kinematics in terms of speed, just before the blow to the head, on a detailed computer model.”
To assess the impact on the brain, the researchers compared the results of their simulations with CT images, in which bleeding was evident in the brains of the crash victims. Then, they conducted simulations with and without helmets to see what would happen.
"We can see how much the brain tissue is stretched in the collisions, and that the tissue is stretched most in those areas where the impact occurred," she said.
"We saw a great reduction of stress on the bones, as a result of wearing a bike helmet, from 80 megapascals down to 10 megapascals. This figure indicates how much load you put on a given surface, and translated into more understandable terms, this means a reduction from 100-percent risk of skull fracture down to 10 percent for those wearing helmets.”
The researchers said there had been some controversy regarding the effectiveness of helmets in preventing head injuries among cyclists.
Epidemiological, experimental and computer simulation studies have suggested that helmets do indeed have a protective effect, whereas other studies based on epidemiological data have argued that there is no evidence that the helmet protects the brain.
The objective of this study was to evaluate the protective effect of a helmet in single bicycle accident reconstructions using detailed finite element simulations. The results of this study show that the brain injury risk and risk of skull fracture could have been reduced in these three cases if a helmet had been worn.
Madelen Fahlstedt et al. The protective effect of a helmet in three bicycle accidents—A finite element study, Accident Analysis & Prevention (2016).
