The increasing importance of the biomechanics of impact trauma

Abstract

The evolution of experimental biomechanics and crash injury research is summarized briefly to show that they both play a major role in mitigating traffic deaths and injuries. Historically, the subject has been based largely in western countries and thus focused on vehicle occupants, whereas some 80% of traffic casualties in the world are outside the vehicle as pedestrians, cyclists and motorcyclists. The subject is close to the regulatory process which controls vehicle design and is thus heavily influenced by government and industry, yet it is now in an expanding period because of new techniques to replicate the human frame's response to impact forces. New knowledge is likely to emerge from addressing population variations and combining real world accident investigations with experimental biomechanics. The application of impact biomechanics to the vulnerable road users is of particular importance.

The influence of headform orientation and flooring systems on impact dynamics during simulated fall-related head impacts

“…While the exact contact area between headform and flooring surface was not measured in this study, firmer floors (Resilient, Commercial Carpet) would have likely undergone smaller deformations following impact, leading to much smaller contact areas compared to the NCFs tested. Based on animal and cadaveric data, the expanded Prasad-Mertz curves suggest that a HIC score of 1000 is associated with a non-zero risk of a fatal head injury, an 18% probability of severe head injury, a 55% probability of a serious injury, and a 90% probability of moderate head injury for the average adult [25,26]. For impacts at 3.5 m/s onto Commercial Carpet, HIC scores exceeded this threshold (mean (SD) = 1068.0 (40.6)).…”

“…The National Operating Committee on Standards for Athletic Equipment (NOCSAE) has also developed biofidelic headforms, which include a glycerin-filled 'brain cavity' to optimally simulate the behaviour of the human head in response to impact [22,23]. Decades of head impact research have produced risk curves and associated injury thresholds for skull fracture and TBI following impact based on force and acceleration profiles, as well as derived injury criteria such as the Head Injury Criterion (HIC) [24][25][26][27][28]. Simulated head impacts have been widely used to evaluate head injury risk, including during falls on taekwondo mats [29], falls onto playground surfaces [27], and impacts during athletic competition [30].…”

Optimal Material Properties for Mitigating Brain Injury During Head Impact

“…Moreover, once the leading edge of the sphere has passed the critical distance d^, the resistive force (from Eq. (8)) is constant Fit) = (9) In this limit, the acceleration is constant, provided densification is avoided. This is an important limit since, as we show below, it produces the minimum HIC.…”

“…For context, the limit set by the Federal Motor Vehicle Safety Standards for an adult head impacting the interior structure of an automobile at 6.7 m/s (15mph) is 700 [2]. Accordingly, a reduction in HIC from 700 to 700/1.84 « 400 would reduce the probability of serious nonlife-threatening head injury (3 on the Abbreviated Injury Scale) from 25% to 8% [9]. Proportional changes starting from higher baseline HICs would have even greater effect.…”

Assessing motorcycle crash-related head injuries using finite element simulations

“…The HICs for the simulations in cases of the head with and without the helmet are 732 and 12958, respectively. A value of 1000 corresponds to 18 % probability of a severe head injury, a 55 % probability of a serious injury and a 90 % probability of a moderate head injury to the average adult [20]. Fig.…”