Darrin Richards

Bicycle helmets are highly effective at preventing head injury during head impact: Head-form accelerations and injury criteria for helmeted and unhelmeted impacts

Cycling is a popular form of recreation and method of commuting with clear health benefits. However, cycling is not without risk. In Canada, cycling injuries are more common than in any other summer sport; and according to the US National Highway and Traffic Safety Administration, 52,000 cyclists were injured in the US in 2010. Head injuries account for approximately two-thirds of hospital admissions and three-quarters of fatal injuries among injured cyclists. In many jurisdictions and across all age levels, helmets have been adopted to mitigate risk of serious head injuries among cyclists and the majority of epidemiological literature suggests that helmets effectively reduce risk of injury. Critics have raised questions over the actual efficacy of helmets by pointing to weaknesses in existing helmet epidemiology including selection bias and lack of appropriate control for the type of impact sustained by the cyclist and the severity of the head impact. These criticisms demonstrate the difficulty in conducting epidemiology studies that will be regarded as definitive and the need for complementary biomechanical studies where confounding factors can be adequately controlled. In the bicycle helmet context, there is a paucity of biomechanical data comparing helmeted to unhelmeted head impacts and, to our knowledge, there is no data of this type available with contemporary helmets. In this research, our objective was to perform biomechanical testing of paired helmeted and unhelmeted head impacts using a validated anthropomorphic test headform and a range of drop heights between 0.5m and 3.0m, while measuring headform acceleration and Head Injury Criterion (HIC). In the 2m (6.3m/s) drops, the middle of our drop height range, the helmet reduced peak accelerations from 824g (unhelmeted) to 181g (helmeted) and HIC was reduced from 9667 (unhelmeted) to 1250 (helmeted). At realistic impact speeds of 5.4m/s (1.5m drop) and 6.3m/s (2.0m drop), bicycle helmets changed the probability of severe brain injury from extremely likely (99.9% risk at both 5.4 and 6.3m/s) to unlikely (9.3% and 30.6% risk at 1.5m and 2.0m drops respectively). These biomechanical results for acceleration and HIC, and the corresponding results for reduced risk of severe brain injury show that contemporary bicycle helmets are highly effective at reducing head injury metrics and the risk for severe brain injury in head impacts characteristic of bicycle crashes.

Towards clinical management of traumatic brain injury: a review of models and mechanisms from a biomechanical perspective

Traumatic brain injury (TBI) is a major worldwide healthcare problem. Despite promising outcomes from many preclinical studies, the failure of several clinical studies to identify effective therapeutic and pharmacological approaches for TBI suggests that methods to improve the translational potential of preclinical studies are highly desirable. Rodent models of TBI are increasingly in demand for preclinical research, particularly for closed head injury (CHI), which mimics the most common type of TBI observed clinically. Although seemingly simple to establish, CHI models are particularly prone to experimental variability. Promisingly, bioengineering-oriented research has advanced our understanding of the nature of the mechanical forces and resulting head and brain motion during TBI. However, many neuroscience-oriented laboratories lack guidance with respect to fundamental biomechanical principles of TBI. Here, we review key historical and current literature that is relevant to the investigation of TBI from clinical, physiological and biomechanical perspectives, and comment on how the current challenges associated with rodent TBI models, particularly those involving CHI, could be improved.

Head injury in snowboarding: evaluating the protective role of helmets

According to a 1999 report by the U.S. Consumer Product Safety Commission, head injuries represent approximately 14 % of all skiing and snowboarding injuries. In a recent retrospective study of patients treated for snowboarding-related head injuries, Nakaguchi and Tsutsumi (2002) found that major head injuries were most often associated with backward falls (68 %) resulting in occipital impacts (66 % of falls) occurring on a gentle or moderate slope. They concluded that the majority of severe snowboarding head injuries were caused by the “opposite-edge phenomenon” where the snowboarder falls backward and contacts the occiput. In order to determine if the use of skiing helmets would reduce the likelihood of head injury associated with catching an edge snowboarding, we conducted a two-part study. In the first part, we measured the speeds of over 180 snowboarders on beginner and intermediate slopes at Mammoth, CA. Across all locations at the resort, the average speeds of beginner and intermediate snowboarders were 17.7 kph (11.0 mph) and 31.9 kph (19.8 mph), respectively. In the second part of the study, we used an instrumented 50th percentile male Hybrid III anthropomorphic test device (ATD) to determine the head accelerations and neck loads associated with a backward fall onto the occiput, both with and without wearing a helmet. For these tests, the ATD was fitted with snowboarding equipment and accelerated to the speeds associated with an intermediate snowboarder (as measured in the first part of the study). Once the ATD was at speed, the snowboard was snubbed on the back edge, simulating the “opposite-edge phenomena” and the posterior aspect of the ATD head was propelled toward the snow surface or a simulated tree. Film analysis of the ATD fall kinematics demonstrated a rapid transition to whole-body angular motion at opposite edge catch. The use of a helmet reduced substantially the linear accelerations and head injury criterion associated with head-to-ground contact on hard, icy snow and during the simulated tree contact. Also, the neck loads were reduced modestly with helmet use. These findings indicate that helmets can mitigate head-to-ground contact severity associated with a common snowboarding fall scenario, the “opposite-edge-phenomenon.”

Electromyographic activity and posturing of the human neck during rollover tests

Lateral head motions, torso motions, lateral neck bending angles, and electromyographic (EMG) activity patterns of five human volunteer passengers are compared to lateral motions of a Hybrid III ATD during right-left and left-right fishhook steering maneuvers leading to vehicular tip-up. While the ATD maintained relatively fixed lateral neck angles, live subjects leaned their heads slightly inward and actively utilized their neck musculature to stiffen their necks against the lateral inertial loads. Except for differences in neck lateral bending, the Hybrid III ATD reasonably reflects occupant kinematics during the pre-trip phase of on-road rollovers.

Evaluation of Human Surrogate Models for Rollover

Anthropomorphic test dummies (ATDs) have been validated for the analysis of various types of automobile collisions through pendulum, impact, and sled testing. However, analysis of the fidelity of ATDs in rollover collisions has focused primarily on the behavior of the ATD head and neck in axial compression. Only limited work has been performed to evaluate the behavior of different surrogate models for the analysis of occupant motion during rollover. Recently, Moffatt et al. examined head excursions for near- and far-side occupants using a laboratory-based rollover fixture, which rotated the vehicle about a fixed, longitudinal axis. The responses of both Hybrid III ATD and human volunteers were measured. These experimental datasets were used in the present study to evaluate MADYMO ATD and human facet computational models of occupant motion during the airborne phase of rollover. Occupant motion predicted by the Hybrid III ATD computation models provided a good match to the temporal movement patterns and corridors of torso and head excursion measured in the volunteers. Differences in torso and head-neck posture were attributed to active muscle contractions in the volunteers. Simulations performed using the TNO human facet model, in the absence of muscle tone, predicted large head excursions and lateral neck and torso bending. These findings were attributed to the stiffer Hybrid III ATD neck and torso as compared to the spinal model incorporated in the human facet model. Although it is possible to model active muscle forces using the TNO human facet model, the appropriate control schemes for coordinating muscle activity in the rollover environment have not been established. Without the implementation of appropriate muscular controls, the TNO human model appears to be best suited to high-force environments or low-force environments where the occupant is unconscious or incapacitated. Our results indicate that among the currently available human computational surrogate models, the Hybrid III ATD provides the best prediction of occupant motion when compared to the available human volunteer data. These results have provided us the impetus to study future human models that incorporate active muscle control.

Development of a computational method to predict occupant motions and neck loads during rollovers

The mechanics of on-road, friction-induced rollovers were studied with the aid of a three-dimensional computer code specifically derived for this purpose. Motions of the wheels, vehicle body, occupant torso, and head were computed. Kanes method was utilized to develop the dynamic equations of motion in closed form. On-road rollover kinematics were compared to a dolly-type rollover at lesser initial speed, but generating a similar roll rotation rate. The simulated on-road rollover created a roof impact on the leading (drivers) side, while the dolly rollover simulation created a trailing-side roof impact. No head-to-roof contacts were predicted in either simulation. The first roof contact during the dolly-type roll generated greater neck loads in lateral bending than the on-road rollover. This work is considered to be the first step in developing a combined vehicle and occupant computational model for studying injury potential during rollovers.

Head and Neck Injury Potential With and Without Helmets During Head-First Impacts on Snow

Terrain parks and jumping features at ski resorts have become increasingly popular with skiers and snowboarders over the past decade. If a jumper were to land incorrectly, such as in an inverted posture where one lands on their head, the consequences can be devastating and can result in cervical spine fractures or dislocations and serious spinal cord injury. The objective of this study was to assess the potential for serious neck injury in head-first impacts onto snow surfaces with and without helmets. We conducted six paired head-first impact drop tests, with and without helmets on snow that varied from soft to hard. Drop tests were carried out with a head and neck assembly from a Hybrid III anthropomorphic test device using a custom designed drop carriage. The impact speed was 4.0 ± 0.1 m/s, representing an equivalent fall height of 0.82 m. The head was instrumented with three uniaxial accelerometers located at the center-of-gravity and a six-axis load cell was located at the upper neck. The results indicated that the helmets provided good head protection in the hard snow impacts, reducing head accelerations by as much as 48 %. Head accelerations were low in soft snow impacts both with and without a helmet. Overall, helmets were not an effective countermeasure to high neck loads, although a minor reduction was noted in the soft snow impacts. All tests resulted in neck loads that exceeded the injury assessment reference values for the neck. Notably in the hard snow impacts, the neck loads were more than double the injury assessment reference values for all tests. Because of the susceptibility of the neck to injury at the relatively low drop heights that we tested, efforts to prevent neck injuries should focus on education and training to avoid head-first impact. KEYWORDS: head injury, neck injury, head-first impact, helmet, anthropomorphic test device, snow impact Language: en

Injuries at the Whistler Sliding Center: a 4-year retrospective study

Background The Whistler Sliding Centre (WSC) in British Columbia, Canada, has played host to many events including the 2010 Winter Olympics. This study was performed to better understand sliding sport incident (crash, coming off sled, etc) and injury prevalence and provide novel insights into the effect of slider experience and track-specific influences on injury risk and severity. Methods Track documentation and medical records over 4 years (2007 track inception to 2011) were used to form 3 databases, including over 43 200 runs (all sliding disciplines). Statistics were generated relating incident and injury to start location, crash location and slider experience as well as to understand injury characteristics. Results Overall injury rate was found to be 0.5%, with more severe injury occurring in <0.1% of the total number of runs. More frequent and severe injuries were observed at lower track locations. Of 2605 different sliders, 73.6% performed 1–29 runs down the track. Increased slider experience was generally found to reduce the frequency of injury. Lacerations, abrasions and contusions represented 52% of all injuries. A fatality represented the most severe injury on the track and was the result of track ejection. Conclusions By investigating the influence of start location, incident location and slider experience on incident and injury frequency and severity, a better understanding has been achieved of the inherent risks involved in sliding sports. Incident monitoring, with particular focus on track ejection, should be an emphasis of sliding tracks.

Ice hockey shoulder pad design and the effect on head response during shoulder-to-head impacts

Abstract Ice hockey body checks involving direct shoulder-to-head contact frequently result in head injury. In the current study, we examined the effect of shoulder pad style on the likelihood of head injury from a shoulder-to-head check. Shoulder-to-head body checks were simulated by swinging a modified Hybrid-III anthropomorphic test device (ATD) with and without shoulder pads into a stationary Hybrid-III ATD at 21 km/h. Tests were conducted with three different styles of shoulder pads (traditional, integrated and tethered) and without shoulder pads for the purpose of control. Head response kinematics for the stationary ATD were measured. Compared to the case of no shoulder pads, the three different pad styles significantly (p < 0.05) reduced peak resultant linear head accelerations of the stationary ATD by 35–56%. The integrated shoulder pads reduced linear head accelerations by an additional 18–21% beyond the other two styles of shoulder pads. The data presented here suggest that shoulder pads can be designed to help protect the head of the struck player in a shoulder-to-head check.