Comparison of Ice Hockey Goaltender Helmets for Concussion Type Impacts

Concussions are among the most common injuries sustained by ice hockey goaltenders and can result from collisions, falls and puck impacts. However, ice hockey goaltender helmet certification standards solely involve drop tests to a rigid surface. This study examined how the design characteristics of different ice hockey goaltender helmets affect head kinematics and brain strain for the three most common impact events associated with concussion for goaltenders. A NOCSAE headform was impacted under conditions representing falls, puck impacts and shoulder collisions while wearing three different types of ice hockey goaltender helmet models. Resulting linear and rotational acceleration as well as maximum principal strain were measured for each impact condition. The results indicate that a thick liner and stiff shell material are desirable design characteristics for falls and puck impacts to reduce head kinematic and brain tissue responses. However for collisions, the shoulder being more compliant than the materials of the helmet causes insufficient compression of the helmet materials and minimizing any potential performance differences. This suggests that current ice hockey goaltender helmets can be optimized for protection against falls and puck impacts. However, given collisions are the leading cause of concussion for ice hockey goaltenders and the tested helmets provided little to no protection, a clear opportunity exists to design new goaltender helmets which can better protect ice hockey goaltenders from collisions.     

枪弹冲击下新型防弹头盔质量对颈椎损伤影响

目的建立有效的头颈部及防弹头盔有限元模型,研究枪弹冲击不同质量防弹头盔时颈部的生物力学响应。方法通过在头盔本体(1.24 kg)增加附件均布质量2 kg,并加载手枪弹以450 m/s速度从正面、侧面、顶部冲击防弹头盔,获得人体颈椎的力学响应。结果受到冲击时,颈椎应力远大于颅骨应力。枪弹冲击防弹头盔时,相比头部,颈椎为易受伤部位,其中椎骨C3所受应力最大。不考虑增加附件质量时,子弹从正面、侧面、顶部方向冲击头盔时,侧面冲击对颈椎伤害最大,相比其他方向冲击最大应力约增加2.58%;同时正面冲击对头部损伤最大,应力约增加59.4%。考虑附件质量时,头盔质量越大对颈椎的损伤越严重。头盔质量从1.24 kg增加到3.24 kg,顶部冲击对颈椎的损伤最大,其应力相比其他方向冲击增加12.98%。结论在设计防弹头盔时应考虑其轻量化,研究结果为防弹头盔设计提供科学参考。     

Determination of the 4 mm Gamma Knife helmet relative output factor using a variety of detectors

Though the 4 mm Gamma Knife helmet is used routinely, there is disagreement in the Gamma Knife users community on the value of the 4 mm helmet relative output factor. A range of relative output factors is used, and this variation may impair observations of dose response and optimization of prescribed dose. To study this variation, measurements were performed using the following radiation detectors: silicon diode, diamond detector, radiographic film, radiochromic film, and TLD cubes. To facilitate positioning of the silicon diode and diamond detector, a three-dimensional translation micrometer was used to iteratively determine the position of maximum detector response. Positioning of the films and TLDs was accomplished by manufacturing custom holders for each technique. Results from all five measurement techniques indicate that the 4 mm helmet relative output factor is 0.868 +/- 0.014. Within the experimental uncertainties, this value is in good agreement with results obtained by other investigators using diverse techniques.     

A national survey about parent awareness of the risk of severe brain injury from playing football

A survey was conducted to determine the level of awareness among parents of high school football players about the risk of severe brain injury. A national sample of 1007 randomly selected households was interviewed by telephone during February, 1992. All interviewees were parents of high school football players who either were currently playing football or had played within the previous 5 years. Survey questions measured the extent to which parents were aware both of the risks associated with playing high school football and the existing helmet warnings about those risks. Overall, the survey results demonstrated that parents of high school football players were uninformed about both the risk of severe brain injury from playing high school football and the football helmet warnings about that risk. Specifically, unprompted, most parents mentioned broken bones, knee injuries, sprains, or shoulder injuries as hazards associated with playing football. Few parents mentioned severe brain damage, even when prompted. Further, the overwhelming majority of parents incorrectly believed that wearing a football helmet generally eliminated the risk of severe brain injury. Very few parents had received information from any source about the risks of head injury or had heard that no football helmet can provide complete protection against this hazard. Few parents were aware of the warning label on the helmet or knew what the label said, even when prompted. In short, parents were unaware of the risk of severe brain damage, misinformed about a football helmet's ability to protect against this risk, and uninformed about the football helmet warning label about this risk.     

气囊式头盔防护下的两轮车骑车人头部损伤风险分析

目的 提出一种气囊式头盔缓冲内衬结构,并分析其对两轮车骑车人头部损伤的防护效果。方法 将气囊式内衬应用于自行车（半盔）和摩托车（全盔）两款典型的两轮车骑车人头盔,通过标准GB 24429-2009和法规ECE R22.05测试工况下的有限元碰撞仿真,获得人体头部模型运动学和生物力学响应,从颅骨骨折和颅脑损伤风险角度对比常规聚苯乙烯泡沫塑料（expanded polystyrene, EPS）头盔,综合评价气囊式头盔的防护性能。结果 当气囊压力为0.06 MPa时,气囊式头盔（半盔/全盔）防护下的人体头部颅骨骨折相关量分别小于120 g和150 g,颅骨骨折风险基本低于40%;颅脑最大主应变均小于0.3,轻度脑损伤风险均低于25%;气囊式头盔防护下的人体颅骨骨折和颅脑损伤风险均低于EPS头盔。结论 本文设计的气囊式头盔具有较好的防护效果,能兼顾颅骨骨折和颅脑损伤防护,可以为新型头盔的设计提供基础示例。损伤风险分析也可为骑车人头部损伤应急诊断提供初步参考。     

An efficient method of measuring the 4 mm helmet output factor for the Gamma knife

It is essential to have accurate measurements of the 4 mm helmet output factor in the treatment of trigeminal neuralgia patients using the Gamma Knife. Because of the small collimator size and the sharp dose gradient at the beam focus, this measurement is generally tedious and difficult. We have developed an efficient method of measuring the 4 mm helmet output factor using regular radiographic films. The helmet output factor was measured by exposing a single Kodak XV film in the standard Leksell spherical phantom using the 18 mm helmet with 30-40 of its plug collimators replaced by the 4 mm plug collimators. The 4 mm helmet output factor was measured to be 0.876 +/- 0.009. This is in excellent agreement with our EGS4 Monte Carlo simulated value of 0.876 +/- 0.005. This helmet output factor value also agrees with more tedious TLD, diode and radiochromic film measurements that were each obtained using two separate measurements with the 18 mm helmet and the 4 mm helmet respectively. The 4 mm helmet output factor measured by the diode was 0.884 +/- 0.016, and the TLD measurement was 0.890 +/- 0.020. The radiochromic film measured value was 0.870 +/- 0.018. Because a single-exposure measurement was performed instead of a double exposure measurement, most of the systematic errors that appeared in the double-exposure measurements due to experimental setup variations were cancelled out. Consequently, the 4 mm helmet output factor is more precisely determined by the single-exposure approach. Therefore, routine measurement and quality assurance of the 4 mm helmet output factor of the Gamma Knife could be efficiently carried out using the proposed single-exposure technique.     

Localization of cerebral arterovenous malformations using digital angiography

Since 1989 we performed stereotactic radiotherapy treatments of cerebral arterovenous malformations (AVM), estimating three-dimensional (3-D) localization and shape of target volumes by the Leksell stereotactic helmet on two orthogonal radiographic projections. Due to the limitations of this method, we developed a new technique for the localization of the target volume using digital subtraction angiography (DSA) and digital image processing. To achieve this result we first developed a method to correct nonlinear distortion of DSA images using spatial relocation of image pixels based on a calibration grid. We then developed an algorithm for localization of the target volume using two independent DSA projections. Target volume coordinates in the helmet system are calculated using two DSA acquisitions taken with a free angle (approximately 90 degrees), one in the AP and the other in the LL direction. The helmet can be freely positioned between the x-ray source and the image plane. The projections of eight reference points inserted in the helmet at a known location, are used to calculate the transformation matrix between the two coordinate systems. We performed numerical and experimental validation of the system. A hypothetical random error (up to 2 mm) on image coordinates of the reference points allowed to determine that the error in target localization was less than 0.2 mm. Using DSA images of target points with a known location within a phantom, the error between calculated and actual location was, on average, 0.30+/-0.13 mm (mean+/-SD), with a maximum error of 0.49 mm. The results of numerical and experimental validations show that the system we have developed allows fast and accurate localization of the center of the target volume and it is suitable for efficient guiding during stereotactic radiosurgery of AVM.     

Effects of Football Collars on Cervical Hyperextension and Lateral Flexion

OBJECTIVES: To evaluate the effectiveness of 3 football collars in reducing cervical range of motion. DESIGN AND SETTING: A repeated-measures design in a controlled laboratory setting. SUBJECTS: Fifteen male National Collegiate Athletic Association Division I varsity football athletes. MEASUREMENTS: Cervical hyperextension and lateral flexion were measured with video analysis. Subjects underwent 5 testing conditions: standard football helmet, standard helmet and shoulder pads, and standard pads with the addition of the Cowboy Collar, A-Force Neck Collar, or a foam neck roll. Subjects performed motions both actively and passively. RESULTS: All 3 collars reduced hyperextension when compared with the helmet and shoulder pads alone (P <.05); in addition, the Cowboy Collar was superior to the foam neck roll (P <.05) in reducing hyperextension. No collar reduced passive lateral flexion when compared with the helmet and shoulder pads, but the foam neck roll permitted significantly less active lateral flexion (P <.01) than the other 3 brace conditions. CONCLUSIONS: In a laboratory setting, cervical hyperextension can be controlled through the use of various cervical collars. Cervical lateral flexion (a more common cause of burners in a scholastic population) cannot be controlled with any of the cervical collars tested. Moreover, foam collars may impede active lateral flexion while not providing additional protection when loaded. These results are limited in that they were produced in a controlled situation as opposed to active football play.     

Wearing a bike helmet leads to less cognitive control,revealed by lower frontal midline theta power and risk indifference

A recent study claims that participants wearing a bike helmet behave riskier in a computer‐based risk task compared to control participants without a bike helmet. We hypothesized that wearing a bike helmet reduces cognitive control over risky behavior. To test our hypothesis, we recorded participants' EEG brain responses while they played a risk game developed in our laboratory. Previously, we found that, in this risk game, anxious participants showed greater levels of cognitive control as revealed by greater frontal midline theta power, which was associated with less risky decisions. Here, we predicted that cognitive control would be reduced in the helmet group, indicated by reduced frontal midline theta power, and that this group would prefer riskier options in the risk game. In line with our hypothesis, we found that participants in the helmet group showed significantly lower frontal midline theta power than participants in the control group, indicating less cognitive control. We did not replicate the finding of generally riskier behavior in the helmet group. Instead, we found that participants chose the riskier option in about half of trials, no matter how risky the other option was. Our results suggest that wearing a bike helmet reduces cognitive control, as revealed by reduced frontal midline theta power, leading to risk indifference when evaluating potential behaviors.     

Effect of helmet liner systems and impact directions on severity of head injuries sustained in ballistic impacts: a finite element (FE) study

The current study aims to investigate the effectiveness of two different designs of helmet interior cushion, (Helmet 1: strap-netting; Helmet 2: Oregon Aero foam-padding), and the effect of the impact directions on the helmeted head during ballistic impact. Series of ballistic impact simulations (frontal, lateral, rear, and top) of a full-metal-jacketed bullet were performed on a validated finite element head model equipped with the two helmets, to assess the severity of head injuries sustained in ballistic impacts using both head kinematics and biomechanical metrics. Benchmarking with experimental ventricular and intracranial pressures showed that there is good agreement between the simulations and experiments. In terms of extracranial injuries, top impact had the highest skull stress, still without fracturing the skull. In regard to intracranial injuries, both the lateral and rear impacts generally gave the highest principal strains as well as highest shear strains, which exceed the injury thresholds. Off-cushion impacts were found to be at higher risk of intracranial injuries. The study also showed that the Oregon Aero foam pads helped to reduce impact forces. It also suggested that more padding inserts of smaller size may offer better protection. This provides some insights on future’s helmet design against ballistic threats.     

Helmet-based physiological signal monitoring system

A helmet-based system that was able to monitor the drowsiness of a soldier was developed. The helmet system monitored the electrocardiogram, electrooculogram and electroencephalogram (alpha waves) without constraints. Six dry electrodes were mounted at five locations on the helmet: both temporal sides, forehead region and upper and lower jaw strips. The electrodes were connected to an amplifier that transferred signals to a laptop computer via Bluetooth wireless communication. The system was validated by comparing the signal quality with conventional recording methods. Data were acquired from three healthy male volunteers for 12 min twice a day whilst they were sitting in a chair wearing the sensor-installed helmet. Experimental results showed that physiological signals for the helmet user were measured with acceptable quality without any intrusions on physical activities. The helmet system discriminated between the alert and drowsiness states by detecting blinking and heart rate variability (HRV) parameters extracted from ECG. Blinking duration and eye reopening time were increased during the sleepiness state compared to the alert state. Also, positive peak values of the sleepiness state were much higher, and the negative peaks were much lower than that of the alert state. The LF/HF ratio also decreased during drowsiness. This study shows the feasibility for using this helmet system: the subjects’ health status and mental states could be monitored without constraints whilst they were working.     

Monte Carlo calculated output factors of a Leksell Gamma Knife unit

The Leksell Gamma Knife is a standard radiosurgical tool for treating brain lesions by directing beams of gamma radiation to a specific region. The diameter of the gamma beams is confined by collimator systems and available collimator sizes are 4, 8, 14 and 18 mm. The reduction in dose rate for each collimator helmet is called the output factor (OPF). Experimental determination of OPFs is difficult due to the extremely narrow beams for which the dose is determined. In the present work, the PRESTA version of the EGS4 Monte Carlo code was used to obtain relative OPFs for the Leksell Gamma Knife for collimator sizes of 14, 8 and 4 mm (relative to that of the 18 mm collimator). A spherical probe with a radius of 1 mm was utilized in this computer experiment. Our Monte Carlo results gave OPFs of 0.974, 0.951 and 0.872 for the 14 mm, 8 mm and 4 mm collimators respectively, relative to the 18 mm collimator. Our calculated OPF for the 4 mm collimator helmet was more than 8% higher than the value currently used, but in good agreement with the average of experimental values obtained by various Gamma Knife centres throughout the world and with the value now recommended by the manufacturer, Elekta (Elekta Instrument AB, Skeppargatan 8, S-114 52 Stockholm, Sweden).     

A discussion of the issue of football helmet removal in suspected cervical spine injuries

In some areas, it is a commonly accepted emergency medical technician protocol to remove a helmet during the initial management of suspected cervical spine injures. After a comprehensive survey of relevant literature, four primary reasons why Emergency Medical Services professionals would desire to remove a helmet emerge. Sources suggest that the presence of a helmet might: 1) interfere with immobilization of the athlete; 2) interfere with the ability to visualize injuries; 3) cause hyperflexion of the cervical spine; and 4) prevent proper airway management during a cardiorespiratory emergency. Many available protocols are designed for the removal of closed chamber motorcycle helmets that do not have removable face masks. There are a great number of differing viewpoints regarding this issue. The varying viewpoints are results of the failure of many emergency medical technician management protocols to address the unique situation presented by a football helmet. We: 1) demonstrate that football helmet removal is potentially dangerous and unnecessary, 2) suggest that cardiorespiratory emergencies can be effectively managed without removing the helmet, and 3) provide sports medicine professional with information that may be used to establish a joint Emergency Medical Services/Sports Medicine emergency action plan.     

Monte Carlo simulation of the Leksell Gamma Knife: I. Source modelling and calculations in homogeneous media

The Monte Carlo code PENELOPE has been used to simulate photon flux from the Leksell Gamma Knife, a precision method for treating intracranial lesions. Radiation from a single 6OCo assembly traversing the collimator system was simulated, and phase space distributions at the output surface of the helmet for photons and electrons were calculated. The characteristics describing the emitted final beam were used to build a two-stage Monte Carlo simulation of irradiation of a target. A dose field inside a standard spherical polystyrene phantom, usually used for Gamma Knife dosimetry, has been computed and compared with experimental results, with calculations performed by other authors with the use of the EGS4 Monte Carlo code, and data provided by the treatment planning system Gamma Plan. Good agreement was found between these data and results of simulations in homogeneous media. Owing to this established accuracy, PENELOPE is suitable for simulating problems relevant to stereotactic radiosurgery.     

Analytical description of dose profile behaviour in Gamma Knife radiosurgery

Stereotactic Gamma Knife radiosurgery utilizes ionizing beams from (60)Co sources and relies on a combination of collimator sizes, weighting, etc to generate a high-dose region that is conformal with a designated target volume. Dose computation is typically performed by computer, but in this paper, single collimator dose profile behaviour is modelled analytically and then extended to accommodate multiple collimators of different weights with co-located isocentres. The dose profile from a single helmet is derived from a top-hat beam profile approximation and an idealized symmetric distribution of sources is used to represent the 201 sources within a collimating helmet. The results from the analysis are validated by an independent numerical model and also compared with those obtained by other groups using numerical and experimental methods. With respect to multiple collimators, the relationship between the size (full width half maximum) of the irradiated volume and relative collimator weighting is also examined using the simple analytical model. The simplicity of the mathematics clarifies the relationship between beam profile, dose profile and multiple collimator behaviour, and provides data that compare favourably with published literature.     

Measurement of Gamma Knife helmet factors using MOSFETs

The relative dose rate for the different Gamma Knife helmets (4, 8, 14, and 18 mm) is characterized by their respective helmet factors. Since the plateau of the dose profile for the 4 mm helmet is at most 1 mm wide, detector choices are limited. Traditionally helmet factors have been measured using 1 x 1 x 1 mm3 thermoluminescent dosimeters (TLDs). However, these are time-consuming, cumbersome measurements. This article investigates the use of metal-oxide-semiconductor field effect transistors (MOSFETs) (active area of 0.2 x 0.2 mm2) as a more accurate and convenient dosimeter. Their suitability for these measurements was confirmed by basic characterization measurements. Helmet factors were measured using both MOSFETs and the established TLD approach. A custom MOSFET cassette was designed in analogy to the Elekta TLD cassette (Elekta Instruments AB) for use with the Elekta dosimetry sphere. Although both dosimeters provided values within 3% of the manufacturer's suggestion, MOSFETs provided superior accuracy and precision, in a fraction of the time required for the TLD measurements. Thus, MOSFETs proved to be a reasonable alternative to TLDs for performing helmet factor measurements.     

Electric Scooter-Related Trauma in Korea

BackgroundThe number of users of electric scooters, which provide swift and convenient mobility options, has increased sharply over recent years as their distribution as a shared service has expanded. Although the number of accidents and related damage has increased accordingly, limited research has analyzed data on the new types of accidents arising from electric scooters. This study aimed to analyze data on trauma characteristics due to accidents that occurred during electric scooter use.MethodsA retrospective chart review was conducted for patients who visited the regional trauma center of our institute due to electric scooter accidents from April 2018 to October 2021. Information was extracted on helmet-wearing status, sex, age, drinking status, accident timeframe, accident mechanism, electric scooter proficiency (period of use), injury severity, severe trauma, lethality, admission to the intensive care unit, surgery under general anesthesia, and the trauma region.ResultsAmong the 108 patients involved in electric scooter accidents, 92 patients were not wearing a helmet. Eighty-nine patients (85.2%) were male. The average age of the patients without a helmet was 31.3 years, while that of patients with a helmet was 34.1 years. The most frequent causes of accidents were lack of electric scooter operation experience and falling off the scooter due to obstacles (90 cases). Whether surgery was performed under general anesthesia was not associated with helmet use or non-use, although all patients who underwent facial fracture surgery were not wearing a helmet.ConclusionThe craniofacial region was most frequently affected in electric scooter accidents and wearing a helmet was the best way to prevent craniofacial trauma. Although helmet-wearing is mandatory, the majority of treated patients were not wearing a helmet at the time of injury. Thus, there is an urgent need to introduce a helmet rental system, as well as strict legal requirements, to improve this situation.     

Dynamic Response Due to Behind Helmet Blunt Trauma Measured with a Human Head Surrogate

A Human Head Surrogate has been developed for use in behind helmet blunt trauma experiments. This human head surrogate fills the void between Post-Mortem Human Subject testing (with biofidelity but handling restrictions) and commercial ballistic head forms (with no biofidelity but ease of use). This unique human head surrogate is based on refreshed human craniums and surrogate materials representing human head soft tissues such as the skin, dura, and brain. A methodology for refreshing the craniums is developed and verified through material testing. A test methodology utilizing these unique human head surrogates is also developed and then demonstrated in a series of experiments in which non-perforating ballistic impact of combat helmets is performed with and without supplemental ceramic appliques for protecting against larger caliber threats. Sensors embedded in the human head surrogates allow for direct measurement of intracranial pressure, cranial strain, and head and helmet acceleration. Over seventy (70) fully instrumented experiments have been executed using this unique surrogate. Examples of the data collected are presented. Based on these series of tests, the Southwest Research Institute (SwRI) Human Head Surrogate has demonstrated great potential for providing insights in to injury mechanics resulting from non-perforating ballistic impact on combat helmets, and directly supports behind helmet blunt trauma studies.     

头盔质量和质心对军机飞行员颈部肌力的影响

目的研究头盔质量和质心偏移对军机飞行员颈部肌肉活动特性的影响。方法基于AnyBody软件平台建立头颈部肌骨模型,包含C0、C1-7、T1和136组头颈部肌肉。采用集中载荷模拟头盔作用,对不同头盔质量、质心位置和加速度载荷下的7个主要肌群的肌力进行了仿真计算。结果当头盔质心与头部质心重合时,支配后伸的头半棘肌、肩胛提肌、头夹肌和颈夹肌处于收缩发力状态。当头盔质量增大,这些肌群肌力也随之线性增加,并且加速度载荷对肌力增大程度起放大作用。头盔质心后移,会降低后伸肌群的肌力,增大前屈肌群受力。头盔质心左右偏移引起的附加侧弯力矩则会激活支配侧弯功能的肌群的活动。结论头盔质量和质心位置对颈部肌群活动特性有明显影响,本文建立的头颈部肌骨模型可以计算不同状态下肌力的变化,头盔设计和使用过程可采用该技术进行定量分析。     

Human vestibulo-ocular responses to rapid,helmet-driven head movements

High-frequency head rotations in the 2–20 Hz range and passive, unpredictable head acceleration impulses were produced by a new technique, utilizing a helmet with a torque motor oscillating a mass. Unrestrained head and eye movements were recorded using magnetic sensor coils in a homogeneous magnetic field. In order to analyze the influence of the visual system on the vestibulo-ocular reflex (VOR), we took measurements under three experimental conditions: (1) with a stationary visual target; (2) in total darkness with the subject imagining the stationary target; and (3) with a head-fixed target. The results in 15 healthy subjects were highly consistent. At 2 Hz, VOR gain was near unity; above 2 Hz, VOR gain started to decrease, but this trend reversed beyond 8 Hz, where the gain increased continuously up to 1.1–1.3 at 20 Hz. Phase lag increased with frequency, from a few deg at 2 Hz to about 45 degrees at 20 Hz. Above 2 Hz, VOR gain was not significantly different for the three experimental conditions. Head acceleration impulses produced a VOR with near-unity gain in both directions. We also tested three subjects with clinically total bilateral loss of labyrinthine functions. These labyrinthine-defective subjects showed, in comparison to the normal subjects, strikingly lower gains and much longer delays in the VOR during sinu-soidal and step-like head movements. These results suggest that our new torque-driven helmet technique is effective, safe and convenient, enabling the assessment of the VOR at relatively high frequencies where both visual and mental influences are minimized.