Head Contact Research Articles

Mechanisms of head injuries in elite football

Objectives: The aim of this study was to describe, using video analysis, the mechanisms of head injuries and of incidents with a high risk of head injury in elite football....

Step-and-Repeat Photo-Nanoimprint System Using Active Orientation Head

An active orientation head was designed and installed into a step-and-repeat photo-nanoimprint system. The characteristics of the passive part of the active orientation head and compliant contact function as a basic function were evaluated. Feedback control of the active orientation head resulted in 50% load deviation at four locations to within 10%. In addition, asymmetrical load control was realized, which is one of the additional functions of the active orientation head. The automatic photo-nanoimprint sequence was demonstrated, in which the imprint load was controlled to within 1.3% of the target value. In 50 min operation, 25 dies were imprinted on a 4-inch wafer. Bright spots are visible to the eye in the dark-field illumination at each location where patterns should be found. Similar patterns 100–300 nm wide on different dies were observable by optical microscopy. Scanning electron microscope revealed smooth patterns with a half pitch of 100 nm fabricated by the step-and-repeat photo-nanoimprint system.

Dynamic Loosening of Threaded Fasteners

A study on loosening of threaded fasteners subjected to dynamic shear loads is presented. A fundamental analysis of loosening reveals that a fastener can loosen at lower loads than previously expected due to localized slip at the contact surfaces. Four different loosening processes of a screw under different conditions of slip at the head and thread contact regions are identified. Experimental results illustrating these loosening processes are presented.

Theoretical Study of the Effect of Ball Properties on Impact Force in Soccer Heading

The objective of this study was to theoretically model, based on the Hertz contact theory, the impact force and contact time, as well as the linear and angular head accelerations during heading in children using two neck stiffness conditions (infinite and negligible stiffness). The following mathematical model inputs were obtained: elastic modulus and mass of size three, four, and five balls at inflation pressures of 10, 12, and 14 psi, head modulus, head mass, head length, head and trunk moment of inertia, and the precontact ball velocity. The model outputs consisted of linear and angular head acceleration, impact force, contact time between the ball and head, and head impact criteria (HIC) all at the point of impact. Head mass and length were obtained as a percentage of body weight and height, respectively, based on age. With an increase in head mass, there is a decrease in the linear and angular head acceleration. With an increase in ball size, for the same head mass, there is an increase in the contact time between the head and the ball. Changing ball inflation pressure has little effect on the impact characteristics. Infinite neck stiffness decreased linear and angular head acceleration and HIC. Head mass and ball size have an effect on linear and angular head acceleration and contact time, respectively, whereas ball inflation pressure has a minimal effect on the impact characteristics. These results indicate that children should be restricted to using the appropriate ball for their age. Smaller head size within an age group is an underemphasized though important identifier of a player's injury risk.

FOREARM AND ELBOW INJURY

The purpose of this study was to develop an axial loading forearm fracture model and to determine the influence of forearm rotation on the fracture pattern. Twenty-six cadaveric arms were thawed in saline solution. Pressure-sensitive film was sealed and was placed through a lateral arthrotomy into the radiocapitellar joint. The arm was potted at the proximal part of the humerus with the elbow in extension. Rotational range of motion was measured with use of a goniometer starting from a supinated position (0 degrees ). Specimens were placed in a vertical position at various angles of forearm rotation, and a 27-kg mass was raised to 90 cm and was dropped onto the distal part of the radius. The pressure film was removed and was analyzed to determine the radiocapitellar joint contact area following impact. Each arm was dissected, and the injury pattern was assessed. Both-bone forearm fractures (proximal radial fractures with concomitant distal ulnar fractures) occurred at 5 degrees +/- 2.6 degrees of rotation, isolated radial head fractures occurred at 44.4 degrees +/- 5.2 degrees of rotation, and Essex-Lopresti fractures (radial head fractures with tearing of the interosseous membrane) occurred at 70 degrees +/- 25.2 degrees of rotation. The distribution of Essex-Lopresti and radial head fractures was significantly different at a cutpoint of 54 degrees of forearm rotation (p = 0.009), and the distribution of radial head fractures and both-bone forearm fractures was significantly different at a cutpoint of 10 degrees of forearm rotation (p = 0.001). The percent contact area of the radial head varied with the injury pattern (p = 0.029). Marginal radial head fractures occurred at 46.7 degrees +/- 6.6 degrees of rotation with a contact area of 30.9% +/- 8.6%, while comminuted radial head fractures occurred at 74.4 degrees +/- 27.2 degrees of rotation with a contact area of 53.9% +/- 8.3%. The amount of forearm rotation at the time of axial load impact directly influenced the injury pattern. Furthermore, the radial head contact area and the fracture severity increased in pronation compared with supination.

Elasticity and onset of frictional dissipation at a non–sliding multi–contact interface

We measure the elastic and dissipative responses of a multicontact interface, formed between the rough surfaces of two contacting macroscopic solids, submitted to a biased oscillating shear force. ...

Seat Influences on Female Neck Responses in Rear Crashes: A Reason Why Women Have Higher Whiplash Rates

Since the earliest crash investigations, whiplash has been found to occur more often in women than men. This study addresses seat properties that may explain a reason for the higher rates in women, and changes in whiplash in general over the past two decades. Three exemplar seats were defined on the basis of seat stiffness ( k ) and frame rotation stiffness ( j ) for rearward occupant load. Stiff seats have k = 40 kN/m and j = 1.8°/kN representing a foreign benchmark loaded by a male. One yielding seat had k = 20 kN/m and j = 1.4°/kN simulating a high-retention seat (1997 Grand Prix) and another k = 20 kN/m and j = 3.4°/kN simulating a 1980s to 1990s yielding seat (1990 Buick Park Avenue). Constant vehicle acceleration for 100 msec gave delta-V of 6, 10, 16, and 24 km/h. The one-dimensional model included a torso mass loading the seatback with flexible neck and head mass. Based on biomechanical data and scaling, neck stiffness was 5 kN/m and 3 kN/m for the male and female, respectively. Based on validation tests, seat stiffness was 25% less with the female. Occupant dynamics were simulated in a step-forward solution based on the differential displacement between the head, torso, and seat up to head restraint contact. Neck responses were 30% higher in the female than male through most of the rear impact and are proportional to ( k F / m TF )/( k M / m TM ), which is the ratio of seat stiffness divided by torso mass for the female and male. Neck displacements were higher with the stiff seat than the 1990 C car seat for both the female and male. They peaked at 10 km/h and dropped off for higher severity crashes due to the shorter time to head contact. Neck displacements were greater in the female than male for the lowest severity crashes with the stiff and 1990 C car seats, when displacement was scaled for equal tolerance. The female in 1997 W car seat had the lowest neck displacements. Stiff seats increased neck displacements over the yielding seats of the 1980s in rear crashes. The trend is similar in men and women, but early neck displacements are greater in women because of a higher ratio of seat stiffness to torso mass. This implies that seat stiffness is not sufficiently low in proportion to the female mass in comparison to males. The j and k seat properties influence neck biomechanics and occupant dynamics, but k is important in determining early response differences between males and females.

Reconstruction of real world head injury accidents resulting from falls using multibody dynamics

Objective. To reconstruct real life head injury accidents resulting from falls using multibody modelling software, with the aim of comparing simulation output to injuries sustained. Background. Much previous research on head injury biomechanics has focussed on animals and cadavers. However, focus is increasingly turning towards the examination of real life head injury. Falls are a major cause of head injury and, in general, are simpler to model than other accident types. Design and methods. Five cases of simple falling accidents resulting in focal head injury were examined, and reconstructions were performed using a multibody model of the human body. Each case was reconstructed a number of times, varying the initial conditions and using two different sets of properties for head contact. Results. Results obtained included velocities, accelerations and forces on the head during impact. This output appeared more sensitive to changes in head contact characteristics than to changes in initial conditions. Depending on the contact characteristics used, results were consistent with proposed tolerance limits from the literature for various lesion types. Conclusions. Provided it is used with caution, this method could prove a useful source of biomechanical data for the investigation of head injury biomechanics. Relevance Biomechanical investigation of real-life cases of head injury is very important, yet not as prevalent as work with animals and cadavers. Reconstruction of real life accidents is a good method of obtaining data that will aid in the investigation of mechanisms of head injury and human tolerance to head injury.

A STUDY OF HEAD ACCELERATION DURING CRASH TEST SIMULATION USING LS_DYNA SOFTWARE

A finite element model of a belted-dummy that uses seatbelts as shell elements is modified to include seatbelts defined in LS_DYNA code as seatbelt elements. This action will give the ability to deal with experimental data of seatbelt materials. A comparison between the two cases (shell elements and seatbelt elements) is included to shed light on differences. Head Injury Criterion (HIC) is used to evaluate the head damage coming from resultant acceleration. The output acceleration data of LS_DYNA is manipulated by VB program written for this purpose. Using softer material for the seat at head and back contact area reduced the high values of HIC. But high value of HIC is noticed at initial velocity 10 m/sec according to instant conditions affecting the dummy, which refer to the necessity of using airbag besides seatbelts to get convenient degree of protection. The studies performed indicated the importance of using two seatbelts (the lower seatbelt together with the upper one).

Measurement and Prediction of Tape Cupping Under Mechanical and Hygrothermal Loads and Its Influence on Debris Generation in Linear Tape Drives

Magnetic tapes, which may be modeled as three-ply laminates, exhibit transverse curvature, or cupping, as manufactured and when mechanical and hygrothermal loads are applied. Among other things, this cupping affects debris generation since it influences the contact between the flawed tape edge and head, the point where much of the debris generation occurs. This influence on debris generation is demonstrated experimentally in this study. Much more debris accumulates near the tape edge-head contact than at other contact locations. No difference in debris generation was found for two tapes with slightly different residual cupping (which is controlled during manufacturing). The target residual cupping is usually negative, which means that the tape bows out towards the tape so that the edges are farther away from the head than the center of contact is, so as to reduce contact pressure with the tape edges. However, cupping generally changes upon application of a tension and generally reduces the importance of residual cupping, which accounts for the failure to find a difference in debris generation for tapes with slightly different residual cupping. A finite element method model that uses laminate shell elements and accounts for in-plane stress stiffening, thus making it suitable for thin laminate modeling, was created. This modeling demonstrates that application of tensile and normal (used to simulate head contact) loads leads to cupping movement in the positive direction, which indicates a more severe edge contact, for an increase in front coat Young’s modulus and/or an increase in front coat thickness. The same trends hold for an increase in back coat Young’s modulus and/or an increase in back coat thickness. Modeling also demonstrates that cupping moves in the positive direction for an increase in the substrate’s Young’s modulus in the transverse direction for MP and ME tapes. An analytical model demonstrates that increases in temperature and front coat thermal expansion coefficient leads to cupping movement in the negative direction. The same trends hold for changes in relative humidity.

Pedestrian Head Impact Conditions Depending on the Vehicle Front Shape and Its Construction--Full Model Simulation

For the evaluation of pedestrian protection, the European Enhanced Vehicle-Safety Committee Working Group 17 report is now commonly used. In the evaluation of head injuries, the report takes into account only the hood area of the vehicle. But recent pedestrian accident data has shown the injury source for head injury changing to the windshield and A-pillar from the hood. The head contact points are considered to fall on a parallel to the front shape of the vehicle along the lateral direction, but the rigidity of the outer side construction is different from the center area. The purpose of this study is to consider the reason for the change in injury source for recent vehicle models. The head contact points and contact conditions, speed and angle, are thought to be influenced not only by the vehicle's geometry, but also its construction (rigidity). In this study, vehicle-pedestrian impact simulations were calculated with a finite element model for several hitting positions, including the outer side areas. Full dummy sled tests were conducted to confirm the simulation results. These results show that, for impacts at the outer sides of the vehicle, the head contact points are more rearward than at the vehicle center. In addition, the speed and angle of the head contact were found to be influenced by the pedestrian height.

The Evidence for Brain Injury in Whiplash Injuries

The evidence that brain damage can occur in injuries that produce whiplash is reviewed. The clinical phenomena for the two injuries are the same. Pure whiplash injury implies no, or minimal head contact, but many patients also have head contact against a head rest or the steering wheel or windshield. The relative severity of the neck injury and the head injury distinguishes whiplash from mild closed head injury. If there is brain injury is some patients with whiplash, it, by definition, falls at the mildest end of the concussion spectrum. The relationship between these two injuries is examined.

The neuronal targets for GABAergic reticulospinal inhibition that stops swimming in hatchling frog tadpoles

In most animals locomotion can be started and stopped by specific sensory cues. We are using a simple vertebrate, the hatchling Xenopus tadpole, to study a neuronal pathway that turns off locomotion. In the tadpole, swimming stops when the head contacts solid objects or the water's surface meniscus. The primary sensory neurons are in the trigeminal ganglion and directly excite inhibitory reticulospinal neurons in the hindbrain. These project axons into the spinal cord and release GABA to inhibit spinal neurons and stop swimming. We ask whether there is specificity in the types of spinal neuron inhibited. We used single-neuron recording to determine which classes of spinal neurons receive inhibition when the head skin is pressed. Ventral motoneurons and premotor interneurons involved in generating the swimming rhythm receive reliable GABAergic inhibition. More dorsal inhibitory premotor interneurons are inhibited less reliably and some are excited. Dorsal sensory pathway interneurons that start swimming following a touch to the trunk skin do not appear to receive such inhibition. There is therefore specificity in the formation of descending inhibitory connections so that more ventral neurons producing swimming are most strongly inhibited.

Contact analysis of impact in magnetic head disk interfaces

Three-dimensional finite element analysis of head and disk contact effects induced by impact in magnetic head disk interface (HDI) are presented. Elastic–plastic contact simulations are performed using abaqus. The entire contact–impact procedures during head disk collision under the dynamic loading of half-sine pulse acceleration with profiles of 300 and 500 g amplitude and 1.0 ms in duration are described in detail. Simulation results for the contact pressure distribution at HDI, von Mises equivalent stress, and equivalent plastic strain fields are examined and interpreted in terms of impact history. A comprehensive history of head disk relative displacement and von Mises equivalent stresses within contact region are provided and the evolution of plasticity are discussed. It is shown that finite element method can provide the simulation of the contact behavior resulting from the dynamic loading.

Calves’ motivation for access to two different types of social contact measured by operant conditioning

Calves housed individually have little opportunity for social contact. However, performance of social behaviour may constitute a need in calves. Slopes of demand functions (demand elasticity), generated by operant conditioning techniques, are used to measure behavioural motivation of farm animals. A methodological discussion concerns the way social contact should be provided in operant conditioning studies. By operant conditioning, the present study investigated calves’ motivation for two different types of social contact: head contact through metal bars, and full social contact where calves were allowed to interact without restrictions. Six test calves and six companion calves were used. Tests were carried out in daily sessions in a cross-over design. For each treatment, test calves were exposed to five Fixed Ratio schedules (FR6, 12, 18, 24, 30) within three runs. Rewards consisted of 3 min access to social contact with the companion. Behavioural activity in the reward periods was recorded continuously. Results showed a difference between demand functions based on number of rewards obtained per session. The slope for head contact was steeper than for full contact ( P<0.01), whereas intercepts did not differ. Calves used more time for social activity within rewards when tested for full contact compared to head contact ( P<0.001). Duration of social activity per reward increased as a function of increasing FR value for full contact ( P<0.001), but not for head contact. Calves used significantly less time for social activity in the later rewards of the test sessions compared to the earlier for full contact ( P<0.01), but not for head contact. Slopes of demand functions based on duration of social activity per session were not significantly different, but intercepts differed significantly ( P<0.01). For both head and full contact, slopes were more shallow than slopes of demand functions based on number of rewards. The study shows that the type of social contact may influence the slope of the resulting demand function based on number of rewards obtained per session. Calves are more motivated to get access to full contact than to head contact, and therefore, full contact should be used in future operant conditioning studies. Moreover, the study also shows that factors like FR value and reward number may affect the duration of time actually engaged in social activity within rewards when full social contact is used as reinforcer.

EXPERIMENTAL STUDY OF LOOSENING OF THREADED FASTENERS DUE TO DYNAMIC SHEAR LOADS

This paper presents a study on loosening of threaded fasteners subjected to dynamic shear loads. A fundamental analysis of loosening reveals that a fastener can loosen at lower loads than previously expected due to localized slip at the contact surfaces. Four different loosening processes of a screw under different conditions of slip at the head and thread contact regions are identified. Experimental results illustrating these loosening processes are presented. In addition, the minimum dynamic shear force required to initiate loosening is determined experimentally.

Sensory Activation and Role of Inhibitory Reticulospinal Neurons that Stop Swimming in Hatchling Frog Tadpoles

Activity in neuronal networks underlying locomotion and other rhythmic actions can start and stop in response to specific sensory stimuli. In vertebrate locomotion, some reticulospinal neurons such as Mauthner neurons can initiate activity, but the neurons controlling stopping are not defined. We have studied swimming in tadpoles of the frog,Xenopus, which is started by touching the skin and stops when the head contacts a solid surface. Using an immobilized tadpole preparation, the same stimuli control fictive swimming. When head contact is imitated by pressure to the head skin sensory neurons in the trigeminal ganglion are active, spinal neurons receive GABAergic inhibition, and swimming stops. Here we record intracellularly from neurons in the hindbrain that are excited by pressure or electrical stimulation to the head skin. By intracellular filling with neurobiotin, we identify these anatomically as mid-hindbrain reticulospinal neurons (MHRs). These have contralateral descending projections to the spinal cord and GABA-like immunoreactivity. They are rhythmically inhibited during fictive swimming. Individual MHRs reliably stopped ongoing swimming when brief firing was induced by intracellular current injection. The ability of individual MHRs to stop swimming was blocked by the GABAAantagonist bicuculline. Our evidence indicates that MHRs receive direct excitation from trigeminal sensory neurons and in turn release GABA to directly inhibit spinal neurons and turn off the swimming central pattern generator.

Sensory activation and role of inhibitory reticulospinal neurons that stop swimming in hatchling frog tadpoles.

Activity in neuronal networks underlying locomotion and other rhythmic actions can start and stop in response to specific sensory stimuli. In vertebrate locomotion, some reticulospinal neurons such as Mauthner neurons can initiate activity, but the neurons controlling stopping are not defined. We have studied swimming in tadpoles of the frog, Xenopus, which is started by touching the skin and stops when the head contacts a solid surface. Using an immobilized tadpole preparation, the same stimuli control fictive swimming. When head contact is imitated by pressure to the head skin sensory neurons in the trigeminal ganglion are active, spinal neurons receive GABAergic inhibition, and swimming stops. Here we record intracellularly from neurons in the hindbrain that are excited by pressure or electrical stimulation to the head skin. By intracellular filling with neurobiotin, we identify these anatomically as mid-hindbrain reticulospinal neurons (MHRs). These have contralateral descending projections to the spinal cord and GABA-like immunoreactivity. They are rhythmically inhibited during fictive swimming. Individual MHRs reliably stopped ongoing swimming when brief firing was induced by intracellular current injection. The ability of individual MHRs to stop swimming was blocked by the GABA(A) antagonist bicuculline. Our evidence indicates that MHRs receive direct excitation from trigeminal sensory neurons and in turn release GABA to directly inhibit spinal neurons and turn off the swimming central pattern generator.

Three-dimensional finite element analysis of threaded fastener loosening due to dynamic shear load

The two most widespread causes of failure of threaded fasteners subjected to dynamic loads are fatigue and vibration induced loosening. This paper presents results of a study on failure of threaded fasteners by vibration induced loosening caused due to dynamic shear loads. Previous experimental work has revealed that fastener loosening occurs as a result of complete or localized slip at the thread and head contact surfaces. A three-dimensional finite element (FE) model is used to study details of four different loosening processes that are characterized by either complete or localized slip at the head and thread contacts. The FE model is found to be capable of adequately modeling factors that influence slip and predicting the different loosening processes. Primary factors that influence slip at fastener contacts are discussed. The results show that loosening can occur at relatively low shear loads due to the process of localized slip.

Correlation of head injury to vehicle contact points using crash injury research and engineering network data

Head injury is the most common cause of morbidity and mortality in motor vehicle crashes. Efforts to improve vehicle design, which minimize forces exerted to the occupant’s head, may lead to a reduction in the frequency and severity of head injury. We therefore set out to identify mechanisms producing severe head injury in motor vehicle crashes (MVC) derived from the crash injury research and engineering network (CIREN) database. CIREN combines crash site analysis, vehicle damage assessment, and occupant kinematics in relation to the occupant’s injuries. From the Seattle CIREN database of 101 cases, compiled from 1997 to 1998, we selected those crashes in which the occupant sustained severe head injury (abbreviated injury score, AIS≥4) for analysis. We examined crash mechanism, energy transfer, point of head contact, vehicle intrusion and resulting injuries. There were 15 cases with severe head injury. These were primarily due to side impacts ( n=10) in comparison to front impacts ( n=5). The average net change in velocity (delta velocity, DV) was 15 mile/h (range 4–29 mile/h). In cases where the primary point of head contact could be elucidated the B-pillar predominated (4 cases, 33.3%) followed by the striking external object (2 cases, 16.7%), A- (1 case, 8.3%) and C- (1 case, 8.3%) pillars, roof side rail (1 case, 8.3%), windshield header (1 case, 8.3%), windowsill (1 case, 8.3%) and airbag (1 case, 8.3%). In this series the predominant mechanism of head injury was lateral impacts, especially those in which the victims’ heads struck the B-pillar. The need for improved head protection from lateral impacts is indicated.