Tolerance of the skull to blunt ballistic temporo-parietal impact

Less-lethal ballistic projectiles are used by police personnel to temporarily incapacitate suspects. While the frequency of these impacts to the head is low, they account for more serious injuries than impacts to any other body region. As a result, there is an urgent need to assess the tolerance of the head to such impacts. The focus of this study was to investigate the tolerance of the temporo-parietal skull to blunt ballistic impact and establish injury criteria for risk assessment. Seven unembalmed isolated cadaver heads were subjected to fourteen impacts. Specimens were instrumented with a nine-accelerometer array as well as strain gages surrounding the impact site. Impacts were performed with a 38 mm instrumented projectile at velocities ranging from 18 to 37 m/s. CT images and autopsies were performed to document resulting fractures. Peak fracture force for the seven resulting fractures was 5633±2095 N. Peak deformation for fracture-producing impacts was 7.8±3.2 mm. The blunt criterion (BC), peak force and principal strain were determined to be the best predictors of depressed comminuted fractures. Temporo-parietal tolerance levels were consistent with previous studies. An initial force tolerance level of 2346 N is established for the temporo-parietal region for blunt ballistic impact with a 38 mm diameter impactor.     

Peak linear and rotational acceleration magnitude and duration effects on maximum principal strain in the corpus callosum for sport impacts

Concussion has been linked to the presence of injurious strains in the brain tissues. Research investigating severe brain injury has reported that strains in the brain may be affected by two parameters: magnitude of the acceleration, and duration of that acceleration. However, little is known how this relationship changes in terms of creating risk for brain injury for magnitudes and durations of acceleration common in sporting environments. This has particular implications for the understanding and prevention of concussive risk of injury in sporting environments. The purpose of this research was to examine the interaction between linear and rotational acceleration and duration on maximum principal strain in the brain tissues for loading conditions incurred in sporting environments. Linear and rotational acceleration loading curves of magnitudes and durations similar to those from impact in sport were used as input to the University College Brain Trauma Model and maximum principal strain (MPS) was measured for the different curves. The results demonstrated that magnitude and duration do have an effect on the strain incurred by the brain tissue. As the duration of the acceleration increases, the magnitude required to achieve strains reflecting a high risk of concussion decreases, with rotational acceleration becoming the dominant contributor. The magnitude required to attain a magnitude of MPS representing risk of brain injury was found to be as low as 2500 rad/s² for impacts of 10–15 ms; indicating that interventions to reduce the risk of concussion in sport must consider the duration of the event while reducing the magnitude of acceleration the head incurs.     

Finite element modelling of equestrian helmet impacts exposes the need to address rotational kinematics in future helmet designs

Jockey head injuries, especially concussions, are common in horse racing. Current helmets do help to reduce the severity and incidences of head injury, but the high concussion incidence rates suggest that there may be scope to improve the performance of equestrian helmets. Finite element simulations in ABAQUS/Explicit were used to model a realistic helmet model during standard helmeted rigid headform impacts and helmeted head model University College Dublin Brain Trauma Model (UCDBTM) impacts.

Current helmet standards for impact determine helmet performance based solely on linear acceleration. Brain injury-related values (stress and strain) from the UCDBTM showed that a performance improvement based on linear acceleration does not imply the same improvement in head injury-related brain tissue loads. It is recommended that angular kinematics be considered in future equestrian helmet standards, as angular acceleration was seen to correlate with stress and strain in the brain.     

Evaluation of a flexible force sensor for measurement of helmet foam impact performance

The association between translational head acceleration and concussion remains unclear and provides a weak predictive measure for this type of injury; thus, alternative methods of helmet evaluation are warranted. Recent finite element analysis studies suggest that better estimates of concussion risk can be obtained when regional parameters of the cranium, brain and surrounding tissues are included. Lacking, however, are empirical data at the head–helmet interface with regards to contact area and force. Hence, the purpose of this study was to evaluate a system to capture the impact force distribution of helmet foams. Thirteen Flexiforce^® sensors were arranged in a 5×5 cm array, secured to a load cell. Three densities of foam were repeatedly impacted with 5 J of energy during ambient (20 °C) and cold (?25 °C) conditions. RMS error, calculated relative to the global force registered by the load cell, was <1.5% of the measurement range during individual calibration of the Flexiforce^® sensors. RMS error was 5% of the measured range for the global force estimated by the sensor array. Load distribution measurement revealed significant differences between repeated impacts of cold temperature foams for which acceleration results were non-significant. The sensor array, covering only 36% of the total area, possessed sufficient spatial and temporal resolution to capture dynamic load distribution patterns. Implementation of this force mapping system is not limited to helmet testing. Indeed it may be adopted to assess other body regions vulnerable to contact injuries (e.g., chest, hip and shin protectors).     

Upper limb and trunk muscle activation during an unexpected descent on the outstretched hands in young and older women

Falling on the outstretched hands (FOOSH), a protective mechanism to arrest the body and avoid injury, requires upper limb and trunk motor control for effective body descent. The purpose of this study was to investigate muscle activity during three phases of an unexpected FOOSH in healthy older and younger women. Twenty young (mean age 22.9 yrs, SD ± 3.7) and 20 older females (mean age 68.1 yrs, SD ± 5.0) performed five trials of unexpected FOOSHs. Surface electromyography (EMG) determined muscle activations for left shoulder girdle, elbow and abdominal muscles during an unexpected FOOSH. Root mean squared EMG data were calculated during three phases: (1) baseline (BL; 500 ms prior to release), (2) the preparatory phase (PRE; time between release and impact) (mean 257 ± 37 ms) and post-impact (POST; 200 ms after impact). A mixed MANOVA determined differences between phases and age groups. There was a significant multivariate interaction effect of age and time phase on muscle activity (p = 0.001). Younger women had significantly higher internal oblique/transversus abdominus activity during PRE (p = 0.006) as well as variations in muscle activity of shoulder girdle and elbow muscles. The age differences observed may lead to poorer preliminary trunk activation and greater arm bracing in older women, potentially increasing risk of fallrelated injury.     

Rhythmic contractility in the hepatic portal “corkscrew” vein of the rat snake

Terrestrial, but not aquatic, species of snakes have hepatic portal veins with a corkscrew morphology immediately posterior of the liver. Relatively large volumes of venous blood are associated with this region, and the corkscrew vein has been proposed to function as a bidirectional valve that impedes gravitational shifts of intravascular volume. To better understand the functional significance of the corkscrew anatomy, we investigated the histology and contractile mechanisms in isolated corkscrew segments of the hepatic portal vein of a yellow rat snake (Pantherophis obsoletus). Morphologically, the corkscrew portal vein is here shown to have two distinct layers of smooth muscle – an inner circular layer, and an outer longitudinal layer, separated by a layer of collagen, – whereas only a single circular layer of smooth muscle is present in the adjacent posterior caval vein. Low frequency (~ 0.3 cycles*min^? 1) spontaneous and catecholamine-induced rhythms were observed in 11% and 89% of portal vein segments, respectively, but neither spontaneous nor agonist-induced cycling was observed in adjacent posterior (non-corkscrew) caval veins. Catecholamines, angiotensin II, or stretch increased the amplitude and/or frequency of contractile cycles. Ouabain, verapamil or indomethacin, but not tetrodotoxin, α-, or ß-adrenergic receptor antagonists, inhibited cyclical contractions indicating a dependence of these cycles on Na⁺/K⁺ ATPase, extracellular Ca²⁺ and prostanoid(s). These data suggest that the rhythmic contractility of the corkscrew segment of the ophidian portal vein may act in conjunction with its morphological features to improve venous return and to prevent retrograde shifts of blood that might otherwise pool in posterior veins.     

The sensitivity to inter-subject variability of the bridging vein entry angles for prediction of acute subdural hematoma

Acute subdural hematoma (ASDH) is one of the most frequent traumatic brain injuries (TBIs) with high mortality rate. Bridging vein (BV) ruptures is a major cause of ASDH. The KTH finite element head model includes bridging veins to predict acute subdural hematoma due to BV rupture. In this model, BVs were positioned according to Oka et al. (1985). The aim of the current study is to investigate whether the location and entry angles of these BVs could be modelled using data from a greater statistical sample, and what the impact of this improvement would be on the model’s predictive capability of BV rupture.From the CT angiogram data of 78 patients, the relative position of the bridging veins and their entry angles along the superior sagittal sinus was determined. The bridging veins were repositioned in the model accordingly. The performance of the model, w.r.t. BV rupture prediction potential was tested on simulations of full body cadaver head impact experiments. The experiments were simulated on the original version of the model and on three other versions which had updated BV positions according to mean, maximum and minimum entry angles.Even though the successful prediction rate between the models stayed the same, the location of the rupture site significantly improved for the model with the mean entry angles. Moreover, the models with maximum and minimum entry angles give an insight of how BV biovariability can influence ASDH.In order to further improve the successful prediction rate, more biofidelic data are needed both with respect to bridging vein material properties and geometry. Furthermore, more experimental data are needed in order to investigate the behaviour of FE head models in depth.     

Twist buckling of veins under torsional loading

Veins are often subjected to torsion and twisted veins can hinder and disrupt normal blood flow but their mechanical behavior under torsion is poorly understood. The objective of this study was to investigate the twist deformation and buckling behavior of veins under torsion. Twist buckling tests were performed on porcine internal jugular veins (IJVs) and human great saphenous veins (GSVs) at various axial stretch ratio and lumen pressure conditions to determine their critical buckling torques and critical buckling twist angles. The mechanical behavior under torsion was characterized using a two-fiber strain energy density function and the buckling behavior was then simulated using finite element analysis. Our results demonstrated that twist buckling occurred in all veins under excessive torque characterized by a sudden kink formation. The critical buckling torque increased significantly with increasing lumen pressure for both porcine IJV and human GSV. But lumen pressure and axial stretch had little effect on the critical twist angle. The human GSVs are stiffer than the porcine IJVs. Finite element simulations captured the buckling behavior for individual veins under simultaneous extension, inflation, and torsion with strong correlation between predicted critical buckling torques and experimental data (R² = 0.96). We conclude that veins can buckle under torsion loading and the lumen pressure significantly affects the critical buckling torque. These results improve our understanding of vein twist behavior and help identify key factors associated in the formation of twisted veins.     

A subject-specific anisotropic visco-hyperelastic finite element model of female pelvic floor stress and strain during the second stage of labor

ObjectivesTo develop an improved model representation of the biomechanics of the levator muscles during the second stage of labor and to use a sensitivity analysis to explore the pathomechanics of levator muscle injury.MethodsA subject-specific finite element model of human pelvic floor and fetal head was developed based on in vivo MRI data of a fetal head and maternal pelvis. An anisotropic visco-hyperelastic constitutive model employed material parameters estimated from biaxial tests on pelvic floor tissues. Boundary conditions reflected both anatomic constraints and the curve of Carus. A short second stage of labor, scaled to 10 min, was then simulated using a single expulsive push made in the absence of levator co-contraction.ResultsLarge levator stresses occurred near the levator hiatus reaching 9 MPa at the pubovisceral muscle enthesis. The dominant principal stresses were located at, and aligned with, the edge of the hiatus. Muscle stretch bordering the levator hiatus was inhomogeneous: the average levator stretch was 3.55 with a high of 4.64 at the pubovisceral muscle enthesis. Decreasing perineal body stiffness by 40%, 50%, and 60% led to reductions in the maximum principal stretch ratio at the pubovisceral muscle enthesis of 8%, 13%, and 18%, respectively.ConclusionsThe pubovisceral muscle enthesis and the muscle near the perineal body are the regions of greatest strain thereby placing them at highest risk for stretch-related injury. Decreasing perineal body tissue stiffness significantly reduced tissue stress and strain, and therefore injury risk, in those regions.     

Fish oil improves motor function,limits blood–brain barrier disruption,and reduces Mmp9 gene expression in a rat model of juvenile traumatic brain injury

The effects of an oral fish oil treatment regimen on sensorimotor, blood–brain barrier, and biochemical outcomes of traumatic brain injury (TBI) were investigated in a juvenile rat model. Seventeen-day old Long-Evans rats were given a 15 mL/kg fish oil (2.01 g/kg EPA, 1.34 g/kg DHA) or soybean oil dose via oral gavage 30 min prior to being subjected to a controlled cortical impact injury or sham surgery, followed by daily doses for seven days. Fish oil treatment resulted in less severe hindlimb deficits after TBI as assessed with the beam walk test, decreased cerebral IgG infiltration, and decreased TBI-induced expression of the Mmp9 gene one day after injury. These results indicate that fish oil improved functional outcome after TBI resulting, at least in part from decreased disruption of the blood–brain barrier through a mechanism that includes attenuation of TBI-induced expression of Mmp9.     

Biceps femoris and semitendinosus tendon/aponeurosis strain during passive and active (isometric) conditions

The purpose of this study was to quantify strain and elongation of the long head of the biceps femoris (BFlh) and the semitendinosus (ST) tendon/aponeurosis. Forty participants performed passive knee extension trials from 90° of knee flexion to full extension (0°) followed by ramp isometric contractions of the knee flexors at 0°, 45° and 90° of knee flexion. Two ultrasound probes were used to visualize the displacement of BFlh and ST tendon/aponeurosis. Three-way analysis of variance designs indicated that: (a) Tendon/aponeurosis (passive) elongation and strain were higher for the BFlh than the ST as the knee was passively extended (p < 0.05), (b) contraction at each angular position was accompanied by a smaller BFlh tendon/aponeurosis (active) strain and elongation than the ST at higher levels of effort (p < 0.05) and (c) combined (passive and active) strain was significantly higher for the BFlh than ST during ramp contraction at 0° but the opposite was observed for the 45° and 90° flexion angle tests (p < 0.05). Passive elongation of tendon/aponeurosis has an important effect on the tendon/aponeurosis behavior of the hamstrings and may contribute to a different loading of muscle fibers and tendinous tissue between BFlh and ST.     

Medium optimization for the high yield production of single (+)-terrein by Aspergillus terreus strain PF26 derived from marine sponge Phakellia fusca

Terrein has potential application in the fields of medicine, cosmetology and agriculture, however, the chemical synthesis of terrein with single configuration is a difficult task, and the biosynthesis of terrein always results in low production (ca. 0.33–400 mg/L). In this study, we reported an Aspergillus terreus strain PF26 which could produce (+)-terrein on a high level. After the selection of a suitable basic medium, the component concentrations were optimized using Plackett–Burman design and response surface methodology. Consequently, an optimal medium containing 28.41 g glucose, 23.18 g maltose, 20.00 g mannitol, 8.52 g malt extract, 10.00 g monosodium glutamate 10.00 g NH₄Cl in 1 L ASW was obtained, and a high (+)-terrein production of 3.71 g/L fermentation broth was achieved, which represents the highest fermentation production of (+)-terrein to date. The result highlighted the industry's potential of A. terreus strain PF26 in the production of bioactive (+)-terrein on a large-scale.     

Effect of ghrelin on chronic liver injury and fibrogenesis in male rats: Possible role of nitric oxide

Recent studies have revealed that ghrelin may be an antioxidant and anti-inflammatory agent in many organs, however its role in chronic liver injury (CLI) remains unclear. The role of nitric oxide (NO) in CLI is controversial as evidence suggests that NO is either a primary mediator of liver cell injury or exhibits a protective effect against injurious stimuli. Recent evidence demonstrated that the therapeutic potential for ghrelin was through eNOS activation and increase in NO production. However, its role on NO production in the liver has not been previously investigated. The aim of this study was to investigate the role of ghrelin in treatment of CLI, and whether this action is mediated through NO. Forty male rats were divided into four groups: Group I: Control; Group II: chronic liver injury (CLI); Group III: CLI + Ghrelin; and Group IV: CLI + Ghrelin + l-NAME. Liver enzymes and tumor necrosis factor alpha (TNF-α), were measured to assess hepatocellular injury. Liver tissue collagen content, malondialdehyde (MDA), gene expression of Bax, Bcl-2, and eNOS were assessed to determine the mechanism of ghrelin action. Results showed that ghrelin decreased serum liver enzymes and TNF-α levels. Ghrelin also reduced liver tissue collagen, MDA, and Bax gene expression, and increased Bcl-2 and eNOS gene expression. The effects on TNF-α, collagen, MDA, Bax, and eNOS were partially reversed in Group IV, suggesting that ghrelin's action could be through modulation of NO levels. Therefore, ghrelin's hepatoprotective effect is partially mediated by NO release.     

Experimental validation of finite element predicted bone strain in the human metatarsal

Metatarsal stress fracture is a common injury observed in athletes and military personnel. Mechanical fatigue is believed to play an important role in the etiology of stress fracture, which is highly dependent on the resulting bone strain from the applied load. The purpose of this study was to validate a subject-specific finite element (FE) modeling routine for bone strain prediction in the human metatarsal. Strain gauge measurements were performed on 33 metatarsals from seven human cadaveric feet subject to cantilever bending, and subject-specific FE models were generated from computed tomography images. Material properties for the FE models were assigned using a published density-modulus relationship as well as density-modulus relationships developed from optimization techniques. The optimized relationships were developed with a ‘training set’ of metatarsals (n = 17) and cross-validated with a ‘test set’ (n = 16). The published and optimized density elasticity equations provided FE-predicted strains that were highly correlated with experimental measurements for both the training (r² ≥ 0.95) and test (r² ≥ 0.94) sets; however, the optimized equations reduced the maximum error by 10% to 20% relative to the published equation, and resulted in an X = Y type of relationship between experimental measurements and FE predictions. Using a separate optimized density-modulus equation for trabecular and cortical bone did not improve strain predictions when compared to a single equation that spanned the entire bone density range. We believe that the FE models with optimized material property assignment have a level of accuracy necessary to investigate potential interventions to minimize metatarsal strain in an effort to prevent the occurrence of stress fracture.     

Knee flexor strength and bicep femoris electromyographical activity is lower in previously strained hamstrings

The aim of this study was to determine if athletes with a history of hamstring strain injury display lower levels of surface EMG (sEMG) activity and median power frequency in the previously injured hamstring muscle during maximal voluntary contractions. Recreational athletes were recruited, 13 with a history of unilateral hamstring strain injury and 15 without prior injury. All athletes undertook isokinetic dynamometry testing of the knee flexors and sEMG assessment of the biceps femoris long head (BF) and medial hamstrings (MHs) during concentric and eccentric contractions at ±180 and ±60° s^?1. The knee flexors on the previously injured limb were weaker at all contraction speeds compared to the uninjured limb (+180° s^?1 p = 0.0036; +60° s^?1 p = 0.0013; ?60° s^?1 p = 0.0007; ?180° s^?1 p = 0.0007) whilst sEMG activity was only lower in the BF during eccentric contractions (?60° s^?1 p = 0.0025; ?180° s^?1 p = 0.0003). There were no between limb differences in MH sEMG activity or median power frequency from either BF or MH in the injured group. The uninjured group showed no between limb differences in any of the tested variables. Secondary analysis comparing the between limb difference in the injured and the uninjured groups, confirmed that previously injured hamstrings were mostly weaker (+180° s^?1 p = 0.2208; +60° s^?1 p = 0.0379; ?60° ^?1 p = 0.0312; ?180° s^?1 p = 0.0110) and that deficits in sEMG were confined to the BF during eccentric contractions (?60° s^?1 p = 0.0542; ?180° s^?1 p = 0.0473). Previously injured hamstrings were weaker and BF sEMG activity was lower than the contralateral uninjured hamstring. This has implications for hamstring strain injury prevention and rehabilitation which should consider altered neural function following hamstring strain injury.     

An ex vivo experiment to reproduce a forward fall leading to fractured and non-fractured radii

Forward falls represent a risk of injury for the elderly. The risk is increased in elderly persons with bone diseases, such as osteoporosis. However, half of the patients with fracture were not considered at risk based on bone density measurement (current clinical technique). We assume that loading conditions are of high importance and should be considered. Real loading conditions in a fall can reach a loading speed of 2 m/s on average. The current study aimed to apply more realistic loading conditions that simulate a forward fall on the radius ex vivo. Thirty radii from elderly donors (79 y.o. ± 12 y.o., 15 males, 15 females) were loaded at 2 m/s using a servo-hydraulic testing machine to mimic impact that corresponds to a fall. Among the 30 radii, 14 had a fracture after the impact, leading to two groups (fractured and non-fractured). Surfacic strain fields were measured using stereovision and allow for visualization of fracture patterns. The average maximum load was 2963 ± 1274 N. These experimental data will be useful for assessing the predictive capability of fracture risk prediction methods such as finite element models.     

The impact of acute lung injury,ECMO and transfusion on oxidative stress and plasma selenium levels in an ovine model

The purpose of this study was to determine the effects of smoke induced acute lung injury (S-ALI), extracorporeal membrane oxygenation (ECMO) and transfusion on oxidative stress and plasma selenium levels. Forty ewes were divided into (i) healthy control (n = 4), (ii) S-ALI control (n = 7), (iii) ECMO control (n = 7), (iv) S-ALI + ECMO (n = 8) and (v) S-ALI + ECMO + packed red blood cell (PRBC) transfusion (n = 14). Plasma thiobarbituric acid reactive substances (TBARS), selenium and glutathione peroxidase (GPx) activity were analysed at baseline, after smoke injury (or sham) and 0.25, 1, 2, 6, 7, 12 and 24 h after initiation of ECMO. Peak TBARS levels were similar across all groups. Plasma selenium decreased by 54% in S-ALI sheep (1.36 ± 0.20 to 0.63 ± 0.27 μmol/L, p < 0.0001), and 72% in sheep with S-ALI + ECMO at 24 h (1.36 ± 0.20 to 0.38 ± 0.19, p < 0.0001). PRBC transfusion had no effect on TBARS, selenium levels or glutathione peroxidase activity in plasma. While ECMO independently increased TBARS in healthy sheep to levels which were similar to the S-ALI control, the addition of ECMO after S-ALI caused a negligible increase in TBARS. This suggests that the initial lung injury was the predominant feature in the TBARS response. In contrast, the addition of ECMO in S-ALI sheep exacerbated reductions in plasma selenium beyond that of S-ALI or ECMO alone. Clinical studies are needed to confirm the extent and duration of selenium loss associated with ECMO.     

Integrating arm movement into bridge exercise: Effect on EMG activity of selected trunk muscles

The purpose of this study was to determine whether incorporating arm movement into bridge exercise changes the electromyographic (EMG) activity of selected trunk muscles. Twenty healthy young men were recruited for this study. EMG data were collected for the rectus abdominis (RA), internal oblique (IO), erector spinae (ES), and multifidus (MF) muscles of the dominant side. During bridging, an experimental procedure was performed with two options: an intervention factor (with and without arm movement) and a bridging factor (on the floor and on a therapeutic ball). There were significant main effects for the intervention factor in the IO and ES and for the bridging factor in the IO. The RA and IO showed significant interaction between the intervention and bridge factors. Furthermore, IO/RA ratio during bridging on the floor (without arm movement, 2.05 ± 2.61; with arm movement, 3.24 ± 3.42) and bridging on the ball (without arm movement: 2.95 ± 3.87; with arm movement: 5.77 ± 4.85) showed significant main effects for, and significant interaction between the intervention and bridge factors. However, no significant main effects or interaction were found for the MF/ES ratio. These findings suggest that integrating arm movements during bridge exercises may be used to provide preferential loading to certain trunk muscle groups and that these effects may be better derived by performing bridge exercises on a therapeutic ball.     

Effect of sophora japonica total flavonoids on pancreas,kidney tissue morphology of streptozotocin-induced diabetic mice model

To observe effect of sophora japonica total flavonoids on pancreas, kidney tissue morphology of streptozotocin-induced diabetic mice model. Mice received tail vein injection of streptozotocin (60 mg/kg) for diabetes modeling. The model mice were divided into five groups, to be respectively fed with high, middle and small doses of sophora japonica total flavonoids solution, metformin solution and saline of the same volume. Another blank control group was set to be fed with saline of the same volume. The mice were administered once a day for 30 consecutive days, to be euthanatized after fasting blood glucose level testing on 30th day with pancreas, kidney taken out for pathological section and microscopic examination. The mice chain streptozotocin diabetes modeling was successful, with significant pathological changes (P < 0.01) in pancreas, kidney. Compared with model group, high, middle and small doses of sophora japonica total flavonoids could significantly alleviate streptozotocin-induced pancreas, kidney damage (P < 0.01). Conclusion: Sophora japonica total flavonoids can effectively alleviate pancreas, kidney injury of streptozotocin-induced diabetic mice model.