Sophisticated biofidelic finite element (FE) models of sideways falls are an emerging tool for predicting hip fracture risk. We adapted an existing experimental setup for in-silico trials by creating an automated workflow to build FE models of the experiment and characterizing it with respect to the effects of limited CT scan coverage. Limited CT scan coverage was simulated by shortening the femur (25–175mm distal to the greater trochanter), misaligning the femur up to 5 degrees, and using a morphed template pelvis. We compared impact force error (EBL) of the FE results to the existing experimental results. We then characterized the limited CT scan coverage with respect to the impact force (EI), femur force (EF), and fragility ratios based on the impact force (EFRI) and the femur force (EFRF) by comparing results to a model without any of these scan-related errors introduced. In general, the baseline simulations agreed well with the experiments (EBL: μ = − 0.007 kN, σ = 0.409 kN). When scan coverage errors were introduced, the errors were small (EI: μ = 0.082kN, σ = 0.232kN; EF: μ = 0.063 kN, σ = 0.228 kN; EFRI: μ = − 0.00, σ = 0.058; EFRF: μ = − 0.012, σ = 0.074). The pelvis template used explained the most variance of the output measures (EI R2 = 0.876; EF R2 = 0.880; EFRI R2 = 0.901; EFRFR2 = 0.884). These results indicate that this automated methodology is suitable for typical scan coverages encountered clinically, and future work should use this workflow to explore fragility fractures in larger clinical cohorts.

The mechanisms of whiplash injury remain poorly understood. One theory suggests that the characteristic inertial loading of the head and neck in motor vehicle collisions can produce injurious cerebrospinal fluid (CSF) pressure transients in the cervical spine. However, these in vivo CSF pressure responses have not yet been adequately characterized. This study used a pig model to characterize the cervical CSF pressure responses to head kinematic inputs in extension (simulating low-speed rear-end collisions with no head restraint) and flexion (simulating low-speed frontal collisions). We also compared the pressure and pressure impulses at three spinal levels to determine if the pressure transient responses differ spatially. Four anesthetized pigs were instrumented with intrathecal pressure transducers placed at the C2, C5, and C7 levels. A servomotor system was programmed to actuate the head through specific trajectories to model two extension, and two flexion, whiplash exposures. During the extension tests, mean peak pressure transients ranged from − 31.2 to 148.7 mmHg, whereas during the flexion tests, mean peak pressure transients ranged from − 50.8 to 126.9 mmHg. Peak individual responses ranged from − 71.1 to 244.8 mmHg across all tests. Pressure impulses reached a maximum of 6.77 mmHg·s. Peak pressure and pressure impulses were largest at the C5 and C7 levels during extension exposures and at the C2 level in flexion exposures. The reported pressure and pressure impulse responses could be used to determine neural tissue tolerances relevant to whiplash injury and contribute to the development and validation of computational models of whiplash.

Low-density expanded polystyrene (EPS) foams are widely used in lightweight energy absorption systems such as helmets due to their ability to readily mold into complex geometries. However, varying material flow and cooling rates during manufacturing produce exterior skin layers with substantially higher density and aspect ratio from the core, and the resultant mechanical properties have not been quantified. Previous studies assumed EPS foams were homogeneous, overlooking or intentionally removing the skin from test specimens and constrain their scopes to out-of-plane compression. In this study, closed-cell EPS foam pucks of 30, 50, 80, and 100 g/L were tested under in-and out-of-plane compression at loading rates spanning 0.001–10/s. Specimens were prepared with as molded and core (skin removed) configurations to quantify anisotropy from heterogeneity. Measurements revealed a 98% ± 8% higher density in the skin layers relative to nominal material density and cells skewed 41% ± 6% in the in-plane direction. As-molded specimens exhibited a 38% ± 4% higher plateau stress for in-plane loading compared to out-of-plane, highlighting foam cell elongation as a key strengthening mechanism. Quasi-orthotropic behavior was observed for the core foam material, which possessed more evenly sized cells. Digital image correlation quantified rate-dependent strain localization, providing novel evidence of internal pressure redistribution from viscous gas dynamics within the EPS beads, with 39% lower peak true strains, on average, measured at 10/s compared to 0.001/s. Unloading data also revealed progressive increases in post-crushing strain recovery, increasing an order of magnitude from 0.04 mm/mm to 0.42 mm/mm between 0.001-10/s for the 30 g/L group, confirming more even load distribution and cell fracture mitigation at elevated rates.

In comparisons of similar crashes between sexes, females exhibit an elevated risk of injury to the cervical spine and ribs. This preliminary study aims to investigate the relationship between upper body shape and shoulder belt fit, which may provide further insight into sex-based differences in seat belt loading and potential injury patterns. A non-ferromagnetic seat was fabricated for use with an open magnetic resonance (MR) imaging system, as well as a seat belt made of standard automotive webbing material with MR-visible markers. MR scans were acquired for 10 volunteers (5 female, 5 male) in an upright self-selected seat back position. This analysis focused on the shoulder belt positioning relative to the sternum and clavicle, with consideration of soft tissue interactions on this routing. Females in this study exhibited over three times greater range in the distance of the shoulder belt to the top of the sternum (SBD) compared to the males, despite similar or less variability than males in all gross anthropometric measures (SBD range, females: 21-116 mm, males: 51-78 mm). Such differences in variability highlight the diversity in routing patterns that may be influenced by different body geometries, such as breast tissue volume and distribution. Understanding how shoulder belt fit varies among and within diverse occupant populations highlights the need for improving the robustness of restraint design and performance.

BACKGROUND:Correct seatbelt use during pregnancy is critical for ensuring maternal and fetal safety during a motor vehicle crash. This study aimed to investigate seatbelt use among pregnant vehicle drivers in Australia, focusing on correct seatbelt positioning and the potential influence of comfort and the receipt of seatbelt information. METHOD:An online survey was completed by 1,491 participants (M = 33.2 years, SD = 4.1, Range = 18.0 - 50.0 years). RESULTS:While nearly all participants (99.1%) reported 'always' wearing their seatbelt while driving a vehicle, only 41.4% met the correct seatbelt positioning criteria, defined as positioning the lap belt under the belly and low over the upper thighs and the shoulder belt between the breasts. Despite increased discomfort with seatbelt use as pregnancy advanced, discomfort was not significantly associated with correct seatbelt positioning. Additionally, while most participants had not received information about seatbelt use during pregnancy (87.7%), those who did had better knowledge (96.2% vs. 90.5%, χ2(1) = 7.16, p < 0.05), and were more likely to meet all three criteria for correct seatbelt positioning during pregnancy (56.8% vs. 39.3%, χ2(1) = 20.26, p < 0.001), than participants who had not received information (90.5%). However, receiving information did not necessarily increase confidence in correct seatbelt use, as participants who had received information were actually less likely to be confident in their ability to use the seatbelt correctly (3.3% vs. 6.6%, χ2(2) = 8.24, p < 0.05). CONCLUSIONS:These findings highlight a significant gap in correct seatbelt positioning among pregnant occupants and the scope for substantial improvement in correct positioning by providing specific information on seatbelt use during pregnancy. PRACTICAL APPLICATIONS:To improve correct seatbelt use among pregnant individuals, public health messaging should be enhanced, and obstetrician-gynaecologists, nurses and other healthcare professionals should provide clear guidance on correct seatbelt positioning throughout the pregnancy. Future research should focus on developing effective educational strategies, assessing vehicle design improvements for comfort and safety, and exploring other factors influencing correct seatbelt use during pregnancy.

BACKGROUND:Fall-related traumas like hip fracture are a common yet devastating injury with poor outcomes. Characterizing fracture biomechanics and bone-implant kinematics is essential to increase our understanding of these events to inform treatment and prevention strategies. METHODS:This study developed a bilateral high-speed x-ray methodology for the real-time capture of fracture and kinematic data near the hip during fall impacts. High speed x-ray was applied to capture fall impacts of seven cadaveric pelvis-femur specimens encased in a soft tissue surrogate, using a previously developed method. In these specimens, the intact proximal femur had been prophylactically reinforced with an intramedullary nailing system intended to prevent fragility fractures. The feasibility of extracting 3D kinematic data from x-ray data was investigated. FINDINGS:The HSXR system demonstrated visual clarity and sufficient resolution for capturing skeletal fracture and kinematics. The data in this study revealed fracture and newly-seen deformations of the pelvis, highlighting the ability of the x-ray system to document real-time fracture and kinematic events. Kinematic data in 3D was extracted with sufficient accuracy for one specimen. INTERPRETATION:These results demonstrate the merit of high-speed x-ray for studying periprosthetic fracture, which is of increasing relevance due to increasing populations with orthopedic hardware. Application of this method advances our understanding of impact-related biomechanics and fracture mechanics during a clinically-relevant fall from standing.

The origin and mechanics of whiplash injury from motor vehicle collisions are poorly understood. Among the proposed injury mechanisms, the inertial loading of the head and neck during whiplash exposures is theorized to produce injurious cerebrospinal fluid pressure (CSFP) transients. To better understand the mechanics and modal behavior of CSFP transients during whiplash exposures, we quantified the time-frequency relationship between input head kinematics and cervical CSFP responses in an in vivo pig model. Wavelet coherence analysis was used to correlate seven head kinematic parameters (including temporal Neck Injury Criterion, NIC) with CSFP during simulated extension and flexion whiplash exposures. Overall, the first and last 50 ms of exposures, and frequency ranges between 30-65 Hz had larger coherences between head kinematics and CSFP, with higher coherences in extension exposures than flexion exposures. NIC did not universally outperform other head kinematic parameters as a correlate of CSFP. These findings highlight the complexity of the dynamics involved in generating CSFP transients in the cervical spine during whiplash exposures.

Hip fracture prevention approaches like prophylactic augmentation devices have been proposed to strengthen the femur and prevent hip fracture in a fall scenario. The aim of this study was to validate the finite element model (FEM) of specimens augmented by prophylactic intramedullary nailing in a simulated sideways fall impact against ex vivo experimental data. A dynamic inertia-driven sideways fall simulator was used to test six cadaveric specimens (3 females, 3 males, age 63-83 years) prophylactically implanted with an intramedullary nailing system used to augment the femur. Impact force measurements, pelvic deformation, effective pelvic stiffness, and fracture outcomes were compared between the ex vivo experiments and the FEMs. The FEMs over-predicted the effective pelvic stiffness for most specimens and showed variability in terms of under- and over-predicting peak impact force and pelvis compression depending on the specimen. A significant correlation was found for time to peak impact force when comparing ex vivo and FEM data. No femoral fractures were found in the ex vivo experiments, but two specimens sustained pelvic fractures. These two pelvis fractures were correctly identified by the FEMs, but the FEMs made three additional false-positive fracture identifications. These validation results highlight current limitations of these sideways fall impact models specific to the inclusion of an orthopaedic implant. These FEMs present a conservative strategy for fracture prediction in future applications. Further evaluation of the modelling approaches used for the bone-implant interface is recommended for modelling augmented specimens, alongside the importance of maintaining well-controlled experimental conditions.

Letter from the Focus Issue Editors

Variability in body shape and soft tissue geometry have the potential to affect the body's interaction with automotive safety systems. In this study, we developed a methodology to capture information on body shape, superficial soft tissue geometry, skeletal geometry, and seatbelt fit relative to the skeleton-in automotive postures-using Open Magnetic Resonance Imaging (MRI). Volunteer posture and belt fit were first measured in a vehicle and then reproduced in a custom MRI-safe seat (with an MR-visible seatbelt) placed in an Open MR scanner. Overlapping scans were performed to create registered three-dimensional reconstructions spanning from the thigh to the clavicles. Data were collected with ten volunteers (5 female, 5 male), each in their self-selected driving posture and in a reclined posture. Examination of the MRIs showed that in the males with substantial anterior abdominal adipose tissue, the abdominal adipose tissue tended to overhang the pelvis, narrowing in the region of the Anterior Superior Iliac Spine (ASIS). For the females, the adipose tissue depth around the lower abdomen and pelvis was more uniform, with a more continuous layer superficial to the ASIS. Across the volunteers, the pelvis rotated rearward by an average of 62% of the change in seatback angle during recline. In some cases, the lap belt drew nearer to the pelvis as the volunteer reclined (as the overhanging folds of adipose tissue stretched). In others, the belt-to-pelvis distance increased as the volunteer reclined. These observations highlight the importance of considering both interdemographic and intrademographic variability when developing tools to assess safety system robustness.

Objective This study aims to establish best practices and guidelines to ensure that experimental research utilizing Postmortem Human Subjects (PMHS) for injury prevention adheres to relevant ethical principles, which are also commonly accepted in research involving human tissues and living subjects. Furthermore, it reviews existing literature to underscore the pivotal role of PMHS testing in evaluating the efficacy of safety systems, with a particular focus on airbag performance. Methods This paper conducts an examination of the primary ethical principles governing human subject research as outlined in the Declaration of Helsinki (1965) and traces their evolution up to the latest framework proposed by the Council for International Organizations of Medical Sciences (CIOMS) in 2002. Input was solicited from international experts and laboratories experienced in PMHS testing to understand how these ethical principles are implemented in practice. This is complemented by a comprehensive review of literature that assesses the contribution of PMHS testing to airbag performance enhancements in frontal impacts. Results The findings underscore the importance of informed consent from donors or their next-of-kin, as highlighted in CIOMS declarations, to ensure the ethical integrity of the donation process in line with international standards. The study also finds it customary for an independent review board to evaluate the research methodology and the necessity of employing PMHS tissue over alternative methods, such as computational models or crash test dummies. Despite various national regulations on human subject participation and living tissue research, no specific legal framework governing PMHS tissue use was identified. The systematic literature review revealed that PMHS testing has been crucial in identifying potential injury mechanisms not detected by Anthropomorphic Test Devices (ATD), significantly contributing to the enhancement of computer human body models and the biofidelity of crash test dummies. Conclusion The International Council on the Biomechanics of Injury (IRCOBI) recognizes the need to provide guidance for research involving human cadaveric tissue to be conducted with the highest ethical standards. This study proposes five recommendations to ensure adherence to these ethical principles in PMHS testing, highlighting the paramount importance of obtaining informed consent and securing independent committee approval. Moreover, IRCOBI emphasizes that until a thorough understanding of tissue damage tolerance levels is achieved and human surrogates, such as ATDs or Human Body Models (HBM), reach full biofidelity, the use of human cadavers remains indispensable for developing effective injury prevention strategies and measures.

Seventeen research posters were prepared and presented by student authors. The posters covered a wide breadth of works-in-progress and recently completed projects. Topics included a variety of body regions and injury scenarios: * Biofidelity Corridors of Powered Two-Wheeler Rider Kinematics from Full-Scale Crash Testing Using Postmortem Human Subjects, Meringolo et al. * Cervical Vertebral and Spinal Cord Injuries Remain Overrepresented in Rollover Occupants, Al-Salehi et al. * The Effect of Surfaces on Knee Biomechanics during a 90-Degree Cut, Rhodes et al. * Investigating the Variabilities in the Spinal Cord Injury in Pig Models Using Benchtop Test Model and Ultrasound Analyses, Borjali et al. * Relationship between Tackle Form and Head Kinematics in Youth Football, Holcomb et al. * Comparing Motor Vehicle Collision Injury Incidence between Pregnant and Nonpregnant Individuals: A Case–Control Study, Levine et al. * Development of an Automated Pipeline to Characterize Full Rib Cage Shape Variability, Robinson et al. * Soft Tissue Force Attenuation and Redistribution during Lateral Hip Impacts, Pretty et al. * Hybrid III Small Female Neck Interaction with a Driver Airbag: Preliminary Observations, Boyle et al. * Changes in Youth Football Athletes’ Oculomotor Task Metrics across Three High School Seasons of Play, Pang et al. * Measurement of Shielding Stiffness in Ice Hockey, Vakili et al. * Investigating the Relationship between Vehicle-Based and Biomechanics Injury Metrics in Car-to-End Terminal Crashes Using a Human Finite Element Model, Buckland et al. * On-Field Instrumented Mouthguard Coupling, Luke et al. * Investigation of Rear-Seat Occupant Safety during High-Speed Frontal Crashes Using GHBMC M50-O, Dahiya et al. * Deformable Headform Design Choices: An Evaluation of Brain Simulant Stiffness Influence on Intracranial Displacements and Strain, Xu et al. * Changes in Neurocognitive Outcomes among Youth Football Teams Participating in an Intervention, Marks et al. * A Parametric Skeleton Model of Human Upper Extremities Accounting for Morphological Variations among the Diverse Population, Neeluru et al.

Fragility fracture of the hip is a global health concern with generally poor outcomes. Clinical studies have shown prophylactic augmentation of the femur to be a plausible intervention with success in some approaches; however, its use is not yet widespread in the clinical community. We aimed to evaluate the efficacy and clinical safety of prophylactic intramedullary nailing for hip fracture prevention after a fall impact in six cadaveric pelvis-femurs. Post-fall fracture status of the native specimens was determined in a virtual control group built using a validated and peer-reviewed finite element method. A commercially available intramedullary nailing system was prophylactically implanted in all specimens. After augmentation, specimens were subjected to an experimental sideways fall impact and inspected for fracture. Overall, fracture status was unchanged or lowered in severity in the augmented group compared to the native control group. No sign of femur fracture was found in the group augmented by intramedullary nailing, but two augmented specimens exhibited pelvis fractures after the impact. No safety concerns associated with prophylactic nailing were found. These results suggest that prophylactic nailing may reduce the potential for hip fracture in a sideways fall impact but would not reduce the likelihood of pelvis fracture, and may shift femur fractures to instead be pelvis fractures. This study provides a robust biomechanical evaluation of prophylactic augmentation with a device already familiar to orthopedic surgeons, broadening the options currently considered for the prevention of hip fractures.

Background: Facet fractures are frequently associated with clinically observed cervical facet dislocations (CFDs); however, to date there has only been one experimental study, using functional spinal units (FSUs), which has systematically produced CFD with concomitant facet fracture. The role of axial compression and distraction on the mechanical response of the cervical facets under intervertebral motions associated with CFD in FSUs has previously been shown. The same has not been demonstrated in multi-segment lower cervical spine specimens under flexion loading (postulated to be the local injury vector associated with CFD). Methods: This study investigated the mechanical response of the bilateral inferior C6 facets of thirteen C5-C7 specimens (67 +/- 13 yr, 6 male) during non-destructive constrained flexion, superimposed with each of five axial conditions: (1) 50 N compression (simulating weight of the head); (2-4) 300, 500, and 1000 N compression (simulating the spectrum of intervertebral compression resulting from neck muscle bracing prior to head-first impact and/or externally applied compressive forces); and, (5) 2 mm of C6/C7 distraction (simulating the intervertebral distraction present during inertial loading of the cervical spine by the weight of the head). Linear mixed-effects models (alpha = 0.05) assessed the effect of axial condition. Results: Increasing amounts of intervertebral compression superimposed on flexion rotations, resulted in increased facet surface strains (range of estimated mean difference relative to Neutral: maximum principal = 77 to 110 mu epsilon, minimum principal = 126 to 293 mu epsilon, maximum shear = 203 to 375 mu epsilon) and angular deflection of the bilateral inferior C6 facets relative to the C6 vertebral body (range of estimated mean difference relative to Neutral = 0.59 degrees to 1.47 degrees). Conclusions: These findings suggest increased facet engagement and higher load transfer through the facet joint, and potentially a higher likelihood of facet fracture under the compressed axial conditions.

Rollover crashes continue to be a substantial public health issue in North America. Previous research has shown that the cervical spine is the most injured spine segment in rollovers, but much of the past research has focused on risk factors rather than the actual cervical spine injuries. We sought to examine how different types of cervical spine injuries (vertebral and/or cord injury) vary with different occupant-related factors in rollovers and to compare these with non-rollovers. We obtained crash and injury information from the National Automotive Sampling System–Crashworthiness Data System (NASS-CDS) for 2005–2015 and Crash Investigation Sampling System (CISS) for 2017–2022. Based on weighted data, we calculated relative risks to assess how occupant sex, seat belt use, ejection status, and fatal outcome relate to the rate of different cervical spine injuries in rollovers and non-rollovers. In NASS-CDS occupants with cervical spine injuries (N = 111,040 weighted cases), about 91.5

Porcine models in injury biomechanics research often involve measuring head or brain kinematics. Translation of data from porcine models to other biomechanical models requires geometric and inertial properties of the pig head and brain, and a translationally relevant anatomical coordinate system (ACS). In this study, the head and brain mass, center of mass (CoM), and mass moments of inertia (MoI) were characterized, and an ACS was proposed for the pre-adolescent domestic pig. Density-calibrated computed tomography scans were obtained for the heads of eleven Large White × Landrace pigs (18–48 kg) and were segmented. An ACS with a porcine-equivalent Frankfort plane was defined using externally palpable landmarks (right/left frontal process of the zygomatic bone and zygomatic process of the frontal bone). The head and brain constituted 7.80 ± 0.79

Various femoral augmentation designs have been investigated over the past decade for the prevention of geriatric hip fracture. The experimental methods used to evaluate the efficacy of these augmentations have not been critically evaluated or compared in terms of biofidelity, robustness, or ease of application. Such parameters have significant relevance in characterizing future clinical success. In this study we aimed to use a scoping review to summarize the experimental studies that evaluate femoral augmentation approaches, and critically evaluate commonly applied protocols and identify areas for concordance with the clinical situation. We conducted a literature search targeting studies that used experimental test methods to evaluate femoral augmentation to prevent geriatric fragility fracture. A total of 25 studies met the eligibility criteria. The most commonly investigated augmentation to date is the injection of bone cement or another material that cured in situ, and a popular subsequent method for biomechanical evaluation was to load the augmented proximal femur until fracture in a sideways fall configuration. We noted limitations in the clinical relevance of sideways fall scenarios being modeled and large variance in the concordance of many of the studies identified. Our review brings about recommendations for enhancing the fidelity of experimental methods modeling clinical sideways falls, which include an improved representation of soft tissue effects, using outcome metrics beyond load-to-failure, and applying loads inertially. Effective augmentations are encouraging for their potential to reduce the burden of hip fracture; however, the likelihood of this success is only as strong as the methods used in their evaluation.

Traumatic brain injury (TBI) is an established risk factor for neurodegenerative diseases. In this study, we used the Closed Head Injury Model of Engineered Rotational Acceleration (CHIMERA) to investigate the effects of a single high-energy TBI in rTg4510 mice, a mouse model of tauopathy. Fifteen male rTg4510 mice (4 mo) were impacted at 4.0 J using interfaced CHIMERA and were compared to sham controls. Immediately after injury, the TBI mice showed significant mortality (7/15; 47%) and a prolonged duration of loss of the righting reflex. At 2 mo post-injury, surviving mice displayed significant microgliosis (Iba1) and axonal injury (Neurosilver). Western blotting indicated a reduced p-GSK-3β (S9):GSK-3β ratio in TBI mice, suggesting chronic activation of tau kinase. Although longitudinal analysis of plasma total tau suggested that TBI accelerates the appearance of tau in the circulation, there were no significant differences in brain total or p-tau levels, nor did we observe evidence of enhanced neurodegeneration in TBI mice compared to sham mice. In summary, we showed that a single high-energy head impact induces chronic white matter injury and altered GSK-3β activity without an apparent change in post-injury tauopathy in rTg4510 mice.