A computational study of injury severity and pattern sustained by overweight drivers in frontal motor vehicle crashes

Obesity as a Risk Factor for Adverse Outcomes After Pedestrian Trauma Accidents in the Pediatric Population

OBJECTIVE

The aim of the study is to determine whether overweight or obese children are at an increased risk for injury and adverse outcomes following pedestrian motor vehicle accidents.

METHODS

We performed a retrospective study of patients between the ages of 2 and 17 who were pedestrians injured in a collision with a motorized vehicle, presenting to a level 1 trauma center, between January 1, 2010, to December 31, 2021. Patients with admission weights falling above the 90th percentile of the Centers for Disease Control and Prevention's sex-specific growth charts were identified as overweight/obese, those below the cutoff were categorized as nonobese. Groups were compared regarding demographics, mechanism of injury, Injury Severity Score, and Abbreviated Injury Scale by body region of injury. Outcome measures included hospital admission, length of hospital stay, intensive care unit (ICU) admission, ICU length of stay, and mortality.

RESULTS

Of the 306 patients included, 72 (23.5%) were overweight/obese and 234 (76.5%) were nonobese. The mean Injury Severity Score scores were higher among overweight/obese patients (5.37 vs 8.74, P = 0.008). Overweight/obese children were more likely to sustain severe abdominal injuries (Abbreviated Injury Scale ≥ 3) (12.2% vs 5.1%; odds ratio [OR], 2.64; 95% CI, 1.07-6.56; P = 0.030), be admitted to the hospital (94.5% vs 74.3%; OR, 12.07; 95% CI, 2.87-50.72; P < 0.001), require ICU admission (31.0% vs 20.0%, OR, 1.87; 95% CI, 1.03-3.36; P = 0.036), and require a longer ICU stay (0.9 vs 0.4 days, P = 0.014) compared with nonobese patients.

CONCLUSIONS

Obese and overweight children are at increased risk for higher injury severity scores, severe abdominal injuries, and ICU admission after pedestrian motor vehicle accidents.

Evaluation of the cushion effect in blunt abdominal trauma patients: A computerized analysis

BACKGROUND

Obesity may serve as a protective factor in blunt abdominal trauma (BAT) patients due to a "cushion effect". In this study, we aim to use computed tomography (CT) scans to measure abdominal adiposity and its correlation with injury severity in BAT patients.

METHODS

We conducted a retrospective analysis of male BAT patients who had undergone CT scans. Subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) were manually measured and height-normalized for analysis at lumbar levels L2 and L3. Statistical methods were used to compare differences in adiposity between patients with and without severe abdominal injuries. For controls, we also compared adipose tissue in patients with and without severe trauma to the chest, where less fat typically accumulates.

RESULTS

We included 361 male participants and conducted a comparative analysis of their demographic and injury characteristics. Patients without severe abdominal injuries had significantly higher SAT and VAT indices at both L2 and L3 (p < 0.05). However, these measures showed no significant differences between patients with and without severe chest trauma. Solid organ injuries, particularly liver injuries, were associated with decreased SAT and VAT.

CONCLUSION

Increase abdominal adiposity was linked to lower abdominal injury severity and solid organ injuries, particularly liver injuries. In addition to conventional BMI for evaluating obesity, either subcutaneous or visceral adipose tissue over lumbar levels L2 and L3 can be used to assess the "cushion effect."

Creativity in energy balance, obesity and feeding behavior research, some thoughts

This review provides an overview of examples of especially creative work related to the fields of ingestive behavior, energetics (defined as the study of the acquisition, storage, and use of metabolizable energy by biological organisms and the causes and consequences of such acquisition, storage, and use), and nutrition, focusing on both individual works and discoveries, as well as bodies of works and in some cases the working styles of particular scientists. The paper then discusses some principles extracted from our observations as well as from the literature on creativity pointing out some factors that seem to make for more creative science and that can be done by individuals to promote creativity in their own work. Finally, we end with a short set of tips for the field in general to promote creativity among our ranks broadly.

Strain-dependent shear properties of human adipose tissue in vivo

INTRODUCTION

Human adipose tissue (fat) deforms substantially under normal physiological loading and during impact. Thus, accurate data on strain-dependent stiffness of fat is essential for the creation of accurate biomechanical models. Previous studies on ex vivo samples reported human fat to be nonlinear and viscoelastic. When static compression is combined with magnetic resonance (MR) elastography (an imaging technique used to measure viscoelasticity in vivo), the large deformation properties of tissues can be determined. Here, we use magnetic resonance elastography to quantify fat shear modulus in vivo under increasing compressive strain and compare it to the underlying passive gluteal muscle.

METHODS

The right buttocks of ten female participants were incrementally compressed at four levels while MR elastography (50 Hz) and mDixon images were acquired. Maps of tissue shear modulus (G*) were reconstructed from the MR elastography phase images. Tissue strain was estimated from registration of deformed and undeformed mDixon images. Linear mixed models were fit to the natural logarithm of the compressive strain and shear modulus data for each tissue.

RESULTS

Shear modulus increased in an exponential relationship with compressive strain in fat: Gfat*=748.5*Cyy-1.18Pa, and to a lesser extent in muscle: Gmuscle*=956.4*Cyy-0.36Pa. The baseline (undeformed) stiffness of fat was significantly lower than that of muscle (mean G*fat = 752 Pa, mean G*muscle = 1000 Pa, paired samples t-test, t = -4.24, p = 0.001). However, fat exhibited a significantly higher degree of strain dependence (characterised by the exponent of the curve, t = -6.47, p = 0.0001).

CONCLUSION

Static compression of human adipose tissue results in an increase in apparent viscoelastic shear modulus (stiffness), in an exponentially increasing relationship. The relationships defined here can be used in the development of physiologically realistic computational models for impact, injury and biomechanical modelling.

Protective Role of Obesity on Trauma Impact: A Retrospective Analysis of Patients with Surgical Blunt Bowel Mesenteric Injury Due to Road Traffic Accidents

Background

The "cushion effect" theory proposes that increased body mass index (BMI) is associated with less severe abdomen injury following blunt abdomen trauma, while the "obesity paradox" describes the protective effect of obesity against mortality. However, most previous studies used the abdominal abbreviated injury scale as the outcomes seemed to be inadequate owing to the injuries to the abdominal organs, such as the spleen and liver, which may be attributable to the force that caused the chest trauma. This study aimed to use adult trauma patients with surgical blunt bowel mesenteric injuries (BBMIs) to investigate the influence of obesity on the clinical outcomes and overall morbidities.

Methods

This retrospective study reviewed the data of all hospitalized trauma patients between 2009 and 2019 and included all patients with surgically proven small bowel, colon, or mesenteric injuries due to a road traffic accident. Comparison of the outcomes was performed among 123 patients with surgically proven BBMI, who were categorized by BMI into the normal-weight (n = 73, BMI<25 kg/m²), overweight (n = 37, 25≤BMI≤30 kg/m²), and obese groups (n = 13, BMI>30 kg/m²).

Results

The obese group had a significantly lower incidence of isolated bowel injury (0%) compared with the normal-weight (35.6%) and overweight (16.2%) groups (p=0.005), but with higher incidence of isolated mesenteric injury or combined injury, although this was not significant. The obese group (92.3%) had a significantly higher percentage of overall morbidity than the normal-weight (61.6%) and overweight (70.3%) groups (p = 0.047). No significant difference was observed in the in-hospital mortality and 24-hour mortality among the three study groups.

Conclusion

The study findings do not support the existence of a cushion effect and obesity paradox of obesity in blunt abdominal trauma.

Does a "Cushion Effect" Really Exist? A Morphomic Analysis of Vulnerable Road Users with Serious Blunt Abdominal Injury

Introduction: The severity of injury from motor vehicle crashes (MVCs) depends on complex biomechanical factors, and the bodily features of the injured person account for some of these factors. By assuming that vulnerable road users (VRUs) have limited protection resulting from vehicles and safety equipment, the current study analyzed the characteristics of fat distribution measured by computed tomography (CT) imaging and investigated the existence of a "cushion effect" in VRUs. Materials and Methods: This retrospective study enrolled 592 VRUs involved in MVCs who underwent CT scans. Visceral fat area and subcutaneous fat cross-sectional area were measured and adjusted according to total body area (TBA) and are presented as the visceral fat ratio and the subQ fat ratio (subcutaneous fat ratio). Risk factors for serious abdominal injury (maximum abbreviated injury scale (MAIS_abd ≥ 3)) resulting from MVCs were determined by univariate and multivariate analysis. Results: MAIS_abd ≥ 3 was observed in 104 (17.6%) of the patients. The subQ fat ratio at the L4 vertebral level was significantly lower in the MAIS_abd ≥ 3 group than in the MAIS_abd < 3 group (24.9 ± 12.0 vs. 28.1 ± 11.9%; p = 0.015). A decreased L4 subQ fat ratio was associated with a higher risk for MAIS_abd ≥ 3 in multivariate analysis (odds ratio 0.063; 95% CI 0.008-0.509; p = 0.009). Conclusion: The current study supported the "cushion effect" theory, and protection was apparently provided by subcutaneous fat tissue. This concept may further improve vehicle and safety designation in the future.

The biomechanics of lower limb injuries in frontal-impact road traffic collisions

Aim

We aimed to review the biomechanics of lower limb injuries caused by frontal-impact road traffic collisions.

Methods

In this narrative review, we identified articles through pubmed, Scopus and Science Direct search engines for the period of 1990–2014. Search terms included: “biomechanics”, “lower limb injury”, “hip injury”, “knee injury”, “foot and ankle injury” and “frontal impact collision”. We studied factors affecting the anatomical site, frequency and severity of the injuries.

Results

The most common reported mechanisms of injury were: the impaction of the knee with the dashboard resulting in acetabular fracture or posterior hip dislocation; and toepan intrusion in combination with forceful application of the brake resulting in foot and ankle fractures. The probability of an occupant sustaining significant injury to the hip is increased in taller males, and being out of position during the collision. The probability of an occupant sustaining a fracture to the foot and ankle is increased in shorter female occupants with a large overlap impact or a near oblique collision.

Conclusion

Understanding the biomechanics of frontal-impact road traffic collisions is useful in alerting clinicians to the potential lower limb injuries sustained in these collisions.

Evaluating the "cushion effect" among children in frontal motor vehicle crashes

BACKGROUND

The "Cushion Effect," the phenomenon in which obesity protects against abdominal injury in adults in motor vehicle accidents, has not been evaluated among pediatric patients. This work evaluates the association between subcutaneous fat cross-sectional area, quantified using analytic morphomic techniques and abdominal injury.

METHODS

This retrospective study includes 119 patients aged 1 to 18years involved in frontal impact motor vehicle accidents (2003-2015) with computed tomography scans. Subcutaneous fat cross-sectional area was measured and converted to age- and gender-adjusted percentiles from population-based normative data. Multivariable analysis determined the risk of the primary outcome, Maximum Abbreviated Injury Scale (MAIS) 2+ abdominal injury, after adjusting for age, weight, seatbelt status, and impact rating.

RESULTS

MAIS 2+ abdominal injuries occurred in 20 (16.8%) of the patients. Subcutaneous fat area percentile was not significantly associated with MAIS 2+ abdominal injury on multivariable logistic regression (adjusted Odds Ratio, 0.86; 95% CI, 0.72-1.03; p=0.10).

DISCUSSION

The "cushion effect" was not apparent among pediatric frontal motor vehicle crash victims in this study. Future work is needed to investigate other analytic morphomic measures. By understanding how body composition relates to injury patterns, there is a unique opportunity to improve vehicle safety design.

LEVEL OF EVIDENCE

Prognosis Study, Level III.

Impact Response Comparison Between Parametric Human Models and Postmortem Human Subjects with a Wide Range of Obesity Levels

OBJECTIVE

Field data analyses have shown that obesity significantly increases the occupant injury risks in motor vehicle crashes, but the injury assessment tools for people with obesity are largely lacking. The objectives of this study were to use a mesh morphing method to rapidly generate parametric finite element models with a wide range of obesity levels and to evaluate their biofidelity against impact tests using postmortem human subjects (PMHS).

METHODS

Frontal crash tests using three PMHS seated in a vehicle rear seat compartment with body mass index (BMI) from 24 to 40 kg/m² were selected. To develop the human models matching the PMHS geometry, statistical models of external body shape, rib cage, pelvis, and femur were applied to predict the target geometry using age, sex, stature, and BMI. A mesh morphing method based on radial basis functions was used to rapidly morph a baseline human model into the target geometry. The model-predicted body excursions and injury measures were compared to the PMHS tests.

RESULTS

Comparisons of occupant kinematics and injury measures between the tests and simulations showed reasonable correlations across the wide range of BMI levels.

CONCLUSIONS

The parametric human models have the capability to account for the obesity effects on the occupant impact responses and injury risks.

Demand for specialised training for the obese trauma patient: National ATLS expert group survey results

BACKGROUND

The growing incidence of obesity in Western populations continues to place new stressors on health systems. Obese trauma patients present particular challenges across the entirety of the patient care pathway, and are at risk of higher lengths of stay, morbidity, and mortality. This study sought to assess a national group of trauma experts' opinions and knowledge regarding the management of obese trauma.

METHODS

A questionnaire was circulated to a trauma training providers and national steering committee members at a UK national Advance Trauma Life Support meeting. Demographic, knowledge, and opinion data was collected and collated for analysis.

RESULTS

109 questionnaires were returned (73% response rate). Broad agreement was reached that obese trauma patients were more challenging to manage (96.2% agreement) and suffered worse outcomes (89.9%). Only 22.2% felt their hospitals possessed appropriate resources to facilitate management. Up to a third of respondents had personally witnesses errors in care due to patient obesity. 90% believed specialist training for obese trauma could improve care.

DISCUSSION

There is broad consensus amongst UK trauma providers that obese trauma patients are at risk of poorer outcomes and errors in care. Knowledge and preparedness of centres to manage these patients is variable. There was broad consensus that specialist training for the management of obese trauma patients may improve outcomes.

Risk and injury severity of obese child passengers in motor vehicle crashes

OBJECTIVE

To investigate the risk and injury severity on the regional body (head, neck, and chest) of obese children in frontal motor vehicle crashes (MVCs).

METHODS

No physical surrogates (i.e., crash dummies) for obese children were available, and experiments on pediatric cadavers were generally not feasible. Therefore, computational models of obese children using medical imaging processing and state-of-the-art modeling techniques were developed. A hybrid modeling technique was used to integrate the finite element model for torso fat layer into the standard multibody model to represent various levels of obese children for 3- and 6-year-old age groups. The models were used to investigate injury severity under various crash scenarios through model simulations.

RESULTS

The head injury criterion and chest acceleration were observed to increase as body mass index (BMI) increased. Meanwhile, no such correlations were found between BMI and neck injury and chest deformation. Forward head and torso excursions were observed to increase as obesity increased, owing to the momentum effect of greater body mass.

CONCLUSIONS

Obese children appeared to have greater risks for head and chest injuries than do their non-obese counterparts in frontal MVCs, owing to higher head and chest accelerations induced by greater body excursion.