Influence of wet surfaces and fall height on pediatric injury risk in feet-first freefalls as predicted using a test dummy

Studies of Acceleration of the Human Body during Overturning and Falling from a Height Protected by a Self-Locking Device

The use of individual fall protection equipment is one of the most commonly applied methods of protecting workers whose worksites are located above the floor level. The safety of the user in such a situation depends on both the proper selection and correct use of such equipment. Additionally, aspects such as minimizing the free-fall distance before the fall arrest, as well as quick notification of an accident and efficient rescue operation, are important factors influencing safety. This paper presents a new testing method for fall arrest equipment using a test stand consisting of the Hybrid III 50th Pedestrian ATD anthropomorphic manikin and measuring set with three-axis acceleration transducers. The proposed method and test stand were developed for the design and testing of new fall protection devices equipped with electronic detection and alarm systems, for which it is necessary to determine acceleration limits in order to determine the alarm threshold. The proposed method is based on the measurement of accelerations that occur during tipping and falling from the height of an anthropomorphic manikin secured by a self-locking device. Two places of attachment of the measuring set with a three-axis acceleration sensor were analyzed at the waist belt of the manikin (abdomen and back). Moreover, the self-locking device lanyard was attached to the two points of the safety harnesses (the front and back point). The aim of the research was to check whether the acceleration values depend on the places of attachment of the measuring and anchored system, as well as to determine their maximum values. Acceleration values corresponding to fall arrest and tipping were analyzed. Limits of acceleration have been established in order to determine the threshold of alarm triggering. The non-parametric Mann-Whitney U test was used to check whether the location of the three-axis acceleration transducer and the position of the self-locking device lanyard attachment affect the value of the recorded acceleration. For results of acceleration measurements when testing the behavior of the manikin during fall arrest, no statistically significant differences were found. For results of acceleration measurements when testing the tipping behavior of the manikin, statistically significant differences occurred. This means that during fall arrest, the location of the three-axis acceleration transducer and the position of the self-locking device lanyard attachment do not matter. This work is a continuation of previous research on accelerations characterizing human body positions occurring during normal physical activities (ADL-activities of daily living).

Head biomechanics of video recorded falls involving children in a childcare setting

The objective of this study was to characterize head biomechanics of video-recorded falls involving young children in a licensed childcare setting. Children 12 to < 36 months of age were observed using video monitoring during daily activities in a childcare setting (in classrooms and outdoor playground) to capture fall events. Sensors (SIM G) incorporated into headbands worn by the children were used to obtain head accelerations and velocities during falls. The SIM G device was activated when linear acceleration was ≥ 12 g. 174 video-recorded falls activated the SIM G device; these falls involved 31 children (mean age = 21.6 months ± 5.6 SD). Fall heights ranged from 0.1 to 1.2 m. Across falls, max linear head acceleration was 50.2 g, max rotational head acceleration was 5388 rad/s², max linear head velocity was 3.8 m/s and max rotational head velocity was 21.6 rad/s. Falls with head impact had significantly higher biomechanical measures. There was no correlation between head acceleration and fall height. No serious injuries resulted from falls—only 1 child had a minor injury. In conclusion, wearable sensors enabled characterization of head biomechanics during video-recorded falls involving young children in a childcare setting. Falls in this setting did not result in serious injury.

Effect of the design of safety harness on the pressures exerted on the user's body in the state of its suspension

AbstractThe presented studies concern the pressure of safety harnesses on the user's body in a state of its suspension. An anthropomorphic dummy was used for simulation of human behaviour in suspension. The test objects included four models of the harnesses of different designs, equipped with attachment elements placed at the back and front of the human body. Pressure mapping sensors of 56 × 56 mm2 surface area and a 2D pressure mapping apparatus were used for the measurements. The parameters characterizing the pressures of the harness belts on the dummy surface were defined. The obtained results demonstrated in which position the pressures exerted on the dummy are the greatest and that they depend mainly on the design of the safety harnesses and their attachment point. The most sensitive points of action of the harness on the user's body have been identified. Guidelines for the construction of the safety harnesses have been formulated.

In vivo soft tissue compressive properties of the human hand

Background/Purpose

Falls onto outstretched hands are the second most common sports injury and one of the leading causes of upper extremity injury. Injury risk and severity depends on forces being transmitted through the palmar surface to the upper extremity. Although the magnitude and distribution of forces depend on the soft tissue response of the palm, the in vivo properties of palmar tissue have not been characterized. The purpose of this study was to characterize the large deformation palmar soft tissue properties.

Methods

In vivo dynamic indentations were conducted on 15 young adults (21–29 years) to quantify the soft tissue characteristics of over the trapezium. The effects of loading rate, joint position, tissue thickness and sex on soft tissue responses were assessed.

Results

Energy absorbed by the soft tissue and peak force were affected by loading rate and joint angle. Energy absorbed was 1.7–2.8 times higher and the peak force was 2–2.75 times higher at high rate loading than quasistatic rates. Males had greater energy absorbed than females but not at all wrist positions. Damping characteristics were the highest in the group with the thickest soft tissue while damping characteristics were the lowest in group with the thinnest soft tissues.

Conclusion

Palmar tissue response changes with joint position, loading rate, sex, and tissue thickness. Accurately capturing these tissue responses is important for developing effective simulations of fall and injury biomechanics and assessing the effectiveness of injury prevention strategies.

Investigation of femur fracture potential in common pediatric falls using finite element analysis

A finite element (FE) model of an 11-month-old child's femur was developed to evaluate fracture risk in short-distance feet-first falls and bed falls. Pediatric material properties were applied to the FE model. Femur loading was derived from previously conducted fall experiments using a child surrogate where fall conditions (e.g., fall height, impact surface) were varied. Fracture thresholds based on principal stress and strain were used to examine potential for fracture. Peak stress/strain were significantly greater for feet-first falls from greater heights and onto harder impact surfaces. Feet-first falls exceeded some, but not all fracture thresholds. Bed falls did not exceed any fracture thresholds.

Effects of full body harness design on fall arrest performance

The use of personal protective equipment, including a safety harness, is one of the basic methods of protection against falls from a height. The presented studies, using an anthropomorphic dummy, identified the effect on the human body of the dangerous phenomena accompanying safety harness performance during fall arrest. The displacement of the dummy in the safety harness, the mutual displacement of the adjustment buckles and the webbing of the harness, the tightening of the straps on the dummy and the impacts exerted on the head of the dummy by the harness elements were considered. The correlation between the design of the safety harness and the parameters and phenomena in question has been demonstrated. It has been shown that for the purposes of assessment of novel harness designs it is necessary to carry out studies utilizing an anthropomorphic dummy in addition to resistance tests.

Playground equipment-related head injuries requiring hospitalization in children

BACKGROUND

The aim of this study was to investigate the circumstances of playground equipment-related head injuries in children and consider preventive measures based on the associated characteristics.

METHODS

The survey period was from February 1988 to January 2017. The study participants were children <15 years of age who had been hospitalized for playground equipment-related head injury. The following factors were investigated retrospectively: age; sex; fall height; material of the surface under the equipment; mechanism and diagnosis of the head injury; neurological signs at admission; and neurological outcome.

RESULTS

A total of 42 children (median age, 5 years; M/F: 26/16) were treated for head injuries, which involved a slide in 20 cases (47.6%), a swing in 11 (26.2%), a jungle gym in five (11.9%), monkey bars, iron bars, and a trampoline in one each, and unspecified equipment in six (14.3%). Falls ranged from a height of 1.2 to 2.5 m. Most of the falls occurred on hard soil or concrete. Head injuries depended on the age of the child, the injury mechanisms, and the characteristics of the equipment.

CONCLUSIONS

The playground equipment-related head injuries found in the present study involved not only skull fractures and concussions, but also intracranial hemorrhage and surgical cases. Children routinely use playground equipment, so effective strategies to reduce the occurrence of playground equipment-related head injuries need to be formulated.

Femur loading in feet-first fall experiments using an anthropomorphic test device

BACKGROUND

Femur fractures are a common orthopedic injury in young children. Falls account for a large portion of accidental femur fractures in young children, but there is also a high prevalence of femur fractures in child abuse, with falls often provided as false histories. Objective information regarding fracture potential in short distance fall scenarios may aid in assessing whether a child's injuries are the result of abuse or an accidental fall. Knowledge of femur loading is the first step towards understanding likelihood of fracture in a fall.

OBJECTIVE

Characterize femur loading during feet-first free falls using a surrogate representing a 12-month-old child.

METHODS

The femur and hip joint of a surrogate representing a 12-month-old were modified to improve biofidelity and measure femur loading; 6-axis load cells were integrated into the proximal and distal femur. Femur modification was based upon CT imaging of cadaveric femurs in children 10-14 months of age. Using the modified 12-month-old surrogate, feet-first free falls from 69 cm and 119 cm heights onto padded carpet and linoleum were conducted to assess fall dynamics and determine femur loading. Femur compression, bending moment, shear and torsional moment were measured for each fall.

RESULTS

Fall dynamics differed across fall heights, but did not substantially differ by impact surface type. Significant differences were found in all loading conditions across fall heights, while only compression and bending loads differed between carpet and linoleum surfaces. Maximum compression, bending, torsion and shear occurred in 119 cm falls and were 572 N, 23 N-m, 11 N-m and 281 N, respectively.

CONCLUSIONS

Fall dynamics play an important role in the biomechanical assessment of falls. Fall height was found to influence both fall dynamics and femur loading, while impact surface affected only compression and bending in feet-first falls; fall dynamics did not differ across carpet and linoleum. Improved pediatric thresholds are necessary to predict likelihood of fracture, but morphologically accurate representation of the lower extremity, along with accurate characterization of loading in falls are a crucial first step.

Reality and risk of contact-type head injuries related to bicycle-mounted child seats

OBJECTIVE

The authors have treated numerous children who have been injured by falling from bicycle-mounted child seats. Despite the greatly increased use of such seats, the understanding of their risk and the importance of helmet use remains alarmingly poor. The objective of this study was to confirm the risk of bicycle-mounted child seats and to evaluate the efficacy of helmets, seat belts, and back seat height in terms of preventing or mitigating contact-type head impacts that occur in falls from bicycle-mounted child seats.

MATERIALS AND METHODS

Biometrical dummy tests were performed to examine contact-type head injuries in falls from stationary bicycles. A bicycle with an anthropometric test dummy placed in a bicycle-mounted child seat was tipped over. Each test was repeated three times and three-dimensional acceleration was measured using accelerometer. Head Injury Criteria (HIC) were calculated and the respective influences of a helmet, a seat belt, and increased height of the back of the seat on such impacts were evaluated.

RESULTS

Only helmets unequivocally lowered maximal acceleration and/or HIC values with statistical significance. The seat belt lowered HIC values as long as it was used with the high-back seat. Only when the dummy wore a helmet sitting in a high-back seat did the HIC show less than the threshold of 570 for three-year-old children. The HIC showed the lowest score of 161.5 when the dummy wore both a helmet and a seat belt sitting in a high-back seat.

CONCLUSIONS

Riders in bicycle-mounted child seats definitely have higher risks of contact-type head injuries. In transporting a child on a bicycle-mounted child seat, parents must use both a child-bicycle helmet and a high-back child seat at least; a seat belt is highly recommended as long as it is used with the other safety devices.

IMPACT ON INDUSTRY

The bicycle-mounted child seat should have a high enough back and an appropriate seat belt to protect the head of the child from a contact-type injury.

Injury biomechanics and child abuse

Child abuse is a leading cause of morbidity and mortality in young children and infants in the United States. Medical care providers, social services, and legal systems make critical decisions regarding injury and history plausibility daily. Injury plausibility judgments rely on evidence-based medicine, individualized experiences, and empirical data. A poor outcome may result if abuse is missed or an innocent family is accused, therefore evidence and science-based injury assessments are required. Although research in biomechanics has improved clinical understanding of injuries in children, much work is still required to develop a more scientific, rigorous approach to assessing injury causation. This article reviews key issues in child abuse and how injury biomechanics research may help improve accuracy in differentiating abuse from accidental events. Case-based biomechanical investigations, human surrogate, and computer modeling biomechanics research applied to child abuse injury are discussed. The goal of this paper is to provide an overview of key research studies rather than on review or commentary articles. Limitations and future research needs are also reviewed.

Biomechanics of the toddler head during low-height falls: an anthropomorphic dummy analysis

OBJECT

Falls are the most common environmental setting for closed head injuries in children between 2 and 4 years of age. The authors previously found that toddlers had fewer skull fractures and scalp/facial soft-tissue injuries, and more frequent altered mental status than infants for the same low-height falls (<or=3 ft).

METHODS

To identify potential age-dependent mechanical load factors that may be responsible for these clinical findings, the authors created an instrumented dummy representing an 18-month-old child using published toddler anthropometry and mechanical properties of the skull and neck, and they measured peak angular acceleration during low-height falls (1, 2, and 3 ft) onto carpet pad and concrete. They compared these results from occiput-first impacts to previously obtained values measured in a 6-week-old infant dummy.

RESULTS

Peak angular acceleration of the toddler dummy head was largest in the sagittal and horizontal directions and increased significantly (around 2-fold) with fall height between 1 and 2 ft. Impacts onto concrete produced larger peak angular accelerations and smaller impact durations than those onto carpet pad. When compared with previously measured infant drops, toddler head accelerations were more than double those of the infant from the same height onto the same surface, likely contributing to the higher incidence of loss of consciousness reported in toddlers. Furthermore, the toddler impact forces were larger than those in the infant, but because of the thicker toddler skull, the risk of skull fracture from low-height falls is likely lower in toddlers compared with infants.

CONCLUSIONS

If similar fracture limits and brain tissue injury thresholds between infants and toddlers are assumed, it is expected that for impact events, the toddler is likely less vulnerable to skull fracture but more vulnerable to neurological impairment compared with the infant.