Head Impact Biomechanics in Pediatric Patient Falls

Problem. Hospitalized patient falls, defined as any unplanned descent to the floor [or onto an object] with or without injury, are medical errors that have captured the attention of health care quality, regulatory, and third party payers. Despite hospital-wide fall prevention programs, patients continue to fall with some regularity from their beds, cribs, chairs, toilets, and examination tables. Quality Improvement staff use the national MERP index to assign the level of medical error and corresponding patient harm to each fall event. Two levels of error include: 1) the capacity to cause error; and, 2) an error occurred. Harm is defined as “impairment of the physical, emotional, or psychological function or structure of the body and/or pain resulting therefrom”, ranging from 1 (capacity to cause error, no harm) to 9 (error that contributed to or caused patient death). Falls that involve head to floor contact are of greatest concern because of the potential for concussion. Unless there is loss of consciousness or skull fracture, the majority of hospitalized children are not examined or followed after discharge for signs of traumatic brain injury after a fall in the hospital. A measure of harm more sensitive than MERP scores is the head injury criterion (HIC), a function of head acceleration rate and the duration of acceleration, is an estimate of the potential for concussion or traumatic brain injury from an impact.

Purpose. The primary aim of this study was to evaluate the head injury potential of pediatric patients who fell and made head to floor contact. The secondary aim was to compare hospital-assigned levels of harm to each fall event with calculated head injury potentials.

Methods. We used forensic accident reconstruction methodologies and Newton’s laws of motion (inertia, acceleration, action-reaction) to calculate the magnitude of forces applied to a child’s body from a fall, and to estimate the HIC15 potential for concussion. According to the Federal Motor Vehicle Safety Standards and Regulations, HIC15 threshold levels are: age 5 years to adults 700; ages >2 to 5 years 570; ages 1 to 2 years 390; and <1 year 225. Biomechanical analysis of pediatric patient falls was conducted for 49 hospitalized patients, ages 11 months to 17 years, who fell from a crib, bed, chair, table, or couch, and made head to floor contact. Data for analysis were obtained from event reports and medical records.

Results. The children fell onto commercial-grade vinyl-covered concrete floors from a height of 72 cm (couch, chair, bed) to 149 cm (crib) in 0.31 to 0.63 seconds, an average of only one half (0.52) of a second. The force with which the children’s heads contacted the floor ranged from 2 to 6.9 times their body mass in kg. The children’s HIC15 potentials ranged from 26.4 to 1302.1. Seven children (14.3%) had head injury potential scores greater than their threshold for age. The median hospital harm index score for these pediatric fall events was 4=“no harm based on monitoring or intervention” assigned to 36 children; 10 were rated 3=”no harm,” 2 were rated 5=“temporary harm. ” The only child that received follow-up care for real or potential head injuries had a skull fracture and was assigned a score of 8=”intervention necessary to save life.”  A Spearman correlation between HIC15 potentials and error/harm scores (r= -0.251, p=0.041) showed a significant negative relationship to HIC15 levels. Of the 7 children with HIC15 greater than threshold, one was assigned a MERP score of 5 (temporary harm), and the others received a score of 4 (no harm based on monitoring or intervention). None of these children received follow-up care for real or potential head injuries after discharge.

Conclusions

Parents or providers have less than one second to stop a child from falling from their beds, cribs, tables, chairs or couches. Hospital-assigned levels of harm do not adequately reflect the potential for head injury calculated from biomechanical principles. The children with head injury potential scores greater than their threshold for age should have received parent instructions about signs and symptoms of concussion and follow-up care. When fall prevention interventions are unsuccessful, hospitals must develop interventions to prevent or minimize fall-related injuries. Two components of HIC15 calculations are height of the fall and the surface coefficient of restitution, or “stiffness,” which reflects the amount of energy absorbed by the floor-person system. Height-adjustable hospital cribs would be a good investment to protect our most vulnerable infants and toddlers. Research shows that floor mats significantly attenuate head injury potential by absorbing some of the force of the fall. The authors are developing an algorithm for use in clinical settings to estimate head injury potential for early identification of concussion from pediatric patient falls.