Anthropomorphic simulations of falls, shakes, and inflicted impacts in infants

Abstract

Object. Rotational loading conditions have been shown to produce subdural hemorrhage and diffuse axonal injury. No experimental data are available with which to compare the rotational response of the head of an infant during accidental and inflicted head injuries. The authors sought to compare rotational deceleration sustained by the head among free falls, from different heights onto different surfaces, with those sustained during shaking and inflicted impact. Methods. An anthropomorphic surrogate of a 1.5-month-old human infant was constructed and used to simulate falls from 0.3 m (1 ft), 0.9 m (3 ft), and 1.5 m (5 ft), as well as vigorous shaking and inflicted head impact. During falls, the surrogate experienced occipital contact against a concrete surface, carpet pad, or foam mattress. For shakes, investigators repeatedly shook the surrogate in an anteroposterior plane; inflicted impact was defined as the terminal portion of a vigorous shake, in which the surrogate's occiput made contact with a rigid or padded surface. Rotational velocity was recorded directly and the maximum (peak—peak) change in angular velocity and the peak angular acceleration were calculated. Analysis of variance revealed significant increases in the and associated with falls onto harder surfaces and from higher heights. During inflicted impacts against rigid surfaces, the and were significantly greater than those measured under all other conditions. Conclusions. Vigorous shakes of this infant model produced rotational responses similar to those resulting from minor falls, but inflicted impacts produced responses that were significantly higher than even a 1.5-m fall onto concrete. Because larger accelerations are associated with an increasing likelihood of injury, the findings indicate that inflicted impacts against hard surfaces are more likely to be associated with inertial brain injuries than falls from a height less than 1.5 m or from shaking.

Potential for head injuries in infants from low-height falls

“…The present surrogate study is the first published 3D head angular acceleration and velocity, and contact force data experienced at head impact in falls of children. 6,7,19,29 As a first principle, larger impact forces have a higher likelihood of producing skull fracture, but tissue thresholds-the critical stresses above which fracture occurs-are the necessary link to associate the measured loads of the surrogate with injury. Thus, the following 2 tools are needed to predict fracture from the measured loads in this study: 1) one that relates fall impact forces to skull stresses (computational models), and 2) one that relates skull stresses to fracture (mechanical properties).…”

“…The 3D angular acceleration and velocity (that is, measurements of sagittal, coronal, and axial rotation of the head), and impact forces were measured to evaluate the biomechanics of head-first low-height falls of young infants. We hypothesized that the addition of sutures to the skull case and the incorporation of a 3D mobile neck would significantly decrease the peak head angular acceleration compared with the surrogate data of Prange et al 19 with a hinge neck. We also hypothesized that falls from higher heights onto harder surfaces would generate significantly more impact force than falls from lower heights onto softer surfaces.…”

“…Previously, we performed similar biomechanical studies with child surrogates to investigate biomechanics of head injury in infants. Specifically, Duhaime et al 7 and Prange et al 19 developed 4-and 6-week-old infant anthropomorphic surrogates, respectively, to compare the velocity and acceleration responses of shaking to intentional impact onto various surfaces. The surrogate used by Prange and colleagues was designed to measure the maximum rotational acceleration response of the head during these events.…”

The Shaken Baby Syndrome: An Odyssey -II Origins and Further Hypotheses-

“…1,9,25) It is now clear that if humans actually do manually shake infants, the forces required to produce acute subdural hematoma by this hypothetical mechanism cannot be generated without impact. In reviewing an extensive body of literature including published articles and clinical cases, it is noted that many of the infants supposedly shaken exhibit not acute, but chronic subdural hematomas, which themselves are known to expand and present by rebleeding without accompanying trauma.…”

Initial Neurologic Presentation in Young Children Sustaining Inflicted and Unintentional Fatal Head Injuries

“…Researchers have suggested that an infant's response to traumatic loading differs from that of an older child 6 and that the acceleration magnitude varies by the mechanism. 15,16 Little research has been conducted that correlates specific clinical presentations of young children with neuropathological findings and how that varies by age and injury mechanism. Future work should focus on making these linkages to determine if those fatal cases that present with a lucid interval demonstrate unique pathology from the overwhelming majority of children who are immediately obviously symptomatic.…”