Ernest Deemer

Femur fractures resulting from stair falls among children: an injury plausibility model.

Background. Stair falls are common among young children and are also common false histories in cases of child abuse. When a child presents with a femur fracture and a stair-fall history, a judgment of plausibility must be made. A lack of objective injury and biomechanical data makes plausibility determination more difficult. Our objective was to characterize key features associated with femur fractures from reported stair falls, to develop a model for assessing injury plausibility (IP). Methods. Children 2 to 36 months of age who presented with a femur fracture from a reported stair fall were studied prospectively. Detailed history recording, examinations, fracture characterization, and injury scene analyses were conducted, and biomechanical measures associated with injury prediction were calculated. With our proposed IP model, all cases were then scored for the detail of history, biomechanical compatibility of fracture morphologic features, time to seeking care, and presence of other injuries. Results. Twenty-nine children were diagnosed with a femur fracture resulting from a reported stair fall. The IP model made a clear distinction between 2 groups, designated plausible and suspicious. Significant differences were observed for the detail of history, biomechanical compatibility of fracture, time to seeking care, presence of other injuries, and total IP scores. In the plausible group, the minimal linear momentum associated with a transverse fracture was almost 10-fold greater than that for spiral or buckle fracture types. Conclusions. This study adds new information to the current body of knowledge regarding injury biomechanics and fractures among children. The IP model provides an objective means of assessing plausibility of reported stair-fall–related femur fractures and identifies key characteristics to facilitate decision-making.

Influence of fall height and impact surface on biomechanics of feet-first free falls in children.

OBJECTIVE The objectives of our study were to assess biomechanics associated with feet-first free falls in 3-year-old children and to investigate the influence of impact surface type and fall height on key biomechanical measures associated with injury risk. METHODS Repeatable feet-first free fall experiments were conducted in a laboratory mock-up environment using an instrumented Hybrid II 3-year-old test dummy. Impact surface type and fall height were varied to examine their influence on biomechanical measures. RESULTS Feet-first falls from short distances (27 in.) (0.69 m) were found to have a low risk of contact-type head injury, regardless of impact surface type. When comparing different types of impact surfaces in a 27 in. (0.69 m) fall, head acceleration associated with falls onto playground foam was significantly less than that associated with falls onto wood, linoleum or padded carpet. For falls onto playground foam, femoral compressive loads and bending moments were found to significantly increase as fall height increased. CONCLUSIONS Impact surface type and fall height were found to influence biomechanics associated with injury risk in feet-first free falls as assessed through experimental mock-ups using an instrumented child test dummy. Feet-first falls from short distances (27 in.) (0.69 m) were associated with a low risk of contact-type head injury as assessed using HIC, irrespective of impact surface type.

Evaluation of wheelchair drop seat crashworthiness

Wheelchair seating crash performance is critical to protecting wheelchair users who remain seated in their wheelchairs during transportation. Relying upon computer simulation and sled testing seat loads associated with a 20 g/48 kph (20 g/30 mph) frontal impact and 50th percentile male occupant were estimated to develop test criteria. Using a static test setup we evaluated the performance of various types of commercially available drop seats against the loading test criteria. Five different types of drop seats (two specimens each) constructed of various materials (i.e. plastics, plywood, metal) were evaluated. Two types of drop seats (three of the total 10 specimens) met the 16650 N (3750 lb) frontal impact test criteria. While additional validation of the test protocol is necessary, this study suggests that some drop seat designs may be incapable of withstanding crash level loads.

Evaluation of wheelchair sling seat and sling back crashworthiness.

Many wheelchairs are used as vehicle seats by those who cannot transfer to a vehicle seat. Although ANSI/RESNA WC-19 has been recently adopted as a standard to evaluate crashworthiness of the wheelchairs used as motor vehicle seats, replacement or after-market seats may not be tested to this standard. This study evaluated the crashworthiness of two specimens each of three unique sling backs and three unique sling seats using a static test procedure intended to simulate crash loading conditions. To pass the test, a sling back is required to withstand a 2290 lb load, and a sling seat should be capable of withstanding a 3750 lb load. All, but two sling back specimens which failed at 1567 lb and 1787 lb, withstood the test criterion load. Two of six tested sling seats failed to pass the test: one failed at 3123 lb and the other failed to sustain the load for 5 s although it reached the test criterion load. Most of the failures occurred at the seams of the side openings of upholsteries where the wheelchair frame inserts for attachment.