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A Test Bed to Examine Helmet Fit and Retention and Biomechanical Measures of Head and Neck Injury in Simulated Impact
Published on: September 21, 2017
Repositioning forward-leaning booster-seated child occupants in frontal-oblique low-acceleration impacts
Valentina Graci1,2, Madeline Griffith1, Thomas Seacrist1,3
1Center for Injury Research and Prevention, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
Objective:
Recently, pre-pretensioner equipped seatbelts (PPT) were found to be effective in repositioning forward-leaning adults. The aim of this study was to evaluate the influence of the PPT on booster-seated forward-leaning children during sled-simulated frontal oblique low-acceleration impacts.
Methods:
Eight child volunteers (mean: 6.6 ± 0.5 years, four males, four females; weight 24.2 ± 2.1 kg; seated height 64.4 ± 3.9 cm) were seated on a low-acceleration impact sled in a high-back belt-positioning booster seat (BPB) on a rear vehicle bench seat restrained with a three-point seatbelt with a PPT. Volunteers were exposed to a far-side impact 30° from frontal (peak acceleration 1 g, duration 265 ms). Four randomized testing conditions were examined and repeated twice: seatbelt conditions with PPT (85 N at 250 ms prior sled onset) and without PPT; and a standard and a forward-leaning posture. A 3D motion capture system captured participants' kinematics. Repeated measure three-way ANOVAs tested the effect of seatbelt condition, posture, and repetition on head and trunk peak forward displacement. All displacements were measured relative to the initial position.
Results:
The PPT reduced peak forward head displacements in both standard (PPT 103 ± 21 mm vs no-PPT 165 ± 19 mm) and forward-leaning (PPT 42 ± 37 mm vs no-PPT 138 ± 25 mm) postures (p < .001). In the forward-leaning posture with the PPT, the maximum trunk displacement was the initial position: the peak trunk displacement during the sled pulse was less forward than the initial trunk position. Overall, the peak forward trunk displacement was greater in the standard posture (50 ± 37 mm) than in the forward-leaning posture (29 ± 45 mm) (p < .001) and was greater without the PPT (79 ± 13 mm) than with the PPT (1 ± 18 mm). Reduced values with the PPT were also found in the lateral head and trunk displacements (p < .005) regardless of initial posture.
Conclusions:
The PPT reduced head and trunk displacements in forward-leaning postures and prevented the trunk from moving further forward from the initial forward-leaning position. A PPT, with a relatively low force of 85 N, has the potential to reduce out-of-position postures in booster-seated children in nonstandard seating positions.
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