Repositioning forward-leaning booster-seated child occupants in frontal-oblique low-acceleration impacts

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. 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. 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 (<i>p</i> &lt; .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) (<i>p</i> &lt; .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 (<i>p</i> &lt; .005) regardless of initial posture. 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.