Rear-impact neck protection devices for adult wheelchair users.

Many wheelchair users remain in their wheelchairs during transit. Safety research for wheelchair users has focused mainly on frontal impact. However, although they are generally less severe, rear-impact injuries are expensive and difficult to treat and whiplash injury protection for adult wheelchair users remains poorly understood. In this article, 10 g (16 km/h) rear-impact sled tests conducted with the Biofidelic Rear Impact Dummy II or BioRID-II (Denton ATD Inc and Chalmers University of Technology; Gothenburg, Sweden) seated in a rigid wheelchair with no head restraint showed that Abbreviated Injury Scale-score 1 neck injury risk evaluated with the neck injury criterion (NIC) and Nkm criterion is substantially above proposed threshold levels. A prototype wheelchair head restraint was developed and tested together with an existing commercial head restraint (Rolko; Borgholzhausen, Germany) in the same 10 g (16 km/h) rear impact. Both head restraints reduced the injury scores substantially. NIC test scores for the head restraints with no gap ranged from 18 to 24 (approximately 20%-30% chance of neck injury symptoms of duration >1 month) compared with test scores for no head restraints that ranged from 34 to 37 (approximately 95% chance of neck injury). The corresponding extension-posterior Nkm scores with no gap ranged from 0.30 to 0.35 (approximately 5% chance of neck injury) compared with no head restraint of 1.16 (approximately 45% chance of neck injury symptoms). However, the number of sled tests performed was small (three with no head restraint and six with a head restraint), and these results should be considered mainly trends. Preliminary results also showed that the horizontal gap between the head and the wheelchair head-restraint cushion should be as small possible.