Rear impact neck protection devices for adult wheelchair users
From: J Rehabil Res Dev. 2009;46(4):499-514
For conventional motor vehicle seats, a head restrainteffectively reduces whiplash injuries to the neck in rear impact collisions, because it substantially reduces relative motion between the occupant’s head and chest. For wheelchair occupants traveling in adapted vehicles, a risk of whiplash injuries also exists, either for forward facing wheelchairs in a rear impact collision or for rearward facing wheelchairs in a frontal collision. However, unlike for motor vehicle seats, the provision of wheelchair head restraints is unregulated and testing of wheelchair head restraints in the mid-1990s indicated that commercial products failed in static tests through plastic bending of the vertical adjuster or pullout forces on the attachment bracket. Recent sled testing of head restraints for child wheelchair users showed that their presence significantly reduced a head restraint head fracture, concussion, and serious neck injury risk for rear impacts. However, how these findingsapply to AIS1 neck injury risk for adults in lower velocity rear impact whiplash cases is unclear. To address this problem, the authors performed a series of nine adult wheelchair occupant rear impact sled tests, where the BioRID-II was seated in a surrogate wheelchair. Tests were performed with and without a head restraint, and a new prototype and anexisting commercial head restraint were used.
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, rear impact sled tests conducted with the Biofidelic Rear Impact Dummy II or BioRID-II 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 in the same 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.
