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.
Irregular head movement patterns in whiplash patients during a trajectory task
From: Exp Brain Res. 2009 Oct 10
Chronic neck pain has been associated with disturbances in the sensorimotor control system in both non traumatic and whiplash related neck pain, such as postural stability disturbances, head and eye movement disturbances, erratic and irregular cervical motion patterns and stiffer, less flexible movement patterns. This points to centrally mediated somatosensory alterations with neck pain that may contribute to ongoing symptoms. Some motor impairments seem to particularly associate with a traumatic origin of the pain. Greater deficits in tests of head and eye movement control and decreased postural stability seem to distinguish whiplash associated disorder patients. Some of these deficits appear in association with the complaint of dizziness and neck pain intensity.
Patients with whiplash associated disorders have shown less accuracy in trajectory head motion compared to asymptomatic controls, which comply with clinical observations. The aim of this study was to investigate whether a trajectory head movement task can differ between whiplash associated disorders patients, chronic non traumatic neck pain patients and asymptomatic controls. Study groups included subjects with whiplash associated disorders (n = 35) with persistent neck pain after a car accident, chronic non traumatic neck pain (n = 45), and asymptomatic controls (n = 48). Head motion was recorded from an unsupported standing position using a 3D Fastrak device. A laser pointer was attached to the head and by moving the head the subjects were asked to trace a figure of eight displayed on the wall at three different paces (slow, moderate and fast). The motion signal was decomposed into 1 Hz frequency bands and angular velocity (deg/s) within each frequency band was calculated. Significantly higher angular RMS velocity was found in the whiplash associated disorders group compared to the two other groups for the slow paced test (3-4 and 4-5 Hz frequency bands) and the moderate paced test (3-4 Hz frequency band) indicating irregular and uncoordinated movements. Angular RMS velocity was associated with pain and dizziness, but only with severe symptom levels. In conclusion, irregular head movements during a complex task were found in the whiplash associated disorders group, indicating altered central sensorimotor processing. The irregularities were found within frequency levels observable to clinicians.
Biomechanics of whiplash injury
From: Chin J Traumatol. 2009 Oct;12(5):305-14
Despite a large number of rear-end collisions on the road and a high frequency of whiplash injuries reported, the mechanism of whiplash injuries is not completely understood. One of the reasons is that the injury is not necessarily accompanied by obvious tissue damage detectable by X-ray or MRI. An extensive series of biomechanics studies, including injury epidemiology, neck kinematics, facet capsule ligament mechanics, injury mechanisms and injury criteria, were undertaken to help elucidate these whiplash injury mechanisms and gain a better understanding of cervical facet pain. These studies provide the following evidences to help explain the mechanisms of the whiplash injury: (1) Whiplash injuries are generally considered to be a soft tissue injury of the neck with symptoms such as neck pain and stiffness, shoulder weakness, dizziness, headache and memory loss, etc. (2) Based on kinematical studies on the cadaver and volunteers, there are three distinct periods that have the potential to cause injury to the neck. In the first stage, flexural deformation of the neck is observed along with a loss of cervical lordosis; in the second stage, the cervical spine assumes an S-shaped curve as the lower vertebrae begin to extend and gradually cause the upper vertebrae to extend; during the final stage, the entire neck is extended due to the extension moments at both ends. (3) The in vivo environment afforded by rodent models of injury offers particular utility for linking mechanics, nociception and behavioral outcomes. Experimental findings have examined strains across the facet joint as a mechanism of whiplash injury, and suggested a capsular strain threshold or a vertebral distraction threshold for whiplash-related injury, potentially producing neck pain. (4) Injuries to the facet capsule region of the neck are a major source of post-crash pain. There are several hypotheses on how whiplash-associated injury may occur and three of these injuries are related to strains within the facet capsule connected with events early in the impact. (5) There are several possible injury criteria to correlate with the duration of symptoms during reconstructions of actual crashes. These results form the biomechanical basis for a hypothesis that the facet joint capsule is a source of neck pain and that the pain may arise from large strains in the joint capsule that will cause pain receptors to fire.
Functional cervical MRI within the scope of whiplash injuries: presentation of a new motion device for the cervical spine
From: Surg Radiol Anat. 2009 Sep 18
Frequently following a whiplash injury of the cervical spine, patients suffer from persistent pain symptoms. The MRI will in some of these cases show changes consistent with disc pathology or spinal stenosis, although in most instances the imaging studies will offer no adequate explanation for the described symptoms. The goal of our research was to develop and test a new MRI compatible device that will allow functional imaging of the cervical spine.
A total of 30 patients with whiplash injuries were evaluated during the first 6 weeks following trauma with the functional MRI. The examination was carried out with a T2-weighted turbo spin-echo sequence utilizing a new apparatus consisting of an inflatable air bag contained in a Plexiglas housing. Thanks to a valve placed outside of the examination room, it was possible to individually regulate the amount of air used to fill the pillow, thereby obtaining a full range of motion between flexion and extension.
In 25 cases no pathology was found during this examination. Two patients presented with scarring of the alar ligaments, indicative of a traumatic lesion. In two other instances the images in reclination revealed a bulging disc, while in one case a widening of the disc space was found as a sign for a rupture of the anterior longitudinal ligament.
This study was able to demonstrate the applicability of the new functional testing device, which permits a standardized, continuous and dynamic evaluation of the cervical spine in a closed MRI.
The clinical presentation of chronic whiplash and the relationship to findings of MRI fatty infiltrates in the cervical extensor musculature: a preliminary investigation
From: Eur Spine J. 2009 Aug 12. [Epub ahead of print]
The objective was to determine whether any measurable changes in sensory responses, kinesthetic sense, cervical motion, and psychological features were related to established fatty infiltration values in the cervical extensor musculature in subjects with persistent whiplash. It is unknown if fatty infiltrate is related to any signs or symptoms. Data on motor function, Quantitative Sensory Testing, psychological and general well-being, and pain and disability were collected from 79 female subjects with chronic whiplash. Total fat values were created for all subjects by averaging the muscle fat indices by muscle, level, and side from our MRI dataset of all the cervical extensor muscles.
Results of this study indicate the presence of altered physical, kinesthetic, sensory, and psychological features in this cohort of patients with chronic whiplash. Combined factors of sensory, physical, kinesthetic, and psychological features all contributed to a small extent in explaining the varying levels of fatty infiltrate, with cold pain thresholds having the most influence. Identifying and relating quantifiable muscular alterations to clinical measures in the chronic state, underpin some clinical hypotheses for possible pathophysiological processes in this group with a chronic and recalcitrant whiplash disorder. Future research investigations aimed at accurate identification, sub-classification, prediction, and management of patients with acute and chronic whiplash is warranted and underway.
The effect of two exercise regimes; motor control versus endurance and strength training for patients with whiplash associated disorders
From: Clin Rehabil. 2009 Aug 5. [Epub ahead of print]
The objective of this pilot study was to compare the effect of exercise regimes with focus on either motor control training or endurance and strength training for patients with whiplash associated disorders in the subacute phase. An outpatient spine clinic in Norway recruited twenty five subjects with a whiplash associated disorder still having symptoms or disability six weeks after injury.
The whiplash associated disorder participants received 6 to 10 sessions of physiotherapy for six weeks with focus on either motor control or endurance and strength of neck muscles. The primary outcome measure was the Neck Disability Index, while the secondary outcome measures were pain intensity, neck functioning and sick leave.
No statistical significant differences concerning primary and secondary outcome measures were demonstrated between the groups. Approximately half of the participants in both groups obtained clinically important improvement on perceived disability assessed by Neck Disability Index at six weeks and one year follow up. The changes within both groups were statistically significant at six weeks, but not at one year follow up. For most pain related variables clinical significant improvement was demonstrated in both groups at six weeks, but for fewer participants at one year. There was also statistical significant improvement within groups in some of the physical performance tests at one year follow up.
The changes associated with motor control training and endurance and strength training of neck muscles were similar for reduced disability, pain and for improving physical performance. With a low number of participants and no control group, however, the authors could not be sure whether the improvements are due to interventions or other reasons.
