European Spine Society —The AcroMed prize for spinal research 1997

A study was conducted to find out whether in a rear-impact motor vehicle accident, velocity changes in the impact vehicle of between 10 and 15 km/h can cause so-called whiplash injuries. An assessment of the actual injury mechanism of such whiplash injuries and comparison of vehicle rear-end collisions with amusement park bumper car collisions was also carried out. The study was based on experimental biochemical, kinematic, and clinical analysis with volunteers. In Europe between DM 10 and 20 billion each year is paid out by insurance companies alone for whiplash injuries, although various studies show that the biodynamic stresses arising in the case of slight to moderate vehicle damage may not be high enough to cause such injuries. Most of these experimental studies with cadavers, dummies, and some with volunteers were performed with velocity changes below 10 km/h. About 65% of the insurance claims, however, take place in cases with velocity changes of up to 15 km/h. Fourteen male volunteers (aged 28–47 years; average 33.2 years) and five female volunteers (aged 26–37 years; average 32.8 years) participated in 17 vehicle rear-end collisions and 3 bumper car collisions. All cars were fitted with normal European bumper systems. Before, 1 day after and 4–5 weeks after each vehicle crash test and in two of the three bumper car crash tests a clinical examination, a computerized motion analysis, and an MRI examination with Gd-DTPA of the cervical spine of the test persons were performed. During each crash test, in which the test persons were completely screened-off visually and acoustically, the muscle tension of various neck muscles was recorded by surface eletromyography (EMG). The kinematic responses of the test persons and the forces occurring were measured by accelerometers. The kinematic analyses were performed with movement markers and a screening frequency of 700 Hz. To record the acceleration effects of the target vehicle and the bullet vehicle, vehicle accident data recorders were installed in both. The contact phase of the vehicle structures and the kinematics of the test persons were also recorded using high-speed cameras. The results showed that the range of velocity change (vehicle collisions) was 8.7–14.2 km/h (average 11.4 km/h) and the range of mean acceleration of the target vehicle was 2.1–3.6 g (average 2.7 g). The range of velocity change (bumper car collisions) was 8.3–10.6 km/h (average 9.9 km/h) and the range of mean acceleration of the target bumper car was 1.8–2.6 g (average 2.2 g). No injury signs were found at the physical examinations, computerized motion analyses, or at the MRI examinations. Only one of the male volunteers suffered a reduction of rotation of the cervical spine to the left of 10° for 10 weeks. The kinematic analysis very clearly showed that the whiplash mechanism consists of translation/extension (high energy) of the cervical spine with consecutive flexion (low energy) of the cervical spine: hyperextension of the cervical spine during the vehicle crashes was not observed. All the tests showed that the EMG signal of the neck muscles starts before the head movement takes place. The stresses recorded in the vehicle collisions were in the same range as those recorded in the bumper car crashes. From the extent of the damage to the vehicles after a collision it is possible to determine the level of the velocity change. The study concluded that, the limit of harmlessness for stresses arising from rear-end impacts with regard to the velocity changes lies between 10 and 15 km/h. For everyday practice, photographs of the damage to cars involved in a rear-end impact are essential to determine this velocity change. The stress occurring in vehicle rear-end collisions can be compared to the stress in bumper car collisions.     

Are cervical multifidus muscles active during whiplash and startle? An initial experimental study

Background  

The cervical multifidus muscles insert onto the lower cervical facet capsular ligaments and the cervical facet joints are the source of pain in some chronic whiplash patients. Reflex activation of the multifidus muscle during a whiplash exposure could potentially contribute to injuring the facet capsular ligament. Our goal was to determine the onset latency and activation amplitude of the cervical multifidus muscles to a simulated rear-end collision and a loud acoustic stimuli.     

Beschleunigungsverletzung der Halswirbels?ule in Abh?ngigkeit vom Unfallmechanismus

Background

Depending on the type of collision, car occupants who are involved in traffic accidents are often exposed to the unexpected effects on the cervical spine of traumatic stimuli from different directions. In a rear-end collision or a frontal collision of the car it is most likely that there is an effect of linear acceleration and a lateral or side impact acceleration of axial rotation on the cervical spine. The neuro-otological manifestations of whiplash injuries that can occur in response to various trauma mechanisms have not yet been sufficiently investigated. Method: Data from 64 patients who suffered a whiplash injury were selected for analysis. In 32 patients the trauma mechanism was a sudden action on the cervical spine from a linear impulse caused by a head-on collision of cars or rear-end collision. In the other 32 patients the trauma mechanism was a sudden action of an axial neck rotation at a side impact collision or a cross collision. The study compared the results of neuro-otological findings between the two patient groups.

Results

A comparison of the neuro-otological examination data of 64 patients revealed that there were 32 patients who had a sudden injury mechanism of cervical axial rotation, the prevalence of central vestibular and sensory impairments, such as pathological central nystagmus disinhibition, pathological changes in the auditory brainstem evoked potentials (ABEP), the auditory evoked cortical potentials (ALEP) and visual evoked potentials (VEP). In the second group of patients where the injury mechanism consisted of an unexpected linear momentum, peripheral vestibular and sensory disorders were predominant.

Conclusion

The observed differences in neuro-otological manifestations of whiplash trauma, which occur depending on the trauma mechanism, can be used for differential diagnostic purposes. The whiplash injuries of the cervical spine induced by an axial rotation acceleration showed a prevalence of central vestibular and sensory disturbances, while the whiplash injuries of the cervical spine induced by a linear acceleration showed a prevalence of peripheral vestibular, sensory and vestibulospinal disorders. Our data thus show in the first group of patients a prevalence of retrocochlear, supratentorial and subcortical lesions of the auditory tract, and brain lesions of the optic tract in the occipital pole and in the visual cortex.     

Are early MRI findings correlated with long-lasting symptoms following whiplash injury? A prospective trial with 1-year follow-up

Neck pain is the cardinal symptom following whiplash injuries. The trauma mechanism could theoretically lead to both soft tissue and bone injury that could be visualised by means of MRI. From previous quite small trials it seems that MRI does not demonstrate significant tissue damage. Large prospectively followed cohorts are needed to identify possible clinically relevant MRI findings. The objective of this trial was to evaluate (1) the predictive value of cervical MRI after whiplash injuries and (2) the value of repeating MRI examinations after 3 months including sequences with flexion and extension of the cervical spine. Participants were included after rear-end or frontal car collisions. Patients with fractures or dislocations diagnosed by standard procedures at the emergency unit were not included. MRI scans of the cervical spine were performed at baseline and repeated after 3 months. Clinical follow-ups were performed after 3 and 12 months. Outcome parameters were neck pain, headache, neck disability and working ability. A total of 178 participants had a cervical MRI scan on average 13 days after the injury. Traumatic findings were observed in seven participants. Signs of disc degeneration were common and most frequent at the C5–6 and C6–7 levels. Findings were not associated with outcome after 3 or 12 months. The population had no considerable neck trouble prior to the whiplash injury and the non-traumatic findings represent findings to be expected in the background population. Trauma-related MRI findings are rare in a whiplash population screened for serious injuries in the emergency unit and not related to a specific symptomatology. Also, pre-existing degeneration is not associated with prognosis.     

Finite element simulation of lower limb injuries to the driver in minibus frontal collisions

Purpose: This study aims to explore the biomechanical mechanism of lower limb injuries to the driver by establishing a finite element (FE) simulation model of collisions. Methods: First a minibus FE model was integrated with a seat belt system. Then it was used to rebuild two collisions together with the total human model for safety (THUMS) provided by Toyota Motor Corporation: a rear-end collision between a minibus and a truck and a head-on collision of a minibus to a rigid wall. The impact velocities of both collisions were set at 56 km/h. The vehicle dynamic response, vehicle deceleration, and dashboard intrusion in the two collisions were compared. Results: In the minibus rear-end truck collision, the peak values of the von Mises equivalent stress at the tibia and the femur were 133 MPa and 126 MPa respectively; while in the minibus head-on rigid wall collision, the data were 139 MPa and 99 MPa. Compared with the minibus head-on rigid wall collision, the vehicle deceleration was smaller and the dashboard intrusion was larger in the minibus rear-end truck collision. Conclusion: The results illustrate that a longer dashboard incursion distance corresponds to a higher von Mises equivalent stress at the femur. The simulation results are consistent with the driver''s autopsy report on lower limbs injuries. These findings verify that FE simulation method is reliable and useful to analyze the mechanisms of lower limb injuries to the driver in minibus frontal collisions.     

Whiplash: fact or fiction?

Cervical sprain/strain or whiplash injuries are a common cause of acute and chronic musculoskeletal impairments and are ubiquitous after rear-end automobile collisions. The diagnosis is largely subjective and the ideal treatment controversial. Unfortunately, the majority of compensated litigation claims are associated with whiplash-type injuries secondary to motor vehicle accidents. Fortunately, many recent advances have led to better understanding of the collision and injury biomechanics and to development of a prognostic classification system, objective diagnostic tests, an array of treatment modalities, and, most important, safer automobiles. These advances will undoubtedly lead to decreased incidence, a more accurate diagnosis, and a tailored management regimen resulting in improved outcomes and ultimately fewer legal proceedings.     

Electrodermal response and outcome from severe brain injury

The relation of electrodermal response measures to outcome from early post-traumatic vegetative state (VS) was investigated in 15 brain-injured and five control subjects. Brain-injured subjects were in acute VS or persistent VS (PVS), or had recovered from acute VS (RVS). Significant group differences were found on all electrodermal response measures, primarily due to the greater amplitude, number and consistency of responses in control subjects. Group differences in electrodermal habituation and orientation to auditory tones reflected the absence of orientation in most RVS subjects and the absence of both habituation and orientation PVS subjects. The groups differed in their response to matching faces and names. All of the control subjects, two of five RVS subjects and none of five acute subjects produced significant responses. Surprisingly, two PVS subjects also produced significant responses. For acute subjects a positive outcome at 6 months post-trauma was associated with early electrodermal startle amplitude and baseline lability. These results indicate that electrodermal responsiveness is generally reduced following acute VS, even in subjects with a relatively good recovery. Greater electrodermal activity in early VS may be associated with better potential for recovery.     

Biomechanics of whiplash injury

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.     

Biomechanics of whiplash injury

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.     

Muscle response pattern to sudden trunk loading in healthy individuals and in patients with chronic low back pain

STUDY DESIGN: A quick-release method in four directions of isometric trunk exertions was used to study the muscle response patterns in 17 patients with chronic low back pain and 17 matched control subjects. OBJECTIVES: It was hypothesized that patients with low back pain would react to sudden load release with a delayed muscle response and would exhibit altered muscle recruitment patterns. SUMMARY OF BACKGROUND DATA: A delay in erector spinae reaction time after sudden loading has been observed in patients with low back pain. Muscle recruitment and timing pattern play an important role in maintaining lumbar spine stability. METHODS: Subjects were placed in a semiseated position in an apparatus that provided stable fixation of the pelvis. They exerted isometric contractions in trunk flexion, extension, and lateral bending. Each subject performed three trials at two constant force levels. The resisted force was suddenly released with an electromagnet and electromyogram signals from 12 trunk muscles were recorded. The time delay between the magnet release and the shut-off or switch-on of muscle activity (reaction time) was compared between two groups of subjects using two-factor analysis of variance. RESULTS: The number of reacting muscles and reaction times averaged over all trials and directions showed the following results: For healthy control subjects a shut-off of agonistic muscles (with a reaction time of 53 msec) occurred before the switch-on of antagonistic muscles (with a reaction time of 70 msec). Patients exhibited a pattern of co-contraction, with agonists remaining active (3.4 out of 6 muscles switched off) while antagonists switched on (5.3 out of 6 muscles). Patients also had longer muscle reaction times for muscles shutting off (70 msec) and switching on (83 msec) and furthermore, their individual muscle reaction times showed greater variability. CONCLUSIONS: Patients with low back pain, in contrast to healthy control subjects, demonstrated a significantly different muscle response pattern in response to sudden load release. These differences may either constitute a predisposing factor to low back injuries or a compensation mechanism to stabilize the lumbar spine.     

Neuromuscular control of the head in an isometric force reproduction task: comparison of whiplash subjects and healthy controls

BACKGROUND CONTEXT: A number of recent scientific publications suggest that patients suffering from whiplash-associated disorders (WADs) exhibit sensorimotor deficits in the control of head and neck movements. PURPOSE: The main objective of the present study was to evaluate if subjects with WADs can produce isometric neck extension and flexion forces with precision, variability, and a mode of control similar to the values of healthy subjects. STUDY DESIGN: A control group study with repeated measures. PATIENT SAMPLES: Neck force production parameters and neuromuscular control were measured in 17 whiplash and 14 control subjects. The experimental group included subjects who had a history of persistent neck pain or disability after a motor vehicle accident. OUTCOME MEASURES: Pain levels were assessed on a standard 100-mm visual analog pain scale at the beginning and end of the experiment. Each whiplash subject completed the neck disability index and the short-form 36 health survey (SF-36) questionnaire before the experiment. METHODS: All subjects were asked to exert flexion and extension forces against a fixed head harness. Kinetic variables included time to peak force, time to peak force variability, peak force variability, and absolute error in peak force. Surface electrodes were applied bilaterally over the sternocleidomastoideus and paraspinal muscles. Electromyography (EMG)-dependent variables included EMG burst duration and amplitude using numerical integrated techniques. RESULTS: The average time to peak force was significantly longer for whiplash subjects than for the healthy controls. A significant increase in peak force variability was also observed in the whiplash group, and no group differences were noted for absolute error. Heightened muscular activity was seen in both paraspinal muscles, even though it only reached statistical significance for the left paraspinal muscle. CONCLUSION: Our results show that the whiplash subjects involved in the study were able to produce isometric forces with spatial precision similar to healthy controls using a motor strategy in which the time to peak force is increased. This trade-off between spatial precision and time to peak force probably reflects an adaptation aimed at limiting pain and further injuries.     

Trapped in the neutral zone: another symptom of whiplash-associated disorder?

Instability of the cervical spine following whiplash trauma has been demonstrated in a number of studies. We hypothesized that, in patients with whiplash-associated disorder, rotation of the head would be accompanied by an earlier onset of neck muscle activity to compensate for intrinsic instability. The aim of the study was to examine the range of motion (RoM) of the cervical spine and the onset and activity of the sternocleidomastoid (SCM) muscles during axial rotation, in healthy control subjects and in patients with chronic whiplash-associated disorder. Forty-eight control subjects (42% male) and 46 patients (33% male) with chronic whiplash-associated disorder (symptoms lasting longer than 3 months) were examined. Cervical axial RoM differed significantly (P = 0.0001) between the groups, with the whiplash patients showing lower values (83 degrees +/- 30 degrees) than the healthy controls (137 degrees +/- 19 degrees). The whiplash patient group showed no evidence of the predicted earlier activation of SCM muscles. Many patients never reached the point in the RoM where SCM muscle activity rises steeply, as it does in the healthy controls (the 'elastic zone'), and their movements remained mostly within the region of low muscle activity (the 'neutral zone'). The whiplash patients appeared either unable or unwilling to drive the cervical spine into this region of high muscle activity, possibly because they were restricted by existing pain or fear of pain.     

A cross-cultural comparison between Canada and Germany of symptom expectation for whiplash injury

OBJECTIVE: Symptom expectation for whiplash injury has been shown to be low in countries with low rates of chronic whiplash when compared with countries like Canada, where chronic whiplash is common. The objective of the current study is to compare the frequency and nature of expected "whiplash" symptoms in Germany with that in Canada. METHODS: A symptom checklist was administered to two subject groups selected from local companies in Germany and Canada. Subjects were asked to imagine having suffered a neck sprain (whiplash injury) with no loss of consciousness in a motor vehicle collision and to check which, of a variety of symptoms, they would expect might arise from the injury. For symptoms they anticipated, they were asked to select the period of time they expected those symptoms to persist. RESULTS: In both groups, the pattern of acute symptoms anticipated closely resembled the symptoms of acute whiplash victims, but 50% of Canadians also anticipated symptoms to last months or years, whereas few German subjects selected any symptoms as likely to persist. CONCLUSIONS: In Germany, despite the documented occurrence of neck sprain symptoms in individuals following motor vehicle collisions, there is a very low rate of expectation of any sequelae from this injury. The current or previous aspects of society that underlie this remain uncertain. This lack of expectation of chronicity in Germany may, in part, determine the low prevalence of the chronic whiplash syndrome there. Further studies of symptom expectation as an etiologic factor in the chronic whiplash syndrome are needed.     

Headache, neck pain, and neck mobility after acute whiplash injury: a prospective study

STUDY DESIGN: A 6-month prospective study of neck mobility in patients with acute whiplash injury and a control group with acute ankle distortion was conducted. OBJECTIVES: To assess active neck mobility after acute whiplash and ankle distortion injuries, and to relate neck mobility to headache, neck pain, and speed of car at the time of collision. SUMMARY OF BACKGROUND DATA: A major problem after whiplash injury is restriction of neck mobility immediately subsequent to trauma. It is, however, unclear whether neck mobility changes after the acute injury are related to the associated headache and neck pain. METHODS: Cervical range of neck motion, neck pain, and headache were assessed after 1 week, then 1, 3, and 6 months after injury in 141 patients with acute whiplash injury, and in 40 patients with acute nonsport ankle distortion. RESULTS: Patients with whiplash injury had significantly reduced flexion, extension, lateral flexion, and rotation of the neck immediately after injury, as compared with patients with ankle distortion injury. Neck mobility, however, was similar in the two groups after 3 months. In patients with whiplash injury, neck pain and neck mobility were found to be related inversely to reported headache and neck mobility. Neck mobility was not significantly related to a difference in car speed at the time of collision. CONCLUSIONS: Neck mobility is reduced immediately after, but not 3 months after, a whiplash trauma. Headache and neck mobility are related inversely and neck pain and neck mobility are related inversely during the first 6 months after acute whiplash injury.     

Trauma or treatment? The role of intermittent traction in the treatment of cervical soft tissue injuries.

Neurophysiology does not provide a satisfactory theory which explains the phenomenon of muscular "spasm" which is said to be present in the neck following soft-tissue injury. Lacking knowledge as to whether long continued intermittent traction--ranging from 10 pounds to total body weight pull--is therapeutic or traumatic, such treatments nevertheless are prescribed in physiotherapy departments and at home for months. They are believed to be non-physiological and irrational and, in the author's opinon, represent the persistence of several medical myths associated with the "rear-end" collision. The question is moot whether the intractable complaints following such injuries are not caused, in large part, by the repeated traumas to muscles, disks, and joints produced by strong intermittent distraction. Experimental anatomical studies also argue against the hopes expressed in favor of such treatment, namely: to relieve spasm and/or traumatic fibro-myositis (?), to enlarge the neural foramina and relieve "radiculitis," and to hasten recovery by means of a conjectured internal massage.     

Cervical muscle dysfunction in the chronic whiplash associated disorder grade II (WAD-II)

STUDY DESIGN: In a cross-sectional study, surface electromyography measurements of the upper trapezius muscles were obtained during different functional tasks in patients with a chronic whiplash associated disorder Grade II and healthy control subjects. OBJECTIVES: To investigate whether muscle dysfunction of the upper trapezius muscles, as assessed by surface electromyography, can be used to distinguish patients with whiplash associated disorder Grade II from healthy control subjects. SUMMARY OF BACKGROUND INFORMATION: In the whiplash associated disorder, there is need to improve the diagnostic tools. Whiplash associated disorder Grade II is characterized by the presence of "musculoskeletal signs." Surface electromyography to assess these musculoskeletal signs objectively may be a useful tool. METHODS: Normalized smoothed rectified electromyography levels of the upper trapezius muscles of patients with whiplash associated disorder Grade II (n = 18) and healthy control subjects (n = 19) were compared during three static postures, during a unilateral dynamic manual exercise, and during relaxation after the manual exercise. Coefficients of variation were computed to identify the measurement condition that discriminated best between the two groups. RESULTS: The most pronounced differences between patients with whiplash associated disorder Grade II and healthy control subjects were found particularly in situations in which the biomechanical load was low. Patients showed higher coactivation levels during physical exercise and a decreased ability to relax muscles after physical exercise. CONCLUSIONS: Patients with whiplash associated disorder Grade II can be distinguished from healthy control subjects according to the presence of cervical muscle dysfunction, as assessed by surface electromyography of the upper trapezius muscles. Particularly the decreased ability to relax the trapezius muscles seems to be a promising feature to identify patients with whiplash associated disorder Grade II. Assessment of the muscle (dys)function by surface electromyography offers a refinement of the whiplash associated disorder classification and provides an indication to a suitable therapeutic approach.     

Electromyographic and kinematic exploration of whiplash-type rear impacts: effect of left offset impact.

BACKGROUND CONTEXT: Although there are some volunteer collision studies reporting the effects of rear impacts on head and neck kinematics, there are few studies detailing the cervical muscle electromyogram response. Moreover, the effect of a rear impact offset to the left on the resultant muscle responses is unknown. PURPOSE: The purpose of this study was to determine the response of the cervical muscles to increasing low-velocity rear impacts offset by 45 degrees to the subject's left, and to compare the quantitative effects of expected and unexpected impact. STUDY DESIGN/SETTING: Nine healthy volunteers were subjected to rear impacts, offset by 45 degrees to the subject's left, of 4.6, 8.7, 11.0 and 14.5 m/s2 acceleration, at two levels of expectation: expected and unexpected. METHODS: Bilateral electromyograms of the sternocleidomastoids, trapezii and splenii capitis were recorded. Triaxial accelerometers recorded the acceleration of the chair, torso at the shoulder level and head of the participant. RESULTS: At an acceleration of 14.5 m/s2, the left sternocleidomastoid generated 71% and the right sternocleidomastoid 82% of their maximal voluntary contraction electromyogram in the unexpected impact conditions. Under these conditions, the right splenius capitis (contralateral to the left offset rear impact) also generated 71% of its maximal voluntary contraction, whereas the left splenius capitis generated only 20% of this variable. The trapezii generated only 25% of their maximal voluntary contraction. Subjects exhibited lower levels of their maximal voluntary contraction electromyogram when the impact was expected. Electromyographic variables were significantly affected by the levels of acceleration and expectation (p<.001). The time to onset and time to peak electromyogram for all muscles progressively decreased with increasing levels of acceleration, in the unexpected condition. The kinetic variables and the electromyographic variables regressed significantly on the acceleration (p<.001). In response to rear impacts offset to the subject's left, muscle responses were greater with higher levels of acceleration, greater with unexpected impact conditions and greatest for both sternocleidomastoids and for the splenius capitis muscle contralateral to the side of impact. CONCLUSIONS: Because the muscular component of the head-neck complex plays a role in the abatement of impact at higher acceleration levels, they are likely a primary site of injury in the whiplash phenomenon in rear collisions. More specifically, when a rear impact is offset to the subject's left, it results in not only increased electromyographic generation in both sternocleidomastoids, but the splenius capitis contralateral to the direction of impact offset also bears part of the force of the neck perturbation. Expecting or being aware of imminent impact also plays a role in reducing muscle responses in low-velocity offset rear impacts.     

Muscle activity during low-speed rear impact

PurposeWhiplash associated disorders remain a major health problem in terms of impact on health care and on societal costs. Aetiology remains controversial including the old supposition that the cervical muscles do not play a significant role. This study examined the muscle activity from relevant muscles during rear-end impacts in an effort to gauge their influence on the aetiology of whiplash associated disorders.MethodsVolunteers were subjected to a sub-injury level of rear impact. Surface electromyography (EMG) was used to record cervical muscle activity before, during and after impact. Muscle response time and EMG signal amplitude were analysed. Head, pelvis, and T1 acceleration data were recorded.ResultsThe activities of the cervical muscles were found to be significant. The sternocleidomastoideus, trapezius and erector spinae were activated on average 59 ms, 73 ms and 84 ms after the impact stimulus, respectively, prior to peak head acceleration (113 ms).ConclusionThe cervical muscles reacted prior to peak head acceleration, thus in time to influence whiplash biomechanics and possibly injury mechanisms. It is recommended therefore, that muscular influences be incorporated into the development of the new rear-impact crash test dummy in order to make the dummy as biofidelic as possible.     

Fiber composition and fiber transformations in neck muscles of patients with dysfunction of the cervical spine

Biopsies of ventral neck muscles (sternocleidomastoid, omohyoid, and longus colli) and dorsal neck muscles (rectus capitis posterior major, obliquus capitis inferior, splenius capitis, and trapezius) were taken from 64 patients who underwent spondylodesis for cervical dysfunction of different etiologies. The muscle fibers were classified histochemically as type I, IIA, IIB, or IIC (transitional or intermediate fibers) according to the pH lability of their myofibrillar ATPase. Signs of muscle fiber transformations were observed in all muscles investigated, as evidenced by an increased relative amount of type-IIC fibers. The transformations occurred independently of (a) the type of muscle (i.e., more “postural” or more “phasic”), (b) the sex and age of the patient, (c) the type of condition, and (d) the presence of additional neurological deficits. Thus, the same pattern of muscular reaction was found in patients with rheumatoid arthritis as in patients with soft-tissue injuries of the neck (e.g., “whiplash injury”). In the ventral muscles and the obliquus capitis inferior, the occurrence of transformations correlated strongly with the duration of symptoms; in the ventral muscles the vast majority of transformations were encountered in patients with a shorter history of symptoms, whereas in the obliquus capitis inferior the reverse occurred. In the other dorsal muscles, no correlation with the duration of symptoms was found. Muscles in which transformations had ceased displayed, on average, a significantly higher percentage of fast type-IIB fibers than were found in muscles with ongoing transformations. This strongly indicates that the transformations proceeded in the direction from “slow oxidative” to “fast glycolytic”.     

An unusual presentation of whiplash injury: long thoracic and spinal accessory nerve injury

Whiplash injuries from motor vehicle accidents are very common. The usual presentation and course of this condition normally results in resolution of symptoms within a few weeks. Brachial plexus traction injuries without any bone or joint lesion of the cervical spine have been reported before. We report a case where a gentleman was involved in a rear end vehicle collision, sustained a whiplash injury and was later found to have a long thoracic nerve palsy and spinal accessory nerve palsy. Although isolated injuries of both nerves following a whiplash injury have been reported, combined injury of the two nerves following a whiplash injury is very uncommon and is being reported for the first time.