GUIDELINES AVAILABLE FOR WHIPLASH

How guidelines are used Guidelines are frequently misused and commonly misunderstood or misinterpreted. These problems arise largely out of the failure of involved parties to thoroughly read and digest the guidelines. Practitioners often fear that their decision-making power and autonomy will be subverted, potentially compromising the health care they deliver and potentially imposing liability risks to them, as well as financial hardships. Insurers fear that some practitioners will leverage guidelines to justify questionably necessary practices, procedures, or medical services to their advantage. For the most part, both of these fears are unjustified if the guidelines are used correctly. For example, virtually all health care professions have always subscribed to a universal practice guideline which is traceable to Hippocrates. It contains several assumptions: in the case of whiplash injury, that 1) the patient has indeed sustained an injury that requires treatment, 2) when the patient reaches a preinjury status, that treatment should be withdrawn, 3) if the treatment is not shown to be effective, further diagnostic tests should be performed, an alternate form of therapy should be instituted, or the patient should be referred to another health care provider who can provide definitive treatment, and that 4) treatment can be justified only as long as it can be clearly documented by the practitioner that it substantially relieves the patient's pain or dysfunction, and/or allows the patient to remain within the workforce or engage in their usual activities.
None of the guidelines mentioned below (ACOEM, Croft, Reed, etc.) actually supercedes these fundamental and universal guiding principles. What they attempt to do is add a layer of precision by making more specific allowances based on best-evidence synthesis of current scientific literature concerning specific diseases or conditions. Used appropriately and conscientiously, for example, the Croft guidelines allow practitioners to provide necessary care to their whiplash patients, while also allowing insurers a greater ability to forecast likely outcomes and durations of care, while at the same time providing them with a means of monitoring for excessive, ineffective, or unnecessary care. This helps insurers reduce the appearance of arbitrary and often uninformed decision-making by IME doctors or file reviewers which is generally viewed skeptically by practitioners as being biased, arbitrary, or doctrinaire. Following is a discussion of some of the guidelines currently applied to the management of whiplash

ACOEM Guidelines With regard to whiplash, the Occupational Medicine Practice Guidelines (2nd edition), of the American College of Occupational and Environmental Medicine (ACOEM), mention the condition only to convey the advice made by the Quebec Task Force in 1995, which was for patients to remain active as opposed to having prolonged rest or immobilization. These guidelines are aimed primarily at workers compensation claims, but do provide general algorithms of management which chiefly follow a medical paradigm. And, although the authors do provide statistical data on disability periods, they do not make specific recommendations regarding treatment or treatment durations. Some diagnostic and treatment approaches are not recommended on the basis of evidence-based medicine. Spinal manipulation is among the treatment methods acknowledged as effective for both neck, upper back and lower back pain.

Acute Low Back Problems in Adults, Clinical Practice Guideline Number 14, U.S. Department of Heath and Human Services Public Health Service. These guidelines, which are occasionally and somewhat erroneously referred to as the "federal guidelines," were promulgated by the Agency for Health Care Policy and Research (AHCPR) in 1994. The authors point out that they do not consider children or adults with chronic low back pain. Needless to say, they are also not intended to be used as guidelines for the treatment of whiplash injuries.
Croft Guidelines The Croft Guidelines are based on an in-depth analysis of nearly 2000 actual cases managed by chiropractic physicians and reflect a broad range of clinical features, risk factors, complications, and practice styles. They were part of a joint project undertaken by the Spine Research Institute of San Diego in early 1990 to provide a lingua franca to this often confusing condition of whiplash injury. In the first stage of this research, a grading system was developed from a synthesis of all available outcomes literature. The resulting whiplash grading system was first published in 1993 (Croft AC: Treatment paradigm for cervical acceleration/deceleration injuries (whiplash). Journal of the American Chiropractic Association 30(1):41-45, 1993). This classification system contained not only a classification based on the grades of severity of the injuries, but also one that considered the type of collision (because the rear impact variety, for example, is known to have a less favorable outcome than other types) and the stage of recovery.

The Croft CAD Classification System (1992) Type of Collision   I Primary rear impact II Primary side impact III Primary frontal impact Grades of Severity Clinical Presentation I Minimal: no limitation of motion; no ligamentous injury or neurological findings II Slight: limitation of motion; no ligamentous or neurological findings * III Moderate: limitation of motion; some ligamentous injury; neurological findings may be present IV Moderate to severe: limitation of motion; ligamentous instability; neurological findings present; fracture or disc derangement ** V Severe: requires surgical management Stages of Recovery   I Acute: inflammatory stage (up to 72 hours) II Subacute: repair stage (72 hours to 14 weeks) III Remodeling stage (14 weeks to 12 months or more) IV Chronic: permanent * Neurological signs can include subjective complaints (numbness, tingling, etc.) . ** Fracture can include minimal end-plate fracture; disc derangement can include non-herniated forms. ***Duration of stages is dependent upon severity of injury and other factors.

Note that two years afterward, the Quebec Task Force on Whiplash Associated Disorders (QTF-WAD) published the results of their literature-wide analysis and, contained in the final document was a nearly identical grading system which has subsequently become known as the QTF grading system. This latter system has been widely adopted internationally and thus, a lingua franca now exists in the whiplash lexicon.

The Quebec Task Force Grading System (1995) Grades of Severity Clinical Presentation 0 No neck complaints; no physical sign(s) I Neck pain, stiffness, or tenderness only; no physical signs II Neck complaint AND musculoskeletal sign(s) * III Neck complaint AND neurological sign(s) ** IV Neck complaint AND fracture or dislocation * Musculoskeletal signs include decreased ROM and point tenderness. **Neurologic signs include decreased or absent deep tendon reflexes, weakness, and sensory deficits.

Because the QTF-WAD guidelines do not comment on chiropractic care, other than during the initial stages of recovery, and because it concerns only cases involving prolonged (i.e., greater than three weeks) loss of work status, the Croft guidelines provide chiropractic practitioners and insurers with the first and only profession-specific guideline.
Following a thorough history and physical examination, the practitioner classifies the patient into the most appropriate grade. The guideline then follows that grading scheme. It is anticipated that barring complicating factors or untoward circumstances, active treatment should not be needed beyond the maxima listed in table below.

Frequency and Duration of Care in CAD trauma
Grade	Daily	3x/wk	2x/wk	1x/wk	1x/mos	TD	TN
I	1 wk	1-2 wk	2-3 wk	<4 wk	-*	<10 wk	<21
II	1 wk	<4 wk	<4 wk	<4 wk	<4 mo	<29 wk	<33
III	1-2 wk	<10 wk	<10 wk	<10 wk	<6 mo	< 56 wk	<76
IV	2-3 wk	<16 wk	<12 wk	<20 wk	**	**	**
V	Surgical stabilization necessary: chiropractic care is post-surgical.
TD= treatment duration * possible follow-up at one month TN= treatment number ** may require permanent monthly or prn care

The reasoning behind daily treatment for the first week is four fold: 1) this is the time when practitioners can have the greatest impact on inflammation, 2) there is much to communicate to patients during this period (e.g., information about activities of daily living), 3) it is important to monitor the development of brain, brain stem, spinal cord, or nerve root lesions; it also allows practitioners to monitor the patient's home use of ice and cervical collar, and 4) because of the phenomenon of neuronal plasticity (814), the practitioner must make every effort to minimize the patient's pain as quickly as possible.
The practitioner can make the greatest impact on outcome during the first few weeks or care. This is one way also of keeping patients on the job. SRISD research demonstrated that whiplash patients treated by chiropractic practitioners only occasionally required more than two days time loss from their usual activities, and many had no time loss. In contrast, The Medical Disability Adviser: Workplace Guidelines for Disability Duration, 4th Edition, reported a median time loss of 37 days from their data source of 16,383 cases. (Note that not all of these cases involved whiplash-type neck injury, although it was described as the exemplar form of cervical strain/sprain injury.)
It is the opinion of Dr. A.C. Croft that the most effective treatment of whiplash requires a comprehensive initial management which includes physician-assisted therapy, physiotherapeutic modalities, appropriate analgesics and/or antiinflammatory agents, nutraceuticals, recommendations about activities of daily living and work and home ergonomics, exercise, and home care. This comprehensive management can help to reduce the current out of control public health burden imposed by whiplash trauma in which as many as 1 million chronic neck pain suffers are added to the growing pool of chronic pain sufferers each year in America, while some 300,000 become disabled. Much of this tragedy can be reduced by a more aggressive management program. Unfortunately, many whiplash victims are not offered much in the way of treatment and are told simply to learn to live with the pain.
Physicians, based on new information, laboratory or imaging data, or the clinical evolution of the particular case, may need to upgrade or downgrade the injury grade as time goes by. No individual case can be evaluated purely on the basis of normative or statistical data, and the practitioner must always base his or her decisions about treatment on the more fundamentally and widely accepted general guidelines adhered to by all practitioners and those promoted by the other practice guidelines mentioned here (e.g., Mercy, Reed, ACOEM, etc.): 1) when a patient reaches a preinjury condition, treatment should be concluded; likewise, 2) treatment can be justified in excess of established guidelines if it can be clearly documented that it substantially reduces the patient's pain or dysfunction, allows the patient to remain in the workforce or engage in their usual activities. Documentation of the need for care and its efficacy is a necessary component of modern practice for all health care practitioners.
Guidelines for Chiropractic Quality Assurance and Practice Parameters (Proceedings of the Mercy Center Consensus Conference) The Mercy guidelines, as they are most often referred to, provide general guidelines to chiropractic practitioners across a broad range of clinical subjects. However, there is no specific provision for the treatment of whiplash injuries in this document.
Following are a number of quotes which express the general spirit and intention of these guidelines. "These guidelines, which may need to be modified, are intended to be flexible. They are not standards of care. Adherence to them is voluntary. The Commission understands that alternative practices are possible and may be preferable under certain clinical conditions. The ultimate judgment regarding the propriety of any specific procedure must be made by the practitioner in light of the individual circumstances presented by each patient . . . This document may provide some assistance to third-party payers in the evaluation of care, but it is not itself a proper basis for evaluation. Many factors must be considered in determining clinical or medical necessity. Further, guidelines require constant re-evaluation as additional scientific and clinical information becomes available."

In chapter 8, "Frequency and Duration of Care," the area of these guidelines providing the basis for some contention among practitioners, it reads (page 117): "Guidelines concerning the treatment plan should be tempered with a balance of scientific information and systematic observation derived from clinical experience. Further, in order to be practical, they must be periodically upgraded to reflect advances in the ever-changing knowledge database. Their purpose is to assist the clinician in decision-making based on the expectation of outcome for the uncomplicated case. They are NOT [their emphasis] designed as a prescriptive or cookbook procedure for determining the absolute frequency and duration of treatment/care for any specific case. " They go on to note that: "No attempt has been made to select for individual conditions by region of complaint or by diagnosis . . . The majority of quantitative information available addresses the management of low back and leg pain complaints . . . The references to low-back disorders in this section are used only as examples. There is no intent to imply that these conditions constitute the totality of chiropractic expertise or practice. Rather, since these recommendations were born from experience and from data on multivariate clinical circumstances, they may be extrapolated with appropriate case-specific modifications to most of the common complaints for which chiropractic care is sought."

On the same page, the authors go on to state: "The approach to the development of guidelines for chiropractic quality assurance and standards of practice pertaining to the frequency and duration of treatment focuses on the uncomplicated case and logically includes the following considerations: 1) the natural history of common spinal disorders; 2) the characteristics and stages of tissue repair processes; and 3) reasonable treatment/care outcome classified into short- and long-range goals." On this page, and under the heading "Principles of Case Management," the authors note: "The primary missions of health care delivery are to provide sufficient care to restore health, maintain it, and prevent the recurrence of injury or illness . . . guidelines framing expectations of treatment outcome can be drawn from the literature and adapted by practical experience on a case-by-case basis."
Procedural/Utilization Facts: Chiropractic/Physical Therapy Treatment Standards-A Reference Guide, 5th edition. Also known commonly as the Olsen Guidelines, this 159-page document, authored by Richard E. Olson, DC, published by Data Management Ventures, Inc. Dr. Olson is also the author of Fee Facts, Prevailing Fees For Rehabilitative Medicine, A Reference Guide, and author of the Chiropractic Services Program, Managed Care Treatment Plans, A Reference Guide. The Olson Guidelines mention "whiplash" three times: twice in reference to PT modalities, and once in a somewhat vague reference to manipulation. In no case does he discuss treatment frequency or duration in reference to whiplash injuries.
QTF Guidelines In 1995 the Quebec Task Force on Whiplash-Associated Disorders published the results of their best-evidence synthesis (Spitzer WO, Skovron ML, Salmi LR, Cassidy JD, Duranceau J, Suissa S, Zeiss E: Scientific monograph of the Quebec task force on whiplash-associated disorders: redefining "whiplash" and its management. Spine (Supplement) 20(8S):1S-73S, 1995). The study has been widely acknowledged in the international scientific community, but it has also received widespread criticism for violating the very promise of best-evidence synthesis because the authors ultimately resorted to consensus-based-rather than evidence-based--methods (Freeman MD, Croft AC, Rossignol AM: "Whiplash associated disorders: redefining whiplash and its management" by the Quebec Task Force: a critical evaluation. Spine 23(9):1043-1049, 1998).
A number of other flaws were uncovered which limits the interpretations allowed by the study in terms of outcome. For example, their cohort of whiplash subjects was biased by selecting only persons with an 847.0 ICD-9-CM code and only those with a police report. Both can potentially select for a more favorable outcome: police reporting only cases in which the property damage exceeds $500 CAN selects for a longer duration (lower acceleration) crash within the narrow spectrum of low speed collisions, and persons with additional diagnostic codes are likely to have suffered more serious injuries.
More egregiously, the authors used return to usual activities (e.g., work) as a proxy for "recovery" when, in fact, they did not know whether these patients were still being treated or whether they were suffering from any lingering symptoms. When only 3% had failed to "recover" after one year, it really meant only that 3% had not returned to work or school. Nevertheless, this provided the source of great confusion regarding the typical outcome from whiplash injury. The authors developed a guideline for whiplash management based largely on a combination of a small number of papers and a consensus of their opinions. Spinal manipulation was considered one appropriate means of treatment. If a patient remains out of work for more than three weeks, specialist advice should be sought. If out of work for six weeks, a multidisciplinary team evaluation is recommended. For persons not out of work, however, these guidelines do not apply.
Reed Group, Ltd. The Medical Disability Adviser: Workplace Guidelines for Disability Duration, 4th edition is edited by Presely Reed, MD. In total, there are 2685 pages of text covering everything from abdominal aneurism to herpes zoster. In the preface he writes, "The Medical Disability Advisor is intended to be used as a tool against which the user should weigh the totality of his or her available knowledge and the specific information [of the individual case]. [And] Please use this tool judiciously, tempering your decisions with thoughtfulness and compassion." Throughout the book, the format follows a standard pattern: a description of the condition, diagnostics, treatment, prognosis, differential diagnosis, specialists, rehabilitation, work restriction/accommodations, comorbid conditions, complications, factors influencing duration, length of disability, duration of disability trends taken from normative data, and failure to recover. It contains two sections which reference whiplash. The first appears on page 1448 and is entitled "neck pain." It is noted that neck pain becomes chronic when it has lasted more than 6 months and the authors give, as an example of chronic neck pain, the cervical zygapophyseal pain associated with late whiplash. Using this condition as an exemplar is appropriate since our own research shows that whiplash may very well be the single largest cause of chronic neck pain.
Diagnostic modalities which might be utilized include radiographs, MRI, CT, EMG, nerve conduction, and laboratory studies. Treatment included pain medication, a short period of cervical collar, manipulation, and use of a pain management clinic. Specialists include chiropractors, a number of other medical specialists, and physical therapists. It is noted that chiropractic may be effective, particularly in the first 4-6 weeks. [This treatment is not excluded beyond 6 weeks.] For rehabilitation, the authors mentioned heat and cold modalities, electrostimulation, home traction, and isometric strength conditioning. The mean disability is reported to be 41 days, and in this context relates to either total or partial disability in the workplace. The duration is expected to be longer for persons with more active job descriptions than for those with sedentary jobs. These values do not represent durations of symptoms, nor should they be used to gauge treatment needs. The guidelines do not specify recommended treatment durations for any forms of health care, nor do they discuss standard practices. Under failure to recover, the authors ask a number of questions designed to guide practitioners toward conditions and/or potential therapies that might have been overlooked. For example, they ask, "Did the individual use a home traction unit, and, if so, did it help?"
The other section relevant to whiplash is found beginning on page 1981, under the title, "sprains and strains, cervical spine (neck)." This section covers, among other things, the specific condition resulting from being struck from the rear in a motor vehicle. The authors describe the plethora of symptoms that can result from these neck injuries and brain injuries, using radiography, CT, and MRI. Treatment includes a soft cervical collar, traction (in the case of radiculopathy or, as noted above, after the condition matures), and, in severe cases, facet rhizotomy. Under the heading "Prognosis," in the whiplash section, the authors make some interesting, if ambiguous, comments. They first note that, while healing is expected in a few weeks, in 20-70% of cases, patients remain symptomatic after 6 months. They note, however, that most of these patients eventually recover. Yet, in the very next paragraph, they acknowledge the fact that as many as a third will be symptomatic even 10 years after the injury. They also acknowledge a variety of risk factors which might make the outcome less favorable, such as female sex, increasing age, reduced range of motion, multiple symptoms, neurological deficit, or headaches. These would presumably be some of the factors which would require thoughtfulness and compassion in tempering decisions concerning management. In this section, no specific comments are made regarding the duration of chiropractic care. Generally, this section is quite consistent with the recommendations given in the textbook, Foreman SM, Croft AC (eds): Whiplash Injuries: the Cervical Acceleration/Deceleration Syndrome, 3rd edition, Lippincott Williams & Wilkins, Baltimore, 2001.
Whiplash: A Practitioner's Guide to Understanding Whiplash Associated Disorders (WAD) This was the result of a collaborative effort of numerous authorities at the behest of the Canadian Chiropractic Association. The 210-page guide was published in 2000 and distributed to all Canadian chiropractors by the CCA. The guide explores the topics of WAD physiology, symptomatology, grading issues, management, legal and road safety issues, third party payers, and the practitioner's role in reporting and note-taking. In chapter 4.2, "Standardized WAD Grading Systems," the Croft treatment guidelines are introduced.

HOW INJURIES ARE EVALUATED

Most often, following a physical examination, the initial method of assessment in the typical whiplash injury is radiography-standard x-rays. It is the only imaging procedure that would be considered routine. If the patient is to be treated medically only (i.e., with medication as opposed to spinal manipulation or surgery) and the injury appears quite minor, x-rays might not be indicated. If the patient has limited range of motion in the neck at the time of the examination, x-rays should be limited to the standard five-view series. Otherwise-once serious pathology (fracture, dislocation, etc.) have been ruled out-bending views in full flexion and extension should be obtained to assess ligamentous integrity.
When further questions arise concerning the biomechanical function and ligamentous integrity of the neck, videofluoroscopy can often provide important diagnostic information. MRI can also provide information about ligaments, but is more often used in the evaluation of the intervertebral discs. As is the case with plain x-rays, CT-and even MRI-will not have the sufficient resolving power to find many soft tissue injuries. In searching for suspected fractures, clinicians may turn to CT, bone scanning (scintigraphy) or single photon emission computed tomography (SPECT

WHIPLASH

Mathematical studies Over the years a number of mathematical models have been developed to help us better understand some of the features of whiplash injury. These studies continue today. A finite element model (FEM) of the human neck (with geometry modeled from the MRI scan of a 50th percentile male spine) has been validated against cadaver tests of 15 mph rear impact crashes from Duke University. Both solid (bone) and soft elements (nucleus and anulus using linear viscoelastic material properties) were modeled based on existing literature. Collision with a pre-deployed airbag was also modeled. The model correlated well with the experimental data in the rear impact crashes and clearly demonstrated the head lag (retraction) seen in human volunteer crash tests. The model also correlated well with airbag tests. During the rear impact tests (with FEM simulations), upward motion of T1 was noted with compression of the spine. This is due either to the ramping up of the torso or straightening of the thoracic spine. Compression led to loosening of the ligaments of the neck at about 40 msec after impact. During compression, the neck becomes less stiff, diminishing its resistance to shear forces. Up to 27% capsular stretch was observed. With FEA, the more complex we make our models, the more processing time is required to solve the simulations. In one of the most sophisticated FEA head/neck models of today, an IBM supercomputer, with five processors, requires 60 hours to process only 50 msec of data.
A multibody model developed at TNO Netherlands is the Mathematical Dynamic Model (MADYMO). Research on MADYMO is ongoing, although there do not appear to be any strong human subject validations for rear impact simulations. Brain injuries are also modeled using mathematical models.
Animal studies Although such work is done less frequently these days, from the 1960s to the 1980s several researchers experimented with primates in whiplash crash simulations. Much was learned concerning the types of soft tissue lesions that could be produced, most of which were not visible using conventional x-ray techniques. Researchers have measured the subcortical EEG in rhesus monkeys exposed to simulated whiplash trauma. They found abnormal hippocampal spiking and subclinical epilepsy-an interesting finding in view of the association between memory and the hippocampus.
Researchers have more recently subjected pigs to controlled whiplash experiments, measuring pressure changes within the spinal canal which result from changes in canal volume as the neck moves in extension and flexion. The head angular accelerations and displacements were consistent with a moderate to moderate-to-severe CAD injury (peak head acceleration of ~25 g; peak displacement of ~75 deg.). None of the animals displayed any obvious neurological abnormality afterward, but minimal capsular bleeding in the cervical ganglia was discovered. Using Evans dye, they determined that many nerve cells within the spinal ganglia (mostly from C4-C7) had lost their normal blood-nerve barrier and conjectured that these changes could be sufficient to cause a similar loss and rebuilding of the afferent synaptic connections within the laminae of the posterior horn of the cord, and that this could contribute to the symptoms of whiplash in patients weeks after trauma. These experiments set the stage for the development of the Neck Injury Criterion (NIC). Note: The Spine Research Institute of San Diego is not engaged in animal research of any kind.

Cadaver studies There is a great deal of research currently available utilizing cadavers or, as they are called in this field of research, post mortem human subjects (PMHS), or even less sympathetically, post mortem test objects (PMTO). The value of using PMHS is that there is no risk to human volunteers. Moreover, unlike human volunteers, we can dissect the PMHS to identify what types of injuries might have occurred during testing. We can also attach accelerometers and other instruments, as well as photoreflective targets directly to the subjects which can provide information not attainable with live human subjects. There are, of course, a number of drawbacks and limitations as well. Nevertheless, a good deal of our current knowledge in this field was initially discovered using this kind of testing which might involve whole specimens, isolated spinal segments, or even isolated facet joints alone.

ATDs Anthropometric test devices (ATD), a.k.a. crash test dummies, have been used for many years as surrogates or stand-ins for humans in tests that are deemed too dangerous for human test subjects. The most familiar of these ATDs to most Americans is the Hybrid III dummy which is currently the designated model used in FMVSS crash tests. While it does serve as a useful surrogate in these higher speed (30-35 mph) frontal crash tests, it does not have sufficient neck flexibility or compliance for use in low speed rear impact crash tests-it is said to lack biofidelity. For example, because the Hybrid III does not have an articulated thoracic spine, it cannot experience the flattening of the kyphotic thoracic curve that results in spinal compression and upward motion seen in human volunteers. Its cervical spine is also too stiff to simulate a relaxed human cervical spine. Thus, there has been a need for a biofidelic rear impact dummy (RID) ATD to use in the development of more effective automotive safety systems. In recent years, two such ATDs have been developed. The RID (currently the RID2), was developed at TNO Netherlands and is manufactured by First Technology Safety Systems, of Plymouth, MI. It uses a modification of the Hybrid III torso which is designed for testing the chest loads imparted by safety restraints. It has rib units and a single joint in the thoracic spine and is called the test device for human occupant restraint (THOR). It has been used to evaluate restraint systems. A completely modified neck, which moves in all cardinal planes (flexion-extension, lateral flexion, and rotation), was added to this dummy to make the RID2.
The second RID, the biofidelic rear impact dummy (BioRID II in its current stage of development) was developed at Chalmers University. Unlike the RID2, it has a fully articulated spine from top to bottom, but moves only in the anterior to posterior (flexion-extension) plane. Currently it is manufactured by Robert A. Denton, Inc./Denton ATD, Inc., in Rochester Hills, MI. Both dummies have been extensively tested by institutional members of the European Whiplash Consortium, the International Insurance Whiplash Prevention Group (IIWPG) formed by Allianz Zentrum fur Technik (AZT), the German Insurance Institute for Traffic Engineering (GDV), IIHS, and the Motor Insurance Repair Research Center (MIRRC), Thatcham. Finally, the Spine Research Institute of San Diego conducted full scale, human subject validation tests of both the RID2 (2002) and the BioRID II (2003). Both ATDs have been shown in SRISD tests to have good biofidelity.
Human subject crash test studies Severy et al. conducted the original full scale rear impact crash tests in the 1950s and 1960s and deserves tribute for their pioneering efforts. Despite the fact that the cars they used in their first series of tests were WWII era Plymouths and Hudsons, and the fact that the equipment today is much more sophisticated than what was used back then, and despite the fact that those old cars had relatively rigid bumpers, no head restraints, and no shoulder harnesses, the results they obtained back then are surprisingly similar to those we obtain today in our modern fleet of cars sporting microchip technology. Most notably, Severy's group were the first to show that the acceleration of a volunteer's head in LOSRIC could be up to 2-3 times (or more) higher than that of his vehicle because of the unique and complex occupant-vehicle coupling of this type of crash.
Subsequently, a number of researchers have conducted human subject crash tests-some using seats mounted on hydraulically accelerated sleds, others in full scale, car-to-car configurations. These include the work of West et al., Szabo et al., McConnell et al., Castro et al., Ono et al., Siegmund et al., van den Kroonenberg et al., Davidsson et al., and Croft et al. (see Croft AC, Haneline MT, Freeman MD: Differential occupant kinematics and head linear acceleration between frontal and rear automobile impacts at low speed: evidence for a differential injury risk. International Congress on Whiplash-Associated Disorders, Berne, Switzerland, March 9-10, 28, 2001; and Croft AC, Haneline MT, Freeman MD: Differential Occupant Kinematics and Forces Between Frontal and Rear Automobile Impacts at Low Speed: Evidence for a Differential Injury Risk, International Research Council on the Biomechanics of Impact (IRCOBI), International Conference, September 18-20, 2002, Munich, Germany, 365-366). This research has taught us, collectively, a great deal about how the human subject interacts with the vehicle; knowledge that simply cannot be gained using mathematical models, animal models, or human cadavers.
Some authors have reported that crash test subjects begin to complain of neck pain or headaches in rear impact crashes when crash velocities reached about 5 mph delta V and these comments have gradually been transmogrified into a threshold for human tolerance, albeit through no fault of these authors. There are, unfortunately, several reasons why such extrapolations cannot be made from these tests. In many cases, the crash test subjects were exposed to multiple impacts. It is likely that tolerance to these crashes is diminished with successive tests. More importantly, none of the studies has been designed specifically to determine human tolerances to these forces. Such a study would require relatively large numbers of subjects who would need to be representative of the general population and who would also need to be tested under representative crash conditions. The results of the tests would have to be subjected to statistical analysis in order to determine that the results were not likely to be simply the result of chance. No published tests to date satisfy those scientific requirements. So, while they can tell us much about human kinematics and other important factors, they cannot be used to determine injury thresholds or to develop tolerance corridors.
Researchers recently conducted low speed crash tests and reported that 29% of their subjects developed symptoms in tests of only 2.5 mph delta V, providing compelling evidence against the popular 5 mph delta V threshold theory. Moreover, in a large German study in which real world crashes were reconstructed, the authors reported that of the rear impact crashes investigated, in 42% the crash speed was below 6.2 mph delta V. (For a more in-depth explanation of the limitations of attempting to establishing injury thresholds using this literature, see Freeman MD, Croft AC, Rossignol AM, Weaver DS, Reiser M: A review and methodologic critique of the literature refuting whiplash syndrome. Spine 24(1):86-96, 1999.)

Epidemiological and clinical literature In 1995 the Quebec Task Force on Whiplash-Associated Disorders set out to synthesize the existing whiplash literature. After searching the world literature on this topic, they found over 10,000 citations; most of this can be found in the clinical literature (see Spitzer WO, Skovron ML, Salmi LR, Cassidy JD, Duranceau J, Suissa S, Zeiss E: Scientific monograph of the Quebec task force on whiplash-associated disorders: redefining "whiplash" and its management. Spine (Supplement) 20(8S):1S-73S, 1995). Using rigid criteria that excluded more than 99% of that literature from further review severely limited the breadth and, consequently, the validity of that document.