Wednesday, November 2, 2011

low speed impacts, Akron Square Chiropractic

Low-Speed Rear Impact Collision

Conference of the Society of Automotive Engineers: A Synopsis

By Arthur Croft, DC, MS, MPH, FACO
On August 8-9, 1994 I attended the Low-Speed Rear Impact Collision technical workshop of the Society of Automotive Engineers in Irvine, California. The program was organized by a gentleman from Collision Research and Analysis, Inc. I was initially disappointed in the speakers who addressed the audience of engineers, designers, physicians, accident reconstructionists, attorneys, and scientists. Several of the speakers had no advanced degrees and, despite the titles they awarded themselves (research engineer, etc.), they appeared to be accident reconstructionists with a decidedly defense-biased attitude. (More than 80 percent of the clients of accident reconstructionists are defense lawyers). Side comments concerning the "green poultice syndrome" were met with predictable audience snickers. They shared their work on seatback stiffness testing and simple rear impact crash testing, but there is nothing particularly interesting to report. One of the researchers who served as volunteer in a very low speed crash test was not wearing his restraint system. When asked why by one of the audience, he replied, "It doesn't make any difference if they are used in low speed impacts." Hmmmm.
The program also included plaintiff and defense attorneys. Both naturally followed party lines. The plaintiff lawyer pointed out that it is important to be able to show actual damage to a vehicle and provided several examples that attested to significant collisions in cars that appeared, to the untrained eye, undamaged. Bolts on the frame that were bent or sprung seatbacks were a few examples. The defense attorney discussed the problems of reliability of the science used in the courtroom, citing as a recent example the case of Dauber vs. Merrill Dow. The proposed use of "qualified juries" (i.e., those with special education or knowledge) in complicated cases will not come into being, in his opinion.
Dennis Schneider, PhD, president of Biokinetics Engineering, Inc., discussed some of the recent research leading up to our current state of knowledge of whiplash. Most of what he reviewed can be found in chapter one of my textbook (Whiplash Injuries: The Cervical Acceleration/Deceleration Syndrome, First Edition).4 His talk was lucid and enlightening. Alan Nahum, MD, spoke very briefly. I thought his notions were out of date. He used dated photographs from Ian Macnab's work to describe the whiplash phenomenon despite more recent work that has necessitated a modification of some of Macnab's models. Nahum told us, for example, that the chin will strike the chest during the flexion phase. In fact, of course, it will not.
Nahum shared the stage with Mark Gomez, PhD. Dr. Gomez gave a from-the-ground-up discussion of whiplash beginning with anatomy which I am sure was appreciated by the non-physicians in the audience. I would disagree with some of his comments, however. He said the discs do not fail in whiplash -- only the end plate or the disc/bone interface. His group experimented with the serial cutting of spinal ligaments (sounded to me like something that White and Panjabi had done) to assess their contribution to spinal stability. Interestingly, they found that the radiographic appearance was not altered by cutting the posterior ligaments.
Several engineers from Biodynamic Engineering, Inc., were on hand to share their findings from crash testing with human volunteers (themselves actually). You will not have access to this material because their "clients" will not allow them to publish their results -- a practice that runs counter to the general aims and philosophy of science. Carley Ward, PhD, the president, remarked later that the research was to be used to refute injury claims in "fraud" cases. I might add that I have had personal experience with one of these engineers. He testified for the defense in a case where I was acting as an expert for the plaintiff and stated confidently that he could precisely calculate the g forces that had been delivered to the low back of the plaintiff (merely by looking at a photograph of her car). In fact, of course, you cannot. Among other things, as an example, you must determine if the bumper isolators were functional at the time of the accident.
The presentation of the research was interesting but generally misleading. The speakers compared the effects of the low speed rear impact with amusement park rides and I was sure that most of the attendees must have concluded that it would be nearly impossible for an injury to occur under such trivial conditions. However, mingling with them later I found it heartening that many didn't buy it.
Overall, I was not pleased with the first day. None of the presenters were physicians and therefore had had no real patient contact, nor did they have any understanding of human anatomical and physiological systems. I sensed that we had spent the entire day using relatively contrived and artificial crash simulations along with applied principles of physics and engineering to "prove" that people are unlikely to be injured in low speed rear impact collisions. Epidemiological data, outcome studies, and animal research were never discussed.
The next day Donald Huelke, PhD, well known for his work in the development of the AIS scale and other projects relating to injury mechanisms in crashes, shared a new finding coming from Europe. It has been discovered that during the whiplash injury a pulse of CSF is injected under high pressure into the nerve root sleeves and may be responsible for some radicular syndromes. This has not yet been published.
Richard Howard, MD, and Whit McConnell, MD, principals of the Biodynamic Research Corporation, discussed their earlier work on full scale human volunteer crash testing1 and their most recent work (as yet unpublished). You may recall Howard as the lead author of a rather "interesting" paper that suggested that the TM joint is subjected to no more trauma in whiplash than "everyday chewing"2 -- a paper that has been highly criticized in dental circles3 and widely applied in defense strategies. Using split bite blocks in the mouths of test subjects (again, the authors themselves) they concluded that whiplash at low speeds would be about as stressful as "vigorously flossing your teeth." Hmmmm. I might point out that the "clients" of BRC are automobile insurance carriers and manufacturers. The results of all of this research have actually been quite enlightening and I have discussed the implications of it at length in the newest edition of my textbook4 which will be released in December. You should be aware, however, that their work is frequently mischaracterized in medical-legal settings -- much to the disadvantage of plaintiffs and treating doctors. Usually this takes the form of extrapolating beyond the collected data. The research shows that significant forces are applied to the head and neck, and adds greatly to our knowledge of the kinematics of these collisions. It does not prove, however, as it is frequently claimed, that persons other than "robustly healthy" middle-aged males, who are perfectly seated and restrained and prepared for an impending controlled crash, with no brakes applied, and with no second collisions, are not likely to be injured.
Also, of course, it is possible to support an incorrect hypothesis. I don't mean to belittle their important contribution to science, but it reminds me of the famous Austrian physiologist who experimented with frogs. He amputated one limb and ordered the frog to jump. It did. He then amputated another and then another. Again, when ordering to, the frog jumped. When the fourth limb was amputated the frog would not jump, providing the scientist's hypothesis that frogs become deaf when all four limbs are missing.
References
  1. McConnell WH, Howard RP, Guzman HM, et al. Analysis of human test subject kinematic responses to low velocity rear end impacts. SAE Technical Paper Series 9308889, Society of Automotive Engineers, 21-31, 1993.
  2. Howard RP, Benedict JV, Raddin JH, Smith HL. Assessing neck extension-flexion as a basis for temporomandibular joint dysfunction. J Oral Maxillofac Surg 49:1210-1213, 1991.
  3. Rogal OJ, Haden J, Keropian B, et al. (representing the College of Trauma, American Academy of Head, Neck, Facial Pain and TMJ Orthopedics): Whiplash-TMD theory refuted. News J AM Acad Head Neck Facial Pain TMJ Orthopedic 4(1):3-4, 1992.
  4. Foreman SM, Croft AC. Whiplash Injuries: The Cervical Acceleration/Deceleration Syndrome. Second Edition. Baltimore, Williams & Wilkins Co., 1995.

Arthur C. Croft, DC, MS, FACO
San Diego, California

whiplash article, akron square chiropractic

"What Causes Those Symptoms, Doctor?"

By Arthur Croft, DC, MS, MPH, FACO
Introduction: The symptoms of whiplash or cervical acceleration/deceleration (CAD) injury are very often referred to as "bizarre," particularly by authors not thoroughly familiar with the condition.
Most of us have developed methods of coping with our patients' difficult, but otherwise benign, questions. "Gee doctor, when you pushed on my right knee, I felt it behind my left ear. Why is that?" We then mumble something about how we expected that and then proceed with our examination and treatment of the patient. Don't get me wrong here, I'm not suggesting that your patients' input or questions are not important but there are times ... Other times, however, our patients have legitimate concerns and do require thoughtful answers. When cases are litigated we may find ourselves responding to questions under cross-examination or in a deposition about why a patient is in pain or is dizzy. This article will review what we do know about the signs and symptoms of CAD trauma.
Symptoms and Signs
Table I list the 14 most frequently described complaints in CAD trauma. Note that some may be related to the postconcussion syndrome, the Barre-Lieou syndrome or TMJ dysfunction.
TABLE I
Common Symptoms Following Whiplash in Order of Prevalence
Neck Pain
Neck stiffness
Trapezius pain
Headache*@+
Interscapular pain
Back pain
Paresthesiae
Extremity pain/weakness
Dizziness/lightheadedness*@+
Facial pain and TMJ related symptoms
(clicking, closed lock, etc.)+
Auditory symptoms (phonophobia,
tinnitus, loss of hearing)*@+
Vertigo*@
Ocular dysfunction (blurred vision,
photophobia)*@
Dysphagia/hoarseness
* May be part of PCS
@ May be part of Barre-Lieou syndrome
+ May be part of TMJ dysfunction
Neck pain is easily explained by tearing of any soft tissue, disc injury/herniation or end plate fracture. Immediate pain indicates more severe injury. Stiffness is usually the result of muscle spasm. Shoulder pain may be the result of direct shoulder injury or referred pain from cervical disc injury (discogenic pain) or soft tissue injury (sclerotogenous pain). Headaches can result from injury to the upper cervical spine, reflex muscle spasm, TMJ dysfunction, the Barre-Lieou syndrome (rarely) or direct brain injury (i.e. postconcussion headaches). They may also have a vascular origin.
Interscapular pain may be due to direct injury to paraspinal muscles in this area but most often is due to muscle spasm or referred (sclerotogenous) pain from cervical soft tissues or from cervical discs. Later onset indicates myofascitis. Croft and Foreman1 found low back pain (LBP) in 57 percent of their CAD cases (71 percent in broadside collisions) while Braaf and Rosner2 noted LBP in 42 percent of their cases. Hohl3 described LBP in 35 percent of his cases. It is interesting though that in a long term follow up study of CAD victims, Watkins et al.4 found that while only 24 percent initially complained of LBP, after a mean of 10.8 years, 34 percent had LBP. Precise interpretation of this is difficult.
While parathesiae are usually blamed on direct nerve injury or irritation, thoracic outlet syndrome (which is probably an advanced manifestation of myofascitis) and sclertogenous pain can be associated with paresthesiae. Other causes include sympathetic disturbance and spinal cord injury. Extremity pain and weakness may be explained in the same way. Braaf and Rosner2 found sciatica in 15 percent of their cases.
It has been shown that dizziness and lightheadedness can be produced by injection of saline solution into the SCM muscle4. Muscular injury or vascular compromise due to increased sympathetic tone may have the same effect. Inner ear damage, such as a perilymph fistula, or a minor brain injury, may give the same symptom. Tinnitus may be the result of inner ear injury, TMJ injury/derangement or (rarely) Barre-Lieou syndrome. Phonophobia typically accompanies minor head injury. Vertigo usually indicates a labyrinthine pathology or brain stem disorder, although it can be due to ischemia. Short duration vertigo (5-10 sec.) associated with quick movements of the head is referred to a benign paroxysmal positional nystagmus (BPPN). This may be due to free floating otoconia which have been detached from the otolithic membrane. With abrupt movements of the head, they are swept up in the current of semicircular canal, causing displacement of the cupola. The resulting barrage of impulses causes BPPN, a condition sometimes referred to as cupolithiasis5,6.
Pupillary dilatation will often result in blurred vision and is generally the result of injury to the sympathetic system. Note that interruption of sympathetic fibers results in miosis e.g., Horner's syndrome. Irritation has the opposite effect. Nystagmus implicates the vestibular apparatus. Photophobia is common with mild head injury. Hildingsson et al.5 have proposed dysfunction of the proprioceptive system of the cervicocranial region as an explanation for visual tracking (smooth pursuit) abnormalities.
Dysphagia and/or hoarseness often is the result of swelling/spasm of the longus colli -- one of the chief culprits in straightening of the cervical lordotic curve. However, retrotracheal or retropharyngeal hematoma may give the same symptoms and should prompt immediate investigation. Hoarseness may also reflect direct laryngeal injury or injury to cranial nerves (brain stem lesions) or the recurrent laryngeal nerve.
Most often in CAD trauma, facial pain is due to a TMJ disorder (a.k.a. TMD). Associated clicking, popping, locking, limited opening, deviations, deflections, and palpable pain should prompt TMJ evaluation/referral.
Remember that delayed onset of symptoms is quite common following CAD trauma. Classic and contemporary writings have reflected this6-13. Some authors have described delays of months or even years2 although some of these conditions represent secondary adaptations to otherwise minimally symptomatic or asymptomatic conditions. Physicians who are cognizant of these numerous conditions and their protean manifestations will be best equipped to manage CAD trauma not only from the standpoint of diagnosis and treatment but also for medicolegal reasons.
References
  1. Foreman SM, Croft AC: Whiplash Injuries: The Cervical Acceleration/Deceleration Syndrome. Baltimore, Williams & Wilkins, 1988.
  2. Braaf MM, Rosner S: Symptomatology and treatment of injuries of the neck. NY State J Med 55: 237-242, 1955.
  3. Hohl M: Soft tissue injuries of the neck in automobile accidents: Factors influencing prognosis. J Bone Joint Surg 56A(8): 1675-1682, 1974.
  4. Macnab I: The "whiplash syndrome." Orth Clin N Amer 2(2): 389-403, 1971.
  5. Hildingsson C, Wenngren B-I, Bring G, Toolanen G: Oculomotor problems after cervical spine injury. Acta Orthop Scand 60(5): 513-516, 1989.
  6. Gotten N: Survey of one hundred cases of whiplash injury after settlement of litigation. JAMA 162(9): 865-867, 1956.
  7. Goldberg AC, Rothfus WE, Deeb ZL, Frankel DG, Wilberger JE Jr, Daffner RH: Hyperextension injuries of the cervical spine. Skeletal Radiol 18: 283-288, 1989.
  8. Green JD, Harle TS, Harris JH Jr: Anterior subluxation of the cervical spine: hyperflexion sprain. AJNR 2: 243-250, 1981.
  9. Evans DK: Anterior cervical subluxation. J Bone Joint Surg 58B (3): 318-321, 1976.
  10. Hildingson C, Toolanen G: Outcome after soft-tissue injury of the cervical spine. Acta Orthop Scand 61(4): 357-359, 1990.
  11. Schneider K, Zernicke RF, Clark G: Modeling of jaw-head-neck dynamics during whiplash. J Dent Res 68(9): 1360-1365, 1989.
  12. Croft AC: Whiplash. In Steigerwald DP, Croft AC (eds): Whiplash and Temporomandibular Joint Dysfunction: a Interdisciplinary Approach to Case Management. Encinitas, Keiser Publishing, 1992 (in press).
  13. Deans GT, Magalliard JN, Kerr M, Rutherford WH: Neck sprain -- a major cause of disability following care accidents. Injury 18: 10-12, 1987.

Arthur C. Croft, D.C., M.S., FACO
San Diego, California

akron square chiropractic

Notable Observations from Three Years of Human-Subject Crash Testing

By Arthur Croft, DC, MS, MPH, FACO and Michael Haneline, DC, FICR
The Spine Research Institute has sponsored three annual human-subject crash tests, beginning with CRASH 1999 (named after the Center for Research into Automotive Safety and Health). These tests have totaled almost 50 individual crashes, with vehicle closing speeds ranging from 2-50 mph.
Crash
number
and year
of crash
Gender and
direction of
impact
(front, rear)
Vc
(mph at
time of
crash)
image V
(change in
mph, or
delta V)
Head linear
resultant
acceleration (g)
2 (99)
3 (99)
4 (99)
5 (99)
6 (99)
7 (99)
8 (99)
9 (99)
15 (99)
1 (00)
2 (00)
3 (00)
6 (00)
7 (00)
8 (00)
9 (00)
10 (00)
11 (00)
12 (00)
13 (00)
5 (01)
6 (01)
M (R)
M (R)
F (R)
F (R)
F (R)
F (R)
F (R)
F (R)
M (F)
M (R)
M (R)
M (R)
M (F)
F (F)
F (F)
F (F)
F (R)
F (R)
F (R)
M (R)
M (R)
M (R)
9.3
9.9
3.7
7.2
6.6
4.1
7.2
7.0
36.9
4.8
7.8
8.3
7.7
4.2
7.9
9.9
3.0
7.5
8.6
3.6
8.1
8.0
5.2
6.0
3.2
5.8
5.6
3.3
5.7
5.2
17.1
3.8
5.8
5.9
5.5
3.2
5.6
7.1
2.8
6.0
6.7
2.9
5.0
4.8
12.5
13.0
5.6
11.1
13.5
6.8
12.8
8.9
10.3
5.0
12.7
8.2
2.9
1.7
3.1
4.6
2.9
12.8
15.0
4.0
7.8
5.0
Table 1. Selected crash sequences from CRASH 1999 and 2000.
  1. Occupants may experience significant head accelerations without noticeable vehicle bumper damage.
  2. Occupants of (target) vehicles struck from the rear undergo approximately three times the amount of force acting on the cervical spine, compared with occupants of striking (bullet) vehicles.
  3. Vehicle speed changes are not linearly associated with occupant head accelerations.
  4. In rear-impact collisions, females (or smaller persons) generally experience greater resultant head acceleration than do males (or larger persons).
  5. Most vehicles tested have been able to withstand impacts resulting in delta Vs in excess of five miles per hour without noticeable vehicle bumper damage.
  6. Occupants who are aware and braced in rear-impact collisions experience significantly less head acceleration and less violent neck kinematics than do unaware and unbraced occupants.
The crash tests are carried out in a precise manner, utilizing established engineering practice. Institutional review board approval for human subject research is granted prior to testing in accordance with the Helsinki Doctrine. The informed and consenting human subjects (male and female) are instrumented with accelerometers, and then individually placed in instrumented crash test vehicles. Occupant accelerations are recorded for the head, thorax, and lumbar spines. Forces and moments can be calculated based on head accelerations and the principles of dynamics. Vehicle accelerations, closing velocities, and speed changes are recorded. Volunteers are subjected to rear, frontal and side-impact crashes, most of which are conducted in the "unaware" mode (subjects had no visual clues as to the time of impact and are distracted with loud music played through earphones). A few are in the "aware" mode, in which the subjects are allowed to brace for the impact. The data from a portion of the total number of crashes conducted in 1999 and 2000 is shown in Table 1.
One of our major purposes for this crash series was to compare the occupant kinematics and forces between the bullet and target vehicles. The same instrumented subjects underwent crash sequences with the same speed changes in the same vehicles under bullet and target conditions. Based on the recorded data, as well as observation of high-speed video, it is clear that the occupant kinematics and forces are dramatically different between the two crash conditions: being rear-ended is much more traumatic than rear-ending another vehicle when the subject, vehicle, and speed change are held constant.
This also addresses the common question: "How come it's always the guy in the front car who gets hurt?" A good example of this event is evident when comparing crash 9 (00) of Table 1, a frontal impact involving a female subject with a delta V of 7.1 mph and 4.6 g head acceleration; with crash 12 (00), a rear impact involving the same female subject with a 6.7-mph delta V and a remarkable 15g head acceleration.
We previously indicated that speed changes are not linearly associated with occupant head accelerations. Again, refer to Table 1, and compare crash 15 (99), a 17.1-mph delta V and 10.3g head acceleration, with crash 2 (99), where the subject experienced more significant head acceleration at only 5.2 mph delta V. The higher-speed crash test resulted in very significant crush damage to both crash test vehicles. This increased the duration of the high-speed crash test, and the resulting head acceleration to the driver of the bullet vehicle was relatively lower. Our findings in this area would be vital to present to attorneys, claims adjusters, and juries in certain real-world cases.

Another interesting finding is that multiple crash sequences can be performed within the crash metrics corridor, of which the upper boundary is generally held to be above the level that could produce injuries to human subjects (i.e., 5-mph delta V) without causing significant damage to the test vehicles. This is consistent with most of the other reported crash testing in the literature. Several of these nondamaging crash sequences are at closing speeds of nearly 10 mph. These observations are significant in light of the common myth that one can predict occupant injury from examining the vehicle damage, or that the absence of property damage is a reliable indication that the crash speeds must have been below the published bumper ratings. As a matter of fact, we exceeded these bumper ratings in nearly every test.
We also noticed that volunteers frequently reported that their heads did not make contact with the head restraints, usually after the first run, and sometimes even after the second, even though the head does make contact, which is quite obvious to the onlookers. It's not clear at this point why this rather abrupt contact is not registered by the volunteers. This phenomenon is also frequent among whiplash patients, and defense experts often use the argument that since the occupant doesn't report (or recall) striking the head restraint, it implies that no contact occurred. If that were the case, the collision would have been at a very low speed. Following this line of reasoning, the neck would not have been exposed to injurious forces.
Rear-impact crashes involving females demonstrated that they react more violently with the seat back than males. Crash 12 (00), which was a female volunteer, demonstrated the highest head acceleration of any on the entire table. Research done by Siegmund, et al.,1 found similar kinematic differences between female and male volunteers.
Finally, compare the head accelerations of crash 5 (01), an unaware and unbraced volunteer, with crash 6 (01), the same volunteer who was aware and braced for the impact. Awareness and bracing obviously have a significant effect on head and neck kinematics in rear-end collisions. A number of other researchers have found that injury is less likely when occupants in a rear-impact collision are braced. Ryan, et al.,2 found that unaware patients were 15 times more likely to have long-term pain. Consequently, this would be an important question to ask whiplash patients during the history portion of their examination.

CRASH has become an annual event, with our fourth program fast approaching in August. This year, in addition to human subjects, we will have a new RID II alpha crash-test dummy provided by First Technology in Plymouth, Michigan. We will then be able to place human volunteers in the seat next to the RID II alpha and compare the resulting accelerometry and kinematic data to help validate the dummy's biofidelity. As in previous years, qualified participants will be able to take advantage of the low-speed rear-impact crash (LOSRIC) reconstruction certification program offered in conjunction with CRASH 2002.
References
  1. Siegmund GP, King DJ, Lawrence JM, Wheeler JB, Brault JR, Smith TA. Head/neck kinematic response of human subjects in low-speed, rear-end collisions. SAE Technical Paper 973341, 1997;357-385.
  2. Ryan GA, Taylor GW, Moore VM, Dolinis J. Neck strain in car occupants: injury status after six months, and crash-related factors. Injury 1994;25(8):533-537.

Tuesday, October 18, 2011

Akron Square Chiropractic

Akron Square Chiropractic, 1419 South Arlington St, Akron, OH, 44306

Tuesday, July 12, 2011

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.