In any case, I'd like to see your data and research design. I'm sure there are problems with it, as there are unavoidable confounds in the best of human crash test data and research design.
The data sources I use on the prevalence, incidence and risk of whiplash are based on whiplash epidemiologic literature (For example, see Freeman MD, Croft AC, Rossignol AM: Chronic neck pain and whiplash: a case-control study of the relationship between acute whiplash injuries and chronic neck pain. Submitted. Also see Bovim G, Schrader H, Sand T: Neck pain in the general population. Spine 19(12)1307-1309, 1994) and recent crash tests with cadavers, BioRid dummies, and human volunteers. If you're talking about incidence of whiplash, then 3 million injuries per year in the U.S. is the most realistic figure (1172 per 100,000) today. The 1971 figures put the number at 1 million. If you're talking prevalence, then outcome and prognostic studies suggest that from 12% to 86% of whiplash victims will continue to be symptomatic for years after the injury (mixed vector collisions). For rear-end impacts only, see:
Ellertsson AB, Sigurjóusson K, Thorsteinsson T: Clinical and radiographic study of 100 cases of whiplash injury. Acth Neurol Scand (Suppl) 67:269, 1978.
Olsson I, Bunketorp O, Carlsson G, et al.: An in-depth study of neck injuries in rear end collisions. 1990 International IRCOBI Conference, Bron, Lyon, France, September 12-14, 1-15, 1990.
Norris SH, Watt I: The prognosis of neck injuries resulting from rear-end vehicle collisions. J Bone Joint Surg 65B(5):608-611, 1983.
Parmar HV, Raymakers R: Neck injuries from rear impact road traffic accidents: prognosis in persons seeking compensation. Injury 24(2):75-78, 1993.
Watkinson A, Gargan MG, Bannister GC: Prognostic factors in soft tissue injuries of the cervical spine. Injury 22(4):307-309, 1991.
Gargan MF, Bannister GC: The rate of recovery following whiplash injury. Eur Spine J 3:162-164, 1994.
Borchgrevink GE, Lereim I, Ryneland L, Bjorndal A, Haraldseth O: National health insurance consumption and chronic symptoms following mild neck sprain injuries in car accidents. Scand J Soc Med 24(4):264-271, 1996.
Squires B, Gargan MF, Bannister GC: Soft-tissue injuries of the cervical spine: 15-year follow-up. J Bone Joint Surg 78-B(6):955-957.
Gargan M, Bannister G, Main C, Hollis S: The behavioral response to whiplash injury. J Bone Joint Surg 79-B:523-526, 1997.
Rear impact injuries have a worse prognosis than side or frontal impact injuries. On average about 46% of the patients in these studies had not recovered completely at follow-up--about 10% rating their problems as "disabling" or "severe". Using these outcome studies, in conjunction with the incidence figure of 3 million, Croft estimated the following prevalence figures:
1) Assuming a more conservative 2 million injuries per year and a 25% non-resolution of symptoms, after 25 cumulative years of whiplash, the prevalence of chronic pain in the U.S. would be 6731/100,000, or 6.7% of the population.
2) Assuming 50% non-resolution of symptoms (which I believe is more realistic), after 25 cumulative years of whiplash, the prevalence of chronic pain in the U.S. would be a remarkable 9615/100,000, or 9.6% of the population.
When we talk about risk, then the PUBLISHED crash tests are particularly relevant. Clearly, we're seeing injuries in the human volunteers as low as 2.5-5.0 mph delta V. There seems to be no debate regarding the injury threshold among the majority of researchers (with the exception of nut-cases like Robert Ferrari and Anthony Russell from Canada). And I would first say to you, what proof do you have that your research subjects have not been harmed or injured long-term? The longitudinal studies have yet to be performed. Many of the PUBLISHED studies have not followed-up on the research subjects after the crash tests in any systematic way. Worse, many of the studies are defining injuries only to the neck, without performing cognitive and psychological testing (neuropsychological testing), without looking at the TMJ, lower back, brain, or extremities. The known injuries from whiplash are extensive, and come to us from looking at whiplash patients who died of other causes within day
s after their whiplash crashes (see Taylor's and Panjabi's extensive studies on this). But if you haven't read Kanno, Ono, Kaneoka in the engineering literature, or Bogduk in the medical, then you're missing an awful lot.
It is well known in medicine that osteoarthrosis occurs more rapidly secondary to trauma. From Kaneoka, Ono, Panjabi, Cholewicki and Bogduk (and others), we know that the cervical spine zygapophyseal joints are injured at low speeds, and damage to these joints causes chronic, recurring pain. We also know that cervical spine ligamentous instability occurs after low speed crashes (damage to anterior and posterior longitudinal ligaments, for example), and that this instability is responsible for chronic pain. Prolotherapy may be a solution for these patients. So I would propose to you that the low speed crashes producing injuries are simply injury thresholds. Since serious spinal cord injuries have been reported at delta V's of 15 mph (rear-end impacts), then the 5-15 mph delta V range would show the full gamut of injuries in between.
It is amazing to me that all doctors learn about referred pain in medical school (i.e., right shoulder blade pain from gallbladder disease, left arm pain from myocardial infarct, low back pain from prostate disease or pelvic inflammatory disease, etc., ad nauseum), but then FORGET ABOUT IT! Bogduk has mapped out referral pain patterns from damaged zygapophyseal joints, following in a long line of research into referred pain by Feinstein and others since the early 20th century. No one has ever refuted any of this work. And yet, we have some insurance company doctors who think that if there are "non-dermatomal" findings in our patients, and if MRI's are negative, that there couldn't be an injury, or worse, we have a malingerer. Nonsense. Medicine has become too spinal disc-centered. God bless Dr. Bogduk for reminding us all that there are MANY OTHER LIGAMENTS IN THE SPINE, that they are OFTEN injured in whiplash crashes, that they cause AS MUCH PAIN as a herniated disc in many whi
plash victims, and that they are USUALLY MISSED by ER doctors, orthopedists, and neurosurgeons/ neurologists. Sad, very sad.
Have you read Kaneoka and Ono's work? Brault and Siegmund's? Bogduk's group's research (and Wallis, Lord, and Barnesley)? Croft's? Freeman's?
In addition, one has to remember that the human volunteers in almost all the recent crash tests were:
robust males
in excellent health
perfectly positioned (not leaning forward or to the side)
without any backset (distance between the head and head restraint)
without head rotation
completely aware of the impending collision
of younger age
Real world occupants have the following risk factors for acute injury:
1) Female gender (12 studies).
2) History of neck injury (one study).
3) Poor head restraint geometry/tall occupant (e.g., 80th percentile male) (2 studies).
4) Rear vs. other vector impacts (16 studies).
5) Use of seat belts/shoulder harness (i.e., standard three-point restraints) (30 studies).
6) Body mass index/head neck index (i.e., decreased risk with increasing mass and neck size) (2 studies).
7) Out-of-position occupant (e.g., leaning forward/slumped) (studies).
8) Non-failure of seat back (3 studies).
9) Having the head turned at impact (one study).
10) Non-awareness of impending impact (3 studies).
11) Increasing age (i.e., middle age and beyond) (5 studies).
12) Front vs. rear seat position (6 studies).
13) Impact by vehicle of greater mass (i.e., 25% greater) (2 studies).
14) Crash speed under 10 mph (one study).
Real world occupants have the following risk factors for poor outcome or prognosis (chronic pain, symptoms):
1) Female gender (2 studies).
2) Body mass index in females only (one study).
3) Immediate/early onset of symptoms (i.e., within 12 hours) and/or severe initial symptoms (6 studies).
4) Ligamentous instability.
5) Initial back pain (one study).
6) Greater subjective cognitive impairment (2 studies).
7) Greater number of initial symptoms (one study).
8) Use of seat belt shoulder harness (2 studies). For neck (not back) pain (one study); non-use had a protective effect.
9) Initial physical findings of limited range of motion (one study).
10) Initial loss of ROM (one study and different from Number 9).
11) Initial neurological symptoms (one study).
12) Past history of neck pain (one study) or headache (one study).
13) Initial degenerative changes seen on radiographs (4 studies).
14) Loss or reversal of cervical lordosis (one study).
15) Increasing age (i.e., middle age and beyond) (4 studies).
16) Front seat position (one study).
Clearly, human crash tests have a major problem with external validity, as there are many risk factors NOT present in human crash tests. That is clearly A MAJOR FLAW in your example of one, and most likely in your "office" crash tests. The most important risk factor for initial severity of injury, in my opinion, is lack of awareness (preparedness, really, which is a different thing) of the impending impact. There is no human volunteer who is not fully aware of the impending impact, no matter how loud the music on the headphones may be (if your group even thought to do that).
So if we could put the full spectrum of humans into these crashes at low speeds, with heads turned, totally unaware and unprepared, with prior injuries, osteoarthritis, osteoporosis, etc., using thin (ectomorphic) females with a history of headaches, etc., then we would be approaching external validity.
Tell me your "office" did that, and I'll introduce you to some gentlemen who will talk to you about Helsinki.
This is supposed to be a forum for serious discussion. Better do your homework.
Sincerely,
Greg Wright
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