The Importance of Understanding the Relationship Between Vehicle Crush and Patient Injury
The headline and front-page photographs were stunning and unbelievable. On Saturday, November 22, 2014, the front page of the San Francisco Chronicle newspaper led with this headline (1):
11-Story Plummet: What Onlookers Saw
“The first inkling that office workers scurrying along Montgomery Street had that something was wrong came when they looked up to see a blue blur falling from the sky. Some thought it was debris—but then it got closer, and the crowd began to scream and scatter. It was a man, plummeting 11 stories towards them.”
“With a thump and a crash of shattering glass, the middle – aged window washer smashed into a moving car just after 10 a.m. Friday morning. He lay wincing and miraculously alive …on the crumpled roof of a green Toyota Camry.”
Peter Melton, from the California Department of Industrial Relations, noted:
“It seems pretty clear the cushioning of the car he fell onto kept him alive.”
The universe and our world are under the control of the principles of math, physics, chemistry, etc. The principles of inertia have likewise always been with us, but they were not officially acknowledged through publication until Isaac Newton wrote, in the year 1687, the book Mathematical Principles of Natural Philosophy.
Inertia is the resistance of a physical object to any change in its state of motion or rest. As often stated, an object in motion will remain in motion unless an outside force acts upon that object. Likewise, an object at rest will remain at rest unless an outside force acts upon that object.
When the laws of inertia are applied to a whiplash injury, it is quickly pointed out that different parts of a single object can have different inertias, depending upon how the object’s mass is distributed. Specifically the human body (a single object) can have different inertias between the trunk and the head. In a rear-end motor vehicle collision, the struck vehicle, its seat, and trunk of the occupant are quickly propelled forward, while the head, having its own inertial mass, will remain at rest. The head remains still, while the body is moved forward, under the head. This gives the appearance that the head is extending upon the trunk, the so-called “hyperextension” phase of a rear-end motor vehicle collision.
Hyperextension As Trunk Is Pushed Under Head
Under these circumstances, the most vulnerable body part to injury is not the trunk nor the head, but rather the part of the body that balances these two larger inertial masses to each other, the neck. Because of the large inertial masses of the trunk and the head, the neck is historically very vulnerable to “inertial injury.” In this context, an “inertial injury” means that there is no direct blow or contact injury to the neck.
A horrible example of a neck inertial injury is the injury sustained in “shaken baby syndrome.” The violent shaking of the baby’s trunk causes the baby’s head to inertially “bounce” on the neck, often leading to catastrophic neck injuries. The neck and spinal cord can sustain horrific injuries, even though there is no direct blow to the head or neck of the child; these are inertial injuries.
Cervical spine (neck) inertial injuries caused by motor vehicle collisions are the rule, and their occurrence is not controversial. Yet, because there are many pain-producing tissues in the neck (discs, facet capsules, ligaments, muscles, tendons, nerves, bone, skin, etc.), research has been conducted to determine if there is one particular tissue in the neck that might be responsible for the predominance of whiplash mechanism induced cervical spine inertial injury pain. Alas, one such tissue has been identified. It is the facet joint capsular ligaments (2, 3, 4, 5, 6, 7, 8). In fact, in 2002, Nikolai Bogduk, MD, PhD, states of the Uhrenholt study (4) in the following, attached, Point Of View:
This study has “harvested the best available evidence concerning the possible pathology of whiplash.”
The credibility of these injuries is enhanced because different lines of investigation, using totally independent methods, point to the same conclusion. “This constitutes convergent validity.”
“In the case of whiplash, postmortem studies, biomechanics studies, and clinical studies converge.”
“Postmortem studies point to lesions in the zygapophysial [facet] joints.”
“Biomechanical studies show how these joints can be injured to produce the lesions seen at mortem.”
“Clinical studies have shown that zygapophysial [facet] joint pain is common in patients with chronic neck pain after whiplash.”
“All three lines of investigation point to the same culprit,” the facet joint.
Chiropractic spinal adjusting (manipulation) affects the facet joints. As described by Canadian Orthopedic Surgeon and Professor, William Kirkaldy-Willis, MD (9):
“Spinal manipulation is essentially an assisted passive motion applied to the spinal apophyseal [facet] and sacroiliac joints.”
There are mechanical neurophysiological explanations as to how spinal manipulation inhibits pain. The most accepted of these involve the use of the Gate Theory by Ronald Melzack and Patrick Wall (10, 11), established more than 50 years ago. This Gate Theory has survived the test of time (12). As described by R. Kirkaldy-Willis (9):
Melzack and Wall proposed the Gate Theory of Pain in 1965, and this theory has “withstood rigorous scientific scrutiny.”
“The central transmission of pain can be blocked by increased proprioceptive input.” Pain is facilitated by “lack of proprioceptive input.” This is why it is important for “early mobilization to control pain after musculoskeletal injury.”
The facet capsules are densely populated with mechanoreceptors. “Increased proprioceptive input in the form of spinal mobility tends to decrease the central transmission of pain from adjacent spinal structures by closing the gate. Any therapy which induces motion into articular structures will help inhibit pain transmission by this means.”
A number of important studies have documented the remarkable benefit of cervical spine (neck) joint manipulation (adjustment) for neck pain including for chronic whiplash mechanism neck pain. A few such studies include these (13, 14, 15, 16):
In 1996, the journal Injury published a study titled (13):
Chiropractic treatment of chronic ‘whiplash’ injuries
The authors of this study are from the University Department of Orthopaedic Surgery, Bristol, UK. The authors retrospectively evaluated the effects of chiropractic in a group of 28 patients who had been referred with chronic ‘whiplash’ syndrome. The 28 chronic whiplash patients in this study were treated by a chiropractor using “specific spinal manipulation, proprioceptive neuromuscular facilitation, and cryotherapy.” The treatment was evaluated by an independent orthopedic surgeon, M. Woodward, who was blinded as to the treatment. The results showed that following chiropractic treatment, 93% of the patients had improved. The authors stated:
“The results of this retrospective study would suggest that benefits can occur in over 90% of patients undergoing chiropractic treatment for chronic whiplash injury.”
In 1999, a second article pertaining to the chiropractic management of chronic whiplash appeared in the Journal of Orthopedic Medicine, and is titled (14):
A symptomatic classification of whiplash injury and the implications for treatment
In this study, the authors retrospectively evaluated 93 consecutive patients seen in chiropractic clinics for chronic whiplash symptoms. All patients underwent spinal manipulation, a high velocity, low amplitude thrust to a specific vertebral segment by a licensed chiropractor. These authors made the following points and conclusions:
“Conventional treatment of patients with whiplash symptoms is disappointing.”
“In chronic cases, no conventional treatment has proved successful.”
“Chiropractic is the only proven effective treatment in chronic [whiplash] cases.”
“Our results confirm the efficacy of chiropractic, with 69 of our 93 patients (74%) improving following treatment.”
“The results from this study provide further evidence that chiropractic is an effective treatment for chronic whiplash symptoms.”
In 2002, physical therapist Jan Hoving and colleagues published a randomized clinical trial in the treatment of acute neck pain involving physician care v. exercise v. manual manipulative therapy. The article was published in the Annals of Internal Medicine and titled (15):
Manual Therapy, Physical Therapy, or Continued Care by a General Practitioner for Patients with Neck Pain A Randomized, Controlled Trial
In this study, “Manual Therapy” was defined as:
“Orthopedic manipulative (manual) therapy is a specialization within physical therapy and provides comprehensive conservative management for pain and other symptoms of neuro-musculo-articular dysfunction in the spine and extremities.”
These authors made the following points and conclusions:
“At 7 weeks, the success rates were 68.3% for manual therapy, 50.8% for physical therapy, and 35.9% for continued [physician] care.”
“Manual therapy scored consistently better than the other two interventions on most outcome measures.”
“In daily practice, manual therapy is a favorable treatment option for patients with neck pain compared with physical therapy or continued care by a general practitioner.”
“Primary care physicians should consider manual therapy when treating patients with neck pain.”
“The success rates for manual therapy were statistically significantly higher than those for physical therapy.”
“Patients receiving manual therapy had fewer absences from work than patients receiving physical therapy or continued [physician] care.”
“In our study, mobilization, the passive component of the manual therapy strategy, formed the main contrast with physical therapy or continued care and was considered to be the most effective component.”
In 2012, Gert Bronfort, DC, PhD, and colleagues from Northwestern Health Science University, published a study in the Annals of Internal Medicine, titled (16):
Spinal Manipulation, Medication, or Home Exercise With Advice for Acute and Subacute Neck Pain A Randomized Trial
This study sought to determine the relative efficacy of spinal manipulation therapy (SMT), medication, and home exercise with advice (HEA) for acute and subacute neck pain in both the short and long term. This was a randomized, controlled trial using 272 subjects aged 18 to 65 years who had nonspecific neck pain for 2 to 12 weeks. The intervention was 12 weeks of SMT, medication, or HEA.
The primary measurement outcome was participant-rated pain, measured at 2, 4, 8, 12, 26, and 52 weeks after randomization. Secondary measures were self-reported disability, global improvement, medication use, satisfaction, general health status (Short Form-36 Health Survey physical and mental health scales), and adverse events. The main conclusion from these authors is:
“For [neck] pain, SMT had a statistically significant advantage over medication after 8, 12, 26, and 52 weeks.”
“For participants with acute and subacute neck pain, SMT was more effective than medication in both the short and long term. However, a few instructional sessions of HEA resulted in similar outcomes at most time points.”
“Our results suggest that SMT and HEA both constitute viable treatment options for managing acute and subacute mechanical neck pain.”
This study clearly shows the superiority of chiropractic spinal manipulation over pharmacologic management of patients suffering from acute and subacute neck pain. However, the findings that chiropractic spinal manipulation and home exercise with advice (HEA) achieved similar results on these patients requires discussion.
The printed words in the article suggest that chiropractic spinal adjusting and home exercise/advice are essentially equal in the management of acute and subacute neck pain. Yet, a careful review of the measured markers presented in the article show that chiropractic adjustments were nearly always superior to those from home exercise/advice. As examples, nine markers are listed for “Portion With Absolute Reduction In Pain”: spinal adjusting was superior in 8 of 9 of the listed markers. Six markers are listed for “Pain Score”: spinal adjusting was superior in 5 of the 6 markers listed.
Additionally, a careful review of the charts presented in the article show that during the randomization, nearly twice as many of the chiropractic group (29.7%) had trauma initiated neck pain compared to the home exercise/advice group (16.5%). Trauma triggered neck pain is always more difficult to manage in both the short and long term as compared to non-trauma triggered neck pain. It appears that the chiropractors had a “tougher” patient draw as compared to the home exercise /advice group. This finding was not discussed in the text of the article.
Although the article states several times that the chiropractic adjustments were given over a period of 12 weeks, the actual range of adjustments was 2-23 with a mean of 15.3. This is slightly more than 1 adjustment per week for 12 weeks. In contrast, the home exercise/advice group was seen only 1 or 2 times, but instructed to do neck exercises at home daily. The exercises consisted of 7 isolated maneuvers that required 3 different positions: sitting, supine head supported, and supine head unsupported. Each maneuver required 10 repetitions, and the patient was instructed to repeat all of the maneuvers 6-8 times per day. Performing the exercise maneuvers as prescribed takes approximately 10 minutes per session. As such, the authors are advocating that patients with acute/subacute neck pain exercise 60-80 minutes per day. This is both impractical and unrealistic.
Back to the “Protection of Crush”
Can a patient involved in a vehicle-to-vehicle collision sustain a crushing type of injury? Yes, of course. However, outside of the emergency department, such injuries are quite rare. Rather, chiropractors primarily treat whiplash inertial injuries, as noted above.
The inertial injuries sustained by the occupant of a struck motor vehicle is dependent upon the rate of struck vehicle acceleration, and distance such vehicle moved (17). Consequently, anything that reduces the forward acceleration of the struck vehicle will reduce inertial injuries to the occupants of that vehicle. Interestingly, one factor that reduces the acceleration of the struck vehicle is the “crushing” of that vehicle.
World-class pole vaulters routinely clear a bar that is approximately 20 feet high.
What goes up must come down. To protect the athlete, the landing pit is constructed of foam. Imagine what the consequences would be if the landing pit were made of concrete; the landing athlete would no doubt be injured.
The foam in the landing pit protects the athlete because it “crushes” when the athlete lands on it. It is precisely this crushing that dissipates the energy from the falling athlete, protecting her/him from injury. In contrast, concrete would not crush and disperse the energy, and the athlete would be injured.
These injury-sparing principles apply to motor vehicle collisions. When a struck vehicle crushes, it dispersed energy that otherwise would accelerate the vehicle, increasing occupant inertial injuries. This concept has been recognized for decades and is often published. As an example, in 1982, Ian MacNab, MD, succinctly states (17):
“The amount of damage sustained by the car bears little relationship to the force applied. To take an extreme example: If the car was stuck in concrete, the damage sustained [crush] might be very great but the occupants would not be injured because the car could not move forward, whereas, on ice, the damage to the car could be slight but the injuries sustained might be severe because of the rapid accelerations permitted.”
The point is that vehicle “crush” is protective of the occupant because it dispersed energy that would otherwise increase the vehicle’s acceleration. In the opening story, the crushing of the roof of the falling window washer was certainly responsible for saving his life. Of course, this all changes if the vehicle is crushed so severely that the occupant also sustains a “crushing” injury.
Other studies that support this “crushing” principle include:
• In 1986, the Journal of Musculoskeletal Medicine publish a study titled (18):
Objective Findings for the Diagnosis “Whiplash”
The amount of damage to the automobile bears little relationship to the force applied to the cervical spine of the occupants. The acceleration of the occupant’s head depends upon the force imparted, the moment of inertia of the struck vehicle, and the amount of collapse of force dissemination by the crumpling [crushing] of the vehicle.
• In 1989, the journal of the Society of Automotive Engineers, published a study titled (19):
Whiplash in Low Speed Vehicle Collisions
“…experimental results indicate that some vehicles can withstand a reasonable high speed impact without significant structural damage [crush]. The resulting occupant motions are marked by a lag interval, followed by a potentially dangerous acceleration up to speeds greater that of the vehicle.
As the vehicle becomes stiffer [less crush], the vehicle damage costs are reduced as less permanent deformation takes place. However, the occupant experiences a more violent ride which increases the potential for injury.
…the average acceleration experienced by the occupant in the elastic [no crush] vehicle would be approximately twice that of the plastic [crushed] vehicle. This theory implies that vehicles which do not sustain damage [crush] in low speed impacts can produce correspondingly higher dynamic loadings on their occupants than those which plastically deform under the same of more severe impact conditions.”
• In 1993, the journal Trial Talk published a study titled (20):
The Physics, Biomechanics and Statistics of Automobile Rear Impact Collisions
“The absence or presence of vehicle damage is not a reliable indicator of injury potential in rear impacts. Based upon the principle of conservation of energy, any energy which does not go into damaging [crushing] the vehicle must be converted into kinetic energy, the source of injuries.”
• In 1997, the journal of the Society of Automotive Engineers published a study titled (21):
Lack of Relationship Between Vehicle Damage and Occupant Injury
Using a mathematical analysis and examples