When considering whiplash injuries, three questions are important:
- What are the primary tissues that are injured during whiplash trauma?
- Which injured tissues are responsible for chronic whiplash injury pain?
- Which conservative treatments are best at preventing and treating chronic whiplash injury pain?
Discussions to help answer these questions are to come in the following pages. However, I believe first a brief review of fundamental yet often misunderstood whiplash biomechanics is warranted.
Historically, it had been thought and extensively taught that whiplash injury was the consequence of hyperextension of the cervical spine. The usual explanation was based upon Sir Isaac Newton’s Law of Inertia, first published in 1687 (1).
However, in 1995, Whitman E. McConnell and colleagues from Biodynamic Research Corporation performed a series of 28 low speed automobile collisions (velocity changes up to 6.8 mph) on 7 male volunteers (2).
All 7 of the volunteer test subjects initially sustained typical whiplash symptoms such as neck discomfort and headaches. Prior to being exposed to the collision, each subject had his sitting range of cervical spine extension measured.
The video assessment of cervical extension during the collision clearly showed that none of the volunteer subject’s cervical spines actually hyperextended. In fact, in some cases the extension of the cervical spine during the collision was up to 40° less extension that the subject could perform while seated prior to the collision. The authors concluded that…
Hyperextension Of The Cervical Spine
Was Not The Cause Of The Subject’s Symptoms.
These findings by McConnell and colleagues initiated a series of experiments to determine the mechanism by which whiplash trauma could cause injury and symptoms without causing cervical spine hyperextension.
The first widely published experiment appeared in the journal Spine two years later, in November 1997 (3).
In this study, Grauer and associates from the Department of Orthopaedics and Rehabilitation at Yale University School of Medicine performed a series of rear-end collisions on human cadavers. Because the subjects in this series were cadavers, exposure to ionizing radiation was moot, allowing the team to view cervical spine dynamics during the collision using cineradiography.
This unique method of assessment brought forth the following conclusions and opinions:
- In the earliest phase of the cervical spine dynamics following a rear-end collision, the cervical spine forms an “S” shaped configuration, with flexion of the upper cervical spine and simultaneous significant hyperextension of the lower cervical spine.
- The tissue distortion noted during this “S” configuration of the cervical spine was of a magnitude that is injurious.
- This injurious “S” configuration of the cervical spine occurs very quickly, between 50 – 75 milliseconds following impact.
- The quickness of this “S” configuration of the cervical spine is shorter than the time required by the stretched muscles to react and to afford meaningful protection of the cervical spine joints. Therefore, the injury is primarily imparted to the joints of the cervical spine.
- In most cases, this quick injurious “S” configuration of the cervical spine occurs before the head contacts the head restraint, meaning the head restraint often does not offer adequate protection.
Several other cadaver studies confirmed this “S” configuration of the cervical spine in the initial phase of whiplash injury.
In 1999, similar cineradiography studies were performed on live human volunteers by Kaneoka and colleagues (4), and the results were the same as those of the cadaver studies.
This 1999 live human volunteer study generated this following official Point of View, published in Spine:
POINT OF VIEW
Nikolai Bogduk, MD, PhD, DSc, FAFRM
Department of Anatomy and Musculoskeletal Medicine
University of Newcastle
Newcastle Bone and Joint Institute
Royal Newcastle Hospital
Newcastle, New South Wales, Australia
“The study of Kaneoka et al now fills a critical gap in the story of cervical facet pain. It provides the missing biomechanical link. Their’s is the most significant advance in the biomechanics of whiplash since the pioneering studies of Severy et al in 1955.”
“As a result of this study, we no longer rely on inference or speculation; we have a direct demonstration of the mechanism of injury in whiplash.”
Essentially all articles published regarding whiplash biomechanics since 1997 – 1999 cite these studies that agree the pathology of whiplash primarily occurs during this “S” configuration very early on (50–75 ms) following the collision. As an example, last fall (October 2007), a review article by Schofferman and colleagues (5) titled:
Chronic whiplash and whiplash-associated disorders: An evidence-based approach
Journal of the American Academy of Orthopedic Surgeons
makes the following comments:
“In a typical rear-end motor vehicle collision, the injury is caused by the abnormal biomechanics of neck motion resulting from the forward and upward motion of the torso while the head lags behind as the result of inertia.”
“Whiplash injury is any structural damage sustained because of the whiplash forces.”
“The forward acceleration of the torso deforms the cervical spine into a nonphysiologic S-shaped curve, with extension developing between the lower segments and flexion developing between the uppermost segments. Most of the whiplash injury occurs during this deformation phase.”
With this basic and fundamental review complete now we’ve laid the groundwork for this month’s discussion of “The 3 Critical Components Of A Whiplash Injury…
Critical Whiplash Component #1
What are the primary tissues that are injured during whiplash trauma?
Importantly, the 1999 live human cineradiography cervical spine biomechanical study by Kaneoka and colleagues (4) showed that the primary injury from whiplash trauma was to the facet joints and to the intervertebral disc. Their article makes the following points:
“The zygapophysial joint is the suspected origin of neck pain after rear-end car collision.”
“The facet joint collision that occurs during the first phase of whiplash trauma creates a bending moment. “If this bending moment is large enough, this motion is likely to cause the disruption of the disc from the vertebral rim (rim lesion) or to cause a zygapophysial joint injury.”
“Most whiplash injuries occur during low-speed rear-end collisions and rarely produce morphologic changes such as fracture of the joint. The zygapophysial joint is a synovial joint and has a synovial fold (meniscus), between the articular facets that is innervated with nociceptive receptors. Thus, we hypothesize that facet collisions are likely to impinge on and inflame the synovial folds in the zygapophysial joints, causing neck pain (facet synovial fold impingement syndrome).”
Once again, in the POINT OF VIEW by Dr. Nikolai Bogduk noted previously following the Kaneoka study, the following comments are found:
“The critical observation is that in whiplash the lower cervical segments undergo sagittal rotation about an abnormally high instantaneous axis of rotation. As a result, there is no translation; there is only rotation. As the vertebra spins, its anterior elements separate from, while the posterior elements crunch into, the vertebra below. This mechanism predicts that the resultant lesions should be tears of the anterior annulus and fractures of the zygapophysial joints or contusions of their meniscoids. These are the very lesions seen at postmortem.”
In 2002, additional evidence for whiplash trauma causing injury to the facet joints and intervertebral disc of the lower cervical spine was presented by Lars Uhrenholt and colleagues from the Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark (6). Their study, published in Spine, was titled:
Cervical spine lesions after road traffic accidents: a systematic review
The authors concluded that occult pathoanatomical lesions in the cervical intervertebral disc and zygapophysial joints were possible in survivors of motor vehicle collisions. This article was also well summarized in the Point Of View from Dr. Nikoli Bogduk, as follows:
Point of View
Nikolai Bogduk, MD
This study has “harvested the best available evidence concerning the possible pathology of whiplash.”
The injuries documented include:
(1) Articular fractures
(2) Intra-articular contusions
(3) Tears of the anterior annulus
“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 joints.”
“Biomechanical studies show how these joints can be injured to produce the lesions seen at mortem.”
“Clinical studies have shown that zygapophysial 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.”
Two years later, in 2004, Pearson and colleagues from the Biomechanics Research Laboratory, Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, published in the journal Spine the most detailed evidence to date showing the biomechanics of facet joint injury during whiplash mechanism (7). Their article is titled:
Facet joint kinematics and injury mechanisms during simulated whiplash
The same year, 2004, the same group from Yale, lead by Panjabi, published in the journal Spine the most detailed experimental evidence on the biomechanics of intervertebral disc injury during the whiplash mechanism (8). Their article is titled:
Injury mechanisms of the cervical intervertebral disc during simulated whiplash
Critical whiplash component #1 answers the question… “what are the primary tissues that are injured during whiplash trauma?”
The answer appears to be the facet and the intervertebral disc. These studies conclusively show that the primary soft-tissue injury caused by whiplash collisions is to the facets and intervertebral discs of the lower cervical spine.
Critical Whiplash Component #2
Which injured tissues are responsible for chronic whiplash injury pain?
The tissue sources for chronic post-traumatic neck pain were thoroughly evaluated by Drs. Nikoli Bogduk and Charles Aprill in 1993 and published in the journal Pain (9). In this study, the authors evaluated the sources of chronic neck pain by using both provocation discography and cervical zygapophysial joint blocks. Comments found in their study include:
“Both a symptomatic disc and a symptomatic zygapophysial joint were identified in the same segment in 41% of the patients.”
“Discs alone were symptomatic in only 20% of the sample.”
“Zygapophysial joints were symptomatic but discs were asymptomatic in 23%.”
“Only 17% of the patients had neither a symptomatic disc nor a symptomatic zygapophysial joint at the segments studied.”
Neck muscle injury “does not provide a satisfying model for persistent or chronic neck pain” because extremity muscle injuries heal rapidly, “in a matter of days or weeks.”
“Persistent neck pain suggests injury to tissues that heal poorly or slowly, such as the intervertebral disc and the facet joints. “However, painful disorders of these structures are not demonstrable by plain radiography, computed tomography or magnetic resonance images.”
No findings on plain radiography, computed tomography or magnetic resonance images are correlated with pain.
The most frequent finding was “both a symptomatic disc and a symptomatic zygapophysial joint at the same segment,” seen in 41%.
The second most frequent finding was a symptomatic zygapophysial joint, alone, with no disc involvement, which was found in 23%.
“This indicated that 64% of the sample had a symptomatic zygapophysial joint.” [41% + 23% = 64%]
The third most frequent finding was a symptomatic disc alone, with no zygapophysial joint involvement, found at 20%.
“This indicated that 61% of the sample had a symptomatic disc.”[41% + 20% = 61%]
“If cervical segments are fully investigated, it emerges that cervical discs are not the most common, primary source of neck pain.”
“A large proportion, if not the majority, of patients with post-traumatic neck pain have symptomatic zygapophysial joints.”
In 1995, members of the Cervical Spine Research Unit from the Faculty of Medicine, University of Newcastle, Callaghan, Australia, published a study in Spine (10) to determine the prevalence of cervical zygapophysial joint pain in patients with chronic neck pain after whiplash. In this study, these authors note and conclude:
“In a significant proportion of patients with whiplash, chronic, refractory neck pain develops.”
“Painful joints were identified in 54% of the patients.”
“In this population, cervical zygapophysial joint pain was the most common source of chronic neck pain after whiplash.”
The following year, in 1996, the same Australian group repeated their study, this time including a placebo control. Once again they published their findings in Spine (11). Their findings and conclusions include:
“Overall, the prevalence of cervical zygapophysial joint pain (C2-C3 or below) was 60%.”
“Cervical zygapophysial joint pain is common among patients with chronic neck pain after whiplash.”
The evidenced based review of chronic whiplash and whiplash-associated disorders, published in the Journal of the American Academy of Orthopedic Surgeons, October 2007 (5), makes the following statements:
“The cervical facet joint is the most common source of chronic neck pain after whiplash injury, followed by disk pain. Some patients experience pain from both structures.”
“The facet joints are the most common source [more than half of the cases] of chronic neck pain after whiplash injury.”
“Some patients have pain that arises from a disk, and some have a combination of facet joint pain and discogenic pain.”
Critical whiplash component #2 answers the question, “Which injured tissues are responsible for chronic whiplash injury pain?”
The answer appears to be the facets and the intervertebral disc. Note, the same tissues responsible for chronic whiplash injury pain (Critical Whiplash Component #2) are the same tissues primarily injured during whiplash trauma (Critical Whiplash Component #1): the facet joints and the intervertebral disc.
Critical Whiplash Component #2
Which conservative treatments are best at preventing and treating chronic whiplash injury pain?
Less is known about the successful conservative treatment of whiplash injuries than is known about the biomechanics of whiplash injuries. However, with respects to the healing of injured soft tissues, studies indicate that early persistent mobilization is significantly superior to immobilization. Two such studies include the 1986 article by physician John Kellett (12), published in the journal Medicine and Science in Sports and Exercise and titled:
Acute Soft Tissue Injuries
A Review of the Literature
The second article is by Pekka Kannus, MD, PhD (13). Dr. Kannus is chief physician and head of the Accident and Trauma Research Center and a sports medicine specialist at the Tampere Research Center of Sports Medicine at the UKK Institute in Tampere, Finland. His article was published in the journal The Physician And Sports Medicine in 2000, and titled:
Immobilization or Early Mobilization After an Acute Soft-Tissue Injury?
Specifically pertaining to whiplash injury, Mark Rosenfeld and colleagues (14) compared the six-month outcome of whiplash-injured patients who were treated either with a cervical collar or no collar and in contrast with early mobilization. Their article was published in Spine in 2000, and titled:
Early Intervention in Whiplash-Associated Disorders
A Comparison of Two Treatment Protocols
Clearly, early mobilization was superior in clinical improvement as compared to the use of a cervical collar. Sadly, the patients who were immobilized earliest following their injury reported a 90% incidence of chronic pain at the six-month follow-up evaluation.
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 (15). The article was published in the Annals of Internal Medicine and titled:
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 also 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.”
There are two studies evaluating the chiropractic management of chronic whiplash injuries. The first was published in the journal Injury in 1996 (16), and titled:
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.”
The second article pertaining to the chiropractic management of chronic whiplash appeared in the Journal of Orthopedic Medicine in 1999 (17), and is titled:
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.”
Lastly, in the evidenced-based review article on whiplash from the October 2007 Journal of the American Academy of Orthopedic Surgeons noted above (5), Dr. Schofferman and colleagues note:
Treatments for acute neck pain include remaining active despite ongoing pain, performance of prescribed exercises, and possible inclusion of spinal manipulation, which can improve outcomes over exercise alone.
Critical whiplash component #3 answers the question, “Which conservative treatments are best at preventing and treating chronic whiplash injury pain?” And it clearly appears to be early mobilization, including manual therapy and manipulation, along with exercise.
Summary and Conclusion
In summary and conclusion, this article supports the following:
- Whiplash biomechanically injures the facets and intervertebral discs of the lower cervical spine.
- The facets and intervertebral discs are proven to be the most probable source of chronic post-traumatic whiplash pain.
- Early persistent mobilization is the most effect treatment for post-traumatic whiplash pain. Superior clinical outcomes are achieved if the early mobilization includes a combination of passive motions, manipulation, and exercise. This protocol has the best chance to avoid post-traumatic chronic pain. If post-traumatic chronic pain does occur in a whiplash-injured patient, specific joint manipulation is appropriate treatment with a high percentage of clinical improvement.
2) McConnell, Whitman E; Howard, Richard P; Van Poppel, Jon; Krause, Robin; Guzman, Herbert M; Bomar, John B; Raddin, James H; Benedict, James V; Human Head and Neck Kinematics After Low Velocity Rear-End Impacts–Understanding “Whiplash”; Society of Automobile Engineers Document Number: 952724, November 1995.
3) Grauer JN, Panjabi MM, Cholewicki J, Nibu K, Dvorak J. Whiplash produces an S-shaped curvature of the neck with hyperextension at lower levels. Spine. 1997 Nov 1;22(21):2489-94.
4) Kaneoka K, Ono K, Inami S, Hayashi K. Motion analysis of cervical vertebrae during whiplash loading. Spine. 1999 Apr 15;24(8):763-9.
5) Schofferman J, Bogduk N, Slosar P. Chronic whiplash and whiplash-associated disorders: An evidence-based approach; Journal of the American Academy of Orthopedic Surgeons; October 2007;15(10):596-606.
9) Bogduk N, Aprill C. On the nature of neck pain, discography and cervical zygapophysial joint blocks; Pain; August 1993;54(2):213-7.
10) Barnsley L, Lord SM, Wallis BJ, Bogduk N. The prevalence of chronic cervical zygapophysial joint pain after whiplash. Spine. 1995 Jan 1;20(1):20-5.
12) Kellett J. Acute soft tissue injuries–a review of the literature; Medicine and Science in Sports and Exercise. Oct. 1986;18(5):489-500.
13) Kannus P. Immobilization or Early Mobilization After an Acute Soft-Tissue Injury?; The Physician And Sports Medicine; March, 2000; Vol. 26 No. 3, pp. 55-63.
14) Rosenfeld M, Gunnarsson R, Borenstein P. Early Intervention in Whiplash-Associated Disorders: A Comparison of Two Treatment Protocols; Spine July 15, 2000;25:1782-1787.
15) Hoving JL, Koes BW, de Vet HCW, van der Windt DAWM, Assendelft WJJ, van Mameren H, Devillé WLJM, Pool JJM, Scholten RJPM, Bouter LM. PhD. Manual Therapy, Physical Therapy, or Continued Care by a General Practitioner for Patients with Neck Pain A Randomized, Controlled Trial; Annals of Internal Medicine, May 21, 2002, Vol. 136 No. 10, pp. 713-722.
16) M. N. Woodward MN, Cook JCH, Gargan MF, and Bannister GC. Chiropractic treatment of chronic ‘whiplash’ injuries; Injury; Volume 27, Issue 9, November 1996, pp 643-645.
17) Khan S, Cook J, Gargan M, Bannister G. A symptomatic classification of whiplash injury and the implications for treatment; The Journal of Orthopaedic Medicine 21(1) 1999, 22-25.