The understanding of whiplash biomechanics was forever changed in 1997. Researchers from Yale University School of Medicine performed a series of rear-end collisions on human cadavers while imaging their biomechanics with cineradiography (1). The results established that during the earliest phase of collision mechanics, 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, especially in the lower cervical spine. As the subjects used in this initial assessment were cadavers, skepticism as to the relevance to live humans in real life collisions remained. This skepticism was mitigated within a few years with follow-up studies.
In 1999, similar cineradiography studies were performed on live human volunteers (2). The results were the same as those of the cadaver studies, solidifying the concept that the cervical spine undergoes an “S” configuration during a rear-end motor vehicle collision, primarily injuring structures of the lower cervical spine. Essentially all articles published between 1997–1999 regarding whiplash biomechanics cite these studies, noting that the pathology of whiplash primarily occurs during this “S” configuration. A representative article from 2007 states (3):
“The forward acceleration of the torso deforms the cervical spine into a non-physiologic 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.”
“The cervical facet joint is the most common source of chronic neck pain after whiplash injury.”
“The facet joints are the most common source of chronic neck pain after whiplash injury.”
Injury to the facet joints and their capsular ligaments as a consequence of the “S” configuration should be emphasized. Findings include (2):
“The zygapophysial joint is the suspected origin of neck pain after rear-end car collision.”
“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).”
Many other studies support the premise of whiplash-mechanism facet joint injury and pain (4, 5, 6, 7, 8, 9, 10).
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The entire December 1, 2011 supplement of the journal Spine is dedicated to whiplash trauma. The issue contains 27 articles by the world’s foremost authorities on whiplash biomechanics, pathology and outcomes, including the physician/clinical anatomist, Nikoli Bogduk, from Australia. Dr. Bogduk’s article in this issue of Spine is titled, “On Cervical Zygapophysial Joint Pain After Whiplash” (9).
Dr. Bogduk cites 72 references while summarizing the evidence that implicates the cervical zygapophysial joints (facets) as the leading source of chronic neck pain after whiplash trauma. He states that the patho-anatomic basis for neck pain after whiplash is not elusive, but rather well documented and well known. Dr. Bogduk notes that there is convergent validity from
All of these studies and diverse methods of investigation indicate that the primary source of chronic whiplash pain is injury to the cervical zygapophysial (facet) joints. Dr. Bogduk states:
“Collectively, these various biomechanics studies, in normal volunteers and in cadavers, predict or produce the same spectrum of lesions as that identified in postmortem studies. In particular, they indicate that the zygapophysial joints can be injured.”
“The zygapophysial joints are the single, most common source of pain in patients with chronic neck pain after whiplash.”
There is an extensive amount of evidence indicating that post-whiplash pain syndrome is attributed to injury to the cervical facet joints; no other explanation for whiplash pain has more evidence.
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Mechanically, spinal manipulation primarily affects the spinal facet joints. This is well accepted and not controversial. In 1985, Canadian Orthopedic Surgeon, WH Kirkaldy-Willis, MD, stated (11):
“Spinal manipulation is essentially an assisted passive motion applied to the spinal apophyseal and sacroiliac joints.”
Biological Plausibility
A few pertinent studies are presented below:
In 1996, clinicians from the University Department of Orthopaedic Surgery, Bristol, United Kingdom, published a study in the journal Injury, titled (12):
Chiropractic Treatment of Chronic ‘Whiplash’ Injuries
The authors note, “The whiplash syndrome is a cause of long-term symptoms for which conventional medicine has failed to discover an effective treatment.” They note that 43% of patients will suffer long-term symptoms following ‘whiplash’ injury, for which no conventional treatment has proven to be effective. Consequently, they performed a retrospective study to determine the effects of chiropractic spinal manipulation [a nonconventional treatment] in a group of 28 patients who were suffering with chronic ‘whiplash’ syndrome. The authors defined “spinal manipulation” as:
“Spinal manipulation is a high-velocity low-amplitude thrust to a specific vertebral segment aimed at increasing the range of movement in the individual facet joint, breaking down adhesions and stimulating production of synovial fluid.”
The severity of patient’s symptoms was assessed before and after treatment using the Gargan and Bannister (1990) classification protocol, as follows:
The 28 patients in this study had initially been treated with anti-inflammatories, soft collars and physiotherapy. These patients had all become chronic, and were referred for chiropractic at an average of 15.5 months (range was 3–44 months) after their initial injury. At the initial evaluation and prior to chiropractic treatment, 27/28 (96%) of the patients were classified as category C (intrusive) or D (disabling) symptoms.
Following the chiropractic treatment, 93% of the patients had improved: 16/28 (57%) improved by one symptom group, and 10/28 (36%) improved by two symptom groups. The authors concluded:
“The encouraging results from this retrospective study merit the instigation of a prospective randomized controlled trial to compare conventional with chiropractic treatment in chronic ‘whiplash’ injury.”
“The results of this retrospective study would suggest that benefits can occur in over 90% of patients undergoing chiropractic treatment for chronic whiplash injury.”
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In 1999, the same group of clinicians from the University Department of Orthopaedic Surgery, Bristol, United Kingdom, published a study in the Journal of Orthopaedic Medicine, titled (13):
A Symptomatic Classification of Whiplash Injury and the Implications for Treatment
In this study, the author’s objective was to determine which patients with chronic whiplash would benefit from chiropractic treatment. The study was a retrospective review involving 93 consecutive whiplash-injured patients. Once again, the patients were assessed using the Gargan and Bannister classification protocol. The authors note:
“Conventional treatment of patients with whiplash symptoms is disappointing.”
“In chronic cases, no conventional treatment has proved successful.”
All patients underwent spinal manipulation, defined as a “high velocity, low amplitude thrust to a specific vertebral segment.” Patients underwent a mean of 19.3 treatments (range 1-53), over a period of 4.1 months.
The authors note that their results “confirm the efficacy of chiropractic, with 69 of our 93 patients (74%) improving following treatment.” Importantly, 94% of whiplash patients with neurological signs and/or symptoms in association with neck pain and a restricted range of neck movement, including tingling, numbness, pins and needles in a dermatomal distribution in the arm or hand as well as both hypo- and hyperaesthesia, responded positively to chiropractic spinal manipulation. The authors concluded:
“The results from this study provide further evidence that chiropractic is an effective treatment for chronic whiplash symptoms.”
“Chiropractic is the only proven effective treatment in chronic [whiplash] cases.”
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In 2004, a group of physiotherapists, physicians, and professors from the Rey Juan Carlos University, Spain, published a study in the Journal of Whiplash & Related Disorders, titled (14):
Manipulative Treatment vs. Conventional Physiotherapy Treatment in Whiplash Injury: A Randomized Controlled Trial
The authors note that the clinical syndrome of whiplash includes neck pain, restriction of neck motion, dizziness, headaches, tinnitus and blurred vision. Spinal joint dysfunction and myofascial pain syndrome are thought to be one of the greatest causes of musculoskeletal disorders and symptoms in patients diagnosed with whiplash injury.
The goal of joint manipulation is to restore maximal, pain-free movement of the musculoskeletal system. “Only joints that are found to be hypomobile should be considered as candidates for high velocity low amplitude [manipulative] techniques.”
The objective of this clinical trial was to compare the results obtained from a manipulative protocol with the results obtained from a conventional physiotherapy treatment in patients suffering from whiplash injury. This is the first controlled experimental trial documenting the effects of the manipulative protocol used in this study. It was a randomized controlled trial using 380 acute whiplash injury (less than 3 months duration) subjects. All subjects were Quebec Task Force classified as grades II and III.
The injured subjects were randomly divided into 2 groups:
Group A (experimental, manipulation group)
This group was treated with high velocity-low amplitude spinal manipulation and soft tissue manipulation. The manipulation was delivered to the upper cervical spine, the cervical-thoracic junction, thoracic spine, thoracolumbar junction and pelvic girdle. Importantly, although the patients were suffering from neck pain and related symptoms, the manipulation was applies “full spine.” The treatment was weekly.
Group B (control, physical therapy group)
This group was treated with a conventional physiotherapy including active exercises, electrotherapy, ultrasound therapy and diathermy. The treatment was daily.
The outcome measures were the visual analogue scale (VAS), the cervical range of motion (CROM) in flexion and rotation, and number of sessions needed to complete the treatment.
Analysis of the change in visual analogue scale for pain showed:
Analysis of the change in cervical range of motion showed:
The authors note:
“Patients who had received manipulative treatment needed fewer sessions to complete the treatment than patients who had received physiotherapy treatment.”
“Patients of manipulative group needed an average of 9 sessions to complete the treatment, whereas physiotherapy group needed an average of 23 sessions.”
“Results showed that the manipulative group had more benefits than the physiotherapy group in the VAS and CROM.”
“Our clinical experience with these [whiplas