New Research-Possible Pathological Mechanism at Work in Chronic Whiplash Not Previously Researched
By Richard H. Adler
December 13, 2001
We recently learned that an abstract paper will be published in the 2001 proceedings of the Cervical Spine Research Society Annual Meeting that potentially breaks new ground in understanding the etilogy of chronic spine pain.1 The abstract, “Whiplash Injury and Occult Vertebral Fracture: A Case Series of SPECT Imaging of Patients with Persisting Pain Following a Motor Vehicle Crash,” involves many researchers including Michael Freeman, Ph.D., D.C., M.P.H, Dan Sapir, M.D., Alex Boutselis, M.D., John Gorup, M.D., Glen Tuckman, M.D., Arthur Croft, D.C., M.P.H., M.S., Chris Centeno, M.D., Arnie Phillips, M.D.
The following is a reprint of the abstract:
The pathology of chronic whiplash injury continues to be a controversial subject in the literature, with some authors claiming that long term pain following whiplash is a factitious disorder. These claims are made despite a growing canon of research demonstrating the cervical zygapophysis as a primary source of pain in approximately half of all chronic whiplash cases.
Other research suggests that the intervertebral disc may be a source of continuing pain, associated with so-called rim lesions and other disc injuries. The pathomechanics of whiplash resulting from a rear impact collision include both segmental hyperextension in the lower cervical spine during the initial rearward movement of the head as well as flexion following the rebound of the head off the head restraint, suggesting forceful loading of both posterior and anterior elements of the cervical spine. Recent cadaver testing of simulated whiplash has resulted in findings of injuries including fracture of both the vertebral body and elements of the neural arch, leading to the supposition that bony injury can occur with both the extension and flexion phases of whiplash trauma.
While plain x-ray with lateral flexion and extension views is the generally recognized standard for evaluating bony injury and instability following whiplash, it is not particularly sensitive for the presence of incomplete cortical disruption such as endplate fractures and subchondral fractures of the facet. In the current investigation, we undertook bone scan and SPECT evaluation of consecutive patients who were referred for significant refractory pain following whiplash trauma based on the hypothesis that there may be a subpopulation of these patients who have continued symptoms resulting from unhealed occult fracture.
Of the 15 referrals, one could not obtain insurance coverage for the study and thus did not undergo the diagnostic imaging. Of the remaining 14 subjects who were studied, ten had positive findings on bone scan and/or SPECT (71%). Nine of the ten positive studies closely corresponded with the patient-reported symptoms. The most frequent finding was vertebral endplate fracture, found in six cervical (60%) and three thoracic (30%) vertebrae.
There were occult fractures identified in the lateral mass/lamina region of two cervical (20%) and two thoracic (20%) vertebra. A spinous process fracture was identified in the thoracic spine of one (10%) subject.
There were ten females and four males in the study, with an average age of 33.3 (SD 9.0). The bone scan and SPECT imaging was performed an average of 18.9 months post-crash (SD 13.5, range 2-47). Pain levels were uniformly high, with average VAS scores of 7.8 (SD 1.1).
Seven of the crashes were rear impact (50%), four were side impacts (29%), and three were front end impacts (21%). Nine of the occupants were drivers (64%) and ten were wearing seatbelts (71%). It did not appear that any of the fractures were a result of direct contact with the vehicle interior.
None of the subjects had fractures that were detectable on plain film, even after reviewing the SPECT images and rereading the radiographs. Ten of the subjects had MRI testing prior to the bone scan/SPECT protocol, and of these, six had signs of disc bulging in the cervical spine, four had disc bulges in the thoracic spine, and one had a frank thoracic herniation. One subject had undergone prior cervical discectomy and fusion, but had uptake activity in an area other than the healed fusion.
Our results, even though of a limited sample of patients, suggest a (possible pathological mechanism at work in chronic whiplash that has not been previously described. While other authors have reported vertebral fractures resulting from whiplash trauma, none that we are aware of have suggested unhealed fractures as a potential source of chronic pain. Lack of specificity of bone scan and SPECT imaging for fracture may be a factor in our series, however, the high correlation of symptoms to findings suggests a traumatic rather than degenerative etiology. Greater subject numbers are needed in order to perform meaningful subgroup analyses relating to gender, age, and injury and crash details as risk factors for occult spinal fracture following whiplash. Our findings may point to more effective methods of dealing with chronic spine pain resulting from motor vehicle crashes.
1 Special thanks to Michael D. Freeman, PhD, DC, MPH, Forensic Trauma Epidemiologist, Department of Public Health and Preventive Medicine, Oregon Health Sciences University School of Medicine, the lead author of this abstract in bringing this to our attention.