Chronic neck pain and whiplash review

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Chronic neck pain and whiplash: A case-control study of the relationship between acute whiplash injuries and chronic neck pain

Michael D Freeman, PhD DC MPH,1 Arthur C Croft, DC MPH MS,2 Annette M Rossignol, ScD,3 Christopher J Centeno, MD,4 and Whitney L Elkins, MPH4
Abstract: The authors undertook a case-control study of chronic neck pain and whiplash injuries in nine states in the United States to determine whether whiplash injuries contributed significantly to the population of individuals with chronic neck and other spine pain.

Four hundred nineteen patients and 246 controls were randomly enrolled. Patients were defined as individuals with chronic neck pain, and controls as those with chronic back pain. The two groups were surveyed for cause of chronic pain as well as demographic information. The two groups were compared using an exposure-odds ratio. Forty-five per cent of the patients attributed their pain to a motor vehicle accident. An OR of 4.0 and 2.1 was calculated for men and women, respectively.

Based on the results of the present study, it reasonable to infer that a significant proportion of individuals with chronic neck pain in the general population were originally injured in a motor vehicle accident.

The rate of recovery following acute whiplash injuries has been the subject of multiple studies. The majority of these studies have been designed as either prospective or retrospective case series, in which there was no control group. Generally, the prospective studies are of higher quality because they use an inception cohort, and are more likely to include consecutive patients presenting to a hospital emergency room (1–9). In comparison, the retrospective studies are more likely to describe cohorts that have been assembled from a specialist’s practice. These studies are more susceptible to bias in the patients’ recall of the etiological event initiating their symptoms, because the patients are enrolled months, and sometimes years, after the original injury (10–18).

Notwithstanding the efforts of prior researchers, there are many unanswered questions regarding the nature of late whiplash, for example:

  • how do individuals with chronic neck pain compare with individuals with other chronic spinal pain with regard to a history of a motor vehicle accident (MVA) as the origin of their pain; and
  • what is the contribution of late whiplash to the total pool of individuals with chronic neck pain in the general population.

The objective of the present study was to compare exposure histories of consecutive patients with chronic neck pain presenting to a random sample of chiropractors’ offices with the exposure histories of consecutive patients with chronic back pain presenting to the same office. The primary exposure history of interest was prior involvement in an MVA. As a matter of practicality, attribution of cause of pain was used as a surrogate for cause of pain in the present study. We chose to study patients in chiropractic practices because:

  • most chiropractic patients present with complaints of spine pain (19);
  • typically, a substantial proportion of a chiropractor’s practice consists of patients with chronic neck and back pain (20); and\
  • in the United States, chiropractors are the initial treating physician for one of three individuals who seek treatment for spine pain (21), and provide 40% of all treatment for low back pain (22); thus, chiropractors treat a broad cross-section of the population with spinal pain.

Conclusion:

The study findings suggest that injuries resulting from MVAs contribute significantly to the population of individuals with chronic spine pain in the United States. In addition, individuals with chronic pain in the neck, and neck and back, are more likely to have acquired their pain as a result of an MVA, in comparison with individuals with chronic back pain alone. The present study suggests that chronic symptoms following whiplash, or ‘late whiplash’, is considerably more prevalent than previously reported (19,28).

  • The prevalence of chronic neck pain in the general population has been estimated by various authors to range from 13.8% for both sexes, to 32.9% for women and 27.5% for men (28). Extrapolating the 45% etiological fraction of MVA injuries found in the present study to the most conservative estimate of chronic neck pain prevalence (13.8%) yields 6.2% prevalence of late whiplash, or 15.5 million Americans alone, with this chronic pain disorder. This figure is close to an estimate published earlier by Croft (29).
  • Whiplash injuries are common in industrialized countries. For many years, the whiplash-injured individual with persistent symptoms has been viewed by some as an opportunist, a malingerer, or both. Even the originator of the term ‘whiplash’ later joked that a whiplash injury was “any strain of the cervical spine that doesn’t resolve until all litigation is concluded” (30). Although the connection between whiplash injuries and litigation has been investigated and refuted in several studies (8,9,13–15), the motives of individuals seeking compensation for chronic pain resulting from an MVA injury continue to be questioned (16). Thus, further well-controlled studies of the chronic effects of whiplash might serve to resolve this misperception.
  • While further study of late whiplash is needed, the present study helps to clarify several of the ambiguities regarding the disorder, leading to better understanding of the epidemiology of the condition, and eventually, the mitigation or prevention of late whiplash.