Prognosis Following Whiplash Injury

Chronic pain and disability from a whiplash injury is still the most common injury after a car accident or other similar (often sports) accident. Whiplash occurs when the head and neck extend backward and then flex forward in a rapid transfer of energy to the neck. Persistent neck pain, arm pain, headache, and other symptoms following such an accident have been labeled whiplash-associated disorder (WAD).

The costs of such an injury (both direct and indirect costs) are substantial. So much so that researchers are looking for ways to predict who might develop WAD. The goal is to prevent this from happening. Past studies of WAD have not been high-quality or did not collect data in the same way, thus making it difficult to combine information and look for predictive factors.

In this systematic review and meta-analysis, the authors did an extensive search of the published literature on WAD. They limited their search in order to look for consistent factors that might predict who would develop chronic symptoms following a whiplash injury.

For example, only studies published after 1995 were included. That was for two reasons. First, it postdated (came after) the Quebec Task Force (QTF) publication. That was the first systematic review on whiplash-associated disorder. The authors of this study knew from the QTF that the work done up until that time offered very little information in the area of risk and predictive factors of disability. Second, the Quebec study reported that up until 1993, there were no high-quality studies to depend on for information on WAD.

For this new review, only patients for whom data was collected within three weeks of the injury were included. And then only those patients who were followed for at least six months were part of the study. Some length of time in follow-up is really necessary to identify patients with WAD-related symptoms and/or disability.

In order to evaluate studies for quality in design and methodology, a special scoring tool was developed. Each study was evaluated using this scoring tool. It helped the researchers look at how the studies were done, how they were analyzed, and how the results were interpreted. Consideration was given to such things as how missing data was handled, differences in facilities treating whiplash injuries (e.g., emergency departments, specialist clinic, primary care clinic), and geographic location (country where the article was published).

Not every study reviewed gathered the same data or even looked at the same predictors. The scoring tool made it possible to compare the results despite the inconsistencies. In fact, there were over 200 predictors studied. Types of predictors followed included age, gender, general health before the accident, education, occupation, income, marital status, type of insurance, pain intensity, body mass index, seat belt usage, neck range-of-motion, and use of medication before the accident.

When they sorted through all the possible predictors, there were 25 that appeared in more than one study. A closer look placed these 25 predictive factors into one of four categories: 1) patient demographics (characteristics), 2) information about the collision, 3) previous patient history, and 4) patient symptoms.

In the end, they found that there were nine significant predictors of pain and disability after whiplash injury. Health-care professionals examining patients following a whiplash injury can look for any of these factors when establishing a prognosis: high school education, female, history of neck pain before the accident or injury, neck and/or headache pain rated as 55 or more out of 100, no seat belt use at the time of the accident, and catastrophizing.

Catastrophizing refers to irrational thinking that something is far worse than it actually is. Patients who catastrophize see their current situation in a negative light. They tend to think that the worst possible outcome will happen. Catastrophizing is associated with pain intensity, psychological distress, and pain-related disability among individuals with chronic pain.

The authors provide a table with a summary of their key findings. They were able to breakdown the results into variables with strong evidence of a significant effect, variables with moderate evidence of a significant effect, variables that just miss significance, and variables with strong evidence of no effect.

This kind of information is helpful in planning treatment that can focus on significant variables. Most of the variables with strong evidence of no effect had to do with the collision (rear-end, no head rest, vehicle not moving when hit). The strongly significant predictive factors included high level of neck pain and headache at the first evaluation and no higher education level than high school. A high rating of neck pain intensity present from the start increased patients' risk of chronic pain/disability by six times.

Two things are not evaluated by this study. First, because patients were assessed within the first three weeks of their injury, legal factors were not included. Not having insurance or hiring a lawyer were not significant factors predicting outcome. If data was collected later in the process, these two factors might figure more prominently in the long-term prognosis.

And second, no attempt was made to determine how multiple factors present at the same time might affect patient prognosis. Most patients do have more than one risk factor. Whether multiple risk factors add to the risk or even multiply the risk remains unknown. It's possible that certain factors when present together could double or triple the risk of developing chronic pain and disability.

The authors make several recommendations based on their findings from this study. Anyone examining a patient with a whiplash injury should make note of any variables with moderate-to-strong evidence of a significant effect. This study can be used in an evidence-based practice when determining a patient's prognosis. This type of information is helpful when seeking reimbursement from insurance companies. And when documenting the presence of these factors, it should be remembered that this evidence is based on only single (not multiple) risk factors.

David M. Walton, PT, MSc, et al. Risk Factors for Persistent Problems Following Whiplash Injury: Results of a Systematic Review and Meta-Analysis. In Journal of Orthopaedic & Sports Physical Therapy. May 2009. Vol. 39. No. 5. Pp. 334-350.

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