Five to ten-year prognosis of whiplash injury-related chronic neck pain: A brief report

1. Introduction

Neck pain is common after traffic accidents. Globally, more than 300 per 100,000 people visit an emergency department annually owing to neck pain after a road traffic accident [1]. Whiplash is a common mechanism of neck injury during traffic accidents, caused by forceful, rapid back-and-forth neck movement [2]. Whiplash-associated disorder constitutes the symptom sequelae following this injury, and it entails neck pain and stiffness, headache, dizziness, and paresthesia [3].

The degree of neck pain following whiplash injury ranges from moderate to severe and frequently hinders activities of daily life, resulting in poor quality of life [4]. Recovery time is also prolonged in many patients [5, 6]. Previous studies have evaluated the 1- to 2-year prognosis of whiplash injury-related neck pain in the general population reporting a relatively poor outcome [7, 8, 9, 10]. However, studies on the prognosis of neck pain after a period of over 2 years following the accident are rare. Moreover, long-term outcomes of whiplash injury-related neck pain remain inadequately evaluated. Given that the chronic pain (pain lasting ⩾ 3 months) is not easily controlled and remains unresolved for a prolonged period, we can expect the prognosis of sustained whiplash injury-related neck pain to be unfavorable [11].

Therefore, this study evaluated the prognosis of chronic whiplash injury-related neck pain that was refractory to conservative treatment (e.g., pain medication, physical modality, and injection procedures) at least 5 years after injury.

2. Methods

3. Results

Initially, 54 patients were recruited, and one investigator conducted the phone interviews. Thirty-eight (70.4%) patients answered their phones and were included in the study (Table 1).

Of the 38 respondents (male: female = 15:13), 34 (89.5%) had current, sustained neck pain caused by a prior traffic accident. The average NRS score at the initial visit was 5.3 ± 1.7 which decreased to 4.3 ± 2.6 at the follow-up interview (Table 2). There was a significant mean difference in neck pain intensity at the initial presentation and after 5 to 10-year conservative management of patients with whiplash injury (mean difference = 1.026, standard deviation = 3.004, t = 2.106, degree of freedom = 37, p = 0.042). However, after adjusting for sex, age, and duration of follow-up, no significant decrease was observed (F (1, 34) = 0.003, p = 0.954). The detailed results of repeated measures twofactor analysis, with sex, age, and duration of follow-up as covariates, are presented in Table 3. Using the results of repeated measures twofactor analysis with covariates, a post hoc power analysis was conducted on G*power, and the power was found to be 0.05, which implies that it our rsults cannot be generalize. The effect size was 0.01. Also, the normality assumption was satisfied by the Kolmogorov-Smirnova test ( p = 0.200).

Twenty-six (68.4%) patients had pain scores ⩾ 3 on the NRS. Eleven (289%) patients were taking oral pain medication prescribed by a medical doctor. Additionally, 18 (47.4%) and 12 (31.6%) patients were receiving physical modalities and injection procedures, respectively. Twenty-six (68.4%) patients were receiving at least one of the following: oral pain medications, physical modality, and injections. No patients were engaging in exercise targeted at the cervical spine. Twenty-eight (73.7%) patients experienced difficulty performing their activities of daily life and occupational duties because of whiplash injury-related neck pain.

Zygapophysealjoint injury is among the most common sources of neck pain after a whiplash injury [14, 15]. The facet joints are richly innervated by nociceptive nerves and are frequently a source of referred pain [16]. During a whiplash injury, the facet joints are at risk of overload, which potentially causes the joint capsule to tear leading to joint hemarthrosis [17]. Additionally, ligamentous tears, disc injury, and muscle injury are potential sources of neck pain after whiplash injury [17, 18]. Several studies have reported that moderate to severe anatomical damage often recovers gradually or incompletely [19, 20, 21]. Previous studies that recruited patients with acute neck pain after whiplash injury found that 50% of patients continued to complain of neck pain 1 year after trafficaccident involvement; furthermore, at 2 years, approximately 20% of patients still had whiplash injury-related neck pain [10, 20]. In this study, we found that patients with chronic neck pain (sustained for ⩾ 3 months) after whiplash injury exhibited poor long-term prognoses. Approximately 70% of patients had pain scores ⩾ 3 on the NRS after 5–10 years of injury onset. Evidence supporting the effectiveness of treatment for chronic whiplash injury-related neck pain is limited. After intraarticular facet injection with corticosteroids, 20% of patients reported relief of whiplash injury-related neck pain for more than one month [22]. Similarly, percutaneous radio-frequency neurotomy reduced neck pain in some patients for several months; however, it was not a permanent solution [23]. Botulinum toxin injection in the muscles of the cervical spine demonstrated no significant effect on pain reduction [24]. In our study, although approximately 70% of patients were receiving at least one painmanagement therapy, many patients continued experiencing pain that hindered their daily life and occupational activities. Several previous studies have demonstrated the beneficial effects of exercises targeting the cervical spine, including strengthening, endurance, and stretching, in reducing neck pain due to whiplash injury [25]. Notwithstanding none of the patients in our study were engaging in exercise. This suggests that clinicians need to emphasize the benefits and importance of exercising the cervical spine for patients with chronic whiplash injury-related neck pain.

In addition, although the mean difference in neck pain intensity at the initial presentation and after 5 to 10 years of whiplash injury was significant, in the analysis with adjustment for sex, age, and duration of follow-up, the power was too low for the results to be generalized. Therefore, when considering patients’ sex, age, and duration of follow-up, it cannot be concluded that a significant decrease in neck pain was observed after 5 to 10 years of whiplash injury.

Our study has certain limitations. First, our study is limited by the small sample size and inclusion of patients from a single institution. Therefore, selection bias might have influenced our findings. Second, only moderate-degree (grade II) whiplash injury [12] was analyzed; therefore the prognoses of grades 0, I, III, and IV whiplash injury were not investigated. Three, various numerical questionnaires, such as the Neck Disability Index and Pain Catastrophizing Scale, were not used to evaluate the prognoses of our patients with chronic whiplash injury-related neck pain. Therefore, further studies that address these limitations are warranted.

5. Conclusion

In the current study, the long-term prognosis of whiplash injury-related neck pain was found to be poor. Approximately 70% had NRS scores ⩾ 3 5–10 years after the initial injury. Chronic neck pain also hindered the patients’ daily life and occupational activities. To the best of our knowledge, this is the first study to evaluate the prognosis of chronic whiplash injury-related neck pain at least 5 years after injury. Overall, this study provides useful clinical information on the long-term prognosis of whiplash injury-related neck pain, thus potentially impacting early treatment practices.