Chronic low back pain (CLBP) is one of the most common health problems in Western societies. In Europe, one out of every five people experiences significant back pain that infers with quality of life [
1]. In addition to its broad prevalence, CLBP is one of the major causes of medical expenses, work absenteeism and disability [
2]. Since cognitive behavioral models of CLBP have become more widely accepted, a large variety of behavioral interventions have become available for the treatment of CLBP [
3]. Psychological interventions have been found to be effective, with cognitive behavioral treatments showing moderate to large effect sizes for reducing self-reported pain, pain-related interference, depression and disability [
4]. However, it is unknown which interventions work best for particular subgroups of patients [
3,
5,
6] and more research is needed to define subgroups [
5]. Vlaeyen and colleagues developed a treatment focusing on fear-avoidant back pain patients [
7]. This treatment, known as graded
in vivo exposure, is based on the fear-avoidance model of chronic pain, which postulates that fear and avoidance of movement contributes to the maintenance of pain via mechanisms of classical conditioning and reinforces disability [
8]. As in the treatment of anxiety disorders, the patient is gradually exposed to a feared stimulus, which in the case of CLBP is movement believed to lead to pain or potential injuries to the back. Approximately 10 years ago, the first single case designs showed that
in vivo exposure reduced pain disability, pain catastrophizing, and pain-related fears with large effect sizes [
7,
9‐
11]. In addition to the case studies, three randomized controlled trials (RCTs) have compared graded exposure to a waiting list, graded activity programs [
12,
13] or treatment as usual, for example, usual medical care [
14]. These studies found that
in vivo exposure was superior to control conditions at reducing pain-related fears and catastrophizing. Only one study found effects (at the trend level) on pain-related disability [
14]. In summary, the efficacy of exposure treatment in the RCTs was inferior relative to the preceding case studies.
Problem definition
Several questions concerning exposure in vivo treatment (EXP) for chronic back pain remain unanswered:
First, there is a lack of empirical evidence regarding whether interventions tailored for particular subgroups, such as
in vivo exposure for fear-avoidant pain patients, are more effective than traditional cognitive behavioral treatments for the management of chronic pain problems (CBT-P). Although a variety of definitions of CBT exist, we favor the description provided by Turk, which incorporates behavioral (principles of learning), emotional and cognitive factors. Thus, we attempt to teach our patients “to recognize the connections linking cognitions, affective, behavioral, and physiologic responses together with their joint consequences” [
18]. Thus far,
in vivo exposure has not been compared to cognitive behavioral treatment as it is usually delivered in clinical practice.
Second, it is unknown how many sessions of EXP are needed to achieve sufficient results and that patients get the needed benefit. In a single case paradigm, Vlaeyen
et al. found significant reductions in disability and pain-related fears after only three exposure sessions [
7]. On the other hand, recent reviews indicate that there is evidence that prolonged psychological treatment in chronic pain patients is beneficial [
19,
20]. Hansen and colleagues showed that between 13 and 18 sessions of therapy in general are required for 50% of patients to improve [
21]. Besides the research on the dose–response relationship in psychotherapy in general it is also very important to evaluate and develop the adequate treatment of more specialized treatment approaches. Thus, the analysis of the dose–response relationship in exposure treatment for chronic pain is needed to establish an effective and economical length of treatment.
Third, CLBP is often described as a socio-economic problem because it is a major cause of medical expenses, work absenteeism and disability [
2]. However, economic aspects of CLBP treatments (for example, cost-effectiveness) have generally received little attention and thus should be incorporated into RCTs [
5,
22].
Objectives
The present investigation, which began recruitment in August 2011 and is currently ongoing, utilizes a three-arm randomized controlled trial method to assess the efficacy of graded in vivo exposure (EXP) for CLBP relative to cognitive behavioral therapy (CBT-P). To our knowledge, this is the first study to implement in vivo exposure for CLBP patients in an outpatient setting in Germany, and is also the first study to compare graded in vivo exposure to CBT. Accordingly, we will assess the feasibility of this new treatment approach. Dose-effects will be analyzed by comparing a short and a long version of EXP. In addition, cost-effectiveness will be evaluated. Besides, the main questions meditational analyses and examination of effects of generalization are planned.
Research questions
1)
Is EXP more effective (at post-treatment and at six-month follow-up) at reducing pain-related disability and pain intensity (primary outcomes) as well as other symptoms compared to CBT-P in patients with fear-avoidance beliefs?
2)
Are there any differences in treatment effects between the short (10 sessions) and the long (15 sessions) versions of exposure at post-treatment and at six-month follow-up?
3)
What is the cost-effectiveness of EXP as compared to CBT-P?