Discussion
The most important finding of this study was the ability of the POQ-VA to detect statistically significant positive responses to injection therapy across all domains. The largest improvements were in self-reported pain intensity, pain-related impairment in mobility and ADLs, and self-reported dysphoric effects. The single largest improvement posttreatment was a reduction in scores related to low self-esteem.
Chronic pain can be assessed in a variety of ways ranging from physical examination findings and subjective numerical ratings to extensive patient-reported questionnaires. The International Association for the Study of Pain acknowledges that pain is a complex experience and recommends assessment should be comprehensive.11 Many patient-reported questionnaires are available to clinicians, including some that address pain in a specific body part, such as the Oswestry Low Back Pain Disability Questionnaire, or those that focus on depression or quality-of-life measures, such as the SF-36.12,13
One major benefit of using the POQ-VA is its potential to demonstrate benefits across multiple domains, reflecting the complex nature of chronic pain. The POQ-VA also separates domain or scale scores, allowing clinicians to identify individuals with different patterns of dysfunction across domains.10 This separation also provides insight into which treatment options are best for chronic pain patients with predominant patterns or lower scores in certain domains. The use of a single summary score, as seen in other questionnaires such as the Roland-Morris Activity Scale, may conceal treatment-induced changes in specific outcome domains.14 Additionally, like many other similar instruments, the POQ-VA is easy to understand and use, requires no special training, takes little time to complete, and can be completed in person or over the phone.
As chronic pain has been studied further and its complexity recognized, more instruments have been developed and modified to reflect these new elements. There is no one scale applicable to all populations. A discussion about the strengths and weaknesses of each available assessment tool is outside the scope of this review. However, to date, the POQ-VA is the only instrument that has been validated to detect change following treatment of chronic pain in an exclusively veteran population.10 This validation emphasizes the importance of this study as it supports the use of this outcome measure to monitor treatment of pain in VA facilities.
One of the secondary findings indicated that injection therapy improved veterans’ physical activity levels and self-esteem and lowered pain scores as well as kinesiophobia and anxiety. The role of interventional procedures has been well established in the field of chronic pain, but their efficacy has been less clear. Injections are costly and not without risk, and these factors relegate them to fourth-line treatment options in most situations.15 Several meta-analyses have demonstrated small improvements in pain scores and patient-reported questionnaires after medial branch blocks, and lumbar or caudal ESIs for chronic back pain.5-7 However, an updated Cochrane Review concluded that there was insufficient evidence to support the use of injection therapy in subacute and chronic low back pain.8 The review acknowledged the limited methodologic quality of the trials and could not definitively report that injection therapy did not have benefits for certain subgroups of patients. The ability of researchers to detect benefit from an intervention is intrinsically linked to how outcomes are determined. The most interesting finding of our study was the patient-reported improved self-esteem scores. Many trials included in the systematic reviews discussed used outcome measures that did not have the multidimensional scope to demonstrate such a potential benefit.
Limitations
Our relatively small sample size represents the main shortcoming of this study. Because many posttreatment questionnaires were never collected, unfortunately, much potential data was lost. Most procedures performed were corticosteroid injections for the treatment of low back pain. This represented a combination of lumbar ESI, caudal ESI, medial branch blocks, and sacroiliac joint injections. The limited numbers meant that a further regression analysis of each injection type was not possible. Since few interventions treated pain in other areas of the body, it is difficult to determine whether procedures such as hip joint injections and ilioinguinal nerve blocks provided overall benefit. In the same vein, there is an inability to comment on which injection for chronic low back pain was the most efficacious.
The veteran population, while similar to the general population experiencing chronic pain, is more likely to experience PTSD and other mental health conditions.2 According to medical literature, no randomized controlled trials have been published examining pain interventions exclusively in veterans, so the applicability of these results needs further investigation. This study suggests there are potential benefits for the veteran population, not solely perhaps from receiving injection therapy, but to having access to an interventional pain clinic led by a pain physician within a network of other specialties. While limited by the inherent biases of a retrospective review, this study highlights the potential value in continuing to study this subgroup of patients, especially in the setting of an interdisciplinary approach.