Psychopathology Predicts the Outcome of Medial Branch Blocks
Psychopathology Predicts the Outcome of Medial Branch Blocks
Background: Comorbid psychopathology is an important predictor of poor outcome for many types of treatments for back or neck pain. But it is unknown if this applies to the results of medial branch blocks (MBBs) for chronic low back or neck pain, which involves injecting the medial branch of the dorsal ramus nerves that innervate the facet joints. The objective of this study was to determine whether high levels of psychopathology are predictive of pain relief after MBB injections in the lumbar or cervical spine.
Methods: This was a prospective cohort study. Consecutive patients in a pain medicine practice undergoing MBBs of the lumbar or cervical facets with corticosteroids were recruited to participate. Subjects were selected for a MBB based on operationalized selection criteria and the procedure was performed in a standardized manner. Subjects completed the Brief Pain Inventory (BPI) and the Hospital Anxiety and Depression Scale (HADS) just prior to the procedure and at one-month follow up. Scores on the HADS classified the subjects into three groups based on psychiatric symptoms, which formed the primary predictor variable: Low, Moderate, or High levels of psychopathology. The primary outcome measure was the percent improvement in average daily pain rating one-month following an injection. Analysis of variance and chi-square were used to analyze the analgesia and functional rating differences between groups, and to perform a responder analysis.
Results: Eighty six (86) subjects completed the study. The Low psychopathology group (n = 37) reported a mean of 23% improvement in pain at one-month while the High psychopathology group (n = 29) reported a mean worsening of -5.8% in pain (p < .001). Forty five percent (45%) of the Low group had at least 30% improvement in pain versus 10% in the High group (p < .001). Using an analysis of covariance, no baseline demographic, social, or medical variables were significant predictors of pain improvement, nor did they mitigate the effect of psychopathology on the outcome.
Conclusion: Psychiatric comorbidity is associated with diminished pain relief after a MBB injection performed with steroid at one-month follow-up. These findings illustrate the importance of assessing comorbid psychopathology as part of a spine care evaluation.
Facet injections are among the most commonly performed non-surgical procedures in the United States for axial low back or neck pain, representing a range of techniques and indications. Published reviews of insurance claims data from the U.S. have been unable to determine the frequency by which each injection technique is used (intrarticular vs. MBB), whether they were performed for diagnostic or therapeutic purposes, or what medications were injected. It is likely that the entire spectrum of indications, techniques, and medications are used with significant frequency, although some have recommended that certain approaches are preferable. While there is heterogeneity in the manner in which they are being used, identification of predictive factors in order to help determine success from these injections as a treatment for back pain is needed.
There is little agreement on what factors predict a successful outcome from facet injections and much depends on how they are used: indication (diagnostic vs. therapeutic), method (intrarticular vs. MBB), or medications (anesthetic only vs. steroid). Low-volume intrarticular injections are more specific for diagnosing facet-mediated pain, while MBBs are more useful in treating a wider range of back or neck pain since they block other potential pain generators such as the multifidus muscle and the interspinales ligament. The diagnostic and therapeutic results have been comparable between the two techniques (intrarticular vs. MBB), and both are associated with significant rates of false positives and negatives. Some clinicians have used the results of these blocks in deciding whom to offer a radiofrequency lesioning (RFL) procedure, which may confer longer benefit. This has been reported in some controlled studies as an average of 50% pain reduction lasting 6 months. Since an RFL of the medial branch dorsal ramus nerve also denervates the medial third of the multifidus muscle, there is a rationale supporting the MBB method, either for therapeutic or prognostic reasons.
An initial controlled trial found little therapeutic efficacy at six weeks for facet injections with corticosteroid. But more recent systematic reviews conclude that there is moderate evidence for significant benefit with either the intrarticular or MBB facet block technique (at least 30% pain relief at 3 months, Level III evidence). In many of these reviewed studies injectate volumes of 1-2 mls were used, which then are likely to spread beyond the dorsal ramus nerve to adjacent structures. Thus, even though therapeutic MBBs with steroid are treatments that are not specific to the facet joint, they may be useful in helping patients with axial neck or back pain.
There is, however, great variability in the subjects' responses to MBBs. Few predictive factors for success have been noted consistently, except for positive SPECT bone scan findings of facet disease. While earlier studies suggest that response to facet injections could be predicted by patient history and physical examination, subsequent work has shown that neither history, physical exam, nor radiographic findings (CT, MRI, or X-ray) can predict pain relief.
Because symptoms and anatomic findings are poorly predictive of results, it is difficult for clinicians to appropriately select patients for MBB injections. Although MBBs would not be indicated for everyone with axial pain, overly stringent selection criteria for performing these injections would likely exclude many who might otherwise benefit from this treatment. Yet, subgroups of responders in pain treatment studies of clinic populations can be identified reliably utilizing prospective observational designs based on possible predictive factors and applying operational inclusion criteria. This suggests that in treatment studies of MBBs confounding factors such as the lack of a clear physical diagnosis and the lack of specificity of an MBB to block the facet joint can be mitigated. Further identification of appropriate selection criteria for a MBB would allow for improved predictability of outcome.
Psychiatric illness-most often marked by depression, anxiety, and personality pathology-has been shown to be a significant predictor of treatment outcome for chronic musculoskeletal pain, regardless of whether it occurs prior to or after developing chronic pain. Psychopathology afflicts 50-75% of clinic populations of chronic pain patients, and those with a combination of negative affective disorders (such as depression and anxiety, which often occur together) are prone to the worst outcomes. In an effort to examine the relationship between psychiatric comorbidity and the diagnostic use of facet injections, Manchikanti, et al., identified 100 chronic low back pain patients with and without somatization, who underwent intrarticular facet injections with local anesthetic only, using the double block method. They reported that the rate of immediate pain relief and positive response from two blocks was the same (42%) whether a somatization disorder was present or not. However, the non-somatizers also had significant rates of major depression and generalized anxiety disorder, and 78% of the entire study population had at least one major psychiatric disorder. Also, the patients were only assessed for immediate pain relief after the procedure and were not followed. Furthermore, conscious sedation was used for the procedures, which the authors have reported to be a significant confounder of positive and negative responses. Thus, while the Manchikanti et al., study reported little relationship between psychopathology and outcome from diagnostic facet injections, there were confounding factors in the study design that made the results difficult to interpret and therapeutic benefit was not studied.
In sum, psychiatric comorbidity is a negative predictor of treatment outcome in general for chronic musculoskeletal pain and the relationship between facet injection results and psychiatric illness is still unclear. The aim of this study was to evaluate whether psychiatric comorbidity predicted the outcomes of MBBs for patients with axial back or neck pain. We hypothesized that patients with high levels of depression and anxiety symptoms would have a diminished response to a therapeutic MBB compared with those with little psychiatric comorbidity.
Abstract and Background
Abstract
Background: Comorbid psychopathology is an important predictor of poor outcome for many types of treatments for back or neck pain. But it is unknown if this applies to the results of medial branch blocks (MBBs) for chronic low back or neck pain, which involves injecting the medial branch of the dorsal ramus nerves that innervate the facet joints. The objective of this study was to determine whether high levels of psychopathology are predictive of pain relief after MBB injections in the lumbar or cervical spine.
Methods: This was a prospective cohort study. Consecutive patients in a pain medicine practice undergoing MBBs of the lumbar or cervical facets with corticosteroids were recruited to participate. Subjects were selected for a MBB based on operationalized selection criteria and the procedure was performed in a standardized manner. Subjects completed the Brief Pain Inventory (BPI) and the Hospital Anxiety and Depression Scale (HADS) just prior to the procedure and at one-month follow up. Scores on the HADS classified the subjects into three groups based on psychiatric symptoms, which formed the primary predictor variable: Low, Moderate, or High levels of psychopathology. The primary outcome measure was the percent improvement in average daily pain rating one-month following an injection. Analysis of variance and chi-square were used to analyze the analgesia and functional rating differences between groups, and to perform a responder analysis.
Results: Eighty six (86) subjects completed the study. The Low psychopathology group (n = 37) reported a mean of 23% improvement in pain at one-month while the High psychopathology group (n = 29) reported a mean worsening of -5.8% in pain (p < .001). Forty five percent (45%) of the Low group had at least 30% improvement in pain versus 10% in the High group (p < .001). Using an analysis of covariance, no baseline demographic, social, or medical variables were significant predictors of pain improvement, nor did they mitigate the effect of psychopathology on the outcome.
Conclusion: Psychiatric comorbidity is associated with diminished pain relief after a MBB injection performed with steroid at one-month follow-up. These findings illustrate the importance of assessing comorbid psychopathology as part of a spine care evaluation.
Background
Facet injections are among the most commonly performed non-surgical procedures in the United States for axial low back or neck pain, representing a range of techniques and indications. Published reviews of insurance claims data from the U.S. have been unable to determine the frequency by which each injection technique is used (intrarticular vs. MBB), whether they were performed for diagnostic or therapeutic purposes, or what medications were injected. It is likely that the entire spectrum of indications, techniques, and medications are used with significant frequency, although some have recommended that certain approaches are preferable. While there is heterogeneity in the manner in which they are being used, identification of predictive factors in order to help determine success from these injections as a treatment for back pain is needed.
There is little agreement on what factors predict a successful outcome from facet injections and much depends on how they are used: indication (diagnostic vs. therapeutic), method (intrarticular vs. MBB), or medications (anesthetic only vs. steroid). Low-volume intrarticular injections are more specific for diagnosing facet-mediated pain, while MBBs are more useful in treating a wider range of back or neck pain since they block other potential pain generators such as the multifidus muscle and the interspinales ligament. The diagnostic and therapeutic results have been comparable between the two techniques (intrarticular vs. MBB), and both are associated with significant rates of false positives and negatives. Some clinicians have used the results of these blocks in deciding whom to offer a radiofrequency lesioning (RFL) procedure, which may confer longer benefit. This has been reported in some controlled studies as an average of 50% pain reduction lasting 6 months. Since an RFL of the medial branch dorsal ramus nerve also denervates the medial third of the multifidus muscle, there is a rationale supporting the MBB method, either for therapeutic or prognostic reasons.
An initial controlled trial found little therapeutic efficacy at six weeks for facet injections with corticosteroid. But more recent systematic reviews conclude that there is moderate evidence for significant benefit with either the intrarticular or MBB facet block technique (at least 30% pain relief at 3 months, Level III evidence). In many of these reviewed studies injectate volumes of 1-2 mls were used, which then are likely to spread beyond the dorsal ramus nerve to adjacent structures. Thus, even though therapeutic MBBs with steroid are treatments that are not specific to the facet joint, they may be useful in helping patients with axial neck or back pain.
There is, however, great variability in the subjects' responses to MBBs. Few predictive factors for success have been noted consistently, except for positive SPECT bone scan findings of facet disease. While earlier studies suggest that response to facet injections could be predicted by patient history and physical examination, subsequent work has shown that neither history, physical exam, nor radiographic findings (CT, MRI, or X-ray) can predict pain relief.
Because symptoms and anatomic findings are poorly predictive of results, it is difficult for clinicians to appropriately select patients for MBB injections. Although MBBs would not be indicated for everyone with axial pain, overly stringent selection criteria for performing these injections would likely exclude many who might otherwise benefit from this treatment. Yet, subgroups of responders in pain treatment studies of clinic populations can be identified reliably utilizing prospective observational designs based on possible predictive factors and applying operational inclusion criteria. This suggests that in treatment studies of MBBs confounding factors such as the lack of a clear physical diagnosis and the lack of specificity of an MBB to block the facet joint can be mitigated. Further identification of appropriate selection criteria for a MBB would allow for improved predictability of outcome.
Psychiatric illness-most often marked by depression, anxiety, and personality pathology-has been shown to be a significant predictor of treatment outcome for chronic musculoskeletal pain, regardless of whether it occurs prior to or after developing chronic pain. Psychopathology afflicts 50-75% of clinic populations of chronic pain patients, and those with a combination of negative affective disorders (such as depression and anxiety, which often occur together) are prone to the worst outcomes. In an effort to examine the relationship between psychiatric comorbidity and the diagnostic use of facet injections, Manchikanti, et al., identified 100 chronic low back pain patients with and without somatization, who underwent intrarticular facet injections with local anesthetic only, using the double block method. They reported that the rate of immediate pain relief and positive response from two blocks was the same (42%) whether a somatization disorder was present or not. However, the non-somatizers also had significant rates of major depression and generalized anxiety disorder, and 78% of the entire study population had at least one major psychiatric disorder. Also, the patients were only assessed for immediate pain relief after the procedure and were not followed. Furthermore, conscious sedation was used for the procedures, which the authors have reported to be a significant confounder of positive and negative responses. Thus, while the Manchikanti et al., study reported little relationship between psychopathology and outcome from diagnostic facet injections, there were confounding factors in the study design that made the results difficult to interpret and therapeutic benefit was not studied.
In sum, psychiatric comorbidity is a negative predictor of treatment outcome in general for chronic musculoskeletal pain and the relationship between facet injection results and psychiatric illness is still unclear. The aim of this study was to evaluate whether psychiatric comorbidity predicted the outcomes of MBBs for patients with axial back or neck pain. We hypothesized that patients with high levels of depression and anxiety symptoms would have a diminished response to a therapeutic MBB compared with those with little psychiatric comorbidity.
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