Abstract
BackgroundComorbid 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.MethodsThis 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.ResultsEighty 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.ConclusionPsychiatric 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.
Highlights
Comorbid psychopathology is an important predictor of poor outcome for many types of treatments for back or neck pain
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[1] Published reviews of insurance claims data from the U.S have been unable to determine the frequency by which each injection technique is used, whether they were performed for diagnostic or therapeutic purposes, or what medications were injected[1,2] It is likely that the entire spectrum of indications, techniques, and medications are used with significant frequency, some have recommended that certain approaches are preferable[3] 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, method, or medications[4] Low-volume intrarticular injections are more specific for diagnosing facet-mediated pain, while medial branch blocks (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[5,6] The diagnostic and therapeutic results have been comparable between the two techniques,[7,8] and both are associated with significant rates of false positives and negatives[4] Some clinicians have used the results of these blocks in deciding whom to offer a radiofrequency lesioning (RFL) procedure, which may confer longer benefit
Summary
Comorbid psychopathology is an important predictor of poor outcome for many types of treatments for back or neck pain. 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)[4] 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[5,6] The diagnostic and therapeutic results have been comparable between the two techniques (intrarticular vs MBB),[7,8] and both are associated with significant rates of false positives and negatives[4] 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[9,10] Since an RFL of the medial branch dorsal ramus nerve denervates the medial third of the multifidus muscle[11], there is a rationale supporting the MBB method, either for therapeutic or prognostic reasons. There is, great variability in the subjects' responses to MBBs[13] Few predictive factors for success have been noted consistently, except for positive SPECT bone scan findings of facet disease[14] While earlier studies suggest that response to facet injections could be predicted by patient history and physical examination,[15,16] subsequent work has shown that neither history, physical exam, nor radiographic findings (CT, MRI, or X-ray) can predict pain relief[4,17,18,19,20,21]
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