Clinical StudyLumbar zygapophysial (facet) joint radiofrequency denervation success as a function of pain relief during diagnostic medial branch blocks: a multicenter analysis
Introduction
Lumbar zygapophysial (l-z) joint pain is a challenging condition affecting approximately 15% of patients with chronic, axial low back pain (LBP) [1]. One of the biggest challenges in managing l-z (facet) joint pain is the lack of any standard, reliable treatment. Until recently, radiofrequency (RF) denervation of the nerves innervating the l-z joints was widely considered to be the gold standard for treating lumbar facet arthropathy, having been shown to provide intermediate to long-term relief in patients who positively respond to diagnostic blocks [2], [3], [4]. However, the publication of three consecutive negative trials evaluating RF denervation for lumbar and cervical z-joint pain has cast doubts as to the efficacy of RF lesioning [5], [6], [7]. Whereas this has led some clinicians to question the concept of RF lesioning for z-joint pain, others have implicated flaws in technique and selection criteria as the likely causes for treatment failure [8], [9], [10], [11]. One variable yet to be examined for its relationship to RF treatment outcome is the pain relief cutoff for designating a diagnostic block as “positive.” Several authors have claimed that the identification of z-joints as pain generators is best accomplished only after complete or near-total relief of back pain after low-volume diagnostic injections [12], [13], [14], [15]. In addition to the logic behind this assertion, this claim seems to be borne out by an examination of prospective studies evaluating medial branch RF denervation. Among six prospective studies evaluating lumbar or cervical medial branch RF denervation that used near-total pain relief after diagnostic blocks as an inclusion criterion, all reported excellent outcomes [14], [15], [16], [17], [18], [19]. In similar studies using 50% pain relief as the threshold for lesioning, about half reported positive outcomes [3], [4], [5], [6], [7], [20]. Yet despite the surface validity of this comparison, any conclusions that can be drawn regarding the superiority of choosing a higher analgesic threshold for RF lesioning is limited by a plethora of confounding variables including a lack of direct comparison between outcomes based on the degree of pain relief experienced after diagnostic blocks, publication bias, variations in RF technique and other selection criteria, multiple publications by the same groups of authors, and the fact that most studies that used complete or near-complete pain relief as an inclusion criterion evaluated cervical (rather than lumbar) z-joint denervation. As a source of spinal pain, cervical z-joints have consistently been found to account for a higher percentage of chronic neck pain than lumbar z-joints do in LBP sufferers [1], [21], [22].
Perhaps most significant is that in almost all of the prospective studies using greater than or equal to 80% pain relief as a cutoff value, either placebo-controlled or comparative local anesthetic blocks were used to minimize the high false-positive rate of uncontrolled z-blocks, estimated at between 25% and 40% [23], [24], [25], [26]. In a busy clinical practice, the recommendation to use double blocks is often disregarded on the bases that the definitive RF neurotomy procedure carries a serious complication (eg, epidural abscess, meningitis) rate comparable to that of each diagnostic injection [1]; each diagnostic injection is associated with a small but quantifiable false-negative rate [27]; and the use of controlled diagnostic blocks is not cost effective [28]. This is the case in many academic pain clinics and military treatment facilities, including our own. Even in the positive studies whereby 50% pain relief was designated as the RF threshold, because no subgroup analyses were performed, it is possible that the beneficial effects were realized mostly in patients who obtained nearly complete pain relief from diagnostic blocks.
The question as to what the optimal cutoff should be before proceeding to RF lesioning is both clinically and academically relevant. To illustrate, withholding a definitive treatment from someone who experiences only partial pain relief from z-blocks but is nevertheless likely to benefit may potentially lead to misdiagnosis, increased disability, unnecessary interventions, and amplified costs. On the other hand, performing RF lesioning on patients who experience partial pain relief from diagnostic blocks and are consequently predisposed to treatment failure exposes them to unnecessary risks, wastes valuable resources, and threatens the viability of the RF denervation because it undermines the very concept of the procedure. To help determine the optimal pain threshold to guide treatment in patients being considered for RF denervation, we conducted a retrospective analysis of large, multicenter databases comparing outcomes between patients experiencing partial but significant pain relief (greater than or equal to 50% but less than 80%) after diagnostic medial branch blocks (MBB) and those who experience near-total relief (greater than or equal to 80%) after diagnostic injections.
Section snippets
Patients and methods
Permission to conduct this study was granted by the Internal Review Boards at three different institutions and all patients who provided informed consent for the procedures. The institutions participating in this study were Johns Hopkins Medical Institutions, Walter Reed Army Medical Center (WRAMC), and Massachusetts General Hospital. The data collected for this study were garnered from the medical records of 298 consecutive patients who underwent lumbar medial branch and L5 dorsal rami RF
Results
Data were analyzed on 262 patients. Morphometric, demographic, and clinical characteristics were somewhat heterogeneous among the three treatment centers. WRAMC patients were younger, more often male, and less likely to smoke cigarettes, use opioids, or have a BMI greater than 30. Massachusetts General Hospital patients had a higher incidence of paraspinal tenderness, “facet loading,” and pain radiation below the knee. Johns Hopkins Medical Institutions patients had a higher prevalence of
Discussion
The principal finding in this study is that the degree of pain relief obtained after diagnostic screening blocks does not correlate with l-z joint denervation outcomes. It suggests that using 50% pain relief as the benchmark for a positive diagnostic procedure, which based on the current literature is the most commonly used cutoff, leads to comparable success rates and superior overall outcomes (because it is more inclusive) than using more stringent criteria for identifying RF candidates.
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2018, Physical Medicine and Rehabilitation Clinics of North AmericaCitation Excerpt :Previous studies have shown no significant difference in terms of radiofrequency denervation outcomes between the 50% and 80% cutoff values. Local anesthetic blocks providing greater than 80% relief increase the number of true positives and screen out the false negatives and the patients who have multiple pain generators.1,11–13 A systematic review by Manchikanti and colleagues10 showed that the prevalence of the accuracy and reliability of diagnostic facet medial branch blocks in the low back was 27% to 41% with a false-positive rate of 25% to 44% and the prevalence for the cervical spine was 36% to 67% with a false-positive rate of 27% to 63%.
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The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or Department of Defense.
Funded in part by the John P. Murtha Neuroscience and Pain Institute, Johnstown, PA and the Army Regional Anesthesia & Pain Medicine Initiative, Washington, DC.