Low Back Pain and Diagnostic Lumbar Facet Joint Nerve Blocks: Assessment of Prevalence, FalsePositive Rates, and a Philosophical Paradigm Shift from an Acute to a Chronic Pain Model

Abstract

Background: Lumbar facet joints are a clinically important source of chronic low back pain. There have been extensive diagnostic accuracy studies, along with studies of influence on the diagnostic process, but most of them have utilized the acute pain model. One group of investigators have emphasized the importance of the chronic pain model and longer lasting relief with diagnostic blocks. Objective: To assess the diagnostic accuracy of lumbar facet joint nerve blocks with controlled comparative local anesthetic blocks and concordant pain relief with an updated assessment of the prevalence, false-positive rates, and a description of a philosophical paradigm shift from an acute to a chronic pain model. Study Design: Retrospective study to determine diagnostic accuracy, prevalence and falsepositive rates. Setting: A multidisciplinary, non-university based interventional pain management practice in the United States. Methods: Controlled comparative local anesthetic blocks were performed initially with 1% lidocaine, followed by 0.25% bupivacaine if appropriate response was obtained, in an operating room under fluoroscopic guidance utilizing 0.5 mL of lidocaine or bupivacaine at L3, L4 medial branches and L5 dorsal ramus. All patients non-responsive to lidocaine blocks were considered to be negative for facet joint pain. All patients were assessed after the diagnostic blocks were performed with ≥ 80% pain relief for their ability to perform previously painful movements. Results: The prevalence of lumbar facet joint pain in chronic low back pain was 34.1% (95% CI, 28.8%, 39.8%), with a false-positive rate of 49.8% (95% CI, 42.7%, 56.8%). This study also showed a single block prevalence rate of 67.9% (95% CI, 62.9%, 73.2%). Average duration of pain relief ≥ 80% was 6 days with lidocaine block and total relief of ≥ 50% of 32 days. With bupivacaine, the average duration of pain relief ≥ 80% was 13 days with total relief of ≥ 50% lasting for 55 days. Conclusion: This study demonstrated that the chronic pain model is more accurate and reliable with concordant pain relief. This updated assessment also showed prevalence and false-positive rates of 34.1% and 49.8%. Key words: Chronic spinal pain, lumbar facet or zygapophysial joint pain, facet joint nerve blocks, medial branch blocks, controlled comparative local anesthetic blocks, diagnostic accuracy, prevalence, false-positive rate