Making Sense of the Accuracy of Diagnostic Lumbar Facet Joint Nerve Blocks: An Assessment of the Implications of 50% Relief, 80% Relief, Single Block, or Controlled Diagnostic Blocks

Abstract

Background: The presence of lumbar facet joint pain has been overwhelmingly supported and the accuracy of controlled diagnostic blocks has been demonstrated in multiple studies and confirmed in systematic reviews. However, controversy surrounds the following related issues: placebo control, the amount of relief (50% versus 80%), single block versus double block, and placebo or comparative control. Study Design: An observational report of an outcome study to establish the diagnostic accuracy of controlled lumbar facet joint nerve blocks. Setting: An interventional pain management practice setting in the United States. Objective: To determine the accuracy of controlled diagnostic blocks in managing lumbar facet joint pain at the end of 2 years, with 2 different criteria (50% or 80% relief) and single block versus double block. Methods: A previous study of 152 patients showed an 89.5% of sustained diagnosis of lumbar facet joint pain at the end of a 2-year follow-up period when the diagnosis was made with double blocks and at least 80% relief. The present evaluation includes comparison of the above results with a study of 110 patients undergoing lumbar facet joint nerve blocks with positive criteria of at least 50% relief and follow-up of 2 years. The inclusion criteria in both studies was based on a positive response to diagnostic controlled comparative local anesthetic lumbar facet joint blocks, with either 50% or 80% relief and the ability to perform previously painful movements. The treatment in both groups included therapeutic lumbar facet joint interventions either with facet joint nerve blocks or radiofrequency neurotomy. Outcome Measures: The sustained diagnosis of lumbar facet joint pain at the end of one year and 2 years based on pain relief and functional status improvement. Results: At the end of one year, the diagnosis was confirmed in 75% of the group with 50% relief, whereas it was 93% in the group with 80% relief. At the end of the 2-year follow-up, the diagnosis of lumbar facet joint pain was sustained in 51% of the patients in the group with 50% relief, whereas it was sustained in 89.5% of the patients with 80% relief. The results differed between 50% relief and 80% relief with prevalence of 61% facet joint pain with dual blocks with 50% relief, and 31% with dual blocks with 80% relief; whereas with only a single block, the prevalence was 73% with 50% relief and 53% in the 80% relief group. Limitations: The study is limited by its observational nature. Conclusion: Controlled diagnostic lumbar facet joint nerve blocks are valid utilizing the criteria of 80% pain relief and the ability to perform previously painful movements, with a sustained diagnosis of lumbar facet joint pain in at least 89.5% of the patients at the end of a 2-year follow-up. In contrast, the diagnosis was sustained in 51% of the patients with 50% relief at the end of 2 years. Thus, inappropriate diagnostic criteria will increase the prevalence of facet joint pain substantially, leading to inappropriate and unnecessary treatment. Key words: Chronic low back pain, lumbar facet or zygapophysial joint pain, facet joint nerve or medial branch blocks, controlled local anesthetic blocks, construct validity, diagnostic studies, diagnostic accuracy