Efficacy and Cost: Benefit Ratio of 0, 1, and 2 Medial Branch Blocks for Lumbar Facet Joint Radiofrequency Denervation

Overview

Lumbar zygapophysial (facet) joint pain is a common cause of low back pain. Radiofrequency (RF) denervation is an effective and low risk treatment of chronic low back pain of suspected facet joint etiology. Blocks of the medial branches innervating the joints are commonly used to localize the pain and make the diagnosis of facet joint pain. There is currently no standard number of diagnostic blocks: zero, one, and two blocks have all been utilized. Considering the high false positive and false negative rates of these blocks, the cost: benefit ratio has been questioned. No study to date has examined the practice of diagnostic medial branch blocks before RF denervation. The purpose of this study is to determine the optimal number of blocks before radiofrequency denervation. Three groups of patients will be studied. In group I, patients will undergo RF denervation based on history and physical exam alone. In group II, patients will undergo RF denervation based on a positive response to a single diagnostic block with local anesthetic. In group III, patients will undergo RF treatment only after a positive screening block and a positive confirmatory block.

Lumbar zygapophysial (facet) joints are recognized as one of the most common causes of chronic low back pain with an estimated prevalence among patients with LBP ranging from 15% to 40%. Radiofrequency (RF) denervation of facet joints has been utilized as an effective treatment of chronic pain attributed to these joints. Blocks of the medial branches innervating the joints are commonly used to localize the pain and make a diagnosis of lumbar zygapophysial (l-z) joint pain. However, considering the high false-positive rates of these blocks (25-40%), the false-negative rates (8-10%), and the number of blocks necessary to make the diagnosis before treatment, the cost-effectiveness of performing these blocks and the benefit of exposing these patients to additional risks is under question. The risks of RF denervation are so low (equivalent to performing the diagnostic block), some have questioned whether or not any diagnostic facet blocks should be performed before RF lesioning. The purpose of the study is to determine the optimal number of diagnostic blocks that should be performed before radiofrequency denervation in patients with chronic lower back pain with suspected facet joint etiology. In this prospective randomized study, we will recruit 150 patients with suspected chronic (l-z) joint pain without neurological symptoms to undergo one of three treatment modalities. In group I, 50 patients will undergo RF denervation based on history and physical exam alone (what we advocate in a recent review article). In group II, 50 patients will receive a single diagnostic block with 0.5% bupivacaine. Those that obtain greater than 50% pain reduction will undergo RF denervation. In group III, 50 patients will receive a block with either 2% lidocaine or 0.5% bupivacaine. Those patients that obtain greater than 50% pain relief with the first block receive a second block with the other local anesthetic. Patients that obtain greater than 50% pain relief with the second block then undergo RF. Patients in any group that obtain less than 50% pain relief with any block exit the study.