Systematic review of diagnostic utility of facet (zygapophysial) joint injections in chronic spinal pain: an update.

BACKGROUND A 2-year review of literature from October 2004 to December 2006 was completed to update current scientific evidence on diagnostic utility of facet joint injections. Diagnostic injections are employed to diagnose facet joint pain because available techniques cannot identify the pain generating structure in patients with chronic spinal pain. There is no physical examination technique, laboratory test, or imaging modality that can precisely identify the spinal structure causing pain, distinguish the culprit from a variety of potential targets, and predict response to a therapeutic intervention. Zygapophysial joint injections, commonly called facet injections (intraarticular joint injections and medial branch blocks) are local anesthetic injections of the facet joint or its nerve supply. These are diagnostic procedures used to determine if pain is arising from facet joints, distinguish painful from nonpainful joints and prognosticate response to therapeutic facet joint interventions. Diagnostic injections must meet the cardinal features of a diagnostic test i.e., accuracy, safety, and reproducibility. Accuracy is based on comparison with a "gold standard" to confirm presence or absence of a disease. There is, however, no available gold standard to measure presence or absence of pain. Hence, there is a degree of uncertainty concerning the accuracy of diagnostic facet joint injections. OBJECTIVES Evaluate and update available evidence (2004 to 2006) relating to clinical utility of facet joint injections (intraarticular and medial branch blocks) in diagnosing chronic spinal pain of facet joint origin. STUDY DESIGN Review of the literature for clinical studies on efficacy and utility of facet joint/nerve injections in diagnosing facet joint pain according to Agency for Healthcare Research and Quality (AHRQ) and Quality Assessment Studies of Diagnostic Accuracy (QUADAS) criteria. The level of evidence was classified as conclusive (Level I), strong (Level II), moderate (Level III), or limited (Level IV). METHODS Computerized database search (2004 to 2006) of PUBMED, EMBASE, CINAHL, and Web of Knowledge was conducted to identify studies on facet joint pain and diagnostic interventions. Abstracts, reviews, book chapters, case reports, studies based on single blocks or blocks without radiologic control, and studies describing techniques were excluded. Prospective studies were given priority over retrospective studies. RESULTS There is no change in the strength of evidence for facet joint diagnostic injections. There is strong evidence for controlled comparative local anesthetic facet joint injections or medial branch blocks in the diagnosis of neck and low back pain and moderate evidence in the diagnosis of pain arising from thoracic facet joints. CONCLUSION The evidence obtained from literature review suggests that controlled comparative local anesthetic blocks of facet joints (medial branch or dorsal ramus) are reproducible, reasonably accurate and safe. The sensitivity, specificity, false-positive rates, and predictive values of these diagnostic tests for neck and low back pain have been validated and reproduced in multiple studies.