Background: Chronic refractory spinal pain poses a peculiar diagnostic challenge because of multiple putative pain sources, overlapping clinical features, and nonspecific radiologic findings. Diagnostic injection techniques are employed to isolate the source(s) of pain. Facet or zygapophysial joint pain is an example of spinal pain diagnosed by local anesthetic injections of the facet joint or its nerve supply. Diagnostic facet joint injections are expected to meet the cardinal features of a diagnostic test (i.e., accuracy, safety and reproducibility). Accuracy must be compared with a "gold" or criterion standard that can confirm presence or absence of a disease. There is, however, no available gold standard, such as biopsy, to measure presence or absence of pain. Hence, there is a degree of uncertainty concerning the accuracy of diagnostic facet joint injections.
Objectives: To evaluate accuracy, safety and reproducibility of facet or zygapophysial joint injections in diagnosing chronic spinal pain of facet joint origin.
Study design: A systematic review of the literature for clinical studies on efficacy and utility of facet joint/nerve injections in diagnosing spinal pain from facet joints.
Methods: Relevant literature on diagnostic facet injections was identified through database searches. Excluded were abstracts, reviews, book chapters, case reports and studies based on single blocks or blocks without radiologic control. Prospective studies with placebo control, or controlled comparative local anesthetic blocks, were given priority over retrospective studies. Each study was graded using AHRQ and QUADAS criteria. The level of evidence was classified as conclusive, strong, moderate, limited, or inconclusive.
Results: Available literature pointed to strong evidence for controlled comparative local anesthetic facet joint medial branch blocks in the diagnosis of neck and low back pain. There was 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 joint nerves (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.