The Ability of Diagnostic Spinal Injections to Predict Surgical Outcomes

Abstract

Since their first description more than 80 yr ago, the use of diagnostic spinal injections to predict surgical outcomes has been the subject of intense controversy. Because there are no standardized guidelines or substantive reviews on this topic, their use has remained inconsistent. Diagnostic procedures included in this review were lumbar and cervical discography, lumbar facet blocks, lumbar and cervical selective nerve root blocks, and sacroiliac (SI) joint injections. We garnered materials via MEDLINE and OVID search engines, books and book chapters, bibliographic references, and conference proceedings. The lack of randomized, comparative studies for all blocks limited the conclusions that could be drawn. For the data that do exist, there is limited evidence that lumbar discography improves fusion outcomes, and no evidence that it influences disk replacement results. Although limited in scope, the current literature supports the notion that cervical discography improves surgical outcomes. There is strong evidence that lumbar selective nerve root blocks improve the identification of a symptomatic nerve root(s), and moderate evidence that both lumbar and cervical nerve root blocks improve surgical outcomes. The data supporting surgery for facet arthropathy are weak, and the use of screening blocks does not appear to improve outcomes. The data supporting SI joint fusion for degenerative, nontraumatic injuries are similarly weak. Because the most reliable method to diagnose a painful SI joint is with low volume, diagnostic injections, one might reasonably conclude that screening blocks improve surgical outcomes. However, this conclusion is not supported by indirect evidence. The ability to evaluate the effect of diagnostic blocks on surgical outcomes is limited by a lack of randomized studies, methodological flaws, and wide-ranging discrepancies with regard to injection variables, surgical technique, and outcome measures. More research is needed to optimize injection techniques and determine which, if any, diagnostic screening blocks can improve surgical outcomes.