Procedure guidance

The accuracy of these injections has been shown to be quite low when using only anatomic landmark guidance without the assistance of any type of image guidance. A variety of image guidance options have been used to ensure accurate needle placement, including fluoroscopy, ultrasound, and computed tomography (CT scans). Fluoroscopic guidance for spine procedures has a few specific benefits, one being the ability to visualize contrast flow in “real time” to help avoid an intravascular injection or otherwise unwanted location for the needle tip as it is being directed to the target location. Second, the confirmation of the needle in the intra-articular space can be accomplished under fluoroscopy by use of a small amount of contrast. Ultrasound guidance and CT guidance have also been used. These procedures confirm an intra-articular injection by guiding the bevel deep to the capsule in the case of diarthrodial joints; however, the major pitfall of using these forms of guidance is the inability to visualize vascular flow of an injection. Without image guidance, the procedure cannot specifically be labeled an SIJ or z-joint injection.

As evidenced by this issue of Physical Medicine and Rehabilitation Clinics of North America, there are a large number of potential pain generators in the lumbar spine. Needle localization becomes important as we seek to be clear and communicate the exact procedure we are performing. For instance, is it the intra-articular SIJ that was injected, the posterior ligamentous structures, or both? It becomes imperative to correctly identify the primary pain generator to target an intervention. This is all despite the poor correlation between accuracy and efficacy in corticosteroid injections. The literature is profuse with studies on nonspecific low-back pain. The addition of nonspecific (nonguided) treatments to the mix does not improve our clinical acumen. Algorithms have been proposed for the diagnosis and treatment of back pain, but fail to recognize the subtle and varied individual differences in patients, and generally poor treatment effect of many of these procedures. Subgrouping patients by clinical characteristics, physical examination maneuvers, imaging studies, and possibly diagnostic blocks can help to correctly identify a treatment subgroup. This is particularly the case when a specific joint may be targeted, as in a therapeutic injection as an adjunct to a comprehensive treatment plan.

The sacroiliac joint

The SIJ is a diarthrodial joint that receives innervation from the lumbosacral nerve roots and has demonstrated nociceptive and proprioceptive afferent units. It is an established potential source of buttock pain with or without lower extremity pain. Pain-referral patterns have been established based on provocation and analgesic response with a local anesthetic in both asymptomatic volunteers and patients with pain.

There is currently no accepted gold standard for the diagnosis of SIJ-mediated pain on either clinical examination or interventional procedure. Similar to most joint disorders, imaging studies collectively have had limited utility and poor correlation with symptoms. The lone exception is the bone scan, which has demonstrated a high specificity but low sensitivity for sacroiliitis.

Studies evaluating physical examination provocative maneuvers have had mixed results when compared with image-guided intra-articular injection of local anesthetic. Using greater than 90% pain relief with this procedure, Dreyfuss and colleagues demonstrated the single most sensitive physical examination maneuver was point of maximal pain over the sacral sulcus with a sensitivity of 60%. Later studies have shown increased sensitivity and specificity with a combination of physical examination maneuvers, but still less than those diagnosed with an intra-articular injection of a local anesthetic.

Because the historical features, physical examination, and imaging often leave the diagnosis in doubt, some have taken to using image-guided, intra-articular injection of anesthetics to further aide in the diagnosis. There have been multiple studies on the use of a single diagnostic injection, and the false positive range being 20% to 54% for uncontrolled single blocks. This has further led to the use of dual diagnostic injections with either a placebo or comparative local anesthetics with differing duration of action to confirm SIJ pain. Collectively, these studies demonstrate the level of evidence of diagnostic SIJ injections to be moderate, but higher than provocative physical examination maneuvers. Using controlled, comparative diagnostic injections, the prevalence of SIJ pain has been demonstrated at 10% to 27%. Because there is no collectively agreed on gold standard diagnostic test for SIJ-mediated pain, a combination of multiple physical examination maneuvers and controlled local anesthetic instillation may currently be the best tools available to identify the SIJ as the primary pain generator.

When reviewing the literature on intra-articular corticosteroids, the lack of a gold standard for the diagnosis of SIJ-mediated pain and the requirement of image guidance must both be taken into consideration. To date, there have been only 4 randomized controlled trials and 14 observational reports on the efficacy of intra-articular steroid injections into the SIJ. The recurring issue with most of these studies is the appropriate selection of patients. Selection criteria are frequently made on historical features and physical examination only, and occasionally with a single diagnostic block. Despite this lack of rigor in patient selection, lasting improvements in pain, disability, and work status have been demonstrated in therapeutic SIJ corticosteroid injections in those who had pain relief following a single diagnostic anesthetic injection into the SIJ.

Studies have also primarily evaluated patients with spondyloarthropathy, and most had follow-up that did not extend beyond 6 months. These studies demonstrate a positive effect of corticosteroid injections in those with SIJ-mediated pain in spondyloarthropathy; however, the literature is less clear in those without spondyloarthropathy. In addition, if strict criteria are set for the requirement of comparative blocks in combination with provocative physical examination maneuvers, none of the studies to date are sufficient. This lack of robust literature has led some to state there is no evidence supporting or refuting the use of therapeutic intra-articular injections of corticosteorids for SIJ-mediated pain.

Another controversial issue concerning the SIJ is the potential discrepancy between the location of the pain and the location of the injection. The joint space is thought to have ventral and dorsal innervation; additionally, the pain may be coming from the synovial joint itself versus periarticular soft tissues, specifically the ligaments. There are multiple ligamentous connections surrounding the SIJ, including the sacroiliac, sacrotuberous, and sacrospinal ligaments, which may contribute to pain. One double-blind, controlled study comparing periarticular corticosteroid injections with saline and lidocaine in those with and without spondyloarthropathy demonstrated significant short-term pain relief. Another study using ultrasound guidance demonstrated positive outcomes with both intra-articular and periarticular corticosteroid injections, without any statistically significant difference between groups at 4 weeks. Although the use of periarticular injections may be a cost-effective and safe alternative, the nonguided injection should be considered a soft tissue injection because of the inability to confirm presence of the injectate or needle in the intra-articular space.

The sacroiliac joint

The SIJ is a diarthrodial joint that receives innervation from the lumbosacral nerve roots and has demonstrated nociceptive and proprioceptive afferent units. It is an established potential source of buttock pain with or without lower extremity pain. Pain-referral patterns have been established based on provocation and analgesic response with a local anesthetic in both asymptomatic volunteers and patients with pain.

There is currently no accepted gold standard for the diagnosis of SIJ-mediated pain on either clinical examination or interventional procedure. Similar to most joint disorders, imaging studies collectively have had limited utility and poor correlation with symptoms. The lone exception is the bone scan, which has demonstrated a high specificity but low sensitivity for sacroiliitis.

Studies evaluating physical examination provocative maneuvers have had mixed results when compared with image-guided intra-articular injection of local anesthetic. Using greater than 90% pain relief with this procedure, Dreyfuss and colleagues demonstrated the single most sensitive physical examination maneuver was point of maximal pain over the sacral sulcus with a sensitivity of 60%. Later studies have shown increased sensitivity and specificity with a combination of physical examination maneuvers, but still less than those diagnosed with an intra-articular injection of a local anesthetic.

Because the historical features, physical examination, and imaging often leave the diagnosis in doubt, some have taken to using image-guided, intra-articular injection of anesthetics to further aide in the diagnosis. There have been multiple studies on the use of a single diagnostic injection, and the false positive range being 20% to 54% for uncontrolled single blocks. This has further led to the use of dual diagnostic injections with either a placebo or comparative local anesthetics with differing duration of action to confirm SIJ pain. Collectively, these studies demonstrate the level of evidence of diagnostic SIJ injections to be moderate, but higher than provocative physical examination maneuvers. Using controlled, comparative diagnostic injections, the prevalence of SIJ pain has been demonstrated at 10% to 27%. Because there is no collectively agreed on gold standard diagnostic test for SIJ-mediated pain, a combination of multiple physical examination maneuvers and controlled local anesthetic instillation may currently be the best tools available to identify the SIJ as the primary pain generator.

When reviewing the literature on intra-articular corticosteroids, the lack of a gold standard for the diagnosis of SIJ-mediated pain and the requirement of image guidance must both be taken into consideration. To date, there have been only 4 randomized controlled trials and 14 observational reports on the efficacy of intra-articular steroid injections into the SIJ. The recurring issue with most of these studies is the appropriate selection of patients. Selection criteria are frequently made on historical features and physical examination only, and occasionally with a single diagnostic block. Despite this lack of rigor in patient selection, lasting improvements in pain, disability, and work status have been demonstrated in therapeutic SIJ corticosteroid injections in those who had pain relief following a single diagnostic anesthetic injection into the SIJ.

Studies have also primarily evaluated patients with spondyloarthropathy, and most had follow-up that did not extend beyond 6 months. These studies demonstrate a positive effect of corticosteroid injections in those with SIJ-mediated pain in spondyloarthropathy; however, the literature is less clear in those without spondyloarthropathy. In addition, if strict criteria are set for the requirement of comparative blocks in combination with provocative physical examination maneuvers, none of the studies to date are sufficient. This lack of robust literature has led some to state there is no evidence supporting or refuting the use of therapeutic intra-articular injections of corticosteorids for SIJ-mediated pain.

Another controversial issue concerning the SIJ is the potential discrepancy between the location of the pain and the location of the injection. The joint space is thought to have ventral and dorsal innervation; additionally, the pain may be coming from the synovial joint itself versus periarticular soft tissues, specifically the ligaments. There are multiple ligamentous connections surrounding the SIJ, including the sacroiliac, sacrotuberous, and sacrospinal ligaments, which may contribute to pain. One double-blind, controlled study comparing periarticular corticosteroid injections with saline and lidocaine in those with and without spondyloarthropathy demonstrated significant short-term pain relief. Another study using ultrasound guidance demonstrated positive outcomes with both intra-articular and periarticular corticosteroid injections, without any statistically significant difference between groups at 4 weeks. Although the use of periarticular injections may be a cost-effective and safe alternative, the nonguided injection should be considered a soft tissue injection because of the inability to confirm presence of the injectate or needle in the intra-articular space.