Pain arising from the sacroiliac (SI) joint is common and difficult to distinguish from other causes of pain in the area of the lumbosacral junction. St joint dysfunction typically presents with localized pain in the lower back or upper buttock overlying the SI joint. Pain may be referred to the posterior thigh, but pain extending below the knee is unusual. In most cases, the etiology is unclear, and the onset is gradual over months to years. Trauma, infection, and tumor are uncommon causes of SI joint pain. The inflammatory arthropathies associated with ankylosing spondylitis, Reiter’s syndrome, and inflammatory bowel diseases are also infrequent but well-established causes of SI-related pain. Intra-articular injection of the SI joint with local anesthetic and steroid can provide short-term pain relief and assist diagnostically in establishing the source of low back pain. Radiofrequency treatments for SI-related pain have been devised but are only modestly effective in a fraction of treated patients. A long-term solution to SI-related pain is one of the needs unmet by our current armamentarium.

The SI joints are paired structures formed by the sacrum medially and the ilium of the pelvis laterally. The SI joints are the principal load-bearing structures that connect the vertebral elements of the spine with the pelvis and lower extremities. The majority of the connection between the sacrum and the ilium is in the form of a dense fibrocartilaginous connection, rather than a true synovial joint. The bulk of the true joint space is limited to the anterior portion of the apposing surfaces of the SI connection. There is a small portion of the synovial joint space that extends to the posterior- and inferior-most extent of the SI apposition, and it is from this point that access for intra-articular injection is gained. The superior extent of the SI joint lies anterior to the iliac crest, and the joint is difficult to access superior to the posterior-superior iliac spine (Fig. 8-1). The plane of the SI joint is variable from individual to individual; at the inferior extent of the joint where SI injection is carried out, the joint lies with 0 to 30 degrees of oblique angulation from the sagittal plane.

The sensory innervation to the SI joints is extensive, arising from branches of both the lumbar plexus anteriorly and the L5 dorsal ramus and S1 to S3 lateral branches posteriorly. Only the posterior aspect of the joint can be accessed with safety and ease percutaneously, and radiofrequency treatments have been devised to treat this portion of the SI joint.

Patients with SI-related pain are difficult to distinguish from those with other causes of axial spinal pain, tending to report pain location over the SI joints to either side of midline near the lumbosacral junction (Fig. 8-2). Physical examination may reveal localized tenderness over the joint, and Patrick’s test (or the Flexion, ABduction, External Rotation [FABER] test) may reproduce pain in the area of the SI joint positive (Table 8-1). Degenerative change of the joint on radiography is uncommon and nonspecific; most patients with SI-related pain have normal SI joint appearance on radiography. Resolution
of pain following intra-articular injection of local anesthetic under fluoroscopic or computed tomography (CT) guidance is the best diagnostic tool available. Similar to facet joint pain, definitive diagnosis is hindered by the significant placebo effect of diagnostic injection. Treatment for SI joint pain remains inadequate and controversial. Currently, periodic intra-articular injection of steroid with local anesthetics is the most common therapy for SI joint pain but typically provides only transient relief.

The available randomized controlled trials examining SI injections and radiofrequency treatment are limited. The American Pain Society (APS) Low Back Pain Guideline Panel published a report in 2009 and concluded that there was insufficient evidence to adequately evaluate the benefits of local anesthetic, corticosteroid injections, or radiofrequency treatment for the treatment of persistent nonradicular low back pain. Due to lack of available evidence, no recommendation for or against the use of SI joint injections was made by this group. Subsequently, the American Society of Anesthesiologists (ASA) Task Force on Chronic Pain Management published A 2010 Practice Guideline, offering the following recommendations: (1) “Sacroiliac joint injections may be considered for symptomatic relief of sacroiliac joint pain.”; and (2) “…water-cooled radiofrequency ablation may be used for chronic sacroiliac joint pain.”. Both groups highlight the limited evidence that is currently available to make any recommendations regarding the best means to diagnose and treat sacroiliac-related pain. In establishing the diagnosis, the features gleaned from the patient history overlap with the symptoms from a myriad of other causes for persistent nonradicular low back pain. Use of provocative maneuvers on physical examination is unreliable (Table 8-1). The gold standard for establishing the diagnosis has been pain relief with the intra-articular placement of local anesthetic, but this too is plagued by the large proportion of patients who report pain relief with the intra-articular injection of (saline) placebo. Thus, use of placebo-controlled, comparative injections is the only certain means to establish the diagnosis, and this is impractical in most clinical settings. Despite the limited evidence for long-term efficacy, the use of intra-articular SI joint injections using local anesthetic and corticosteroid remains commonplace. The use of radiofrequency treatment of the L5 dorsal ramus and the S1 to S3 lateral branches is still emerging. Detailed anatomic studies have recently appeared to guide accurate treatment and small controlled trials of water-cooled radiofrequency treatment suggest modest efficacy for this new approach.