SacroIliac Joint injection

The sacroiliac (SI) joint is the largest axial joint in the body. There is wide variability in the adult SI joint, encompassing size, shape, and surface contour. The SI joint is most often characterized as a large, auricular-shaped, diarthrodial synovial joint. In reality, only the anterior third of the interface between the sacrum and ilium is a true synovial joint; the rest of the junction is comprised of an intricate set of ligamentous connections. Because of an absent or rudimentary posterior capsule, the SI ligamentous structure is more extensive dorsally, functioning as a connecting band between the sacrum and ilia. The main function of this ligamentous system is to limit motion in all planes of movement. In women the ligaments are weaker, allowing the mobility necessary for parturition.

The SI joint is also supported by a network of muscles that transmit regional muscular forces to the pelvic bones. Some of these muscles, such as the gluteus maximus, piriformis and biceps femoris, are functionally connected to SI joint ligaments, so their actions can affect joint mobility.

Age-related changes in the SI joint begin in puberty and continue throughout life. During adolescence, the iliac surface becomes rougher, duller, and coated in some areas with fibrous plaques. These senescent changes accelerate during the third and fourth decades of life and are manifested by surface irregularities, crevice formation, fibrillation and the clumping of chondrocytes. In the sixth decade, motion at the joint may become markedly restricted as the capsule becomes increasingly collagenous and fibrous ankylosis occurs. By the eighth decade of life, erosions and plaque formation are inevitable and ubiquitous.

The innervation of the SI joint remains a subject of much debate. The lateral branches of the L4-S3 dorsal rami are cited by some experts as composing the major innervation to the posterior SI joint. The innervation of the anterior joint is similarly ambiguous.

Patients complain of pain in the lower back with radiation into the buttock, lower lumbar region, lower extremity, groin area, upper lumbar region and abdomen. Pain can rarely be radiated below the knee and in to the foot. Based on the existing data, the most consistent factor for identifying patients with SI joint pain is unilateral pain (unless both joints are affected) localized predominantly below the L5 spinous process.

Pain is frequently worse with standing and sitting down for prolonged periods. Pain is also exacerbated by turning in bed or lying on the affected side.

One of the most challenging aspects of treating SI joint pain is the complexity of diagnosis. Dozens of physical examination tests have been advocated as diagnostic aids in patients with presumed SI joint pain . Many involve distraction of the SI joints, with two of the most common ones being Patrick’s test and Gaenslen’s test. Neither medical history nor physical examination findings are consistently capable of identifying dysfunctional SI joints as pain generators.

Intra articular injection

Intra articular injections with local anaesthetic and steroid often serve the dual function of being diagnostic and therapeutic. Most investigators have found radiologically guided SI joint injections to provide good to excellent
pain relief lasting from 6 months to 1 year. Various studies have also shown a beneficial effect for peri articular corticosteroid treatment as well.

Botulinum toxin injection

Botulinum toxin injections have been used in management of SI joint pain. Both peri articular and intra articular botox injections have been reported.

Cooled radiofrequency treatment for SI joint pain

Cooled radiofrequency is a relatively new concept developed for conditions that are difficult to treat effectively using conventional radiofrequency treatment. Cooled radiofrequency utilises a special radiofrequency probe designed to produce a larger lesion size and therefore treat a larger area than is possible with conventional radiofrequency treatment.

There is some evidence that suggests that cooled RF treatment may be more efficacious in management of SI joint pain, compared to standard RF and intra articular injections, though more robust studies are needed to confirm this.

Injections are generally avoided in patients with systemic infection or skin infection over puncture site, bleeding disorders or coagulopathy, allergy to local anaesthetics or any of the medications to be administered. Radiofrequency treatment is contraindicated in patients with pacemakers or any other neural implants (spinal cord stimulator, deep brain stimulator).

The procedure is usually done on an outpatient basis. The procedure is performed under ultrasound or fluoroscopic guidance to ensure accuracy of needle placement. Patients need to be aware that the outcome of the procedure is variable and they may not receive the desired benefits. Similarly, they must be aware of the transient nature of the therapeutic benefits and that there may need repeated injections.

Generally a mixture of local anaesthetic and steroid is injected. The local anaesthetic agent within the injectate may act on the nociceptive fibres in the synovium, whereas intracapsular corticosteroids may reduce inflammation of the synovium. The anaesthetic is probably responsible for immediate pain relief, whereas steroids are believed to be responsible for pain relief 2–6 days after their administration. For a diagnostic block, a short-acting anaesthetic alone is sufficient.

Complications are rare, particularly if SI joint injections are performed using a precise needle-positioning technique. Severe allergic reactions to local anaesthetics are uncommon. Steroid injections may produce local reactions, occurring most often immediately after injection. These local reactions last for 24 to 48 hours, and are relieved by application of ice packs. Post-procedural pain flare-up may occasionally occur, and may be treated with pain killers. Neurological complications including paraesthesias, numbness and paralysis are extremely rare. Infection can occur but the incidence is very low as the procedure is performed under strict aseptic conditions.

The SI joint is a real yet underappreciated pain generator in an estimated 15% to 25% of patients with axial LBP. Whereas historical and physical examination findings have been previously advocated as useful tools in identifying patients with SI joint pain, more recent studies have demonstrated they have limited diagnostic value. Presently, small-volume diagnostic blocks remain the most commonly used method for diagnosing this disorder, although their validity remains unproven. Intra articular and peri articular corticosteroid injections have been shown in most, but not all, studies to provide good to excellent pain relief lasting up to 10 months in patients with and without spondylarthropathy. One promising area in the treatment of SI joint pain is RF denervation, although the conclusions that can be drawn are limited by the heterogeneous methods used and the lack of controlled studies.