Intra-Articular Injection of the Sacroiliac Joint

Indications and Clinical Considerations

The sacroiliac joint is susceptible to developing arthritis from a variety of conditions that all have the ability to damage the joint cartilage. The sacroiliac joint also is susceptible to developing strain from trauma or misuse. Osteoarthritis of the joint is the most common form of arthritis that results in sacroiliac joint pain. However, rheumatoid arthritis and posttraumatic arthritis are also common causes of sacroiliac pain secondary to arthritis ( Fig. 132.1 ). Less common causes of arthritis-induced sacroiliac pain include the collagen vascular diseases, including ankylosing spondylitis, infection, and Lyme disease. Acute infectious arthritis usually is accompanied by significant systemic symptoms, including fever and malaise, and should be easily recognized by the astute clinician and treated appropriately with culture and antibiotics rather than injection therapy. The collagen vascular diseases generally manifest as a polyarthropathy rather than a monoarthropathy limited to the sacroiliac joint, although sacroiliac pain secondary to ankylosing spondylitis responds exceedingly well to the intra-articular injection technique described later. Occasionally, the clinician encounters patients with iatrogenically induced sacroiliac joint dysfunction caused by overaggressive bone graft harvesting for spinal fusions.

The majority of patients with sacroiliac pain secondary to strain or arthritis report pain localized around the sacroiliac joint and upper leg. The pain of sacroiliac joint strain or arthritis radiates into the posterior buttocks and the back of the legs. The pain does not radiate below the knees. Activity makes the pain worse; rest and heat provide some relief. The pain is constant and characterized as aching and may interfere with sleep. On physical examination, there is tenderness to palpation of the affected sacroiliac joint. The patient often favors the affected leg and exhibits a list to the unaffected side. Spasm of the lumbar paraspinal musculature often is present, as well as limitation of range of motion of the lumbar spine in the erect position that improves in the sitting position because of relaxation of the hamstring muscles. Patients with pain emanating from the sacroiliac joint exhibit a positive pelvic rock test. The pelvic rock test is performed by placing the hands on the iliac crests and the thumbs on the anterior superior iliac spine and then forcibly compressing the pelvis toward the midline ( Fig. 132.2 ). A positive test is indicated by the production of pain around the sacroiliac joint.

Plain radiographs are indicated for all patients with sacroiliac pain. On the basis of the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, sedimentation rate, human leukocyte antigen B27 testing, and antinuclear antibody testing.

Clinically Relevant Anatomy

The sacroiliac joint is formed by the articular surfaces of the sacrum and iliac bones ( Fig. 132.3 ). These articular surfaces have corresponding elevations and depressions, which give the joints their irregular appearance on radiographs ( Fig. 132.4 ). The strength of the sacroiliac joint comes primarily from the posterior and interosseous ligaments rather than from the bony articulations ( Fig. 132.5 ). The sacroiliac joints bear the weight of the trunk and are therefore subject to the development of strain and arthritis. As the joint ages, the intra-articular space narrows, making intra-articular injection more challenging. The ligaments and the sacroiliac joint itself receive their innervation from L3 to S3 nerve roots, with L4 and L5 providing the greatest contribution to the innervation of the joint. This diverse innervation may explain the ill-defined nature of sacroiliac pain. The sacroiliac joint has a very limited range of motion, and that motion is induced by changes in the forces placed on the joint by shifts in posture and joint loading.