Sacroiliac joint dysfunction is a common source of low back pain. In this chapter, a review of the relevant anatomy and frequent presenting symptoms associated with the dysfunction are presented. Additionally, a summary of the specific provocative maneuvers essential to the physical exam and the common functional limitations associated with this diagnosis are included. Finally, this chapter reviews the current literature regarding the various diagnostic tests, rehabilitation techniques, and interventional procedures used to treat this common pain generator.
KeywordsLow back pain, Radiofrequency ablation, Radiofrequency neurotomy, SIJ, Sacroiliac joint dysfunction, Sacroiliac joint pain, Sacroiliac ligaments
|S33.6||Sprain of sacroiliac joint or ligament|
|M53.3||Sacrococcygeal disorders, not elsewhere classified|
Although chronic low back pain is more commonly attributed to the lumbar intervertebral disc and the zygapophyseal joints, the sacroiliac joint (SIJ) remains a significant cause of low back and buttock pain. However, diagnosis and treatment of sacroiliac joint dysfunction (SIJD) are a clinical challenge. The diagnosis of sacroiliac dysfunction should be considered only after careful exclusion of many separate distinct pathologic entities. Sacral fractures, SIJ inflammation (such as is seen with various seronegative spondyloarthropathies), metastatic disease, and even infectious seeding of the SIJ are but a few known pathologic conditions that deserve investigation. Imaging studies are often unhelpful and nonspecific in SIJD. In addition, because of its redundant and variable innervation, SIJD can be manifested with a variable pain referral pattern. Thus, one must consider pathologic changes of neighboring structures sharing pain referral regions with the SIJ before deciding on the diagnosis of SIJD.
The prevalence of SIJD in those with low back pain complaints is thought to be between 10% and 25%, although during pregnancy the SIJ is the source of low back or posterior pelvic pain in 20% to 80% of cases. As such, SIJD may be more common in women than in men, and various studies demonstrate a female-to-male ratio of approximately 3:1 to 4:1. Although the most common cause of SIJD is idiopathic, a high percentage of SIJ pain has been found to be secondary to trauma, including motor vehicle accident, falls, and childbirth. Additionally, SIJ pain has been shown to occur following lumbar or lumbosacral fusion.
Adjoining the axial and appendicular skeleton, the SIJ occupies a critical biomechanical position ( Fig. 51.1 ). It is thought that joint dysfunction occurs with structural change to the joint or positional changes relative to the sacrum and pelvis. One can appreciate such changes in pregnancy-related instability or with joint misalignment in adolescents, both of which are known sources of SIJ pain and dysfunction. Pain associated with changes in position or the joint anatomy itself may be mediated by intra-articular, capsular, and ligamentous structures.
The SIJs are the bilateral weight-bearing joints that connect the articular surface of the sacrum with the ilium. The anterior and inferior third of the joint is synovial; the remainder of the joint space is syndesmotic. The SIJ is bordered on its ventral and superior edges by the ventral sacroiliac ligament and on its dorsal and inferior surfaces by the interosseous and dorsal sacroiliac ligaments. The articular capsule of the SIJ is thin and stabilized anteriorly by the ventral sacroiliac ligament. The strong extracapsular fibers of the dorsal sacroiliac and interosseous ligaments contribute principally to the stability of the joint. Further anchoring of the SIJ is conferred by the sacrotuberous and sacrospinous ligaments, which provide additional connections between the pelvis and sacrum.
Innervation of the SIJ remains an area of active study, and differing descriptions of SIJ innervation exist. Anatomic studies have described innervation primarily through dorsal rami of spinal nerve roots L5-S4. However, another study indicates that the SIJ either receives its innervation from the ventral rami of L4 and L5, the superior gluteal nerve, and the dorsal rami of L5, S1, and S2, or that it is almost exclusively derived from the sacral dorsal rami. Yet others suggest that dorsal innervation to the SIJ is from the L5 dorsal ramus and the S1-S3 lateral branches, whereas the ventral innervation derives from the ventral rami of L4 and L5.
The SIJ undergoes changes throughout life that affect the biomechanics of the joint. During childhood and adolescence, the joint is more mobile, absorbing forces throughout the gait cycle. With normal aging, the joints develop uneven opposing surfaces, and the joints are thought to gradually fuse in later years. Movements around the SIJs are small in magnitude yet complex in nature. As body weight is transmitted downward through the first sacral vertebra, the sacrum is pushed downward and forward, causing its inferior end to rotate upward and backward. Although there are no muscles that directly control movements around the joint, imbalance of the musculature surrounding the SIJ can affect stresses through the joint. Muscles anterior to the SIJ, including the psoas and iliacus, can influence movement of the sacrum. Weakness in posterior muscles, such as the gluteus maximus and medius, can affect pelvic posture during weight bearing, thereby altering stresses through the joint.
By far the most common presenting symptom of SIJD is low back and gluteal pain, which can be indolent and refractory to traditional interventions and therapies. Pain referral from SIJD is not limited to the lumbosacral region or buttocks, however. Because of the complex and extensive innervation of the SIJ as detailed before, dysfunction within the joint may be manifested with pain localizing to several rather removed regions, such as the thigh, groin, and leg. SIJD does not cause pain by neural compression, but because of the anatomic proximity of spinal nerve roots to the lumbar and sacral plexuses, pain referral patterns can mimic a variety of neurologic pathologic processes. In a retrospective study of 50 patients with positive diagnostic response to fluoroscopically guided SIJ injection, investigators sought to characterize the most common presenting symptoms experienced by the cohort. The most common symptoms were buttock pain (94%), lower lumbar pain (72%), and lower extremity pain (50%). Pain in the distal leg and pain in the foot were also reported, as was low abdominal pain and groin pain.
Activities said to aggravate the pain include prolonged standing, asymmetric weight bearing, and stair climbing. Pain can also stem from running, large strides, or extreme postures.
A thorough assessment of the low back, hips, and pelvis, including musculoskeletal and neurologic testing, is essential in isolating back pain caused by SIJD and to exclude other common diagnoses. Examination should include measurement of leg length and assessment of pelvic symmetry by inspection of the posterior superior iliac spine, anterior superior iliac spine, gluteal folds, pubic tubercles, ischial tuberosities, and medial malleoli. The sacral sulcus is palpated and inspected with the patient prone, and any muscle atrophy in the gluteal muscles or distal extremity is noted. Atrophy in the limb implicates a lumbar radiculopathy more than SIJ syndrome. Palpation of the bony sacrum, subcutaneous tissues, muscles, and ligaments also helps to complete the examination.
Provocative tests have long been used by clinicians to differentiate SIJ-derived back pain from other regional pain generators. However, repeated clinical studies have suggested that when they are considered separately, the most commonly used provocative tests have low specificity for sacroiliac dysfunction. One possible explanation for this is poor inter-rater reliability. Others suggest that both the minimal range of motion around the joints and the difficulty in simulating physiologic stresses through the joints make it more likely that provocative tests will elicit pain from surrounding structures. Such structures include the lumbar intervertebral disc, zygapophyseal joint, and hip joint. Several investigators have shown that in the diagnosis of SIJ disease, a multitest regimen is more clinically useful than any isolated finding. Studies suggest that three or more positive findings on provocative tests are 82% to 85% sensitive and 57% to 79% specific for SIJ disease. There is some evidence, in fact, that patients with low back pain who point to the posterior superior iliac spine or within 2 cm from this landmark are more likely to respond to periarticular SIJ blockade, thus making the patient’s ability to pinpoint the pain a potentially useful tool.
With the patient supine, lying close to the edge of the examination table with the buttock of the tested side over the edge of the table, the patient’s leg is dropped off the table such that the thigh and hip are in hyperextension. The contralateral knee is then maximally flexed. Pain or discomfort with this maneuver suggests SIJ disease, although a false-positive result can be seen in patients with an L2-L4 nerve root lesion, spondylolisthesis, sacral fractures, lumbar compression fractures, or spinal stenosis ( Fig. 51.2 ).
Patrick Test (Also Called Flexion, Abduction, External Rotation Test)
With the patient supine on a level surface, the thigh is flexed and the ankle placed above the patella of the opposite extended leg. Downward pressure is applied simultaneously to the flexed knee and the opposite anterior superior iliac spine as the ankle maintains its position above the knee. Pain or discomfort in the gluteal region reflects sacroiliac disease; pain in the groin or thigh may be suggestive of hip disease ( Fig. 51.3 ).
With the patient standing, the examiner palpates both the spinous process of the second sacral vertebra and the posterior superior iliac spine of the affected side. The patient is asked to maximally flex the hip on the involved side. A positive test result is indicated by a reproduction of pain and the failure of the palpated posterior superior iliac spine to move inferiorly in relation to the second sacral vertebra.
POSH Test (Posterior Shear Test)
With the patient supine, the examiner flexes the hip of the involved side to 90 degrees and adducts the thigh toward midline, providing axial pressure along the femur, directed into the table. This maneuver produces a shear force across the SIJ and reproduces pain in a symptomatic patient.
REAB Test (Resisted Abduction)
With the patient supine, the hip of the involved side is placed in 30 degrees of abduction with the knee extended. The patient is asked to provide an isometric abduction contraction while the examiner resists at the lateral ankle. Reproduction of pain in the region of the SIJ is a positive test result. The test is thought to stress the cephalad aspect of the joint.
Distraction Test (Also Called the Gapping Test)
With the patient supine, pressure is applied downward and laterally to the bilateral anterior superior iliac spines. This maneuver stretches the ventral sacroiliac ligaments and joint capsule while placing pressure on the dorsal sacroiliac ligaments.
With the patient lying in the lateral recumbent position, the examiner stands behind the patient and applies pressure downward on the uppermost iliac crest, compressing the pelvis. This stretches the dorsal sacroiliac ligaments and compresses the ventral sacroiliac ligaments.
With the patient positioned prone, the knee is flexed to approximately 90 degrees and the hip is extended by the examiner. The SIJ ipsilateral to the extended hip is being tested. Reproduction of familiar gluteal or pelvic pain is considered a positive test result ( Fig. 51.4 ).