Sacroiliac Joint Syndrome
The pathologic conditions that affect the sacroiliac (SI) joint are myriad, including inflammatory, degenerative, traumatic, metabolic, infectious, neoplastic, and iatrogenic conditions, as well as sacroiliac joint syndrome. Sacroiliac joint dysfunction, or SI joint syndrome, is pain originating in the sacroiliac joint (SIJ) without a demonstrable anatomic lesion and presumed to be due to a biochemical abnormality. Predisposing factors include conditions that cause unusual stress on the joint such as spinal deformity, previous spinal surgery, and leg length discrepancy. Pathology and pain from surrounding structures, such as intervertebral disks and lumbar facet joints, can result in SI joint pain caused by postural changes with resulting increased stress on the SI joint. Pregnancy also predisposes to SI joint pain, which is thought to result from ligament laxity mediated by the hormone relaxin . Patients may report a history of minor trauma, such as lifting a heavy object while in a twisted position, or mis-stepping off a curb. The incidence of SI joint dysfunction in patients with back pain ranges from 15% to 30%.
Symptoms of SI joint dysfunction include pain in the superior medial quadrant of the buttock, the lateral buttock, and inferior to the posterosuperior iliac spine, with radiation to the greater trochanter, upper lateral thigh, and groin ( Fig. 63.1 ). Less commonly, the pain may radiate to the posterior thigh and leg below the knee. Two distinguishing features of the pain from SI joint dysfunction are the presence of groin pain and the absence of pain above the level of L5. In contrast to the pain distribution of SI joint dysfunction, the typical pattern of pain from facet joint syndrome includes the low back with radiation to the posterior thigh down to the knee, whereas the pain from a herniated disk usually extends to the leg and foot. Bending, sitting, and riding typically aggravate pain in sacroiliac joint dysfunction, and walking or standing relieves it.
Physical examination of the patient with SI joint syndrome usually reveals tenderness over the posterior aspect of the joint and the sacral sulcus. There are no neurologic symptoms such as numbness or weakness. There are several provocative maneuvers designed to stress the SI joint and elicit concordant pain, including the FABER (flexion, abduction, and external rotation)-Patrick’s test, Gaenslen’s test, Yeoman’s (extension) test, sacroiliac or posterior shear test, and Gillet’s test.
Faber-Patrick’s Test (Left Sacroiliac Joint Dysfunction) ( Fig. 63.2 )
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Figure 63.2
FABER-Patrick’s test.
(From Benzon HT. Pain originating from buttock: sacroiliac joint syndrome and piriformis syndrome. In: Benzon HT, Raja SN, Molloy RE, et al, eds. Essentials of Pain Medicine and Regional Anesthesia. 2nd ed. Philadelphia: Elsevier; 2005.)
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Left leg, near the ankle, is placed in front of the right thigh above the knee.
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The physician places one hand over the right iliac crest while the other hand pushes over the medial aspect of the left knee.
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Positive test: Pain over sacroiliac joint region (also back, buttock, groin).
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Comment: Test stresses sacroiliac and hip joint.
Gaenslen’s Test (Left Sacroiliac Joint Dysfunction) ( Fig. 63.3 )
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Figure 63.3
Gaenslen’s test.
(From Benzon HT. Pain originating from buttock: sacroiliac joint syndrome and piriformis syndrome. In: Benzon HT, Raja SN, Molloy RE, et al, eds. Essentials of Pain Medicine and Regional Anesthesia. 2nd ed. Philadelphia: Elsevier; 2005.)
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Left lower thigh and leg hang over the examination table.
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The examiner flexes right hip and right knee (i.e., hip joint is maximally flexed). The examiner presses downward over the left thigh (hip joint is hyperextended).
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Positive test: Pain in the left sacroiliac joint.
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Comments: Test stresses both sacroiliac joints simultaneously by counter-rotation at the extreme range of motion of the joint. Test also stresses the hip joint and stretches the femoral nerve (examiner should ensure the absence of hip pathology or conditions affecting the femoral nerve to diagnose sacroiliac joint syndrome).
Yeoman’s Test (Also Called Extension Test ( Fig. 63.4 )
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Figure 63.4
Yeoman’s test (also called the extension test).
(From Benzon HT. Pain originating from buttock: sacroiliac joint syndrome and piriformis syndrome. In: Benzon HT, Raja SN, Molloy RE, et al, eds. Essentials of Pain Medicine and Regional Anesthesia. 2nd ed. Philadelphia: Elsevier; 2005.)
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Examiner places one hand above the anterior aspect of the knee and elevates it slightly; the other hand presses downward over the crest of the ilium.
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Positive test: Pain over the posterior sacroiliac joint.
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Comments: The hip is extended and the ipsilateral ilium is rotated. Test stresses the sacroiliac joint; it also extends the lumbar spine and stresses the femoral nerve. More specific and reliable compared to the other tests.
Gillet’s Test ( Fig. 63.5 )
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Figure 63.5
Gillet’s test.
(From Benzon HT. Pain originating from buttock: sacroiliac joint syndrome and piriformis syndrome. In: Benzon HT, Raja SN, Molloy RE, et al, eds. Essentials of Pain Medicine and Regional Anesthesia. 2nd ed. Philadelphia: Elsevier; 2005.)
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One of the examiner’s thumbs is placed on the second sacral spinous process; the other thumb is placed on the posterior superior iliac spine (PSIS).
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Normal sacroiliac joint: When the patient maximally flexes the hip, the PSIS moves inferior to the S2 spinous process.
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Dysfunctional or fixed sacroiliac joint: PSIS remains at the level of the S2 spinous process or moves superior to the sacrum.
Sacroiliac Shear Test ( Fig. 63.6 )
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Figure 63.6
Sacroiliac shear test.
(From Benzon HT. Pain originating from buttock: sacroiliac joint syndrome and piriformis syndrome. In: Benzon HT, Raja SN, Molloy RE, et al, eds. Essentials of Pain Medicine and Regional Anesthesia. 2nd ed. Philadelphia: Elsevier; 2005.)
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Palm of the examiner’s hand is placed over the posterior iliac wing. Shear thrust is directed inferiorly, producing a shearing force across the sacroiliac joint.
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Positive test: Pain in dysfunctional sacroiliac joint.
Pain secondary to SI joint syndrome is difficult to isolate, making these tests neither highly sensitive nor specific. The FABER-Patrick’s test also stresses the hip joint, Gaenslen’s test stresses the hip joint and stretches the femoral nerve, and Gillet’s test can be difficult to perform. Although the Yeoman’s test stretches the femoral nerve and extends the lumbar spine, it appears to be a more specific and reliable maneuver. Some experts require the presence of three positive screening tests to confirm SI joint dysfunction.
The tests do not by themselves suggest the presence of SI joint dysfunction. Indeed, up to 2% of asymptomatic patients were found to have positive findings in one or more of these tests. Rather, the diagnosis of SI joint dysfunction is made based on the combination of history, symptoms, and physical examination findings. The maneuvers are of added value in confirming the diagnosis when the symptoms suggest SI joint syndrome and other causes of pain have been eliminated. The presence of tenderness over the sacral sulcus, pain over the SI joint, buttock pain, and the patient pointing to the posterior superior iliac spine as the main source of pain showed better sensitivity than the other tests evaluated.
Radiographic evaluation of the joint rarely aids diagnosis. Diagnostic local anesthetic block of the joint is considered to be the standard criterion for SI joint pain, although provocation of pain on injection of the SI joint is not a suitable criterion of SI joint dysfunction.
Anatomy
The sacroiliac (SI) joint is considered a diarthrodial joint because it contains synovial fluid, the articulating bones have ligamentous connections, the outer fibrous joint capsule has an inner synovial lining, and the cartilaginous surfaces allow motion to occur. The sacral side of the joint is thicker and made up of hyaline cartilage, whereas the iliac side is made up of thin fibrocartilage. The adult joint has irregular and coarse surfaces that increase with age, reflecting the stress to which the joint is exposed. The irregular contour of the joint contributes to its stability; the function of the joint is to transmit or dissipate the loading of the trunk to the lower extremities.
The ligaments of the SI joint include the anterior sacroiliac ligament, interosseous ligament, and posterior sacroiliac ligament ( Fig. 63.7 ). The anterior sacroiliac ligament traverses the ilium to the sacrum, and the posterior sacroiliac ligament traverses the posterior iliac ridge to the sacrum. The interosseous ligament is responsible for the stability of the joint. The sacrotuberous ligament, which is superficial to the posterior SI ligament, has multiple muscle attachments including the gluteus maximus, piriformis, and long head of the biceps femoris. These multiple muscle attachments provide stability during activities such as sitting, walking, and standing, which stress the sacroiliac joint. The sacroiliac joint is innervated at its anterior and posterior aspects. Its variable and extensive innervation accounts for the multiple presentations and variable referred pain patterns of sacroiliac joint pain. Posteriorly, the joint is innervated by the lateral branches of the posterior primary ramus of the L4 to S4 dorsal rami. The predominant innervation is from the dorsal ramus of S1, and there are isolated dorsal innervations from S1-4. The anterior innervation is from the ventral rami of the L5 to S2 and via branches from the sacral plexus. The blood supply of the joint is from the anastomosis between the median sacral artery and lateral sacral branches from the internal iliac artery.
Technique of Sacroiliac Joint Injection
For diagnostic injections, patients are asked to stop their pain medication on the day of the procedure. Sedation is usually not required but light sedation (1 to 2 mg intravenous midazolam) may be given in a nervous patient. Contraindications to the injection include infection in the area and bleeding diathesis. Allergy to contrast media may require pretreatment with H 1 and H 2 antagonists, whereas allergy to local anesthetics may require identification of the appropriate local anesthetic to be used for the procedure. The use of imaging is recommended during SI joint injection to ensure intra-articular needle placement, as blind injections rarely result in correct needle positioning.
Fluoroscopy-Guided Sacroiliac Joint Injection
The patient is positioned prone on the table, with the head turned to one side. A pillow is placed under the abdomen to flex the spine. Under a straight anteroposterior (AP) view, the SI joint presents several lines that course caudocranially in a semiparallel fashion. The lateral line represents the ventral or anterior margin of the joint, and the medial line represents the dorsal or posterior margin of the joint. The C-arm is initially rotated approximately 30 degrees caudal to the axial plane to better visualize the area underneath the posterior superior iliac spine and iliac crest. The C-arm is then angled obliquely to the contralateral side until the inferior joint space is clearly demarcated, usually between 5 and 20 degrees. The target point lies along the inferoposterior aspect of the joint, in the area 1 to 2 cm cephalad from its most caudal end.
The area is prepped and draped in the usual sterile fashion. The skin is anesthetized with 1 to 2 mL 1% lidocaine via a 25-gauge needle. A 22-gauge spinal needle is advanced coaxially toward the inferior pole of the sacroiliac joint with intermittent images obtained at regular intervals (every 2- to 4-mm advancement of the needle) to confirm trajectory. When the posterior surface of the sacroiliac joint is contacted, the needle is advanced to just penetrate the joint capsule. A change in resistance is commonly felt as the needle passes through the capsular tissue, and the needle tip is often deflected slightly as it traces the surface of the ilium. Some patients have significant osteoarthritic changes that preclude needle entry into the joint, making periarticular infiltration necessary. Once the needle is within the joint, a small amount of contrast is injected to demonstrate intra-articular spread ( Fig. 63.8 ). The response of the patient to the injection of contrast media is noted as either “no pain,” “unfamiliar pain,” or “similar pain” in comparison with the pain complaint. After appropriate contrast spread, a solution of steroid and local anesthetic (40 to 60 mg of methylprednisolone or triamcinolone with 1 to 2 mL of 0.5% bupivacaine or ropivacaine) is injected. Because the capacity of the sacroiliac joint is small and distension may exacerbate pain, a maximum volume of 2 to 2.5 mL has been recommended for SI joint injections. Spillage of injectate outside the SI joint is acceptable because some of the pain receptors are located outside the joint. Nociceptive fibers and receptors containing calcitonin gene-related peptide (CGRP) and substance P immunoreactive free nerve endings have been noted in the interosseous and anterior ligaments of the SI joint by Szadek and colleagues. In view of their findings, the authors recommended extra- as well as intra-articular approaches to diagnostic SI joint injection.
Other approaches include placement of the needle at the inferior end where the posterior and anterior joints overlap, if a markedly lucent zone is noted in that area. The midportion of the joint also can be cannulated. With 20 to 30 degrees of contralateral obliquity, the medial and lateral planes of the joint overlap. The needle entry is at the most lucent zone of the joint space; a 20- to 30-degree medial-to-lateral and 10- to 20-degree inferior direction of the needle approach has been recommended to gain entry into the midportion of the joint. Finally, the superior aspect of the joint can be accessed with a cephalocaudad approach.
Directly after the procedure the patient should be observed for 15 to 30 minutes to determine analgesic response and to monitor for complications. The local anesthetic has an immediate effect, but the anti-inflammatory effect of the steroid develops over 3 to 5 days. A greater than 75% reduction of pain over the SI joint is considered to be a positive response. Provocative maneuvers can be repeated to assess improvement. Transient weakness in the ipsilateral leg is due to spillage of local anesthetic onto the sacral nerve roots or the sciatic nerve. Other complications include bleeding, infection, exacerbation of pain, fever, transient difficulty voiding, and allergic reaction to components of the prep solution or injectate.
Ultrasound-Guided Sacroiliac Joint Injection
The feasibility of ultrasound-guided SI joint injections was initially shown by Pekkafahli and associates and was further described by Harmon and O’Sullivan. The patient is positioned prone with a pillow underneath the abdomen. A curvilinear low-frequency transducer (4 to 6 MHz) is placed perpendicular to the skin over the distal sacrum in the midline in a cross-sectional view (short axis) to identify the sacral hiatus. The probe is moved laterally until the lateral edge of the sacrum comes in view, then moved cephalad to find the medial aspect of the iliac bone. At this site the SIJ appears as a hypoechoic wedge-shaped structure ( Fig. 63.9 ). The target area for injection is at the level of the second sacral foramen, which is approximately 2 to 3 cm above the caudal pole of the SI joint. Lidocaine 1% is injected subcutaneously at the medial edge of the probe. A 22-gauge needle is inserted and advanced in-plane with a lateral and anterior trajectory into the joint. After the needle is deep to the iliac bone it is no longer visible on ultrasound. A pop is felt once the synovial joint is penetrated. Visible spread of injectate outside of the joint indicates periarticular rather than intra-articular placement.
The accuracy of this technique has been assessed. Pekkafahli and coworkers noted marked improvement with operator experience, from a 60% success rate in their first 30 injections to a 94% success rate in their second 30 injections. Klauser and colleagues evaluated ultrasound-guided SI joint injection in cadavers at two levels of the joint by comparing approaches at the level of the first sacral foramen versus those at the second sacral foramen. Computed tomography (CT) examination showed 90% of the needles at the lower level to be within the SIJ versus 70% in the upper level. The same procedure resulted in an intra-articular placement rate of 100% in both locations (eight in the lower and two in the upper site) when performed in live patients.
Computed Tomography–Guided Sacroiliac Joint Injection
Injection of the SI joint has been described under computed tomography (CT) guidance. The patient is positioned prone and the SI joint scanned. The best access point to the joint is determined and the gluteal injection point selected. The needle is inserted into the joint and steroid or local anesthetic is injected. Success rates from CT-guided injections range from 75% to 92%, with the duration of relief lasting 14 days to 10 months. The increased radiation exposure and lack of availability of CT in pain clinics restrict a wider application of this approach.
Efficacy of Sacroiliac Joint Injections
The efficacy of sacroiliac joint injections has been examined in studies, meta-analyses, and reviews with discordant results. Multiple uncontrolled studies indicate that corticosteroid SIJ injections are helpful. Liliang and colleagues reported a prospective observational study of 39 patients with SIJ pain confirmed by two diagnostic SIJ injections. Triamcinolone injection into the SI joint resulted in 67% of the patients having significant pain reduction for an average of 37 weeks ( Table 63.1 ). Other studies also showed positive results in patients without spondyloarthropathies. Bollow and associates studied CT-guided SIJ corticosteroid injections in 66 patients with back pain and known spondyloarthropathies; 92% had significant relief (average visual analog scale [VAS] reduction of 5 points) for a mean duration of 10 months. Similarly, Braun and colleagues showed significant reduction in VAS score 5 months after CT-guided SIJ injection with triamcinolone in 25 of 30 patients with spondyloarthropathies and low back pain. Fischer and coworkers performed corticosteroid SI joint injections in 56 children with spondyloarthropathy whose pain was unresponsive to nonsteroidal anti-inflammatory drugs (NSAIDs); 87.5% of the patients who received injections had an improvement in pain scores that lasted 12 ± 6 months.
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