(Radiology. 2000;214:273-277.)
© RSNA, 2000
Fluoroscopy-guided Sacroiliac Joint Injections1
Robert G. Dussault, MD,
Phoebe A. Kaplan, MD and
Mark W. Anderson, MD
1 From the Department of Radiology, University of Virginia Health System, Lee St, Box 170, Charlottesville, VA 22908. Received November 19, 1998; revision requested December 21; final revision received April 16, 1999; accepted June 28 1999. Address reprint requests to R.G.D. (e-mail: rgd6q@virginia.edu).
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Abstract
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The authors performed fluoroscopy-guided sacroiliac (SI) joint injections. With the patient prone and the x-ray tube perpendicular to the fluoroscopic table, the skin was marked over the distal 1 cm of the SI joint. With the tube angled 20°–25° cephalad, a 22-gauge needle was inserted at the skin mark and advanced perpendicular to the fluoroscopic table toward the posterior joint. Nonionic contrast material was injected to confirm the intraarticular position of the needle. Of 31 SI joint injections, 30 (97%) were intraarticular. Mean procedure time was 108 seconds. This technique is safe, rapid, and reproducible.
Index terms: Joints, sacroiliac, 337.1269
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Introduction
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Low back pain of sacroiliac (SI) joint origin is a difficult clinical diagnosis and often one of exclusion. Patients usually have pain over the buttock that may extend to the lateral aspect of the hip and thigh (1). Pain arising from the SI joint may mimic pain originating from the lumbar disk, lumbar facet, or hip joint (2). Injection of local anesthetic or contrast material is a useful diagnostic test to determine if the SI joint is the pain source; intraarticular injection of corticosteroids may allow long-term pain relief in affected joints (3). Computed tomographic (CT) guidance was advocated for needle placement into the SI joint because fluoroscopy-guided injections were believed to be too difficult owing to the complex configuration of the joint (4,5). CT, however, is a time-consuming and expensive procedure. In previously described fluoroscopic techniques, the needle was directed in a posteroanterior direction by using complex angles in an attempt to distinguish the anterior from the posterior aspects of this curved joint (1,6–9).
The purpose of this study was to (a) describe a rapid and reproducible fluoroscopic technique for SI joint injection and (b) determine how many patients experienced immediate pain relief after injection of local anesthetic, which implicates the SI joint as the pain generator.
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Materials and Methods
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Fluoroscopy-guided SI joint injections for the diagnosis and treatment of pain, possibly of SI joint origin, were retrospectively evaluated in 24 patients (19 women and five men; age range, 24–91 years; mean age, 49 years). Patients were referred for pain over the SI joint (n = 11), low back pain (n = 10), or hip pain (n = 3). On conventional radiographs, the SI joints injected had a normal appearance in 16 patients, showed degenerative joint disease on the side of injection in seven, and showed bilateral sacroiliitis with erosions from ankylosing spondylitis in one.
Thirty-one SI joint injections were performed with local anesthetic (bupivacaine hydrochloride; Abbott Laboratories, North Chicago, Ill) and corticosteroids (betamethasone sodium phosphate and betamethasone acetate solution, Celestone Soluspan; Schering-Plough, Kenilworth, NJ). All SI joint injections were performed in outpatients, without premedication or sedation. The injections were performed by either musculoskeletal radiologists (R.G.D, P.A.K., M.W.A.) or musculoskeletal radiology fellows in training. Fluoroscopic time was recorded for all procedures. Both SI joints were injected in four subjects, and the same joint was injected on two separate occasions in three.
After informed consent was obtained, patients were positioned prone on the C-arm fluoroscopic table (Polystar; Siemens, Erlangen, Germany). With the x-ray tube perpendicular to the table, the skin was marked over the distal 1 cm of the SI joint (Fig 1a). The tube was then angled about 20°–25° in a cephalic direction to displace the posteroinferior portion of the SI joint in a caudal direction (Fig 1b). This allowed it to be clearly differentiated from the inaccessible anterior aspect of the joint, which moved cephalad on the image, as demonstrated on a dry pelvic specimen (Fig 2).
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Figure 1a. Posteroanterior fluoroscopic radiographs depict technique for SI joint injection, with patient prone. In a-d, R = right. (a) With the x-ray tube perpendicular to the fluoroscopic table, a localization probe (arrows) is centered over the distal 1 cm of the right SI joint, and the skin is marked. (b) With the x-ray tube angled 20° cephalad, the posterior aspect of the inferior SI joint (arrows) is clearly depicted caudally. (c) Straight needle (arrow) is advanced perpendicular to the fluoroscopic table into the posterior portion of the SI joint. (d) The x-ray tube is angled 25° cephalad, and the SI joint is opacified with contrast material (arrows).
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Figure 1b. Posteroanterior fluoroscopic radiographs depict technique for SI joint injection, with patient prone. In a-d, R = right. (a) With the x-ray tube perpendicular to the fluoroscopic table, a localization probe (arrows) is centered over the distal 1 cm of the right SI joint, and the skin is marked. (b) With the x-ray tube angled 20° cephalad, the posterior aspect of the inferior SI joint (arrows) is clearly depicted caudally. (c) Straight needle (arrow) is advanced perpendicular to the fluoroscopic table into the posterior portion of the SI joint. (d) The x-ray tube is angled 25° cephalad, and the SI joint is opacified with contrast material (arrows).
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Figure 1c. Posteroanterior fluoroscopic radiographs depict technique for SI joint injection, with patient prone. In a-d, R = right. (a) With the x-ray tube perpendicular to the fluoroscopic table, a localization probe (arrows) is centered over the distal 1 cm of the right SI joint, and the skin is marked. (b) With the x-ray tube angled 20° cephalad, the posterior aspect of the inferior SI joint (arrows) is clearly depicted caudally. (c) Straight needle (arrow) is advanced perpendicular to the fluoroscopic table into the posterior portion of the SI joint. (d) The x-ray tube is angled 25° cephalad, and the SI joint is opacified with contrast material (arrows).
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Figure 1d. Posteroanterior fluoroscopic radiographs depict technique for SI joint injection, with patient prone. In a-d, R = right. (a) With the x-ray tube perpendicular to the fluoroscopic table, a localization probe (arrows) is centered over the distal 1 cm of the right SI joint, and the skin is marked. (b) With the x-ray tube angled 20° cephalad, the posterior aspect of the inferior SI joint (arrows) is clearly depicted caudally. (c) Straight needle (arrow) is advanced perpendicular to the fluoroscopic table into the posterior portion of the SI joint. (d) The x-ray tube is angled 25° cephalad, and the SI joint is opacified with contrast material (arrows).
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Figure 2a. Fluoroscopic radiographs of a prone dry skeletal specimen of the pelvis demonstrate the effect of tube angulation. (a) With the x-ray tube perpendicular to the fluoroscopic table, a medial metallic dot (solid arrow, P) is positioned on the posteroinferior SI joints. Two slightly larger metallic dots located more laterally (open arrow, A) are affixed to the anteroinferior aspect of the SI joints. (b) With the x-ray tube angled 20° cephalad, the posterior aspects of the SI joints (solid arrow, P) project inferiorly and are now well outlined. The anterior aspects of the SI joints (open arrow, A) project superiorly and are more difficult to identify.
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Figure 2b. Fluoroscopic radiographs of a prone dry skeletal specimen of the pelvis demonstrate the effect of tube angulation. (a) With the x-ray tube perpendicular to the fluoroscopic table, a medial metallic dot (solid arrow, P) is positioned on the posteroinferior SI joints. Two slightly larger metallic dots located more laterally (open arrow, A) are affixed to the anteroinferior aspect of the SI joints. (b) With the x-ray tube angled 20° cephalad, the posterior aspects of the SI joints (solid arrow, P) project inferiorly and are now well outlined. The anterior aspects of the SI joints (open arrow, A) project superiorly and are more difficult to identify.
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Sterile technique was used, and the skin was anesthetized at the site previously marked. A 22-gauge, 3
- or 5-inch (depending on patient size) straight or 10° curved-tip spinal needle (Quincke type point; Beckton Dickinson, Franklin Lakes, NJ) was advanced perpendicular to the fluoroscopic table. With the tube in the cephalic position, the needle was directed toward the posterior SI joint, without angling of the needle in either a cephalic or caudal direction (Fig 1c). The 10° curved-tip needles were made by hand, with the needle bevel centered on the convex or outer part of the curve (Fig 3). The tip of the curved-tip needle was oriented in a cephalic direction, and the convex portion of the curve was oriented downward (closest to the joint). The curved-tip needle may be advanced either vertically or angled 10° downward to initially compensate for the 10° curve until the needle reaches the joint. As the needle contacted firm tissues on the posterior aspect of the joint, it was maneuvered through the ligaments and capsule into the joint by advancing it about 5–10 mm, usually by angling the needle tip slightly laterally to follow the natural curve of the joint. Intraarticular position was confirmed by injecting 0.2–0.5 mL of contrast material (Omnipaque [300 mg of iodine per milliliter], iohexol; Nycomed, Princeton, NJ) through the needle. When contrast material outlined the joint (Fig 3), 6 mg (1 mL) of betamethasone sodium phosphate and betamethasone acetate solution and 1 mL of 0.5% bupivacaine hydrochloride was injected.
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Figure 3a. Fluoroscopic radiographs were obtained with the x-ray tube angled 25° cephalad in a 91-year-old woman with right SI pain and a radiographically normal SI joint. No pain relief was obtained after injection of local anesthetic. (a) The intraarticular needle (arrowheads) is in position. (b) Contrast material (arrowheads) outlines the SI joint.
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Figure 3b. Fluoroscopic radiographs were obtained with the x-ray tube angled 25° cephalad in a 91-year-old woman with right SI pain and a radiographically normal SI joint. No pain relief was obtained after injection of local anesthetic. (a) The intraarticular needle (arrowheads) is in position. (b) Contrast material (arrowheads) outlines the SI joint.
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Each patient's pain level was recorded just prior to the procedure with use of a numeric grid line graded in centimeters from 0 (no pain) to 10 (the maximum tolerable pain). Approximately 10 minutes after the injection, the pain level was again recorded.
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Results
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All but one of the SI joints were successfully injected intraarticularly, as confirmed by means of injection of contrast material and fluoroscopic spot imaging. The mean fluoroscopic time for the procedure was 108 seconds (range, 36–328 seconds), and 70% (22 of 31) were performed in less than 2 minutes. Data for pain relief were available for 28 of the 31 injections. Two patients had no pain at the time of the procedure; therefore, an immediate change could not be evaluated in them. In a third patient, the pain level after the procedure was not available. After injection, pain decreased by 80% or more in seven of the 28 joints (27%); by 50%–70% in 11 joints (39%), including the patient with bilateral sacroiliitis [Fig 4]); and by less than 50% in 10 joints (36%). Pain relief of 50% or more after intraarticular injection of local anesthetic was obtained in 55% (10 of 18) of joints with normal conventional radiographs, in 62% (five of eight) of joints with degenerative joint disease, and in the one patient with bilateral sacroiliitis as a result of ankylosing spondylitis. In our series, pain decreased 50% or more in 64% (18 of 28) of the joints after intraarticular injection of local anesthetic.
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Figure 4a. Fluoroscopic radiographs depict left SI joint injection in a 24-year-old woman with ankylosing spondylitis. In a and b, L = left. (a) With the x-ray tube angled 20° cephalad, the SI joint space (arrows) is very narrow but clearly depicted. (b) With the x-ray tube perpendicular to the fluoroscopic table and the needle angled slightly cephalad, intraarticular contrast material is seen to fill articular erosions (arrows).
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Figure 4b. Fluoroscopic radiographs depict left SI joint injection in a 24-year-old woman with ankylosing spondylitis. In a and b, L = left. (a) With the x-ray tube angled 20° cephalad, the SI joint space (arrows) is very narrow but clearly depicted. (b) With the x-ray tube perpendicular to the fluoroscopic table and the needle angled slightly cephalad, intraarticular contrast material is seen to fill articular erosions (arrows).
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After the procedure, two patients experienced transient lower extremity weakness on the side of injection as a result of infiltration of anesthetic around the sciatic nerve. In both patients, the weakness resolved in the following 4 hours. There were no other complications during or after the injections.
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Discussion
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Imaging-guided diagnostic injections to help determine the precise structure(s) responsible for generating pain are gaining in popularity for different sites in the body (10–13). Such a diagnostic technique is useful because findings at physical examination are frequently inconclusive, and anatomic abnormalities identified on imaging studies are often not responsible for causing pain symptoms; conversely, normal-appearing structures may be painful (11,12,14,15). Our findings confirm the lack of correlation between imaging abnormalities and the painfulness of a structure.
Pain of SI joint origin may be difficult to diagnose. The pain pattern may cover the area of the buttock, hip, or proximal thigh and may mimic pain referred from lumbar disks, lumbar facet joints, or the hip (1,2). It is also a difficult joint to evaluate at physical examination because provocative tests are not specific for the SI joint and may simultaneously stress the lumbar spine and hip joints (2).
Intraarticular injection of the SI joint may help the diagnosis of pain of SI joint origin as a result of either provocation of typical pain symptoms after distention of the joint or relief of typical pain symptoms after injection of anesthetic. A provocative test consists of distention of the SI joint with contrast material. If pain is generated within the distribution of pain previously described by the patient, the test is positive. If there is no pain, the test is negative (16). A diagnostic test based on pain relief rather than pain provocation consists of injection of local anesthetic into the SI joint (17,18). If the patient reports 80% or more pain relief from the injection, the test is positive. If the pain is decreased 50%–80%, the SI joint may be considered a major contributor to the patient's pain. If pain relief is less than 50%, the test is negative. In our series, pain decreased 50% or more in 64% of the joints.
Corticosteroids can also be injected intraarticularly for more long-term therapeutic purposes. Our referring physicians prefer simultaneous injection of local anesthetic for immediate diagnostic purposes and corticosteroids for potential long-term pain relief, which eliminates the need for an additional injection with steroids at a later time in those patients who receive pain relief from the initial anesthetic injection. We do not perform provocative tests in the SI joint. Both diagnostic (provocative or pain relief) and therapeutic steroid injections rely on rapid, accurate, and painless intraarticular insertion of the needle.
The SI joint has typically been difficult to enter with a needle and fluoroscopic guidance owing to its complex configuration (9). The SI joint is curved, and the posterior aspect of the joint is located medially as compared with the anterior aspect of the joint, which is positioned relatively more laterally. Obliquity of the fluoroscopic tube in a medial or lateral direction may give the impression that the joint is well aligned, but, in fact, only a portion of the joint may be demonstrated, and the portion demonstrated is uncertain. Obviously, it is the posterior aspect of the joint that must be clearly visible at fluoroscopy to be accessed with a needle. The technique described herein allows this to occur. By angling the x-ray beam in a cephalic direction, the posterior aspect of the caudal end of the SI joint is clearly depicted separate from the remainder of the joint. This allows easy placement of a needle directly into this portion of the joint. As the joint is entered posteriorly, the needle may need to be oriented in a cephalic direction to remain in the joint. This is best obtained with the 10° curved-tip needle, with the curve directed cephalad.
This technique can be performed with use of any tilt tube fluoroscopic unit that permits cephalocaudal angulation of the x-ray tube. The same approach can be used for aspiration and lavage of the SI joint in cases of suspected sacroiliitis of infectious origin.
Our technique for intraarticular injection of SI joints can be performed with short fluoroscopic times (36–328 seconds). Because the injections were performed in a setting in which physicians were being trained, the fluoroscopic times were almost certainly elevated in comparison with what they would be with experienced radiologists. Still, the injections were performed within an acceptable mean fluoroscopic time of 108 seconds, with 70% performed in less than 2 minutes. This technique is also accurate, as confirmed by means of opacification of the SI joints in all but one patient. The one unsuccessful intraarticular injection could have been a result of a technical error or unsuspected ossification of the posterior aspect of the joint.
A 22-gauge, 3- or 5-inch straight or 10° curved-tip spinal needle can be used for the SI joint injection. We prefer use of a 10° curve on the needle. Once the posterior aspect of the joint is reached, the curve makes it easier to maneuver the needle into the curved joint with much greater latitude in positioning than is possible with a straight needle.
The sciatic nerve is located just anterior to the piriformis muscle, which is at the same depth as the inferior aspect of the SI joint. Aggressive injection of local anesthetic at the time the skin is anesthetized, improper positioning of the needle, or extravasation of bupivacaine hydrochloride at the time the joint is injected may lead to transient lower extremity weakness. This occurred in two of our patients, but they reported the symptoms had resolved when they were contacted by phone the following morning. Because of such potential complications, we ask that patients who undergo this procedure have someone available to drive them home after the injection.
Because this was a retrospective study, we acquired data that allowed evaluation of only the immediate response to intraarticular local anesthetic injection. We did not have the follow-up pain diaries to allow evaluation of the long-term therapeutic effect of the corticosteroids injected. Another potential limitation is that we used a numeric pain scale instead of a visual analog pain scale. Numeric scales predispose patients to preferential selection of certain numbers at the middle or end of the scale, such as 5 or 10, and this is less likely to occur with a visual analog scale (19,20). In this investigation, however, initial numeric pain levels selected by patients were distributed throughout the scale and did not appear to be grouped. We use a numeric scale (rather than a visual analog scale without numbers) for all diagnostic injections because our patients and various referring physicians find it easier to understand. It also provides a quick and simple way to report the patient's pain levels before and immediately after injection.
In conclusion, fluoroscopy-guided intra-articular needle insertion, as described, is a safe and rapid procedure. The response to intraarticular injection of local anesthetic can be a useful diagnostic test in the evaluation of pain that may originate from the SI joints.
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Footnotes
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Abbreviation: SI = sacroiliac
Author contributions: Guarantors of integrity of entire study, R.G.D., P.A.K.; study concepts and design, R.G.D., P.A.K.; definition of intellectual content, R.G.D., P.A.K.; literature research, R.G.D.; clinical studies, R.G.D., P.A.K., M.W.A.; data acquisition and analysis, R.G.D., P.A.K., M.W.A.; manuscript preparation, R.G.D., P.A.K.; manuscript editing, P.A.K., M.W.A.; manuscript review, R.G.D., P.A.K., M.W.A.
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Abstract
Introduction
