Eur Spine J DOI 10.1007/s00586-014-3375-y
ORIGINAL ARTICLE
The diagnostic value of single-photon emission computed tomography/computed tomography for severe sacroiliac joint dysfunction Katsuhiro Tofuku • Hiroaki Koga • Setsuro Komiya
Received: 28 January 2014 / Revised: 4 May 2014 / Accepted: 4 May 2014 Ó Springer-Verlag Berlin Heidelberg 2014
Abstract Purpose We aimed to evaluate the value of single-photon emission computed tomography (SPECT)/computed tomography (CT) for the diagnosis of sacroiliac joint (SIJ) dysfunction. Methods SPECT/CT was performed in 32 patients with severe SIJ dysfunction, who did not respond to 1-year conservative treatment and had a score of [4 points on a 10-cm visual analog scale. We investigated the relationship between the presence of severe SIJ dysfunction and tracer accumulation, as confirmed by SPECT/CT. In cases of bilateral SIJ dysfunction, we also compared the intensity of tracer accumulation on each side. Moreover, we examined the relationship between the intensity of tracer accumulation and the different treatments the patients subsequently received. Results All 32 patients with severe SIJ dysfunction had tracer accumulation with a standardized uptake value (SUV) of [2.2 (mean SUV 4.7). In the 19 patients with lateralized symptom intensity, mean SUVs of the dominant side were significantly higher than those of the nondominant side. In 10 patients with no lateralization, the difference in the SUVs between sides was \0.6. Patients exhibiting higher levels of tracer accumulation required more advanced treatment. Conclusion Patients with higher levels of tracer accumulation had greater symptom severity and also required K. Tofuku (&) H. Koga Department of Orthopedic Surgery, Imakiire General Hospital, 4-16 Shimotatsuo, Kagoshima 892-8502, Japan e-mail: [email protected] S. Komiya Department of Orthopedic Surgery, Kagoshima Graduate School of Medical and Dental Sciences, Kagoshima, Japan
more advanced treatment. Thus, we believe that SPECT/ CT may be a suitable supplementary diagnostic modality for SIJ dysfunction as well as a useful technique for predicting the prognosis of this condition. Keywords Diagnosis Imaging fusion Sacroiliac joint dysfunction SPECT/CT
Introduction Sacroiliac joint (SIJ) dysfunction is the cause of low back pain in 10–25 % of cases [1]; this percentage may be even higher in pregnancy-related pelvic girdle pain [2]. Pain originating in the SIJ is typically perceived in the lumbar region, buttock, groin, abdomen, and/or lower limb. At the beginning of the twentieth century, the SIJ dysfunction was considered the most important cause of low back pain. With the use of magnetic resonance imaging (MRI), lumbar disc herniation was found to be a cause of low back pain; after this, the importance of SIJ as a cause of this symptom has decreased. Because pain caused by SIJ dysfunction can mimic discogenic or radicular low back pain, we assume that the diagnosis of SIJ dysfunction is frequently overlooked. Galm et al. [3] reported that 46 of 150 patients with herniated lumbar discs were diagnosed with SIJ dysfunction; they suggested that in cases with low back pain and sciatica, SIJ dysfunction should be considered, and appropriate therapy should be initiated. It is also worth discussing whether a disc herniation and SIJ dysfunction develop independently or whether they are related. If it would be possible to determine whether SIJ dysfunction is related to the manifesting symptoms, the number of surgical operations performed could be reduced.
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Although there are no conclusive tests for the diagnosis of SIJ dysfunction, SIJ blocks are the current gold standard; an analgesic response to a properly performed anesthetic block is the most reliable method of diagnosing SIJ dysfunction. However, the diagnostic value of SIJ blocks remains controversial because of the potential for falsepositive and false-negative results. The potential causes of inaccurate blocks include dispersal of the local anesthetic to adjacent pain-generating structures and failure to achieve infiltration throughout the entire SIJ complex. Radiography, computed tomography (CT), and MRI are not helpful for the diagnosis of painful SIJ dysfunction because these modalities typically only show a few abnormal findings. Further, other imaging modalities are not useful for the diagnosis of SIJ dysfunction. After the recent developments in combined SPECT and CT imaging, the potential for identifying the exact location of scintigraphic lesions has improved compared to that with SPECT alone. To our knowledge, only a few previous reports have described the use of SPECT/CT for the diagnosis of this condition [4]. In the present study, we aimed to evaluate the diagnostic value of SPECT/CT for SIJ dysfunction.
We investigated the relationship between the presence of severe SIJ dysfunction confirmed by SIJ block and tracer accumulation as shown on SPECT/CT. In the cases of bilateral SIJ dysfunction, we also compared the intensity of tracer accumulation on both sides. The relationship between the intensity of tracer accumulation and the treatments subsequently required by the patients was also examined. In positron emission tomography studies, quantitative analysis was performed using the standardized uptake value (SUV). This dimensionless quantity is calculated from the activity concentration measured in the lesion or region of interest, and the total injected dose in a patient of a specified weight. SPECT does not provide quantitative information on the regional activity concentration of the injected tracer, and therefore, the potential for the use of SUV in SPECT imaging has not been widely recognized. However, recent studies successfully demonstrated the application of SUV measurements in the estimation of various regions of interest, including tumors and the spine [5, 6]. In the present SPECT/CT study, SUV was used for the quantitative analysis of regional activity concentration of the injected tracer. The mean duration of follow-up was 15.3 months (range 13–22 months).
Materials and methods
Results
Thirty-two patients with severe SIJ dysfunction unresponsive to 1 year of conservative treatment who had a score of [4 points on a 10-cm visual analog scale (VAS) underwent SPECT/CT in our hospital. The Institutional Review Board at our hospital approved this study protocol. An SIJ block was considered positive when the contrast was injected directly into the SIJ under fluoroscopic guidance followed by a 2-mL injection of 2 % lidocaine, and up to 75 % pain relief was achieved. A positive block confirmed the diagnosis of SIJ dysfunction. Whole-body scintigraphy was performed 3 h after the intravenous injection of 740 MBq of Tc-99 m-methylene diphosphonate using a dual-head gamma camera equipped with a low-energy high-resolution parallel-hole collimator. For SPECT acquisition, counts from the 20 % energy windows at 140 keV were acquired as a 128 9 128 matrix. The SPECT raw data were reconstructed into axial, coronal, and sagittal slices using reconstruction software. CT scans were performed with the patient in the same position after SPECT. The CT dataset was acquired with a tube voltage of 120 kVp, a different current intensity depending on the patient, and a slice width of 5 mm. The CT images were coregistered with the SPECT images using a nuclear medicine workstation. CT attenuation correction was applied to the SPECT images.
All 32 [10 men and 22 women; mean age, 49.4 years (range 19–80 years)] patients with severe SIJ dysfunction showed tracer accumulation, with a mean SUV of 4.7 (range 2.2–9.9). Twenty-nine patients had bilateral SIJ dysfunction including 19 patients with lateralized symptom intensity (Group A): 11 patients had right-sided symptom dominance and 8 patients had left-sided symptom dominance, and 10 patients had no lateralized symptom intensity (Group B). Three patients had unilateral SIJ dysfunction (Group C), and all these three patients exhibited left-sided symptoms. All 19 patients with lateralized symptom intensity (Group A) showed a higher SUV on the symptom-dominant side than on the nondominant side. The mean SUV of the dominant side was 5.3 (range 3.6–9.9), which was significantly higher than that of the nondominant side (mean 4.1; range 2.2–6.9; Student t test, P = 0.02). However, in the 10 patients without lateralized symptom intensity (Group B), the difference in the SUV between the sides was \0.6. The mean difference in the SUV between the two sides in Group B was 0.22 (range 0.0–0.6), which was significantly lower than the mean difference in the SUV between the 2 sides in Group A (mean 1.22; range 0.2–5.4; Mann–Whitney U test, P = 0.0006). In the three patients with unilateral SIJ dysfunction (Group C), the affected side had tracer
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Eur Spine J Table 1 Summary of the SUV of patients with severe SIJ dysfunction Mean SUV
Mean difference in the SUV between the two sides
Total
4.7
1.22
Dominant side
5.3
Group A (N = 19)
Nondominant side
4.1
Group B (N = 10)
4.8
0.22
Group C (N = 3)
3.6
N/A
SUV standardized uptake value, SIJ sacroiliac joint
accumulation, with a mean SUV of 3.6 (range 3.0–4.8); no tracer accumulation was noted in the non-affected side (Table 1). Patients were initially treated with drug therapy using nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, steroids, and narcotics in addition to other conservative treatment options. In cases that did not respond to conservative treatment in the present study, surgery for SIJ fixation was performed. At the final follow-up, 22 patients had been treated with oral NSAIDs, opioids, and steroids (Group D), whereas five patients were treated with narcotics due to resistance to oral medications (Group E). Five patients who were resistant to conservative treatment underwent surgery for SIJ fixation (Group F). The mean SUV in Groups D, E, and F were 4.4 (range 2.8–7.2), 5.4 (range 3.2–7.5), and 7.4 (range 5.4–9.9), respectively. Although there were no statistically significant differences, Group F had higher SUV than Group E, and Group E had higher SUV than Group D. Thus, higher levels of tracer accumulation tended to indicate the need for more advanced treatment. In the cases of bilateral SIJ dysfunction, higher SUV was used.
Case presentation A 41-year-old woman with a 2-year history of severe low back, groin, gluteal, and thigh pain was referred to our hospital after she was involved in an automobile accident. Patrick’s and Gaenslen’s tests indicated positive results on both sides. Moreover, she experienced pain on palpation at both sides of the sacral sulcus. The results of imaging studies, including radiography, CT, and MRI, were normal. The SIJ blocks indicated positive results on both sides. The VAS score for both right and left sides was nine points. The SUVs were 5.4 and 5.7 for the right and left sides, respectively. Because she was resistant to conservative treatment, she underwent surgery for SIJ fixation on the left side through an anterior approach. Her VAS score improved to three points at 1 month after the operation (Fig. 1).
Discussion The SIJ has rich nociceptive innervation. The anterior portion receives innervation from the posterior rami of the L2–S2 roots. Additional fibers originate from the obturator nerve, superior gluteal nerve, and lumbosacral trunk. The posterior portion is innervated by the posterior rami of L4– S3 [7]. The piriformis muscle is the largest of the short rotators of the hip and crosses both the hip joint and the SIJ. It originates from the lateral part of the ventral surface of the second, third, and fourth sacral vertebrae, and converges on a rounded tendon that is inserted into the medial side of the superior surface of the greater trochanter. The sciatic nerve passes under or occasionally (partially) through the piriformis muscle. Any process in the SIJ that induces piriformis spasm may provoke sciatic irritation. Due to this abundant innervation and the occurrence of entrapment neuropathy, pain mimicking a radiculopathy may develop in various regions, including the buttocks, groin, thigh, calf, and foot. Unidirectional pelvic shear stress, repetitive torsional forces, and inflammation can cause pain. The risk factors include leg length discrepancy, abnormal gait pattern, trauma, scoliosis, lumbar fusion surgery, heavy physical exertion, and pregnancy [4, 8, 9]. Numerous studies of adjacent segment disease after lumbar fusion surgery have shown increased mobility in the cephalad and/or caudad adjacent segments, as well as increased stress on the facet joints and/or discs of adjacent segments [10, 11]. This could also apply to the SIJ. Spinal surgery, including lumbar laminectomy and/or fusion, can increase impact loading on the SIJ, leading to mechanical overload. The common structural causes for low back, gluteal, and lower extremity pain after lumbar fusion include foraminal or central stenosis, facet syndrome, and discogenic pain. Most spinal clinicians are familiar with these conditions, but painful SIJ dysfunction may not be well recognized and thus, may not be considered in patients with pain after lumbar fusion. In patients who experience persistent low back pain after lumbar fusion, a prevalence rate of 32–35 % for SIJ dysfunction has been indicated by diagnostic SIJ blocks [8]. Solitary provocative maneuvers have little diagnostic value and frequently result in false-negative results because large forces are needed to stress the SIJ. Further, if forces are exerted incorrectly, pain can be provoked in neighboring structures, resulting in false-positive results. However, two studies have shown that C3 positive provocative tests resulted in a specificity and sensitivity of 79 and 85 %, and 78 and 94 %, respectively [12, 13]. In addition, Szadek et al. [14] reported that C3 positive provocative tests had discriminative power for diagnosis in a metaanalysis. SIJ blocks are considered the gold standard for the
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Fig. 1 A 41-year-old woman with a 2-year history of severe pain in the low back, groin, gluteal, and thigh regions, following an automobile accident. a Computed tomography (CT) image.
b Single-photon emission computed tomography (SPECT) image combined with CT data providing a fusion image. c SPECT/CT image showing significant radiotracer uptake at both sacroiliac joints
diagnosis of SIJ dysfunction. Although some authors have used a single diagnostic block for clinical studies and some advocate the use of confirmatory double blocks using two different local anesthetics with different durations of action [12, 13], the diagnostic value of SIJ blocks remains controversial because of the potential for false-positive and false-negative results. The potential causes of inaccurate blocks include dispersal of the local anesthetic to adjacent pain-generating structures and failure to achieve infiltration throughout the entire SIJ complex. The diagnosis of SIJ dysfunction by imaging remains difficult. In some studies, radiography, CT, and MRI have been used to identify SIJ dysfunction. However, a correlation has not been consistently demonstrated between imaging findings and SIJ dysfunction confirmed by diagnostic SIJ blocks [15]. Bone scans are the procedure of choice for demonstrating stress fractures, infection, or osteoarthritic lesions. Tracer uptake is a function of blood flow and bone matrix turnover. If the osteoarthritic process is active in the cartilage, which is indicative of further destruction, the subchondral bone is also metabolically abnormal either in response to or along with the factor causing the cartilage destruction. A scintigraphy would only indicate positive results in a lesion with an active osteoarthritic process causing subchondral bone turnover. Morphological changes in radiological imaging correlate poorly with symptoms and the progression of degenerative joint disease [16].
However, scintigraphic activity correlates with the symptoms of degenerative joint disease and has a strong negative predictive value for the progression of joint degeneration [17]. Quantitative scintigraphy has poor sensitivity in identifying patients with SIJ dysfunction who respond to anesthetic SIJ injection. Slipman et al. [18] reported that only 12.9 % of patients with SIJ syndrome had an abnormal bone scan appearance, although the specificity was 100 %. Maigne et al. [19] reported that the sensitivity in identifying the SIJ dysfunction as a cause of low back pain was 46.1 % and the specificity was 89.5 %. SPECT scanning is a lesser invasive modality and has superior lesion detection ability compared with planar bone imaging, which is more sensitive than radionuclide bone scanning. The number of detected spinal lesions may increase by 20–50 %, and improvements in sensitivity, specificity, and negative predictive and positive predictive values have been reported [20, 21]. SPECT is also advantageous because of its improved anatomic localization of abnormalities—a feature that has been widely used in patients with spinal pain for the diagnosis of facet joint arthritis. Previous studies have shown that SPECT results correlate well with the response to facet joint steroid injections [22, 23]. However, Dolan et al. [22] reported that only 38 % of patients with facet joint pain diagnosed using facet joint blocks showed positive findings on scans on increased uptake, thus scans are considered to have low
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sensitivity. A multimodality imaging technique combining high-resolution structural images (CT) and functional radionuclide scan images (SPECT) has recently been developed. The advantages of SPECT/CT are also expected to be useful in non-malignant conditions. SPECT has improved sensitivity compared to planar imaging. The high spatial resolution of CT along with the structural information this modality provides enables an accurate assessment of the lesion site. Moreover, the additional information on the shape and structure of the abnormalities improves the specificity of the method. Consequently, specificity is considerably higher with SPECT/CT than with SPECT alone, and SPECT/CT is slightly more sensitive than SPECT alone [24]. If SPECT/CT was to be used only in patients with severe facet joint or SIJ syndrome, the sensitivity would be greatly improved. In terms of SIJ dysfunction, Cusi et al. [4] demonstrated metabolic disturbances in and around the SIJ using hybrid imaging with SPECT/CT in patients with peripartum or traumatic SIJ dysfunction. Their study successfully detected SIJ lesions by finding a specific pattern of metabolic disturbances, and the technique showed a sensitivity of 95 %, specificity of 99 %, positive predictive value of 99 %, and negative predictive value of 94 %.
Conclusion Our findings suggest that the use of SPECT/CT adds value in detecting patients with SIJ dysfunction, who are resistant to conservative treatment. We observed a tendency for a higher tracer accumulation in patients with greater symptom severity who also required more advanced treatment. Thus, we believe that SPECT/CT might be a suitable supplementary diagnostic modality for SIJ dysfunction, and may be useful for predicting the prognosis of this condition. Conflict of interest
None.
References 1. Hansen HC, McKenzie-Brown AM, Cohen SP, Swicegood JR, Colson JD, Manchikanti L (2007) Sacroiliac joint interventions: a systematic review. Pain Physician 10:165–184 2. Albert HB, Godskesen M, Westergaard JG (2002) Incidence of four syndromes of pregnancy-related pelvic joint pain. Spine 27:2831–2834 3. Galm R, Fro¨hling M, Rittmeister M, Schmitt E (1998) Sacroiliac joint dysfunction in patients with imaging-proven lumbar disc herniation. Eur Spine J 7:450–453 4. Cusi M, Saunders J, Van der Wall H, Fogelman I (2013) Metabolic disturbances identified by SPECT-CT in patients with a clinical diagnosis of sacroiliac joint incompetence. Eur Spine J 22:1674–1682
5. Beauregard JM, Hofman MS, Pereira JM, Eu P, Hicks RJ (2011) Quantitative (177)Lu SPECT (QSPECT) imaging using a commercially available SPECT/CT system. Cancer Imaging 11:56–66 6. Cachovan M, Vija AH, Hornegger J, Kuwert T (2013) Quantification of 99mTc-DPD concentration in the lumbar spine with SPECT/CT. EJNMMI Res 3:45 7. Atlihan D, Tekdemir I, Atesˆ Y, Elhan A (2000) Anatomy of the anterior sacroiliac joint with reference to lumbosacral nerves. Clin Orthop Relat Res 376:236–241 8. Katz V, Schofferman J, Reynolds J (2003) The sacroiliac joint: a potential cause of pain after lumbar fusion to the sacrum. J Spinal Disord Tech 16:96–99 9. Albert H, Godskesen M, Westergaard J (2001) Prognosis in four syndromes of pregnancy-related pelvic pain. Acta Obstet Gynecol Scand 80:505–510 10. Bastian L, Lange U, Knop C, Tusch G, Blauth M (2001) Evaluation of the mobility of adjacent segments after posterior thoracolumbar fixation: a biomechanical study. Eur Spine J 10:295–300 11. Chen CS, Cheng CK, Liu CL (2002) A biomechanical comparison of posterolateral fusion and posterior fusion in the lumbar spine. J Spinal Disord Tech 15:53–63 12. Laslett M, Aprill CN, McDonald B, Young SB (2005) Diagnosis of sacroiliac joint pain: validity of individual provocation tests and composites of tests. Man Ther 10:207–218 13. van der Wurff P, Buijs EJ, Groen GJ (2006) A multitest regimen of pain provocation tests as an aid to reduce unnecessary minimally invasive sacroiliac joint procedures. Arch Phys Med Rehabil 87:10–14 14. Szadek KM, van der Wurff P, van Tulder MW, Zuurmond WW, Perez RS (2009) Diagnostic validity of criteria for sacroiliac joint pain: a systematic review. J Pain 10:354–368 15. Hansen HC, McKenzie-Brown AM, Cohen SP, Swicegood JR, Colson JD, Manchikanti L (2007) Sacroiliac joint interventions: a systematic review. Pain Physician 10:165–184 16. Dieppe PA, Cushnaghan J, Shepstone L (1997) The Bristol ‘OA5000 study: progression of osteoarthritis (OA) over 3 years and the relationship between clinical and radiographic changes at the knee joint. Osteoarthr Cartil 5:87–97 17. Kim HR, So Y, Moon SG, Lee IS, Lee SH (2008) Clinical value of (99 m)Tc-methylene diphosphonate (MDP) bone single photon emission computed tomography (SPECT) in patients with knee osteoarthritis. Osteoarthr Cartil 16:212–218 18. Slipman CW, Sterenfeld EB, Chou LH, Herzog R, Vresilovic E (1996) The value of radionuclide imaging in the diagnosis of sacroiliac joint syndrome. Spine 21:2251–2254 19. Maigne JY, Boulahdour H, Chatellier G (1998) Value of quantitative radionuclide bone scanning in the diagnosis of sacroiliac joint syndrome in 32 patients with low back pain. Eur Spine J 7:328–331 20. Gates GF (1998) SPECT bone scanning of the spine. Semin Nucl Med 28:78–94 21. Reinartz P, Schaffeldt J, Sabri O, Zimny M, Nowak B, Ostwald E, Cremerius U, Buell U (2000) Benign versus malignant osseous lesions in the lumbar vertebrae: differentiation by means of bone SPET. Eur J Nucl Med 27:721–726 22. Dolan AL, Ryan PJ, Arden NK, Stratton R, Wedley JR, Hamann W, Fogelman I, Gibson T (1996) The value of SPECT scans in identifying back pain likely to benefit from facet joint injection. Br J Rheumatol 35:1269–1273 23. Pneumaticos SG, Chatziioannou SN, Hipp JA, Moore WH, Esses SI (2006) Low back pain: prediction of short-term outcome of facet joint injection with bone scintigraphy. Radiology 238:693–698 24. Horger M, Eschmann SM, Pfannenberg C, Vonthein R, Besenfelder H, Claussen CD, Bares R (2004) Evaluation of combined transmission and emission tomography for classification of skeletal lesions. AJR Am J Roentgenol 183:655–661
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ORIGINAL ARTICLE
The diagnostic value of single-photon emission computed tomography/computed tomography for severe sacroiliac joint dysfunction Katsuhiro Tofuku • Hiroaki Koga • Setsuro Komiya
Received: 28 January 2014 / Revised: 4 May 2014 / Accepted: 4 May 2014 Ó Springer-Verlag Berlin Heidelberg 2014
Abstract Purpose We aimed to evaluate the value of single-photon emission computed tomography (SPECT)/computed tomography (CT) for the diagnosis of sacroiliac joint (SIJ) dysfunction. Methods SPECT/CT was performed in 32 patients with severe SIJ dysfunction, who did not respond to 1-year conservative treatment and had a score of [4 points on a 10-cm visual analog scale. We investigated the relationship between the presence of severe SIJ dysfunction and tracer accumulation, as confirmed by SPECT/CT. In cases of bilateral SIJ dysfunction, we also compared the intensity of tracer accumulation on each side. Moreover, we examined the relationship between the intensity of tracer accumulation and the different treatments the patients subsequently received. Results All 32 patients with severe SIJ dysfunction had tracer accumulation with a standardized uptake value (SUV) of [2.2 (mean SUV 4.7). In the 19 patients with lateralized symptom intensity, mean SUVs of the dominant side were significantly higher than those of the nondominant side. In 10 patients with no lateralization, the difference in the SUVs between sides was \0.6. Patients exhibiting higher levels of tracer accumulation required more advanced treatment. Conclusion Patients with higher levels of tracer accumulation had greater symptom severity and also required K. Tofuku (&) H. Koga Department of Orthopedic Surgery, Imakiire General Hospital, 4-16 Shimotatsuo, Kagoshima 892-8502, Japan e-mail: [email protected] S. Komiya Department of Orthopedic Surgery, Kagoshima Graduate School of Medical and Dental Sciences, Kagoshima, Japan
more advanced treatment. Thus, we believe that SPECT/ CT may be a suitable supplementary diagnostic modality for SIJ dysfunction as well as a useful technique for predicting the prognosis of this condition. Keywords Diagnosis Imaging fusion Sacroiliac joint dysfunction SPECT/CT
Introduction Sacroiliac joint (SIJ) dysfunction is the cause of low back pain in 10–25 % of cases [1]; this percentage may be even higher in pregnancy-related pelvic girdle pain [2]. Pain originating in the SIJ is typically perceived in the lumbar region, buttock, groin, abdomen, and/or lower limb. At the beginning of the twentieth century, the SIJ dysfunction was considered the most important cause of low back pain. With the use of magnetic resonance imaging (MRI), lumbar disc herniation was found to be a cause of low back pain; after this, the importance of SIJ as a cause of this symptom has decreased. Because pain caused by SIJ dysfunction can mimic discogenic or radicular low back pain, we assume that the diagnosis of SIJ dysfunction is frequently overlooked. Galm et al. [3] reported that 46 of 150 patients with herniated lumbar discs were diagnosed with SIJ dysfunction; they suggested that in cases with low back pain and sciatica, SIJ dysfunction should be considered, and appropriate therapy should be initiated. It is also worth discussing whether a disc herniation and SIJ dysfunction develop independently or whether they are related. If it would be possible to determine whether SIJ dysfunction is related to the manifesting symptoms, the number of surgical operations performed could be reduced.
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Eur Spine J
Although there are no conclusive tests for the diagnosis of SIJ dysfunction, SIJ blocks are the current gold standard; an analgesic response to a properly performed anesthetic block is the most reliable method of diagnosing SIJ dysfunction. However, the diagnostic value of SIJ blocks remains controversial because of the potential for falsepositive and false-negative results. The potential causes of inaccurate blocks include dispersal of the local anesthetic to adjacent pain-generating structures and failure to achieve infiltration throughout the entire SIJ complex. Radiography, computed tomography (CT), and MRI are not helpful for the diagnosis of painful SIJ dysfunction because these modalities typically only show a few abnormal findings. Further, other imaging modalities are not useful for the diagnosis of SIJ dysfunction. After the recent developments in combined SPECT and CT imaging, the potential for identifying the exact location of scintigraphic lesions has improved compared to that with SPECT alone. To our knowledge, only a few previous reports have described the use of SPECT/CT for the diagnosis of this condition [4]. In the present study, we aimed to evaluate the diagnostic value of SPECT/CT for SIJ dysfunction.
We investigated the relationship between the presence of severe SIJ dysfunction confirmed by SIJ block and tracer accumulation as shown on SPECT/CT. In the cases of bilateral SIJ dysfunction, we also compared the intensity of tracer accumulation on both sides. The relationship between the intensity of tracer accumulation and the treatments subsequently required by the patients was also examined. In positron emission tomography studies, quantitative analysis was performed using the standardized uptake value (SUV). This dimensionless quantity is calculated from the activity concentration measured in the lesion or region of interest, and the total injected dose in a patient of a specified weight. SPECT does not provide quantitative information on the regional activity concentration of the injected tracer, and therefore, the potential for the use of SUV in SPECT imaging has not been widely recognized. However, recent studies successfully demonstrated the application of SUV measurements in the estimation of various regions of interest, including tumors and the spine [5, 6]. In the present SPECT/CT study, SUV was used for the quantitative analysis of regional activity concentration of the injected tracer. The mean duration of follow-up was 15.3 months (range 13–22 months).
Materials and methods
Results
Thirty-two patients with severe SIJ dysfunction unresponsive to 1 year of conservative treatment who had a score of [4 points on a 10-cm visual analog scale (VAS) underwent SPECT/CT in our hospital. The Institutional Review Board at our hospital approved this study protocol. An SIJ block was considered positive when the contrast was injected directly into the SIJ under fluoroscopic guidance followed by a 2-mL injection of 2 % lidocaine, and up to 75 % pain relief was achieved. A positive block confirmed the diagnosis of SIJ dysfunction. Whole-body scintigraphy was performed 3 h after the intravenous injection of 740 MBq of Tc-99 m-methylene diphosphonate using a dual-head gamma camera equipped with a low-energy high-resolution parallel-hole collimator. For SPECT acquisition, counts from the 20 % energy windows at 140 keV were acquired as a 128 9 128 matrix. The SPECT raw data were reconstructed into axial, coronal, and sagittal slices using reconstruction software. CT scans were performed with the patient in the same position after SPECT. The CT dataset was acquired with a tube voltage of 120 kVp, a different current intensity depending on the patient, and a slice width of 5 mm. The CT images were coregistered with the SPECT images using a nuclear medicine workstation. CT attenuation correction was applied to the SPECT images.
All 32 [10 men and 22 women; mean age, 49.4 years (range 19–80 years)] patients with severe SIJ dysfunction showed tracer accumulation, with a mean SUV of 4.7 (range 2.2–9.9). Twenty-nine patients had bilateral SIJ dysfunction including 19 patients with lateralized symptom intensity (Group A): 11 patients had right-sided symptom dominance and 8 patients had left-sided symptom dominance, and 10 patients had no lateralized symptom intensity (Group B). Three patients had unilateral SIJ dysfunction (Group C), and all these three patients exhibited left-sided symptoms. All 19 patients with lateralized symptom intensity (Group A) showed a higher SUV on the symptom-dominant side than on the nondominant side. The mean SUV of the dominant side was 5.3 (range 3.6–9.9), which was significantly higher than that of the nondominant side (mean 4.1; range 2.2–6.9; Student t test, P = 0.02). However, in the 10 patients without lateralized symptom intensity (Group B), the difference in the SUV between the sides was \0.6. The mean difference in the SUV between the two sides in Group B was 0.22 (range 0.0–0.6), which was significantly lower than the mean difference in the SUV between the 2 sides in Group A (mean 1.22; range 0.2–5.4; Mann–Whitney U test, P = 0.0006). In the three patients with unilateral SIJ dysfunction (Group C), the affected side had tracer
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Eur Spine J Table 1 Summary of the SUV of patients with severe SIJ dysfunction Mean SUV
Mean difference in the SUV between the two sides
Total
4.7
1.22
Dominant side
5.3
Group A (N = 19)
Nondominant side
4.1
Group B (N = 10)
4.8
0.22
Group C (N = 3)
3.6
N/A
SUV standardized uptake value, SIJ sacroiliac joint
accumulation, with a mean SUV of 3.6 (range 3.0–4.8); no tracer accumulation was noted in the non-affected side (Table 1). Patients were initially treated with drug therapy using nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, steroids, and narcotics in addition to other conservative treatment options. In cases that did not respond to conservative treatment in the present study, surgery for SIJ fixation was performed. At the final follow-up, 22 patients had been treated with oral NSAIDs, opioids, and steroids (Group D), whereas five patients were treated with narcotics due to resistance to oral medications (Group E). Five patients who were resistant to conservative treatment underwent surgery for SIJ fixation (Group F). The mean SUV in Groups D, E, and F were 4.4 (range 2.8–7.2), 5.4 (range 3.2–7.5), and 7.4 (range 5.4–9.9), respectively. Although there were no statistically significant differences, Group F had higher SUV than Group E, and Group E had higher SUV than Group D. Thus, higher levels of tracer accumulation tended to indicate the need for more advanced treatment. In the cases of bilateral SIJ dysfunction, higher SUV was used.
Case presentation A 41-year-old woman with a 2-year history of severe low back, groin, gluteal, and thigh pain was referred to our hospital after she was involved in an automobile accident. Patrick’s and Gaenslen’s tests indicated positive results on both sides. Moreover, she experienced pain on palpation at both sides of the sacral sulcus. The results of imaging studies, including radiography, CT, and MRI, were normal. The SIJ blocks indicated positive results on both sides. The VAS score for both right and left sides was nine points. The SUVs were 5.4 and 5.7 for the right and left sides, respectively. Because she was resistant to conservative treatment, she underwent surgery for SIJ fixation on the left side through an anterior approach. Her VAS score improved to three points at 1 month after the operation (Fig. 1).
Discussion The SIJ has rich nociceptive innervation. The anterior portion receives innervation from the posterior rami of the L2–S2 roots. Additional fibers originate from the obturator nerve, superior gluteal nerve, and lumbosacral trunk. The posterior portion is innervated by the posterior rami of L4– S3 [7]. The piriformis muscle is the largest of the short rotators of the hip and crosses both the hip joint and the SIJ. It originates from the lateral part of the ventral surface of the second, third, and fourth sacral vertebrae, and converges on a rounded tendon that is inserted into the medial side of the superior surface of the greater trochanter. The sciatic nerve passes under or occasionally (partially) through the piriformis muscle. Any process in the SIJ that induces piriformis spasm may provoke sciatic irritation. Due to this abundant innervation and the occurrence of entrapment neuropathy, pain mimicking a radiculopathy may develop in various regions, including the buttocks, groin, thigh, calf, and foot. Unidirectional pelvic shear stress, repetitive torsional forces, and inflammation can cause pain. The risk factors include leg length discrepancy, abnormal gait pattern, trauma, scoliosis, lumbar fusion surgery, heavy physical exertion, and pregnancy [4, 8, 9]. Numerous studies of adjacent segment disease after lumbar fusion surgery have shown increased mobility in the cephalad and/or caudad adjacent segments, as well as increased stress on the facet joints and/or discs of adjacent segments [10, 11]. This could also apply to the SIJ. Spinal surgery, including lumbar laminectomy and/or fusion, can increase impact loading on the SIJ, leading to mechanical overload. The common structural causes for low back, gluteal, and lower extremity pain after lumbar fusion include foraminal or central stenosis, facet syndrome, and discogenic pain. Most spinal clinicians are familiar with these conditions, but painful SIJ dysfunction may not be well recognized and thus, may not be considered in patients with pain after lumbar fusion. In patients who experience persistent low back pain after lumbar fusion, a prevalence rate of 32–35 % for SIJ dysfunction has been indicated by diagnostic SIJ blocks [8]. Solitary provocative maneuvers have little diagnostic value and frequently result in false-negative results because large forces are needed to stress the SIJ. Further, if forces are exerted incorrectly, pain can be provoked in neighboring structures, resulting in false-positive results. However, two studies have shown that C3 positive provocative tests resulted in a specificity and sensitivity of 79 and 85 %, and 78 and 94 %, respectively [12, 13]. In addition, Szadek et al. [14] reported that C3 positive provocative tests had discriminative power for diagnosis in a metaanalysis. SIJ blocks are considered the gold standard for the
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Fig. 1 A 41-year-old woman with a 2-year history of severe pain in the low back, groin, gluteal, and thigh regions, following an automobile accident. a Computed tomography (CT) image.
b Single-photon emission computed tomography (SPECT) image combined with CT data providing a fusion image. c SPECT/CT image showing significant radiotracer uptake at both sacroiliac joints
diagnosis of SIJ dysfunction. Although some authors have used a single diagnostic block for clinical studies and some advocate the use of confirmatory double blocks using two different local anesthetics with different durations of action [12, 13], the diagnostic value of SIJ blocks remains controversial because of the potential for false-positive and false-negative results. The potential causes of inaccurate blocks include dispersal of the local anesthetic to adjacent pain-generating structures and failure to achieve infiltration throughout the entire SIJ complex. The diagnosis of SIJ dysfunction by imaging remains difficult. In some studies, radiography, CT, and MRI have been used to identify SIJ dysfunction. However, a correlation has not been consistently demonstrated between imaging findings and SIJ dysfunction confirmed by diagnostic SIJ blocks [15]. Bone scans are the procedure of choice for demonstrating stress fractures, infection, or osteoarthritic lesions. Tracer uptake is a function of blood flow and bone matrix turnover. If the osteoarthritic process is active in the cartilage, which is indicative of further destruction, the subchondral bone is also metabolically abnormal either in response to or along with the factor causing the cartilage destruction. A scintigraphy would only indicate positive results in a lesion with an active osteoarthritic process causing subchondral bone turnover. Morphological changes in radiological imaging correlate poorly with symptoms and the progression of degenerative joint disease [16].
However, scintigraphic activity correlates with the symptoms of degenerative joint disease and has a strong negative predictive value for the progression of joint degeneration [17]. Quantitative scintigraphy has poor sensitivity in identifying patients with SIJ dysfunction who respond to anesthetic SIJ injection. Slipman et al. [18] reported that only 12.9 % of patients with SIJ syndrome had an abnormal bone scan appearance, although the specificity was 100 %. Maigne et al. [19] reported that the sensitivity in identifying the SIJ dysfunction as a cause of low back pain was 46.1 % and the specificity was 89.5 %. SPECT scanning is a lesser invasive modality and has superior lesion detection ability compared with planar bone imaging, which is more sensitive than radionuclide bone scanning. The number of detected spinal lesions may increase by 20–50 %, and improvements in sensitivity, specificity, and negative predictive and positive predictive values have been reported [20, 21]. SPECT is also advantageous because of its improved anatomic localization of abnormalities—a feature that has been widely used in patients with spinal pain for the diagnosis of facet joint arthritis. Previous studies have shown that SPECT results correlate well with the response to facet joint steroid injections [22, 23]. However, Dolan et al. [22] reported that only 38 % of patients with facet joint pain diagnosed using facet joint blocks showed positive findings on scans on increased uptake, thus scans are considered to have low
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sensitivity. A multimodality imaging technique combining high-resolution structural images (CT) and functional radionuclide scan images (SPECT) has recently been developed. The advantages of SPECT/CT are also expected to be useful in non-malignant conditions. SPECT has improved sensitivity compared to planar imaging. The high spatial resolution of CT along with the structural information this modality provides enables an accurate assessment of the lesion site. Moreover, the additional information on the shape and structure of the abnormalities improves the specificity of the method. Consequently, specificity is considerably higher with SPECT/CT than with SPECT alone, and SPECT/CT is slightly more sensitive than SPECT alone [24]. If SPECT/CT was to be used only in patients with severe facet joint or SIJ syndrome, the sensitivity would be greatly improved. In terms of SIJ dysfunction, Cusi et al. [4] demonstrated metabolic disturbances in and around the SIJ using hybrid imaging with SPECT/CT in patients with peripartum or traumatic SIJ dysfunction. Their study successfully detected SIJ lesions by finding a specific pattern of metabolic disturbances, and the technique showed a sensitivity of 95 %, specificity of 99 %, positive predictive value of 99 %, and negative predictive value of 94 %.
Conclusion Our findings suggest that the use of SPECT/CT adds value in detecting patients with SIJ dysfunction, who are resistant to conservative treatment. We observed a tendency for a higher tracer accumulation in patients with greater symptom severity who also required more advanced treatment. Thus, we believe that SPECT/CT might be a suitable supplementary diagnostic modality for SIJ dysfunction, and may be useful for predicting the prognosis of this condition. Conflict of interest
None.
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