Sensitivity and specificity of magnetic resonance imaging for axial spondyloarthritis

Diagnosing spondyloarthritis (SpA) early in young patients with inflammatory back pain and normal findings on radiographs of the sacroiliac joints (SIJ) remains a challenge in routine practice. Magnetic resonance imaging (MRI) is regarded as the most sensitive imaging modality for detecting early SpA before the radiographic appearance of structural lesions. The recently published Assessment of SpondyloArthritis International Society classification criteria for axial SpA include for the first time a positive MRI demonstrating sacroiliitis as an imaging criterion indicative of SpA together with at least 1 clinical feature of SpA. A systematic and standardized evaluation of the SIJ in patients with SpA showed that MRI has much greater diagnostic utility than documented previously and allowed a data-driven definition of a positive MRI for SpA. Single MRI lesions suggestive of inflammation can be found in the SIJ and the spine in up to one quarter of healthy controls and young patients with mechanical back pain.     

Psoriatic arthritis: imaging techniques

Imaging techniques to assess psoriatic arthritis (PsA) include radiography, ultrasonography (US), magnetic resonance imaging (MRI), computed tomography (CT) and bone scintigraphy. The radiographic hallmark of PsA is the combination of destructive changes (joint erosions, tuft resorption, osteolysis) with bone proliferation (including periarticular and shaft periostitis, ankylosis, spur formation and non-marginal syndesmophytes). US has an increasing important role in the evaluation of PsA. In fact, power Doppler US is useful mainly for its ability to assess musculoskeletal (joints, tendons, entheses) and cutaneous (skin and nails) involvement, to monitor efficacy of therapy and to guide steroid injections at the level of inflamed joints, tendon sheaths and entheses. MRI allows direct visualization of inflammation in peripheral and axial joints, and peripheral and axial entheses, and has dramatically improved the possibilities for early diagnosis and objective monitoring of the disease process in PsA. MRI has allowed explaining the relationships among enthesitis, synovitis and osteitis in PsA, supporting a SpA pattern of inflammation where enthesitis is the primary target of inflammation. CT has little role in assessment of peripheral joints, but it may be useful in assessing elements of spine disease. CT accuracy is similar to MRI in assessment of erosions in sacroiliac joint involvement, but CT is not as effective in detecting synovial inflammation. Bone scintigraphy lacks specificity and is now supplanted with US and MRI techniques.     

脊柱关节病患者骶髂关节细针活检的病理表现及其临床意义

目的了解骶髂关节(SIJ)炎的病理表现,提高强直性脊柱炎(AS)的早期诊断水平。方法对96例脊柱关节病(SpA)患者的SIJ进行CT导引下的细针活检,3例非SpA死亡病例为对照组。记录临床资料进行分析。结果76例SpA的SIJ存在炎症表现,包括骨髓炎、血管翳形成和炎性细胞浸润,软骨下骨板破坏,软骨变性、破坏,滑膜炎,附着点炎等。其中45例0～Ⅰ级CT下SIJ炎均存在骨髓炎、软骨下骨板炎、软骨变性等改变;0级CT下SIJ炎的滑膜无病理改变,而部分Ⅰ级和所有≥Ⅱ级SIJ炎滑膜可见炎症;软骨破坏和骨化发生率以0～Ⅰ级最低,且仅见于软骨下骨板侧,关节面侧未见破坏;骨质硬化也是0～Ⅰ级最少见;附着点炎仅见于部分≥Ⅱ级SIJ炎;炎性细胞浸润程度Ⅳ级最低。45例0～Ⅰ级CT下SIJ炎的SpA经病理检查诊断为AS;其平均病程显著短于≥Ⅱ级者。结论0级CT下SIJ炎时SIJ已可有炎症存在。SIJ炎可能自骨髓开始,继而血管翳形成,软骨下骨板破坏,软骨变性、破坏,最后纤维化、骨化而导致关节融合。滑膜炎和附着点炎不是SIJ炎的最早改变。病理检查有利于AS的早期诊断和鉴别诊断。     

Imaging of Sacroiliitis

Inflammation of one or both sacroiliac joints is a characteristic feature of patients with spondyloarthropathies (SpA). Sacroiliitis often leads to inflammatory back pain (IBP). IBP and asymmetric peripheral arthritis of the lower limbs are the main clinical symptoms and criteria for classification and diagnosis of SpA in which sacroiliac joints are uni- or bilaterally affected with an intensity ranging from mild to very severe inflammation resulting in partial or complete ankylosis Sacroiliitis is a very frequent feature of undifferntiated SpA. In ankylosing spondylitis (AS) inflammation in the axial skeleton occurs rarely in the absence of sacroiliitis. Objective evidence of sacroiliitis obtained by imaging procedures, especially x-rays, has always been part of diagnostic and classification criteria for AS. This is in contrast to spinal radiography which, however, has been recently included in a core set of outcome items to be assessed in clinical studies. In early and acute stages of sacroiliitis the diagnosis can be difficult because conventional radiographs - which are known to have considerable intra- and interobserver variability - may be normal. Since IBP is not a specific indicator of sacroiliitis there is need for valuable imaging techniques. Scintigraphy lacks specificity. Computed tomography (CT) is a very good method to demonstrate already established bony changes and magnetic resonance imaging (MRI) has the advantage of combining a good visualisation of the complicated anatomy of the sacroiliac joint with the ability to localise different degrees of inflammation and oedema and prove a possible spread to muscles as it occurs in septic sacroiliitis, an important differential diagnosis. Received: 3 March 1999 / Accepted: 3 March 1999     

Very early spondyloarthritis: where the inflammation in the sacroiliac joints starts

Involvement of the sacroiliac joints (SIJ) is a major and characteristic feature of the spondyloarthritides (SpA). In early ankylosing spondylitis and undifferentiated SpA (uSpA) sacroiliitis is the most common early clinical finding and the presumed first manifestation of the disease. Magnetic resonance imaging has proved useful for visualising inflammation in the SIJ in adults and children. Recently, initial localisation of the inflammation in the SIJ has been described in some detail, but it has not been completely defined to date--either in imaging or in histopathological studies. This is mainly owing to the lack of data in very early disease and the lack of follow up studies. Here we present a patient with early disease, which may augment our understanding of this stage of SpA.     

Imaging of the seronegative spondyloarthropathies

The group of seronegative spondyloarthropathies consists of ankylosing spondylitis, psoriatic arthritis, Reiter’s disease, enteropathic spondylitis, and a fifth entity known as undifferentiated spondyloarthropathy. All of these diseases share common clinical and radiographic features with characteristic involvement of the sacroiliac joints, spine, and to various degrees, the peripheral joints. Although plain radiographs are the first line of imaging investigation, they are often insensitive for demonstrating the early changes of sacroiliitis, an important feature for establishing the early diagnosis of seronegative spondyloarthropathy. Other imaging modalities, including conventional tomography, bone scintigraphy, and computed tomography, have improved visualization of inflammatory changes at the sacroiliac joints. This article will review these modalities and emphasize the role of magnetic resonance imaging. By directly imaging changes in the synovium, articular cartilage, and subchondral bone, findings on magnetic resonance imaging are the most sensitive and specific for sacroiliitis and other changes in the axial skeleton. Its role and that of ultrasound in the assessment of the peripheral joints will also be highlighted.     

Incidental computed tomography sacroiliitis: clinical significance and inappropriateness of the New York radiological grading criteria for the diagnosis

The clinical implications of computed tomography (CT) detected sacroiliac joint (SIJ) changes compatible with sacroiliitis has been rarely discussed in the literature. The aim of the present study was to describe prevalence and clinical correlations of sacroiliitis, noted incidentally by abdominal CT in patients referred for non-musculoskeletal complaints, utilizing the New York radiological grading criteria for reference. Five hundred ninety-eight CT scans of the abdomen of patients 18–55 years old, performed at a community medical center, were prospectively examined for the presence of imaging changes consistent with sacroiliitis. Patients with the evidence of bilateral sacroiliitis of grade ≥2 were interviewed and underwent a rheumatologic examination. Twenty-two patients (13 females) were enrolled. Only eight patients (six males) had a history and clinical picture compatible with previously undiagnosed axial spondyloarthritis (SpA). Only the presence of erosions/joint space irregularity and/or inhomogeneous osseous sclerosis around SIJs on CT correlated with the clinical diagnosis of axial SpA. Dense homogenous osseous sclerosis was unrelated to axial SpA and was seen almost exclusively in females. The prevalence of incidental CT sacroiliitis is low, while the New York radiological grading criteria for diagnosing sacroiliitis may be inappropriate for CT imaging. CT noted erosions of the SIJ appear to be a reliable diagnostic sign of sacroiliitis, while the significance of the osseous sclerosis, seen on CT adjacent to SIJs requires better understanding.     

Studying patients with inflammatory back pain and arthritis of the lower limbs clinically and by magnetic resonance imaging: many, but not all patients with sacroiliitis have spondyloarthropathy.

OBJECTIVE: Clinical and magnetic resonance imaging (MRI) data of 170 consecutive patients with inflammatory back pain (IBP) and/or oligoarthritis of the lower limbs were evaluated in a retrospective study. The aim was to determine the frequency of sacroiliitis and spondyloarthropathy (SpA) in this population, and to assess the significance of HLA B27 measurements for diagnosis in early disease. METHODS: Pelvic X-rays were performed in all IBP patients and dynamic MRI of the sacroiliac joints in patients with IBP who had indefinite results on sacroiliac X-rays (n = 32). RESULTS: European Spondyloarthropathy Study Group criteria for SpA were fulfilled by 106/170 patients (62.4%); eight additional patients had symptoms suggestive of SpA (4.7%). The most frequent SpA subset was undifferentiated SpA (uSpA), diagnosed in 46/106 patients (43.4%). Sacroiliitis was detected by MRI in 21/32 patients with IBP and unclear X-rays (65.6%). Of those, 14 were diagnosed as SpA and seven females with moderate unilateral sacroiliitis, but no features of SpA, also not on follow-up (at least 1 yr), were classified as undifferentiated sacroiliitis (US). Ten of the 14 SpA (71.4%) and none of the seven US patients were HLA B27 positive. CONCLUSION: HLA B27 positivity in IBP patients with MRI-proven sacroiliitis positively predicts SpA. uSpA is a frequent SpA subset. There are HLA B27-negative non-SpA patients with moderate unilateral sacroiliitis whom we propose to be classified as US.     

The investigation of sacroiliitis with different imaging techniques in spondyloarthropathies

Purpose The aim of this study was to compare the value of different imaging techniques in spondyloarthropathy (SpA) patients with inflammatory low back pain.Patients and methods We evaluated 54 patients who fulfilled the European spondyloarthropathy classification criteria and had inflammatory low back pain. They were subdivided into two groups according to changes on plain radiography rated on a 0–4 scale according to modified New York criteria. Group A patients had at least grade-2 unilateral or bilateral changes in the sacroiliac (SI) joints, whereas group B included patients with radiologic changes not exceeding grade 0–1. Quantitative SI scintigraphy and magnetic resonance imaging (MRI) were performed to investigate the value of these techniques to the diagnosis of sacroiliitis, and the sacroiliac joint:sacrum uptake ratios were calculated. Scintiscanning was done in 80 healthy subjects to define the normal range.Results The sensitivities of plain radiography, quantitative SI scintigraphy, and MRI were 61%, 55%, and 89%, respectively, among the patients with SpA. MRI and quantitative SI scintigraphy detected sacroiliitis in 97% and 49% of group A, respectively. In group B, these results were 76% and 66%, respectively.Conclusion Magnetic resonance imaging is the most sensitive method for detecting acute or chronic changes in SpA patients with histories of inflammatory low back pain and normal or indeterminate findings on plain radiographs.     

Magnetic resonance imaging in rheumatic disorders of the spine and sacroiliac joints

OBJECTIVE: To review the value of magnetic resonance imaging (MRI) in diagnosis and evaluation of rheumatic diseases of the spine and sacroiliac joints. METHODS: A review of the literature on MRI of the spine and sacroiliac joints in rheumatoid arthritis (RA), ankylosing spondylitis (AS), infectious spondylodiscitis, infection of the sacroiliac joint (SIJ), gout, calcium pyrophosphate deposition disease, nontraumatic vertebral compression fractures, insufficiency fracture of the sacrum, avascular necrosis of the vertebral body, sarcoidosis, and Paget's disease was performed. The reports were obtained from a Medline search. RESULTS: In RA, AS, and crystal deposition disease, synovial tissue, atlantoaxial and subaxial subluxations, crystal deposition, and neurologic compromise can be adequately diagnosed with MRI of the cervical spine. Studies on MRI of SIJs in AS indicate that MRI enables early diagnosis of sacroiliitis. In most cases of infectious spondylodiscitis, avascular necrosis of the vertebral body, nontraumatic vertebral compression fractures, and insufficiency fractures of the sacrum characteristic findings on MRI suggest the correct diagnosis. Moreover, soft tissue abnormalities and neurologic compromise can be visualized. In infection of the SIJ, MRI shows findings suggesting an inflammatory process. In Paget's disease, MRI does not provide additional information as compared with plain radiography (PR) or computed tomography (CT). CONCLUSION: In evaluation of spinal and SIJ abnormalities in many rheumatic diseases, MRI, in addition to PR, can replace conventional tomography, CT, and myelography. Moreover, MRI can visualize soft tissue abnormalities and neurologic compromise without use of intrathecal contrast.     

High frequency of inflammatory back pain and other features of spondyloarthritis in patients with rheumatoid arthritis

The aim of this study was to investigate the frequency of patients with rheumatoid arthritis (RA) who have inflammatory back pain (IBP) and meet the existing classification criteria for ankylosing spondylitis (AS) and spondyloarthritis (SpA). We included 167 patients fulfilling the ACR 1987 revised criteria for RA. After obtaining a medical history and performing a physical examination, standard pelvic X-rays for examination of the sacroiliac joints (SIJ) were ordered in all patients. A computed tomography (CT) or magnetic resonance imaging (MRI) of SIJ was performed in patients with suspected radiographic sacroiliitis and MRI of SIJ in those who have IBP but no radiographic sacroiliitis. IBP was defined according to both Calin and experts’ criteria. The modified New York (mNY) criteria were used to classify AS, both ESSG and Amor criteria for SpA and ASAS classification criteria for axial SpA. There were 135 female and 32 male patients with a mean age of 54.8 years. The mean disease duration was 9.8 years. RF was positive in 128 patients (79.2 %) and anti-CCP in 120 patients (81.1 %). Twenty-eight patients with RA (16.8 %) had IBP (Calin criteria), and four (2.4 %) had radiographic sacroiliitis of bilateral grade 3. Three patients (1.8 %) fulfilled the mNY criteria for AS, 31 (18.6 %) ESSG and 26 (15.6 %) Amor criteria for SpA. Nine patients (five with MRI sacroiliitis) (5.3 %) were classified as having axial SpA according to new ASAS classification criteria. This study suggests that the prevalence of SpA features in patients with RA may be much higher than expected.     

MRI abnormalities of sacroiliac joints in early spondylarthropathy: a 1-year follow-up study

OBJECTIVE: To describe changes in chronic and acute magnetic resonance imaging (MRI) abnormalities of the sacroiliac joints (SIJs) in early spondylarthropathy (SpA), and to associate these findings with computed tomography (CT), X-ray, and clinical findings during a 1-year follow-up. METHODS: Thirty-four patients, 20 males and 14 females, median age 27 years, with inflammatory low back pain (median 23 months) were included. MRI, CT, and X-ray, as well as clinical and laboratory tests were performed. After a follow-up period of 1 year (median 377 days) the examinations were repeated, and the findings were correlated. RESULTS: MRI and CT changes resulting from SIJ destruction increased significantly during follow-up, and the two modalities were significantly correlated. For the MRI findings of inflammatory activity, only bone marrow oedema decreased significantly. An increase in the Schober test was the only clinical examination that changed significantly. CONCLUSION: In early SpA, MRI can detect significant inflammatory and destructive changes of the SIJs over a 1-year follow-up period, in spite of minimal changes in the clinical parameters. The MRI changes in inflammatory activity are not detectable by CT and X-ray examinations. Thus, MRI may be a sensitive method, without known risks, for early diagnosis and for following disease progression in SpA.     

Anatomic structures involved in early- and late-stage sacroiliitis in spondylarthritis: a detailed analysis by contrast-enhanced magnetic resonance imaging

OBJECTIVE: To localize inflammatory and chronic changes to defined areas in the sacroiliac joints in patients with early-stage compared with late-stage spondylarthritis (SpA), using magnetic resonance imaging (MRI). METHODS: Using MRI, 93 patients with SpA and inflammatory back pain who had radiographs of the sacroiliac joints were examined, comprising 31 patients with ankylosing spondylitis (AS) and 62 with other SpA subsets, including 48 with undifferentiated SpA (uSpA). MRI was performed using T1-weighted, T2*-weighted, STIR, and dynamic contrast-enhanced (gadolinium diethylenetriaminepentaacetic acid) sequences. Two readers retrospectively analyzed the images by differentiating 9 areas of the sacroiliac joints: the ventral and caudal joint capsule, cavum, subchondral bone, bone marrow, ligament entheses, and ligaments; the sacral and iliac sides were tabulated separately. RESULTS: By MRI, sacroiliitis was more often bilateral in AS (84%) than in uSpA (48%) (P = 0.01). Inflammatory changes were found in a mean +/- SD 4.7 +/- 2.9 regions/joint, with involvement of 4.5 +/- 3.2 regions in early disease versus 5.2 +/- 2.3 regions in late disease (P not significant [NS]). Involvement of the iliac side of the sacroiliac joints was found to be more frequent than the sacral side in early disease (58% versus 48%; P < 0.01) as compared with that in late disease (58% versus 63%; P NS). The dorsocaudal parts of the synovial joint and the bone marrow were the most frequently inflamed structures in early disease (P < 0.001 for ventral versus dorsal joint capsule). In contrast, involvement of the entheses was more common in advanced disease (early 43% versus late 86%; P < 0.001). Similarly, the ligaments were more frequently involved in the late stages (early 26% versus late 40%; P = 0.06). Both patterns of bone marrow inflammation (focal and diffuse) were observed in equal frequencies in early and late disease (17% and 42% versus 26% and 43%, respectively; P NS). HLA-B27-positive patients (n = 80) had more entheseal involvement than did HLA-B27-negative patients (n = 13) (60% versus 39%; P = 0.05). HLA-B27-negative patients had a shorter disease duration (2.2 years versus 4.4 years; P = 0.05) and were more often female (62%; P = 0.02). When all pathologic changes were assessed, the STIR sequence (performed in 62 patients) was less sensitive than the contrast-enhanced sequences in that it was not able to show all relevant changes in 27% of these patients (n = 17), failing to reveal inflammation of the cavum in 15 patients and of the bone marrow and joint capsule in 1 patient each. CONCLUSION: As visualized by MRI, sacroiliitis in SpA is characterized by involvement of different joint structures. Whereas the iliac and the sacral side of the sacroiliac joints are almost equally affected, the dorsocaudal synovial part of the joint is involved significantly more often than the ventral part, especially in early disease. Sacroiliac enthesitis is not a special feature of early sacroiliac inflammation.     

磁共振成像对早期骶髂关节炎的诊断价值研究

目的了解磁共振成像(MRI)在早期骶髂关节炎诊断中的意义。方法对82例炎症性腰背痛或不对称性下肢滑膜炎患者的骶髂关节CT扫描、MRI平扫以及病理检查结果进行分析比较。结果45例病理证实的早期骶髂关节炎中,69%(31/45)MRI显示骶髂关节存在炎症性改变。但17例病理检查骶髂关节无炎症性改变者,也有59%(10/17)MRI表现不同程度骶髂关节炎症性改变。以病理检查结果为依据,MRI对早期骶髂关节炎诊断的敏感性、特异性分别为69%和41%。结论MRI对早期骶髂关节炎的诊断有一定的敏感性,但特异性不高,临床应用要慎重考虑。     

Atlas of MRI findings of sacroiliitis in pediatric sacroiliac joints to accompany the updated preliminary OMERACT pediatric JAMRIS (Juvenile Idiopathic Arthritis MRI Score) scoring system: Part I: Active lesions

Magnetic resonance imaging (MRI) is an increasingly important tool for identifying involvement of the sacroiliac joints (SIJ) in juvenile idiopathic arthritis (JIA). The key feature for diagnosing active sacroiliitis is bone marrow edema (BME), but other features of active arthritis such as joint space inflammation, inflammation in an erosion cavity, capsulitis and enthesitis can be seen as well. Structural changes may also be seen. Systematic MRI assessment of inflammation and structural damage may aid in monitoring the disease course, choice of therapeutics and evaluating treatment response. In this pictorial essay, we illustrate normal MRI findings and growth-related changes of the SIJ in the pediatric population, as well as the different MRI features of SIJ inflammation. This atlas demonstrates fundamental MRI disease features of active inflammation in a format that can serve as a reference for assessing SIJ arthritis according to the updated preliminary JAMRIS (Juvenile Idiopathic Arthritis MRI Score) scoring system proposed by the MRI in JIA working group of Outcome Measures in Rheumatology and Clinical Trials (OMERACT). The atlas is intended to be read in conjunction with its companion Part 2, Structural Lesions.     

Evaluation of acute and chronic MRI features of sacroiliitis in asymptomatic primary hyperparathyroid patients

Asymptomatic primary hyperparathyroidism (PHPT) is characterized with autonomous overproduction of parathyroid hormone without signs or symptoms associated with hyperparathyroidism. Before symptoms become obvious, PHPT may affect structures like sacroiliac joints, which consist of bone. So, in the asymptomatic PHPT patients, structural and inflammatory changes in sacroiliac joints may lead to confusion during diagnosis workup of axial spondyloarthropathy. In this study, we evaluated active and chronic sacroiliac magnetic resonance imaging (MRI) changes relevant to sacroiliitis in the patients with asymptomatic PHPT and interpreted bone marrow edema within the scope of Assessment of SpondyloArthritis International Society–Outcome Measures in Rheumatology Clinical Trials (ASAS-OMERACT) criteria. Forty-nine patients with asymptomatic PHPT, 26 patients with newly diagnosed axial spondyloarthropathy (SpA), and 37 healthy controls were enrolled. All subjects were evaluated by sacroiliac MRI for four active (bone marrow edema, enthesitis, capsulitis, and synovitis) and four chronic (subchondral sclerosis, subchondral/periarticular erosions, periarticular fat deposition, and bony bridges/ankylosis) lesions relevant to sacroiliitis. Bone marrow edema compatible with ASAS-OMERACT active sacroiliitis criteria in sacroiliac MRI was fulfilled by 16.3 % (8/49) of the asymptomatic PHPT patients which was similar with controls but statistically lower than axial SpA. Moreover, asymptomatic PHPT patients and controls were similar for other chronic or active MRI findings. Also, we detected lower frequency of all other MRI findings, except enthesis, in asymptomatic PHPT patients according to axial SpA. Acute inflammatory including bone marrow edema fulfilling ASAS-OMERACT active sacroiliitis criteria and chronic structural sacroiliac lesions relevant to sacroiliitis in MRI were detected in asymptomatic PHPT similar frequency with controls but as expected, lower than axial SpA. But, these findings could not be attributed to excessive secretion of parathyroid hormone.     

Imaging in spondyloarthropathies

Seronegative spondyloarthropathies comprise a group of inflammatory arthritides, which consists of ankylosing spondylitis, psoriatic arthritis, reactive arthritis (Reiter’s syndrome), enteropathic arthritis, and undifferentiated spondyloarthropathy. All of them share common laboratory, clinical, and imaging findings, with characteristic involvement of the sacroiliac joints, spine, and, to various degrees, peripheral joints. For many years, conventional radiography was the mainstay for definitive diagnosis of sacroiliitis and for follow-up of the anatomic changes in the spine, peripheral joints, and entheses. Conventional radiographs remain the imaging investigation of choice; however, they are unable to detect early inflammatory changes of sacroiliitis, which are important for establishing a diagnosis without delay. Other imaging modalities, such as computed tomography, bone scintigraphy, magnetic resonance imaging, and ultrasonography have improved the capabilities of detecting early disease and became useful adjuncts to plain films. In addition, they also have enabled more accurate detection of pathology at various anatomic sites of the musculoskeletal system predominantly involved in spondyloarthropathies. This article will review and highlight the role of each of these modalities in the assessment of the axial and peripheral skeleton in seronegative spondyloarthropathies.     

Imaging in axial spondyloarthritis: Changing concepts and thresholds

Imaging is key to recognition of axial spondyloarthritis (SpA) because clinical and laboratory examinations have limited diagnostic utility. Only MRI can capture both inflammation and bone remodeling by simultaneous depiction of active and structural lesions and their anatomic location. Bone marrow edema of limited extent on the sacroiliac joint (SIJ) MRI is often nonspecific and should be interpreted along with the clinical context. Contextual interpretation of the SIJ lesion signature viewed simultaneously on fluid- and fat-sensitive MRI sequences enhances confidence in the recognition of disease. A critical re-appraisal of using pelvic radiographs in clinically suspected early spondyloarthritis is warranted because of substantial limitations. In health care settings with low threshold access to advanced imaging, MRI is the preferred modality in early SpA. CT has recently advanced spinal outcome research, but substantial radiation exposure in young patients with spondyloarthritis and limited evidence on its relevance in practice do not advocate its use in daily routine.     

Sacroiliac joints: osteoarthritis or arthritis

One of the most challenging aspects of treating the sacroiliac joint (SIJ) pain is the complexity of diagnosis. Imaging methods have gained importance for the diagnosis of SIJ diseases. CT and MR exams had equal efficacy superior to radiography in staging structural changes in the SIJ due to osteoarthritis or sacroiliitis. The diagnosis of spondyloarthropaty can be delayed for several years using certain radiography studies. MR imaging reveal early cartilage changes and active inflammatory changes in the subchondral bone and surrounding ligaments in spondyloarthropaties, as well as subperiosteal and transcapsular yuxtaarticular infiltrations characteristic of septic sacroiliitis, which could not be found by either CT of radiography. T1-WI with fat suppression (FS) and STIR images improve the demonstration of erosions and inflammatory changes respectively, on MR studies. Additional T1-FS after i.v. contrast has proven valuable in demonstrating the extension of inflammatory changes and abscesses in septic sacroiliitis, and in spondyloartropaties may be useful although this is debatable. Scintigraphy gives high sensibility only in early inflammatory changes and low specificity for the diagnosis of sacroiliitis due to high bone turnover in the SIJ, although specific radioprobes are useful in confirming the septic etiology and evaluating additional foci. This complex joint of very limited mobility shows a lot of structural variations and some anatomical degenerative changes due to age, which are necessary to know to an adequate image interpretation and diagnosis of disease.     

骶髂关节病变病理学与影像学诊断的相关性

目的通过了解骶髂关节炎病理特点,并以病理结果为标准,探讨病理表现与放射性核素单光子发射计算机断层成像术(single-photon emission computed tomography,SPECT)、磁共振显像(magnetic resonance imaging,MRI)、计算机断层扫描(computed tomography,CT)、X线等影像学检查的关系。方法对中轴型脊柱关节炎患者进行CT引导下骶髂关节(sacroiliac joint,SIJ)穿刺,所得组织进行病理检查,并同时行SIJ的SPECT、MRI、CT和X线检查,按组织病理结果分为SIJ炎组和无炎性反应组。结果 36例患者获得组织有软骨、软骨下骨板、关节滑膜、骨髓、肌腱或韧带附着点等。获得率以软骨为最高,继以软骨下骨板、关节滑膜、骨髓和韧带附着点,各占92%、83%、75%、72%、22%;其中28例(2836,78%)患者SIJ炎病理变化包括软骨(93%)和软骨下骨板改变(75%)、滑膜炎(64%)、骨髓炎(46%)、附着点炎(32%),8例(22%)未发现有SIJ炎改变。MRI示29例(81%)患者共56个SIJ可见不同程度的异常信号改变,软骨线改变、软骨下骨板改变、骨髓水肿、脂肪沉积、骨质硬化分别为82%、71%、65%、59%、76%;SPECT示29例(81%)共52个SIJ可见骶髂关节感兴趣区的放射性比值有不同程度的升高,23例(64%)CT阳性,19例(53%)X线阳性。以病理结果为标准,SPECT、MRI、CT、X线的阳性预测值分别为89.6%、93.1%、95.6%、94.7%,敏感性分别为92.8%、96.4%、73.3%、64.2%,特异性分别62.5%、75.0%、87.5%、87.5%。4种诊断方法的受试者工作特征曲线下面积分别为0.79、0.84、0.83、0.76。结论病理检查是诊断Sl J炎和活动性炎性反应的主要方法。MRI和SPECT的相互补充,能提高骶髂关节活动性炎症的敏感性和特异性。MRI和SPECT的诊断价值与CT和X线相当,并可通过对炎症的活动度进行量化,有利于随访和疗效的评价,是诊断SIJ炎重要的辅助手段。