MRI of the sacroiliac joints: what to report and its pitfalls

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1 MRI of the sacroiliac joints: what to report and its pitfalls Poster No.: C-1920 Congress: ECR 2016 Type: Educational Exhibit Authors: J. Goncalves, A. Y. Aihara, C. Longo, H. Guidorizzi, P. Aguiar, A. Rosenfeld, F. B. M. D. Ferreira, F. Cardoso ; BRASÍLIA/BR, São Paulo/BR, São Paulo, São Paulo/BR, SAO PAULO, SP/BR Keywords: Musculoskeletal system, Musculoskeletal joint, Musculoskeletal bone, MR, Education, Normal variants, Education and training DOI: /ecr2016/C-1920 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 21

2 Learning objectives MRI is the imaging modality of choice for the investigation of sacroiliac pain, playing a central role in detecting disease activity even in the most advanced stages of the disease, as in ankylosis. More importantly MRI has the ability to quantify inflammatory activity, which makes it ideal for monitoring disease activity and therapeutic management of sacroiliitis. Finally, the main objective of this study is to discuss the radiological signs of sacroiliitis and its pitfalls in MRI. Background Spondyloarthropathy comprises a group of chronic inflammatory rheumatic diseases, including ankylosing spondylitis, reactive arthritis (Reiter syndrome), arthritis or spondylitis associated with inflammatory bowel disease, and psoriatic arthritis, as well as undifferentiated spondyloarthritis. [1] This group of diseases can manifest with axial spondyloarthropathies and/or peripheral arthritis. The sacroiliac joints are involved in most cases of axial spondyloarthropathy, with sacroiliitis usually being the first manifestation. This is diagnosed by ASAS criteria that are applied to patients with at least a 3month history of back pain who are less than 45 years old at the onset of pain. [2,3] (Fig 1) Normal Anatomy The sacroiliac joint has two components, a fibrous and a cartilaginous (anterior-inferior) component. Posterior to the sacroiliac joint we find the strong sacroiliac ligaments, which are not intra-articular (posterior). The cartilaginous component (headset) is an atypical synovial joint. The interosseous ligaments that form the ligament portion (syndesmosis) consist of small and resistant bands that fall into the spines bets. [3] ( Figs 2 and 3) Page 2 of 21

3 MR Imaging Technique MRI has a key role in accessing the presence of acute and chronic signs of disease. Protocol Two perpendicular ( axial and coronal oblique) planes are required. [7] The entire sacral bone should be included in the study, from its leading edge to the trailing edge. The basic protocol comprises (Figs 4 and 5): Coronal oblique Fast spin-echo (FSE) T1 Coronal oblique STIR or T2 Fat Sat Axial oblique STIR or T2 Fat Sat Axial oblique T1 Fat Sat Coronal oblique T1 Fat Sat after administration of gadolinium-based contrast Axial oblique T1 Fat Sat after administration of gadolinium-based contrast Images for this section: Page 3 of 21

4 Fig. 1 Page 4 of 21

5 Fig. 2: Gross specimen illustrates the normal anatomy of the sacroiliac joint: anteriorinferior part (synovial cartilage - yellow) and upper-posterior (ligament - in blue). Page 5 of 21

6 Fig. 3: Axial images T1 and T2 Fat sat of a normal sacroiliac joint illustrating the ventral portion and the lower two thirds. Page 6 of 21

7 Fig. 4: Diagram illustrates the cutting plans of the MRI protocol. Page 7 of 21

8 Fig. 5: Sagittal and axial T1 images illustrates the cutting plans of the MRI protocol. Page 8 of 21

9 Findings and procedure details We reviewed cases mentioned in the literature and seen in our daily clinical practice. We set up a list of findings to be checked in the evaluation of the sacroiliac joints. [1] These are changes that we should look for when reading a sacroiliac joint MRI. I. Active inflammatory lesions (STIR / post-gadolinium T1): Synovitis, capsulitis, enthesitis (Fig 6): Synovitis can only be differentiated from joint fluid after contrast media administration and is manifested as an enhancement of the synovial joint. Capsulitis manifests itself with pericapsular edema and contrast enhancement. Enthesitis manifests as hyperintense signal on STIR and Fat Sat T2 - weighted images and contrast enhancement Fat Sat T1 weighted images. Bone marrow edema (Fig 7): The bone marrow edema manifests with high signal intensity on Fat Sat FSE T2 - weighted or STIR images and enhancement on postgadolinium Fat Sat FSE T1 weighted images (osteitis). It usually has periarticular location and can be associated with local bone erosions. II. Chronic inflammatory lesions ( normally T1): Fat deposition (Fig 8): Fat deposits usually appear hyperintense on T1- weighted images. Subchondral sclerosis and irregularity (Figs 9 and 10): The subchondral sclerosis manifests itself as areas of low signal in all sequences and extends at least 5 mm from the joint space. Ankylosis (Fig 11): Ankylosis is a result of pathological fusion of bones. These findings help make the diagnosis of sacroiliitis, but one critical role in imaging is to detect disease activity, because it can change the treatment regimen. Disease activity, currently, can only be diagnosed when we see osseous edema /osteitis (According to the new ASAS criteria for axial spondyloarthropathy). Page 9 of 21

10 We should keep in mind that not all subchondral edema or hiperintensity is related to sacroiliitis activity, and can be seen in degenerative disease, mechanical stress and pitfalls that mimic edema. The other inflammatory signs (synovitis, capsulitis, enthesitis) help us to be more confident on the diagnosis, but are not single criteria to define activity. Ex: finding only capsulitis does not allow us to suggest disease activity according to ASAS. What helps us is that usually these findings are accompanied by osseous edema /osteitis. Chronic changes are also important to detect because it makes the diagnosis of sacroiliits more confident, and because it means some structural damage has already ocurred. So the prognosis of the articulation is poorer. Ex 1: if you find ankylosis, there realy is not much to do. Ex 2: edema with no structural changes has good prognosis but edema with erosions, sclerosis, fat deposition and bony bridges probably does not have a good prognosis. We also have to remember that there are common pitfalls that can simulate sacroiliitis. Some pitfalls in the study of these joints by magnetic ressonance imaging are: [2,8] Ventral sacroiliac ligament (Figs 12 and 13) Dorsal-ventral transition vessels. (Figs 12 and 13) Dorsal-ventral transition irregularities (Fig 14) Periradicular cysts (Fig 15) Intraosseous ligament simulating bone island (Fig 15) Images for this section: Page 10 of 21

11 Fig. 6: Axial T2 Fat sat image of a sacroiliac joint whit synovitis ( white arrow) and enthesitis ( black arrow.) Page 11 of 21

12 Fig. 7: Axial T2 Fat sat image of a sacroiliac joint showing bilateral bone medular edema. Page 12 of 21

13 Fig. 8: Axial T1 image of a sacroiliac joint showing bilateral fat deposits Fig. 9: Axial T2 Fat sat images of a sacroiliac joint showing the subchondral sclerosis and irregularity ( blue arrows). Page 13 of 21

14 Fig. 10: Coronal CT image of a sacroiliac joint showing the subchondral sclerosis and irregularity. Fig. 11: Coronal and axial T1 images of sacroiliac joints showing bilateral ankylosis. Page 14 of 21

15 Fig. 12: Axial T2 Fat Sat image illustrating one of the pitfalls in the evaluation of the sacroiliac joints: ventral sacroliliac ligament (red arrow) and the dorsal-ventral transition vessels ( green arrow). Fig. 13: Axial T2 Fat Sat image illustrating one of the pitfalls in the evaluation of the sacroiliac joints: ventral sacroliliac ligament (red arrow) and the dorsal-ventral transition vessels ( green arrow). Page 15 of 21

16 Fig. 14: Coronal T2 Fat Sat image illustrating one of the pitfalls in the evaluation of the sacroiliac joints: dorsal-ventral transition irregularities (arrow). Fig. 15: Coronal T2 Fat Sat image illustrating one of the pitfalls in the evaluation of the sacroiliac joints: dorsal-ventral transition irregularities (arrow). Page 16 of 21

17 Fig. 16: Coronal T2 Fat Sat image illustrating one of the pitfalls in the evaluation of the sacroiliac joints: dorsal-ventral transition irregularities (arrow). Page 17 of 21

18 Conclusion The use of the checklist presented and knowledge of the various pitfalls in the study of sacroiliitis helps the radiologist avoid diagnostic errors. Look for the 4 acute (synovitis, capsulitis, enthesitis, bone marrow edema) and the 4 chronic ( fat deposition, subchondral sclerosis, erosions, ankylosis) signs of disease. Differentiate it from other pathologies (degenerative disease, mechanical stress, infectious sacroiliitis and condensing osteitis of the iliac). (Figs 17 21) Remember common pitfalls that may simulate disease. Images for this section: Fig. 17: Coronal oblique T1 (a), coronal olbique T2 Fat Sat (b), axial oblique T1 (c) and axial oblique T2 fat sat (d): Chronic signs of bilateral sacroiliitis, characterized by reduction of the articular space, fat deposition and bone ankylosis outbreaks. There is no evidence of bone edema or osteitis to indicate current disease activity. Page 18 of 21

19 Fig. 18: This sequence of RM cuts illustrate one of the differential diagnosis of inflammatory sacroiliiti: infectious sacroiliitis. Page 19 of 21

20 Fig. 19: This sequence of RM cuts illustrate one of the differential diagnosis of inflammatory sacroiliitis: degenerative changes with anterior osteophytes( red circle). Fig. 20: An example of condensing osteitis of the iliac. Fig. 21: An example of condensing osteitis of the iliac whit bilateral and symmetric subchondral sclerosis of the iliac ( red circles). Page 20 of 21

21 Personal information References 1. Maria Navallas, MD; Jesús Ares, MD; Brigitte Beltrán, MD; Maria Pilar Lisbona, MD; Joan Maymó, MD; Albert Solano, MD. Sacroiliitis Associates whit Axial Spondyloartropathy: New Concepts and Latest Trends. Radiographics 2013; 33: Sieper J, Rudwaleit M, Baraliakos X, et al. The Assessment of SpondyloArthritis international Society (ASAS) handbook: a guide to assess spondyloarthritis. Ann Rheum Dis 2009;68(suppl 2):ii1-ii44. # 3. Puhakka KB, Melsen F, Jurik AG, Boel LW,Vesterby A, Egund N. MR imaging of the normal sacroiliac joint with correlation to histology. Skeletal Radiol 2004;33(1): # 4. Resnick D. Articular anatomy and histology. In: Resnick D, ed. Diagnosis of bone and joint disorders. Philadelphia, Pa: Saunders, 2002; Prassopoulos PK, Faflia CP,Voloudaki AE, Gourt- soyiannis NC. Sacroiliac joints: anatomical variants on CT. J Comput Assist Tomogr 1999;23(2): Hanly JG, Mitchell MJ, Barnes DC, Macmillan L. Early recognition of sacroiliitis by magnetic resonance imaging and single photon emission computed tomography. J Rheumatol 1994;21(11): # 7. Puhakka KB, Jurik AG, Egund N, et al. Imaging of sacroiliitis in early seronegative spondylarthropathy: assessment of abnormalities by MR in comparison with radiography and CT. Acta Radiol 2003;44(2): # 8. Rudwaleit M, Jurik AG, Hermann KG, et al. Defining active sacroiliitis on magnetic resonance imaging (MRI) for classification of axial spondyloarthritis: a consensual approach by the ASAS/OMERACT MRI group. Ann Rheum Dis 2009;68(10): # Page 21 of 21