MSK Imaging in Rheumatology

As Wilhelm Roentgen remarked, “We shall see what we shall see. We have the start now; the developments will follow in time.” Over the past few decades, imaging of rheumatologic diseases has developed spectacularly, particularly due to the constant technological improvements of cross-sectional modalities and more importantly new developments in immunology, molecular biology, genetics, as well histopathology of these disorders and even anatomy of selected joints.[1] Such achievements have increased our understanding of pathologic phenomena underlying the images, initiated discussions on the proper interpretation of features or even the naming of some findings, even diseases,[2] [3] and have increased our ability to diagnose earlier and to treat patients with disease-modifying drugs and biologics.

Increasing emphasis at both the clinical and diagnostic levels has especially been placed on the early diagnosis in patients with inflammatory arthropathies. However, in the very early stages of these diseases, in adults and children alike, making a specific diagnosis remains challenging because patients often present with nonspecific musculoskeletal symptoms. Conversely, even clinically evident and more advanced stages of inflammatory arthritides frequently remain difficult to differentiate from other noninflammatory arthropathies. In patients with subclinical synovitis or bone marrow edema, the role of radiologic imaging is still unclear, and the same issue applies to patients in remission.[4] [5]

This issue of Seminars in Musculoskeletal Radiology offers 10 articles detailing the imaging features of a wide variety of rheumatologic disorders. They were authored or coauthored by internationally recognized authorities, most of them members of the Arthritis Subcommittee of the European Society of Skeletal Radiology and true experts in their subspecialties.

This issue begins with an article by Reijnierse and colleagues discussing MRI manifestations of rheumatoid arthritis (RA) in the peripheral joints and the spine. The authors portray the clinical background of RA, current treatment strategies, and the role of MRI in patient management, all of them a direct reflection of the dynamic changes in the way rheumatology and imaging in rheumatology are practiced today, in close cooperation between different specialities.

The major trust factors when looking at the subject of juvenile inflammatory arthropathies written by Sudoł-Szopińska et al is directed toward the role of a variety of imaging techniques in the evaluation of juvenile idiopathic arthritis and other rare connective tissue diseases such as juvenile scleroderma, juvenile dermatomyositis, juvenile lupus erythematosus, and CRMO. The authors focus on the presentation of the main imaging features coupled with a concise review of key pathophysiologic and clinical points.

We then turn to the discussion of a similar topic devoted to musculoskeletal manifestations of non-RA connective tissue diseases in adults including Still's disease, systemic lupus erythematosus, scleroderma, polymyositis/dermatomyositis, Sjögren's syndrome, and mixed connective tissue disease. Jacques and colleagues begin by presenting the entity of each clinical picture and then scrupulously describe radiographic features of all entities, not yet often met in daily practice.

Another innovative approach to sacroiliitis is offered by Jans et al in “Sacroiliitis in Axial Spondyloarthritis: Assessing Morphology and Activity.” The authors highlight the new anatomy of the sacroiliac joint and not only discuss the magnetic resonance imaging (MRI) appearance of active sacroiliitis and structural abnormalities but also elaborate on the strength and limitations of MRI, providing new insight into the usefulness of this technique.

To complete this discussion of spondyloarthritides, Eshed and colleagues present a timely topic. They took upon themselves the challenging problem of identifying the difference in the imaging presentation of specific subtypes of spondyloarthritis and have successfully provided us with distinct imaging features that may help differentiate linked together entities of the spondyloarthritis (SpA) group.

A similar topic follows, related to the interpretation of imaging and the differential diagnosis of axial SpA spondylitis and anterior chest wall involvement by Rennie et al. The authors remind us about the quite frequent involvement of the anterior chest wall in SpA, recall specifically the anatomy of the sternal joints and resulting types of pathologies, and lastly discuss SpA features on radiographs, MRI, scintigraphy, and ultrasound.

Another important article, “CRMO and SAPHO: The Value of Imaging,” shedding a guiding light to the common problem of how to diagnose these closely related conditions, was written by Jurik and colleagues. In this comprehensive overview, readers can learn the genesis of the disease and also about the relevant clinical, pathogenetic, and pathologic findings. The article confirms the diversified radiologic picture of CRMO/SAPHO that has not yet been classified into any of the groups of rheumatologic disorders.[6]

Another article discusses the significant advances in imaging techniques in the diagnosis and monitoring of gout, calcium pyrophosphate deposition disease, and hydroxyapatite arthropathy. Teh et al meticulously describe the ultrasound, dual-energy computed tomography, MRI, and positron emission tomography/computed tomography (PET/CT) features of diseases for depicting the crystal deposition in the joints and other soft tissues. They describe the sensitivity and specificity of each method, compare their efficacy, discuss false results, and highlight their importance with regard to early and noninvasive diagnosis.

The final two articles look at the advanced imaging techniques in arthritis. Hemke et al wrote an article on novel imaging techniques for the evaluation of rheumatic diseases. In the last few years, several new functional imaging techniques have applied in rheumatic diseases, such as dynamic contrast-enhanced MRI, diffusion-weighted imaging, optical imaging, and PET-MRI, making it possible to evaluate the pathophysiology of rheumatic diseases in greater detail. Moreover, these techniques permit a more quantitative approach for the evaluation of disease activity and damage.

In the concluding contribution to this issue, the detailed work of Oei and colleagues discusses the recent developments in cartilage imaging including T2 and T1ρ mapping, delayed gadolinium-enhanced MRI of cartilage, glycosaminoglycan chemical exchange saturation transfer, and sodium imaging combined with quantitative CT arthrography. We are currently evaluating their utility in osteoarthritis with only a few reports yet available on their use in RA. Cartilage damage in RA, in addition to synovitis or osteitis, according to some hypotheses may induce synovitis, driving an immunoinflammatory response and leading to irreversible joint damage.[7]

We would like to thank the editors for giving us the opportunity to serve as guest editors. We are also indebted to all the authors, distinguished leaders in their field, for their vital contributions and their generosity in sharing their experience in the preparation of this comprehensive up-to-date overview of imaging in rheumatology.

Thank you all for your participation!

• References

• 1 Egund N, Jurik AG. Anatomy and histology of the sacroiliac joints. Semin Musculoskelet Radiol 2014; 18 (03) 332-339
• 2 Ciang NCO, Pereira N, Isenberg DA. Mixed connective tissue disease-enigma variations?. Rheumatology (Oxford) 2017; 56 (03) 326-333
• 3 Kubaszewski Ł, Wojdasiewicz P, Rożek M. , et al. Syndromes with chronic non-bacterial osteomyelitis in the spine. Reumatologia 2015; 53 (06) 328-336
• 4 Horton SC, Tan AL, Freeston JE, Wakefield RJ, Buch MH, Emery P. Discordance between the predictors of clinical and imaging remission in patients with early rheumatoid arthritis in clinical practice: implications for the use of ultrasound within a treatment-to-target strategy. Rheumatology (Oxford) 2016; 55 (07) 1177-1187
• 5 Dale J, Stirling A, Zhang R. , et al. Targeting ultrasound remission in early rheumatoid arthritis: the results of the TaSER study, a randomised clinical trial. Ann Rheum Dis 2016; 75 (06) 1043-1050
• 6 Rukavina I. SAPHO syndrome: a review. J Child Orthop 2015; 9 (01) 19-27
• 7 Smolen JS, Aletaha D, Steiner G. Does damage cause inflammation? Revisiting the link between joint damage and inflammation. Ann Rheum Dis 2009; 68 (02) 159-162