Editorial Ann Rheum Dis April 2012 Vol 71 No 4 477 Enthesitis, the inflammation involving the insertion of tendons, ligaments and joint capsule is a characteristic sign and hallmark of several rheumatic diseases in both adult and paediatric patients. The change in the perception of enthesitis (ie, its growing sig- nificance as a clinicopathological entity) is best reflected in the new European League Against Rheumatism (EULAR) recom- mendations for psoriatic arthritis, which recommend antitumour necrosis factor therapy for patients with active enthesitis and/or dactylitis and insufficient response to non-steroidal anti-inflammatory drugs or local steroid injections. 1 It is also one of three entry criteria (the other two being arthritis and dactylitis) for the new Assessment of SpondyloArthritis Society classification criteria for peripheral spon- dylarthritis. 2 Broadly, enthesitis can be evaluated either clinically or by one of several imaging modalities that have been validated to various extents for the assess- ment thereof. A recent systematic literature review that examined the US definition of enthesi- tis found large variability in the definitions utilised to outline enthesitis. 3 Indeed, the appropriate definition of enthesitis and of its components remains an issue that is crucial for the evaluation of enthesitis with any given imaging modality. As of yet, we have no single examining modal- ity that is capable of evaluating all of these components. Clinical examination may aid in the detection of enthesitis when palpation is used to trigger pain or tenderness. However, it only allows the detection of soft tissue swelling, including tendon thickening and accompanying bursitis, two key features of enthesitis, while fail- ing to provide information on typical bony changes, ie, bone erosions, enthesophytes and calcifications. Clinical evaluation has been shown to underestimate enthesi- tis involvement compared with imaging modalities. 3–6 Contrary to clinical evalu- ation, conventional radiography is useful for assessing bony changes, as described above, but does not permit the evaluation of soft tissue changes. MRI and ultrasound have clear advantages over both clinical examination and conventional radiogra- phy, in that they are capable of providing information with respect to both bony changes and soft tissue processes. MRI is increasingly investigated for its use in assessing enthesitis mainly in anky- losing spondylitis, in which it is capable of detecting diffuse bone oedema associ- ated with surrounding soft tissue oedema in the region adjacent to enthesis. 7 MRI is the imaging modality of choice for assess- ing bone marrow oedema; however, this may occur in a number of distinct dis- eases, 8–11 histopathological correlation is moderate, 9 and results from several studies have questioned its specificity as a strictly pathological phenomenon. 11–13 When soft tissue involvement occurs in a synovial joint, synovitis may mask some, if not all, MRI features of enthesi- tis. 14 Interestingly, a recent investigation revealed that bone marrow oedema was the most specific finding on non-contrast MRI of the hands and wrists in rheuma- toid arthritis. 15 However, MRI cannot be considered as a gold standard as it lacks sensitivity and specificity for peripheral enthesitis, 16–18 due to the anatomical build-up of the entheses, which is unfa- vourable for visualisation using MRI due to the low water content of the fibrocarti- lage component of the enthesis. Ultrasound is an imaging tool that has been increasingly utilised in the past two decades for the assessment of enthesitis. 3 4 19–24 Ultrasound is capable of demon- strating and evaluating both soft tissue and bony changes, and additionally may also be used to assess the vascularisation and blood flow in the enthesis by colour or power Doppler. 25 26 A recent system- atic literature review that examined the ultrasound definition of enthesitis found evidence supporting face, content valid- ity and reliability for the evaluation of enthesitis. 3 This review concluded that ultrasound demonstrated face and content validity, but that criterion and construct validity may not be properly evaluated lacking a gold standard comparator. However, with increased sensitivity comes the price of reduced specificity. Previous studies have shown that certain components of enthesitis such as bony changes, tendon thickening, etc. cannot be adequately distinguished from entheseal involvement due to both mechanical and degenerative processes. 19 27 The detec- tion of subclinical enthesitis in clinically asymptomatic regions in patients with psoriatic arthritis 28 29 highlights the dis- crepancy between clinical symptoms (eg, pain or tenderness) and imaging phenom- ena interpreted as a pathological findings. It also raises awareness to the possibility of inappropriate labelling of otherwise healthy individuals as patients and of erro- neous diagnosis based on certain imaging phenomena, which can, in certain cases, be considered components of enthesitis, but that may be detected in the absence of an inflammatory involvement of the entheses. Feydy and colleagues 30 report the results of a comparative study of MRI and power Doppler ultrasound of the heel in patients with spondylarthritis with and without heel pain and in controls. In their article the authors use the term enthesopathy, rather than enthesitis, because the term enthesi- tis remains undefined in the context of ultrasound. This underscores the impor- tance of terminology, with enthesopathy corresponding to a group term encom- passing all forms of entheseal involve- ment, which may be caused by different aetiologies (figure 1). Within this group the term enthesitis refers to entheseal involvement in the context of an inflam- matory rheumatic disease. The Outcome Measures in Rheumatoid Arthritis Clinical Trials (OMERACT) Ultrasound Group consensus definition for enthesopathy requires the presence of tendon or liga- ment pathology, manifested as either loss of normal echostructure and/or thicken- ing seen in two planes. 31 Doppler signal and bony changes are included as optional findings. The recent systematic review on the ultrasound evaluation of enthesitis found that enthesitis was most commonly characterised by increased thickness and hypoechogenicity (94% and 83% of stud- ies, respectively) of the tendon in the stud- ies included. 3 Feydy and colleagues 30 divide the com- ponents of enthesopathy according to the imaging modalities utilised into two groups, that of early and chronic changes, Ultrasound for enthesitis: handle with care! Peter Mandl, 1,2 Dora S Niedermayer, 2 Peter V Balint 2 1 Division of Rheumatology, Medical University of Vienna, Vienna, Austria 2 3rd Department of Rheumatology, National Institute of Rheumatology and Physiotherapy, Budapest, Hungary Correspondence to Peter V Balint, 3rd Department of Rheumatology, National Institute of Rheumatology and Physiotherapy, 25–29 Frankel L St, 1023 Budapest, Hungary; pvbalint@gmail.com on January 12, 2022 by guest. Protected by copyright. http://ard.bmj.com/ Ann Rheum Dis: first published as 10.1136/annrheumdis-2011-201217 on 2 March 2012. Downloaded from