The Role of Musculoskeletal Ultrasound Imaging in Rheumatoid Arthritis

Abstract

Musculoskeletal ultrasound (MSUS) is gaining popularity among rheumatologists, especially in the context of rheumatoid arthritis (RA) joint assessment, as it is a non-invasive, radiation-free imaging modality that is relatively easy to set up in a clinic setting. Although ultrasonography (US) is often regarded as being operator dependent with associated reproducibility issues, the use of consensus-based scoring system along with standardized definition of joint inflammation in RA has been shown to improve its performance/reliability as an outcome measurement tool. Through this review article, we have (i) gone through the principle US findings in RA joint assessment, (ii) discussed various scoring systems for evaluation of US joint pathologies, (iii) described the literature in the use of US in areas of RA diagnosis and disease prognostication and (iv) examined the findings of recent major randomized controlled trials incorporating US as monitoring tools to help target treatment in RA. By doing so, we hope to provide clinicians with an insight into the role of musculoskeletal US imaging in areas of RA diagnosis, prognosis and disease monitoring.

Introduction

Rheumatoid arthritis (RA) is the most common chronic autoimmune inflammatory joint disease (prevalence of about 1%), and it commonly affects the peripheral joints including the small joints of the hands and feet. Multiple imaging modalities such as conventional radiography (CR), ultrasonography (US), magnetic resonance imaging (MRI) and computed tomography (CT) are available to assess for structural joint pathologies in RA. To date, CR remains a useful modality for RA joint assessment, and its advantages include its low cost, easy availability and ability to provide the clinician with a quick assessment of the imaged joints, which is particularly useful at the hands and feet (Baker et al. 2015). It is the current recommended modality by the European League Against Rheumatism (EULAR) for baseline and follow-up review (Colebatch et al. 2013). However, CR is not a sensitivity modality to pick up erosions in early disease, as it only detects erosions in 6%–40% of patients with RA at 6-mo disease duration (Østergaard et al. 2008). In fact, in the EULAR recommendations for the use of joint imaging in clinical management of RA, it was specifically mentioned that US or MRI can be considered if CR does not show any damage (bone erosions or loss of joint space) (Colebatch et al. 2013). CT is often regarded as the gold standard for identifying structural bone damage, particularly erosions. However, its use in the clinical setting for RA joint assessment is limited owing to concerns of radiation exposure and limited soft tissue visualization. MRI has exceptional soft tissue visualization capabilities and can detect bone marrow edema (i.e., osteitis), which can be highly predictive of subsequent bone erosion development (Østergaard et al. 2003). The main drawbacks of MRI include the high costs, long scanning duration and less universally available scanning facilities compared with CR (Tan et al. 2012).

US has gained popularity among rheumatologists as it is non-invasive, relatively cheaper to set up (compared with MRI), radiation free and allows dynamic assessment at multiple joint sites. US also offers the prospect of more accurate assessment of soft tissue inflammation than conventional clinical examination (Wakefield et al. 2004). One concern with US is related to its reproducibility (i.e., inter-/intra-rater reliability issues), although it has been shown that a consensus-based scoring system and a standardized definition of synovitis in RA would improve the performance of US as an outcome measure (D'Agostino et al. 2017; Terslev et al. 2017). This review article will focus on the utility of US in the diagnosis, prognostication and as a monitoring tool for RA. All studies included in this review did obtain informed consent from each study participant and was approved by an ethics committee or institutional review board.