Magnetic resonance imaging of hindfoot involvement in patients with spondyloarthritides: Comparison of low-field and high-field strength units
Introduction
The spondyloarthritides (SpA) are a group of related conditions that includes ankylosing spondylitis (AS), psoriatic arthritis (PsA), reactive arthritis (Reiter's disease), undifferentiated spondyloarthritis (uSpA) and inflammatory bowel-disease-associated arthritis. This group is characterized by the absence of rheumatoid factor and the presence of synovitis and enthesopathy which lead to axial and peripheral inflammatory joint disease [1].
The hindfoot is one of the more commonly affected sites in SpA and may cause considerable morbidity. However, the numerous structures of the feet and ankle make both clinical evaluation of the ankle and diagnosis difficult [2], [3], [4]. Magnetic resonance imaging (MRI) is particularly advantageous for assessing the ankle and its soft tissue structures such as tendons, ligaments and fascia [5], [6], [7].
In recent years, MRI has been shown to be a sensitive tool for early changes of the arthritic disease [8], [9], [10], [11] and few descriptive studies have shown its advantages in imaging hindfoot involvement in inflammatory joint diseases [12], [13].
There has been a trend towards the use of low-field equipment in recent years. Compared to a high-field MRI, dedicated low-field MRI offers greater patient comfort, eliminates the problem of claustrophobia and is less expensive, although issues as limited field of view, unavailability of spectral fat suppression, and non-reimbursement in some countries do still exist.
Low-field MRI has been proved to be a sensitive, reliable tool for evaluating the peripheral joints of patients with inflammatory diseases [8], [14], [15], [16].
The purpose of the current study was to compare high-field and low-field strength MRI in the evaluation of the hindfoot in SpA.
Section snippets
Study design and patients
This study was a prospective trial using a standardised protocol. Patients with SpA who met the ESSG criteria [17] and suffered from heel or ankle pain were enrolled consecutively. Randomly, patients were referred to either high-field or low-field MRI for the evaluation of their ankle.
In each patient a thorough physical examination, laboratory tests and MRI of the hindfoot were performed. Informed consent was obtained from all patients and the study protocol was approved by the local ethics
Results
A total of 25 out of 27 MRI examinations of the hindfoot were evaluated. Two patients from the high-field group were excluded from the study. One refused contrast injection and in the other examination quality was low because of patient movement. No significant differences were found between the two group's demographic data, disease duration, and laboratory parameters (Table 3).
Analyzing all joints together (i.e., all four joints evaluated), no statistical significant difference was found
Discussion
SpA is a progressive, debilitating group of diseases that affects mostly the axial skeleton and lower extremities. Inflammatory processes are evident as synovitis, tenosynovitis, and enthesitis. Early diagnosis and treatment are important for improved outcome [1].
Low-field MRI has been shown to be a cost effective, reliable alternative modality for evaluation of the peripheral joints of patients with inflammatory rheumatic diseases [8], [14], [15], [16]. Hottya et al. have evaluated the
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