Ai Lyn Tan

MRI of enthesitis of the appendicular skeleton in spondyloarthritis

Entheses are sites where tendons, ligaments, joint capsules or fascia attach to bone. Inflammation of the entheses (enthesitis) is a well-known hallmark of spondyloarthritis (SpA). As entheses are associated with adjacent, functionally related structures, the concepts of an enthesis organ and functional entheses have been proposed. This is important in interpreting imaging findings in entheseal-related diseases. Conventional radiographs and CT are able to depict the chronic changes associated with enthesitis but are of very limited use in early disease. In contrast, MRI is sensitive for detecting early signs of enthesitis and can evaluate both soft-tissue changes and intraosseous abnormalities of active enthesitis. It is therefore useful for the early diagnosis of enthesitis-related arthropathies and monitoring therapy. Current knowledge and typical MRI features of the most commonly involved entheses of the appendicular skeleton in patients with SpA are reviewed. The MRI appearances of inflammatory and degenerative enthesopathy are described. New options for imaging enthesitis, including whole-body MRI and high-resolution microscopy MRI, are briefly discussed.

The Nail as a Musculoskeletal Appendage – Implications for an Improved Understanding of the Link between Psoriasis and Arthritis

The nail is considered to be a specialised modification of the skin – an ‘epidermal appendage’. However, the phrase ‘hanging on by your fingernails’ belies a vital aspect of nail microanatomy that has been overlooked, namely that the nail is functionally integrated with the musculoskeletal system. The current article reviews how the nail is functionally linked to the distal phalanx and several distal interphalangeal joint structures, including extensor tendon fibres and the collateral ligaments. New histological images exploring this link are provided. The extensor tendon in particular continues from its bony insertion to envelop the nail root, and the collateral ligaments form an integrated network on the sides of the joint, helping to anchor the nail margins. This virtual continuum of connective tissue structures merges with a thick periosteum on the distal phalanx and with the numerous cutaneous ligaments that anchor the fatty pads of the finger pulp to the skin.

Successful Treatment of Resistant Pseudogout With Anakinra

We describe herein the case of a 63-year-old man with pseudogout affecting multiple joints that was resistant to treatment with allopurinol, steroids, and antiinflammatory drugs. Based on recent data on the molecular mechanism of pseudogout that demonstrated overproduction of interleukin-1 (IL-1), we treated the patient with anakinra, an IL-1 receptor antagonist. The patient responded to treatment with anakinra within 2 weeks, with resolution of the signs and symptoms of pseudogout and normalization of levels of inflammation markers.

Distinct topography of erosion and new bone formation in achilles tendon enthesitis: Implications for understanding the link between inflammation and bone formation in spondylarthritis

OBJECTIVE This study combined ultrasonography of the Achilles tendon enthesis at different stages of spondylarthritis (SpA) with microanatomic studies of normal cadaveric entheses, with the aim of exploring the relationship between bone erosion and new bone formation in enthesitis. METHODS Thirty-seven patients with SpA and Achilles tendon enthesitis (20 with early SpA and 17 with chronic SpA) and 10 normal control subjects underwent ultrasound scanning. The presence of bone erosion and spur formation was recorded at 3 sites: the proximal and distal halves of the enthesis and the adjacent calcaneal superior tuberosity. Parallel histologic analysis was performed on cadaveric Achilles tendon entheses to determine whether regional variations in bone density and trabecular architecture in relation to fibrocartilage distribution are related to disease patterns. RESULTS Bone erosion in patients with early SpA occurred at either the proximal insertion or the superior tuberosity (11 of 20 patients; P < 0.001 versus distal enthesis). Very small spurs, which were present almost exclusively at the distal enthesis, were evident in patients with early SpA and in normal control subjects. However, large spurs were evident distally only in patients with chronic SpA (9 of 17 patients, compared with none of 20 patients with early SpA; P < 0.0001). Histologic studies showed that aged normal individuals had small spurs at the corresponding location. The bone-to-marrow ratio was also significantly lower in the regions prone to erosions (P < 0.05). CONCLUSION Bone erosion in association with Achilles tendon enthesitis in SpA is anatomically uncoupled from bone formation-the 2 processes are topographically and temporally distinct. We thus conclude that disease patterns in SpA are related to normal enthesis structure and biomechanics.

Combined high-resolution magnetic resonance imaging and histological examination to explore the role of ligaments and tendons in the phenotypic expression of early hand osteoarthritis.

Background: The pathogenesis of the early stages of hand osteoarthritis is poorly understood, but recent high-resolution magnetic resonance imaging (hrMRI) studies suggest that the joint ligaments have a major role in the phenotypic expression of the disease. Objective: To combine hrMRI and cadaveric histological studies to better understand the mechanisms of damage, and especially the role of joint ligaments and tendons in disease expression. Methods: hrMRI was carried out in the distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints in 20 patients with osteoarthritis,with a disease duration ⩽12 months. Histological sections of the DIP and PIP joints were obtained from three dissecting-room specimens for comparative analysis. Results: The collateral ligaments influenced the location of both hrMRI-determined bone oedema and bone erosion in early osteoarthritis. These changes were best understood in relation to the enthesis organ concept, whereby the interaction between ligament fibrocartilages leads to bone disease. Normal ligaments were commonly associated with microdamage at insertions corresponding to ligament thickening noted in early osteoarthritis. The ligaments also influenced the location of node formation in early osteoarthritis. The DIP extensor tendon insertions were associated with the development of a neoarticular surface. Conclusions: Small-joint collateral ligaments and tendons have a central role in the early stages of hand osteoarthritis, and determine the early expression of both the soft tissue and bony changes in disease.

Psoriasis patients with nail disease have a greater magnitude of underlying systemic subclinical enthesopathy than those with normal nails

Objective Enthesopathy is a major feature of psoriatic arthritis (PsA), which is supported by imaging studies. Given that nail disease often predates PsA and that the nail is directly anchored to entheses, the authors asked whether nail involvement in psoriasis equates with a systemic enthesopathy. Methods Forty-six patients with psoriasis (31 with nail disease) and 21 matched healthy controls (HC) were recruited. 804 entheses of upper and lower limbs were scanned by an ultrasonographer blinded to clinical details. Results Psoriasis patients had higher enthesitis scores than HC (median (range) 21 (0–65) vs 11 (3–39), p=0.005). Enthesopathy scores were higher in patients with nail disease (23 (0–65)) than in patients without nail disease (15 (5–26), p=0.02) and HC (11 (3–39), p=0.003). Inflammation scores of patients with nail disease (13 (0–34)) were higher than patients without nail disease (8 (2–15), p=0.02) and HC (5 (0–19), p<0.001). Modified nail psoriasis severity index scores were correlated to both inflammation (r2=0.45, p=0.005) and chronicity scores (r2=0.35, p=0.04). No link between the psoriasis area and severity index and enthesitis was evident. Conclusion The link between nail disease and contemporaneous subclinical enthesopathy offers a novel anatomical basis for the predictive value of nail psoriasis for PsA evolution.

Successful treatment of resistant giant cell arteritis with etanercept

Giant cell arteritis (GCA) is a systemic medium to large cell vasculitis that predominantly affects the elderly population.1 Initial high dose corticosteroids are the cornerstone of treatment, which is subsequently tapered.2 However, disease flares are not uncommon and corticosteroid related side effects are frequent.3 The limitations of corticosteroids in the treatment of some cases of GCA have led to the evaluation of other strategies using steroid sparing agents.4–7 In two previous studies patients with resistant GCA were treated with infliximab, a monoclonal chimeric antibody directed against tumour necrosis factor α (TNFα) that binds circulating and membrane bound TNF, with promising results.6,7 The rationale for this approach was that the vasculitic lesions in GCA had prominent macrophage infiltration where excess TNFα production had been demonstrated by immunohistochemistry.8 We report the case of a patient who was treated with the anti-TNFα agent etanercept, which is the fusion protein of the extracellular ligand binding portion of the p75 TNF receptor and the Fc portion of IgG1, on the basis that the GCA could not be controlled and that complications of high dose corticosteroid treatment …

MR imaging of erosions in interphalangeal joint osteoarthritis: is all osteoarthritis erosive?

ObjectiveErosive osteoarthritis is usually considered as an inflammatory subset of osteoarthritis (OA). However, an inflammatory component is now recognised in all subsets of OA, so this subgroup of erosive or inflammatory OA is more difficult to conceptualise. The aim of this study was to compare routine CR and MRI to investigate erosion numbers and morphology to determine whether hand OA in general is a more erosive disease than previously recognised.Design and methodsFifteen patients with clinical (OA) of the small joints of the hand underwent MRI of one of the affected proximal interphalangeal (PIP) or distal interphalangeal (DIP) joints. Conventional radiographs (CR) of the hand were also obtained. The MR images were reviewed by two observers for the presence of central and marginal erosions. The site and morphology of any erosions was recorded. CR images of the same hand joint were scored independently for central and marginal erosions by the same observers.ResultsThere was 100% agreement between the observers for scoring erosions on CR. Agreement for the MRI scores was also excellent (kappa = 0.84). MRI detected 37 erosions, of which only 9 were seen on CR. The increase in sensitivity using MRI was much greater for marginal erosions (1 detected on CR, 19 on MRI) than for central erosions (8 on CR, 18 on MRI). Using MRI 80% of joints examined showed 1 or more erosions compared with 40% using CR. If only marginal erosions were considered 80% of joints were still considered erosive by MRI criteria, but only 1 showed evidence of erosion on CR. Morphologically central erosions appeared to represent areas of subchondral collapse and pressure atrophy. In contrast, marginal erosions resembled those seen in inflammatory arthritides.ConclusionErosions, and particularly marginal erosions typical of those seen in inflammatory arthritis, are a more common feature of small joint OA than conventional radiographs have previously indicated.

The anatomical basis for a novel classification of osteoarthritis and allied disorders

Osteoarthritis (OA) has historically been classified as ‘primary’ where no discernible cause was evident and ‘secondary’ where a triggering factor was apparent. Irrespective of the triggering events, late‐stage OA is usually characterized by articular cartilage attrition and consequently the anatomical basis for disease has been viewed in terms of cartilage. However, the widespread application of magnetic resonance imaging in early OA has confirmed several different anatomical abnormalities within diseased joints. A key observation has been that several types of primary or idiopathic OA show ligament‐related pathology at the time of clinical presentation, so these categories of disease are no longer idiopathic – at least from the anatomical perspective. There is also ample evidence for OA initiation in other structures including menisci and bones in addition to articular cartilage. Therefore, a new classification for OA is proposed, which is based on the anatomical sites of earliest discernible joint structural involvement. The major proposed subgroups within this classification are ligament‐, cartilage‐, bone‐, meniscal‐ and synovial‐related, in addition to disease that is mixed pattern or multifocal in origin. We show how such a structural classification for OA provides a useful reference framework for staging the magnitude of disease. For late‐stage or end‐stage/whole organ disease, the final common pathway of these different scenarios, joint replacement strategies are likely to remain the only viable option. However, for younger subjects in particular, near the time of clinical disease onset, this scheme has implications for therapy targeted to specific anatomical locations. Thus, in the same way that tumours can be classified and staged according to their tissue of origin and extent of involvement, OA can likewise be anatomically classified and staged. This has implications for therapeutic strategies including regenerative medicine therapy development.

Magnetic resonance imaging in the assessment of metacarpophalangeal joint disease in early psoriatic and rheumatoid arthritis

Objectives: The aim of this study was to determine whether magnetic resonance imaging (MRI)‐related entheseal changes including osteitis and extracapsular oedema could be used to differentiate between metacarpophalangeal (MCP) joint involvement in rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Methods: Twenty patients (10 each with early RA and PsA) had dynamic contrast‐enhanced MRI (DCE‐MRI) of swollen MCP joints. Synovitis and tenosynovitis was calculated using quantitative analysis including the degree and kinetics of enhancement of gadolinium diethylenetriaminepentaacetic acid (Gd‐DTPA). Periarticular bone erosion and bone oedema were scored using the Outcome Measures in Rheumatology Clinical Trials (OMERACT) proposals. Entheseal‐related features including extracapsular soft tissue enhancement or regions of diffuse bone oedema were also evaluated. Results: MRI was not able to differentiate at the group level between both cohorts on the basis of entheseal‐related disease but a subgroup of PsA patients had diffuse extracapsular enhancement (30%) or diffuse bone oedema (20%). The RA patient group had a greater degree of MCP synovitis (p<0.0001) and tenosynovitis than PsA patients (p<0.0001). There were no significant differences in either the total number of erosions (p = 0.315) or the presence of periarticular bone oedema (p = 0.105) between the groups. Conclusion: Although conventional MRI shows evidence of an enthesitis‐associated pathology in the MCP joints in PsA, this is not sufficiently common to be of diagnostic utility.