Imaging in Psoriatic Arthritis

Review Standardizing the monitoring of outcome measures: imaging in psoriatic arthritis The wide spectrum of manifestations of musculoskeletal inflammation in psoriatic arthritis makes standardized assessment of joint damage in psoriatic arthritis a challenge. Assessment of erosions and joint space narrowing on plain radiographs of the hands and feet has remained the benchmark for assessing damage in psoriatic arthritis. The methods used to assess damage have been mostly borrowed from those used in rheumatoid arthritis. Axial joint involvement has not been systematically addressed. Methods to assess spinal disease have been borrowed from those used in ankylosing spondylitis. Both ultrasound and MRI have demonstrated promise in the assessment of psoriatic arthritis. The Outcome Measures in Rheumatology Clinical Trials (OMERACT) group is involved in the development of valid, reliable and feasible methods for assessment of joint involvement in psoriatic arthritis. † KEYWORDS: inflammation n joint damage n MRI n psoriasis n radiography Dafna D Gladman n spondylitis n ultrasonography n validation & Vinod Chandran1 1Psoriatic Arthritis Program, University Health Network, 1E 412, 399 Bathurst Psoriatic arthritis (PsA) is an inflammatory and validates outcome measures in rheumato- Street, Toronto, Ontario, M5T 2S8, musculo skeletal disease associated with psoria- logy, identified several measures that should be Canada †Author for correspondence: sis [1]. Psoriasis is an inflammatory, immune- assessed in patients with PsA [6]. These include University of Toronto, Toronto Western mediated skin disease that occurs in 2–3% of the assessment of peripheral joints, skin and Research Institute, Psoriatic Arthritis Program, University Health Network, the worldwide population [2]. Up to 30% of nail lesions, patient assessment of pain, patient 399 Bathurst Street, 1E-410B, Toronto, patients with psoriasis may develop inflamma- assessment of function, patient and physician Ontario, M5T 2S8, Canada tory musculo skeletal manifestations including assessment of disease activity and patient assess- Tel.: +1 416 603 5753 Fax: +1 416 603 9387 synovitis of the peripheral joints (peripheral ment of quality of life. In addition, radiographic [email protected] arthritis), which occurs in the majority of assessment was highly recommended, although patients, inflammation of the joints of the spine not yet mandatory since the instruments to (axial PsA), inflammation at the insertions of assess radiographs in PsA have not been vali- tendons and muscles into bone (enthesitis) and dated. Moreover, other imaging modalities, such inflammation of the whole digit affecting fingers as ultrasound (US) and MRI were considered and toes (dactylitis) [3]. Although in the past PsA important and included in the research agenda. was considered a mild form of arthritis, over the In this article we review the imaging modalities past several decades it has become apparent that used in the assessment of patients with psoriasis the arthritis is more common and more severe and PsA, discuss the controversies associated with than previously appreciated. Some 20% of the their use, and recommend future approaches. patients develop a severe, destructive form of The search was conducted in PubMed, using the arthritis called arthritis mutilans, which in the keywords: PsA, spondylitis, imaging, radiogra- past was thought to occur in only 5% of cases, phy, MRI, ultrasound and scintigraphy. Articles and more than 55% of the patients develop at relevant to PsA were selected. least five deformed joints over the 10-year follow- up period [4]. This results in a significant reduc- Why should we use imaging to tion in joint function and is associated with a assess patients with PsA? reduced quality of life in patients with PsA [5]. Psoriatic arthritis may be a very aggressive dis- The Group for Research and Assessment of ease with rapid progression to joint damage. In Psoriasis and Psoriatic Arthritis (GRAPPA), a study of a cohort of patients with early PsA, an international collaborative group includ- who were presented to an early arthritis clinic ing rheumatologists, dermatologists, radiolo- within 5 months of the onset of symptoms, gists, methodologists and members of patient 27% of the 129 patients already had at least one groups and industry, in collaboration with the joint erosion at presentation [7]. Over the first Outcome Measures in Rheumatology Clinical 2 years of follow-up 47% of these 129 patients Trials (OMERACT) group, which develops had at least one erosion, and this is despite the 10.2217/IJR.10.103 © 2011 Future Medicine Ltd Int. J. Clin. Rheumatol. (2011) 6(1), 77–86 ISSN 1758-4272 77 Review Gladman & Chandran Standardizing the monitoring of outcome measures: imaging in psoriatic arthritis Review fact that 56% of the patients had been treated Imaging peripheral joints in PsA with DMARDs. An observational study of Several features can be identified by radio- 220 patients identified 67% of the patients graphic assessment of the peripheral joints in with erosive disease at first visit, with an aver- PsA [15]. Erosions, which can be marginal or age disease duration of 9 years [8]. Another study nonmarginal, can be detected. Periostitis or a of 71 patients who had no erosive disease at bony reaction at the sites of inflammation or recruitment reported that 45% of the patients tendon insertion may be noted. In PsA the peri- developed erosive disease over an average of ostitis is specifically ‘fluffy’. Severe erosive dis- 8 years [9]. Thus, the study with the early PsA ease leads to the ‘pencil-in-cup’ change that is cohort suggests that patients with PsA develop typical for PsA. However, patients with PsA also erosions early, whereas the observational cohorts demonstrate ankylosis, and at times one finds demonstrate that patients with PsA sustain one joint totally destroyed with a pencil-in-cup progression of damage over time. Some stud- change while the next joint in the same digit ies of progression of damage have used clinical demonstrates total ankylosis. Recognizing these damage (defined as the presence of deformities, radiographic features is important, as they can limitation of movement of greater than 20% of help differentiate patients with PsA from those the range not related to a joint effusion, flail with rheumatoid arthritis (RA) and those with joints, fused joints or joints that have undergone osteoarthritis or even gout. replacement) as the outcome measure, since it To assess severity and progression over time is an assessment that can be made at the bed- and to compare across studies, a number of side at each visit and does not require additional radiographic scoring methods have been used cost or radiation exposure [10,11]. However, it to record changes in the peripheral arthritis of has been demonstrated that there is a strong PsA [16]. These include a modification of the relationship between clinical and radiological Steinbrocker method, originally developed for damage, as radiological damage often precedes RA [17]; a modification of the Sharp method, the detection of clinical damage [12]. Moreover, also originally developed for RA [18,19]; the van it has been demonstrated that patient func- der Heijde (vdH) modification of the Sharp tion, as determined by the Health Assessment method [20]; the Larsen method [21] and the Questionnaire Score, is related to clinical and Ratingen method [22]. The Ratingen method is radiological damage [13]. In addition, the pres- the only one specifically developed for PsA. ence of erosion at first visit was a risk factor for While the modified Steinbrocker and the mortality among patients with PsA [14]. Thus, Larsen methods assess each of the hand and foot imaging of the joints is relevant in patients with joints globally, the Sharp and the vdH–Sharp PsA. In addition to radiographs, other imaging methods record each site for erosion and joint modalities include US and MRI. These tech- space narrowing (JSN) separately. The origi- niques have higher sensitivity in the detection of nal Sharp method includes only the hands and synovitis and joint damage and may prove use- wrists while the vdH–Sharp includes the feet. ful in early detection of joint damage. However, The Ratingen method includes scores for bony prospective studies using these modalities are proliferation. A comparison of these methods not currently available. is given in Table 1. The Sharp and vdH–Sharp Thus, it is important to assess patients methods have been used to evaluate radio- with PsA using imaging in order to detect graphic progression in randomized controlled early changes and follow the progression of trials with anti-TNF agents [19,23,24]. the disease. It is also important to determine response to therapy in terms of prevention of Modified Steinbrocker method damage progression. The original Steinbrocker classification scored a patient with RA according to their worst joint [25]. Imaging in PsA: current status The modified Steinbrocker method scores the Plain radiographs are used to determine the pres- wrists, metacarpophalangeal (MCP), proximal ence of periostitis (a criterion for classification and distal interphalangeal, metatarso phalangeal of PsA) assess damage (erosions, osteolysis, sub- (MTP) joints as well as the interphalangeal joints luxation and ankylosis) in the peripheral joints, of the first toes (total: 42 joints) on a 0–4 scale determine the extent of involvement in the sacro- where 0 is normal, 1 represents juxta-articular iliac

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