Enthesitis is a cardinal feature of spondylarthritis (SpA), and the pelvis is a common site of enthesitis. This study aimed to establish the association between pelvic enthesis involvement on pelvic X-ray and SpA diagnosis through a radiographic enthesis index (REI) and to assess the reliability and accuracy of this REI.

The participants were SpA patients and a control group composed of patients with chronic lumbar pain without SpA. Three blinded observers assessed each pelvic radiography three times. Three zones were used: Zone I (ZI), the iliopubic ramus; Zone II (ZII), the pubic symphysis, and Zone III (ZIII), the ischiopubic ramus. A grading system was created from 0 to 3 [Grade 0, normal; Grade 1, minimal changes (subcortical bone demineralization and/or periosteal wishkering, seen as radiolucency and trabeculation of the cortical bone upon tendon insertion); Grade 2, destructive changes (Grade 1 findings and erosions at the enthesis site); and Grade 3, findings of Grade 2 plus >2 mm whiskering out of the cortical bone) for the REI. The sum of the results of the three zones was called the total REI. For statistical analysis, we used the weighted kappa statistic adjusted for prevalence and bias using Gwet's agreement coefficient.

We enrolled 161 patients, 111 of them with SpA (39.6 % with axial SpA and 47.7 % with peripheral SpA) and 50 without SpA. In the SpA group, 36.7 % and 25.7 % had REI Grades 2 and 3 in ZIII, respectively, while only 6 % of the controls had these grades. For ZI, the frequency of Grades 1 to 3 was 42.3 % in the SpA group (8.1 %, 14.4 %, and 19.8 %, respectively), compared to only 2 % in the controls. ZII was unaffected in most of the patients with SpA (82.9 %) and in the controls (98 %). In the control group, Grade 0 was the most common REI grade in all three zones. The agreement was almost perfect for each zone and between the independent readers. The ROC-curve analysis showed that the highest performance areas were the total REI, ZIII, and ZI. Most (75 %) of the SpA patients without sacroiliitis on X-ray were REI-positive. The sensitivity of the REI for SpA diagnosis was 82 %, while the sensitivity of sacroiliitis on X-ray was 38.7 %.

The assessment of pelvic enthesis using the REI on pelvic radiography may be useful for SpA diagnosis. Total REI, ZIII, and ZI had the highest accuracy and almost perfect reliability. The REI is especially helpful in patients without sacroiliitis on imaging.

The purpose of this study is to evaluate the prevalence of pelvic enthesopathy on computed tomography (CT) in patients with DISH compared to matched control group. Pelvic CT examinations of patients with DISH (Resnick criteria) were retrospectively evaluated for the presence of enthesophytes at four entheseal sites bilaterally: ischial tuberosity, pubis, greater trochanter, and anterior superior iliac spine (ASIS). This was compared with age- and gender-matched control group of consecutive patients with <2 flowing osteophytes on CT along the entire spine. Multivariate analysis of variance (ANOVA) was applied to examine the degree of difference between pelvic enthesopathy in DISH patients and controls and to estimate the potential predictive ability of the different findings. Logistic regression analysis was used to estimate the odds ratio of the studied findings. Pelvic CTs of 210 patients (149:61, M:F; average age, 72.3 years) were evaluated: DISH group, 104 patients (74:30, M:F); matched control group, 106 patients (75:31, M:F). Mean total and local enthesopathy scores were significantly higher in the DISH group compared with the control group (total 5.03:1.9; ASIS 1.58:0.55; pubis 0.94:0.36; ischial tuberosity 1.47:0.76; greater trochanter 1.04:0.24; p < 0.001). ASIS and greater trochanter enthesophytes were the most robust contributors that significantly distinguished between patients with DISH and those without DISH. Prominent enthesophytes were more common among DISH patients (DISH:controls, 52:13, p = 0.02). Prominent pelvic enthesophytes detected on CT have a strong discriminating power between DISH and non-DISH patients. Results imply that pelvic enthesopathy may be included in the radiographic criteria for DISH.

Ankylosing spondylitis (AS) is the most common clinical subgroup of sero-negative spondyloarthropathies. Radiographic and clinical signs of bilateral inflammatory involvement of sacroiliac joints are the gold standard for the diagnosis of juvenile AS. Although radiographic evidence of sacroiliitis is included in the definition, it is not mandatory for the diagnosis of juvenile AS. The aim of this study is to describe pelvic enthesitis-osteitis MRI findings accompanying sacroiliitis in a group of juvenile AS. Eleven patients suffering from low back pain underwent MRI of the pelvis and were enrolled in this retrospective study. The mean duration of symptoms was 12 months. The mean age of the 11 cases in our study was 12.18 years (range, 6-19). There were eight boys and three girls. Anteroposterior radiographs of the pelvis were obtained in all patients. Sacroiliac joint involvement was detected in all of the cases by pelvic MRI. Pathologic signal changes were detected in the pubic symphisis (osteitis pubis) in ten cases, trochanteric bursitis in six cases, coxofemoral joint in five cases, crista iliaca in three cases, and ischion pubis in three cases. There was increased T2 signal intensity in eight of the 11 cases (72.7%) relevant with soft tissue edema/inflammation. This high correlation between sacroiliitis and enthesitis suggests that enthesitis could be an important finding in juvenile AS.

To identify the characteristic features of Achilles enthesitis of the spondyloarthropathies (SpA) detectable by colour Doppler energy ultrasound (CDEU) in the context of the 'enthesis organ'.

Seventy patients with SpA and 15 healthy subjects were clinically evaluated and underwent CDEU examination of the Achilles entheses. The CDEU images were evaluated according to five distinctive CDEU features of enthesitis in the context of the enthesis organ.

Fifty-six of the 70 SpA patients (80%) showed at least one abnormal finding of the enthesitis on CDEU examination, affecting 91 of 140 Achilles entheses examined (65%). Only 22 of 140 Achilles entheses (15.7%) showed abnormal vascularization in the peri-sesamoidal and periosteal areas or in the area of enthesis fibrocartilage. In addition, 67 (47.9%) and 18 (12.9%) of 140 Achilles entheses examined showed cortical bone irregularities and erosions, respectively, at areas of the periosteal and the enthesis fibrocartilage. Sixteen (88.9%) of 18 clinically detected Achilles enthesitis and six (75%) of eight Achilles entheses with swelling on clinical examination presented corresponding abnormalities on CDEU examination. The Doppler twinkling artefact (TA) was observed consistently in all normal entheses and completely disappeared upon stabilization of the probe application. The C-reactive protein (CRP) level was higher in the patients with cortical bone erosion than in those without erosion.

This study demonstrates the characteristic features of enthesitis detectable by CDEU in the context of the enthesis organ and shows a good correlation with clinical as well as with laboratory findings.

It has been proposed that the defining difference between rheumatoid arthritis and spondyloarthropathy (including psoriatic arthritis) is the initial pathological lesion where the emphasis in psoriatic arthritis is on the enthesis and in rheumatoid arthritis on the synovium. Classical radiological descriptions of seronegative spondyloarthropathy include enthesopathy at major entheseal insertions characterised by erosions and exuberant new bone formation. In this study, the plain radiographic features of spondyloarthropathy are compared between psoriatic arthritis, other spondyloarthropathies and rheumatoid arthritis.

The CASPAR study collected clinical, radiological and laboratory data on 588 patients with physician diagnosed psoriatic arthritis and 525 controls with other inflammatory arthritis, 70% of which had rheumatoid arthritis. Plain radiographs of the pelvis and heels were part of the study protocol, although radiographs of other potential entheseal sites such as the knee, elbow and shoulder, were interpreted if available. All radiographs were read blind by two observers working in tandem.

Significant differences in entheseal erosion and entheseal new bone formation were found between psoriatic arthritis, ankylosing spondylitis, undifferentiated spondyloarthropathy, rheumatoid arthritis and other diagnoses (entheseal erosion, chi-squared 20.8, p=0.008; entheseal new bone formation, chi-squared 24.5, p=0.001). These differences were mainly due to a higher proportion of these features in ankylosing spondylitis. No differences in the plain radiographic features of enthesopathy were found between psoriatic arthritis and rheumatoid arthritis except in the case of entheseal new bone formation at sites of attachment of inguinal ligament, sartorius and rectus femoris muscles to the ilium (OR 3.01, 95% CI 1.13-8.02). Very few subjects with symptomatic heel involvement had radiographic changes and minimal differences were found between those with and without symptoms in terms of new bone formation and erosion at either calcaneal site.

New bone formation and erosion at major entheseal sites is most commonly seen in ankylosing spondylitis. Plain radiographic features of major enthesopathy are poor discriminators between psoriatic arthritis and rheumatoid arthritis.

To develop recommendations regarding imaging studies for the diagnosis and follow-up of patients with axial forms of ankylosing spondylitis (AS) seen in everyday practice.

Evidence from the literature and expert opinion were used to develop the recommendations. Using the Delphi consensus procedure, a scientific committee selected five areas of interest, about which scientific evidence was sought by searching Medline and the databases maintained by the French Society for Rheumatology, European League against Rheumatism, and American College of Rheumatology. Based on this evidence, a panel of experienced rheumatologists drafted recommendations, using expert opinion if needed to supplement gaps in evidence. For each recommendation, the level of evidence and the extent of agreement among the experts were specified.

The five areas of interest dealt with the usefulness of imaging studies for the diagnosis, follow-up, prognostic evaluation, and assessment of treatment responses in patients with AS. The literature search retrieved 144 articles based on titles and abstracts. After elimination of articles that did not include an analysis of the radiological evaluation of AS, 73 articles were left for review. Eight recommendations were drafted then validated by having all panel participants vote during a final meeting.

Eight recommendations about the use of imaging studies in patients with AS were developed. They can be expected to improve clinical practice uniformity and, in the longer term, to optimize the management of patients with AS.

To determine alterations of the soft tissue, tendon, cartilage, joint space, and bone of the foot using magnetic resonance (MR) imaging in ankylosing spondylitis (AS) patients.

Clinical and MR examination of the foot was performed in 23 AS patients (46 feet). Ten asymptomatic volunteers (20 feet) were studied on MR imaging, as a control group. MR imaging protocol included; T1-weighted spin-echo, T2-weighted fast-field echo (FFE) and fat-suppressed short tau inversion recovery (STIR) sequences in sagittal, sagittal oblique, and coronal planes using a head coil. Specifically, we examined: bone erosions, tendinitis (acute and chronic), para-articular enthesophyte, joint effusion, plantar fasciitis, joint space narrowing, soft tissue edema, bone marrow edema, enthesopathy in the Achilles tendon and plantar fascia attachment, subchondral signal intensity abnormalities (edema and sclerosis), tenosynovitis, retrocalcaneal bursitis, subchondral cysts, subchondral fissures, and bony ankylosis. Midfoot, hindfoot, and ankle were included in examined anatomic regions.

Clinical signs and symptoms (pain and swelling) due to foot involvement were present in 3 (13%) of the patients while frequency of involvement was 21 (91%) with MR imaging assessment. The MR imaging findings were bone erosions (65%), Achilles tendinitis (acute and chronic) (61%), para-articular enthesophyte (48%), joint effusion (43%), plantar fasciitis (40%), joint space narrowing (40%), subchondral sclerosis (35%), soft tissue edema (30%), bone marrow edema (30%), enthesopathy of the Achilles attachment (30%), subchondral edema (26%), enthesopathy in the plantar fascia attachment (22%), retrocalcaneal bursitis (22%), subchondral cysts (17%), subchondral fissures (17%), tendinitis and enthesopathy of the plantar ligament (13%), and bony ankylosis (9%). The most common involved anatomical region was the hindfoot (83%) following by midfoot (69% ) and ankle (22%).

In our experience, MR imaging may detect inflammatory and/or erosive bone, soft tissue, cartilage, tendon, and joint abnormalities in AS patients, even if AS patients did not have clinical signs and symptoms of foot involvement. If these data prove to be confirmed in further MR studies, MR imaging may be of importance especially in early diagnosis of inflammatory changes in the foot.

Many cartilage matrix proteins or domains such as collagen types II, IX, and XI, GP39, AG1, VG1, and LP are potential antigens that might induce polyarthritis in susceptible animals (Table 1). Ordinarily, spondylitis is not a feature of polyarthritis induced with collagen types II, IX, and XI, GP39, cartilage matrix protein (matrilin-1) and cartilage LP. It seems that only the proteoglycans aggrecan and versican are capable of inducing sacroiliitis and spondylitis. Both molecules are structural proteins in intervertebral discs. Moreover, the arthritogenic or spondylitogenic epitopes of both molecules have been localized to the homologous N-terminal G1 globular domains. This region of versican and aggrecan is highly conserved, with 52% identity of amino acids. The homology is seen exclusively in the G1 domain and is concentrated between residues 115 and 332 (AG1 numbering) near the natural cleavage DIPEN site of aggrecan [84, 85]. Extra-articular pathology is often seen in rheumatic diseases, especially in AS. Other tissues, such as the sclera of the eye [86] and the media of the arteries [86, 87], also contain type II collagen, AG1, VG1, and LP, and versican is present in the central and peripheral nervous systems. Thus, there is the potential for an immune response against cartilage G1 and LP to be directed against related structures in extra-articular tissues. The presence of versican in the tendon and trochlea of the human superior oblique muscle might account for the occurrence of transient attacks of acquired Brown syndrome in patients with juvenile and adult forms of chronic RA [88]. Thus, it will be interesting to determine whether or not extra-articular expression of these cartilage proteins is closely related to extra-articular pathogenic expression in rheumatic diseases. Uveitis develops in VG1-immunized BALB/c mice, which is not seen in AG1-, and LP-treated animals. There is evidence that aggrecan and LP are also localized at these sites in the eye, but only immunity to versican can induce uveitis. In sacroiliitis and enthesitis of AS patients, the inflammation is associated with chondrometaplasia. In versican-induced sacroiliitis, replacement of cartilage by bone is seen with relatively little inflammation, somewhat resembling the situation in AS (Fig. 2). Versican can also stimulate chondrocyte proliferation [43]. Three conserved domains of human cartilage matrix molecules, namely VG1, AG1, and LP, show considerable homology [77, 79, 80, 89], and each is capable of inducing a unique inflammatory arthritis in BALB/c mice, with VG1 inducing only spondylitis [65], LP inducing peripheral arthritis with no spondylitis [90], and AG1 inducing axial and peripheral arthritis [66, 91]. It remains a mystery why such similar molecules cause different pathology in different target tissues. The exact immunopathogenic mechanisms deserve further study.

To compare ultrasonography (US) with clinical examination in the detection of entheseal abnormality of the lower limb in patients with spondyloarthropathy (SpA).

35 patients with SpA (ankylosing spondylitis 27; psoriatic arthritis 7; reactive arthritis 1) underwent independent clinical and ultrasonographic examination of both lower limbs at five entheseal sites-superior pole and inferior pole of patella, tibial tuberosity, Achilles tendon, and plantar aponeurosis. US was performed using an ATL (Advanced Technology Laboratories, Bothell, Washington, USA) high definition imaging 3000 machine with linear 7-4 MHz and compact linear 10-5 MHz probes to detect bursitis, structure thickness, bony erosion, and enthesophyte (bony spur). An enthesitis score was formulated from these US findings giving a possible maximum total score of 36.

On clinical examination 75/348 (22%) entheseal sites were abnormal and on US examination 195/348 (56%) sites were abnormal. In 19 entheseal sites with bursitis on US, only five were detected by clinical examination. Compared with US, clinical examination had a low sensitivity (22.6%) and moderate specificity (79.7%) for the detection of enthesitis of the lower limbs. There was no significant correlation between the US score of enthesitis and acute phase parameters such as erythrocyte sedimentation rate (ESR) or C reactive protein (CRP). The intraobserver kappa value for analysis of all sites was 0.9.

Most entheseal abnormality in SpA is not detected at clinical examination. US is better than clinical examination in the detection of entheseal abnormality of the lower limbs in SpA. A quantitative US score of lower limb enthesitis is proposed but further studies are required to validate it in SpA.

Enthesitis is a distinctive pathological feature of spondyloarthropathy and may involve synovial joints, cartilaginous joints, syndesmoses and extra-articular entheses. This review focuses on peripheral extra-articular enthesitis which is a clinical hallmark of spondyloarthropathy. The entheses of the lower limbs are more frequently involved than those of the upper limbs, and heel enthesitis is the most frequent. Entheseal pain may be mild or moderate as well as severe and disabling. Peripheral enthesitis may be observed in all forms of spondyloarthropathy, including the undifferentiated ones, and may for a long time be the only long-standing clinical manifestation of the B27-associated disease process. Various imaging methods have been suggested for studying peripheral enthesitis. Ultrasonography and magnetic resonance imaging are the most useful because they may show alterations of the structures involved. Therapy of peripheral enthesitis consists of NSAIDs, orthoses and physical therapy. Steroid injections, second line drugs such as sulphasalazine and radiotherapy are reserved for more severe cases.