RESEARCH - MRI of sacroiliac joints can detect inflammation, damage early

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MRI of sacroiliac joints can detect inflammation, damage early

Rheumawire

Mar 22, 2006

Janis

Maastricht, the Netherlands - Magnetic resonance imaging (MRI) of sacroiliac

(SI) joints in patients with recent-onset back pain can reliably detect

inflammation and structural changes and is likely to be helpful in

diagnosing sacroiliitis, often a sign of ankylosing spondylitis (AS) in such

patients [1]. Dr Liesbeth Heuft-Dorenbosch (University Hospital Maastricht,

the Netherlands) and colleagues report in Arthritis Research & Therapy that

about one third of patients with recent-onset inflammatory back pain showed

inflammation of the SI joints and that one sixth of patients showed

structural changes in at least one SI joint.

Senior author Dr Desire van der Heijde (University Hospital Maastricht) told

rheumawire, " MRI of sacroiliac joints is sufficiently reliable to be used in

determining inflammatory and structural changes due to sacroiliitis, and

looking for [MRI evidence of] bone-marrow edema and/or subchondral

inflammation is sufficient, since other sites contribute relatively little

additional information. "

Researchers hope MRI can reduce time to diagnosis of ankylosing spondylitis

The Dutch researchers tested interreader reliability of SI-joint MRI in 68

patients with inflammatory back pain. Patients had back pain for less than

two years and met at least four of these five criteria: onset before age 40,

insidious onset, morning stiffness, duration of more than three months, and

improvement with exercise. Alternatively, patients could have three of the

criteria plus night pain.

They investigators write that the study was undertaken in part as an attempt

to find ways to improve the diagnosis of ankylosing spondylitis, of which

sacroiliitis is a characteristic feature. They note that there is currently

a mean lag time of about eight years between the start of symptoms and the

diagnosis of AS.

Patients were scanned in a supine position with a 1.5-T Philips Gyro scan.

The researchers used a coronal oblique scan plan parallel to the length of

the sacrum, one transversal slab positioned cranially to the region of

interest (to diminish flow artifacts) and one positioned frontally through

the bowel and anterior abdominal wall (to diminish motion artifacts of

breathing and bowel movement). The scan observers looked for inflammation

and structural changes, including erosions, sclerosis, and ankylosis. The

regions examined were the subchondral region, bone marrow, joint capsule,

joint space, and retroarticular ligaments. Scans were read by two MRI

readers, and interreader reliability was determined.

The most frequent MRI finding was inflammation of the subchondral region and

bone marrow. Interreader agreement was 85% for inflammation in the right SI

joint and 78% in the left SI joint. Inflammation was detected in 22 of 68

patients, and 10 of these 22 patients also had structural changes.

" One of the important aims of this study was to establish whether

inflammation and structural changes on MRI could reliably be assessed. . . .

With agreement levels around 85% for the presence of inflammation overall

and at different locations, it seems sufficiently high to justify a

conclusion of inflammation made by one observer in clinical practice, " the

authors write.

They also conclude that the search for inflammation can be limited to

looking for bone-marrow edema and/or subchondral inflammation without

requiring examination of other sites such as the joint capsule, joint space,

or retroarticular ligaments, since these added little to the accuracy of the

diagnosis.

The clinical and research usefulness of sacroiliac-joint MRI in diagnosing

inflammatory back pain would be increased by a reliable scoring system for

sacroiliitis on MRI. Van der Heijde tells rheumawire that the Assessment in

Ankylosing Spondylitis (ASAS) Outcome Measures in Rheumatoid Arthritis

Clinical Trials (OMERACT) working group recently reviewed several scoring

methods used in research but concluded that data are insufficient for

preferring one over the others [2].

From the viewpoint of the typical rheumatologist, van der Heijde says that

MRI should be considered in the patient with inflammatory back pain and one

or two other features linked to spondyloarthropathy, such as inflammatory

bowel disease, psoriasis, uveitis, positive family history, heel pain,

peripheral arthritis, dactylitis, good response to nonsteroidal

anti-inflammatory drugs (NSAIDs), or elevated acute-phase reactants. " If the

patient has three or more of these features, information from MRI is not

necessary to make the diagnosis, " she adds. She also recommends combining

information from MRI with that from conventional radiographs for diagnosis

of sacroiliitis in recent-onset inflammatory back pain [3].

Sources

1. Heuft-Dorenbosch L, Weijers R, Landewe R, et al. Magnetic

resonance imaging changes of sacroiliac joints in patients with recent-onset

inflammatory back pain: inter-reader reliability and prevalence of

abnormalities. Arthritis Res Ther 2006; 8:R11.

2. Landewé R, Hermann KG, van der Heijde D, et al. Scoring

sacro-iliac joints by magnetic resonance imaging, a multiple-reader

reliability experiment. J Rheumatol 2005; 32:2050-2055.

3. Heuft-Dorenbosch L, Landewé R, Weijers R, et al. Combining

information obtained from MRI and conventional radiographs in order to

detect sacroiliitis in patients with recent-onset inflammatory back pain.

Ann Rheum Dis 2005; DOI:10.1136/ard.2005.044206.

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