Can erosions on MRI of the sacroiliac joints be reliably detected in patients with ankylosing spondylitis - A cross-sectional studyReportar como inadecuado

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Arthritis Research and Therapy

, 14:R124

First Online: 24 May 2012Received: 17 December 2011Revised: 27 March 2012Accepted: 24 May 2012


IntroductionErosions of the sacroiliac joints SIJ on pelvic radiographs of patients with ankylosing spondylitis AS are an important feature of the modified New York classification criteria. However, radiographic SIJ erosions are often difficult to identify. Recent studies have shown that erosions can be detected also on magnetic resonance imaging MRI of the SIJ early in the disease course before they can be seen on radiography. The goals of this study were to assess the reproducibility of erosion and related features, namely, extended erosion EE and backfill BF of excavated erosion, in the SIJ using a standardized MRI methodology.

MethodsFour readers independently assessed T1-weighted and short tau inversion recovery sequence STIR images of the SIJ from 30 AS patients and 30 controls 15 patients with non-specific back pain and 15 healthy volunteers ≤45 years old. Erosions, EE, and BF were recorded according to standardized definitions. Reproducibility was assessed by percentage concordance among six possible reader pairs, kappa statistics erosion as binary variable and intraclass correlation coefficient ICC erosion as sum score for all readers jointly.

ResultsSIJ erosions were detected in all AS patients and six controls by ≥2 readers. The median number of SIJ quadrants affected by erosion recorded by four readers in 30 AS patients was 8.6 in the iliac and 2.1 in the sacral joint portion P < 0.0001. For all 60 subjects and for all four readers, the kappa value for erosion was 0.72, 0.73 for EE, and 0.63 for BF. ICC for erosion was 0.79, 0.72 for EE, and 0.55 for BF, respectively. For comparison, the kappa and ICC values for bone marrow edema were 0.61 and 0.93, respectively.

ConclusionsErosions can be detected on MRI to a comparable degree of reliability as bone marrow edema despite the significant heterogeneity of their appearance on MRI.

AbbreviationsASankylosing spondylitis

BASDAIBath Ankylosing Spondylitis Disease Activity Index

BASFIBath Ankylosing Spondylitis Functional Index 29


BMEbone marrow edema

CIconfidence interval

CRPC-reactive protein

CTcomputed tomography

EEextended erosion


ESSGEuropean Spondylarthopathy Study Group

FIfat infiltration

ICCintraclass correlation coefficient

IQRinterquartile range

HChealthy control

HLA-B27human leucocyte antigen B27

MRImagnetic resonance imaging

N-Anot applicable

NRSnumeric rating scale

NSBPnon-specific back pain

RPreader pair

SIJsacroiliac joint


STIRshort tau inversion recovery sequence

T1FST1-weighted fat saturated sequence

T1SET1-weighted spin echo sequence

T2GET2-weighted gradient echo sequence.

Electronic supplementary materialThe online version of this article doi:10.1186-ar3854 contains supplementary material, which is available to authorized users.

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Autor: Ulrich Weber - Susanne J Pedersen - Mikkel Østergaard - Kaspar Rufibach - Robert GW Lambert - Walter P Maksymowych


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