We included into the retrospective study 49 patients who undergone multiparametric MRI of the SIJs due to the clinical suspicion of axSpA.
All examinations were performed between January 2017 and August 2018.
The inclusion criteria were: clinical suspicion of sacroiliitis in the course of axSpA and age between 18 and 45 years.
The exclusion criteria were: age <18 or >45 years,
the lack of clinical data about the reason of referral,
patients with a history of sacroiliac region trauma or neoplasm.
The mean age of qualified patients was 28.9±8.5 years (range 18 - 43 years),
the percentage of females was 63.3% (n=31),
while males 36.7% (n=18).
All examinations were performed in 3.0 Tesla MRI scanner (Achieva,
Philips Healthcare,
Amsterdam,
Netherlands) with the use of 8 channel phased-array XL-torso body matrix coil.
Both SIJs were imaged simultaneously from the anterior to the posterior border in the coronal oblique plane,
parallel to the long axis of the sacral bone.
MR images were retrospectively assessed in random order by two independent observers,
aware of the clinical suspicion of axSpA,
blinded to patients’ identities and clinical findings.
In every patient,
such sequences were individually evaluated: STIR combined with T1-weighted sequence (structural joint assessment),
DWI sequence with b=0 and 800 with ADC map and DCE sequence.
In order to standardize the visual assessment of these sequences,
we used the SPARCC (Spondyloarthritis Research Consortium of Canada) score,
with slight modifications (without the evaluation of depth and intensity of the inflammatory lesions).
In every sequence,
8 sections,
with the longest visible part of the SIJ articular surface (>1 cm),
were chosen.
On every section,
each SIJ was divided into 4 quadrants (upper iliac,
upper sacral,
lower iliac,
lower sacral),
what finally made the number of 64 quadrants evaluated in every sequence.
Each quadrant was separately analysed for the presence of bone marrow oedema/osteitis related to the inflammatory sacroiliitis – the presence of typical subchondral bone marrow oedema lesion (STIR) or restricted diffusion (DWI,
ADC) or contrast enhancement (DCE) was marked as 1,
and the lack of these signs as 0.
Moreover,
every SIJ was assessed in STIR sequence for the presence of other signs of acute inflammatory sacroiliitis – enthesitis,
capsulitis,
and synovitis.
If the active inflammatory lesion according to ASAS criteria was identified in at least one joint of particular patient in the STIR sequence,
a patient was qualified to the group with ASAS positive sacroiliitis.
If particular patient belonged to an ASAS positive sacroiliitis group and additionally had at least one typical axSpA feature,
according to ASAS criteria,
in the next step that patient was included into ASAS axSpA imaging arm positive group.
As only patients suspected of axSpA were included into our study,
there was not any patient fulfilling the clinical arm of ASAS criteria.