Background The disease course of non-radiographic axial spondyloarthritis
(nr-axSpA), usually detected by magnetic resonance imaging (MRI), is often
unclear at the time of diagnosis. We investigated which MRI findings in the
sacroiliac joints (SIJs) and lumbar spine including the facet joints can be
observed over a two-year period in patients with newly diagnosed active
inflammatory lesions in the SIJs fufilling the Assessment of SpondyloArthritis
International Society criteria (ASAS) for Axial Spondyloarthritis (axSpA).
Methods Patients (n=56, age<45 years, 30 female and 26
male, symptom duration 3–30 months) consecutively diagnosed with
unilateral or bilateral sacroiliitis through MRI during an 18-month period and
meeting the ASAS criteria for axial SpA were followed up for two years. Clinical
examination, laboratory tests and an MRI of the sacroiliac joints (SIJs), lumbar
spine and facet joints were performed at diagnosis (t0), after one year (t1) and
after two years (t2).
Results At t0, 31 patients (55%) with a bone marrow edema (BME) in
the SIJs already had detectable changes in the facet joints, including signs of
inflammation or degenerative changes. At t2, patients with facet joint
involvement in t0 not only had more significant changes in the SIJs but also
significantly more changes in the vertebral bodies, including BME, fat lesions
and vertebral body erosions than patients without changes in the facet joints at
t0. All vertebral changes described might be potential indicators of progression
to radiographic axSpA (r-axSpA). These MRI findings are seen more frequently
over a short period of time than previously thought.
Conclusions MRI progression in the SIJs over a two-year period is
associated with increasing damage to the facet joints and vertebral bodies.
Involvement of the facet joints in the early stages of the disease may indicate
increasing changes in the vertebral bodies and thus a less favourable course of
axSpA.