Background/Purpose : Conventional radiographs (CR) are currently the imaging modality of
choice for evaluation of structural hand osteoarthritis (OA) progression. Lately
Magnetic Resonance Imaging (MRI) has been introduced as a promising tool to detect
both structural and inflammatory hand OA features. No studies have compared the
detection of structural hand OA progression by MRI and CR. The aim was
therefore to evaluate the agreement between 1.0T MRI and CR to detect
structural hand OA progression as well as the sensitivity and specificity of
MRI in comparison to CR.

Methods : We included 69 persons (91% women, mean (SD) age of 68.0 (5.5)
years) from the Oslo hand OA cohort with 1.0T MRI scans and radiographs of the interphalangeal
joints at baseline (2008-09) and 5-year follow-up (2013). Evaluating the paired
radiographs (posteroanterior view) with known time
sequence, the joints were scored for radiographic osteophytes (grade 0-3),
joint space narrowing (JSN) (grade 0-3) and central erosions (absent/present).
Similarly, the joints were scored for MRI-defined osteophytes (grade 0-3),
cartilage space loss (grade 0-3) and erosive damage (grade 0-3) using a
T1-weighted sequence in coronal and sagittal planes. Progression was defined as
an increase of ³1 features. We evaluated the agreement to detect progression
using kappa statistics. The sensitivity and specificity of MRI to detect
progression was calculated using CR as reference. We repeated the analyses focusing
on osteophytes and joint damage separately. Cartilage space loss/JSN and
erosions were evaluated as one combined feature (joint damage) as erosions
likely affect the joint space.

Results: We analysed 549 joints (3 joints missing), of which 131 (23.9%) and
144 (26.2%) showed structural progression by MRI and CR, respectively. We found
moderate agreement between MRI and CR (Table). Structural progression was
detected by both modalities in 79 (14.4%) joints, MRI only in 52 (9.3%) joints
and CR only in 65 (11.8%) joints. The sensitivity of MRI was modest. In joints
with radiographic progression only, progression of osteophytes was most
commonly observed. The specificity of MRI was high, as most joints did not progress by neither MRI nor CR. In joints with
MRI-progression only, progression of joint damage was most frequently seen.

We found similar results with modest
sensitivity of MRI when looking into progression of individual features (Table).
However, MRI detected more joints with incident erosions as compared to CR (35
vs. 25 joints) in joints without erosive changes neither on CR nor MRI at
baseline.

Conclusion: 1.0T MRI is not more sensitive than CR to detect structural hand OA
progression. CR will also assess more joints to a lower price, and should
therefore be the imaging modality of choice rather than 1.0T MRI in clinical
trials on therapies with potential effects on disease progression. Future
studies should compare OA progression by CR and MRI with higher field strength.