Background/Purpose:

Early detection of joint inflammation and tissue damage are critical for patient management in rheumatoid arthritis (RA). High-resolution peripheral quantitative computed tomography (HR-pQCT) is an emerging modality for the assessment of bone damage in RA, including erosions and deterioration of bone microarchitecture. The goal of this study was to examine the correlation of structural changes evaluated by HR-pQCT, 3 Tesla (T) MRI and conventional radiographs (CR) in RA.

Methods:

In sixteen RA patients, HR-pQCT of the second and third metacarpophalangeal joints (MCP) as well as the wrist joints, 3 T MRI of the wrists joint and CR of both hands and feet were performed. Ten patients had 1 year follow-up CR. CRs were graded according to the Modified Sharp/van der Heijde Score (MSS). Bone erosions were evaluated in HR-pQCT and MRI for number, grade and maximum dimension. Bone marrow edema pattern (BMEP) was quantified from MRI for volume, signal intensity and lesion burden using in-house developed software. Spearman’s rank correlation coefficients between MSS by CR, bone erosion by HR-pQCT, bone erosion and BME by MRI were calculated.

Results:

Fifteen patients (93.8%) had evidence of erosions in HR-pQCT. MRI erosions and BME were found in 13 patients (81.3%). Baseline total MSS was significantly correlated with HR-pQCT erosion measures, MRI erosion measures and MRI BMEP volume (r = 0.59 – 0.90, p <0.05). The erosion detection sensitivity of MRI was 85.7% (42/49) and CR was 60.9% (53/87) when HR-pQCT was considered as a reference method. In the 10 patients who had both baseline and one year follow up CRs, the mean difference between baseline and follow up MSS (delta MSS) was 1.2. There was no significant correlation between delta MSS and HR-pQCT/MRI erosion measures at baseline, but a trend was observed toward a correlation between delta MSS and MRI BMEP volume and burden.

Conclusion:

HR-pQCT detects more and smaller bone erosions compared to MRI and CR. In addition, 3 T MRI can also provide quantitative measurement of BMEP. From the erosion findings by HR-pQCT, MRI and CR, and the BME observation by MRI, we may suggest the stages of erosion in RA, shown in Figure 1. The combination of HR-pQCT and MRI is a powerful mean to evaluate joint inflammation and bone damage, and MRI BMEP potentially could predict disease progression in patients with RA.

Figure 1. The stages of erosion by HR-pQCT, MRI and CR in RA hands.

As a result of inflammation, initially BMEP will develop without erosion (stage 1). After this stage, early erosion will develop, which can be very small and can be identified only on HR-pQCT, which is the most sensitive modality for the detection of erosion but no on other modalities such as MRI and CR (stage 2). As the disease progresses, the size of erosion becomes larger and can be detected by both HR-pQCT and MRI (stage 3). Finally, the erosion is becoming large enough to be shown by all 3 modalities, CR, HR-pQCT and MRI (stage 4).