Background Periarticular bone loss is a typical finding in rheumatoid arthritis (RA) patients. However, this structural bone change is yet insufficiently characterized. Larger studies assessing periarticular bone composition in healthy controls (HC) and RA patients by high-resolution imaging have not been undertaken and have not been validated against standard measurement at the distal radius.
Objectives To assess periarticular bone by high-resolution peripheral quantitative computed tomography (HR-pQCT) in the metacarpal heads and compare it with standard measurement in the distal radius in HC and anti-citrullinated peptide antibodies-positive (ACPA+) RA patients.
Methods HR-pQCT (XtremeCT, Scanco, Switzerland) scans of the distal radius and of the metacarpal head 2 joints of HC and RA patients were performed. In contrast to previous studies the entire metacarpal head was assessed. After motion grading of the images by two independent readers, images with a motion grade more than 3 were excluded. A graphical objet (GOBJ) was generated and evaluated using the standard evaluation protocol for the radius provided by the manufacturer for both, the metacarpal head and the distal radius. In the last step, bone density values such as average bone density (D100 [mg HA/cm3]), bone volume/total volume (BV/TV), number of trabeculae (Tb N [1/mm])) were determined and compared between (i) the metacarpal head and the radius and (ii) between HC and RA patients.
Results 222 subjects (110 HC and 112 RA) were analyzed. Sex and age distribution were balanced between HC (f/m: 58/52; 50.1±16.1 years) and RA patients (f/m: 53/59; 53.2±12.4 years; disease duration 9.2±8.7 years). Bone density in HC was 288.3±54.7 mg HA/cm3 in the distal radius and 294.4±43.3 mg HA/cm3 in the metacarpal head with significant correlation (ρ=0.583 (p<0.001)) (Fig1a, top row). Respective bone densities in RA patients were 269.8±49.6 mg HA/cm3 and 263.3±46.0 mg HA/cm3 with significant correlation (ρ=0.632 (p<0.001)) (Fig. 1a, bottom row). Similar correlations were found for BV/TV (HC: ρ=0.590, p<0.001, RA: ρ=0.687, p<0.001) and Tb N (HC: ρ=0.576, p<0.001, RA: ρ=0.705, p<0.001). Comparing bone densities between HC and RA patients we found significant bone loss in both the metacarpal head (p<0.001, U=3834.5, Z=-4.860) and the distal radius (p=0.018, U=2700.5, Z=-2.357) in RA patients. Examples of measurements in the metacarpal heads of HC and RA patients are shown in Figure 1b.
Conclusions In this large study, we show that the assessment of periarticular bone structure in metacarpal heads is feasible and correlates well with standard measurement in the distal radius. Furthermore, we show significant bone loss in RA patients as compared to HC in both anatomical sites.
Disclosure of Interest None declared