Background Studies investigating risk of osteoporosis in rheumatoid arthritis (RA) have mainly been conducted in female patients. Bone health in male RA patients is less well studied. High-resolution peripheral quantitative computed tomography (HR-pQCT) is an in vivo imaging technique capable of assessing volumetric bone mineral density BMD (vBMD) and bone microstructure of the peripheral skeleton.
Objectives To investigate bone density, microstructure and biomechanical competence at distal radius in male RA patients using HR-pQCT
Methods This cross-sectional study involved 23 male RA patients (age: 57.5±7.0 years; disease duration: 16.0±11.1 years) with mild disease activity (DAS28 score: 3.3±1.9) and 23 age-matched male healthy controls (age: 58.2±7.1 years). Areal BMD (aBMD) of femoral neck, total hip, lumbar spine (L1-4) and ultradistal radius was measured by dual-energy X-ray absorptiometry (DXA). HR-pQCT at distal radius and micro-finite element (µFE) analysis were performed to assess cortical and trabecular vBMD, microstructure and bone biomechanical properties.
Results RA patients had significantly lower body weight (62.3±10.1kg vs. 68.0±7.3kg, p=0.033). aBMD at femoral and total hip were -10% (p=0.019) and -11% (p=0.037) respectively lower in RA patients. aBMD at lumbar spine (-3%, p=0.447) or ultradistal radius (-8%, p=0.133) did not differ significantly between patients and controls. In contrast, at distal radius, trabecular vBMD was -22% (p=0.002) significantly lower in patients. Indices related to trabecular microstructure, such as trabecular bone volume fraction (-22%, p=0.002), number (-10%, p=0.041), thickness (-15%, p=0.003), separation (-20%, p=0.011), and network inhomogeneity (-33%, p=0.031), were significantly worse in RA patients. Cortical vBMD and cortical thickness were comparable between patients and controls. Indices related to cortical porosity, including pore volume (55%, p= 0.026), pore diameter (6%, p=0.030) and porosity index (57%, p=0.011) were significantly higher in patients. µFE analysis showed that whole bone stiffness and modulus were preserved but failure load (-13%, p=0.031) significantly decreased in patients. Trabecular stress (-17%, p<0.0005) and strain (-14%, p<0.0005) were significantly lower in patients with stress distributed more unevenly. After adjusted for age, disease duration and disease activity, compared with those without wrist deformity (n=12), patients with wrist deformity (n=11) had significantly increased trabecular network inhomogeneity, cortical pore diameter and cortical stress being more unevenly distributed. There was no correlation between use of oral glucocorticoids 6 months prior and vBMD or microstructure.
Conclusions This study shows for the first time a significant deficit in density, cortical and trabecular microstructure and strength at distal radius in male RA patients. Increased cortical porosity is particularly noticeable in RA patients. This structural deterioration is most likely an effect of chronic inflammation rather than steroid therapy.
Disclosure of Interest None Declared