Fractal analysis of subchondral bone changes of the hand in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic and systemic inflammatory disorder. Conventional radiography, a widely available and cost-effective examination method, remains the standard of reference for the detection and quantification of joint involvement in RA. Fractal dimension (FD) of the trabecular bone structure has been proven to correlate with the bone's physical properties. The present study was designed to use fractal analysis to validate radiograph changes in the hand of RA patients. This study retrospectively evaluated the hand radiographs of 108 subjects. Fifty-four patients were suffering from RA, of which 18 were men and 36 were women. Their ages ranged from 25 to 90 years. The hand radiographs of 54 healthy patients, 18 men and 36 women (age range 23–88 years), were used as the control group. Bone structure value (BSV) is a critical parameter for the assessment and analysis of bone microarchitecture. The BSVs were calculated over the fractal dimension using the Brownian motion. The BSV calculated for ROI showed a significant difference in ROI5 (0.210 ± 0.045), ROI6 (0.186 ± 0.066), and ROI11 (0.201 ± 0.056) in patients with RA, in comparison to the CG (P < 0.05). A significant correlation was observed between anti-CCP and ROI4, ROI5, ROI6, ROI9, and ROI12 in seropositive RA patients (post hoc test (Bonferroni) P <0.001). This study demonstrates that the bone textural image analysis technique can be used to quantify the radiographic changes in RA hands, based on comparisons of FDs.