Effect of rheumatoid arthritis and age on metacarpal bone shaft geometry and density: A longitudinal pQCT study in postmenopausal women.

Objective: This study aimed to elucidate the effects of changes in the geometry and density of the metacarpal bone of patients with rheumatoid arthritis (RA).

Methods: This prospective study included consecutive postmenopausal RA patients who met the American College of Rheumatology Criteria and healthy controls (HC). Peripheral quantitative computed tomography scans at 50% of the total metacarpal shaft (third metacarpal bone) were obtained at baseline and follow-ups. Use of bisphosphonates (BP), glucocorticoids (GC), biologics, and disease-modifying anti-rheumatic drugs (DMARD) was monitored (baseline to follow-up). Total cross-sectional area (CSA), cortical-transitional zone and compact zone CSA, cortical volumetric bone mineral density, and compact cortex porosity were measured. A linear mixed-effects model was used to determine significant differences in the rate of change in the RA and control groups and in RA patient subgroups.

Results: Thirty-nine RA patients and 42 consecutive postmenopausal HC were followed for 63 months. RA and HC depicted a time-dependent increase of medullary CSA (+0.41 mm/year, P < 0.0001), while total CSA remained stable (P = 0.2). RA status was associated with a loss of cortical bone mineral density (interaction: -3.08 mg/mm; P = 0.014). In RA subgroup analysis, GC use ≥5 mg/day was positively correlated with a fourfold increase of medullary CSA (0.67 mm/year P = 0.009), which resulted in a three- to fourfold loss of cortical density (-6.6 mg/mm/year; P = 0.002) and cortical CSA (-0.57 mm/year, P = 0.004). Patients with high disease activity and high GC dose at baseline demonstrated an increase in the total CSA (0.29 mm/y; P = 0.049) and a loss of cortical BMD (-5.73 mg/mm/y; P = 0.05) despite good clinical response.

Conclusion: Increase in medullary metacarpal CSA and thinning of the cortical CSA are physiological and time dependent. RA status is associated with loss in cortical density. Even upon biological therapy, low glucocorticoid dose affects metacarpal bone shaft geometry and density over time.