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Quantitative assessment of periarticular osteopenia in patients with early rheumatoid arthritis: a preliminary report

Background: Involvement of the metacarpophalangeal (MP) joints is one of the major problems in patients with rheumatoid arthritis (RA). Although several data about the cumulative influence of steroid intake on bone are available, the course of demineralisation in RA has not been described by quantitative methods until now. Patients and methods: Computed tomography (CT) sections of 96 MP joints in 12 RA patients and of 32 MP joints in four age‐matched healthy controls were investigated. Patients were classified according to Steinbrocker. Densitometric evaluation of subchondral bone density was performed by CT osteoabsorptiometry (CT‐OAM). Quantitative CT‐OAM was used to evaluate mineralisation of the articular surfaces in MP joints. Results: In the distal articular surface of MP joints, the number of density maxima was reduced from 3 to 2.1±0.3, 1.9±0.5 and 1.3±0.3 in RA patients with early, mild to moderate, and severe disease, respectively. Means of calcium concentrations were 633.4±35. 3 mg Ca2+/mL, 518.9±56.2 mg Ca2+/mL, 497.7±23.8 mg Ca2+/mL and 455.1±28.6 mg Ca2+/mL for controls and RA patients with early, mild to moderate, and severe RA, respectively. Mineralisation of the distal articular surface was significantly reduced in all groups of RA patients [probability (p)=0.005]. Regarding the number of density maxima, no differences were detected in the proximal articular surface of normal and RA fingers. However, mineralisation of the proximal articular surface was significantly reduced in all groups of RA patients (p=0.004). Means of calcium concentrations of the proximal articular surface were 494.1±48.5 mg Ca2+/mL, 413.0±16.2 mg Ca2+/mL, 406.0±51.4 mg Ca2+/mL, 390,4±41.1 mg Ca2+/mL for controls and RA patients with early, mild to moderate, and severe RA, respectively. Conclusion: Patients with early and untreated RA show loss of mineralisation and altered morphology of the MP joints of the hand, even before corticosteroid therapy. CT‐OAM provides evidence for an early alteration of functional anatomy in MP joints.