Microarchitectural analysis of the metacarpophalangeal joint using HR-pQCT in patients with rheumatoid arthritis: A comparison with healthy controls.

OBJECTIVE

To investigate which joint microarchitectural parameters measured by high-resolution peripheral quantitative computed tomography (HR-pQCT) serve as imaging markers for rheumatoid arthritis (RA).

METHODS

The second and third metacarpophalangeal (MCP) joints of 50 patients with RA and 50 healthy controls (HCs) (aged 50-79 years, all females) were scanned using a HR-pQCT. Joint space, trabecular bone microarchitecture, and erosion were measured and compared between RA patients and HCs.

RESULTS

There were no differences in joint space parameters between RA patients and HCs. For bone microarchitecture, RA patients had lower trabecular bone mineral density (127 vs. 167 mg/cm), thinner trabecular thickness (0.20 vs. 0.21 mm), fewer trabecular number (1.49 vs. 1.55 /mm), more rod-like structure (1.68 vs. 1.23), and poorer trabecular connectivity (4.51 vs. 5.72 /mm) than HCs. Regarding erosion, RA patients had a higher number of erosions per joint (36/100 vs. 18/100), larger volume (4.62 vs. 1.89 mm), and longer width (2.40 vs. 1.82 mm) and longer length (2.34 vs. 1.64 mm) than HCs. Most of the erosions in HCs were <5 mm in volume (95 %) and located on the radial side (85 %). When erosions <5 mm were compared between RA patients and HCs, there were no differences in their location or morphology.

CONCLUSIONS

Deterioration of bone microarchitecture and existences of erosions >5 mm in the MCP joints are sensitive imaging markers of RA. Erosions <5 mm in RA patients may include not only early pathological erosion but also physiological erosion because even HCs can have erosions <5 mm.