Reduced trabecular bone mineral density and cortical thickness accompanied by increased outer bone circumference in metacarpal bone of rheumatoid arthritis patients: a cross-sectional study

PQCT scans were performed in 50 female RA patients and 100 healthy female controls at the distal epiphyses and shafts of the third metacarpal bone, the radius and the tibia. Reproducibility was determined by coefficient of varia-tion. Bone densitometric and geometric parameters were compared between the two groups and correlated to disease characteristics.Reproducibility of different pQCT parameters was between 0.7% and 2.5%. RA patients had 12% to 19% lower trabecular bone mineral density (BMD) (P ≤ 0.001) at the distal epiphyses of radius, tibia and metacarpal bone. At the shafts of these bones RA patients had 7% to 16% thinner cortices (P ≤ 0.03). Total cross-sectional area (CSA) at the metacarpal bone shaft of pa-tients was larger (between 5% and 7%, P < 0.02), and relative cortical area was reduced by 13%. Erosiveness by Ratingen score correlated negatively with tra-becular and total BMD at the epiphyses and shaft cortical thickness of all measured bones (P < 0.04).Reduced trabecular BMD and thinner cortices at peripheral bones, and a greater bone shaft diameter at the metacarpal bone suggest RA spe-cific bone alterations. The proposed pQCT protocol is reliable and allows measuring juxta-articular trabecular BMD and shaft geometry at the metacarpal bone.Juxta-articular bone loss is one of the earliest radiographic findings of active rheuma-toid arthritis (RA) [1,2]. Recently, loss of bone mass at the metacarpal shafts meas-ured on plain radiographs of the hand has been found to be predictive of subsequent joint damage in patients with active rheumatoid arthritis [1,3]. So far, reduced bone mass at the metacarpal bone shaft in RA has been documented in a number of stud-ies using Digital X-ray Radiogrammetry (DXR) [1,3-5] or at the hand by Dual X-ray Absorptiometry (DXA) [3,6-8]. Trabecular bone loss in RA patients, however, has on-ly been studied at the iliac crest [9] and at the distal radius [10-12], where it was found to be lower in RA patients than in contro