Abstract:

Objective：To find the correlation of wrist bone mineral density (BMD) to wrist synovitis and erosion, by comparing wrist BMD and ultrasonography.Methods: A number of 80 female RA patients were examined by BMD measurement of the femoral neck, spine and non-dominant wrist using dual-energy X-ray absorptiometry (DXA). Synovitis of the wrist was examined by ultrasonography. The wrist joint (radiocarpal joint, dorsal midline, and carpoulnar joint) was assessed in the same side of DXA, with transverse and longitudinal scans for USGS synovial hypertrophy and proliferation, tenosynovitis,tendinitis and bone erosion. Colour and power doppler ultrasonography (PDUS) were used to sum the synovitis score.Results:We found: (1) In the study, 80 female RA patients were enrolled, the mean age was 54.6±13.3 (27.0-80.0) years, the disease duration was 48 (12-116) months, and the body Mass Index was 23.0±4.0 (14.8-31.2) kg/m2. The Wrist BMD (g/cm2) in RA significantly reduced, compared with normal controls(0.297±0.121 vs. 0.420±0.180，P<0.01). (2) The Wrist BMD (g/cm2) exceeded in early RA compared with the established RA(0.326±0.103 vs. 0.285±0.132，P<0.01); the positive rate of severe osteoporosis in wrist was lower in early RA compared with the established RA(47.8% vs. 64.9%, P<0.05); the positive rate of bone erosion in wrist by ultrasound was lower in early RA compared with the established RA (39.1% vs.  56.1%, P<0.01). (3) The wrist BMD (g/cm2) in RA with high disease activity reduced compared with moderate and low disease activity (0.267±0.140 vs. 0.280±0.126) and (0.267±0.140 vs. 0.320±0.103) respectively, P<0.05). The percentages of positive ACPA in the high and moderate disease activity groups were significantly higher than those in the remission group (85% vs. 81.8% and 92.6% vs.  81.8%, respectively). DAS28ESR was correlated with wrist BMD (r=-0.288， P<0.01). (4) A significant positive correlation was found between wrist and spine/femur BMD (r=0.634， P<0.01， r=0.795， P<0.01), and a negative correlation between wrist and disease duration and DAS28ESR (r=-0.286，r=-0.301，P<0.01). There was a highly significant positive correlation between wrist BMD and femur BMD (r=0.95，P<0.05). (5) RA patients in wrist osteoporosis group had higher RF positive rate and ACPA rate than wrist osteopenia group (75.5% vs.  55.6%，P<0.05,100% vs.  83.3%， P<0.05). The patients of BMD osteoporosis group had higher DAS28ESR compared with osteopenia group (5.3±1.8 vs.  3.7±1.5， P<0.01). The percentages of synovitis (61.5% vs.  51.7%, P<0.05), tendenitis (14.3% vs. 10.0%, P<0.05) and bone erosion (54.2% vs.  46.2%, P<0.05) in wrist by ultrasonography in osteoporosis group were higher than those of osteopenia group. (6) The wrist BMD in ne-gative bone erosion group by ultrasonography was lower than that in positive bone erosion group ［(0.333±0.107) g/cm2 vs.  (0.264±0.125) g/cm2, P<0.01］, also the PDUS score was higher than positive bone erosion group (4.53±1.40 vs.  2.55±2.66，P<0.01). Compared with negative bone erosion group, the patients in positive bone erosion group had longer disease duration (96.0±104.7) months vs.  (66.2±78.0) months， P<0.05), higher percentage of RF (81.0% vs.  53.8%，P<0.01), ACPA (92.7% vs. 79.5%, P<0.05). and higher DAS28ESR (5.4±1.8 vs.  4.2±2.0，P<0.05). The percentage of wrist synovitis in positive bone erosion group was higher (75.6% vs.  30.8%，P<0.01) than that of negative bone erosion group, and moreover, the percentage of severe osteoporosis in the wrist was significantly higher (75.0% vs.  46.4%， P< 0.01). (7) A stepwise multivariate linear regression model was constructed to explore the relationship between the different clinical factors studied and a low wrist BMD. Statistically significant variables were age (P=0.001), disease duration (P=0.017), DAS28ESR (P=0.021), and ACPA (P=0.05).Conclusion:This study shows a highly significant correlation between hand BMD with disease duration and disease activity, and female RA patients with high titer of ACPA have lower wrist BMD.

Key words: Arthritis, rheumatoid, Bone density, Carpal joints, Absorptiometry, photon, Ultrasonography