Bone impairment assessed by lumbar spine trabecular bone score (TBS) and HR-pQCT in male ankylosing spondylitis patients

Abstract

Objectives. Low bone mineral density (BMD) and osteoporosis diagnosis in AS patients is based on data using dual-energy X-ray absorptiometry (DXA), which may be difficult to interpret due to the presence of syndesmophytes. The objective of this study is to evaluate bone mass and quality using areal (a) BMD, lumbar spine trabecular bone score (TBS) and HR-pQCT parameters in AS patients compared with healthy controls (HC). Methods. TBS and aBMD were evaluated using DXA. Volumetric bone mineral density (vBMD), bone microarchitecture and stiffness were analyzed at the distal tibia and radius using HR-pQCT. Seventy-three AS male patients and 52 agematched HC were evaluated. Results. Lower TBS values were observed in AS patients compared with HC (1.314 ± 0.121 vs. 1.396 ± 0.070, p<0.001); however, no difference was observed in lumbar spine aBMD between these two groups (1.080 ± 0.193 vs. 1.041 ± 0.118 g/cm2 , p=0.11). Lower trabecular vBMD (162.1 ± 39.6 vs. 186.8 ± 39.9 mg HA/cm3 , p<0.001), lower structural parameters Tb.Th (0.074 ± 0.012 vs. 0.080 ± 0.013 mm, p=0,044) and Tb.Sp (0.497 ± 0.110 vs. 0.448 ± 0.086 mm, p=0,039) and lower strength parameters stiffness (254250.8 ± 48477.7 vs. 291770.3 ± 52858.4 N/mm, p<0.001) and F.Load (12098.6 ± 2240. vs 13770.2 ± 2388.1 N, p=0,001) were observed in the trabecular compartment at the distal tibia in AS patients compared to HC. Conclusion. The lumbar spine TBS and HR-pQCT imaging measurements are superior technologies to detect impairment of bone mass and quality in AS patients compared to healthy subjects.