Increased bone mineral density at the hypoxia prone site of the juxta-articular metacarpal bone in patients with limited systemic sclerosis: a cross-sectional study

OBJECTIVES Low levels of oxygen has been shown to be involved in the induction of osteogenesis, particularly in bone repair. It is unknown whether hypoxia leads to osteogenesis at the hypoxia prone skeletal sites in limited systemic sclerosis. This study determined the total and trabecular volumetric bone mineral density (vBMD) at the hypoxia prone site of the juxta-articular metacarpal bone. METHODS In this cross-sectional study, female patients with limited systemic sclerosis were included and compared to healthy controls. Peripheral quantitative computed tomography was used to measure cross-sectional area, total vBMD, and trabecular vBMD at the radius, the tibia and the third metacarpal bone. Disease severity was assessed by the modified Rodnan Skin Score. RESULTS Twenty consecutive patients were included in the sclerosis group and 20 in the control group. Mean age was 60 years (range 52-68 years), and mean disease duration was 45 months (range 4-156 months). Age, height, and weight were comparable between the groups. The mean modified Rodnan Skin Score was 1.78 (range 0 to 8). The sclerosis group showed both higher total and trabecular vBMD at the distal metacarpal bone (p=0.05 and 0.04, respectively). vBMD of the tibia and radius did not differ in both groups. CONCLUSIONS vBMD at the juxta-articular metacarpal bone in patients with limited systemic sclerosis is increased, possibly due to an alteration in local bone metabolism and hypoxia induced local osteogenesis.