Hand bone densitometry associates with nailfold capillaroscopic severity of microvascular damage in systemic...

Patients with systemic sclerosis (SSc) exhibit systemic and more pronounced micro- and macro-architectural bone damage compared to healthy subjects (HS). The extent of the microvascular damage in SSc may be associated with the severity of compromised systemic bone integrity. The aim of this study is to investigate and score the status of the hand bone mineral density (BMD) in patients with SSc, using a new dedicated hand software and to score the microvascular status of the same hands by using nailfold videocapillaroscopy (NVC).

Bone mineral density (BMD/g/cm2) and bone mineral content (BMC/g) of left and right hand using a new hand dedicated software (enCore, GE Lunar Prodigy Bone Densitometer, BMD hand software, USA), as well total BMD of the skeleton (GE Lunar Prodigy Bone Densitometer), were measured in 32 SSc patients classified according to the 2013 ACR/EULAR criteria (mean age 61±14 years, 94% women, 47% (n=13) dcSSc and in 27 age-matched HS. Quality of peripheral microvascular involvement (NVC patterns) was evaluated via standardised NVC analysis including capillary number scoring. SSc organ involvement was evaluated according to the 2023 EULAR recommendations. Statistical analysis included non-parametric and multivariable regression analyses to explore the relationship between capillary density and hand bone status.

A multiple regression analysis demonstrated that left- and right-hand BMD was significantly associated with capillary loss after adjustment for age, sex, BMI, osteoporosis history, grip strength, immunosuppressive therapy and bone-specific treatments (p=0.02 and p=0.03). Interestingly, BMD values were found positively correlated with the absolute number of capillaries per linear millimetre (left hand r=0.6893, p<0.001; right hand r=0.45, p=0.03). A significant negative correlation was also found between left hand BMD (r=-0.5752, p=0.001) with the presence of "late" NVC scleroderma pattern. A significant negative correlation was finally observed between left hand BMD and the presence of dcSSc (r=-0.3836, p=0.036) and the modified Rodnan skin score (r=-0.5811, p=0.002). Moreover, SSc patients exhibited significantly lower hand BMD compared to HS even adjusted for age, sex, BMI and history of osteoporosis.

For the first time, hand local bone status was found significantly associated with hand/fingers NVC microvascular damage in SSc patients, emphasising the effects of capillary loss/local hypoxia on the observed bone loss. At the same time, the results of the regression model reinforced the role of capillary loss as a potential predictor of hand bone quality in SSc patients.