Bone Abstracts

Children with cystinosis have numerous risk factors for impaired bone accrual. We used state-of-the-art quantitative imaging of bone microarchitecture (HR-pQCT) to measure trabecular and cortical microstructure and bone strength in children and adolescents (5-20yrs) with cystinosis. We enrolled 20 cystinosis patients and recruited 34 healthy age- and gender- matched controls. Distal radius and tibia HR-pQCT scans (XtremeCT II, Scanco Medical) were acquired 2 mm proximal to the proximal margin of the growth plate or remnant. Diaphyseal radius and tibia scans were centered at an offset from the same landmark, corresponding to 30% of limb length. Bone volumetric density and microstructure were measured using an automated image analysis pipeline optimized for pediatric scans. Micro-finite element analysis (μFEA) was applied to estimate bone strength. One-way ANOVA regression, adjusting for age and sex was used to test for differences in bone measures between cystinosis and healthy control groups. After correcting for age and sex (Table 1 and 2), cystinosis patients had significantly lower bone strength, most prominently at the distal tibia (-25%, p<0.008) where smaller cross-sectional area, thinner cortices, and deficits in trabecular architecture were all significant. Smaller bone size was observed at all sites, suggesting a systemic lag in bone development. Our findings indicate cystinosis subjects have significantly impaired bone strength and abnormal architecture at the weight-bearing tibia, and will consequently have an elevated lifetime risk of sustaining a fragility fracture.

Disclosure: The authors declared no competing interests.