Serum levels of osteoprotegerin and receptor activator of nuclear factor kB ligand (RANKL) in children with various stages of chronic renal disease

Abstract

We recruited 93 cases (children with a current fracture, including some with previous fracture) and 32 controls (no current or previous fracture) by approaching families attending our A&E department with a history of trauma and suspected bony injury. The children underwent bone densitometry of the hip, spine and total body and spiral CT of the lower legs with an in-line Mindways calibration phantom. The latter technique provided complete 3-D images of both tibias with associated volumetric densitometry of the different compartments of bone. The vQCT measures of cortical bone were performed in the mid shaft of the left tibia (50% tibia). Measures of trabecular bone were acquired at sites where the distance to the distal tibial inferior articular cartilage corresponded to 6% and 8% of the length of the left tibia. The inferior articular cartilage was selected as a reference point as it is consistent at all ages in children. We obtained data from single tomographic slices of 2.5 mm transectional thickness at a voxel size of 0.5 mm. A threshold algorithm was used to separate cortical and trabecular bone. As previously, we found significant differences in the relationship between the bone parameters-bone mass, areal bone density and bone area-and body size for children who had had a fracture compared with non-fracture subjects (pb0.01). There was a significant difference between the groups in hip cross-sectional area (pb0.05). However, we found no significant difference between the groups in cortical bone volumetric bone density or cross-sectional area at the mid tibia either before or after adjustment for potential confounders. Neither was there any clear difference between the groups in metaphyseal crosssectional area or volumetric density at either the 6% or 8% site. This study confirms previous observations of lower bone mass for body size in children who fracture, and reduced bone size at the hip, but has not as yet indicated that there are significant accompanying changes in bone microarchitecture in the lower legs.