There are several different techniques for assessing bone strength and fracture susceptibility in children namely; dual-energy x-ray absorptiometry (DXA), quantitative computed tomography (QCT), plain radiography and magnetic resonance imaging (MRI). The most readily available technique and recommended by the International Society of Clinical Densitometry (ISCD) is DXA. The advantage of DXA is that it is widely available, affords the child a low radiation dose and can assess fracture prone areas of the body with fast scanning times. The main disadvantage of DXA is that it is a two-dimensional technique which measures the ratio of bone mineral content to projected bone area, such that areal bone density is highly dependent on bone size. As a result, reduced bone density in childhood is frequently a reflection of poor growth rather than a true measure of reduced bone strength. Given the limitations of DXA it is not surprising that other imaging techniques are appealing for assessing reduced bone strength and fracture risk. Techniques such as QCT have the advantage of being able to separately measure cortical and trabecular bone densities. Dedicated peripheral QCT scanners can assess fracture prone long bones with minimal radiation exposure and high resolution QCT scanners now give almost in-vivo bone biopsy type outputs of parameters such as trabecular bone volume, trabecular separation etc. However, small measurement regions, long scanning times and a high susceptibility to movement, keep these techniques predominantly in the research arena rather than for routine clinical assessments. The most recently developed technique is MRI. It can be applied to the peripheral or axial skeleton. The advantage of MRI is that it uses non-ionising radiation to assess bone architecture and muscle structure in multiple planes without repositioning. The disadvantages of MRI are that it is time consuming, expensive and has been used only in few research protocols. As with QCT its applicability in clinical practice has yet to be fully assessed. Increasingly, old and new technologies are being combined to fully exploit currently available diagnostic procedures. The improved image resolution of modern DXA scanners has facilitated accurate assessment of osteoporotic vertebral fractures. At the same time, sophisticated intelligent computer software programs have enabled techniques such as textural analysis, shape modelling and finite element modelling to be genuine contenders for the assessment of bone strength in children. How well any of these novel diagnostic tools are incorporated into clinical practice remains to be seen.
27 - 29 Sep 2018
European Society for Paediatric Endocrinology