Trabecular Analysis of the Distal Radial Metaphysis during the Acquisition of Crawling and Bipedal Walking in Childhood: A Preliminary Study

In modern day populations, children following a normal pattern of development acquire independent bipedal locomotion between the ages of 9 and 18 months. Variability in the timing of this psychomotor developmental milestone depends on various factors, including cultural influences. It is well known that trabecular bone adapts to changes in biomechanical loading and that this can be influenced by alternative locomotor modes, such as crawling, which may be adopted before the acquisition of bipedal locomotion. With the onset of crawling, increased loading of the distal metaphysis of the radius, a component of the wrist, may lead to changes in trabecular bone architecture. To test this hypothesis, eight distal metaphyses of the radius of nonpathological children aged 0 to 3 years from the Bologna collection of identified skeletons were μCT-scanned at a resolution of 10.7 μm. The microarchitectural parameters of the trabecular bone (trabecular bone volume fraction, trabecular thickness, trabecular spacing, and trabecular ellipsoid factor) were quantified for the entire metaphysis and 3D morphometric maps of the distribution of the bone volume fraction were generated. Analysis of these microarchitectural parameters and the 3D morphometric maps show changes in the trabecular bone structure between 6 and 15 months, the period during which both crawling and bipedalism are acquired. This preliminary study analyzed the trabecular structure of the growing radius in three dimensions for the first time, and suggests that ontogenetic changes in the trabecular structure of the radial metaphysis may be related to changes in the biomechanical loading of the wrist during early locomotor transitions, i.e. the onset of crawling. Moreover, microarchitectural analysis could supply important information on the developmental timing of locomotor transitions, which would facilitate interpretations of locomotor development in past populations.