Geometrical assessment of the foetal lumbar vertebral column -- clinical implications

The neural arches, transverse processes, spinous processes, and superior and inferior articular processes of each of the 5 lumbar vertebrae can often be found under the common heading of 'posterior element'. The aim of our study was to assess the changes in geometry of the posterior elements of the foetal lumbar vertebrae during the foetal period. A total of 50 human foetuses, both female and male, from natural abortions, C-R length ranging from 58 to 220 mm, were examined. The methodology of the research included classical anatomical preparation, detailed measurements of the structural elements of the lumbar vertebrae and statistical analysis. Geometrical reconstruction was subsequently performed. The shape of the posterior elements changed gradually from wide and massive to slender. We observed a descending sequence of these alterations, the first vertebra to change being L1, with L5 the last. The dynamic of the change was at its greatest during the first 4 weeks of the period evaluated. On the basis of our observations we concluded that the geometry of the posterior elements of the lumbar vertebrae undergoes a process of a great transformation during the foetal period, a process which progresses dynamically until the 14th week of intra-uterine development. The associations with micro-angiogenesis, the ossification process and the notion of structural adaptation of the lumbar spine to heightening mechanical stress are also discussed.