The growth of the lumbar vertebral canal
The aim of the study was to examine the growth and the shape of the lumbar vertebral canal throughout life. A unique collection in the Natural History Museum, London provided many infant spines along with adult ones in perfect condition. Unmagnified silhouette photographs were taken of the vertebrae and the size of the canals was measured by a computer. It was found that in midsagittal diameter and cross-sectional area the vertebral canal was fully matured by 1 year of age at L1-L4 and by 6 at L5. The midsagittal dimension was larger in many infant spines that in the adult. The interpedicular diameter grew at L1 until 10 years of age, at L2-L5 until adulthood while the perimeter did not change at the cranial 3 vertebrae, however, grew at the caudal levels until 16 years of age. The shape of the vertebral canal showed changes at the cranial four levels until adulthood as regards the trefoil configuration, the circularity and the situation of the centroid. At L5 circularity increased throughout life showing degenerative changes by increasing age. Trefoil configuration appeared in adulthood at L5 and its degree as well as its incidence did not change throughout life and generally was not associated with degenerative changes. In the second study anthropometric measurements of head circumference, clavicle length and lower limb lengths were compared to vertebral canal size taken from CT scans. The midsagittal diameter of the canal did not correlate with the other bone measurements, however, the interpedicular diameter showed a relationship. This dimension has significant growth potential like the clavicles and the long bones and to a less extent the skull. This also shows that the neural contents probably exert an effect on the growth of the canal. In the third study MRI measurements of adult lumbar canals were compared to the obstetric data of the subjects to investigate whether on adverse ante-natal environment can cause a disturbance in canal growth, thus, a small canal.