Purposes: The detailed understanding of the anatomy and timing of ossification centers is indispensable in both determining the fetal stage and maturity and for detecting congenital disorders. This study was performed to quantitatively examine the odontoid and body ossification centers in the axis with respect to their linear, planar and volumetric parameters.
Methods: Using the methods of CT, digital image analysis and statistics, the size of the odontoid and body ossification centers in the axis in 55 spontaneously aborted human fetuses aged 17-30 weeks was studied.
Results: With no sex difference, the best fit growth dynamics for odontoid and body ossification centers of the axis were, respectively, as follows: for transverse diameter y = -10.752 + 4.276 × ln(age) ± 0.335 and y = -10.578 + 4.265 × ln(age) ± 0.338, for sagittal diameter y = -4.329 + 2.010 × ln(age) ± 0.182 and y = -3.934 + 1.930 × ln(age) ± 0.182, for cross-sectional area y = -7.102 + 0.520 × age ± 0.724 and y = -7.002 + 0.521 × age ± 0.726, and for volume y = -37.021 + 14.014 × ln(age) ± 1.091 and y = -37.425 + 14.197 × ln(age) ± 1.109.
Conclusions: With no sex differences, the odontoid and body ossification centers of the axis grow logarithmically in transverse and sagittal diameters, and in volume, while proportionately in cross-sectional area. Our specific-age reference data for the odontoid and body ossification centers of the axis may be relevant for determining the fetal stage and maturity and for in utero three-dimensional sonographic detecting segmentation anomalies of the axis.
Keywords: Axis vertebra; Growth dynamics; Human fetus; Odontoid process; Ossification center; Size.