Morphometric study of the T6 vertebra and its three ossification centers in the human fetus

PURPOSE: Knowledge on the normative growth of the spine is critical in the prenatal detection of its abnormalities. We aimed to study the size of T6 vertebra in human fetuses with the crown-rump length of 115–265 mm. MATERIALS AND METHODS: Using the methods of computed tomography (Biograph mCT), digital image analysis (Osirix 3.9) and statistics, the normative growth of the T6 vertebral body and the three ossification centers of T6 vertebra in 55 spontaneously aborted human fetuses (27 males, 28 females) aged 17–30 weeks were studied. RESULTS: Neither male–female nor right–left significant differences were found. The height, transverse, and sagittal diameters of the T6 vertebral body followed natural logarithmic functions as y = −4.972 + 2.732 × ln(age) ± 0.253 (R (2) = 0.72), y = −14.862 + 6.426 × ln(age) ± 0.456 (R (2) = 0.82), and y = −10.990 + 4.982 × ln(age) ± 0.278 (R (2) = 0.89), respectively. Its cross-sectional area (CSA) rose proportionately as y = −19.909 + 1.664 × age ± 2.033 (R (2) = 0.89), whereas its volumetric growth followed the four-degree polynomial function y = 19.158 + 0.0002 × age(4) ± 7.942 (R (2) = 0.93). The T6 body ossification center grew logarithmically in both transverse and sagittal diameters as y = −14.784 + 6.115 × ln(age) ± 0.458 (R (2) = 0.81) and y = −12.065 + 5.019 × ln(age) ± 0.315 (R (2) = 0.87), and proportionately in both CSA and volume like y = −15.591 + 1.200 × age ± 1.470 (R (2) = 0.90) and y = −22.120 + 1.663 × age ± 1.869 (R (2) = 0.91), respectively. The ossification center-to-vertebral body volume ratio was gradually decreasing with age. On the right and left, the neural ossification centers revealed the following models: y = −15.188 + 6.332 × ln(age) ± 0.629 (R (2) = 0.72) and y = −15.991 + 6.600 × ln(age) ± 0.629 (R (2) = 0.74) for length, y = −6.716 + 2.814 × ln(age) ± 0.362 (R (2) = 0.61) and y = −7.058 + 2.976 × ln(age) ± 0.323 (R (2) = 0.67) for width, y = −5.665 + 0.591 × age ± 1.251 (R (2) = 0.86) and y = −11.281 + 0.853 × age ± 1.653 (R (2) = 0.78) for CSA, and y = −9.279 + 0.849 × age ± 2.302 (R (2) = 0.65) and y = −16.117 + 1.155 × age ± 1.832 (R (2) = 0.84) for volume, respectively. CONCLUSIONS: Neither sex nor laterality differences are found in the morphometric parameters of evolving T6 vertebra and its three ossification centers. The growth dynamics of the T6 vertebral body follow logarithmically for its height, and both sagittal and transverse diameters, linearly for its CSA, and four-degree polynomially for its volume. The three ossification centers of T6 vertebra increase logarithmically in both transverse and sagittal diameters, and linearly in both CSA and volume. The age-specific reference intervals for evolving T6 vertebra present the normative values of potential relevance in the diagnosis of congenital spinal defects.