Ossification center of the humeral shaft in the human fetus: a CT, digital, and statistical study.

PURPOSE: The knowledge of the development of the humeral shaft ossification center may be useful both in determining the fetal stage and maturity and for detecting congenital disorders, as well. This study was performed to quantitatively examine the humeral shaft ossification center with respect to its linear, planar, and volumetric parameters.

MATERIALS AND METHOD: Using methods of CT, digital image analysis, and statistics, the size of the humeral shaft ossification center in 48 spontaneously aborted human fetuses aged 17-30 weeks was studied.

RESULTS: With no sex differences, the best-fit growth dynamics for the humeral shaft ossification center was modeled by the following functions: y = -78.568 + 34.114 × ln (age) ± 2.160 for its length, y = -12.733 + 5.654 × ln(age) ± 0.515 for its proximal transverse diameter, y = -4.750 + 2.609 × ln (age) ± 0.294 for its middle transverse diameter, y = -10.037 + 4.648 × ln (age) ± 0.560 for its distal transverse diameter, y = -146.601 + 11.237 × age ± 19.907 for its projection surface area, and y = 121.159 + 0.001 × (age)4 ± 102.944 for its volume.

CONCLUSIONS: With no sex differences, the ossification center of the humeral shaft grows logarithmically with respect to its length and transverse diameters, linearly with respect to its projection surface area, and fourth-degree polynomially with respect to its volume. The obtained morphometric data of the humeral shaft ossification center are considered normative for respective prenatal weeks and may be of relevance in both the estimation of fetal ages and the ultrasonic diagnostics of congenital defects.