Quantitative anatomy of the primary ossification center of the femoral shaft in human fetuses

PURPOSE: Early clinical distinction of congenital defects in the femur is extremely important, as it determines the prognosis of the development of the lower limb. This study was performed to quantitatively examine the primary center of ossification in the femoral shaft with respect to its linear, planar, and volumetric parameters. MATERIALS AND METHODS: Using methods of CT, digital-image analysis, and statistics, the size of the primary ossification center of the femoral shaft in 47 spontaneously aborted human fetuses aged 17–30 weeks was studied. RESULTS: With no sex and laterality differences, the best fit growth dynamics for femoral shaft ossification center was modelled by the following functions: y = 5.717 + 0.040 × (age)(2) ± 2.905 (R (2) = 0.86) for its length, y = −3.579 + 0.368 × age ± 0.529 (R (2) = 0.88) for its proximal transverse diameter, y = −1.105 + 0.187 × age ± 0.309 (R (2) = 0.84) for its middle transverse diameter, y = −2.321 + 0.323 × age ± 0.558 (R (2) = 0.83) for its distal transverse diameter, y = −50.306 + 0.308 × (age)(2) ± 18.289 (R (2) = 0.90) for its projection surface area, and y = −91.458 + 0.390 × (age)(3) ± 92.146 (R (2) = 0.88) for its volume. CONCLUSIONS: The size of the femoral shaft ossification center displays neither sex nor laterality differences. The ossification center in the femoral shaft follows quadratic functions with respect to its length and projection surface area, linear functions with respect to its proximal, middle, and distal transverse diameters, and a cubic function with respect to its volume. The obtained morphometric data of the femoral shaft ossification center are considered normative for respective prenatal weeks and may be of relevance in both the estimation of fetal ages and the ultrasound diagnostics of congenital defects.