[Prenatal development of the human humerus in light of anthropometric examinations].

The study was done on 128 humeral bones (76 male and 52 female; 57 right and 71 left) obtained from 71 fetuses with C-R lengths ranging from 105 to 255 mm. Periosteum and perichondrium were exposed prior to radiography of frontal and lateral aspects using a Microphocus 401 bone X-ray apparatus. Radiographs were digitized with an analogue camera and an A/D converter for transfer to a PC computer. Nine measurements were done for each bone. Changes in proportions (structure-to-shaft ratios) during development were studied using non-linear regression analysis. The number of nutritive vessels in ossifying bone shafts were determined and indices were calculated representing sites of penetration into the humerus. The mean C-R length of the fetus when the first ossification center in the humerus appeared was 20.34 mm (21.75 mm in females and 19.0 mm in males corresponding to gestation age of 7 to 8 weeks). The length of the ossifying shaft increased proportionally to C-R length. The regression equations representing changes in the proportions of the humerus were linear in four cases: minimum anterior-posterior shaft size, minimum medial-lateral shaft size, maximum anterior-posterior condylus size, width of distal cartilage. The relative decrease in the length of the proximal and distal cartilages and their sum was regressed to three hyperbolic functions. The absolute length in mm of these cartilages increased. This change could be expressed with three exponential equations having positive fractional exponents. A single parabolic equation described the increase in the absolute and relative length of the distant chondro-osseous region. Analysis of the number of nutrient vessels, their direction and relation to surrounding structures was done in 76 humeral bones. The results are presented for pooled bones, as well as arranged by side (39 (51.3%) right, 37 (48.7%) left) and gender (54 (71%) male, 22 (29%) female). The number of nutrient foramina varied from one to three. A single nutrient foramen was found in 50%, two were disclosed in 40.85% and three in 9.2% of bones. Furthermore, 70.25% of them were located in zone IV on the anteromedial surface and the medial margin, 10.75% on the anterolateral and 15.7% on the posterior surfaces. The principal nutrient foramen contained an artery accompanied by a relatively large vein. As a rule, accessory foramina contained veins only, but in rare cases a branch of the nutrient artery was also present. All nutrient canals were directed distally. No significant differences were disclosed between right and left, male and female humeral bones as to indices representing location of the nutrient foramina.