Biostatics of the tibial shaft

In all, 56 tibiae from Lapps and 56 tibiae from Norwegians have been studied. These ethnic groups represent different weight bearing situations. Only measurements referring to the diaphysis are presented. The bones are studied in the AP and ML planes and at different transverse sections. The material is analyzed statistically. The distribution form is examined. Chiefly positive skewness occurs. Platykurtosis is found twice as often as leptokurtosis. A differentiated pattern of distribution seems to be the case regarding measurements in the lower extremities. This corresponds to the influence of variable hereditary and external factors. Divergencies from standard normal distribution is compared with differences between groups. In some cases differences are influenced by platykurtosis and skewness. Divergence from standard normal distribution could not be traced back to measuring errors, special features of the bone or special sex characteristics. The divergencies are not supposed to affect the results to any noteworthy extent. Female Lapps show small variances, female Norwegians great variances. In linear variables Lapps generally show smaller values than Norwegians, females smaller values than males. Regarding linear measurements, sex differences are a little more marked than differences between the two ethnic groups. The opposite is the case regarding the angular measurements and the indices. The sex differences in linear measurements are smaller in Lapps than in Norwegians. The opposite is the case regarding the length of the bone. In Lapps, angular measurements and indices show no significant sex differences. Regarding linear measurements, differences between the ethnic groups are mostly due to differences between the males. The opposite may be said about the indicnes. The variations of the tibia recorded and discussed in the present paper are the results of mechanical factors influencing the basic processes in functional bone remodelling. The periosteal ossification is particularly involved in the dimensions of the shaft, the epiphyseal cartilage in the length dimensions. Particularly important is the relation between the weight bearing line and the diaphysial axis of the bone, and the muscles activated by variation is this relation.