Variations in the relationship between the diaphysis and the epiphyses of the tibia

In all 56 tibiae from Lapps and 56 tibiae from Norwegians have been studied. These ethnic groups represent different weight bearing situations. Variables expressing adaptation to non-axial loading are dealt with. The bone is mainly studied in the AP and the ML planes, as well as in the three dimensional space. The material is analyzed statistically. The distribution form is examined and the deviations from normality are found to be moderate. Mainly positive skewness occurs. Platykurtosis is found as often as leptokurtosis. The deviations from a standard normal distribution are not supposed to affect the results significantly. There is a non-systematic pattern of distribution. The variability is generally lower in Lapps than in Norwegians. The standard deviation shows highest numerical values in indices, lowest in linear variables. Systematic group differences, especially in similar variables, are supposed to be of greater importance than isolated differences. The variables giving deviations from the reference planes or the diaphyseal axis, show the largest and the consistent left-right differences. In linear variables Lapps and females show lower mean values than males and Norwegians, respecitvely. In linear variables giving deviations from the reference planes, in angular variables and in indices, Lapps usually show the highest mean values. Lapps tend to show larger sex differences in variables giving deviations from the reference planes or the diaphyseal axis. However, the sex differences within the Lapps are small. The variations of the tibia are supposed to be the results of mechanical factors in bone remodelling. The epiphyseal-metaphyseal parts tend to have a constant shape, the adaptations to non-axial loading predominantly appearing in the diaphysis. The relation between the weight bearing line and the diaphyseal axis is discussed, particularly regarding the ML stability mechanism of the knee joint. The occurrence of torsion and its influence upon the AP and ML projected values regarding the relationship between the epiphyses and the diaphysis are discussed.