Third trochanter incidence and metric trait covariation in the human femur.

The relationship between third trochanter incidence and femoral metric trait covariation has been investigated in a group of 60 left human femora. The experimental sample was constructed so that one group consisted of 15 male and 15 female femora which displayed a third trochanter and a second group consisted of an equal number of sexed long bones which lacked this trait. A battery of ten femoral measurements was sorted according to main effects and interactions and respective covariance matrices were tested for equivalence. Covariance matrices of sorted variables determined not to be significantly different were initially subjected to both ANOVA and MANOVA and subsequently to a principal component analysis. Covariance matrices determined to be significantly different were subjected to a principal component analysis separately. Results of this study indicate that third trochanter incidence is associated with short femora displaying robust proximal diaphyses. The gluteus maximus muscle may act as a primary factor governing third trochanter expression. Further, this infracranial discrete trait appears well suited for human taxonomy studies.