Recent roentgenographic studies suggest that periosteal apposition adds femoral cortical bone faster than it is lost by endosteal involution, so that cortical bone area increases with age. A comparison was made of direct and roentgenographic measurements of femoral cortical bone using femora from 23 females and 20 males of a prehistoric Mississippian population dated at A.D. 1540–1700. The comparison revealed that significant errors existed in the technique of radiographic measurement (p<0.000001), in estimating male and female cortical thickness (p<0.000001), and the changes in thickness with age (p<0.000001). There was no significant interaction of the variables: age, sex, and method.

The errors arose partly from the inability of the roentgenograph to reveal clearly endosteal porosity, and partly in the assumption that the medial and lateral cortical wall thickness would be representative of the mean cortical thickness.

The reduction in cortical thickness (11.3% males and 29.3% females) with age as measured directly is comparable with loss in modern populations.