Masters Theses

Date of Award

8-1998

Degree Type

Thesis

Degree Name

Master of Arts

Major

Anthropology

Major Professor

Richard L. Jantz

Committee Members

Murray Marks, Andrew Kramer, Lyle Konigsberg

Abstract

The purpose of the present study is to examine secular change during the last century in the femur as expressed through external measures. New technologies have greatly impacted nutrition, healthcare, sanitation, activity levels and behavior. Secular changes in stature, body proportion, weight, childhood growth and development, age at menarche, and cranial measures have been documented for many modem industrialized human samples. These secular changes are attributed largely to environmental influences which allow individuals to reach a genetic potential that is environmentally plastic.

My results indicate a statistically significant increase in anterior-posterior elongation of the femoral midshaft from 1840 to the mid 1970's in black females (n = 156), white females (n = 249), black males (n = 202), and white males (n = 388) from the Terry collection and Forensic Data Bank. Additionally, these data demonstrate a statistically significant secular decrease in overall robusticity of the femur midshaft relative to maximum femur length, an increase in femur length and a decrease in many diaphyseal measures. The secular increase in anterior-posterior elongation of the femur midshaft is due to a non-significant change in the anterior posterior dimension of the midshaft accompanied by a significant decrease in the transverse dimension.

The results of this study indicate that a complex relationship exists between the diaphysis, total femur structure, and mechanical loading. The current findings suggest the mediolateral dimension of the femoral midshaft may be more indicative of the level of mechanical loading than the anterior-posterior dimension. Additionally, anterior-posterior elongation of the femur midshaft in the current study appears to be related to a decrease loading and not to the type of loading (like running), as previously postulated. The non-significant change in the anterior posterior midshaft is attributed to the critical significance of this dimension to overall femur morphology, including length, curvature, and anatomical significance as a muscle attachment site. The decrease in many femur measures is attributed to a reduction in mechanical loads as a consequence of the changing lifestyle initiated in the early 20th century.

Sex differences were also examined, with statistically significant differences apparent for all size variables. Sex differences were not noted for the subtrochanteric or midshaft shape indices in Whites, or for the subtrochanteric region in Blacks. Blacks were significant for sex differences in the shape of the midshaft at p = 0.0029. Difference between Black and White females and Black and White males were also examined for each of the femur variables. Results of the allometric analysis suggest that total subperiosteal area is increasing more slowly in relation to bone length in all groups. Finally, the interaction between age and the diaphyseal variables was explored. The results support some age related expansion of the diaphysis with no change in midshaft shape, supporting the hypothesis that bone shape is determined during growth and development and young adulthood while the skeleton is engaged in modeling. Different patterns of age- related periosteal expansion were noted for males and females.

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