Regional variations in cortical modeling in the femoral mid-shaft: Sex andage differences

Modern lifestyle changes may result in site-specific alterations in the ske leton. Our aim was to determine sex and age differences in regional geometr y at the mid-femur. Complete cross sections from 113 individuals aged 20-97 years from a modern Australian population were obtained. A further subsamp le of 24, in whom the precise orientation of specimens was known, was subse quently collected. Microradiographs were made of 100-mu m sections and the bone was analyzed using image processing software (Optimas, Media Cyberneti cs). The periosteal boundary was extracted automatically and the centroid o f the periosteal outline was calculated. Fourier shape analysis was used to delineate the endocortical surface. Radial and cortical widths in each qua drant were determined. The posterior was identified by the linea aspera, an d the medial and lateral were indistinguishable and therefore grouped toget her. For analysis, the entire sample was divided into three groups: young ( 20-40 years), middle (41-60 years), and old (61+ years). Raw and height-nor malized values were analyzed with SPSS using t-tests, analysis of variance, and Tukey's honestly significant difference (HSD) tests. The results show that with age the femoral mid-shaft in both sexes becomes larger and more c ircular, with a slight shift towards the anterior. Apposition is least on t he posterior and resorption greatest on the anterior, the latter being part icularly evident in postmenopausal females. The greatest sex differences ar e seen in the middle years, lessening again in the old. We conclude that di fferential circumferential modeling in response to functional and postural changes occurs in both sexes with age. (C) 2000 Wiley-Liss, Inc.