Age-related trends in hip geometry in Sri Lankan women: a cross-sectional study

Indices of hip geometry are known to be predictive of hip fractures while sex and ethnic differences in hip geometry have been previously demonstrated. Age-related trends in hip geometry among Asians, however, have not been studied sufficiently. A total of 280 healthy, perimenopausal women, aged between 32 and 97 years, were selected from the Community Study Area of the Faculty of Medicine, Galle, Sri Lanka. Hip DXA images were analyzed further to calculate the hip axis length, neck-shaft angle, and femoral neck width at the narrowest point of the femoral neck. Standard formulae were used to calculate cross-sectional area, cross-sectional moment of inertia, and section modulus in the femoral neck region. Mean (SD) age, weight, height, femoral neck bone mineral density (BMD), hip axis length, neck-shaft angle, neck width, cross-sectional area, and cross-sectional moment of inertia of the study sample were 56.8 (13.0) years, 47.8 (10.1) kg, 1.48 (0.06) m, 0.704 (0.147) g/cm(2), 90.6 (5.6) mm, 123.2 (5.7) degrees, 2.99 (0.24) cm, 2.00 (0.42) cm(2), and 1.62 (0.47) cm(4), respectively. Height and weight of subjects had positive correlations with most of the indices of hip geometry. Femoral neck BMD, cross-sectional area and section modulus showed a rapid reduction during the postmenopausal period. With advancing age, there was a marginal but statistically nonsignificant expansion of the neck width, increase in the hip axis length, and narrowing of the neck-shaft angle. In conclusion, this study demonstrated a gradual loss of BMD in postmenopausal age, accompanied by thinning of the cortical shell and deterioration of the resistance to bending in the femoral neck of this group of healthy women. The clinical relevance of the marginal changes seen in other indices such as neck-shaft angle, hip axis length, and neck width is not known.