DIFFERENCES IN HIP AXIS AND FEMORAL-NECK LENGTH IN PREMENOPAUSAL WOMEN OF POLYNESIAN, ASIAN AND EUROPEAN ORIGIN

There are substantial inter-racial differences in hip fracture inciden ce. Studies in several different ethnic groups have suggested that dif ferences in the length of the femoral neck may contribute to these. Th e present study assesses femoral neck and hip axis lengths in three et hnic groups in which it has not been documented previously (Chinese, I ndians and Polynesians) and compares these values with those in Europe ans. Lengths were measured from dual-energy X-ray absorptiometry scans of the proximal femur in normal premenopausal women (n = 225). The Po lynesian (1.65 m) and European (1.64 m) women were significantly talle r than the two Asian groups (mean height in each, 1.58 m). There were also differences in mean body weight, the Polynesians being the heavie st (76 kg) and the Chinese the lightest (53 kg). Femoral neck lengths were (mean +/- SD) Chinese 61.5 +/- 4.4 mm, Indian 61.5 +/- 5.1 mm, Po lynesian 68.2 +/- 4.3 mm and Europeans 66.0 +/- 4.8 mm. Hip axis lengt hs were Chinese 98.0 +/- 5.6 mm, Indian 94.5 +/- 5.2 mm, Polynesian 10 6.3 +/- 5.3 mm and European 102.3 +/- 5.3 mm. Each of the other groups were significantly different from the Europeans for both variables an d, in general, this remained so after height adjustment. These data su ggest that shorter femoral necks are common to the major Asian racial groups. However, in contrast to all other ethnic groups studied, Polyn esians have longer femoral necks than Europeans and their low incidenc e of hip fracture is not explicable, therefore, in terms of their femo ral neck length. This suggests that either higher bone density or othe r more subtle differences in proximal femoral geometry must account fo r the low hip fracture incidence in Polynesians.