Sexual dimorphism of femoral neck cross-sectional bone geometry in athletes and non-athletes: a hip structural analysis study.

The characterisation of bone geometry in male and female athletes may increase our understanding of how physical loading may enhance bone strength in both sexes. This study investigated sexual dimorphism in hip geometry of athletes and age- and sex-matched non-athletes. Dual energy X-ray absorptiometry of the left proximal femur was performed in 62 male (n = 31; 30.2 ± 4.6 years) and female (n = 31; 27.9 ± 5.2 years) competitive endurance runners, and 36 male (n = 18; 28.7 ± 5.8 years) and female (n = 18; 29.1 ± 5.3 years) non-athletes. The hip structural analysis programme determined areal bone mineral density (aBMD), bone area (BA), hip axis length, cross-sectional area (CSA), and cross-sectional moment of inertia (CSMI) of the femoral neck. Strength indices were derived from the femoral strength index (FSI) (Yoshikawa et al., J Bone Miner Res 9:1053-1064, 1994). Despite similar size-adjusted aBMD, sexual dimorphism was apparent for BA, CSA and CSMI, with superior values in men compared to women (P < 0.01). FSI was greater in male and female athletes than non-athletes (P < 0.01). From all groups, results in male athletes inferred greatest resistance to axial (CSA) and bending loads (FSI). Estimates of bone strength (FSI) were greater in female athletes than male and female non-athletes, supporting the osteogenic value of regular loading of the hip.