Femoral bone density in young male adults with stress fractures

Femoral bone mineral density (BMD) was measured by dualphoton absorptiometry in 41 young military recruits who had one or several stress fractures, during their physical training program. These fractures involved the following locations: Femur (neck: n = 10, diaphysis: n = 2), calcaneus (n = 10), tibia (n = 8), fibula (n = 3), metatarsus (n = 8). The stress fracture group generally had a lower bone density than that of a control group, consisting of 48 young military recruits matched for age, height and weight. However, the BMD was significantly lower (-10%) in patients with femoral and calcaneal locations, but it did not differ for other locations. To determine the possible effect of this intense physical activity on bone mineral mass, bone mass was measured again in 35 subjects from the control group at the end of their training. The BMD remained stable or increased in 28 subjects, but decreased significantly (greater than 2%) in 7 subjects, demonstrating the individual variability in the adaptation of bone to this stress. Our results suggest that lowered bone mass could be a factor that encourages the development of stress fractures (femoral and calcaneal) in young subjects submitted to intense physical activity to which they are not accustomed.