Parameters of Bone Strength in New Recruits

Abstract

Bone size and mineralization have been shown to contribute to stress fracture, a bone overuse injury. Characterization of these parameters of bone strength in new recruits may help to understand observed gender differences in the incidence of stress fracture. PURPOSE: To identify gender differences in density and geometry of the tibia, a frequent site of stress fracture. METHODS: Fifty-eight Israeli Defense Forces (IDF) basic training soldiers (11 men, 47 women; age 18–21 yr) volunteered to participate in this study. Peripheral quantitative computed tomography (pQCT) scans were taken at 4% and 38% proximal to the tibial endplate prior to entering basic combat training. Measures included bone mineral content (BMC), bone area, bone mineral density (BMD), and a cortical polar strength strain index (SSIp). A one-way ANOVA was used to analyze gender differences in trabecular parameters at the 4% site and cortical parameters at the 38% site. RESULTS: As seen in the table below, women had lower BMC and smaller area at the 4% and 38% sites compared to the men, and a decreased SSIp at the 38% site. Women had higher cortical BMD than men, while trabecular BMD did not differ between genders.TableDISCUSSION: Gender adequately differentiated bone mineral and geometric properties in our sample. The comparatively increased density at the 38% site in women in the context of the decreased area at the 4% and 38% sites suggests that midshaft cortical density increases to compensate for a more slender bone. Gender differences in size, rather than BMD, may provide an explanation for the higher incidence of stress fracture seen in women.