Bone geometry and lower extremity bone stress injuries in male runners

Bone stress injuries (BSI) are common among distance runners and research investigations examining risk factors for BSI among men are limited. Therefore, investigations are needed to determine if men with a history of BSI have skeletal properties that may heighten BSI incidence.

To analyze differences in bone density, bone geometry, and estimates of bone strength in male runners with and without a BSI history.

Cross-sectional.

We recruited 36 male distance runners ages 18-41 for this study. We used peripheral quantitative computed tomography (pQCT) to assess volumetric bone mineral density (vBMD, mg/mm³), bone geometry (total and cortical bone area, mm²), tibia robustness (total area/tibia length, mm) and estimates of bone strength (section modulus and polar strength-strain index, mm³) at 5 tibial sites.

After adjusting for age, the BSI group had more slender tibias (9%), lower stress strain indices (-16%), lower section moduli (-17%) and smaller total cross-sectional (-11%) and cortical areas (-12%) at the 66% site of the tibia compared with controls (P < 0.05 for all). Similar differences were found at all other measurement sites. After adjusting for body size, differences in bone outcomes remained significant at the 66% site.

These results indicate that men with a history of BSI have lower estimated bending strength compared to controls because of narrower tibias. However, differences are largely attenuated in the distal ½ of the tibia after adjusting for body size. Thus, smaller tibia size, particularly at the mid-diaphysis, may be an important indicator for BSI incidence.