Cortical microstructure and estimated bone strength in young amenorrheic athletes, eumenorrheic athletes and non-athletes

ContextLower bone density in young amenorrheic athletes (AA) compared to eumenorrheic athletes (EA) and non-athletes may increase fracture risk during a critical time of bone accrual. Finite element analysis (FEA) is a unique tool to estimate bone strength in vivo, and the contribution of cortical microstructure to bone strength in young athletes is not well understood.ObjectiveWe hypothesized that FEA-estimated stiffness and failure load are impaired in AA at the distal radius and tibia compared to EA and non-athletes despite weight-bearing exercise.Design and settingCross-sectional study; Clinical Research CenterSubjects34 female endurance athletes involved in weight-bearing sports (17 AA, 17 EA) and 16 non-athletes (14–21 years) of comparable age, maturity and BMIOutcome measuresWe used HR-pQCT images to assess cortical microarchitecture and FEA to estimate bone stiffness and failure load.ResultsCortical perimeter, porosity and trabecular area at the weight-bearing tibia were greater in both groups of athletes than non-athletes, whereas the ratio (%) of cortical to total area was lowest in AA. Despite greater cortical porosity in EA, estimated tibial stiffness and failure load was higher than in non-athletes. However, this advantage was lost in AA. At the non-weight-bearing radius, failure load and stiffness were lower in AA than non-athletes. After controlling for lean mass and menarchal age, athletic status accounted for 5–9% of the variability in stiffness and failure load, menarchal age for 8–23%, and lean mass for 12–37%.ConclusionAA have lower FEA-estimated bone strength at the distal radius than non-athletes, and lose the advantage of weight-bearing exercise seen in EA at the distal tibia.

► Finite element analysis allows estimation of bone stiffness and failure load.
► Bone strength estimates were assessed in young, weight-bearing endurance athletes.
► Amenorrheic athletes (AA) have lower bone strength at the radius than non-athletes.
► Eumenorrheic athletes have higher bone strength at the tibia than non-athletes.
► In AA, loss of strength at the radius is attenuated at the weight-bearing tibia.