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

Abstract

CONTEXT Lower 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. OBJECTIVE We 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 SETTING Cross-sectional study; Clinical Research Center SUBJECTS 34 female endurance athletes involved in weight-bearing sports (17 AA, 17 EA) and 16 non-athletes (14-21y) of comparable age, maturity and BMI OUTCOME MEASURES We used HR-pQCT images to assess cortical microarchitecture and FEA to estimate bone stiffness and failure load. RESULTS Cortical 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%. CONCLUSION AA 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.

Hip Structural Analysis in Adolescent and Young Adult Oligoamenorrheic and Eumenorrheic Athletes and Nonathletes

“…These data sug- (3). Of interest, menarchal age was not a significant predictor of any HSA measure in our study, in contrast to studies of microarchitecture of the distal tibia and distal radius in athletes, which found that increasing menarchal age was associated with greater impairment of bone density and structure (2,3). Girls involved in Ն16 hours/wk of moderate to vigorous activity were noted to have a higher risk of stress fractures in one study, suggesting that greater volume or intensity of exercise is deleterious to bone health, despite the effects of mechanical loading (19).…”

“…In studies using HRpQCT, we have reported that eumenorrheic endurance athletes have higher estimates of bone strength, namely stiffness and failure load, at the distal tibia than nonathletes, whereas amenorrheic athletes do not differ from nonathletes (3). These data and reports of a higher prevalence of fractures in amenorrheic compared with eumenorrheic athletes (20,21) suggest that benefits of mechanical loading on bone through exercise may be attenuated in the amenorrheic (hypogonadal) state.…”

“…Using high-resolution peripheral quantitative computed tomography (HRpQCT), we have shown that at the distal tibia, oligoamenorrheic athletes (AAs) have lower trabecular number and greater trabecular separation than eumenorrheic athletes (EAs) and nonathletes (2). We have also shown, using finite element analysis, that estimates of bone strength such as stiffness and failure load are higher at the distal tibia in EAs than in nonathletes, whereas these measures do not differ in AAs versus nonathletes (3). Body mass index (BMI), lean mass, height, bone age, and menarchal age are important predictors of trabecular and cortical parameters.…”

Current and past menstrual status is an important determinant of femoral neck geometry in exercising women

“…Historically, the majority of studies focusing on the effects of menstrual cycle disturbances have naturally focused on BMD, the bone health variable clinically used to diagnose osteoporosis. However, with technological advances in bone health imaging, such as HSA, and greater accessibility to other modes of bone imaging, such as QCT, there has been an additional focus on bone geometry among female athletes with menstrual disturbances [5][6][7]12,27,50]. These advancements in the field of women's bone health are important due to the major influence that bone geometry has on overall bone health.…”

Skeletal muscle and pediatric bone development

“…Skeletal muscle mass and size are consistent and positive predictors of cortical bone geometry, predominantly because of their role in promoting bone mineral deposition toward the periosteum [14,[30][31][32][33] …”