Compromised Tibial Microarchitecture Is Also Present In Healthy Men With Subclinically Low Bone Mass

Developing a resilient skeleton early in life, by maximizing accrual of bone mass and optimizing structure and strength, is an important strategy for mitigating future fracture risk. PURPOSE: Compare bone mineral density (BMD), microarchitecture and estimated strength in healthy, physically active adult males with lower than expected vs. normal bone mass. METHODS: Dual-energy X-ray absorptiometry (DXA) of the total body, lumbar spine, and unilateral hip was performed in healthy, physically active, young adult males to determine areal BMD (aBMD) and calculate Z-scores. High-resolution peripheral quantitative computed tomography (HR-pQCT) assessed volumetric BMD (vBMD), microarchitecture and estimated strength at the distal tibial metaphysis (4% of limb length) and diaphysis (30%). Men with lower than expected aBMD (LOW; Z-score < -1 any site; n = 20; 26 ± 5 yr; 24.5 ± 3.5 kg/m2) were compared to those with higher than average aBMD (CON; Z-score > 1 any site and none < -1 at any site; n = 18; 23 ± 5 yr; 23.8 ± 2.6 kg/m2) based on low BMD guidelines by the American College of Sports Medicine. ANCOVAs, adjusting for age, analyzed group differences; mean ± SD, α = 0.05. RESULTS: Z-scores and aBMD were lower in LOW vs. CON at total body, lumbar spine, total hip, and femoral neck (p < 0.001). At the tibial metaphysis, LOW had lower total area (1134.7 ± 152.4 vs. 1245.9 ± 117.4 mm2, p = 0.020), cortical area (90.8 ± 20.6 vs. 112.3 ± 15.1 mm2, p = 0.004), trabecular number (1.7 ± 0.2 vs. 1.9 ± 0.2 1/mm, p = 0.004), total vBMD (247.3 ± 31.5 vs. 275.8 ± 15.8 mgHA/cm3, p = 0.002), trabecular vBMD (202.4 ± 22.8 vs. 227.7 ± 17.8 mgHA/cm3, p < 0.001) and failure load (11.3 ± 2.2 vs. 14.8 ± 2.0 kN, p < 0.001), and higher trabecular separation (0.55 ± 0.08 vs. 0.49 ± 0.06 mm, p = 0.002) than CON. At the tibial diaphysis, LOW had lower total area (384.8 ± 43.5 vs. 423.4 ± 55.1 mm2, p = 0.024), cortical area (273.4 ± 28.8 vs. 323.1 ± 33.1 mm2, p < 0.001), cortical thickness (5.7 ± 0.8 vs. 6.6 ± 0.5 mm, p < 0.001), and failure load (16.5 ± 1.9 vs. 19.7 ± 1.9 kN, p < 0.001) than CON. CONCLUSION: Healthy, physically active, young adult men presenting with subclinically low aBMD demonstrate compromised bone microarchitecture and estimated strength. Osteogenic lifestyle factors, e.g., adequate nutrition and weight-bearing physical activity, should be encouraged early in life to optimize bone health. Supported by: DoD W81XWH2110542