Association Between DXA And HR-pQCT Measurements Of BMD In Active, Recruit-aged Men And Women

Abstract

Dual-energy X-ray absorptiometry (DXA) areal bone mineral density (aBMD) measurements are routinely employed to assess fracture risk despite the limitations of a two-dimensional, estimated projection of bone volume. Conversely, high-resolution peripheral quantitative computed tomography (HR-pQCT) provides three-dimensional volumetric BMD (vBMD) measurements of total, trabecular, and cortical bone, offering better characterization of fracture risk. It remains unclear whether regional aBMD accurately reflects vBMD of specific bone compartments in the distal tibia, a common injury site for military personnel. PURPOSE: To determine if lower limb aBMD correlates with distal total (Tt), trabecular (Tb) and cortical (Ct) vBMD in healthy, recruit-aged men and women. METHODS: Seventy-six recreationally active men (n = 43;26.4 ± 0.8 yrs.), and women (n = 33;26.2 ± 4.7 yrs.), free of any musculoskeletal conditions that could influence BMD, completed two HR-pQCT (XtremeCT; Scanco Medical) and one total body DXA (Lunar iDXA; GE Healthcare) scans. Total body DXA and non-dominant tibial HR-pQCT scans at the metaphysis (4% site) and diaphysis (30% site) were obtained. Lower leg aBMD was assessed in DXA scans with custom region of interest (ROI) analysis between the ultradistal tibia and the tibial plateau. Associations between variables were analyzed with Pearson’s correlation coefficient (r2); alpha was set at p < 0.05. RESULTS: aBMD positively correlated with Tt vBMD at the 4% site for men (r2 = 0.42; p < 0.001) and women (r2 = 0.17; p = 0.016) but only in men at the 30% site (r2 = 0.16; p = 0.008). aBMD positively correlated with Tb vBMD at the 4% site for men (r2 = 0.35; p < 0.001) and women (r2 = 0.20; p = 0.010), but not at the 30% site for either sex. aBMD was not correlated with Ct vBMD at the 4% site for either sex but was positively correlated with Ct vBMD at the 30% site in men (r2 = 0.12; p = 0.032). CONCLUSIONS: There is poor to moderate association between lower limb aBMD and tibial vBMD at both sites, with greater association in men than in women. aBMD is unlikely to provide a suitable assessment of distal tibial bone health. aBMD and tibial vBMD should, therefore, not be used interchangeably to examine the bone response to interventions or for the prediction of fracture risk. Supported by UK Ministry of Defence (WGCC 5.5.6-Task 0107).