Assessing Agreement of Lateral Leg Muscle and Bone Composition Using Dual X-ray Absorptiometry

Background: Recently, a lateral-view dual X-ray absorptiometry (DXA)scanning method for measuring leg total, lean, and fat masses demonstrated accuracy vs the standard whole-body frontal DXA scanning view on the GE Lunar iDXA. The current study examined the lateral scanning method's agreement using a Hologic Horizon A DXA scanner. Methodology: Thirty healthy college-age participants (16 female; X̅_age = 21.5 ± 1.7 yr)received 3 DXA scans (1 whole-body, 2 lateral leg scans)to quantify leg composition in the frontal and lateral plane. To mark regions of interest for postscan analysis, metallic markers were placed at 60% of the length above and below each leg's lateral epicondyle. Using lateral subject positioning, leg composition was measured with participants lying on their right and left sides. Paired t tests examined the lateral DXA scanning method's agreement when quantifying total, fat, and lean masses, bone mineral content, and bone mineral density compared to measurements of equal area in the whole-body frontal scanning view. Results: Comparisons of frontal and lateral view DXA scan measurements for right leg total mass (7.12 ± 0.91kg vs 6.39 ± 0.85kg), fat mass (1.70 ± 0.44kg vs 1.36 ± 0.33kg), lean mass (5.14 ± 1.05kg vs 4.77 ± 0.92kg), bone mineral content (0.28 ± 0.06kg vs 0.23 ± 0.05kg), and bone mineral density (1.39 ± 0.14g/cm²vs 1.36 ± 0.15g/cm²), respectively, were significantly different (p < 0.001–0.028). Similarly, comparisons of frontal and lateral left leg total mass (7.12 ± 0.97kg vs 6.38 ± 0.92kg), fat mass (1.70 ± 0.44kg vs 1.39 ± 0.36kg), lean mass (5.15 ± 1.12kg vs 4.76 ± 0.97kg), bone mineral content (0.28 ± 0.06kg vs 0.24 ± 0.06kg), and bone mineral density (1.39 ± 0.15g/cm²vs 1.36 ± 0.17g/cm²), respectively, were significantly different (p < 0.001–0.046). Conclusion: Unlike a previous study in which agreement of lateral vs frontal leg composition measurements of equal area was reported utilizing the GE Lunar iDXA, agreement was not observed using the Hologic Horizon A DXA scanner. Therefore, lateral view assessment may not be reliably performed on DXA scanner models produced by different manufacturers.