Examination of the effects of obesity on weight-bearing extremities: CT scan analysis and comparison of modern European American and African American male samples
Arias, Sara Melissa
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Analysis of body mass markers on the skeletal frame allows for the identification of obesity markers in unknown skeletons and brings into focus the debilitating effects of obesity on the skeletal frame. Drawing from Agostini and Ross' (2011) and Moore's (2009) analyses of obese body mass indicators, this study compared lower extremity CT scans of mesomorphic and obese male patients of African-American and European-American ancestry from the Boston Medical Center. Using the software OsiriX, CT cross-sectional area slices yielded measurements of cortical thickness, an indicator of axial compression, and linear dimensions of the cortical shape, an indicator of bending strength, not possible with external osteometric measurements. Measurements from the pelvis, knee region, and tibia were included as they contribute to the biomechanics of walking (Spyropoulos et al., 1991; Dalstra and Huiskes, 1995) and respond to extra loads from excess adipose tissue (Moore, 2009). Multivariate analysis on a sample of 17 European-Americans and 21 African-Americans measured the effects of BMI and ancestry on the lower extremity. The main effects of BMI correlated with a greater external medial-lateral width of the femoral diaphysis (p less than 0.05) in obese individuals of both ancestries compared to the mesomorphic groups. The cross sectional anterior-posterior elongation of the mid-diaphyses of the femur (p less than 0.05) also correlated with BMI, resulting in a greater average mean in the obese groups, which may be attributed to either active lifestyle patterns in this particular obese population or sample size limitations. Main effects associated with ancestry were in the femoral neck, cross sectional area at 35% femoral diaphyseal length, medial-lateral cross sectional width at 80% diaphyseal length, femoral epicondylar width, tibial epiphyseal width, and ischial thickness. The results reflect the difference in gait velocity, knee flexion, and cortical bone build-up between the ancestral groups, with the obese gait exacerbating the difference in their femoral shape. Future studies would benefit from a larger sample size and analyzing the biomechanical stress of the obese gait in African-Americans, following Spyropoulos et al. (1991) methods, to isolate the weaker regions of the skeletal frame in both ancestries and address them in weight intervention programs.
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