EFFECTS OF ANTEVERSION ON FEMORAL BONE-MINERAL DENSITY AND GEOMETRY MEASURED BY DUAL-ENERGY X-RAY ABSORPTIOMETRY - A CADAVER STUDY

The effect of femoral neck anteversion on bone mineral density (BMD) a nd geometry as measured by dual energy X-ray absorptiometry (DXA) was assessed using 61 right proximal femora from 36 male and 28 female cad avers, The anteversion angle was measured on computed tomography (CT) images, and DXA measurements were made both in the neutral position (i .e., at 0 degrees anteversion, femoral neck axis parallel to the table ) and in the simulated anteverted position (i.e., femoral shaft axis p arallel to the table, greater and lesser trochanters in contact with t he table, and femoral neck free), The mean anteversion angle measured by CT was 19.3 degrees (range 6 degrees-38 degrees). Anteversion was a ssociated with a significant elevation in femoral neck BR;ID of +2.8% (range -5.3%-+9.8%) (p < 0.05), and the femoral neck BMD increased wit h increasing anteversion (p < 0.01), Trochanteric BMD was less affecte d by anteversion, with an average increase of only 0.2% (range -5%-5.9 %) (p = n.s.) in the anteverted position, but there was a significant positive association between the change in trochanteric BMD and the an teversion angle (p < 0.01). Anteversion produced a mean reduction of - 2.4% (range -7.6%-+4.3%)) (p < 0.001) in apparent femoral neck aids le ngth, while femoral neck width remained generally unaffected, These da ta confirm that femoral BMD as measured by DXA is affected by femoral anteversion with a lesser magnitude than previously reported, The use of trochanteric BMD may minimize the influence of anteversion. While t he mean changes in BMD and neck axis length attributable to anteversio n are modest, the considerable interindividual variability in the magn itude of the effects demonstrates that other factors, such as, the com plex geometry of femoral neck modifies the effect of anteversion on BM D measurements, The error in BMD introduced femoral anteversion may re present a significant confounding influence in cross-sectional and lon gitudinal studies, Careful repositioning of the foot and leg is essent ial in monitoring changes in BMD longitudinally, Knowledge of the effe cts of femoral anteversion may assist in understanding the relation of femoral BMD and neck axis length to hip fracture. (C) 1997 by Elsevie r Science Inc. All rights reserved.