Abduction Position at Hip Influences Femoral Neck (FN) BMD?

Case Description:

This is a routine screening DXA in 70 y.o. male. The first image shows excessive abduction at L hip. The FN BMD is 0.617 gm/cm2.  The patient was recalled and proper positioning is seen in the second image, with a similar degree of internal rotation and same hip ROI size. The FN BMD is 0.568 gm/cm2.

No LSC available for the FN at the facility, absolute difference is -0.031 gm/cm2 or -5.0%. ISCD maximum permissible is +/- 6.9 %

The degree of  hip rotation is well known to influence FN BMD, data are scarce regarding the influence of “verticality” on FN BMD measures, but existing data on GE/Lunar scanners appear to show no significant impact (see refs).

The hip global regions of interest are incorrect.  The bottom of the hip global region of interest should be 10 pixels below the lesser trochanter.  In addition, in both images, the upper aspect of the femoral head is not completely outlined.

Credit:

Christopher R. Shuhart, MD, MHA, CCD
Swedish Bone Health and Osteoporosis
Seattle, WA

References:

Byram H. Ozer, Diane Krueger, Neil Binkley,
Slight Abduction/Adduction Deviations in Femur Positioning for Dual-Energy X-Ray Absorptiometry are Inconsequential,
Journal of Clinical Densitometry,
Volume 13, Issue 1,
2010,
Pages 10-17,

Fergus McKiernan, William Washington,
Effect of Subtle Positioning Flaws on Measured Bone Mineral Density of the Hip,
Journal of Clinical Densitometry,
Volume 8, Issue 3,
2005,
Pages 330-334,