Comparison of DXA hip structural analysis with volumetric QCT.

Hip structural analysis (HSA) estimates geometrical and mechanical properties from hip dual-energy X-ray absorptiometry (DXA) images and is widely used in osteoporosis trials. This study compares HSA to volumetric quantitative computed tomography (QCT) measurements in the same population. A total of 121 women (mean age 58 yr, mean body mass index 27 kg/m2) participated. Each woman received a volumetric QCT scan and DXA scan of the left hip. QCT scans were analyzed with in-house software that directly computed geometric and mechanical parameters at the neck and trochanteric regions. DXA HSA was performed with an implementation by GE/Lunar. Pair-wise linear regression of HSA variables was conducted by method to site matched QCT variables for bone density, cross-sectional area, and cross-sectional moment of inertia (CSMI) of the femur neck. HSA correlated well with QCT (r2=0.67 for neck bone mineral density [BMD] and 0.5 for CSMI) and standard DXA at the neck (r2=0.82 for BMD). HSA and volumetric QCT compared favorably, which supports the validity of a projective technique such as DXA to derive geometrical properties of the proximal hip.