Dual-energy x-ray absorptiometry measurement and accuracy of bone mineral after unilateral total hip arthroplasty

The standard technique for monitoring bone mineral in hip arthroplasty has been dual-energy x-ray absorptiometry (DEXA). The accuracy of DEXA in the cortical bone adjacent to femoral components has not been established. This study evaluated bone mineral in the cortical bone adjacent to the femoral component comparing DEXA and ashing. Seven pairs of human femora from postmortem donors with unilateral hip implants were examined. Twenty-eight ashed core specimens from both the medial and lateral sides were taken. Cortical bone loss was seen to be greater in the proximal and medial regions of the implanted femora. Dual-energy x-ray absorptiometry failed to show an acceptable level of accuracy compared with ash data (r = 0.56; P =.002). it did show relative patterns of bone loss. Bone loss was consistent with implant-induced stress shielding.